Nutrition for Health, Fitness & Sport [9 ed.] 0073375551, 9780073375557

This textbook provides the reader with thorough coverage of the role nutrition plays in enhancing one's health, fit

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Nutrition for Health, Fitness & Sport [9 ed.]
 0073375551, 9780073375557

Table of contents :
Tittle
Contents
1 Introduction to Nutrition for Health, Fitness, and Sports Performance
Health-Related Fitness: Exercise and Nutrition
Exercise and Health-Related Fitness
What is health-related fitness?
What are the basic principles of exercise training?
What is the role of exercise in health promotion?
How does exercise enhance health?
Do most of us exercise enough?
How much physical activity is enough for health benefits?
What are some general guidelines for exercising properly for someone who wants to be more physically active?
Can too much exercise be harmful to my health?
Nutrition and Health-Related Fitness
What is nutrition?
What is the role of nutrition in health promotion?
Do we eat right?
What are some general guidelines for healthy eating?
Am I eating right?
Are there additional health benefits when both exercise and diet habits are improved?
Sports-Related Fitness: Exercise and Nutrition
What is sports-related fitness?
What is sports nutrition?
Is sports nutrition a profession?
Are athletes today receiving adequate nutrition?
How does nutrition affect athletic performance?
What should athletes eat to help optimize sport performance?
Ergogenic Aids and Sports Performance: Beyond Training
What is an ergogenic aid?
Why are nutritional ergogenics so popular?
Are nutritional ergogenics effective?
Are nutritional ergogenics safe?
Are nutritional ergogenics legal?
Nutritional Quackery in Health and Sports
What is nutritional quackery?
Why is nutritional quackery so prevalent in athletics?
How do I recognize nutritional quackery in health and sports?
Where can I get sound nutritional information to combat quackery in health and sports?
Research and Prudent Recommendations
What types of research provide valid information?
Why do we often hear contradictory advice about the effects of nutrition on health or physical performance?
What is the basis for the dietary recommendations presented in this book?
How does all this relate to me?
2 Healthful Nutrition for Fitness and Sport: The Consumer Athlete
Essential Nutrients and Recommended Nutrient Intakes
What are essential nutrients?
What are nonessential nutrients?
How are recommended dietary intakes determined?
The Balanced Diet and Nutrient Density
What is a balanced diet?
What foods should I eat to obtain the nutrients I need?
What is the MyPyramid Food Guide?
What is the Food Exchange System?
What is the key-nutrient concept for obtaining a balanced diet?
What is the concept of nutrient density?
Will use of MyPyramid Food Guide or the Food Exchange System guarantee me optimal nutrition?
Healthful Dietary Guidelines
What is the basis underlying the development of healthful dietary guidelines?
What are the recommended dietary guidelines for reducing the risk of chronic disease?
Vegetarianism
What types of foods does a vegetarian eat?
What are some of the nutritional concerns with a vegetarian diet?
Is a vegetarian diet more healthful than a nonvegetarian diet?
How can I become a vegetarian?
Will a vegetarian diet affect physical performance potential?
Consumer Nutrition—Food Labels and Health Claims
What nutrition information do food labels provide?
How can I use this information to select a healthier diet?
What health claims are allowed on food products?
What are functional foods?
Consumer Nutrition—Dietary Supplements and Health
What are dietary supplements?
Will dietary supplements improve my health?
Can dietary supplements harm my health?
Consumer Nutrition—Food Quality and Safety
Is current food biotechnology effective and safe?
Do pesticides in food present significant health risks?
Are organic foods safer and healthier choices?
Does commercial food processing affect food quality and safety?
Does home food processing affect food quality and safety?
What is food poisoning?
Are food additives safe?
Why do some people experience adverse reactions to some foods?
Healthful Nutrition: Recommendations for Better Physical Performance
What should I eat during training?
When and what should I eat just prior to competition?
What should I eat during competition?
What should I eat after competition?
Should athletes use commercial sports foods?
How can I eat more nutritiously while traveling for competition?
How do gender and age influence nutritional recommendations for enhanced physical performance?
3 Human Energy
Measures of Energy
What is energy?
How do we measure work,physical activity, and energy expenditure?
What is the most commonly used measure of energy?
Human Energy Systems
How is energy stored in the body?
What are the human energy systems?
What nutrients are necessary for the operation of the human energy systems?
Human Energy Metabolism during Rest
What is metabolism?
What factors account for the amount of energy expended during rest?
What effect does eating a meal have on the metabolic rate?
How can I estimate my daily resting energy expenditure (REE)?
What genetic factors affect my REE?
How does body composition affect my REE?
What environmental factors may also influence the REE?
What energy sources are used during rest?
Human Energy Metabolism during Exercise
How do my muscles influence the amount of energy I can produce during exercise?
What effect does muscular exercise have on the metabolic rate?
How is exercise intensity measured?
How is the energy expenditure of exercise metabolism expressed?
How can I tell what my metabolic rate is during exercise?
How can I determine the energy cost of exercise?
What are the best types of activities to increase energy expenditure?
Does exercise affect my resting energy expenditure (REE)?
Does exercise affect the thermic effect of food (TEF)?
How much energy do I need to consume daily?
Human Energy Systems and Fatigue during Exercise
What energy systems are used during exercise?
What energy sources are used during exercise?
What is fatigue?
What causes acute fatigue in athletes?
How can I delay the onset of fatigue?
How is nutrition related to fatigue processes?
4 Carbohydrates: The Main Energy Food
Dietary Carbohydrates
What are the different types of dietary carbohydrates?
What are some common foods high in carbohydrate content?
How much carbohydrate do we need in the diet?
Metabolism and Function
How are dietary carbohydrates digested and absorbed and what are some implications for sports performance?
What happens to the carbohydrate after it is absorbed into the body?
What is the metabolic fate of blood glucose?
How much total energy do we store as carbohydrate?
Can the human body make carbohydrates from protein and fat?
What are the major functions of carbohydrate in human nutrition?
Carbohydrates for Exercise
In what types of activities does the body rely heavily on carbohydrate as an energy source?
Why is carbohydrate an important energy source for exercise?
What effect does endurance training have on carbohydrate metabolism?
How is hypoglycemia related to the development of fatigue?
How is lactic acid production related to fatigue?
How is low muscle glycogen related to the development of fatigue?
How are low endogenous carbohydrate levels related to the central fatigue hypothesis?
Will eating carbohydrate immediately before or during an event improve physical performance?
When, how much, and in what form should carbohydrates be consumed before or during exercise?
What is the importance of carbohydrate replenishment after prolonged exercise?
Will a high-carbohydrate diet enhance my daily exercise training?
Carbohydrate Loading
What is carbohydrate, or glycogen, loading?
What type of athlete would benefit from carbohydrate loading?
How do you carbohydrate load?
Will carbohydrate loading increase muscle glycogen concentration?
How do I know if my muscles have increased their glycogen stores?
Will carbohydrate loading improve exercise performance?
Are there any possible detrimental effects relative to carbohydrate loading?
Carbohydrates: Ergogenic Aspects
Do the metabolic by-products of carbohydrate exert an ergogenic effect?
Dietary Carbohydrates: Health Implications
How do refined sugars and starches affect my health?
Are artificial sweeteners safe?
Why are complex carbohydrates thought to be beneficial to my health?
Why should I eat foods rich in fiber?
Do some carbohydrate foods cause food intolerance?
Does exercise exert any beneficial health effects related to carbohydrate metabolism?
5 Fat: An Important Energy Source during Exercise
Dietary Fats
What are the different types of dietary fats?
What are triglycerides?
What are some common foods high in fat content?
How do I calculate the percentage of fat Calories in a food?
What are fat substitutes?
What is cholesterol?
What foods contain cholesterol?
What are phospholipids?
What foods contain phospholipids?
How much fat and cholesterol do we need in the diet?
Metabolism and Function
How does dietary fat get into the body?
What happens to the lipid once it gets in the body?
What are the different types of lipoproteins?
Can the body make fat from protein and carbohydrate?
What are the major functions of the body lipids?
How much total energy is stored in the body as fat?
Fats and Exercise
Are fats used as an energy source during exercise?
Does gender or age influence the use of fats as an energy source during exercise?
What effect does exercise training have on fat metabolism during exercise?
Fats: Ergogenic Aspects
What is fat loading?
Will fasting help improve my performance?
Can the use of medium-chain triglycerides improve endurance performance?
Is the glycerol portion of triglycerides an effective ergogenic aid?
Are phospholipid dietary supplements effective ergogenic aids?
Why are omega-3 fatty acids suggested to be ergogenic, and do they work?
Can carnitine supplements enhance fat metabolism and physical performance?
Can hydroxycitrate (HCA) enhance endurance performance?
Can conjugated linoleic acid (CLA) enhance exercise performance?
What’s the bottom line regarding the ergogenic effects of fat-burning diets or strategies?
Dietary Fats and Cholesterol: Health Implications
How does cardiovascular disease develop?
How do the different forms of serum lipids affect the development of atherosclerosis?
Can I reduce my serum lipid levels and possibly reverse atherosclerosis?
What should I eat to modify my serum lipid profile favorably?
Can exercise training also elicit favorable changes in the serum lipid profile?
6 Protein: The Tissue Builder
Dietary Protein
What is protein?
Is there a difference between animal and plant protein?
What are some common foods that are good sources of protein?
How much dietary protein do I need?
How much of the essential amino acids do I need?
What are some dietary guidelines to ensure adequate protein intake?
Metabolism and Function
What happens to protein in the human body?
Can protein be formed from carbohydrates and fats?
What are the major functions of protein in human nutrition?
Proteins and Exercise
Are proteins used for energy during exercise?
Does exercise increase protein losses in other ways?
What happens to protein metabolism during recovery after exercise?
What effect does exercise training have upon protein metabolism?
Do individuals in strenuous physical training, including the developing adolescent athlete, need more protein in the diet?
What are some general recommendations relative to dietary protein intake for athletes?
Protein: Ergogenic Aspects
What types of special protein supplements are marketed to physically active individuals?
Do high-protein diets or protein supplements increase muscle mass and strength in resistance-trained individuals?
Do high-protein diets or protein supplements improve aerobic endurance performance in endurance-trained individuals?
Are amino acid, amine, and related nitrogen-containing supplements effective ergogenic aids?
Dietary Protein: Health Implications
Does a deficiency of dietary protein pose any health risks?
Does excessive protein intake pose any health risks?
Does the consumption of individual amino acids pose any health risks?
7 Vitamins: The Organic Regulators
Basic Facts
What are vitamins and how do they work?
What vitamins are essential to human nutrition?
In general, how do deficiencies or excesses of vitamins influence health or physical performance?
Fat-Soluble Vitamins
Vitamin A (retinol)
Vitamin D (cholecalciferol)
Vitamin E (alpha-tocopherol)
Vitamin K (menadione)
Water-Soluble Vitamins
Thiamin (vitamin B1)
Riboflavin (vitamin B2)
Niacin
Vitamin B6 (pyridoxine)
Vitamin B12 (cobalamin)
Folate (folic acid)
Pantothenic acid
Biotin
Choline
Vitamin B complex
Vitamin C (ascorbic acid)
Vitamin Supplements: Ergogenic Aspects
Should physically active individuals take vitamin supplements?
Can the antioxidant vitamins prevent fatigue or muscle damage during training?
How effective are the special vitamin supplements marketed for athletes?
What’s the bottom line regarding vitamin supplements for athletes?
Vitamin Supplements: Health Aspects
Can I obtain the vitamins I need through my diet?
Why are vitamin supplements often recommended?
Why do individuals take vitamin megadoses?
Do foods rich in vitamins, particularly antioxidant vitamins, help deter chronic disease?
Do vitamin supplements help deter disease?
How much of a vitamin supplement is too much?
If I want to take a vitamin-mineral supplement, what are some prudent guidelines?
8 Minerals: The Inorganic Regulators
Basic Facts
What are minerals, and what is their importance to humans?
What minerals are essential to human nutrition?
In general, how do deficiencies or excesses of minerals influence health or physical performance?
Macrominerals
Calcium (Ca)
Phosphorus (P)
Magnesium (Mg)
Trace Minerals
Iron (Fe)
Copper (Cu)
Zinc (Zn)
Chromium (Cr)
Selenium (Se)
Boron (B)
Vanadium (V)
Other trace minerals
Mineral Supplements: Exercise and Health
Does exercise increase my need for minerals?
Can I obtain the minerals I need through my diet?
Are mineral megadoses or some nonessential minerals harmful?
Should physically active individuals take mineral supplements?
9 Water, Electrolytes, and Temperature Regulation
Water
How much water do you need per day?
What else is in the water we drink?
Where is water stored in the body?
How is body water regulated?
How do I know if I am adequately hydrated?
What are the major functions of water in the body?
Can drinking more water or fluids confer any health benefits?
Electrolytes
What is an electrolyte?
Sodium (Na)
Chloride (Cl)
Potassium (K)
Regulation of Body Temperature
What is the normal body temperature?
What are the major factors that influence body temperature?
How does the body regulate its own temperature?
What environmental conditions may predispose an athletic individual to hyperthermia?
How does exercise affect body temperature?
How is body heat dissipated during exercise?
Exercise Performance in the Heat: Effect of Environmental Temperature and Fluid and Electrolyte Losses
How does environmental heat affect physical performance?
How do dehydration and hypohydration affect physical performance?
How fast may an individual dehydrate while exercising?
How can I determine my sweat rate?
What is the composition of sweat?
Is excessive sweating likely to create an electrolyte deficiency?
Exercise in the Heat: Fluid, Carbohydrate, and Electrolyte Replacement
Which is most important to replace during exercise in the heat— water, carbohydrate, or electrolytes?
What are some sound guidelines for maintaining water (fluid) balance during exercise?
What factors influence gastric emptying and intestinal absorption?
How should carbohydrate be replaced during exercise in the heat?
How should electrolytes be replaced during or following exercise?
What is hyponatremia and what causes it during exercise?
Are salt tablets or potassium supplements necessary?
What are some prudent guidelines relative to fluid replacement while exercising under warm or hot environmental conditions?
Ergogenic Aspects
Does oxygen water enhance exercise performance?
Do pre-cooling techniques help reduce body temperature and enhance performance during exercise in the heat?
Does sodium loading enhance endurance performance?
Does glycerol supplementation enhance endurance performance during exercise under warm environmental conditions?
Health Aspects: Heat Illness
Should I exercise in the heat?
What are the potential health hazards of excessive heat stress imposed on the body?
What are the symptoms and treatment of heat injuries?
Do some individuals have problems tolerating exercise in the heat?
How can I reduce the hazards associated with exercise in a hot environment?
How can I become acclimatized to exercise in the heat?
Health Aspects: High Blood Pressure
What is high blood pressure, or hypertension?
How is high blood pressure treated?
What dietary modifications may help reduce or prevent hypertension?
Can exercise help prevent or treat hypertension?
10 Body Weight and Composition for Health and Sport
Body Weight and Composition
What is the ideal body weight?
What are the values and limitations of the BMI?
What is the composition of the body?
What techniques are available to measure body composition and how accurate are they?
What problems may be associated with rigid adherence to body fat percentages in sport?
How much should I weigh or how much body fat should I have?
Regulation of Body Weight and Composition
How does the human body normally control its own weight?
How is fat deposited in the body?
What is the cause of obesity?
Can the set point change?
Why is prevention of childhood obesity so important?
Weight Gain, Obesity, and Health
What health problems are associated with overweight and obesity?
How does the location of fat in the body affect health?
Does being obese increase health risks in youth?
Does losing excess body fat reduce health risks and improve health status?
Does being physically fit negate the adverse health effects associated with being overweight?
Excessive Weight Loss and Health
What health problems are associated with improper weight-loss programs and practices?
What are the major eating disorders?
What eating problems are associated with sports?
Body Composition and Physical Performance
What effect does excess body weight have on physical performance?
Does excessive weight loss impair physical performance?
11 Weight Maintenance and Loss through Proper Nutrition and Exercise
Basics of Weight Control
How many Calories are in a pound of body fat?
Is the caloric concept of weight control valid?
How many Calories do I need per day to maintain my body weight?
How much weight can I lose safely per week?
How can I determine the amount of body weight I need to lose?
Behavior Modification
What is behavior modification?
How do I apply behavior-modification techniques in my weight-control program?
Dietary Modifications
How can I determine the number of Calories needed in a diet to lose weight?
How can I predict my body-weight loss through dieting alone?
Why does a person usually lose the most weight during the first week on a reducing diet?
Why does it become more difficult to lose weight after several weeks or months on a diet program?
What are the major characteristics of a sound diet for weight control?
Is it a good idea to count Calories when attempting to lose body weight?
What is the Food Exchange System?
How can I determine the number of Calories I eat daily?
What are some general guidelines I can use in the selection and preparation of foods to promote weight loss or maintain a healthy body weight?
How can I plan a nutritionally balanced, low-Calorie diet?
Are very-low-Calorie diets effective and desirable as a means to lose body weight?
Is it harmful to overeat occasionally?
Exercise Programs
What role does exercise play in weight reduction and weight maintenance?
Does exercise affect the appetite?
Does exercise affect the set point?
What types of exercise programs are most effective for losing body fat?
If I am inactive now, should I see a physician before I initiate an exercise program?
What other precautions would be advisable before I start an exercise program?
What is the general design of exercise programs for weight reduction?
What is the stimulus period of exercise?
What is an appropriate level of exercise intensity?
How can I determine the exercise intensity needed to achieve my target HR range?
How can I design my own exercise program?
How much exercise is needed to lose weight?
From what parts of the body does the weight loss occur during an exercise weight-reduction program?
Should I do low-intensity exercises to burn more fat?
Is spot reducing effective?
Is it possible to exercise and still not lose body weight?
What about the five or six pounds a person may lose during an hour of exercise?
Comprehensive Weight-Control Programs
Which is more effective for weight control—dieting or exercise?
If I want to lose weight through a national or local weight-loss program, what should I look for?
What type of weight-reduction program is advisable for young athletes?
What is the importance of prevention in a weight-control program?
12 Weight Gaining through Proper Nutrition and Exercise
Basic Considerations
Why are some individuals underweight?
What steps should I take if I want to gain weight?
Nutritional Considerations
How many Calories are needed to form one pound of muscle?
How can I determine the amount of Calories I need daily to gain one pound per week?
Is protein supplementation necessary during a weight-gaining program?
Are dietary supplements necessary during a weight-gaining program?
What is an example of a balanced diet that will help me gain weight?
Would such a high-Calorie diet be ill advised for some individuals?
Exercise Considerations
What are the primary purposes of resistance training?
What are the basic principles of resistance training?
What is an example of a resistance-training program that may help me to gain body weight as lean muscle mass?
Are there any safety concerns associated with resistance training?
How does the body gain weight with a resistance-training program?
Is any one type of resistance-training program or equipment more effective than others for gaining body weight?
If exercise burns Calories,won’t I lose weight on a resistance-training program?
Are there any contraindications to resistance training?
Are there any health benefits associated with resistance training?
Can I combine aerobic and resistance-training exercises into one program?
13 Food Drugs and Related Supplements
Alcohol: Ergogenic Effects and Health Implications
What is the alcohol and nutrient content of typical alcoholic beverages?
What is the metabolic fate of alcohol in the body?
Is alcohol an effective ergogenic aid?
What effect can drinking alcohol have upon my health?
Caffeine: Ergogenic Effects and Health Implications
What is caffeine and in what food products is it found?
What effects does caffeine have on the body that may benefit exercise performance?
Does caffeine enhance exercise performance?
Does drinking coffee, tea, or other caffeinated beverages provide any health benefits or pose any significant health risks?
Ephedra (ephedrine): Ergogenic Effects and Health Implications
What is ephedra (ephedrine)?
Does ephedrine enhance exercise performance?
Do dietary supplements containing ephedra pose any health risks?
Sodium Bicarbonate: Ergogenic Effects, Safety, and Legality
What is sodium bicarbonate?
Does sodium bicarbonate, or soda loading, enhance physical performance?
Is sodium bicarbonate supplementation safe and legal?
Anabolic Hormones and Dietary Supplements: Ergogenic Effects and Health Implications
Is human growth hormone (HGH) an effective, safe, and legal ergogenic aid?
Are testosterone and anabolic/androgenic steroids (AAS) effective, safe, and legal ergogenic aids?
Are anabolic prohormone dietary supplements effective, safe, and legal ergogenic aids?
Ginseng, Herbals, and Exercise and Sports Performance
Do ginseng or ciwujia enhance exercise or sport performance?
What herbals are effective ergogenic aids?
Sports Supplements: Efficacy, Safety, and Permissibility
What sports supplements are considered to be effective, safe, and permissible?
APPENDIX A Units of Measurement: English System– Metric System Equivalents
APPENDIX B Approximate Caloric Expenditure per Minute for Various Physical Activities
APPENDIX C Self-Test on Drinking Habits and Alcoholism
APPENDIX D Determination of Healthy Body Weight
APPENDIX E Exchange Lists for Meal Planning
APPENDIX F Calories, Percent Fat, Sodium, and Dietary Fiber Cholesterol in Selected Fast-Food Restaurant Products
APPENDIX G Energy Pathways of Carbohydrate, Fat, and Protein
APPENDIX H Small Steps: 120 Small Steps to a Healthier Diet and Increased Physical Activity
APPENDIX I Sample Menu for a 2,000-Calorie Food Pattern
APPENDIX J MyPyramid for Kids
Glossary
Credits
Index

Citation preview

500* 800*

1,300* 1,300* 1,000* 1,000* 1,200* 1,200*

1,300* 1,300* 1,000* 1,000* 1,200* 1,200*

1,300* 1,000* 1,000*

1,300* 1,000* 1,000*

Children 1–3 y 4–8 y

Males 9–13 y 14–18 y 19–30 y 31–50 y 51–70 y ⬎70 y

Females 9–13 y 14–18 y 19–30 y 31–50 y 51–70 y ⬎70 y

Pregnancy ⱕ18 y 19–30 y 31–50 y

Lactation ⱕ18 y 19–30 y 31–50 y 44* 45* 45*

29* 30* 30*

21* 24* 25* 25* 20* 20*

25* 35* 35* 35* 30* 30*

11* 15*

0.2* 5.5*

Chromium (␮g/d)

1,300 1,300 1,300

1,000 1,000 1,000

700 890 900 900 900 900

700 890 900 900 900 900

340 440

200* 220*

Copper (␮g/d)

3* 3* 3*

3* 3* 3*

2* 3* 3* 3* 3* 3*

2* 3* 4* 4* 4* 4*

0.7* 1*

0.01* 0.5*

Fluoride (mg/d)

290 290 290

220 220 220

120 150 150 150 150 150

120 150 150 150 150 150

90 90

110* 130*

Iodine (␮g/d)

10 9 9

27 27 27

8 15 18 18 8 8

8 11 8 8 8 8

7 10

0.27* 11

Iron (mg/d)

360 310 320

400 350 360

240 360 310 320 320 320

240 410 400 420 420 420

80 130

30* 75*

Magnesium (mg/d)

2.6* 2.6* 2.6*

2.0* 2.0* 2.0*

1.6* 1.6* 1.8* 1.8* 1.8* 1.8*

1.9* 2.2* 2.3* 2.3* 2.3* 2.3*

1.2* 1.5*

0.003* 0.6*

Manganese (mg/d)

50 50 50

50 50 50

34 43 45 45 45 45

34 43 45 45 45 45

17 22

2* 3*

Molybdenum (␮g/d)

1,250 700 700

1,250 700 700

1,250 1,250 700 700 700 700

1,250 1,250 700 700 700 700

460 500

100* 275*

Phosphorus (mg/d)

70 70 70

60 60 60

40 55 55 55 55 55

40 55 55 55 55 55

20 30

15* 20*

Selenium (␮g/d)

13 12 12

12 11 11

8 9 8 8 8 8

8 11 11 11 11 11

3 5

2* 3

Zinc (mg/d)

Copyright 2001 by the National Academy of Sciences. All rights reserved.

SOURCES: Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride (1997); Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B-6, Folate, Vitamin B-12, Pantothenic Acid, Biotin, and Choline (1998); Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids (2000); and Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc (2001). These reports may be accessed via www.nap.edu.

NOTE: This table presents Recommended Dietary Allowances (RDAs) in bold type and Adequate Intakes (AIs) in ordinary type followed by an asterisk (*). RDAs and AIs may both be used as goals for individual intake. RDAs are set to meet the needs of almost all (97 to 98 percent) individuals in a group. For healthy breastfed infants, the AI is the mean intake. The AI for other life stage and gender groups is believed to cover needs of all individuals in the group, but lack of data or uncertainty in the data prevent being able to specify with confidence the percentage of individuals covered by this intake.

210* 270*

Calcium (mg/d)

Infants 0–6 mo 7–12 mo

Life stage group

Food and Nutrition Board, Institute of Medicine, National Academies

Dietary Reference Intakes (DRIs): Recommended Intakes for Individuals, Elements

130 130 130 130 130 130 130 130 130 130 130 130 130 130 175 175 175 210 210 210

Children 1–3 y 4–8 y

Males 9–13 y 14–18 y 19–30 y 31–50 y 51–70 y ⬎70 y

Females 9–13 y 14–18 y 19–30 y 31–50 y 51–70 y ⬎70 y

Pregnancy 14–18 y 19–30 y 31–50 y

Lactation 14–18 y 19–30 y 31–50 y 29* 29* 29*

28* 28* 28*

26* 26* 25* 25* 21* 21*

31* 38* 38* 38* 30* 30*

19* 25*

ND ND

Total fiber (g/d)

ND ND ND

ND ND ND

ND ND ND ND ND ND

ND ND ND ND ND ND

NDb ND

31* 30*

Fat (g/d)

13* 13* 13*

13* 13* 13*

10* 11* 12* 12* 11* 11*

12* 16* 17* 17* 14* 14*

7* 10*

4.4* 4.6*

Linoleic acid (g/d)

1.3* 1.3* 1.3*

1.4* 1.4* 1.4*

1.0* 1.1* 1.1* 1.1* 1.1* 1.1*

1.2* 1.6* 1.6* 1.6* 1.6* 1.6*

0.7* 0.9*

0.5* 0.5*

␣-Linolenic acid (g/d)

71 71 71

71 71 71

34 46 46 46 46 46

34 52 56 56 56 56

13 19

9.1* 13.5

Proteina (g/d)

Copyright 2002 by the National Academy of Sciences. All rights reserved.

SOURCE: Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Fatty Acids, Cholesterol, Protein, and Amino Acids (2002). This report may be accessed via www.nap.edu.

NOTE: This table presents Recommended Dietary Allowances (RDAs) in bold type and Adequate Intakes (AIs) in ordinary type followed by an asterisk (*). RDAs and AIs may both be used as goals for individual intake. RDAs are set to meet the needs of almost all (97 to 98 percent) individuals in a group. For healthy breastfed infants, the AI is the mean intake. The AI for other life stage and gender groups is believed to cover needs of all individuals in the group, but lack of data or uncertainty in the data prevent being able to specify with confidence the percentage of individuals covered by this intake. a Based on 0.8 g protein/kg body weight for reference body weight. b ND ⫽ not determinable at this time

60* 95*

Carbohydrate (g/d)

Infants 0–6 mo 7–12 mo

Life stage group

Food and Nutrition Board, Institute of Medicine, National Academies

Dietary Reference Intakes (DRIs): Recommended Intakes for Individuals, Macronutrients

Ninth Edition

NUTRITION F O R H E A LT H , F I T N E S S , & S P O R T

Melvin H. Williams Old Dominion University

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NUTRITION FOR HEALTH, FITNESS, AND SPORT, NINTH EDITION

Published by McGraw-Hill, a business unit of The McGraw-Hill Companies, Inc., 1221 Avenue of the Americas, New York, NY 10020. Copyright © 2010 by The McGraw-Hill Companies, Inc. All rights reserved. Previous editions © 2007, 2005, and 2002. No part of this publication may be reproduced or distributed in any form or by any means, or stored in a database or retrieval system, without the prior written consent of The McGraw-Hill Companies, Inc., including, but not limited to, in any network or other electronic storage or transmission, or broadcast for distance learning. Some ancillaries, including electronic and print components, may not be available to customers outside the United States. This book is printed on recycled, acid-free paper containing 10% postconsumer waste.

1 2 3 4 5 6 7 8 9 0 DOW/DOW 0 9 ISBN 978-0-07-337555-7 MHID 0-07-337555-1

Publisher: Michelle Watnick Executive Editor: Colin H. Wheatley Director of Development: Kristine Tibbetts Senior Developmental Editor: Lynne M. Meyers Marketing Manager: Heather Chase Wagner Project Manager: Melissa M. Leick Senior Production Supervisor: Kara Kudronowicz Associate Design Coordinator: Brenda A. Rolwes Cover Designer: Studio Montage, St. Louis, Missouri (USE) Cover Image: Tennis Player: © Royalty-Free CORBIS; Man Skiing, Two Women Jogging, and Healthy Living: © Getty Images; Male Swimmer: © Comstock/Jupiter Images. Lead Photo Research Coordinator: Carrie K. Burger Compositor: S4Carlisle Publishing Services Typeface: 10/12 Times Roman Printer: R. R. Donnelley Willard, OH All credits appearing on page 618 or at the end of the book are considered to be an extension of the copyright page. Library of Congress Cataloging-in-Publication Data Williams, Melvin H. Nutrition for health, fitness & sport / Melvin H. Williams. -- 9th ed. p. cm. Includes index. ISBN 978-0-07-337555-7 — ISBN 0-07-337555-1 (hard copy : alk. paper) 1. Nutrition. 2. Physical fitness. 3. Sports-Physiological aspects. I. Title. II. Title: Nutrition for health, fitness, and sport. QP141.W514 2010 613.2--dc22 2008049593

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To Jeanne, Sara, Nik, and Katy May Serena, Jeff, Daniel, and David Newsom and To My Teachers, Colleagues, and Students

Brief Contents

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CHAPTER ONE

Introduction to Nutrition for Health, Fitness, and Sports Performance 1

CHAPTER TWO

Healthful Nutrition for Fitness and Sport: The Consumer Athlete 35

CHAPTER THREE

Human Energy 85

CHAPTER FOUR

Carbohydrates: The Main Energy Food 117

CHAPTER FIVE

Fat: An Important Energy Source during Exercise 167

CHAPTER SIX

Protein: The Tissue Builder 211

CHAPTER SEVEN

Vitamins: The Organic Regulators 261

CHAPTER EIGHT

Minerals: The Inorganic Regulators 308

CHAPTER NINE

Water, Electrolytes, and Temperature Regulation 351

CHAPTER TEN

Body Weight and Composition for Health and Sport 402

CHAPTER ELEVEN

Weight Maintenance and Loss through Proper Nutrition and Exercise 441

CHAPTER TWELVE

Weight Gaining through Proper Nutrition and Exercise 498

CHAPTER THIRTEEN

Food Drugs and Related Supplements 524

Contents Preface xiv CHAPTER ONE

Introduction to Nutrition for Health, Fitness, and Sports Performance 1 Health-Related Fitness: Exercise and Nutrition 4 Exercise and Health-Related Fitness 4 What is health-related fitness? 4 What are the basic principles of exercise training? 5 What is the role of exercise in health promotion? 5 How does exercise enhance health? 6 Do most of us exercise enough? 7 How much physical activity is enough for health benefits? 7 What are some general guidelines for exercising properly for someone who wants to be more physically active? 8 Can too much exercise be harmful to my health? 10

Nutrition and Health-Related Fitness 11 What is nutrition? 11 What is the role of nutrition in health promotion? 12 Do we eat right? 12 What are some general guidelines for healthy eating? 13 Am I eating right? 14 Are there additional health benefits when both exercise and diet habits are improved? 14

Sports-Related Fitness: Exercise and Nutrition 15 What is sports-related fitness? 15 What is sports nutrition? 16 Is sports nutrition a profession? 16 Are athletes today receiving adequate nutrition? 17 How does nutrition affect athletic performance? 18 What should athletes eat to help optimize sport performance? 18

Ergogenic Aids and Sports Performance: Beyond Training 19 What is an ergogenic aid? 19 Why are nutritional ergogenics so popular? 20 Are nutritional ergogenics effective? 20 Are nutritional ergogenics safe? 20 Are nutritional ergogenics legal? 21

Nutritional Quackery in Health and Sports 21 What is nutritional quackery? 21 Why is nutritional quackery so prevalent in athletics? 22 How do I recognize nutritional quackery in health and sports? 23 Where can I get sound nutritional information to combat quackery in health and sports? 23

Research and Prudent Recommendations 25 What types of research provide valid information? 25

Why do we often hear contradictory advice about the effects of nutrition on health or physical performance? 27 What is the basis for the dietary recommendations presented in this book? 27 How does all this relate to me? 28

CHAPTER TWO

Healthful Nutrition for Fitness and Sport: The Consumer Athlete 35 Essential Nutrients and Recommended Nutrient Intakes 37 What are essential nutrients? 37 What are nonessential nutrients? 38 How are recommended dietary intakes determined? 38

The Balanced Diet and Nutrient Density 40 What is a balanced diet? 40 What foods should I eat to obtain the nutrients I need? 40 What is the MyPyramid Food Guide? 41 What is the Food Exchange System? 43 What is the key-nutrient concept for obtaining a balanced diet? 43 What is the concept of nutrient density? 45 Will use of MyPyramid Food Guide or the Food Exchange System guarantee me optimal nutrition? 46

Healthful Dietary Guidelines 47 What is the basis underlying the development of healthful dietary guidelines? 47 What are the recommended dietary guidelines for reducing the risk of chronic disease? 48

Vegetarianism 53 What types of foods does a vegetarian eat? 53 What are some of the nutritional concerns with a vegetarian diet? 55 Is a vegetarian diet more healthful than a nonvegetarian diet? 56 How can I become a vegetarian? 58 Will a vegetarian diet affect physical performance potential? 59

Consumer Nutrition—Food Labels and Health Claims 60 What nutrition information do food labels provide? 60 How can I use this information to select a healthier diet? 60 What health claims are allowed on food products? 62 What are functional foods? 64

Consumer Nutrition—Dietary Supplements and Health 66 What are dietary supplements? 66 Will dietary supplements improve my health? 66 Can dietary supplements harm my health? 67

Consumer Nutrition—Food Quality and Safety 68 Is current food biotechnology effective and safe? 68 Do pesticides in food present significant health risks? 69 Are organic foods safer and healthier choices? 70 vii

Does commercial food processing affect food quality and safety? 71 Does home food processing affect food quality and safety? 71 What is food poisoning? 72 Are food additives safe? 73 Why do some people experience adverse reactions to some foods? 74

Healthful Nutrition: Recommendations for Better Physical Performance 75 What should I eat during training? 75 When and what should I eat just prior to competition? 76 What should I eat during competition? 77 What should I eat after competition? 77 Should athletes use commercial sports foods? 77 How can I eat more nutritiously while traveling for competition? 78 How do gender and age influence nutritional recommendations for enhanced physical performance? 80

CHAPTER THREE

Human Energy 85 Measures of Energy 86 What is energy? 86 How do we measure work, physical activity, and energy expenditure? 87 What is the most commonly used measure of energy? 89

Human Energy Systems 90 How is energy stored in the body? 90 What are the human energy systems? 91 What nutrients are necessary for the operation of the human energy systems? 95

Human Energy Metabolism during Rest 96 What is metabolism? 96 What factors account for the amount of energy expended during rest? 96 What effect does eating a meal have on the metabolic rate? 96 How can I estimate my daily resting energy expenditure (REE)? 97 What genetic factors affect my REE? 97 How does body composition affect my REE? 97 What environmental factors may also influence the REE? 98 What energy sources are used during rest? 98

Human Energy Metabolism during Exercise 98 How do my muscles influence the amount of energy I can produce during exercise? 98 What effect does muscular exercise have on the metabolic rate? 99 How is exercise intensity measured? 100 How is the energy expenditure of exercise metabolism expressed? 100 How can I tell what my metabolic rate is during exercise? 101 How can I determine the energy cost of exercise? 103 What are the best types of activities to increase energy expenditure? 103 Does exercise affect my resting energy expenditure (REE)? 105 Does exercise affect the thermic effect of food (TEF)? 106 How much energy do I need to consume daily? 106

Human Energy Systems and Fatigue during Exercise 108 What energy systems are used during exercise? 108 What energy sources are used during exercise? 109 What is fatigue? 110 viii

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What causes acute fatigue in athletes? 110 How can I delay the onset of fatigue? 112 How is nutrition related to fatigue processes? 112

CHAPTER FOUR

Carbohydrates: The Main Energy Food 117 Dietary Carbohydrates 118 What are the different types of dietary carbohydrates? 118 What are some common foods high in carbohydrate content? 119 How much carbohydrate do we need in the diet? 121

Metabolism and Function 122 How are dietary carbohydrates digested and absorbed and what are some implications for sports performance? 123 What happens to the carbohydrate after it is absorbed into the body? 123 What is the metabolic fate of blood glucose? 125 How much total energy do we store as carbohydrate? 125 Can the human body make carbohydrates from protein and fat? 128 What are the major functions of carbohydrate in human nutrition? 128

Carbohydrates for Exercise 129 In what types of activities does the body rely heavily on carbohydrate as an energy source? 130 Why is carbohydrate an important energy source for exercise? 130 What effect does endurance training have on carbohydrate metabolism? 131 How is hypoglycemia related to the development of fatigue? 131 How is lactic acid production related to fatigue? 133 How is low muscle glycogen related to the development of fatigue? 134 How are low endogenous carbohydrate levels related to the central fatigue hypothesis? 135 Will eating carbohydrate immediately before or during an event improve physical performance? 135 When, how much, and in what form should carbohydrates be consumed before or during exercise? 139 What is the importance of carbohydrate replenishment after prolonged exercise? 143 Will a high-carbohydrate diet enhance my daily exercise training? 144

Carbohydrate Loading 145 What is carbohydrate, or glycogen, loading? 145 What type of athlete would benefit from carbohydrate loading? 145 How do you carbohydrate load? 146 Will carbohydrate loading increase muscle glycogen concentration? 148 How do I know if my muscles have increased their glycogen stores? 148 Will carbohydrate loading improve exercise performance? 148 Are there any possible detrimental effects relative to carbohydrate loading? 150

Carbohydrates: Ergogenic Aspects 151 Do the metabolic by-products of carbohydrate exert an ergogenic effect? 151

Dietary Carbohydrates: Health Implications 153 How do refined sugars and starches affect my health? 153 Are artificial sweeteners safe? 154

Why are complex carbohydrates thought to be beneficial to my health? 155 Why should I eat foods rich in fiber? 156 Do some carbohydrate foods cause food intolerance? 157 Does exercise exert any beneficial health effects related to carbohydrate metabolism? 158

Can I reduce my serum lipid levels and possibly reverse atherosclerosis? 194 What should I eat to modify my serum lipid profile favorably? 195 Can exercise training also elicit favorable changes in the serum lipid profile? 202

CHAPTER SIX CHAPTER FIVE

Fat: An Important Energy Source during Exercise 167 Dietary Fats 168 What are the different types of dietary fats? 168 What are triglycerides? 168 What are some common foods high in fat content? 169 How do I calculate the percentage of fat Calories in a food? 170 What are fat substitutes? 171 What is cholesterol? 172 What foods contain cholesterol? 172 What are phospholipids? 173 What foods contain phospholipids? 173 How much fat and cholesterol do we need in the diet? 173

Metabolism and Function 175 How does dietary fat get into the body? 175 What happens to the lipid once it gets in the body? 175 What are the different types of lipoproteins? 176 Can the body make fat from protein and carbohydrate? 178 What are the major functions of the body lipids? 178 How much total energy is stored in the body as fat? 179

Fats and Exercise 180 Are fats used as an energy source during exercise? 180 Does gender or age influence the use of fats as an energy source during exercise? 181 What effect does exercise training have on fat metabolism during exercise? 182

Fats: Ergogenic Aspects 183 What is fat loading? 183 Will fasting help improve my performance? 185 Can the use of medium-chain triglycerides improve endurance performance? 185 Is the glycerol portion of triglycerides an effective ergogenic aid? 186 Are phospholipid dietary supplements effective ergogenic aids? 186 Why are omega-3 fatty acids suggested to be ergogenic, and do they work? 187 Can carnitine supplements enhance fat metabolism and physical performance? 188 Can hydroxycitrate (HCA) enhance endurance performance? 189 Can conjugated linoleic acid (CLA) enhance exercise performance? 190 What’s the bottom line regarding the ergogenic effects of fat-burning diets or strategies? 190

Dietary Fats and Cholesterol: Health Implications 191 How does cardiovascular disease develop? 191 How do the different forms of serum lipids affect the development of atherosclerosis? 192

Protein: The Tissue Builder 211 Dietary Protein 212 What is protein? 212 Is there a difference between animal and plant protein? 213 What are some common foods that are good sources of protein? 214 How much dietary protein do I need? 214 How much of the essential amino acids do I need? 216 What are some dietary guidelines to ensure adequate protein intake? 216

Metabolism and Function 217 What happens to protein in the human body? 217 Can protein be formed from carbohydrates and fats? 218 What are the major functions of protein in human nutrition? 219

Proteins and Exercise 220 Are proteins used for energy during exercise? 220 Does exercise increase protein losses in other ways? 221 What happens to protein metabolism during recovery after exercise? 222 What effect does exercise training have upon protein metabolism? 222 Do individuals in strenuous physical training, including the developing adolescent athlete, need more protein in the diet? 223 What are some general recommendations relative to dietary protein intake for athletes? 224

Protein: Ergogenic Aspects 228 What types of special protein supplements are marketed to physically active individuals? 228 Do high-protein diets or protein supplements increase muscle mass and strength in resistance-trained individuals? 229 Do high-protein diets or protein supplements improve aerobic endurance performance in endurance-trained individuals? 230 Are amino acid, amine, and related nitrogen-containing supplements effective ergogenic aids? 232

Dietary Protein: Health Implications 249 Does a deficiency of dietary protein pose any health risks? 249 Does excessive protein intake pose any health risks? 250 Does the consumption of individual amino acids pose any health risks? 252

CHAPTER SEVEN

Vitamins: The Organic Regulators 261 Basic Facts 262 What are vitamins and how do they work? 262 What vitamins are essential to human nutrition? 264 In general, how do deficiencies or excesses of vitamins influence health or physical performance? 264 www.mhhe.com/williams9

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Fat-Soluble Vitamins 265 Vitamin A (retinol) 265 Vitamin D (cholecalciferol) 268 Vitamin E (alpha-tocopherol) 271 Vitamin K (menadione) 273

Water-Soluble Vitamins 274 Thiamin (vitamin B1) 274 Riboflavin (vitamin B2) 276 Niacin 276 Vitamin B6 (pyridoxine) 277 Vitamin B12 (cobalamin) 278 Folate (folic acid) 279 Pantothenic acid 281 Biotin 281 Choline 282 Vitamin B complex 283 Vitamin C (ascorbic acid) 283

Vitamin Supplements: Ergogenic Aspects 286 Should physically active individuals take vitamin supplements? 286 Can the antioxidant vitamins prevent fatigue or muscle damage during training? 286 How effective are the special vitamin supplements marketed for athletes? 288 What’s the bottom line regarding vitamin supplements for athletes? 290

Vitamin Supplements: Health Aspects 290 Can I obtain the vitamins I need through my diet? 291 Why are vitamin supplements often recommended? 291 Why do individuals take vitamin megadoses? 293 Do foods rich in vitamins, particularly antioxidant vitamins, help deter chronic disease? 293 Do vitamin supplements help deter disease? 294 How much of a vitamin supplement is too much? 297 If I want to take a vitamin-mineral supplement, what are some prudent guidelines? 297

CHAPTER EIGHT

Minerals: The Inorganic Regulators 308 Basic Facts 309 What are minerals, and what is their importance to humans? 309 What minerals are essential to human nutrition? 310 In general, how do deficiencies or excesses of minerals influence health or physical performance? 310

Macrominerals 312 Calcium (Ca) 312 Phosphorus (P) 321 Magnesium (Mg) 323

Trace Minerals 325 Iron (Fe) 325 Copper (Cu) 332 Zinc (Zn) 333 Chromium (Cr) 334 Selenium (Se) 337 Boron (B) 338 x

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Vanadium (V) 339 Other trace minerals 340

Mineral Supplements: Exercise and Health 341 Does exercise increase my need for minerals? 341 Can I obtain the minerals I need through my diet? 341 Are mineral megadoses or some nonessential minerals harmful? 342 Should physically active individuals take mineral supplements? 343

CHAPTER NINE

Water, Electrolytes, and Temperature Regulation 351 Water 352 How much water do you need per day? 352 What else is in the water we drink? 353 Where is water stored in the body? 353 How is body water regulated? 355 How do I know if I am adequately hydrated? 356 What are the major functions of water in the body? 356 Can drinking more water or fluids confer any health benefits? 356

Electrolytes 358 What is an electrolyte? 358 Sodium (Na) 358 Chloride (Cl) 359 Potassium (K) 360

Regulation of Body Temperature 361 What is the normal body temperature? 361 What are the major factors that influence body temperature? 362 How does the body regulate its own temperature? 362 What environmental conditions may predispose an athletic individual to hyperthermia? 363 How does exercise affect body temperature? 364 How is body heat dissipated during exercise? 365

Exercise Performance in the Heat: Effect of Environmental Temperature and Fluid and Electrolyte Losses 365 How does environmental heat affect physical performance? 366 How do dehydration and hypohydration affect physical performance? 366 How fast may an individual dehydrate while exercising? 368 How can I determine my sweat rate? 368 What is the composition of sweat? 369 Is excessive sweating likely to create an electrolyte deficiency? 369

Exercise in the Heat: Fluid, Carbohydrate, and Electrolyte Replacement 370 Which is most important to replace during exercise in the heat— water, carbohydrate, or electrolytes? 370 What are some sound guidelines for maintaining water (fluid) balance during exercise? 370 What factors influence gastric emptying and intestinal absorption? 372 How should carbohydrate be replaced during exercise in the heat? 373 How should electrolytes be replaced during or following exercise? 375 What is hyponatremia and what causes it during exercise? 375 Are salt tablets or potassium supplements necessary? 376 What are some prudent guidelines relative to fluid replacement while exercising under warm or hot environmental conditions? 377

Ergogenic Aspects 380 Does oxygen water enhance exercise performance? 381 Do pre-cooling techniques help reduce body temperature and enhance performance during exercise in the heat? 381 Does sodium loading enhance endurance performance? 381 Does glycerol supplementation enhance endurance performance during exercise under warm environmental conditions? 382

Health Aspects: Heat Illness 384 Should I exercise in the heat? 384 What are the potential health hazards of excessive heat stress imposed on the body? 384 What are the symptoms and treatment of heat injuries? 386 Do some individuals have problems tolerating exercise in the heat? 388 How can I reduce the hazards associated with exercise in a hot environment? 389 How can I become acclimatized to exercise in the heat? 389

Health Aspects: High Blood Pressure 390 What is high blood pressure, or hypertension? 390 How is high blood pressure treated? 392 What dietary modifications may help reduce or prevent hypertension? 392 Can exercise help prevent or treat hypertension? 395

CHAPTER TEN

Body Weight and Composition for Health and Sport 402 Body Weight and Composition 404 What is the ideal body weight? 404 What are the values and limitations of the BMI? 404 What is the composition of the body? 404 What techniques are available to measure body composition and how accurate are they? 406 What problems may be associated with rigid adherence to body fat percentages in sport? 409 How much should I weigh or how much body fat should I have? 410

Regulation of Body Weight and Composition 411 How does the human body normally control its own weight? 411 How is fat deposited in the body? 414 What is the cause of obesity? 415 Can the set point change? 418 Why is prevention of childhood obesity so important? 419

Weight Gain, Obesity, and Health 420 What health problems are associated with overweight and obesity? 420 How does the location of fat in the body affect health? 421 Does being obese increase health risks in youth? 423 Does losing excess body fat reduce health risks and improve health status? 423 Does being physically fit negate the adverse health effects associated with being overweight? 424

Excessive Weight Loss and Health 425 What health problems are associated with improper weight-loss programs and practices? 425

What are the major eating disorders? 428 What eating problems are associated with sports? 429

Body Composition and Physical Performance 432 What effect does excess body weight have on physical performance? 432 Does excessive weight loss impair physical performance? 433

CHAPTER ELEVEN

Weight Maintenance and Loss through Proper Nutrition and Exercise 441 Basics of Weight Control 443 How many Calories are in a pound of body fat? 443 Is the caloric concept of weight control valid? 443 How many Calories do I need per day to maintain my body weight? 444 How much weight can I lose safely per week? 447 How can I determine the amount of body weight I need to lose? 447

Behavior Modification 448 What is behavior modification? 448 How do I apply behavior-modification techniques in my weight-control program? 449

Dietary Modifications 452 How can I determine the number of Calories needed in a diet to lose weight? 452 How can I predict my body-weight loss through dieting alone? 453 Why does a person usually lose the most weight during the first week on a reducing diet? 453 Why does it become more difficult to lose weight after several weeks or months on a diet program? 454 What are the major characteristics of a sound diet for weight control? 454 Is it a good idea to count Calories when attempting to lose body weight? 457 What is the Food Exchange System? 458 How can I determine the number of Calories I eat daily? 458 What are some general guidelines I can use in the selection and preparation of foods to promote weight loss or maintain a healthy body weight? 461 How can I plan a nutritionally balanced, low-Calorie diet? 466 Are very-low-Calorie diets effective and desirable as a means to lose body weight? 468 Is it harmful to overeat occasionally? 469

Exercise Programs 469 What role does exercise play in weight reduction and weight maintenance? 469 Does exercise affect the appetite? 472 Does exercise affect the set point? 473 What types of exercise programs are most effective for losing body fat? 473 If I am inactive now, should I see a physician before I initiate an exercise program? 475 What other precautions would be advisable before I start an exercise program? 476 What is the general design of exercise programs for weight reduction? 476 www.mhhe.com/williams9

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What is the stimulus period of exercise? 477 What is an appropriate level of exercise intensity? 478 How can I determine the exercise intensity needed to achieve my target HR range? 480 How can I design my own exercise program? 481 How much exercise is needed to lose weight? 484 From what parts of the body does the weight loss occur during an exercise weight-reduction program? 485 Should I do low-intensity exercises to burn more fat? 485 Is spot reducing effective? 486 Is it possible to exercise and still not lose body weight? 486 What about the five or six pounds a person may lose during an hour of exercise? 487

Comprehensive Weight-Control Programs 488 Which is more effective for weight control—dieting or exercise? 488 If I want to lose weight through a national or local weight-loss program, what should I look for? 489 What type of weight-reduction program is advisable for young athletes? 490 What is the importance of prevention in a weight-control program? 490

C H A P T E R T W E LV E

Weight Gaining through Proper Nutrition and Exercise 498 Basic Considerations 500 Why are some individuals underweight? 500 What steps should I take if I want to gain weight? 500

Nutritional Considerations 501 How many Calories are needed to form one pound of muscle? 501 How can I determine the amount of Calories I need daily to gain one pound per week? 501 Is protein supplementation necessary during a weight-gaining program? 501 Are dietary supplements necessary during a weight-gaining program? 502 What is an example of a balanced diet that will help me gain weight? 503 Would such a high-Calorie diet be ill advised for some individuals? 505

Exercise Considerations 505 What are the primary purposes of resistance training? 505 What are the basic principles of resistance training? 506 What is an example of a resistance-training program that may help me to gain body weight as lean muscle mass? 508 Are there any safety concerns associated with resistance training? 510 How does the body gain weight with a resistance-training program? 515 Is any one type of resistance-training program or equipment more effective than others for gaining body weight? 516 If exercise burns Calories, won’t I lose weight on a resistance-training program? 517 Are there any contraindications to resistance training? 518 Are there any health benefits associated with resistance training? 518 Can I combine aerobic and resistance-training exercises into one program? 519

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CHAPTER THIRTEEN

Food Drugs and Related Supplements 524 Alcohol: Ergogenic Effects and Health Implications 526 What is the alcohol and nutrient content of typical alcoholic beverages? 526 What is the metabolic fate of alcohol in the body? 526 Is alcohol an effective ergogenic aid? 527 What effect can drinking alcohol have upon my health? 529

Caffeine: Ergogenic Effects and Health Implications 533 What is caffeine and in what food products is it found? 533 What effects does caffeine have on the body that may benefit exercise performance? 534 Does caffeine enhance exercise performance? 534 Does drinking coffee, tea, or other caffeinated beverages provide any health benefits or pose any significant health risks? 539

Ephedra (ephedrine): Ergogenic Effects and Health Implications 542 What is ephedra (ephedrine)? 542 Does ephedrine enhance exercise performance? 542 Do dietary supplements containing ephedra pose any health risks? 543

Sodium Bicarbonate: Ergogenic Effects, Safety, and Legality 544 What is sodium bicarbonate? 544 Does sodium bicarbonate, or soda loading, enhance physical performance? 544 Is sodium bicarbonate supplementation safe and legal? 547

Anabolic Hormones and Dietary Supplements: Ergogenic Effects and Health Implications 547 Is human growth hormone (HGH) an effective, safe, and legal ergogenic aid? 547 Are testosterone and anabolic/androgenic steroids (AAS) effective, safe, and legal ergogenic aids? 548 Are anabolic prohormone dietary supplements effective, safe, and legal ergogenic aids? 550

Ginseng, Herbals, and Exercise and Sports Performance 551 Do ginseng or ciwujia enhance exercise or sport performance? 552 What herbals are effective ergogenic aids? 553

Sports Supplements: Efficacy, Safety, and Permissibility 554 What sports supplements are considered to be effective, safe, and permissible? 554

Units of Measurement: English System– Metric System Equivalents 564 APPENDIX B Approximate Caloric Expenditure per Minute for Various Physical Activities 566 APPENDIX C Self-Test on Drinking Habits and Alcoholism 572 APPENDIX D Determination of Healthy Body Weight 574 APPENDIX E Exchange Lists for Meal Planning 579 APPENDIX A

Calories, Percent Fat, Sodium, and Dietary Fiber Cholesterol in Selected Fast-Food Restaurant Products 590 APPENDIX G Energy Pathways of Carbohydrate, Fat, and Protein 592 APPENDIX H Small Steps: 120 Small Steps to a Healthier Diet and Increased Physical Activity 596 APPENDIX F

APPENDIX I Sample Menu for a 2,000-Calorie Food Pattern 598 APPENDIX J MyPyramid for Kids 601 Glossary 602

Credits 618 Index 619

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Preface In this new millennium, our love affair with fitness and sports continues to grow. Worldwide, although physical inactivity is still very prevalent in developed nations, more of us are joining fitness facilities or initiating fitness programs, such as bicycling, running, swimming, walking, and weight training. Improvement in health and fitness is one of the major reasons that more and more people initiate an exercise program. Research has shown that adults who become physically active also may become more interested in other aspects of their lifestyles—particularly nutrition—that may affect their health in a positive way. Nutrition is the study of foods and their effects upon health, development, and performance. Although a relatively young science, nutrition research has made a significant contribution to our knowledge of essential nutrient needs. During the first part of the twentieth century, most nutrition research focused on identification of essential nutrients and amounts needed to prevent nutrientdeficiency diseases, such as scurvy from inadequate vitamin C. As nutrition science evolved, medical researchers focused on the effects of foods and their specific constituents as a means to help prevent major chronic diseases, such as heart disease and cancer, that are epidemic in developed countries. Nutriceutical is a relatively new term used to characterize the drug, or medical, effects of a particular nutrient. Recent research findings continue to indicate that our diet is one of the most important determinants of our health status. Although individual nutrients are still being evaluated for possible health benefits, research is also focusing on dietary patterns, or the totality of the diet, and resultant health benefits. Other than the health benefits of exercise and fitness, many physically active individuals also are finding the joy of athletic competition, participating in local sport events such as golf tournaments, tennis matches, triathlons, and road races. Individuals who compete athletically are always looking for a means to improve performance, be it a new piece of equipment or an improved training method. In this regard, proper nutrition may be a very important factor in improving exercise and sport performance. The United States AntiDoping Agency (USADA), in its Optimal Dietary Intake guidelines for competitive athletes, notes that now more than ever, athletes need accurate sports nutrition information, indicating that optimal nutrition is an integral part of peak performance, while an inadequate diet and lack of fuel can limit an athlete’s potential for maximum performance. Although the effect of diet on sport and exercise performance had been studied only sporadically prior to 1970, subsequently numerous sport scientists and sport nutritionists have studied the performance-enhancing effects of nutrition, such as diet xiv

composition and dietary supplements. Results of these studies have provided nutritional guidance to enhance performance in specific athletic endeavors. With the completion of the Human Genome Project, gene therapies are currently being developed for the medical treatment of various health problems. Moreover, some contend that genetic manipulations may be used to enhance sports performance. For example, gene doping to increase insulin-like growth factor, which can stimulate muscle growth, may be applied to sport. Our personal genetic code plays an important role in determining our health status and our sports abilities, and futurists speculate that one day each of us will carry our own genetic chip that will enable us to tailor food selection and exercise programs to optimize our health and sport performance. Such may be the case, but for the time being we must depend on available scientific evidence to provide us with prudent guidelines. Each year literally thousands of published studies and reviews analyze the effects of nutrition on health or exercise and sports performance. The major purpose of this text is to evaluate these scientific data and present prudent recommendations for individuals who want to modify their diet for optimal health or exercise/ sport performance.

Textbook Overview This book uses a question-answer approach, which is convenient when you may have occasional short periods to study, such as riding a bus or during a lunch break. In addition, the questions are arranged in a logical sequence, the answer to one question often leading into the question that follows. Where appropriate, crossreferencing within the text is used to expand the discussion. No deep scientific background is needed for the chemical aspects of nutrition and energy expenditure, as these have been simplified. Instructors who use this book as a course text may add details of biochemistry as they feel necessary. Chapter 1 introduces you to the general effects of exercise and nutrition on health-related and sports-related fitness, including the importance of well-controlled scientific research. Chapter 2 provides a broad overview of sound guidelines relative to nutrition for optimal health and physical performance. Chapter 3 focuses upon energy and energy pathways in the body, the key to all exercise and sport activities. Chapters 4 through 9 deal with the six basic nutrients— carbohydrate, fat, protein, vitamins, minerals, and water—with

emphasis on the health and performance implications for the physically active individual. Chapters 10 through 12 review concepts of body composition and weight control, with suggestions on how to gain or lose body weight through diet and exercise, as well as the implications of such changes for health and athletic performance. Chapter 13 covers several drug foods, such as alcohol and caffeine, and other related dietary supplements regarding their effects on health and exercise performance. Several appendixes complement the text, providing data on caloric expenditure during exercise; detailed metabolic pathways for carbohydrate, fat, and protein, methods to determine body composition; nutritional value of fast foods; and other information pertinent to physically active individuals.

New to the Ninth Edition The content throughout each chapter of the book has been updated, where merited, based on contemporary research findings regarding the effects of nutritional practices on health, fitness, and sport performance. Over 900 new references, including clinical studies, reviews, and meta-analyses, have been added to the text. Some key changes regarding specific chapters follow. Chapter 1—Introduction to Nutrition for Health, Fitness, and Sports Performance • New exercise guidelines from the joint position statement by the American College of Sports Medicine and the American Heart Association. Chapter 2—Healthful Nutrition for Fitness and Sport The Consumer Athlete • Introduction to the new MyPyramid for Kids. • New information on pesticides in foods, including the clean and dirty dozen foods to choose to minimize pesticide intake. • New question on sports food products, including sports bars, gels, and supplements. Chapter 3—Human Energy • New section on the three muscle fiber types and their role in the human energy systems during exercise. • Expanded discussion of muscular fatigue during exercise. Chapter 4—Carbohydrates: The Main Energy Food • Revised material on the glucose index and glucose load. • New discussion on how lactic acid is related to fatigue. • New table on carbohydrate intake for various athletic endeavors. • Discussion of the OmniHeart diet and healthy carbohydrates. Chapter 5—Fat: An Important Energy Source during Exercise • Expanded discussion of the Mediterranean diet, fish oils, and healthy fats in the OmniHeart diet as related to health. • New information on a recent purported ergogenic aid, phosphatidylserine. Chapter 6—Protein: The Tissue Builder • New information regarding protein/carbohydrate and whey protein supplementation and exercise performance. • New information on recent purported ergogenic aids, beta-alanine, carnosine, and arginine/citrulline. • Discussion of healthy proteins and the OmniHeart diet.

Chapter 7—Vitamins: The Organic Regulators • New information from the recent State-of-the-Science report by the National Institutes of Health on vitamin supplements and disease prevention integrated throughout the chapter. • New information on a recent purported ergogenic aid, quercetin. Chapter 8—Minerals: The Inorganic Regulators • New information from the recent State-of-the-Science report by the National Institutes of Health on mineral supplements and disease prevention integrated throughout the chapter. • New information on the ergogenic technique of live high and train low as related to iron metabolism and exercise. Chapter 9—Water, Electrolytes, and Temperature Regulation • New information from the American College of Sports Medicine position stand on fluid replacement and exercise. • Updated discussion of ergogenic aids and exercise performance, including sodium loading and body-cooling techniques. • Updated research on exertional heat illness during training and competition based on the recent American College of Sports Medicine position stand. • Discussion of the OmniHeart diet and prevention of high blood pressure. Chapter 10—Body Weight and Composition for Health and Sport • Expanded discussion of weight-loss dietary supplements. • Updated discussion of eating disorders in sport based on the recent American College of Sports Medicine position stand on the female athlete triad. Chapter 11—Weight Maintenance and Loss through Proper Nutrition and Exercise • New section on estimating daily energy expenditure through use of the MyPyramid Tracker protocol. • Updated information on the efficacy of various diet plans, such as high-fat, low-carbohydrate and low-fat, high-carbohydrate diets. • Integration of the joint American College of Sports Medicine/ American Heart Association guidelines on exercise as they may relate to weight loss and maintenance. • New guidelines from the American Academy of Pediatrics for weight loss in young athletes. Chapter 12—Weight Gaining through Proper Nutrition and Exercise • Introduction of the concept of periodization to resistance training programs. Chapter 13—Food Drugs and Related Supplements • Updated information on the potential health risks and benefits of alcohol consumption, including the new Fetal Alcohol Spectrum Disorders and challenges to research suggesting positive health benefits of moderate alcohol intake. • Updated discussion of the effects caffeine or coffee may have on health, including possible health risks and benefits. • New section presenting a list of all dietary supplements discussed in the text relative to their efficacy to enhance exercise performance, their safety, and their permissibility. Additionally, new questions, figures, or tables have been added to most chapters. Numerous Websites are highlighted throughout www.mhhe.com/williams9

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each chapter, providing appropriate addresses to obtain additional information on specific exercise and nutrition topics.

text will help the reader develop a more healthful and performanceenhancing diet. Bon appetit!

Enhanced Pedagogy

Acknowledgments

Each chapter contains several features to help enhance the learning process. Chapter Learning Objectives are presented at the beginning of each chapter, highlighting the key points and serving as a studying guide. Key Terms also are listed at the beginning of each chapter, along with the page number on which they are first highlighted and defined. Although some terms may appear in the text before they are defined, a thorough glossary includes the key terms as well as other terms warranting definition. Key Concepts provide a summary of essential information presented throughout each chapter. Students are encouraged to participate in several practical activities to help reinforce learning. Check for Yourself includes individual activities, such as checking food labels at the supermarket or measuring your body fat percentage, while the Application Exercise at the end of each chapter may involve more extensive involvement, such as a case study in weight control involving yourself or a survey of an athletic team. Students may wish to peruse all application exercises at the beginning of the course, as some may take several weeks or months to complete. The bibliographic references are of three types. Books listed provide broad coverage of the major topics in the chapter. Reviews are detailed analyses of selected topics, usually involving a synthesis and analysis of specific research studies. The specific studies listed are primary research studies. The reference lists have been completely updated for this ninth edition, with the inclusion of nearly 900 new references, and provide the scientific basis for the new concepts or additional support for those concepts previously developed. These references provide greater in-depth reading materials for the interested student. Although the content of this book is based on appropriate scientific studies, a reference-citation style is not used, that is, each statement is not referenced by a bibliographic source. However, names of authors may be used to highlight a reference source where deemed appropriate. This book is designed primarily to serve as a college text in professional preparation programs in health and physical education, exercise science, athletic training, sports medicine, and sports nutrition. It is also directed to the physically active individual interested in the nutritional aspects of physical and athletic performance. Those who may desire to initiate a physical training program may also find the nutritional information useful, as well as the guidelines for initiating a training program. This book may serve as a handy reference for coaches, trainers, and athletes. With the tremendous expansion of youth sports programs, parents may find the information valuable relative to the nutritional requirements of their active children. In summary, the major purpose of this book is to help provide a sound knowledge base relative to the role that nutrition, complemented by exercise, may play in the enhancement of both health and sport performance. Hopefully, the information provided in this

This book would not be possible without the many medical/health scientists and exercise/sport scientists throughout the world who, through their numerous studies and research, have provided the scientific data that underlie its development. I am fortunate to have developed a friendship with many of you, and I extend my sincere appreciation to all of you. The reviewers of the eight previous editions have played an integral role in the changes that are made, and this edition is no exception. I wish to extend a special note of appreciation to those who reviewed the eighth edition text and provided many valuable suggestions for improving the ninth edition manuscript.

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Preface

Ninth Edition: Dawn E. Anderson, Winona State University; Gail L. Tylec, Niagara County Community College; Linda Brady, University of Minnesota; Professor Laura J. Burger, Grossmont College; Rebecca M. Mohning, George Washington University; Stephen D. Ball, University of Missouri; Stephen K. Henderson, PhD, California State University. I would like to acknowledge deep gratitude to Lynne Meyers, Senior Developmental Editor, and Jolynn Kilburg, Roxanne Klaas, and Barb Tucker of S4Carlisle Publishing Services, for their friendly and cooperative support during the developmental and production process of this book, to Melissa Leick, Project Manager, for her assistance during the production process, and to Colin Wheatley, Publisher, for his continued support. Many thanks also to Sue Grutz for her meticulous review as a copyeditor. Thanks also to Alan Titchenal, University of Hawaii at Manoa, for his thoughtful suggestions. Finally, to the memory of Pat McSwegin for her friendship and input during the first five editions of this book. Melvin H. Williams Norfolk, Virginia

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Introduction to Nutrition for Health, Fitness, and Sports Performance

K E Y

antipromoters 12 cytokines 6 doping 21 epidemiological research 25 ergogenic aids 19 exercise 5 experimental research 25 health-related fitness 4 malnutrition 18 meta-analysis 27 nutrient 11 nutrition 11 physical activity 4 physical fitness 4

CHAPTER L E A R N I N G

O B J E C T I V E S

After studying this chapter, you should be able to: 1. Explain the role of both genetics and environment, particularly nutrition and exercise, in the determination of optimal health and successful sport performance. 2. List each of the components of health-related fitness, and then identify the potential health benefits of a physical fitness program designed to enhance both aerobic and musculoskeletal fitness. 3. Define sports-related fitness and compare it to health-related fitness, noting similarities and differences.

T E R M S

ONE

promoters 12 Prudent Healthy Diet 14 quackery 21 risk factor 3 Sedentary Death Syndrome (SeDS) 5 sports nutrition 16 sports-related fitness 15 sports supplements 20 structured physical activity 5 unstructured physical activity 5

4. List the seven principles of exercise training and explain the importance of each. 5. List the twelve guidelines underlying the Prudent Healthy Diet and discuss, in general, the importance of proper nutrition, including the role of dietary supplements, to optimal health. 6. Understand the importance of proper nutrition, including the role of dietary supplements as ergogenic aids, to sports performance. 7. Define nutritional quackery and understand the various strategies you can use to determine whether the claims of a dietary supplement are valid. 8. Explain what types of research have been used to evaluate the relationship between nutrition and health or sport performance, and evaluate the pros and cons of each type.

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Introduction There are two major focal points of this book. One is the role that nutrition, complemented by physical activity and exercise, may play in determining one’s health status. The other is the role that nutrition may play in the enhancement of fitness and sports performance. People of all ages today are physically active, and athletic competition spans all ages. Healthful nutrition is important throughout the life span of the physically active individual because suboptimal health status may impair training and competitive performance. In general, the diet that is optimal for health is also optimal for exercise and sports performance.

Nutrition, fitness, and health. The health care in most developed countries has improved tremendously over the past century. Primarily because of the dedicated work of medical researchers, we no longer fear the scourge of major acute infectious diseases such as polio, smallpox, or tuberculosis. However, we have become increasingly concerned with the treatment and prevention of chronic diseases. For example, six of the ten leading causes of death in the United States are chronic diseases, and are preventable. Given with rank in parentheses, they include: (1) diseases of the heart, (2) cancer, (3) stroke, (4) chronic lung diseases, (7) diabetes, and (10) chronic liver disease and cirrhosis. These diseases cause over 80 percent of all deaths, and this figure is destined to rise as the U.S. population becomes increasingly older, particularly during the first quarter of this century when the baby boomers of the 1940s and 1950s reach their senior years. The two primary factors that influence one’s health status are genetics and lifestyle. Most chronic diseases have a genetic basis. The Human Genome Project, which deciphered the DNA code of our 80,000 to 100,000 genes, has identified various genes associated with many chronic diseases, such as breast and prostate cancer. Genetically, females whose mothers had breast cancer are at increased risk for breast cancer, while males whose fathers had prostate cancer are at increased risk for prostate cancer. Completion of the Human Genome Project is believed to be one of the most 2

significant medical advances of all time and, according to Futterman and Lemberg, will change the field of medicine forever. Scientists now have the ability to analyze the genetic basis and molecular mechanisms underlying various diseases, and genetic health risk profiles may be developed to evaluate individual susceptibility. Although multiple genes are involved in the etiology of most chronic diseases and research regarding the application of the findings of the Human Genome Project to improve health is in its initial stages, the future looks bright. For individuals with genetic profiles predisposing them to a specific chronic disease, such as cancer, genetic therapy may provide an effective treatment or cure. Although genetic influences may play an important role in the development of chronic diseases, so too does lifestyle. The Consumers Union indicates that for most Americans heredity accounts for about 30 percent of life expectancy, while lifestyle choices and environmental factors determine the rest. However, if your close relatives lived into their 90s or died prematurely from disease, genes may play a stronger role in determining your life expectancy. According to Mokdad and others, poor diet and physical inactivity may soon overtake tobacco as the leading cause of death in the United States. Indeed, LaRosa indicated that even with the current use of powerful medicines to treat chronic health problems, diet and exercise

C H A P T E R 1 Introduction to Nutrition for Health, Fitness, and Sports Performance

are important nonpharmacological interventions not only because they may augment the effect of therapeutic drugs but, probably more importantly, may prevent chronic disease in the first place. The role of a healthful diet and exercise are intertwined with your genetic profile. What you eat and how you exercise may influence your genes. Research involving nutritional regulation of gene expression may help identify specific nutrients in the diet that may either promote or repress gene expression. For example, nutrients may be identified that repress expression of a specific cancer gene. A new journal entitled Genes & Nutrition publishes research involving the application of genetics and nutrition to health. Additionally, Shephard and Shek indicate that exercise may induce various chemical changes, such as hormone secretion, in the body that may repress gene expression for certain cancers. If your personal genetic code indicates that your genetic profile predisposes you to certain forms of cancer, and if your genetic profile indicates that you will respond favorably to specific nutritional or exercise interventions, then a preventive diet and an exercise plan may be individualized for you. Genomics represents the study of genetic material in body cells, and the terms nutrigenomics and exercisenomics have been coined to identify the study of the genetic aspects of nutrition and exercise, respectively, as related to health benefits.

Treatment of chronic diseases is very expensive. Foreseeing a financial healthcare crisis associated with an increasing prevalence of such diseases during the first half of this century, most private and public health professionals have advocated health promotion and disease prevention as the best approach to address this potential major health problem. For example, James Rippe, a renowned physician, has coined the term “lifestyle medicine” to characterize this focus on health promotion behaviors to help prevent disease. The United States Public Health Service, beginning in the 1980s, has published a series of reports designed to increase the nation’s health, the latest version entitled Healthy People 2010: National Health Promotion/Disease Prevention Objectives. Physical activity/ fitness and overweight/obesity are two major focus areas in Healthy People 2010. In these reports, lifestyle behaviors that promote health and reduce the risk of chronic diseases are basically under the control of the individual. See web address below. Over the years, scientists in the field of epidemiology have identified a number of lifestyle factors considered to be health risks; these lifestyle factors are known as risk factors. A risk factor is a health behavior that has been associated with a particular disease, such as cigarette smoking being linked to lung cancer. As we shall see, proper exercise and proper nutrition, both individually and combined, may reduce many of the risk factors associated with the development of chronic diseases. These health-

ful benefits will be addressed at appropriate points throughout the book. Nutrition, fitness, and sport. Sport is now most commonly defined as a competitive athletic activity requiring skill or physical prowess, for example, baseball, basketball, soccer, football, track, wrestling, tennis, and golf. As with health status, athletic ability and subsequent success in sport are based primarily upon two factors: natural genetic endowment and lifestyle, with lifestyle representing the appropriate type and amount of training. To be successful at high levels of competition, athletes must possess the appropriate biomechanical, physiological, and psychological genetic characteristics associated with success in a given sport. International-class athletes have such genetic traits. Enhancement of athletic performance of elite athletes via genetic therapy, or genetic engineering, is a current concern among international sport organizations such as the International Olympic Committee (IOC) and the World Anti-Doping Agency (WADA). Research by Claude Bouchard, James Skinner, and James Hagberg and their associates have identified specific genetic markers for various sport performance attributes, which Rankinen and others have assembled as a human gene map for performance and health-related fitness. Several recent genetic engineering studies with rodents have produced “endurance” and “He-Man” mice. Although some sports scientists do not believe that genetic engineering can be

www.health.gov/healthypeople Check for the full report of Healthy People 2010. www.hhs.gov/familyhistory Create your own family health history.

Ke y C o n c e p t s 䉴 Six of the ten chronic diseases in major developed countries

(heart diseases, cancer, stroke, lung diseases, diabetes, and liver diseases) may be prevented by appropriate lifestyle behaviors. 䉴 The two primary determinants of health status are genetics and lifestyle. 䉴 Two of the key health promotion objectives set by the U.S. Department of Health and Human Services in Healthy People 2010 are increased levels of physical activity and reduced levels of overweight

used to reliably produce champion athletes, others indicate it is only a matter of time and may even be in use now. To be successful at high levels of competition, athletes must also develop their genetic characteristics maximally through proper biomechanical, physiological, and psychological coaching and training. Whatever the future holds for genetic enhancement of athletic performance, specialized exercise training will still be the key to maximizing genetic potential. Training programs at the elite level have become more intense and individualized, resulting in significant performance gains, and world records continue to improve. Proper nutrition also is an important component in the total training program of the athlete. Certain nutrient deficiencies can seriously impair performance, while supplementation of other nutrients may help delay fatigue and improve performance. Over the past 50 years research has provided us with many answers about the role of nutrition in athletic performance, but unfortunately some findings have been misinterpreted or exaggerated so that a number of misconceptions still exist. The purpose of this chapter is to provide a broad overview of the role that exercise and nutrition may play relative to health, fitness, and sport, and how prudent recommendations may be determined. More detailed information regarding specific relationships of nutritional practices to health and sports performance is provided in subsequent chapters.

and obesity, one of the major purposes of a healthy diet. 䉴 Sports success is dependent upon biomechanical, physiological,

and psychological genetic characteristics specific to a given sport, but proper training, including proper nutrition, is essential to maximize one’s genetic potential.

C h e c k f o r Yo u r s e l f 䉴 Discuss with your parents any health problems they or your

grandparents may have, such as high blood pressure or diabetes, to determine whether you may be predisposed to such health problems in the future. Having such knowledge may help you develop a preventive exercise and nutrition plan early in life. Please use the Website www.hhs.gov/familyhistory to create your own family history.

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Health-Related Fitness: Exercise and Nutrition Physical fitness may be defined, in general terms, as a set of abilities individuals possess to perform specific types of physical activity. The development of physical fitness is an important concern of many professional health organizations, including the American Alliance for Health, Physical Education, Recreation, and Dance (AAHPERD), which has categorized fitness components into two different categories. In general, these two categories may be referred to as health-related fitness and sports-related fitness. Both types of fitness may be influenced by nutrition and exercise.

Exercise and Health-Related Fitness What is health-related fitness? As mentioned previously, one’s health status or wellness is influenced strongly by hereditarian predisposition and lifestyle behav-

iors, particularly appropriate physical activity and a high-quality diet. As we shall see in various sections of this book, one of the key factors in preventing the development of chronic disease is maintaining a healthful body weight. Proper physical activity may certainly improve one’s health status by helping to prevent excessive weight gain, but it may also enhance other facets of health-related fitness as well. Healthrelated fitness includes not only a healthy body weight and composition, but also cardiovascular-respiratory fitness, adequate muscular strength and muscular endurance, and sufficient flexibility (figure 1.1). Other measures used as markers of health-related fitness include blood pressure, bone strength, postural control and balance, and various indicators of lipid and carbohydrate metabolism. Several health professional organizations, such as the American College of Sports Medicine (ACSM) and American Heart Association (AHA), have indicated that various forms of physical activity may be used to enhance health. In general, physical activity involves any bodily movement caused by muscular contraction that results in the expenditure of

FIGURE 1.1 Health-

related fitness components. The most important physical fitness components related to personal health include cardiovascularrespiratory fitness, body composition, muscular strength, muscular endurance, and flexibility.

Cardiovascular-respiratory fitness

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Body composition

C H A P T E R 1 Introduction to Nutrition for Health, Fitness, and Sports Performance

Muscular strength

energy. For purposes of studying its effects on health, epidemiologists classify physical activity as either unstructured or structured. Unstructured physical activity includes many of the usual activities of daily living, such as leisurely walking and cycling, climbing stairs, dancing, gardening and yard work, various domestic and occupational activities, and games and other childhood pursuits. These unstructured activities are not normally planned to be exercise. Structured physical activity, as the name implies, is a planned program of physical activities usually designed to improve physical fitness, including health-related fitness. For the purpose of this book, we shall refer to structured physical activity as exercise, particularly some form of planned vigorous exercise, such as brisk, not leisurely, walking.

What are the basic principles of exercise training? Exercise training programs may be designed to provide specific types of health-related fitness benefits and/or enhance specific types of sports-related fitness. However, no matter what the purpose, several general principles are used in developing an appropriate exercise training program. Principle of Overload Overload is the basic principle of exercise training, and it represents the intensity, duration, and frequency of exercise. For example, a training program for cardiovascularrespiratory fitness could involve training at an intensity of 70 percent of maximal heart rate, a duration of 30 minutes, and a frequency of 5 times per week. The adaptations the body makes are based primarily on the specific exercise overload. Principle of Progression Progression is an extension of the overload principle. As your body adapts to the original overload, then the overload must be increased if further beneficial adaptations are desired. For example, you may start lifting a weight of 20 pounds, increase the weight to 25 pounds as you get stronger, and so forth. The overloads are progressively increased until the final health-related or sports-related goal is achieved. Principle of Specificity Specificity of training represents the specific adaptations the body will make in response to the type of exercise and overload. For example, running and weight lifting impose different demands, so the body adapts accordingly. Both types of exercise may provide substantial, yet different, health benefits. Exercise training programs may be designed specifically for certain health or sports-performance benefits. Principle of Recuperation Recuperation is an important principle of exercise training. Also known as the principle of recovery, it represents the time in which the body rests after exercise. This principle may apply to a specific exercise period, such as including rest periods when doing multiple sets during weight lifting. It may also apply to rest periods between exercise periods, such as a day of recovery between two long cardiovascular workouts. Principle of Individuality Individuality reflects the effect exercise training will have on each given individual, as deter-

mined by genetic characteristics. The health benefits one receives from a specific exercise training program may vary tremendously among individuals. For example, most individuals experience a reduction in blood pressure during a cardiovascular-respiratory fitness training program, whereas some may not. Principle of Reversibility Reversibility is also referred to as the principle of disuse, or use it or lose it. Without exercise, the body will begin to lose the adaptations it has made over the course of the exercise program. Individuals who suffer a lapse in their exercise program, such as a week or so, may lose only a small amount of fitness gains. However, a total relapse to a previous sedentary lifestyle can reverse all health gains. Principle of Overuse Overuse represents an excessive amount of exercise which may induce adverse, rather than beneficial, health effects. Overuse may be a problem during the beginning stages of an exercise program if one becomes overenthusiastic and exceeds her capacity, such as developing shin splints by running too far. Overuse may also occur in elite athletes who become overtrained, as discussed in chapter 3. Specific exercise programs for healthy body weight and composition, cardiovascular-respiratory fitness, and muscular strength and muscular endurance are detailed in chapters 11 and 12, and several of these principles are discussed in more detail.

What is the role of exercise in health promotion? The beneficial effect of exercise on health has been known for centuries. For example, Plato noted that “Lack of activity destroys the good condition of every human being while movement and methodical physical exercise save and preserve it.” Plato’s observation is even more relevant in contemporary society. Frank Booth, a prominent exercise scientist at the University of Missouri, has coined the term Sedentary Death Syndrome, or SeDS. Slentz and others discussed the cost of physical inactivity over time. The short-term cost of physical inactivity is metabolic deterioration and weight gain; the intermediate-term cost is an increase in disease, such as type 2 diabetes, whereas the long-term cost is increased premature mortality. Six months of continued physical inactivity in sedentary individuals significantly increased health risks by increasing body weight, waist circumference, and serum cholesterol as well as decreasing insulin sensitivity. Booth and Lees indicated that physical inactivity is cited as an actual cause of chronic disease by the U.S. Centers for Disease Control, increasing the relative risk of coronary artery disease by 45 percent, stroke by 60 percent, hypertension by 30 percent, and osteoporosis by 59 percent. The Consumers Union, reporting on the use of alternative treatments to treat various health problems, noted that exercise was one of the most effective for numerous conditions. In support of this viewpoint, the National Center for Chronic Disease Prevention and Health Promotion indicated that regular physical activity reduces people’s risk for heart attacks, certain cancers, diabetes, and high blood pressure, and may reduce their risk for stroke. It also helps to control weight; contributes to healthy bones, muscles, and joints; reduces falls among older adults; helps to relieve the pain of arthritis; reduces www.mhhe.com/williams9

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symptoms of anxiety and depression; and is associated with fewer hospitalizations, physician visits, and medications. Indeed, some physicians indicate that exercise is the best medicine of all because it offers such an array of health benefits. In this regard, the American College of Sports Medicine (ACSM) and the American Medical Association (AMA) recently launched a program entitled Exercise Is MedicineTM designed to encourage physicians and other healthcare professionals to include exercise as part of the treatment for every patient. Clinical, epidemiological, and basic research evidence clearly supports the inclusion of regular physical activity as a tool for the prevention of chronic disease and the enhancement of overall health. Recent studies and reviews, such as those led by Colcombe, Conley, Cotman, Ignarro, Irwin, Jeon, Lakka, Trojan, Warburton, and Weissgerber have documented the manifold health benefits of exercise, which are highlighted in figure 1.2. For example, Warburton and others concluded that there is irrefutable evidence of the effectiveness of regular physical activity in the primary and secondary prevention of several chronic diseases, such as cardiovascular disease, diabetes, cancer, hypertension, obesity, depression, osteoporosis, as well as premature death. These benefits may accrue to males and females of all races across all age spans. You are never too young or too old to reap some of these health benefits of exercise. Exercise may be especially helpful in preventing the premature development of chronic diseases. The term predisease recently has

been used to describe several health conditions, such as a slightly elevated blood glucose, which if little is done may lead to a full blown disease, such as diabetes. According to Hu and others, type 2 diabetes is one of the fastest growing public health problems in both developed and developing countries. They estimate that the number of people with diabetes in the world will double in coming years, from 171 million in 2000 to 366 million in 2030, and also note that cardiovascular disease accounts for more than 70 percent of total mortality among patients with type 2 diabetes. However, Hu and others also note that moderate- or high-level physical activity is an effective and safe way to prevent type 2 diabetes in all populations. In essence, physically active individuals enjoy a higher quality of life, a joie de vivre, because they are less likely to suffer the disabling symptoms often associated with chronic diseases, such as loss of ambulation experienced by some stroke victims. Physical activity may also increase the quantity of life. Franco and others found that a physically active lifestyle during adulthood, due to its effect to help prevent chronic diseases, increases life expectancy for men and women about 3.7 and 3.5 years, respectively.

How does exercise enhance health?

Bouchard has indicated that physical activity may have a direct effect on health, such as improving heart function, or it may have an indirect effect by influencing a risk factor for health, such as excess body weight. The specific mechaIncreases bone Reduces nisms whereby exercise may help to prevent the density and strength blood pressure Reverses brain deterioration development of various chronic diseases are not with aging; helps prevent, completely understood, but are involved with or delay, Alzheimer’s disease changes in gene expression that modify cell strucIncreases insulin ture and function. Physical inactivity is a major sensitivity; improves Increases cardiovascular risk factor for chronic diseases. Booth and Neufer blood glucose function and improves have noted that physical inactivity causes genes to regulation; helps prevent blood lipid profile; helps type 2 diabetes misexpress proteins, producing the metabolic dysprevent heart disease and stroke functions that result in overt clinical disease if continued long enough. On the other hand, exercise Reduces stress and may cause the expression of genes with favorable improves self-image; Aids in weight health effects. helps prevent mental loss/weight control depression Most body cells can produce and secrete small proteins known as cytokines, which are similar to hormones. Cytokines enter various body tissues, Increases flexibility Increases muscle mass, influencing gene expression that may induce adapand balance, reduces muscular strength, and tations either favorable or unfavorable to health risk of falling muscular endurance (figure 1.3). Spangenburg indicated that an increase in fat cells, which is associated with physical inactivity, may increase secretion of cytokines Improves immune Promotes a healthy that influence genes to produce fewer receptors for function pregnancy glucose in the cell membrane, thus inducing insulin resistance in adipose tissue and predisposing an individual to type 2 diabetes. On the other hand, Reduces risk of colon Improves sleep exercise may induce the formation of cytokines cancer, prostate cancer, (if activity is done in that increase the number of glucose receptors, and likely breast cancer the morning or improving insulin sensitivity and helping to reguafternoon) late blood glucose and prevent type 2 diabetes. In general, exercise-induced cytokine effects F I G U R E 1 . 2 Exercise is medicine. Here are some of the benefits of regular, on genes help to reduce many of the traditional moderate physical activity and exercise. See text for discussion. 6

C H A P T E R 1 Introduction to Nutrition for Health, Fitness, and Sports Performance

1 Hormone or Cytokine Receptor activation

3 Cellular response Gene regulatory protein Unactivated receptor protein

2 Signal transmission pathway

Altered gene expression, which changes the amounts of proteins in the cell

Nucleus

FIGURE 1.3 Exercise may induce adaptations that have favorable health effects in various body tissues. One suggested mechanism is the effect that

various hormones or cytokines, which are produced during exercise, may have on gene regulation in body cells. (1) The hormone or cytochrome binds to a cell receptor that activates a signal within the cell, (2) the signal is transmitted along a specific pathway, (3) the signal may alter gene expression and induce changes within the cell. Cell signals may also affect enzymes or other cell structures that may induce beneficial health effects.

risk factors associated with development of chronic diseases. Moreover, the Consumers Union suggested a new risk factor, local inflammation, may underlie most of the major chronic diseases, such as heart disease, cancer, diabetes, and Alzheimer’s. Exercising muscle produces an anti-inflammatory cytokine that may help cool inflammation and thus prevent certain chronic diseases. Some healthful adaptations may occur with a single bout of exercise. Thompson and others have noted that a single exercise session can acutely improve the blood lipid profile, reduce blood pressure, and improve insulin sensitivity, all beneficial responses. However, such adaptations will regress unless exercise becomes habitual. For example, Horowitz suggested that a substantial portion and perhaps most of the benefits of exercise on insulin resistance are not due to the adaptations accrued over weeks, months, or even years of endurance exercise training, but stem largely from the most recent exercise sessions. The role that exercise may play in the prevention of some chronic diseases, such as heart disease, and associated risk factors, such as obesity, are discussed throughout this book where relevant.

Do most of us exercise enough? In general, no. Surveys reveal that most adult Americans and Canadians have little or no physical activity in their daily lives. The Consumers Union notes that our addiction to physical inactivity remains as strong as ever. Keating and others noted recently that 40 to 50 percent of college students are physically inactive, and efforts by college health and physical activity professionals to increase physical activity have been unsuccessful. In a recent review of the goals of Healthy People 2010, Spain and Franks noted that most adult Americans were not getting enough physical activity. The physical activity objectives of Healthy People 2010 are to reduce the per-

centage of people who engage in no leisure-time physical activity, which is currently 40 percent; to increase the percentage who engage regularly, preferably daily, in moderate physical activity for 30 minutes per day, which is currently only 15 percent; and, to increase the proportion of adults who engage in vigorous physical activity that promotes the development of cardiovascular fitness 3 or more days per week for 20 or more minutes per occasion. Similar objectives have been set for muscular strength/endurance and flexibility. Although the percentage of children and adolescents participating in physical activity was somewhat higher compared to adults, participation was still considered to be low and thus similar physical activity objectives were established.

How much physical activity is enough for health benefits? To maximize health benefits, most health professionals recommend a comprehensive program of physical activity, including aerobic exercise, resistance training, and flexibility exercises. However, aerobic exercise is the major focus because it provides the most health benefits. For aerobic exercise, a moderate amount of physical activity, or about 30 minutes daily of moderate-intensity exercise, is the basic recommendation. Health benefits may be achieved whether the 30 minutes of exercise is done continuously, or as three 10-minute exercise snacks done throughout the day. However, some exercise scientists contend that although moderate exercise is fine, more vigorous exercise can elicit additional benefits. Kuchment indicates the mechanism underlying the enhanced benefits from more vigorous exercise is not known, but one factor may be a decrease in inflammatory www.mhhe.com/williams9

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tion, frequency) of physical activity may vary accordingly, as will type of physical activity (aerobic exercise for cardiovascular fitness; resistance exercise for muscular fitness). Moreover, the response to exercise depends on the individual. Claude Bouchard, an expert in genetics, exercise, and health, noted that due to genes, physical activity may affect some, but not others. For example, most sedentary individuals will respond favorably to an aerobic exercise training program, such as improving insulin sensitivity. On the other hand, others will not respond and have no change in insulin sensitivity. Currently there is no gene profile for responders and nonresponders to exercise training, but that may change in the future so specific exercise programs may be designed for individuals.

High

Health Benefits

Moderate

Low

What are some general guidelines for exercising properly for someone who wants to be more physically active? None 0 Sedentary (None)

Low

Moderate

High

Excessive

Weekly Level of Physical Activity

F I G U R E 1 . 4 Significant health benefits may occur at low to

moderate levels of physical activity with diminishing returns at higher levels. Excessive amounts or intensity of exercise, depending on the individual, may predispose to various types of health problems. See text for discussion.

processes. Some guidelines to moderate-intensity and more vigorousintensity exercise are presented under the next question. In general, there is a curvilinear relationship between the amount of physical activity (dose) and related health benefits (response), as depicted by the dose-response graph in figure 1.4. A sedentary lifestyle has no health benefits, but health benefits increase rapidly with low to moderate levels of weekly activity. For example, Tully and others found that sedentary individuals who began an exercise program of walking just 3 days a week achieved some, but not all, of the health benefits for those who walked 5 days a week. Beyond moderate levels of weekly physical activity, the increase in health benefits will continue to increase gradually and then plateau. Excessive exercise may actually begin to have adverse effects on some health conditions. However, as noted by Bouchard, there may be other specific doseresponse curves. Some health conditions may improve rapidly with low to moderate weekly levels of physical activity, whereas others may necessitate increased levels. As an example of the latter, Jakicic and Otto indicate that although sedentary overweight individuals may experience significant health benefits by participating in at least 30 minutes of moderate-intensity exercise daily, they may need to achieve 60 to 90 minutes per day to enhance initial weight loss and prevent weight regain. Slentz and others also note that modest increases in exercise above the minimal recommendation of 30 minutes daily lead to additional significant and widespread improvements in numerous health measures, especially in overweight individuals. Dependent on the desired health outcome, the dose (intensity, dura8

In general, moderate-intensity exercise is defined as working at 40 to 60 percent of your aerobic capacity, which we will detail in chapter 3. You should experience noticeable increases in heart rate and breathing. Your perception of the effort needed to exercise is another gauge of its intensity. Check page 481 for the 10-point scale of perceived exertion. Moderate-intensity effort is a 5 or 6 on this scale, or the feeling that the exercise feels somewhat hard. Walking at a speed of 3 miles per hour, or 20 minutes per mile, is a good guideline to moderate-intensity exercise for most individuals. Vigorous exercise usually is defined as working at 60 percent or more of your aerobic capacity, or about a 7 or 8 on the effort scale. There are large increases in heart rate and breathing so that it should be difficult to carry on a conversation using complete sentences. Jogging or running may be considered vigorous exercise for sedentary individuals. Both moderate-intensity and high-intensity exercise bouts can contribute to the accumulation of moderate amounts of weekly physical activity. Some examples of physical activity that will burn about 150 Calories in an adult male are presented in table 1.1. You may also consult appendix B to estimate Calories burned per minute for various types of physical activity and exercise. Two recent joint reports from the American College of Sports Medicine and the American Heart Association, authored by Haskell and Nelson and their colleagues, provided recommendations on exercise for adults (age 18–65) and older adults (over age 65) as a means to help prevent chronic diseases. Another report by the American Heart Association, authored by Williams and others, presents recommendations for resistance training. These exercise recommendations are above and beyond those activities of daily living, such as leisurely walking, climbing stairs, gardening, and other such activities. The following is a summarization of these recommendations. 1. Aerobic exercise. Both adults and older adults should engage in moderate-intensity aerobic (endurance) exercise for a minimum of 30 minutes daily on 5 days each week, or vigorousintensity aerobic physical activity for a minimum of 20 minutes on 3 days each week. Individuals may combine these workouts during the week, such as doing moderate-intensity exercise two days and vigorous-intensity on another 2 days. Moreover, the daily exercise time may be subdivided into multiple bouts, such as doing three 10-minute brisk walks to

C H A P T E R 1 Introduction to Nutrition for Health, Fitness, and Sports Performance

TABLE 1.1

Some examples of moderate amounts of physical activity*

Washing and waxing a car for 45–60 minutes Washing windows or floors for 45–60 minutes Playing various team sports for 45 minutes Gardening for 30–45 minutes Wheeling self in wheelchair for 30–40 minutes Walking 2 miles in 40 minutes (20 minutes/mile) Bicycling 5 miles in 30 minutes (10 miles/hour) Dancing (social) fast for 30 minutes Walking briskly 2 miles in 30 minutes (15 minutes/mile) Water aerobics for 30 minutes Swimming laps for 20 minutes Bicycling 4 miles in 15 minutes (3.75 minutes/mile) Jumping rope for 15 minutes Running 1.5 miles in 15 minutes (10 minutes/mile) Stairwalking for 15 minutes *A moderate amount of physical activity is roughly equivalent to physical activity that uses 150 Calories per day, or 1,000 Calories per week. Note that exercising at lower intensity levels requires more time (walking 2 miles in 40 minutes) than exercising at higher intensity levels (running 1.5 miles in 15 minutes). Adapted from U.S. Department of Health and Human Services. The Surgeon General’s Report on Physical Activity and Health.

total 30 minutes over the course of a day. Aerobic exercise programs are detailed in chapter 11. 2. Resistance exercise. Both adults and older adults should do exercises that maintain or increase muscular strength and endurance. The recommendation includes 8 to 10 exercises that stress the major muscle groups of the body. Individuals should perform about 8–12 repetitions of each exercise at least twice a week on nonconsecutive days. Older adults may lift lighter weights or use less resistance, but do more repetitions. Resistance exercises may include use of weights or other resistance modes, or weightbearing activities such as stair climbing, push-ups, pull-ups, and various other calisthenics that stress major muscle groups. Resistance exercise programs will be discussed in chapter 12. 3. Flexibility and balance exercise. Older adults should perform activities that help maintain or increase flexibility on at least 2 days each week for at least 10 minutes daily. Flexibility exercises are designed to maintain the range of joint motion for daily activities and physical activity. Older adults should also perform exercises that help maintain or improve balance about three times a week. Such exercises may help reduce the risk of injury from falls.

4. Individualization. Exercise programs, especially for older adults, should be individualized based on physical fitness level and health status. One key component is simply to reduce the amount of daily sedentary activity. Leisure walking may be adequate physical activity for elderly individuals with compromised health status or very low fitness levels. One of the concepts of these recommendations is more is better. For those who have the time and energy, exceeding the minimum recommended amounts of physical activity may provide additional health benefits beyond those associated with the minimum recommendations. www.americanheart.org For more information on these recommendations, click on Healthy Lifestyle, and then Exercise and Fitness.

The Department of Health and Human Services (DHHS) recently has developed comprehensive guidelines to help Americans understand the importance of physical activity and how to incorporate it into their lives. These Physical Activity Guidelines for Americans are designed to provide details supporting the recommendation for exercise in the 2005 Dietary Guidelines for Americans, popularly known as MyPyramid. The report, based on scientific studies, is based on the following criteria for different types of exercise: • Efficacy—What are the specific health benefits? • Effectiveness—Is the specified health benefit obtained by a reasonable percentage of individuals who undertake the prescribed exercise program? • What dose (intensity, duration, frequency) of exercise provides a meaningful benefit for a specific health condition? • Mechanism of action—What changes in structure or function caused by the physical activity are responsible for the specific health benefit? • Potential adverse effects—What are the health risks associated with the prescribed dose of exercise? These physical activity guidelines were published as this book went to press, and detailed information regarding their scientific basis has been presented on the DHHS Website. http://www.health.gov/paguidelines/ Presents information regarding the scientific basis underlying the development of Physical Activity Guidelines for Americans. www.acsm.org/physicalactivity/ Details both the government and ACSM/ANA exercise guidelines.

Chuck Corbin and Robert Pangrazi, exercise scientists from Arizona State University, have developed a Physical Activity Pyramid comparable to the MyPyramid food guide. A modification of their Physical Activity Pyramid, adhering to the ACSM and AHA guidelines, is presented in figure 1.5. The Physical Activity Pyramid is in accord with the guidelines to obtain adequate amounts of moderate aerobic physical activity, complemented with several days of vigorous aerobic activity and muscular strength, endurance, and flexibility training. The ACSM and AHA guidelines, the Physical Activity Pyramid, and guidelines provided by the President’s Council on Physical www.mhhe.com/williams9

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Level 5

Decrease inactivity levels; make a plan to incorporate physical activity into daily living

Watch less TV; stand rather than sit; move more

physical inactivity Level 4

Level 3

Older adults may use lighter weights or resistance but more repetitions

8–10 exercises that stress major muscle groups at least 2, preferably 3, days per week

resistance (strength) exercises: 15–30 minutes

At least 2, preferably 7, days per week for at least 10 minutes daily

Especially important for older adults

flexibility and balance exercises: 5–10 minutes Level 2 May be continuous or intermittent; three 10-minute bouts of brisk walking equals 30 minutes

aerobic exercises: 20–60 minutes

Level 1

Moderate intensity at least 5; vigorous intensity at least 3; or combination of both moderate and vigorous intensity at least 4 days per week Daily

Walk more; climb stairs low-intensity exercises: at least 30 minutes

F I G U R E 1 . 5 One version of a Physical Activity Pyramid, modeled after the My Pyramid Food Guide. See text for more specific information

regarding exercise intensity and duration for adults and older adults.

Fitness and Sports underlie the basis of designing an aerobics program for cardiovascular-respiratory fitness and proper weight control presented in chapter 11 and the principles of resistance training for muscular strength and endurance presented in chapter 12. If you are interested in starting an exercise program, you may preview those chapters or access several excellent Websites. www.smallstep.gov www.Americaonthemove.org www.fitness.gov Consult these Websites for information on fitness and starting an exercise program for most individuals. www.choosetomove.org Choose to Move is a free, 12-week physical activity program for women developed by the American Heart Association. www.Kidnetic.com www.nick.com/myworld/letsjustplay www.whatmovesu.com www.verbnow.com These Websites provide games and activities to help children become more physically active and promote overall good health.The What Moves U Website was developed jointly by the National Football League and American Heart Association, and has activity kits for use by school teachers.

10

Can too much exercise be harmful to my health? In general, the health benefits outweigh the risks of exercise. Although individuals training for sport may need to undergo prolonged, intense exercise training, such is not the case for those seeking health benefits of exercise. Given our current state of knowledge, adhering to the guidelines of the Physical Activity Pyramid, preferably at the upper time and day limits, should be safe and provide optimal health benefits associated with physical activity. The Surgeon General’s report indicates that care should be taken to avoid excessive amounts of high-intensity exercise because of increased risk of injury or other health problems. Some of these health problems include the following, which includes individuals who may have underlying health problems prior to exercising. • Orthopedic problems. Too much exercise may lead to orthopedic problems, such as stress fractures in the lower leg in those who run, particularly in those with poor biomechanics. • Impaired immune functions. Some contend that excessive exercise may impair immune functions, which may increase susceptibility to illnesses such as the common cold, or chronic fatigue as discussed in chapter 3.

C H A P T E R 1 Introduction to Nutrition for Health, Fitness, and Sports Performance

• Exercise-induced asthma. Webb and Lieberman reported that in a study of over 600 patients experiencing anaphylaxis, about 5 percent were precipitated by exercise. • Osteoporosis. When coupled with inadequate dietary energy intake, exercise that leads to excessive weight loss may contribute to the menstrual irregularities in female athletes that may contribute to loss of bone mass, or osteoporosis. This topic is discussed in chapters 8 and 10. • Heat illness and kidney failure. Exercising in the heat may cause heat stroke or other heat illnesses, as discussed in chapter 9. Clarkson noted that heat stress and dehydration from exercising in the heat, along with other factors, could cause muscle tissue damage that could result in kidney failure. • Heart attack. The ACSM indicated that although chronic exercise training helps protect the heart, an acute bout of vigorous activity could increase the risk of acute myocardial infarction and sudden cardiac death in susceptible persons, particularly those who are habitually physically inactive. It is important to emphasize that although a properly planned exercise program may be safe and confer multiple health benefits to most individuals, exercise may be hazardous to some. In an article entitled “Exercise can kill you—or save your life,” the Consumers Union notes that exercise may aggravate heart problems in susceptible individuals, leading to a heart attack, possibly a fatal one. Individuals who have any concerns about their overall health, particularly those over age 35, should have a medical screening to detect risk factors for heart disease, such as high blood pressure, before increasing their level of physical activity. Such a medical screening might include an exercise stress test during which your heart rate and blood pressure are monitored for abnormal responses. The Consumers Union notes that although exercise may be a temporary risk, it conveys lasting protection. The best protection for the heart is to exercise frequently, mainly because regular exercise helps prevent heart disease in the first place. See chapter 5, and activities in chapters 3, 11, and 12.

C h e c k f o r Yo u r s e l f As a prelude to activities presented in later chapters, make a detailed record of all your physical activities for a full day, from the moment you arise in the morning until you go to bed at night.

Nutrition and Health-Related Fitness What is nutrition? Nutrition usually is defined as the sum total of the processes involved in the intake and utilization of food substances by living organisms, including ingestion, digestion, absorption, transport, and metabolism of nutrients found in food. This definition stresses the biochemical or physiological functions of the food we eat, but the American Dietetic Association notes that nutrition may be interpreted in a broader sense and be affected by a variety of psychological, sociological, and economic factors. Although our food selection may be influenced by these latter factors, particularly economic ones in the case of many college students, the biochemical and physiological roles of many different types of food are similar. From a standpoint of health and sport performance, it is the biochemical and physiological role or function of food that is important. The primary purpose of the food we eat is to provide us with a variety of nutrients. A nutrient is a specific substance found in food that performs one or more physiological or biochemical functions in the body. There are six major classes of essential nutrients found in foods: carbohydrates, fats, proteins, vitamins, minerals, and water. However, as noted in chapter 2, food contains substances other than essential nutrients that may affect body functions. As illustrated in figure 1.6, the major nutrients perform three basic functions. First, they provide energy for human metabolism (see

Ke y C o n c e p t s 䉴 Health-related fitness includes a healthy body weight,









cardiovascular-respiratory fitness, adequate muscular strength and muscular endurance, and sufficient flexibility. Overload is the key principle underlying the adaptations to exercise that may provide a wide array of health benefits.The intensity, duration, and frequency of exercise represent the means to impose an overload on body systems that enable healthful adaptations. Physical inactivity may be dangerous to your health. Exercise, as a form of physical activity, is becoming increasingly important as a means to achieve health benefits, and even treat many chronic diseases. Physical activity need not be strenuous to achieve health benefits, but additional benefits may be gained through greater amounts of physical activity. Excessive exercise may cause serious health problems in some individuals.You should be aware of personal health issues or other factors that may be related to exercise-associated health risks.

Promote growth and development

Provide energy

Regulate metabolism

F I G U R E 1 . 6 Three major functions of nutrients in food. Many

nutrients have only one key role (e.g., glucose provides energy), whereas others have multiple roles (e.g., protein is necessary for growth and development and regulation of metabolism, and it may also be used as a source of energy).

www.mhhe.com/williams9

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chapter 3). Carbohydrates and fats are the prime sources of energy. Protein may also provide energy, but this is not its major function. Vitamins, minerals, and water are not energy sources. Second, all nutrients are used to promote growth and development by building and repairing body tissue. Protein is the major building material for muscles, other soft tissues, and enzymes, while certain minerals such as calcium and phosphorus make up the skeletal framework. Third, all nutrients are used to help regulate metabolism, or body processes. Vitamins, minerals, and proteins work closely together to maintain the diverse physiological processes of human metabolism. For example, hemoglobin in the red blood cell (RBC) is essential for the transport of oxygen to muscle tissue via the blood. Hemoglobin is a complex combination of protein and iron, but other minerals and vitamins are needed for its synthesis and for full development of the RBC. In order for our bodies to function effectively, we need more than forty specific essential nutrients, and we need these nutrients in various amounts as recommended by nutrition scientists. Dietary Reference Intakes (DRI) represent the current recommendations in the United States, and include the Recommended Dietary Allowances (RDA). These recommendations are detailed in chapter 2. Nutrient deficiencies or excesses may cause various health problems, some very serious.

What is the role of nutrition in health promotion? As noted previously, your health is dependent upon the interaction of your genes and your environment, and the food you eat is part of your personal environment. Let food be your medicine and medicine be your food. This statement has been attributed to Hippocrates for over two thousand years, and it is becoming increasingly meaningful as the preventative and therapeutic health values of food relative to the development of chronic diseases are being unraveled. Nutrients and other substances in foods may influence gene expression, some having positive and others negative effects on our health. For example, adequate amounts of certain vitamins and minerals may help prevent damage to DNA, the functional component of your genes, while excessive alcohol may lead to DNA damage. Most chronic diseases have a genetic basis; if one of your parents has had coronary heart disease or cancer, you have an increased probability of contracting that disease. Such diseases may go through three stages: initiation, promotion, and progression. Your genetic predisposition may lead to the initiation stage of the disease, but factors in your environment promote its development and eventual progression. In this regard, some nutrients are believed to be promoters that lead to the progression of the disease, while other nutrients are believed to be antipromoters that deter the initiation process from progressing to a serious health problem. What you eat plays an important role in the development or progression of a variety of chronic diseases. For example, the National Center for Chronic Disease Prevention and Health Promotion indicates that good nutrition lowers people’s risk for many chronic diseases, including heart disease, stroke, some types of cancer, diabetes, and osteoporosis (see figure 1.7). The National Cancer Institute estimates that one-third of all cancers are linked in some way to diet, ranking just behind tobacco smoking as one of the major causes of cancer. DeMarini estimates that appropriate dietary changes could 12

reduce by 50 percent the deaths due to prostate, colorectal, pancreatic, and breast cancer. As noted previously, Exercise Is Medicine. In a like manner, Food Is Medicine may also be an appropriate phrase, not only attributable to the quote from Hippocrates, but based on modern medicine as well. The types and amount of carbohydrate, fat, and protein that we eat; the amount and type of other substances such as vitamins, minerals, and phytochemicals found in our foods; the source of our food; and the method of food preparation are all factors that may influence gene expression or other metabolic functions that may affect our health status. The following are some of the proposed effects of various nutrients and appropriate energy intake that may help promote good health. • • • • • • • • • • •

Inactivate carcinogens or kill bacteria that cause cancer Increase insulin sensitivity Relax blood vessels and improve blood flow Reduce blood pressure Optimize serum lipid levels Reduce inflammation Inhibit blood clotting Enhance immune system functions Speed up digestive processes Prevent damaging oxidative processes Reduce body fat

The beneficial, or harmful, effects of specific nutrients and various dietary practices on mechanisms underlying the development of chronic diseases will be discussed as appropriate in later sections of this book.

Do we eat right? Surveys indicate that most people are aware of the role of nutrition in health and want to eat better for healthful purposes, but they do not translate their desires into appropriate action. Poor eating habits span all age groups. For example, in a recent survey of female college students by Anding and others, not one student adhered to all of the seven healthy guidelines recommended for Americans. The diets of children are also poor. Brady and others found that less than 10 percent of the children studied met dietary recommendations, and 50 percent of the diet was composed of foods least recommended, those with high amounts of sugar and fat. As a nation, young and older Americans still eat too many Calories, too much fat and saturated fat, too much sugar and other sweeteners, too much salt, too much meat and cheese, too few fruits and vegetables, and too few complex-carbohydrate and fiber-containing foods. Many are overweight and chronically dieting. Many women and children do not consume enough foods rich in calcium and iron. Analyzing recent changes in the American diet for intake of nine different food categories associated with health status, Liebman and Schardt indicated we were doing good in some areas, such as eating more fruits and vegetables, eating more chicken, and drinking less whole milk; however, we are still eating too much beef as hamburgers, eating too much cheese, drinking more soda, and consuming too much caloric sweeteners like sugar and corn syrup. To relate these nutrition findings to health in simplistic terms, most Americans eat more food (Calories) than they need, due in part to the increase in food portion sizes in recent years, and eat

C H A P T E R 1 Introduction to Nutrition for Health, Fitness, and Sports Performance

Stress Caffeine ( ↑ ) Breast cancer Alcohol ( ↑ ) Obesity ( ↑ )

Cataracts Fruits and vegetables ( ↓ ) Mouth, esophagus cancer Alcohol ( ↑ ) High blood pressure Salt ( ↑ ) Alcohol ( ↑ ) Fruits and vegetables ( ↓ ) Lung cancer Fruits and vegetables ( ↓ ) Obesity ( ↑ ) Heart disease Saturated fat ( ↑ ) Cholesterol ( ↑ ) Dietary fiber ( ↓ ) Obesity ( ↑ ) Liver disease Alcohol ( ↑ ) Diabetes Obesity ( ↑ ) Stomach cancer Cured smoked foods ( ↑ ) Colon cancer Dietary fat ( ↑ ) Dietary fiber ( ↓ ) Fruits and vegetables ( ↓ )

Prostate cancer Saturated fat ( ↑ ) Tomatoes ( ↓ ) Tomato-Based Foods ( ↓ )

§

Osteoporosis Calcium ( ↓ )

F I G U R E 1 . 7 Some possible health problems associated with poor dietary habits. An upward arrow ( ) indicates excessive intake while a

§

downward arrow ( ) indicates low intake or deficiency.

less of the food that they need more. As a rule, according to Hill, children and most adults eat what they like and leave the rest, and what they like are foods high in sugar and fat. In essence, the major nutrition goal of Healthy People 2010 is to get more Americans to change their faulty dietary habits.

What are some general guidelines for healthy eating? Because the prevention of chronic diseases is of critical importance, thousands of studies have been and are being conducted to discover the intricacies of how various nutrients may affect our health. Particular interest is focused on nutrient function within cells at the molecular level, the interactions between various nutrients, and the identification of other protective factors in certain foods. All of the answers are not in, but sufficient evidence is available to provide us with some useful, prudent guidelines for healthful eating practices. Over the past two decades, in response to the need for healthier diets, a variety of public and private health organizations analyzed the research relating diet to health and developed some basic guidelines for the general public. The details underlying these recommendations

may be found in several voluminous governmental reports, most recently the totally revamped sixth edition of Nutrition and Your Health: Dietary Guidelines for Americans, released by the U.S. Departments of Agriculture and Health and Human Services in 2005. Additionally, governmental health agencies in other countries, such as Britain, Canada, Germany, Japan, and Mexico, have developed dietary guidelines for health promotion in their countries. Recently, the American Heart Association released a set of dietary guidelines to help prevent heart disease, the American Cancer Society released a similar set to help prevent cancer, and the American Diabetes Association did likewise for prevention of diabetes. Other organizations, such as the American Dietetic Association, have also proposed dietary guidelines to promote general health. Although most of the guidelines are directed to the general population, the American Heart Association has recommended dietary guidelines specifically for women and for children and adolescents over the age of about 2 years. The dietary guidelines promoted by these government and professional health organizations have much in common, and are related to some of the diet plans we will discuss in chapters 2 and 9, notably the OmniHeart diet and the DASH diet. Each specific dietary recommendation may convey some health benefit, www.mhhe.com/williams9

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so the more of these dietary guidelines you adopt, the greater will be your overall health benefits. Although we do have considerable research to support dietary recommendations to promote health, the research is incomplete. Thus, the following dozen recommendations may be considered to be prudent, and throughout this book we will refer to these recommendations as a Prudent Healthy Diet. 1. Balance the food you eat with physical activity to maintain or improve your weight. Consume only moderate food portions. Be physically active every day. 2. Eat a nutritionally adequate diet consisting of a wide variety of nutrient-rich foods. Let the MyPyramid Food Guide guide your food choices. 3. Choose a diet moderate in total fat, but low in saturated and trans fat and cholesterol. 4. Choose a diet with plenty of fruits and vegetables, whole grain products, and legumes, which are rich in healthy carbohydrates, phytochemicals, and fiber. 5. Choose beverages and foods that moderate or reduce your intake of sugars. 6. Choose and prepare foods with less salt and sodium. 7. If you drink alcoholic beverages, do so in moderation. Pregnant women should not drink any alcohol. 8. Maintain protein intake at a moderate, yet adequate level, obtaining much of your daily protein from plant sources, complemented with smaller amounts of fish, skinless poultry, and lean meat. 9. Choose a diet adequate in calcium and iron. Individuals susceptible to tooth decay should obtain adequate fluoride. 10. Practice food safety, including proper food storage, preservation, and preparation. 11. Avoid excess intake of questionable food additives and dietary supplements. 12. Enjoy your food. Eat what you like, but balance it within your overall healthful diet. An expanded discussion of these guidelines along with practical recommendations to help you implement them is presented in chapter 2. Additional details on how each specific recommendation may affect your health status, including specific considerations for women, children, and the elderly, are presented in appropriate chapters throughout this book. For example, inadequate dietary intake of calcium may cause osteoporosis, which is covered in chapter 8.

Am I eating right? As part of this course, you may be required to document your actual food intake for several days and then conduct a computerized dietary analysis to determine your nutrient intake. Many computerized dietary analysis programs assess the quality of your diet from a health perspective, and make recommendations for improvement where necessary. For the time being, you may wish to take the brief dietary inventory in the Application Exercise at the end of this chapter to provide you with a general analysis of your current eating habits. See the following Website for in-depth, dietary (and physical activity) assessments that you may use online. 14

www.MyPyramid.gov Detailed analysis of diet and physical activity. Click on MyTracker for details.

Are there additional health benefits when both exercise and diet habits are improved? A poor diet and physical inactivity are individual major risk factors for the development of chronic diseases. Collectively, however, they may pose additional risks. In this regard, Brooks and others indicated that dietary and physical activity recommendations for healthful living are inextricably intertwined, and thus for the first time physical activity recently became part of the Dietary Recommendations for Americans. Indeed, Roberts and Barnard believe that the combination of proper exercise and a healthful diet is the solution to the epidemic of metabolic diseases—such as cardiovascular disease, diabetes, and cancer—diseases that are inundating today’s societies worldwide. For example, in its recent extensive worldwide report on the means to prevent cancer, the American Institute of Cancer Research highlighted the three most important means to prevent a wide variety of cancers, and all are related to exercise and nutrition: • Choose mostly plant foods, limit red meat, and avoid processed meat. • Be physically active every day in any way for 30 minutes or more. • Aim to be a healthy weight throughout life as much as possible. As indicated in table 1.2, which highlights risk factors for heart disease, the key lifestyle behaviors that may be effective in favorably modifying heart disease risk factors are proper nutrition and exercise. Moreover, several of the risk factors for heart disease are diseases themselves, such as diabetes, obesity, and high blood pressure, all of which may benefit from the combination of proper nutrition and exercise. The National Institute of Aging recently cited research revealing that lack of exercise and poor dietary habits, taken together, were the second-largest underlying cause (smoking was the largest) of all deaths in the United States, not counting genetic causes. Vuori indicates that in the genesis of most chronic diseases, a lack of physical activity and inadequate nutrition act synergistically and in part, additively, so both must be given high priority in plans to improve the health of the public. And many organizations have already done so. Recommendations to improve general health by the United States Department of Health and Human Services, as well as recommendations to help prevent specific chronic diseases, such as heart disease and cancer, by the American Heart Association and the American Cancer Society, include considerations of both diet and physical activity. Recent studies and reviews by Bass and others, Buettner, Khan and others, Liebman, Specker and Vukovich, and Weinstein and Sesso have shown that a healthy lifestyle incorporating proper diet and exercise would help to maximize related health benefits. The possible complementary effect of exercise and nutrition on chronic diseases will be presented in later chapters as appropriate. However, although appropriate lifestyle behaviors, such as exercise, a healthful diet, and maintaining a healthy body weight, may help prevent the development of chronic diseases, individuals with a strong genetic predisposition to various risk factors, such as high serum cholesterol levels and high blood pressure, or those who are nonresponders to exercise or diet changes, may need medication to reduce these to a level compatible with protective effects.

C H A P T E R 1 Introduction to Nutrition for Health, Fitness, and Sports Performance

TABLE 1.2

Risk factors associated with coronary heart disease Positive Health Lifestyle Modification

Risk Factors

Classification

High blood pressure

Major

Proper nutrition, aerobic exercise

High blood lipids

Major

Proper nutrition, aerobic exercise

Smoking

Major

Stop smoking

Sedentary lifestyle

Major

Aerobic exercise

ECG abnormalities

Major

Proper nutrition, aerobic exercise

Obesity

Major

Low-Calorie diet, aerobic exercise

Diabetes

Major

Proper nutrition, weight loss, aerobic exercise

Stressful lifestyle

Contributory

Stress management

Dietary intake

Contributory

Proper nutrition

Oral contraceptives

Contributory

Alternative methods of birth control

Family history

Major

Not modifiable

Gender

Contributory

Not modifiable

Race

Contributory

Not modifiable

Age

Contributory

Not modifiable

Ke y C o n c e p t s 䉴 The primary purpose of the food we eat is to provide us with









nutrients essential for the numerous physiological and biochemical functions that support life. Dietary guidelines developed by major professional health organizations are comparable, and collectively help prevent major chronic diseases such as heart disease, cancer, diabetes, high blood pressure, and obesity. Poor eating habits span all ages. The Healthy People 2010 report notes that poor nutrition is a major health problem in the United States. Basic guidelines for a Prudent Healthy Diet include maintenance of a proper body weight and consumption of a wide variety of natural foods rich in nutrients associated with health benefits. The more healthful dietary guidelines that you adopt, the greater will be your overall health benefits. Although both proper exercise and sound nutrition habits may confer health benefits separately, health benefits may be maximized when both healthy exercise and nutrition lifestyles are adopted.

C h e c k f o r Yo u r s e l f As a prelude to activities presented in later chapters, make a detailed record of everything you eat for a full day, from breakfast until your late snack at night.

Sports-Related Fitness: Exercise and Nutrition As with health, genetic endowment plays an important underlying role in the development of success in sport. For example, MacArthur and North indicate genetic factors determine 20 to 80 percent of the variation in a wide variety of traits relevant to athletic performance, such as oxygen uptake, cardiac output, and the relative proportion of fast and slow fibers in skeletal muscle. In their article entitled “What Makes a Champion?” Brutsaert and Parra also note genetically gifted athletes may be identified, but must optimize their athletic traits through appropriate training. Sport training will induce changes in gene expression that will lead to improved performance. Elite athletes are not only born, they must train properly. Moreover, Joyner and Coyle note that complex motivational and sociological factors also play important roles in who does or does not become a sport champion.

What is sports-related fitness? One of the key factors determining success in sport is the ability to maximize your genetic potential with appropriate physical and mental training to prepare both mind and body for intense competition. In this regard, athletes develop sports-related fitness, that is, fitness components such as strength, power, speed, endurance, and neuromuscular motor skills specific to their sport. The principles of exercise training introduced earlier, such as overload and specificity, are as applicable to sports-related fitness as they are to health-related fitness. However, training for sports performance is more intense, prolonged, and frequent than training for health, and training is specific to the energy demands and skills associated with each sport. We will discuss energy expenditure for sports performance in chapter 3, but here are some examples of sport events with varying rates of energy expenditure or energy needs: • Explosive, power sports —Olympic weight lifting • Very high-intensity sports —100-meter dash • High-intensity, short duration sports —5,000-meter run (3.1 miles) • Intermittent high-intensity sports —Soccer • Endurance sports —Marathon running (26.2 miles; 42.2 kilometers) • Low-endurance, precision skill sports —Golf • Weight-control and body-image sports —Bodybuilding www.mhhe.com/williams9

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FIGURE 1.8 Elite athletes are exposed to state-of-the-art physio-

logical, psychological, and biomechanical training that may mean the difference between the gold and silver medal in world-class competition.

Training of elite athletes at the United States Olympic Training Center (USOTC) focuses on three attributes: • Physical power • Mental strength • Mechanical edge Coaches and scientists work with athletes to maximize physical power production for their specific sport, to optimize mental strength in accordance with the psychological demands of the sport, and to provide the best mechanical edge by improving specific fitness and sport skills, sportswear, and sports equipment. Jay Kearney, former senior sports scientist at the USOTC, has noted that sports science and technology provide elite competitors with the tiny margins needed to win in world-class competition (figure 1.8). Athletes at all levels of competition, whether an elite international competitor, a college wrestler, a high school baseball player, a seniors age-group distance runner, or a youth league soccer player, can best improve their performance by intense training appropriate for their age, physical and mental development, and sport. For example, in a recent review as to how we should spend our time and money to improve cycling performance, Jeukendrup and Martin indicated that, of the many ways possible, training is the first and most effective means. As the saying goes, “Do the best with what you got.” However, sports and exercise scientists have investigated a number of means to improve athletic performance beyond that attributable to training, and one of the most extensively investigated areas has been the effect of nutrition.

What is sports nutrition? As noted previously, state-of-the-art physical and mental training is one of the most important factors underlying success in sports. At 16

high levels of athletic competition, athletes generally receive excellent coaching to enhance their biomechanical skills (mechanical edge), sharpen their psychological focus (mental strength), and maximize physiological functions (physical power) essential for optimal performance. Clyde Williams, a renowned sport scientist from England, notes that, in addition to specialized training, from earliest times certain foods were regarded as essential preparation for physical activity, whether this was for confrontation on the battlefields of history or competition in the stadiums of ancient Greece, the aim being to achieve greater strength, power, and stamina than one’s opponent. As we shall see, there are various dietary factors that may influence biomechanical, psychological, and physiological considerations in sport. For example, losing excess body fat will enhance biomechanical efficiency; consuming carbohydrates during exercise may maintain normal blood sugar levels and prevent psychological fatigue; and providing adequate dietary iron may ensure optimal oxygen delivery to the muscles. All these sports nutrition factors may impact favorably upon athletic performance. Sports nutrition is a relatively new area of study involving the application of nutritional principles to enhance sports performance. Louise Burke, a prominent sports nutritionist from Australia, defines sports nutrition as the application of eating strategies with several major objectives: • • • •

To promote good health To promote adaptations to training To recover quickly after each training session To perform optimally during competition

Although investigators have studied the interactions between nutrition and various forms of sport or exercise for more than a hundred years, it is only within the past few decades that extensive research has been undertaken regarding specific recommendations to athletes.

Is sports nutrition a profession? Sports nutrition is becoming increasingly recognized as an important factor for optimal athletic performance. Sports nutrition is sometimes referred to as exercise nutrition when coupled with exercise designed for health-related fitness, as discussed in the previous section, but that term is less frequently used. Several factors suggest that sports nutrition has become a profession and is a viable career opportunity. Professional Associations Several professional associations, such as the Sports and Cardiovascular Nutritionists (SCAN) subsection of the American Dietetic Association, and the International Society of Sports Nutrition, are involved in the application of nutrition to sport, health, and wellness. Certification Programs Several professional and sportsgoverning organizations have developed a recognized course of study or certification program to promote the development of professionals who can provide athletes with sound information about nutrition. For example, the American Dietetic Association has established a certification program for specialists in Sports Dietetics while the International Olympic Committee offers a Diploma in Sports Nutrition.

C H A P T E R 1 Introduction to Nutrition for Health, Fitness, and Sports Performance

Research Productivity Numerous exercise-science research laboratories at major universities are dedicated to sports nutrition research. Almost every scientific journal in sport/exercise science, and even in general nutrition, appears to contain at least one study or review in each issue that is related to sports nutrition. International Meetings Numerous international meetings have focused on sports nutrition, some meetings highlighting nutritional principles for a specific sport, such as soccer or track and field. Consensus Statements and Position Stands Several international sports-governing organizations have developed consensus statements on nutrition for their specific sport. For example, the International Association of Athletics Federations (IAAF) recently released a consensus statement on nutrition for the sport of athletics (track, field, and related events). A more generalized position stand entitled “Nutrition and Athletic Performance” was issued jointly by the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine. The American College of Sports Medicine, in concert with the International Olympic Committee and the European Congress of Sport Sciences, is in the process of publishing a joint position statement on the role of supplements in the athlete’s diet. College Courses Many colleges and universities throughout the world have developed courses in sports nutrition to help prepare future coaches, athletic trainers, and other sports medicine personnel to better advise athletes on sound nutritional practices. Some universities that have departments of nutrition and sport/exercise science have developed complete curricular programs of study in sports nutrition. Career Opportunities Sports nutritionists are employed by professional sport teams and athletic departments of major universities to design optimal nutritional programs for their athletes. Some dieticians market themselves as full-time or part-time sports nutritionists within their communities. Sports nutrition as we know it today has a relatively short history, but it appears to be an important aspect in the total preparation of the athlete. www.acsm.org You may access the position stand entitled “Nutrition and Athletic Performance” by clicking on Publications and then Position Stands

Are athletes today receiving adequate nutrition? Survey data evaluating the dietary habits of athletes may vary tremendously, particularly when different sports are compared. An excellent review is presented by Sarah Short of Syracuse University who provides a critique of the validity and usefulness of various survey techniques used to assess average nutrient intake. The usual method in these studies is to obtain a 3- to 7-day record of the food intake of the athletes and then use computer analyses to compare their intake

with the RDA for a variety of nutrients. One of the problems with dietary survey research is improper responses to the survey by the athletes. For example, in a study evaluating the diet of female gymnasts, Jonnalagadda and others noted that some athletes may underreport energy intake, which may distort the nutritional analysis and indicate a dietary deficiency when there is none. Nevertheless, numerous dietary surveys of various athletic groups provide a broad view of dietary adequacy. Recent surveys regarding dietary intake of athletes present mixed results. Some studies find that athletes may be eating as well as or better than nonathletes and meeting or exceeding the RDA for many nutrients, while other studies reveal diets inadequate in energy intake or specific nutrients. However, as Mullins and others note, even though the dietary status of the group of athletes as a whole may appear appropriate, wide individual variability indicates that individual athletes may be undernourished. Inadequate nutrient intakes have been reported for athletes of both genders and all age levels, ranging in athletic ability from the high school level to Olympic caliber. Athletes involved in weight-control sports, such as dancers, gymnasts, bodybuilders, distance runners, and wrestlers, are most susceptible to poor nutrient intake. Female athletes were much more likely than males to incur inadequate nutrient intake. The most significant dietary deficiency in most studies was iron, although zinc, calcium, protein, and several of the B vitamins also were found to be inadequate by several investigators. In many of these studies, including a nationwide survey of elite athletes, inadequate nutrient intake was due to a very low caloric intake. In addition, several studies have revealed a high incidence of eating disorders in these groups of athletes as they adopted bizarre techniques in attempts to control body weight. Although this problem is more prevalent in females, a small percentage of male athletes also exhibit disordered eating behaviors. This topic is addressed in chapter 10. This brief review indicates that some athletic groups are not receiving the recommended allowances for a variety of essential nutrients or may not be meeting certain recommended standards. It should be noted, however, that these surveys have analyzed the diets of the athletes only in reference to a standard, such as the RDA, and many studies have not analyzed the actual nutrient or biochemical status (such as by a blood test) of the athlete or the effects that the dietary deficiency exerted on exercise performance capacity or sport performance. The RDA for vitamins and minerals incorporates a safety factor, so an individual with a dietary intake of essential nutrients below the RDA may not necessarily suffer a true nutrient deficiency. On the other hand, if the athlete does develop a nutrient deficiency, then athletic performance may deteriorate and health may be impaired. For example, Daly and others note that adolescent athletes may be at risk of restricted growth and delayed maturation when intense training is combined with insufficient energy intake, which may impair optimal growth if done long-term. This viewpoint is supported by the American Academy of Pediatrics which indicated decreased bone density could be a related health problem in these athletes. For a number of reasons, dietary surveys indicate that many athletes do not appear to be getting adequate nutrition. For example, one recent study found that only 15 and 26 percent of athletes had www.mhhe.com/williams9

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adequate intakes of carbohydrate and protein, respectively, based on recommendations for athletes. Part of the problem may be that athletes do not possess sufficient knowledge to make appropriate food choices. Christine Rosenbloom, a distinguished sports nutritionist at Georgia State University, and her colleagues indicate that athletes continue to have misconceptions about the roles of specific nutrients in sport performance, and if they chose foods based on these misconceptions then sports performance may suffer. Many athletes may not be getting sound sport nutrition information. In a survey of nutrition practices and knowledge of college varsity athletes, Jacobson and others reported that although some athletes received nutrition information from reliable sources, such as dietitians and athletic trainers (who are required to have a nutrition course for certification), considerable nutrition information was obtained from less reliable sources such as magazines. Many athletes receive nutrition information from their coaches, who may not have the background to provide proper advice, as documented recently by Zinn and others. Surveys of coaches indicated that 60 to 80 percent had not had a formal course in nutrition or were in need of a better nutrition background. Other constraints, such as finances and time, may limit food selection and preparation. Given the numerous dietary surveys indicating that some athletes may not be eating appropriately for their sport, Ziegler and others suggest the need to develop dietary intervention and education programs targeted at promoting optimal nutrient intakes by these athletes, not only to maintain performance, but also to improve longterm health status.

Provide energy for various energy systems

Improve acid-base balance and reduce acidity

Increase bone mineral density and strength

Increases oxygen transport and delivery

Prevent muscle tissue damage

Regulate body temperature

Increase muscle tissue growth

Enhance energyproducing metabolic pathways

Facilitate recovery following exercise

Increase mechanical efficiency

FIGURE 1.9 Nutrients in the foods we eat and dietary strategies may influence

exercise or sport performance in a variety of ways.They may provide energy for the various human energy systems, may help regulate various metabolic processes important to exercise, and may also promote the growth and development of various body tissues and organs important for energy production during exercise.

How does nutrition affect athletic performance? The nutrients in the foods we eat can affect exercise and sports performance in accord with the three major functions of nutrients. First, nutrients may provide energy for the different energy-producing systems discussed in chapter 3. Second, nutrients also help regulate metabolic processes important to energy production and temperature regulation during exercise. Third, nutrients support the growth and development of specific body tissues and organs as they adapt to exercise training; Figure 1.9 highlights some of the roles nutrients play during exercise. A well-planned sport-specific diet will help optimize sports performance, but a poor diet plan may lead to impaired performance. Malnutrition represents unbalanced nutrition and may exist as either undernutrition or overnutrition, that is, an individual does not receive an adequate intake (undernutrition) or consumes excessive amounts of single or multiple nutrients (overnutrition). Either condition can hamper athletic performance. An inadequate intake of certain nutrients may impair athletic performance due to an insufficient energy supply, an inability to regulate exercise 18

Enhance psychological functions

metabolism at an optimal level, or a decreased synthesis of key body tissues or enzymes. On the other hand, excessive intake of some nutrients may also impair athletic performance, and even the health of the athlete, by disrupting normal physiological processes or leading to undesirable changes in body composition.

What should athletes eat to help optimize sport performance? Melinda Manore, an expert in sport nutrition, noted that there is no doubt that the type, amount, composition, and timing of food intake can dramatically affect exercise performance, recovery from exercise, body weight and composition, and health. The importance of nutrition to your athletic performance may depend on a variety of factors, including your gender, your age, your body weight status, your eating and lifestyle patterns, the environment, the type of training you do, and the type of sport or event in which you participate. As an example of the latter point, the nutrient needs of a golfer or baseball player may vary little from those of the nonathlete, whereas those of a marathon runner or ultraendurance triathlete may be altered significantly during training and competition. The opinions offered by researchers in the area of exercise and nutrition relative to optimal nutrition for the athlete run the gamut.

C H A P T E R 1 Introduction to Nutrition for Health, Fitness, and Sports Performance

At one end, certain investigators note that the daily food requirement of athletes is quite similar to the nutritionally balanced diet for everyone else, and therefore no special recommendations are needed. On the other extreme, some state that it is almost impossible to obtain all the nutrients the athlete requires from the normal daily intake of food, and for that reason nutrient supplementation is absolutely necessary. Other reviewers advocate a compromise between these two extremes, recognizing the importance of a nutritionally balanced diet but also stressing the importance of increased consumption of specific nutrients or dietary supplements for athletes under certain situations. The review of the scientific literature presented in this book supports the latter point of view. In general, athletes who consume enough Calories to meet their energy needs and who meet the requirements for essential nutrients should be obtaining adequate nutrition. The dietary guidelines for better health, as discussed previously and expanded upon in chapter 2, are the same for optimal physical performance. The key to sound nutrition for the athletic individual is to eat a wide variety of healthful foods. Although a healthy diet is the foundation of a dietary plan for athletes, modifications may be important for training and competition in various sports. Some basic guidelines regarding eating for training and for competition are presented in chapter 2, whereas details regarding the use of specific nutrients, including related dietary supplements, are presented in the chapter highlighting that nutrient. Some athletes believe that there are super foods or diets that may provide a competitive advantage in sports. Numerous sports supplements are marketed to athletes with this premise in mind, and have been the subject of considerable research by sports nutrition scientists. The following section discusses the general role of such supplements in the enhancement of sports performance.

Ke y C o n c e p t s 䉴 Success in sports is primarily dependent on genetic endowment

and proper training, but nutrition also can be an important contributing factor. 䉴 The major objectives of sports nutrition are to promote good health and adaptations to training, to recover quickly after each training session, and to perform optimally during competition. 䉴 Studies reveal that although athletes desire to eat a diet that may enhance sport performance, their knowledge of nutrition is inadequate, and many are not meeting the dietary recommendations of sport nutritionists. 䉴 In general, the diet that is optimal for health is optimal for sports performance. However, athletes involved in certain sports may benefit from specific dietary modifications.

Ergogenic Aids and Sports Performance: Beyond Training Since time immemorial, athletes have attempted to use a wide variety of techniques or substances in attempts to enhance sports performance beyond the effects that could be obtained through

training. In sport and exercise science terminology, such techniques or substances are referred to as ergogenic aids.

What is an ergogenic aid? As mentioned previously, the two key factors important to athletic success are genetic endowment and state of training. At certain levels of competition, the contestants generally have similar genetic athletic abilities and have been exposed to similar training methods, and thus they are fairly evenly matched. Given the emphasis placed on winning, many athletes training for competition are always searching for the ultimate method or ingredient to provide that extra winning edge. Indeed, one report suggests that two of the key factors leading to better athletic records in recent years are improved diet and ergogenic aids. The word ergogenic is derived from the Greek words ergo (meaning work) and gen (meaning production of), and is usually defined as to increase potential for work output. In sports, various ergogenic aids, or ergogenics, have been used for their theoretical ability to improve sports performance by enhancing physical power, mental strength, or mechanical edge. There are several different classifications of ergogenic aids, grouped according to the general nature of their application to sport. The first two classifications are often referred to as performance-enhancing techniques, whereas the last three classifications involve taking some substance into the body and are known as performance-enhancing substances. We have listed several major categories with an example of one theoretical ergogenic aid for each. Mechanical Aids Mechanical, or biomechanical, aids are designed to increase energy efficiency, to provide a mechanical edge. Lightweight racing shoes may be used by a runner in place of heavier ones so that less energy is needed to move the legs and the economy of running increases. Psychological Aids Psychological aids are designed to enhance psychological processes during sport performance, to increase mental strength. Hypnosis, through posthypnotic suggestion, may help remove psychological barriers that may limit physiological performance capacity. Physiological Aids Physiological aids are designed to augment natural physiological processes to increase physical power. Blood doping, or the infusion of blood into an athlete, may increase oxygen transport capacity and thus increase aerobic endurance. Pharmacological Aids Pharmacological aids are drugs designed to influence physiological or psychological processes to increase physical power, mental strength, or mechanical edge. Caffeine, a commonly used drug, may increase physical power and mental strength to help improve performance in a variety of exercise tasks. Nutritional Aids Nutritional aids are nutrients designed to influence physiological or psychological processes to increase physical power, mental strength, or mechanical edge. Protein supplements may be used by strength-trained athletes in attempts to increase muscle mass because protein is the major dietary constituent of muscle. www.mhhe.com/williams9

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Why are nutritional ergogenics so popular? Probably the most used ergogenic aids are dietary supplements. Dietary supplements marketed to physically active individuals are commonly known as sports nutrition supplements, or simply sports supplements. Companies market their products as “Supplements for the Competitive Athlete,” and the overall sports supplement business is brisk. According to Dancho and Manore, sports supplements constitute approximately 10 percent of total dietary supplement sales. Sports supplements are popular worldwide. Sports supplements are used by all types of athletes: male and female, young and old, professional and amateur. Reports indicate that 90 percent or more of elite, international-class athletes consume dietary supplements. Other surveys document significant use among high school and collegiate athletes, military personnel in elite groups such as SEALS, and fitness club members. Sports supplements are popular for several reasons. Athletes have believed that certain foods may possess magical qualities, so it is no wonder that a wide array of nutrients or special preparations have been used since time immemorial in attempts to run faster, jump higher, or throw farther. Shrewd advertising and marketing strategies promote this belief, enticing many athletes and physically active individuals to try sports supplements. Many of these products may be endorsed by professional athletes, giving the product an aura of respectability. Specific supplements also may be recommended by coaches and fellow athletes. Additionally, as drug testing in sports gets increasingly sophisticated, leading to greater detection of pharmacological ergogenics, many athletes may resort to sports supplements, believing them to be natural, safe, and legal. However, as noted below, this may not be the case.

Are nutritional ergogenics effective? There are a number of theoretical nutritional ergogenic aids in each of the six major classifications of nutrients, and athletes have been known to take supplements of almost every nutrient in attempts to improve performance. Here are a few examples: Carbohydrate. Special compounds have been developed to facilitate absorption, storage, and utilization of carbohydrate during exercise. Fats. Special fatty acids have been used in attempts to provide an alternative fuel to carbohydrate. Protein. Special amino acids derived from protein have been developed and advertised to be more potent than anabolic steroids in stimulating muscle growth and strength development. Vitamins. Special vitamin mixtures and even “nonvitamin vitamins,” such as vitamin B15, have been ascribed ergogenic qualities ranging from increases in strength to improved vision for sport. Minerals. Special mineral supplements, such as chromium, vanadium, and boron, have been advertised to be anabolic in nature. Water. Special oxygenated waters have been developed specifically for aerobic endurance athletes, theoretically designed to increase oxygen delivery. In addition to essential nutrients derived from foods, there are literally hundreds of nonessential substances or compounds that are clas20

sified as food supplements and targeted to athletes as potent ergogenics, such as creatine, L-carnitine, coenzyme Q10, inosine, octacosonal, and ginseng. Moreover, many products contain multiple ingredients, each purported to enhance sports performance. For example, one of the “Energy” drinks on the market includes carbohydrates, amino acids, vitamins, minerals, metabolites, herbs, and caffeine. Nutrient supplementation above and beyond the RDA is not necessary for the vast majority of athletes. In general, consumption of specific nutrients above the RDA has not been shown to exert any ergogenic effect on human physical or athletic performance. However, there are some exceptions. As noted in chapters 4 through 10, there may be some justification for nutrient supplementation or dietary modification in certain athletes under specific conditions, particularly in cases where nutrient deficiencies may occur. Some specific dietary supplements and food drugs may also possess ergogenic potential under certain circumstances. The effectiveness of almost all of the popular nutritional ergogenics, including the essential nutrients, the nonessential nutrients, the food drugs caffeine and alcohol, the steroid precursor androstenedione, and other agents, will be covered in this book. A summarization is presented in chapter 13.

Are nutritional ergogenics safe? The majority of over-the-counter dietary supplements, particularly those containing essential nutrients, appear to be safe for the general population when taken in recommended dosages. However, some dietary supplements, including sports supplements, may contain ingredients that pose health risks in several ways. First, using the “if one is good, then ten is better” mentality, athletes may overdose. The FDA has noted that some sports supplements contain chemicals that have been linked to numerous serious illnesses and even death. Second, the product label may not contain all the ingredients or may contain ingredients not listed. Several products analyzed independently have been shown to contain powerful stimulants which could have adverse effects. Hermann Engels, a noted exercise scientist at Wayne State University, says that medical authorities are concerned about possible adverse reactions of athletes to commercially sold sports supplements, and that this may be particularly so with young athletes. A recent Consumer Reports article noted that adolescents are as likely to use sports supplements as adults. Young athletes, who may have a sense of invincibility, may not possess the judgment to use appropriate dosages and may overdose. Supplements that are mislabeled and contain unlisted substances pose a serious health threat. Some companies are unscrupulous and may not list a chemical, such as ephedrine, that could provide a stimulant effect which, unknowingly, you may attribute to the listed ingredients and thus think the product is effective. Fortunately, the government is working to have all ingredients listed on dietary supplement labels, and hopefully appropriate warnings of any potential health risks will be provided as new laws take effect. Currently, some companies are voluntarily adding warnings in their advertisements and product labels.

C H A P T E R 1 Introduction to Nutrition for Health, Fitness, and Sports Performance

Throughout this text, possible health risks associated with nutritional ergogenics will be discussed when such information is available.

Are nutritional ergogenics legal? The use of pharmaceutical agents to enhance performance in sport has been prohibited by the governing bodies of most organized sports. The use of drugs in sports is known as doping, and the Medical Commission of the International Olympic Committee has provided an extensive list of drugs and doping techniques that have been prohibited. At the present time, all essential nutrients are not classified as drugs and are considered to be legal for use in conjunction with athletic competition. Most other food substances and constituents sold as dietary supplements are also legal. However, some dietary supplements are prohibited, such as androstenedione, because they are classified as anabolic steroids, which are prohibited drugs. Other dietary supplements may contain substances that are prohibited; for example, Chinese Ephedra and some forms of ginseng may contain ephedrine, a prohibited stimulant drug. The National Football League (NFL) has developed strict requirements for the manufacturing of dietary supplements approved for use by its players. The National Collegiate Athletic Association (NCAA) prohibits member institutions from providing ergogenic nutritional supplements to student athletes at any time, while permitting nonergogenic nutritional supplements provided they do not contain NCAA-banned substances. Ron Maughan, an international expert in sports nutrition, noted that contamination of sports supplements that may cause an athlete to fail a doping test is widespread. The scientific literature contains numerous reports of athletes testing positive for doping who claim that they have not taken drugs, only dietary supplements. Although the risk of an inadvertant positive doping test through the use of sports supplements is small, Baylis and others note it is a real problem facing athletes who may be tested for drug use. Supporting this viewpoint, independent analyses of sports supplements, such as those reported by the research groups of Green and Kamber, revealed prohibited substances not listed on the product label. It is hoped that, with pending legislation, all ingredients will be listed in correct amounts on dietary supplement labels. In the meantime, athletes should consult with appropriate authorities before using any sports nutrition supplements marketed as performance enhancers. Nevertheless, the United States Anti-Doping Agency notes that the use of nutritional or dietary supplements is completely at the athlete’s own risk, even if the supplements are “approved” or “verified.” www.supplementwatch.com Click on Product Review, and then Sports & Fitness. Provides a review of specific sports supplements. www.ais.org.au Click on Sports Science, then Nutrition, then Supplements.The Australian Institute of Sport lists sports supplements approved for use and those that should not be used or used only under certain circumstances.

Ke y C o n c e p t s 䉴 Probably the most prevalent ergogenic aids used to increase

sport performance are those classified as nutritional, for theoretical nutritional aids may be found in all six classes of nutrients. 䉴 Although most sports supplements are safe and legal, most are not effective ergogenic aids, and some are unsafe or illegal. Before using a sports supplement, athletes should try to determine if it is effective, if it is safe, and if it is legal.

C h e c k f o r Yo u r s e l f Go to a health food store, peruse the multiple dietary supplements available, and ask the clerk for advice on a supplement to help you enhance your sport performance, such as increasing your muscle mass or losing body fat.Write down the advice and check out advertisements on the Internet.Then, go to www.supplementwatch.com, check their comments on the supplement, and compare the findings.

Nutritional Quackery in Health and Sports Increasing numbers of dietary supplements are being marketed to the general population as health enhancers and to athletes as performance enhancers. Unfortunately, many of the products that advertise extravagant claims of enhanced health or performance are promoted by unscrupulous entrepreneurs, have no legitimate basis, and may be regarded as quackery.

What is nutritional quackery? According to the Food and Drug Administration (FDA), quackery, as the term is used today, refers not only to the fake practitioner but also to the worthless product and the deceitful promotion of that product. Untrue or misleading claims that are deliberately or fraudulently made for any product, including food products, constitute quackery. The American Dietetic Association, in its position statement on food and nutrition misinformation, notes that such misinformation can have harmful effects on the health and economic status of consumers. Knowledge relative to all facets of life, the science of nutrition included, has increased phenomenally in recent years. Thousands of studies have been conducted, revealing facts to help unravel some of the mysteries of human nutrition. The ADA indicates that consumers are taking greater responsibility for self-care and are eager to receive food and nutrition information. However, that creates opportunities for nutrition misinformation, health fraud, and quackery to flourish. The ADA further notes that the media are consumers’ leading source of nutrition information, but that news reports of nutrition research often provide inadequate depth for consumers to make wise decisions. Certain individuals may capitalize on these research findings for personal financial gain. For example, isolated nutritional facts may be distorted or the results www.mhhe.com/williams9

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of a single study will be used to market a specific nutritional product. Health hustlers will use this information to capitalize on people’s fears and hopes, be it the fear that the nutritional quality of our food is being lessened by modern processing methods or the hope of improved athletic performance capacity. Quackery is big business. It has been estimated that over twenty-five billion dollars a year are spent on questionable health practices in the United States. A substantial percentage of this amount has been spent on unnecessary nutritional products. Authorities in this area have noted that the amount of misinformation about nutrition is overwhelming, and it is circulated widely, particularly by those who may profit from it. Although we may still think of quacks as sleazy individuals selling patent medicine from a covered wagon, the truth is quite different. Nutritional quacks today are super salespeople, using questionable scientific information to give their products a sense of authenticity and credibility and using sophisticated advertising and marketing techniques. As noted previously, there are some bona fide health benefits associated with the foods we eat, but as shall be noted in chapter 2, federal legislation provides strict guidelines regarding the placement of health claims on food labels for most of the packaged foods that we buy. Such may not be the case, however, with dietary supplements. Before the passage of the 1994 Dietary Supplements Health and Education Act (DSHEA), many extravagant health claims were made by some unscrupulous companies in the food supplement industry. As an example, the label of one secret formula noted that it would help you lose excess body fat while sleeping, which is untrue. Although the DSHEA was designed to eradicate such fraudulent health claims, dietary supplements appear to have more leeway than packaged foods to infer health benefits. Technically, labels on dietary supplements are not permitted to display scientifically unsupported claims. However, companies are allowed to make general claims like “boosts the immune system” if, for example, the product contains a nutrient, such as zinc, that has been deemed important in some way to immune functions in the body. Although companies may not claim that the product prevents diseases associated with impaired immune functions, such as the common cold, cancer, or AIDS, the consumer may erroneously make such an assumption. Many companies now use a disclaimer on their labels, indicating that the effectiveness of their products has not been evaluated by the FDA. They may also provide information in the form of a reprint of an article, a brochure with highlighted research, or other printed materials that are distributed in connection with the sale of the product. Many dietary supplement companies have developed infomercials for television or home pages on the Internet to provide comparable biased advertising information to potential consumers. Although these advertising strategies may contain fraudulent information, the federal agencies that monitor such practices are understaffed and cannot litigate every case of misleading or dishonest advertising. Thus, unsuspecting consumers may be lured into buying an expensive health-food supplement that has no scientific support of its effectiveness. However, the FDA has plans in motion to remedy this problem by the year 2010. Nutritional quackery is widespread as documented in the recent position stand on food and nutrition misinformation by the American Dietetic Association. Years ago J.V. Durnin, an international authority 22

on nutrition and exercise, stated that there is still no sphere of nutrition in which faddism, misconceptions, ignorance, and quackery are more obvious than in athletics, a situation which continues today.

Why is nutritional quackery so prevalent in athletics? As with nutritional quackery in general, hope and fear are the motivating factors underlying the use of nutritional supplements by athletes. They hope that a special nutrient concoction will provide them with a slight competitive edge, and they fear losing if they do not do everything possible to win. In this regard, there are four factors within the athletic environment that help nurture these hopes and fears. First, eating behavior may be patterned after some star athlete who is successful in a given sport, such as an Olympic champion or professional athlete who attributed part of their success to a sport supplement. For example, sales of androstenedione skyrocketed when Mark McGwire, baseball’s home-run record holder at the time, revealed that he had used it as a dietary supplement. Although androstenedione had been regulated as a dietary supplement at the time, it now is regulated as a drug and its use is prohibited in sports. More details are presented in chapter 13. Second, many coaches may suggest to their athletes that certain foods or food supplements are essential to success. Surveys reveal that many athletes still receive nutritional information from their coaches, but as noted previously, these surveys also reveal that many coaches have poor backgrounds in nutrition. Thus, misconceptions adopted by coaches in the past may be perpetuated in their athletes. Third, misinformation also may be found in leading sports magazines and books, which often present articles on nutrition for the athlete based upon very questionable research. As noted previously, Jacobson and others reported that athletes receive considerable nutrition information from magazines. Unfortunately, many people believe that if it is in print, then it is true. Some of these magazines and books are published by companies that sell nutritional ergogenics, so the information in the article may be biased. Fourth, and probably the most significant factor contributing to nutritional quackery in sports, is direct advertising of nutritional products marketed specifically for the athlete, as suggested by the fabricated example presented in figure 1.10. Literally hundreds of nutritional supplements are advertised for athletic consumption. For example, in a survey of only five magazines targeted to bodybuilding athletes, Grunewald and Bailey reported that over 800 performance claims were made for 624 commercially available supplements ranging from amino acids to yohimbine. The authors noted that most claims were not supported by research. Direct advertising is often combined with several of the methods noted previously for perpetuating nutritional information. Often star athletes are hired to endorse a particular product. One advertisement pictured one of America’s leading marathoners with the name of a nutritional supplement emblazoned across his running shirt and the statement that this product was an important part of his training program. Also, many sports magazines will run articles on the ergogenic benefits of a particular nutrient, and in close

C H A P T E R 1 Introduction to Nutrition for Health, Fitness, and Sports Performance

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for athletes.

proximity to the article place an advertisement for a product that contains that nutrient. Freedom of speech guaranteed by the First Amendment permits the author of the article to make sensational and deceptive claims about the nutrient. However, freedom of speech does not extend to advertising, so that fraudulent or deceptive claims may be grounds for prosecution by the FDA or the Federal Trade Commission (FTC). Thus, by cleverly positioning the article and the advertisement, the promoter can make the desired claims about the value of the product and yet avoid any illegality. Classic examples of this technique may be found with protein and amino acid supplement advertising in magazines for bodybuilders. Moreover, many advertisements now appear in a format designed to look like a scientific review, but in actuality are deceptive advertisements for sport supplements. Most of these advertised products are economic frauds. The prices are exorbitant in comparison to the same amount of nutrients that may be obtained in ordinary foods. Besides being an economic fraud, these products are an intellectual fraud, for there is very little scientific evidence to support their claims. Simple basic facts about the physiological functions of the nutrients in these products are distorted, magnified, and advertised in such a way as to make one believe they will increase

athletic performance. Unfortunately, in the area of nutrition and sport, it is very easy to distort the truth and appeal to the psychological emotions of the athlete. Dr. Robert Voy, former chief medical officer of the United States Olympic Training Center, has noted that we have abandoned athletes to the hucksters and charlatans. Athletes are wasting their money on worthless, and sometimes harmful, substances. David Lightsey has documented such quackery in his book Muscle, Speed, and Lies: What the Sports Supplement Industry Does Not Want Athletes or Consumers to Know.

How do I recognize nutritional quackery in health and sports? It is often difficult to differentiate between quackery and reputable nutritional information, but the following may be used as guidelines in evaluating the claims made for a nutritional supplement or nutritional practice advertised or recommended to athletes and others. If the answer to any of these questions is yes, then one should be skeptical of such supplements and investigate their value before investing any money. 1. Does the product promise quick improvement in health or physical performance? 2. Does it contain some secret or magical ingredient or formula? 3. Is it advertised mainly by use of anecdotes, case histories, or testimonials? 4. Are currently popular personalities or star athletes featured in its advertisements? 5. Does it take a simple truth about a nutrient and exaggerate that truth in terms of health or physical performance? 6. Does it question the integrity of the scientific or medical establishment? 7. Is it advertised in a health or sports magazine whose publishers also sell nutritional aids? 8. Does the person who recommends it also sell the product? 9. Does it use the results of a single study or dated and poorly controlled research to support its claims? 10. Is it expensive, especially when compared to the cost of equivalent nutrients that may be obtained from ordinary foods? 11. Is it a recent discovery not available from any other source? 12. Is its claim too good to be true? Does it promise the impossible?

Where can I get sound nutritional information to combat quackery in health and sports? The best means to evaluate claims of enhanced health or sport performance made by dietary supplements or other nutritional practices is to possess a good background in nutrition and a familiarity with related high-quality research. Unfortunately, most individuals, including most athletes, coaches, and physicians, have not been exposed to such an educational program, so they must either take formal course work in nutrition or sport nutrition, develop a reading program in nutrition for health and sport, or consult with an expert in the field. www.mhhe.com/williams9

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This book has been designed to serve as a text for a college course in nutrition for health-related and sports-related fitness, but it may also be read independently. It is an attempt to analyze and interpret the available scientific literature as to how nutrition may impact upon health and sports performance, and to provide some simple guidelines for physically active individuals to help improve their health or athletic performance. It should provide the essential science-based (evidence-based) information you need to plan an effective nutritional program, either for yourself, other physically active individuals, or athletes, and to evaluate the usefulness of many nutritional supplements or practices designed to improve health or sport performance. Here are some key resources. Books Numerous reputable books that detail the relationship of nutrition to health and sports performance are available, and many are cited in the reference list at the end of this chapter. Government, Health Professional, Consumer, and Commercial Organizations Accurate information relating nutrition to health is published by governmental agencies such as the FDA and USDA; health professional groups such as the American Dietetic Association, Dietitians of Canada, American College of Sports Medicine, and the American Medical Association; consumer groups such as Consumers Union and Center for Science in the Public Interest; and commercial groups such as the National Dairy Council and the PepsiCo’s Gatorade Sports Science Institute. Excellent materials relative to nutrition may be obtained free or at small cost from some of these organizations. www.health.harvard.edu Harvard Medical School Website provides the latest health information on a variety of health conditions, including lifestyle and nutrition advice. www.hsph.harvard.edu/nutritionsource Excellent Website for nutrition information from the Harvard School of Public Health. www.gssiweb.com Website for the Gatorade Sports Science Institute, providing detailed reviews on various topics in sports nutrition. www.healthfinder.gov U.S.Department of Health and Human Services Website for information on various health topics,including nutrition. http://medlineplus.gov National Library of Medicine, a comprehensive health-information retrieval Website. www.MerckSource.com Unbiased health information, including nutrition and exercise. www.WebMD.com Covers a wide variety of health-related issues, including proper nutrition and exercise.

Scientific Journals Many scientific journals publish reputable findings about nutrition, exercise, and health. These technical journals may not be readily available in public libraries but may be found in university and medical libraries. Examples of such publications include Medicine & Science in Sports & Exercise, The Journal of the American Dietetic Association, American Journal of Clinical Nutrition, Sports Medicine, and the International Journal of Sport Nutrition and Exercise Metabolism. www.pubmed.gov National Library of Medicine Website provides abstracts of original research studies and excellent reviews and meta-analyses. 24

Popular Magazines Articles in popular health and sports magazines may or may not be accurate. The credentials of the author, if listed, should be a good guide to an article’s authenticity. A Ph.D. listed after the author’s name may not guarantee accuracy of the content of the article. Be wary of publications emanating from organizations or publishers that also sell nutritional supplements. Consultants Nutritional consultants are another source of information. Such consultants should have a solid background in nutrition, particularly sports nutrition if they are to advise athletes. The consultant should be a registered dietitian (RD) or possess appropriate professional certification, such as the Certified Nutrition Specialist (CNS). He or she should be a member of a reputable organization of nutritionists, such as the American Dietetic Association (ADA). You may contact the ADA at its Website address and they will provide you with the name of a local dietitian. Other recognized nutritional organizations include the American Society for Nutrition Sciences, the American College of Nutrition, and the American Society for Clinical Nutrition. Qualified nutritionists are able to provide you with nutritional advice to help you meet your health goals. www.eatright.org Contact the American Dietetic Association for the names of local dietitians, as well as other sources of sound nutrition information.

As noted previously, the American Dietetic Association’s Commission on Dietetic Registration, working with members of Sports, Cardiovascular and Wellness Nutritionists (SCAN), has developed a certification program for registered dietitians (RD) who work in sports. A qualified sports nutritionist will be able to assess your nutritional status, including such variables as body composition, dietary analysis, and eating and lifestyle patterns, and relate these nutritional factors to the physiological and related nutritional demands of your sport or exercise program, providing you with a plan to help you reach your performance goals. The International Olympic Committee (IOC) also has developed a program of study leading to the IOC Diploma in Sports Nutrition. http://www.scandpg.org/mapsearch.php Use this Website to find a sports nutritionist. Click on your state to find one closest to you. Those with the CSSD designation have earned the designation as a Certified Specialist in Sports Dietetics

Be wary of individuals who do not possess professional degrees or appropriate certification, such as “experts” in nutrition or fitness. Many states do not have regulations restricting the use of various terms, such as nutritionist or fitness professional. Although these individuals may have some practical experience to help people change their diets and initiate exercise programs, they normally do not have the depth of knowledge required in many cases. For example, Healey and others recently reported that employees of natural/health food stores did not provide appropriate health information to investigators posing with symptoms of severe asthma. For proper nutritional advice, be certain to ask for proof of certification from recognized nutrition professional groups as cited previously. For fitness professionals, check

C H A P T E R 1 Introduction to Nutrition for Health, Fitness, and Sports Performance

for certification by such groups as the American College of Sports Medicine (ACSM), the American Council on Exercise (ACE), or the National Strength and Conditioning Association (NSCA). Websites Several Websites listed previously provide reputable information. Although some commercial (.com) Websites provide trustworthy information, and may be cited in this text, others may not be as reputable as they may be sponsored by unethical supplement companies. In general, education (.edu), government (.gov), and organization (.org) Websites provide trustworthy information. Dancho and Manore provide guidelines for evaluating dietary supplement Websites and provide a list of reputable sites, most of which are also listed at www.mhhe.com/williams.

Ke y C o n c e p t s 䉴 Nutritional quackery is widespread as related to the purported

benefits of specific dietary supplements, particularly so with dietary supplements marketed to athletes. 䉴 There are a number of guidelines to help identify quackery and false claims of dietary supplements, but one of the critical points to consider is if the claim simply appears to be too good to be true. 䉴 The best means to counteract nutritional quackery is to possess a good background in nutrition. Reputable sources of information are available to help provide contemporary viewpoints on the efficacy, safety, and legality of various dietary supplements for health or sport.

Research and Prudent Recommendations By now you should realize that nutrition and exercise may influence our health and sport performance. But how do we know what effect a nutrient, food, or dietary supplement we consume or exercise program we undertake will have on our health or performance? To find answers to specific questions, we should rely on the findings derived from scientific research which is the heart of evidence-based medicine. As sophisticated sciences, nutrition and exercise science have a relatively short history. Not too long ago, nutrition scientists were concerned primarily with identifying the major constituents of the foods we eat and their general functions in the human body, while those investigating exercise concentrated more on its application to enhance sports performance. More recently, however, numerous scientists have turned their attention to the possible health benefits of certain foods and various forms of exercise, and, in the case of sport scientists, the possible applications to athletic performance. These scientists are not only attempting to determine the general effects of diet and exercise on health and performance, but are also investigating the effects of specific nutrients at the molecular and genetic level to determine possible mechanisms of action to improve health or performance in sport. Because this book makes a number of nutritional (and some exercise) evidence-based recommendations relative to sports and health, it is important to review briefly the nature and limitations of nutritional and exercise research with humans. For the purpose of

this discussion, our emphasis will be on nutritional research, although the same research considerations apply to exercise as well.

What types of research provide valid information? Several research techniques have been used to explore the effect of nutrition on health or athletic performance. The two major general categories have been epidemiological research and experimental research, and Temple provides an excellent overview of the challenges of research design in the study of nutrition and disease. Epidemiological research, also known as observational research, involves studying large populations to find relationships between two or more variables, such as dietary fat and heart disease. However, the treatment of interest, such as dietary fat, is not assigned to the subjects. Their normal diet and its relationship to the development of heart disease is the main variable of interest. There are various forms of epidemiological research. One general form uses retrospective techniques. In this case, individuals who have a certain disease are identified and compared with a group of their peers, called a cohort, who do not have the disease. Researchers then trace the history of both groups through interviewing techniques to identify dietary practices that may have increased the risk for developing the disease. Another general form of epidemiological research uses prospective techniques. In this case, individuals who are free of a specific disease are identified and then followed for years, during which time their diets are scrutinized. As some individuals develop the disease and others do not, the investigators then attempt to determine what dietary behaviors may increase the risk for the disease. Epidemiological research helps scientists identify important relationships between nutritional practices and health. For example, years ago several epidemiological studies reported that individuals who consumed a diet high in fat were more likely to develop heart disease. One should note that such research does not prove a cause and effect relationship. Although these studies did note a deleterious association between a diet high in fat and heart disease, they did not actually prove that fat consumption (possible cause) leads to heart disease (possible effect), but only that some form of relationship between the two existed. However, in some cases the relationship between a lifestyle behavior and a disease is so strong that causality is inferred. In this regard, epidemiologists often calculate and report relative risks (RR) or odds ratios (OR), which are probability estimates of getting some disease by practicing some unhealthful behavior. A RR of 1.0 is normal probability, so if a study reports a RR of 2.5 for developing heart disease in individuals who consumed a diet rich in saturated fatty acids, such diets may increase one’s risk 2.5 times normal. Conversely, if a study reports a RR of 0.5 for developing heart disease by consuming a pure vegetarian diet, such diets may cut heart disease risk in half. Epidemiological research is useful in identifying relationships between variables and generating hypotheses, and is often a precursor to experimental research. Experimental research is essential to establishing a cause and effect relationship (figure 1.11). In human nutrition research, experimental studies are often referred to as randomized clinical trials (RCTs) or intervention studies, usually involving a treatment www.mhhe.com/williams9

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ease, should you continue to consume a high-fat diet? The answer to this question, as we shall see later, is “not necessarily.” Most of the research designed to explore the effect of nutrition on sport performance is experimental in nature, and of a much shorter time frame compared to those studies investigating the relationship of nutrition and health. Additionally, most sports nutrition studies are conducted in a laboratory with tight control of extraneous variables. Very few studies have actually investigated the effect of nutritional strategies on actual competitive sport performance. Nevertheless, although most of our information about the beneficial effects of various nutritional strategies on sport performance is derived from laboratory-based research, many of these studies use laboratory protocols designed to mimic the physiologic demands of the sport. In later chapters, as we discuss the effects of various nutritional strategies or dietary supplements on sports performance, we will often refer to studies that have problems with their experimental methodology, but we will also note studies that are well controlled. Following are some major questions you should ask when evaluating the experimental methodology of a study to see if it has been well designed. We shall use research with creatine supplementation as an example.

F I G U R E 1 . 1 1 Well-controlled experimental research serves as the basis underlying recommendations for the use of nutritional strategies to enhance health status or sport performance.

group and a control, or placebo, group. RCTs may involve studying a smaller group of subjects under tightly controlled conditions for a short time frame, or larger population groups living freely over a long time frame. In RCTs an independent variable (cause) is manipulated so that changes in a dependent variable (effect) can be studied. If we continue with the example of fat and heart disease, a large (and expensive) clinical intervention study could be designed to see whether a low-fat diet could help prevent heart disease. Two groups of subjects would be matched on several risk factors associated with the development of heart disease, and over a certain time, say 10 years, one group would receive a low-fat diet (treatment, or cause) while the other would continue to consume their normal high-fat diet (control or placebo). At the end of the experiment, the differences in the incidence of heart disease (effect) between the two groups would be evaluated to determine whether or not the low-fat diet was an effective preventive strategy. Bouchard presents an excellent detailed overview of the quality of different research-based sources of evidence, noting that RCTs with large populations represent the richest source of data and are generally considered the gold standard for evidence-based decision making. If the results of a RCT showed that consumption of a low-fat diet had no effect upon the incidence rate of heart dis26

1. Is there a legitimate reason for creatine supplementation? Theoretically, creatine may add to the stores of creatine phosphate in the muscle, an important energy source. 2. Were appropriate subjects used? As creatine phosphate may theoretically benefit power performance, trained strength athletes would be ideal subjects. 3. Are the performance tests valid? Validated tests should be used to collect data on the dependent variable, in this case valid power tests. 4. Was a placebo control used? A placebo similar in appearance and taste to creatine should be used in the control trial. Ideally, a control trial in which no substance is consumed should be incorporated into the study. Beedie and others found that inert substances could induce a positive (placebo) effect or even a negative (nocebo) effect on performance, depending on the respective perception of the subject. 5. Were the subjects randomly assigned to treatments? Subjects should be randomly assigned to separate groups, either the treatment (creatine) or the control (placebo) group. In a repeatedmeasures design, in which all subjects take both the creatine and the placebo in different trials, the order of administration of the creatine and placebo are counterbalanced, which is known as a crossover design. In general, a repeated-measures design is preferable because each subject serves as his or her own control. 6. Was the study double-blind? Neither the investigators nor the subjects should know which groups received the treatment or the placebo until the conclusion of the study. 7. Were extraneous factors controlled? Investigators should try to control other factors that may influence power, such as physical training, diet, and activity prior to testing. 8. Were the data analyzed properly? Appropriate statistical techniques should be used to reduce the risk of statistical error. Using a reasonable number of subjects also helps to minimize statistical error.

C H A P T E R 1 Introduction to Nutrition for Health, Fitness, and Sports Performance

Most experienced contemporary investigators generally use similar sophisticated research designs to generate meaningful data, and their studies appear in peer-reviewed journals. A peer-reviewed journal uses a process whereby each manuscript submitted undergoes a review and critique by several experts who recommend for or against publication. However, some researchers do not apply such strict protocols, and thus may produce erroneous conclusions.

Why do we often hear contradictory advice about the effects of nutrition on health or physical performance? It is very difficult to conduct nutritional research about health and athletic performance with human subjects. For example, many diseases such as cancer and heart disease are caused by the interaction of multiple risk factors and may take many years to develop. It is not an easy task to control all of these risk factors in freely living human beings so that one independent variable, such as dietary fat, could be isolated to study its effect on the development of heart disease over 10 or 20 years. In a similar manner, numerous physiological, psychological, and biomechanical factors also influence athletic performance on any given day. Why can’t athletes match their personal records day after day, such as the world-record 43.18-second 400-meter dash performance by Michael Johnson? Because their physiology and psychology vary from day to day, and even within the day. Although well-designed studies in peer-reviewed (reviewed by several other experts) scientific journals serve as the basis for making an informed decision as to whether or not to use a particular nutritional strategy or dietary supplement to enhance health or sport performance, it is important to realize that the results from one study with humans do not prove anything. For example, Ioannidis recently noted that even the most highly cited RCTs, particularly small ones with a limited number of subjects, may be challenged and refuted over time. Although most investigators attempt to control extraneous factors that may interfere with the interpretation of the results of their study, there may be some unknown factor that leads to an erroneous conclusion. For example, early epidemiological studies investigating the role of dietary fat in heart disease may not have adjusted their findings for the type of fat or intake of dietary fiber, which may help retard the development of heart disease. Thus, the results of such a study may lead to the conclusion that diets high in fat do not contribute to the development of heart disease. Consequently, for this and other reasons, the results of single studies, whether epidemiological or experimental, should be taken with a grain of salt, figuratively speaking of course. The Center for Science in the Public Interest recently published an article entitled “Behind the Headlines,” noting that headlines often neglect to consider important limitations to the study. In this regard, Wellman and others indicated that, unfortunately, all too often the media make bold headlines based on the findings of an individual study, and often these headlines may inadvertently exaggerate the findings of the study and their importance to health or physical performance. For example, a newspaper headline might blare that “Coffee drinking causes heart disease” after a study is published that indicated coffee drinking could increase blood cholesterol levels slightly. The study did not show coffee drinking caused heart disease, but only that

it may have adversely affected one of its risk factors. A year or so later one may read headlines that report “Coffee drinking does not cause heart disease” because a more recent individual study did not find an association between coffee use and serum cholesterol levels. Is it no wonder consumers are often confused about nutrition and its effects on health or sport performance? Wellman and others note that nutrition scientists should be more involved in helping the media accurately convey diet and health messages. For the purpose of improving public understanding, the National Cancer Institute provided for journalists and others in the communications business some guidelines for reporting health-related nutrition research. Key points included the quality and credibility of the study; peer-reviewed study or presentation at a meeting; comparison of findings to other studies; funding sources; and putting findings in context, such as risk/benefit trade-offs. As an example of the latter point, some behavior may increase a health risk from one in a million to three in a million; if reported as a three-fold increase in risk, it may appear to be more unhealthful than it really is. Although these guidelines were presented more than 10 years ago their use by the media does not appear to have increased appreciably.

What is the basis for the dietary recommendations presented in this book? Scientists consider each single study as only one piece of the puzzle in attempting to find the truth. To evaluate the effects of nutritional strategies or dietary supplements on health or sport performance, individual studies need to be repeated by other scientists and, if possible, a consensus developed. Reviews and meta-analyses provide a stronger foundation than the results of an individual study. In reviews, an investigator analyzes most or all of the research on a particular topic, and usually offers a summarization and conclusion. However, the conclusion may be influenced by the studies reviewed or by the reviewer’s orientation. There have been instances in which different reviewers evaluated the same studies and came up with diametrically opposed conclusions. Meta-analysis, a review process that involves a statistical analysis of previously published studies, may actually provide a quantification and the strongest evidence available relative to the effect of nutritional strategies or dietary supplements on health or sport performance. The value of reviews and meta-analyses is based on the quantity and quality of studies reviewed. If the number of studies is limited and they are not well controlled, or if improper procedures are used in analyzing and comparing the findings of each study, the conclusions may be inaccurate. Nevertheless, well-designed reviews and, in particular, meta-analyses provide us with valuable data to make prudent decisions. In particular, position statements and position stands of various groups, such as the American College of Sports Medicine and the American Dietetic Association, are developed using an evidence-based approach, which includes an evaluation of the quality of the studies reviewed. Such groups normally use only RCTs to support their position on specific topics. A number of such positions are cited throughout the text where relevant. Within the lifetime of many students a tremendous amount of both epidemiological and experimental research has been concerned with the effect nutrition may have upon health and athletic www.mhhe.com/williams9

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performance. Based on evolving research findings, dietary recommendations change over time. For example, in a twenty-fifth anniversary issue, Environmental Nutrition compared 10 different dietary recommendations based on current research and that available 25 years ago. Here is one of the ten: Then, fat was at the root of most illnesses, including heart disease and cancer, and there was no distinction between different types of fat. Now, fat is in good favor if amounts are moderate, and unsaturated fats, especially monounsaturated, when substituted for saturated fats may even help reduce the risk of some chronic diseases. Comparable to the science of other human behaviors, the science of human exercise and nutrition is not, as many may believe, exact. Although in many cases we still do not have absolute proof that a particular nutritional practice will produce the desired effect, we do have sufficient information to make a recommendation that is prudent, meaning that it is likely to do some good and cause no harm. Thus, the recommendations offered in this text should be considered prudent; they are based upon a careful analysis and evaluation of the available scientific literature, primarily comprehensive reviews and meta-analyses of the pertinent research by various scientists or public and private health or sports organizations. In cases where the research data are limited, recommendations may be based on several individual studies if they have been well designed.

ogy, diets may one day be individualized to conform to our genetically determined favorable responses to particular dietary strategies. Thus, recommendations offered in this text should not be regarded as medical advice. Individuals should consult a physician or another appropriate health professional for advice on taking any dietary supplement for health purposes. Additionally, although information presented in this book may help athletes make informed decisions regarding the use of nutritional strategies as a means to improve sport performance, athletes should confer with an appropriate health professional before using dietary supplements or nutritional ergogenics.

Ke y C o n c e p t s 䉴 Epidemiological research helps to identify relationships between

nutritional practice and health or sport performance and may be helpful in developing hypotheses for experimental research. However, experimental studies such as randomized controlled trials (RCTs) are needed to establish a cause-effect relationship. Such experimental studies should adhere to appropriate research design protocols. 䉴 Prudent nutritional recommendations for enhancement of health or athletic performance are based on reputable evidencebased research.

How does all this relate to me? Remember that we all possess biological individuality and thus might react differently to a particular nutritional intervention. For example, relative to health, most of us have little or no reaction to an increase in dietary salt, but some individuals are very sensitive to salt intake and will experience a significant rise in blood pressure with increased dietary salt. Relative to athletic performance, some, but not all, individuals experience gastrointestinal distress when they ingest certain forms of carbohydrate before performing. Such individual reactions have been noted in some research studies, and are discussed where relevant in the following chapters. With advances in genetic technol-

A P P L I C AT I O N Rate and score your diet by completing the quiz on the next several pages. Keep these results until the end of the course and retake the quizzes to see if your dietary practices have changed.

Instructions These 39 questions will give you a rough sketch of your typical eating habits. The (+) or (–) number for each answer instantly pats you on the back for good eating habits or alerts you to problems you didn’t even know you had. 28

C h e c k f o r Yo u r s e l f Obtain a scientific article from your library that involves the use of a dietary supplement to improve some facet of sport performance.To get a list of studies, you may go to www.pubmed.gov, and type in the name of the supplement and the term “exercise” in the search column, or simply scan some sports medicine journals in your library. Compare the methodology to the recommended criteria presented on page 26.

E X E R C I S E S The quiz focuses on fat, saturated fat, cholesterol, sodium, sugar, fiber, and fruits and vegetables, It doesn’t attempt to cover everything in your diet. Also, it doesn’t try to measure precisely how much of the key nutrients you eat. Next to each answer is a number with a + or – sign in front of it. Circle the number that corresponds to the answer you choose. That’s your score for the question. If two or more answers apply, circle each one. Then average them to get your score for the question.

C H A P T E R 1 Introduction to Nutrition for Health, Fitness, and Sports Performance

How to average. In answering question 19, for example, if your sandwich-eating is equally divided among tuna salad (–2), roast beef (+1), and turkey breast (+3), add the three scores (which gives you +2) and then divide by three. That gives you a score of +2/3 for the question. Round it to +1. Pay attention to serving sizes, which we give when needed. For example, a serving of vegetables is 1/2 cup. If you usually eat one cup of vegetables at a time, count it as two servings.

The Quiz Fruits,Vegetables, Grains, and Beans 1. How many servings of fruit or 100% fruit juice do you eat per day? (OMIT fruit snacks like Fruit Roll-Ups and fruit-on-thebottom yogurt. One serving = one piece or 1/2 cup of fruit or 6 oz. of fruit juice.) (a) 0 –3 (d) 2 +1 (b) less than 1 –2 (e) 3 +2 (c) 1 0 (f) 4 or more +3 2. How many servings of non-fried vegetables do you eat per day? (One serving = 1/2 cup. INCLUDE potatoes.) (a) 0 –3 (d) 2 +1 (b) less than 1 –2 (e) 3 +2 (c) 1 0 (f) 4 or more +3 3. How many servings of vitamin-rich vegetables do you eat per week? (One serving = 1/2 cup. Count ONLY broccoli, Brussels sprouts, carrots, collards, kale, red pepper, spinach, sweet potatoes, or winter squash.) (a) 0 –3 (c) 4 to 6 +2 (b) 1 to 3 +1 (d) 7 or more +3 4. How many servings of leafy green vegetables do you eat per week? (One serving = 1/2 cup cooked or 1 cup raw. Count ONLY collards, kale, mustard greens, romaine lettuce, spinach, or Swiss chard.) (a) 0 –3 (d) 3 to 4 +2 (b) less than 1 –2 (e) 5 or more +3 (c) 1 to 2 +1 5. How many times per week does your lunch or dinner contain grains, vegetables, or beans, but little or no meat, poultry, fish, eggs, or cheese? (a) 0 –1 (c) 3 to 4 +2 (b) 1 to 2 +1 (d) 5 or more +3 6. How many times per week do you eat beans, split peas, or lentils? (OMIT green beans.) (a) 0 –3 (d) 2 +1 (b) less than 1 –1 (e) 3 +2 (c) 1 0 (f) 4 or more +3 7. How many servings of grains do you eat per day? (One serving = 1 slice of bread, 1 oz. of crackers, 1 large pancake, 1 cup pasta or cold cereal, or 1/2 cup granola, cooked cereal, rice, or bulgur. OMIT heavily sweetened cold cereals.) (a) 0 –3 (d) 5 to 7 +2 (b) 1 to 2 0 (e) 8 or more +3 (c) 3 to 4 +1 8. What type of bread, rolls, etc., do you eat? (a) 100% whole wheat as the only flour +3

(b) whole wheat flour as the 1st or 2nd flour +2 (c) rye, pumpernickel, or oatmeal +1 (d) white, French, or Italian 0 9. What kind of breakfast cereal do you eat? (a) whole-grain (like oatmeal or Wheaties) +3 (b) low-fiber (like Cream of Wheat or Corn Flakes) 0 (c) sugary low-fiber (like Frosted Flakes) or low-fat granola –1 (d) regular granola –2

Meat, Poultry, and Seafood 10. How many times per week do you eat highfat red meats (hamburgers, pork chops, ribs, hot dogs, pot roast, sausage, bologna, steaks other than round steak, etc.)? (a) 0 +3 (d) 2 –2 (b) less than 1 +2 (e) 3 –3 (c) 1 –1 (f) 4 or more –4 11. How many times per week do you eat lean red meats (hot dogs, or luncheon meats with no more than 2 grams of fat per serving, round steak, or pork tenderloin)? (a) 0 +3 (d) 2–3 –1 (b) less than 1 +1 (e) 4–5 –2 (c) 1 0 (f) 6 or more –3 12. After cooking, how large is the serving of red meat you eat? (To convert from raw to cooked, reduce by 25%. For example, 4 oz. of raw meat shrinks to 3 oz. after cooking. There are 16 oz. in a pound.) (a) 6 oz. or more –3 (b) 4 to 5 oz. –2 (c) 3 oz. or less 0 (d) don’t eat red meat +3 13. If you eat red meat, do you trim the visible fat when you cook or eat it? (a) yes +1 (b) no –3 14. What kind of ground meat or poultry do you eat? (a) regular ground beef –4 (b) ground beef that’s 11% to 25% fat –3 (c) ground chicken or 10% fat ground beef –2 (d) ground turkey –1 (e) ground turkey breast +3 (f) don’t eat ground meat or poultry +3 15. What chicken parts do you eat? (a) breast +3 (d) wing –2 (b) drumstick +1 (e) don’t eat (c) thigh –1 poultry +3 16. If you eat poultry, do you remove the skin before eating? (a) yes +2 (b) no –3

17. If you eat seafood, how many times per week? (OMIT deep-fried foods, tuna packed in oil, and mayonnaise-laden tuna salad—low-fat mayo is okay.) (a) less than 1 0 (c) 2 +2 (b) 1 +1 (d) 3 or more +3 Mixed Foods 18. What is your most typical breakfast? (SUBTRACT an extra 3 points if you also eat sausage.) (a) biscuit sandwich or croissant sandwich –4 (b) croissant, Danish, or doughnut –3 (c) eggs –3 (d) pancakes, French toast, or waffles –1 (e) cereal, toast, or bagel (no cream cheese) +3 (f) low-fat yogurt or low-fat cottage cheese +3 (g) don’t eat breakfast 0 19. What sandwich fillings do you eat? (a) regular luncheon meat, cheese, or egg salad –3 (b) tuna or chicken salad or ham –2 (c) peanut butter 0 (d) roast beef +1 (e) low-fat luncheon meat +1 (f) tuna or chicken salad made with fat-free mayo +3 (g) turkey breast or hummus +3 20. What do you order on your pizza? (Subtract 1 point if you order extra cheese, cheesefilled crust, or more than one meat topping.) (a) no cheese with at least one vegetable topping +3 (b) cheese with at least one vegetable topping –1 (c) cheese –2 (d) cheese with one meat topping –3 (e) don’t eat pizza +3 21. What do you put on your pasta? (ADD one point if you also add sautéed vegetables.) (a) tomato sauce or red clam sauce +3 (b) meat sauce or meat balls –1 (c) pesto or another oily sauce –3 (d) Alfredo or another creamy sauce –4 22. How many times per week do you eat deep-fried foods (fish, chicken, french fries, potato chips, etc.)? (a) 0 +3 (d) 3 –2 (b) 1 0 (e) 4 or more –3 (c) 2 –1 23. At a salad bar, what do you choose? (a) nothing, lemon, or vinegar +3 (b) fat-free dressing +2

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(c) (d) (e) (f)

24.

25.

26.

27.

low- or reduced-Calorie dressing +1 oil and vinegar –1 regular dressing –2 cole slaw, pasta salad, or potato salad –2 (g) cheese or eggs –3 How many times per week do you eat canned or dried soups or frozen dinners? (OMIT lower-sodium, low-fat ones.) (a) 0 +3 (d) 3 to 4 –2 (b) 1 0 (e) 5 or more –3 (c) 2 –1 How many servings of low-fat calcium-rich food do you eat per day? (One serving = 2/3 cup low-fat or nonfat milk or yogurt, 1 oz. low-fat cheese, 1 1/2 oz. sardines, 3 1/2 oz. canned salmon with bones, 1 oz. tofu made with calcium sulfate, 1 cup collards or kale, or 200 mg. of a calcium supplement.) (a) 0 –3 (d) 2 +2 (b) less than 1 –1 (e) 3 or more +3 (c) 1 +1 How many times per week do you eat cheese? (INCLUDE pizza, cheeseburgers, lasagna, tacos or nachos with cheese, etc. OMIT foods made with low-fat cheese.) (a) 0 +3 (d) 3 –2 (b) 1 +1 (e) 4 or more –3 (c) 2 –1 How many egg yolks do you eat per week? (ADD 1 yolk for every slice of quiche you eat.) (a) 0 +3 (d) 3 –1 (b) 1 +1 (e) 4 –2 (c) 2 0 (f) 5 or more –3

Fats and Oils 28. What do you put on your bread, toast, bagel, or English muffin? (a) stick butter or cream cheese –4 (b) stick margarine or whipped butter –3 (c) regular tub margarine –2 (d) light tub margarine or whipped light butter –1 (e) jam, fat-free margarine, or fat-free cream cheese 0 (f) nothing +3 29. What do you spread on your sandwiches? (a) mayonnaise –2 (b) light mayonnaise –1 (c) catsup, mustard, or fat-free mayonnaise +1 (d) nothing +2

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30. With what do you make tuna salad, pasta salad, chicken salad, etc? (a) mayonnaise –2 (b) light mayonnaise –1 (c) fat-free mayonnaise 0 (d) low-fat yogurt +2 31. What do you use to sauté vegetables or other foods? (Vegetable oil includes safflower, corn, sunflower, and soybean.) (a) butter or lard –3 (b) margarine –2 (c) vegetable oil or light margarine –1 (d) olive or canola oil +1 (e) broth +2 (f) cooking spray +3 Beverages 32. What do you drink on a typical day? (a) water or club soda +3 (b) caffeine-free coffee or tea 0 (c) diet soda –1 (d) coffee or tea (up to 4 a day) –1 (e) regular soda (up to 2 a day) –2 (f) regular soda (3 or more a day) –3 (g) coffee or tea (5 or more a day) –3 33. What kind of “fruit” beverage do you drink? (a) orange, grapefruit, prune, or pineapple juice +3 (b) apple, grape, or pear juice +1 (c) cranberry juice blend or cocktail 0 (d) fruit “drink,” “ade,” or “punch” –3 34. What kind of milk do you drink? (a) whole –3 (c) 1% low-fat +2 (b) 2% fat –1 (d) skim +3 Desserts and Snacks 35. What do you eat as a snack? (a) fruits or vegetables +3 (b) low-fat yogurt +2 (c) low-fat crackers +1 (d) cookies or fried chips –2 (e) nuts or granola bar –2 (f) candy bar or pastry –3 36. Which of the following “salty” snacks do you eat? (a) potato chips, corn chips, or popcorn –3 (b) tortilla chips –2 (c) salted pretzels or light microwave popcorn –1 (d) unsalted pretzels +2 (e) baked tortilla or potato chips or homemade air-popped popcorn +3 (f) don’t eat salty snacks +3

C H A P T E R 1 Introduction to Nutrition for Health, Fitness, and Sports Performance

37. What kind of cookies do you eat? (a) fat-free cookies +2 (b) graham crackers or reduced-fat cookies +1 (c) oatmeal cookies –1 (d) sandwich cookies (like Oreos) –2 (e) chocolate coated, chocolate chip, or peanut butter –3 (f) don’t eat cookies +3 38. What kind of cake or pastry do you eat? (a) cheesecake –4 (b) pie or doughnuts –3 (c) cake with frosting –2 (d) cake without frosting –1 (e) muffins 0 (f) angelfood, fat-free cake, or fat-free pastry +1 (g) don’t eat cakes or pastries +3 39. What kind of frozen dessert do you eat? (SUBTRACT 1 point for each of the following toppings: hot fudge, nuts, or chocolate candy bars or pieces.) (a) gourmet ice cream –4 (b) regular ice cream –3 (c) frozen yogurt or light ice cream –1 (d) sorbet, sherbet, or ices –1 (e) non-fat frozen yogurt or fat-free ice cream +1 (f) don’t eat frozen desserts +3

Scoring Your Diet Add your score for each question.

Score 0 or below

We don’t staple Nutrition Action shut, you know. 1 to 29 Hmmm. Don’t be discouraged. This eating business is tough. 30 to 59 Yesss! Congratulations. You can invite us over to eat any day. 60 or above C-o-o-o-l. Our photographer should be at your door any second. Oops!

Copyright 1996. CSPI. Adapted from Nutrition Action Healthletter (1875 Connecticut Ave., N. W., Suite 300, Washington DC 20009-5728. $24.00 for 10 issues).

Review Questions—Multiple Choice 5. Poor nutrition may contribute to the development of numerous chronic diseases. For example, obesity, high blood pressure, diabetes, and heart disease are most associated with which of the following nutritional problems? (a) diets rich in vitamins and minerals (b) diets rich in dietary fiber (c) diets rich in fat and Calories (d) diets rich in complex carbohydrates (e) diets rich in plant proteins 6. Which group of athletes are most likely to suffer from nutritional inadequacies? (a) male baseball players (b) female gymnasts (c) male tennis players (d) female basketball players (e) male football players 7. Based on recent recommendations of the American College of Sports Medicine and the American Heart Association relative to exercise and health benefits for adults, which of the following statements is false? (a) Moderate-intensity aerobic exercise should be done for a minimum of 30 minutes daily on 5 days each week. (b) Vigorous-intensity exercise may be done for a minimum of 20 minutes on 3 days each week. (c) Each daily exercise bout of aerobic exercise may be done continuously or in smaller segments, such as three 10-minute bouts. (d) In general, more is better as exceeding the minimum recommended amounts of exercise may provide additional health benefits. (e) Resistance exercise, including exercises for the major muscle groups in the body, is recommended at least 5, and preferably 7, days per week.

8. Which of the following statements regarding ergogenic aids is false? (a) They are designed to enhance sports performance. (b) Use of any aid that enhances sport performance is illegal and is grounds for disqualification. (c) Although most nutritional ergogenics are safe, some dietary supplements pose significant health risks. (d) Endorsement of a nutritional ergogenic by a professional athlete does not necessarily mean that it is effective as advertised. (e) Some nutritional supplements marketed as ergogenics may contain prohibited drugs. 9. In an experimental study to evaluate the effect of creatine supplementation on muscular power for sport, which of the following would not be considered acceptable for the research methodology to be followed in the conduct of the study? (a) Use well-trained power sport athletes. (b) Use a double-blind protocol. (c) Use a placebo control group. (d) Use a sport-related performance task. (e) Use males in one group and females in the other. 10. A meta-analysis is (a) an ergogenic aid for mathematicians. (b) a technique to evaluate the presence of drug metabolites in athletes. (c) a statistical evaluation of a collection of studies in order to derive a conclusion. (d) an evaluation of the daily metabolic rate. (e) an analytical technique to evaluate biomechanics in athletes. Answers to multiple choice questions: 1. c; 2. c; 3. d; 4. c; 5. c; 6. b; 7. a; 8. b; 9. e; 10. c.

1. Which of the following would not be regarded as unstructured physical activity, sometimes referred to as activities of daily living? (a) gardening (b) housework (c) jogging (d) leisurely walking (e) driving the car 2. Which basic principle of exercise training is associated with the concept that cardiovascular-respiratory training will enhance adaptations primarily in the heart whereas resistance training will enhance adaptations primarily in the skeletal muscles? (a) overuse (b) overload (c) specificity (d) progression (e) reversibility 3. Increased levels of both aerobic and musculoskeletal fitness through physical activity may produce numerous health benefits. Which of the following is least likely to occur from a combined aerobic and resistance exercise training program? (a) prevention of heart disease (b) building of bone density (c) prevention of weight gain (d) prevention of type 1 diabetes (e) improvement of life expectancy 4. Which of the following is not a recommended dietary guideline associated with the Prudent Healthy Diet? (a) Maintain a healthy body weight. (b) Eat a variety of wholesome, natural foods. (c) Choose a diet with plenty of simple, refined carbohydrates. (d) Abstain from alcohol if you are pregnant. (e) Choose a diet low in saturated fat.

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Review Questions—Essay 1. Describe the possible mechanisms whereby exercise may enhance health status, and list at least eight of the potential health benefits of a regular, comprehensive exercise program. 2. Name and describe the various principles of exercise.

3. Define the term sports nutrition and explain how appropriate eating strategies may enhance sports performance. 4. List at least five guideline questions one may use to evaluate advertised claims for nutritional supplements.

5. Differentiate between epidemiological research and experimental research, discussing the protocols used in each and the pros and cons of each.

References Books American Institute of Cancer Research. 2007. Food, Nutrition, Physical Activity, and the Prevention of Cancer: A Global Perspective. Washington, DC: AICR. Antonio, J., and Stout, J. 2001. Sports Supplements. Philadelphia: Lippincott Williams & Wilkins. Bahrke, M., and Yesalis, C. 2002. PerformanceEnhancing Substances in Sport and Exercise. Champaign, IL: Human Kinetics. Benardot, D. 2000. Nutrition for the Serious Athlete. Champaign, IL: Human Kinetics. Clark, N. 2003. Nancy Clark’s Sports Nutrition Guidebook: Eating to Fuel Your Active Lifestyle. Champaign, IL: Human Kinetics. Driskell, J., and Wolinsky, I. 2002. Nutritional Assessment of Athletes. Boca Raton, FL: CRC Press. Driskell, J. A. 2000. Sports Nutrition. Boca Raton, FL: CRC Press. Dunford, M. 2006. Sports Nutrition: A Practice Manual for Professionals. Chicago: SCAN and the American Dietetic Association. Duyff, R. 2002. The American Dietetic Association’s Complete Food and Nutrition Guide. New York: Wiley. Institute of Medicine, Food and Nutrition Board. 2002. Dietary Reference Intakes for Energy, Carbohydrates, Fiber, Fat, Protein and Amino Acids (Macronutrients). Washington, DC: National Academy Press. Ivy, J., and Portman, R. 2004. Nutrient Timing: The Future of Sports Nutrition. North Bergen, NJ: Basic Health Publications. Jeukendrup, A., and Gleeson, M. 2004. Sport Nutrition. Champaign, IL: Human Kinetics. Kreider, R. B., et al. (eds.) 2009. Exercise & Sport Nutrition: Principles, Promises, Science & Recommendations. Santa Barbara: Fitness Technologies Press. Lightsey, D. 2006. Muscle, Speed, and Lies: What the Sports Supplement Industry Does Not Want Athletes or Consumers to Know. Guilford, CT: Globe Pequot Press. Manore, M., and Thompson, J. 2000. Sport Nutrition for Health and Performance. Champaign, IL: Human Kinetics. Maughan, R. J. 2000. Nutrition in Sport. Oxford: Blackwell Science. McArdle, W. D., et al. 2005. Sports and Exercise Nutrition. Baltimore: Lippincott Williams & Wilkins.

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Mooren, F., and Völker, K. 2005. Molecular and Cellular Exercise Physiology. Champaign, IL: Human Kinetics. National Academy of Sciences. 1999. Dietary Reference Intakes. Washington, DC: National Academy Press. National Institutes of Health. 2002. The Interaction of Physical Activity and Nutrition: Biological Remodeling and Plasticity. Bethesda, MD: NIH. Rippe, J. M. 1999. Lifestyle Medicine. Boston: Blackwell Science. Shils, M., et al. 2006. Modern Nutrition in Health and Disease. Philadelphia: Lippincott Williams & Wilkins. United States Anti-Doping Agency. 2005. Optimal Dietary Intake. Colorado Springs, CO: USADA. U.S. Department of Agriculture and U.S. Department of Health and Human Services. 2005. Nutrition and Your Health: Dietary Guidelines for Americans. Washington, DC: U.S. Government Printing Office. U.S. Department of Health and Human Services. Public Health Service. 1996. The Surgeon General’s Report on Physical Activity and Health. Washington, DC: U.S. Government Printing Office. U.S. Department of Health and Human Services. 2000. Healthy People 2010. Washington, DC: U.S. Government Printing Office. Voy, R. 1991. Drugs, Sports, and Politics. Champaign, IL: Leisure Press. Wardlaw, G., and Hampf, J. 2007. Perspectives in Nutrition. Boston: McGraw-Hill. Wolinsky, I., and Driskell, J. 2004. Nutritional Ergogenic Aids. Boca Raton, FL: CRC Press.

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C H A P T E R 1 Introduction to Nutrition for Health, Fitness, and Sports Performance

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Cordain, L., et al. 2005. Origins and evolution of the Western diet: Healthy implications for the 21st century. American Journal of Clinical Nutrition 81:341–54. Cotman, C., et al. 2005. Exercise and the brain. In Molecular and Cellular Exercise Physiology, eds. F. Mooren and K. Völker. Champaign, IL: Human Kinetics. Daly, R., et al. 2002. Does training affect growth? The Physician and Sportsmedicine 30 (10):21–29. Dancho, C., and Manore, M. 2001. Dietary supplement information on the World Wide Web. ACSM’s Health & Fitness Journal 5 (6):7–12. DeMarini, D. M. 1998. Dietary interventions and human carcinogenesis. Mutation Research 400:457–65. Durnin, J.V. 1967. The influence of nutrition. Canadian Medical Association Journal 96:715–20. Engels, H. J. 1999. Publication of adverse events in exercise studies involving nutritional agents. International Journal of Sport Nutrition 9:89–91. Environmental Nutrition Editors. 2002. Celebrating 25 years of Environmental Nutrition: What we believed then, what we think we know now. Environmental Nutrition 25 (1):8. Febbraio, M., and Pedersen, B. 2005. Contractioninduced myokine production and release: Is skeletal muscle an endocrine organ? Exercise and Sport Sciences Reviews 33:114–19. Franco, O., et al. 2005. Effects of physical activity on life expectancy with cardiovascular disease. Archives of Internal Medicine 165:2355–60. Friedenreich, C., and Orenstein, M. 2002. Physical activity and cancer prevention: Etiologic evidence and biological mechanisms. Journal of Nutrition 132:3456S–64S. Futterman, L., and Lemberg, L. 2001. The mysteries of the human genome uncovered: Medicine is changed forever. American Journal of Critical Care 10:125–32. Grunewald, K., and Bailey, R. 1993. Commercially marketed supplements for bodybuilding athletes. Sports Medicine 15:90–103. Hagberg, J., et al. 2001. Specific genetic markers of endurance performance and VO2 max. Exercise & Sport Sciences Reviews 29:15–19. Haskell, W., et al. 2007. Physical activity and public health: Updated recommendation for adults from the American College of Sports Medicine and the American Heart Association. Medicine & Science in Sports & Exercise 39:1423–34. Hill, A. 2002. Developmental issues in attitudes to food and diet. Proceedings of the Nutrition Society 61:259–66. Horowitz, J. 2007. Exercise-induced alterations in muscle lipid metabolism improve insulin sensitivity. Exercise and Sport Sciences Reviews 35:192–96. Hu, G., et al. 2007. Epidemiological studies of exercise in diabetes prevention. Applied Physiology, Nutrition, and Metabolism 32:583–95. Ignarro, L., et al. 2007. Nutrition, physical activity, and cardiovascular disease: An update. Cardiovascular Research 73:326–40. Irwin, M. 2006. Randomized controlled trials of physical activity and breast cancer prevention. Exercise and Sport Sciences Reviews 34:182–93. Jakicic, J., and Otto, A. 2006. Treatment and preven-

tion of obesity: What is the role of exercise? Nutrition Reviews 64:S57–61. Jeon, C., et al. 2007. Physical activity of moderate intensity and risk of type 2 diabetes: A systematic review. Diabetes Care 30:744–52. Jeukendrup, A., and Martin, J. 2001. Improving cycling performance: How should we spend our time and money. Sports Medicine 31:559–69. Joyner, M., and Coyle, E. 2008. Endurance exercise performance: The physiology of champions. Journal of Physiology 586:35–44. Kearney, J. 1996. Training the Olympic athlete. Scientific American 274 (June):52–63. Keating, X., et al. 2005. A meta-analysis of college students’ physical activity behaviors. Journal of American College Health 54:116–25. Kell, R., et al. 2001. Musculoskeletal fitness, health outcomes and quality of life. Sports Medicine 31:863–73. Khan, N., et al. 2007. The 2007 Canadian Hypertension Education Program recommendations for the management of hypertension: Part 2—therapy. Canadian Journal of Cardiology 23:539–50. Kreider, R. B., et al. (eds.) 2009. Exercise & Sport Nutrition: Principles, Promises, Science & Recommendations. Santa Barbara: Fitness Technologies Press. Kuchment, A. 2007. On your marks . . . Newsweek 156 (13):56–59. Kushi, L., et al. 2006. American Cancer Society Guidelines on Nutrition and Physical Activity for cancer prevention: Reducing the risk of cancer with healthy food choices and physical activity. CA Cancer Journal for Clinicians 56:254–81. Lakka, T., and Laaksonen, D. 2007. Physical activity in prevention and treatment of the metabolic syndrome. Applied Physiology, Nutrition and Metabolism 32:76–88. LaRosa, J. C. 1998. The role of diet and exercise in the statin era. Progress in Cardiovascular Diseases 41:137–50. Lawrence, M., and Kirby, D. 2002. Nutrition and sports supplements: Fact or fiction. Journal of Clinical Gastroenterology 35:299–306. LeLorier, J., et al. 1997. Discrepancies between metaanalyses and subsequent large, randomized, controlled trials. New England Journal of Medicine 337:559–61. Liebman, B. 2007. Staying sharp. Nutrition Action Health Letter 34 (5):1, 3–7. Liebman, B. 2005. While you wait: The cost of inactivity. Nutrition Action Health Letter 32 (10):1–6. Liebman, B., and Schardt, D. 2006. The changing American diet. Nutrition Action Health Letter 33 (3):8–9. MacArthur, D., and North, K. 2007. ACTN3: A genetic influence on muscle function and athletic performance. Exercise and Sport Sciences Reviews 35:30–34. Manore, M. 2004. Nutrition and physical activity: Fueling the active individual. President’s Council on Physical Fitness and Sports Research Digest 5(1):1–8. Maughan, R., et al. 2004. Dietary supplements. Journal of Sports Sciences 22:95–113. Maughan, R. 2002. The athlete’s diet: Nutritional goals and dietary strategies. Proceedings of the Nutrition Society 61:87–96. Meadows, M. 2005. Genomics and personalized medicine. FDA Consumer 39(6):12–17. Melzer, K., et al. 2004. Physical activity: The health benefits outweigh the risks. Current Opinion in Clinical Nutrition and Metabolic Care 7:641–47.

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Mooren, F., et al. 2005. Inter- and intracellular signaling. In Molecular and Cellular Exercise Physiology, eds. F. Mooren and K. Völker. Champaign, IL: Human Kinetics. Mosca, L. 2007. Evidence-based recommendations for cardiovascular disease prevention in women. 2007 Update. Circulation 115:1481–501. National Cancer Institute. 1998. Commentary: Improving Public Understanding: Guidelines for communicating emerging science on nutrition, food safety, and health. Journal of National Cancer Institute 90 (3): 194–99. National Institutes of Health. 2006. National Institutes of Health State-of-the-Science conference statement: Multivitamin/mineral supplements and chronic disease prevention. Annals of Internal Medicine 145:364–71. Nelson, M., et al. 2007. Physical activity and public health in older adults: Recommendation from the American College of Sports Medicine and the American Heart Association. Medicine & Science in Sports & Exercise 39:1435–45. Nieman, D. 2000. Is infection risk linked to exercise workload? Medicine & Science in Sports & Exercise 32:S406–11. Oguma, Y., and Shinoda-Tagawa, T. 2004. Physical activity decreases cardiovascular disease risk in women: Review and meta-analysis. American Journal of Preventive Medicine 26:407–18. Østergård, T., et al. 2007. The effect of exercise, training, and inactivity on insulin sensitivity in diabetics and their relatives: What is new? Applied Physiology, Nutrition, and Metabolism 32:541–48. Pollock, M. L., and Evans, W. J. 1999. Resistance training for health and disease; Introduction. Medicine & Science in Sports & Exercise 31:10–11. Rankinen, T., et al. 2006. The human gene map for performance and health-related fitness phenotypes: the 2005 update. Medicine & Science in Sports & Exercise 38:1863–88. Roberts, C., and Barnard, R. 2005. Effects of exercise and diet on chronic disease. Journal of Applied Physiology 98:3–30. Rogers, C., et al. 2008. Physical activity and cancer prevention: Pathways and targets for intervention. Sports Medicine 38:271–96. Short, S. 1994. Surveys of dietary intake and nutrition knowledge of athletes and their coaches. In Nutrition in Exercise and Sport, eds. I. Wolinsky and J. Hickson. Boca Raton, FL: CRC Press. Skinner, J. 2001. Do genes determine champions? Sports Science Exchange 14 (4):1–4. Slentz, C., et al. 2007. Modest exercise prevents the progressive disease associated with physical inactivity. Exercise and Sport Sciences Reviews 35:18–23. Spain, C., and Franks, B. D. 2001. Healthy People 2010: Physical activity and fitness. President’s Council on Physical Fitness and Sports Research Digest 3(13):1–16. Spangenburg, E. 2007. Suppressor of cytokine signaling, skeletal muscle, and chronic health conditions: The potential interactions. Exercise and Sport Sciences Reviews 35:156–62. Specker, B., and Vukovich, M. 2007. Evidence for an interaction between exercise and nutrition for improved bone health during growth. Medicine and Sport Science 51:50–63. Temple, N. 2002. Nutrition and disease: Challenges of research design. Nutrition 18:343–47.

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Thompson, P., et al. 2001. The acute versus the chronic response to exercise. Medicine & Science in Sports & Exercise 33:S438–45. Trojan, T., et al. 2007. Exercise and colon cancer: Primary and secondary prevention. Current Sports Medicine Reports 6:120–24. Tufts University. 2008. Moderate exercise can cut stroke risk 40%. Health & Nutrition Letter 26 (1):1–2. Vuori, I. 2001. Health benefits of physical activity with special reference to interaction with diet. Public Health Nutrition 4:517–28. Warburton, D., et al. 2006. Health benefits of physical activity: The evidence. Canadian Medical Association Journal 174:801–9. Webb, L., and Lieberman, P. 2006. Anaphylaxis: A review of 601 cases. Annals of Allergy, Asthma & Immunology 97:39–43. Weinstein, A., and Sesso, H. 2006. Joint effects of physical activity and body weight on diabetes and cardiovascular disease. Exercise and Sport Sciences Reviews 34:10–15. Weissgerber, T., et al. 2006. Exercise in the prevention and treatment of maternal-fetal disease: A review of the literature. Applied Physiology, Nutrition and Metabolism 31:661–74. Wellman, N., et al. 1999. Do we facilitate the scientific process and the development of dietary guidance when findings from single studies are publicized? An American Society for Nutritional Sciences controversy session report. American Journal of Clinical Nutrition 70:802–5. Williams, C. 1998. Diet and sports performance. In Oxford Textbook of Sports Medicine, eds. M. Harries et al. Oxford: Oxford University Press. Williams, M., et al. 2007. Resistance exercise in individuals with and without cardiovascular disease: 2007 update: A scientific statement from the American Heart Association Council on Clinical Cardiology and Council on Nutrition, Physical Activity, and Metabolism. Circulation 116:572–84. Williams, M. H. 2006. Sports Nutrition. In Modern Nutrition in Health and Disease, eds. M. Shils et al. Philadelphia: Lippincott Williams & Wilkins. Williams, M. H., and Branch, J. D. 2000. Ergogenic aids for improved performance. In Exercise and Sport Science, eds. W. E. Garrett and D. T. Kirkendall. Philadelphia: Lippincott Williams & Wilkins.

Specific Studies Beedie, C., et al. 2007. Positive and negative placebo effects resulting from the deceptive administration of an ergogenic aid. International Journal of Sport Nutrition and Exercise Metabolism 17:259–69. Bouchard, C., et al. 2000. Genomic scan for maximal oxygen uptake and its response to training in the HERITAGE family study. Journal of Applied Physiology 88:551–59. Brady, L., et al. 2000. Comparison of children’s dietary intake patterns with US dietary guidelines. British Journal of Nutrition 84:361–7. Colcombe, S., et al. 2006. Aerobic exercise training increases brain volume in aging humans. Journal of Gerontology 61:1166–70. Erdman, K. 2006. Influence of performance level on dietary supplementation in elite Canadian athletes. Medicine & Science in Sports & Exercise 38:348–56. Green, G., et al. 2001. Analysis of over-the-counter

C H A P T E R 1 Introduction to Nutrition for Health, Fitness, and Sports Performance

dietary supplements. Clinical Journal of Sports Medicine 11:254–59. Healey, B., et al. 2002. Do natural health food stores require regulation? New Zealand Medical Journal 115:U165. Hinton, P., et al. 2004. Nutrient intakes and dietary behaviors of male and female collegiate athletes. International Journal of Sport Nutrition and Exercise Metabolism 14:389–405. Ioannidis, J. 2005. Contradicted and initially stronger effects in highly cited clinical research. JAMA 294:218–28. Jacobson, B., et al. 2001. Nutrition practices and knowledge of college varsity athletes: A followup. Journal of Strength and Conditioning Research 15:63–68. Jonnalagadda, S., et al. 2000. Assessment of underreporting of energy intake of elite female gymnasts. International Journal of Sport Nutrition and Exercise Metabolism 10:315–25. Kamber, M., et al. 2001. Nutritional supplements as a source for positive doping cases? International Journal of Sport Nutrition and Exercise Metabolism 11:258–63. Kristiansen, M., et al. 2005. Dietary supplement use by varsity athletes at a Canadian University. International Journal of Sport Nutrition and Exercise Metabolism 15:195–210. Maruti. S., et al. 2008. A prospective study of agespecific physical activity and premenopausal breast cancer. Journal of the National Cancer Institute 100:728–37. Mokdad, A., et al. 2004. Actual causes of death in the United States, 2000. JAMA 291:1238–45. Morrison, L., et al. 2004. Prevalent use of dietary supplements among people who exercise at a commercial gym. International Journal of Sport Nutrition and Exercise Metabolism 14:481–92. Mullins, V., et al. 2001. Nutritional status of U.S. elite female heptathletes during training. International Journal of Sport Nutrition and Exercise Metabolism 11:299–314. Peplonska, B., et al. 2008. Adulthood lifetime physical activity and breast cancer. Epidemiology 19:226–36. Rosenbloom, C. 2002. Nutrition knowledge of collegiate athletes in a Division I National Collegiate Athletic Association institution. Journal of the American Dietetic Association 102:418–20. Sossin, K., et al. 1997. Nutrition beliefs, attitudes, and resource use of high school wrestling coaches. International Journal of Sport Nutrition 7:219–28. Stewart, L., et al. 2007. The influence of exercise training on inflammatory cytokines and C-reactive protein. Medicine & Science in Sports & Exercise 39:1714–19. Tully, M., et al. 2007. Randomised controlled trial of home-based walking program at and below current recommended levels of exercise in sedentary adults. Journal of Epidemiology and Community Health 61:778–83. Ziegler, P., et al. 1999. Nutritional and physiological status of U.S. national figure skaters. International Journal of Sport Nutrition 9:345–60. Zinn, C., et al. 2006. Evaluation of sports nutrition knowledge of New Zealand premier club rugby coaches. International Journal of Sport Nutrition and Exercise Metabolism 16:214–25.

Healthful Nutrition for Fitness and Sport: The Consumer Athlete

K E Y

T E R M S

Acceptable Macronutrient Distribution Range (AMDR) 39 Adequate Intake (AI) 39 chronic training effect 75 complementary proteins 55 Daily Value (DV) 60 Dietary Reference Intake (DRI) 39 dietary supplement 66 essential nutrients 37 Estimated Average Requirement (EAR) 39 Estimated Energy Requirement (EER) 39 food additive 73

CHAPTER TWO L E A R N I N G

O B J E C T I V E S

After studying this chapter, you should be able to: 1. List the six major classes of nutrients that are essential for human nutrition and identify specific nutrients within each class. 2. Explain the development of the DRI and explain the meaning of its various components, including the RDA, AI, AMDR, UL, EER, and EAR. 3. Discuss the concept of the balanced diet as applied to the MyPyramid food guide. 4. Explain the concept of nutrient density and provide an example. 5. Outline the twelve guidelines for healthy eating and provide several examples for each as to how food might be selected or prepared in order to adhere to these guidelines. 6. Describe the various classes of vegetarians, what foods they may consume in their diets, and the potential health benefits. 7. List the nutrients that must be included on a food label and explain how reading food labels may help one consume a healthier diet. 8. Identify the various types of dietary supplements and discuss, in general, the potential benefits and risks associated with taking dietary supplements. 9. Describe how commercial and home food processing may enhance or impair the quality of food we eat. 10. Differentiate among food intolerance, food allergy, and food poisoning regarding causes and consequences of each. 11. Understand how dietary practices as related to training and competition may help optimize sport performance.

food allergy 74 Food Exchange System 43 food intolerance 74 food poisoning 72 functional foods 64 generally recognized as safe (GRAS) 73 irradiation 72 key-nutrient concept 44 lactovegetarians 54 liquid meals 77 macronutrient 37 micronutrient 37 MyPyramid 41 nonessential nutrient 38 nutraceuticals 57 nutrient density 45 nutritional labeling 60 organic foods 70 ovolactovegetarians 54 ovovegetarians 54 pescovegetarians 54 phytochemicals 57 Recommended Dietary Allowance(s) (RDA) 38 semivegetarians 54 sports bars 78 Tolerable Upper Intake Level (UL) 39 vegan 53

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Introduction What you eat can have a significant effect on your health. Hippocrates, the Greek physician known as the father of medicine, recognized the value of nutrition and the power of food to enhance health when he declared that you should let food be your medicine and medicine be your food. As noted in chapter 1, the foods we eat contain various nutrients to sustain life by providing energy, promoting growth and development, and regulating metabolic processes. Basically, healthful nutrition is designed to optimize these life-sustaining properties of nutrients and other substances found in food. As the human race evolved over the aeons, a natural diet of plant and animal foods provided the nutrients necessary to sustain the lives of our hunter/gatherer ancestors. As human civilization developed, however, human food consumption patterns gradually changed as the emerging food industry developed newer and increasingly more technological methods to plant, grow, process, and prepare foods. Overall, modern developments in the food industry have improved food quality and safety, but there are still some practices that are cause for consumer concern. For example, provision of a wide variety of foods has helped to eradicate most nutrientdeficiency diseases in industrialized nations. Conversely, provision of a wide variety of high-fat, high-sugar, highCalorie, low-fiber foods appears to have increased the possibility of the development of various chronic diseases. The three keys to a healthful diet are balance, variety, and moderation. In general, a healthful diet is simply one that provides a balanced proportion of foods from different food groups, a variety of foods from within the different food groups, and moderation in the consumption of any food. Such a diet should provide us with the nutrients we need to sustain life. In this regard, several governmental and professional health organizations have developed dietary

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guidelines to help us obtain the nutrients we need. Additionally, the current major focus of nutrition research, both epidemiological and experimental, is how our diets— and even specific foods or nutrients in our diets—affect our health, primarily as related to the development of chronic diseases. Again, specific dietary guidelines have been recommended as a means to enhance one’s health status, and these recommendations underlie the Prudent Healthy Diet. In essence, the basic premise of the Prudent Healthy Diet is to consume foods in as natural a state as possible, primarily relying on plant foods and a movement toward a vegetarian or semivegetarian diet. Although the basic guidelines underlying the Prudent Healthy Diet are rather simple, selecting the appropriate foods in modern society may be somewhat confusing. Fortunately, nutrition labels should provide the knowledgeable consumer with sufficient information to make intelligent choices and select highquality foods. Food safety is also another consumer concern, and appropriate food selection and preparation practices may help minimize most of the health risks associated with certain foods. Another problem underlying healthy eating is the cost. In a recent report, Tufts University noted that the cost of

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more nutritious foods is climbing. They report that low-Calorie, nutrient-rich fruits and vegetables were far more expensive, Calorie for Calorie, than sweets and snack foods. One researcher noted that fruits and vegetables are rapidly becoming luxury goods. In one survey they reported that energy-dense foods rich in sugar and fat cost an average $1.76 for 1,000 Calories, whereas nutrient-dense foods cost $18.16 per 1,000 Calories, nearly 10 times as much. However, you can reduce the cost of nutrient-dense foods with a little planning, such as the following. • Choose seasonal fruits and vegetables. • Capitalize on store specials on fresh chicken, fish, and low-fat meat. Buy quantities, repackage into smaller portions, and freeze for future use. • Purchase whole grain cereals, rice, and similar products in bulk at warehouse stores. • Buy bags of frozen vegetables, which are cheaper and do not spoil. The Prudent Healthy Diet also serves as the basic diet for those interested in optimal physical performance, although it may be modified somewhat for specific types of athletic endeavors as shall be noted as appropriate throughout the book.

Essential Nutrients and Recommended Nutrient Intakes “You are what you eat” is a popular phrase that contains some truth, particularly in its implications for both health and athletic performance. The foods you eat contain a wide variety of nutrients, both essential and nonessential, as well as other substances that may affect your body functions. These nutrients are synthesized by plants from water, carbon dioxide, and various elements in the soil, and they also become concentrated in animals who consume plant foods. Various nutrients may also be added to foods in the manufacturing process. Careful selection of wholesome, natural foods will provide you with the proper amounts of nutrients to optimize energy sources, to build and repair tissues, and to regulate body processes. However, as we shall see in later chapters, poor food selection with an unbalanced intake of some nutrients may contribute to the development of significant health problems and impair sport performance.

TABLE 2.1

Nutrients essential or probably essential to humans

Carbohydrates Fiber Sugars and starches Fats (essential fatty acids) Linoleic fatty acid Alpha linolenic fatty acid Protein (essential amino acids) Histidine Isoleucine Leucine Lysine Methionine and cysteine

Phenylalanine and tyrosine Threonine Tryptophan Valine

Vitamins

What are essential nutrients? As noted in chapter 1, six classes of nutrients are considered necessary in human nutrition: carbohydrates, fats, proteins, vitamins, minerals, and water. Within most of these general classes (notably protein, vitamins, and minerals) are a number of specific nutrients necessary for life. For example, more than a dozen vitamins are needed for optimal physiological functioning. In relation to nutrition, the term essential nutrients describes nutrients that the body needs but cannot produce at all or cannot produce in adequate quantities. Thus, in general, essential nutrients must be obtained from the food we eat. Essential nutrients also are known as indispensable nutrients. Table 2.1 lists the specific nutrients currently known to be essential or probably essential to humans. Some of the nutrients listed have been shown to be essential for various animals and are theorized to be essential for humans. Curing a nutrient-deficiency disease by a specific nutrient has been the key factor underlying the determination of nutrient essentiality. However, the concept of nutrient essentiality has evolved to include substances that may help prevent the development of chronic diseases. Most recently, the essentiality of choline was included with the B vitamin group, and the list is likely to expand in the future as research reveals health benefits of various plant substances. Some foods, such as whole wheat bread, may contain all six general classes of nutrients, whereas others, such as table sugar, contain only one nutrient class. However, whole wheat bread cannot be considered a complete food because it does not contain a proper balance of all essential nutrients. The human body requires substantial amounts of some nutrients, particularly those that may provide energy and support growth and development of the body tissues, namely carbohydrate, fat, protein, water, and several minerals and electrolytes. These nutrients are referred to as macronutrients because the daily requirement usually is greater than a few grams. Most nutrients that help to regulate metabolic processes, particularly vitamins and

Water soluble

Fat soluble

B1 (thiamin) B2 (riboflavin) Niacin B6 (pyridoxine) Pantothenic acid Folacin B12 (cyanocobalamin) Biotin Choline* C (ascorbic acid)

A (retinol) D (calciferol) E (tocopherol) K

Minerals Major

Trace/Ultratrace

Calcium Chloride Magnesium Phosphorus Potassium Sodium Sulfur

Boron Chromium Cobalt Copper Fluorine Iodine Iron

Manganese Molybdenum Nickel Selenium Silicon Vanadium Zinc

Water *Technically not classified as a vitamin (see chapter 7).

minerals, are needed in much smaller amounts (usually measured in milligrams or micrograms) and are referred to as micronutrients, although as noted in chapter 8, minerals may be classified by other terminology according to the daily requirement. Essential nutrients are necessary for human life. An inadequate intake may lead to disturbed body metabolism, certain disease states, or death. Conversely, an excess of certain nutrients may also disrupt normal metabolism and may even be lethal (see figure 2.1).

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TABLE 2.2

Death Toxic effects

Nonessential nutrients Above UL

Increasing Nutrient Intake

Examples of nonessential nutrients and other substances found in foods

Carnitine Creatine Glycerol Drugs Caffeine Ephedrine

Adequate and safe intake

Within RDA or AI

Phytochemicals Phenols Plant sterols Terpenes Extracts

Below RDA or AI Deficiency diseases

Death

Bee pollen Ginseng Yohimbe Antinutrients Phytates Tannins

FIGURE 2.1 One model of the possible relationship between

nutrient intake and health status. An inadequate intake may lead to nutrient-deficiency diseases, while excessive amounts may cause various toxic reactions. Both deficiencies and excesses may be fatal if carried to extremes. Nutrient intakes within the Recommended Dietary Allowance (RDA) or Adequate Intake (AI) levels are normally adequate and safe, while those below these levels may lead to deficiency diseases. Nutrient intakes above the Tolerable Upper Intake Level (UL) may lead to toxic reactions.

What are nonessential nutrients? Those nutrients found in food but that also may be formed in the body are known as nonessential nutrients, or dispensable nutrients. A good example of a nonessential nutrient is creatine. Although we may obtain creatine from food, the body can also manufacture creatine from several amino acids when necessary. Thus, we need not consume creatine per se, but must consume adequate amounts of the amino acids from which creatine is made. As we shall see later, creatine combined with phosphate is a very important nutrient for energy production during very high intensity exercise. Other than nonessential nutrients, foods contain other nonessential substances that may be involved in various metabolic processes in the body. These substances, sometimes referred to as non-nutrients, include those found naturally in foods and those added either intentionally or inadvertently during the various phases of food production and preparation. Classes of these substances include drugs, phytochemicals, extracts, herbals, food additives, and even antinutrients (substances that may adversely 38

affect nutrient status). Many of these nonessential nutrients and other substances are marketed as a means to enhance health or sports performance. Table 2.2 provides some examples that will be covered later in this text.

How are recommended dietary intakes determined? As noted in table 2.1, humans have an essential requirement for more than forty specific nutrients. A number of countries, as well as the Food and Agriculture and World Health Organizations (FAO/WHO), have estimated the amount of each nutrient that individuals should consume in their diets. In the United States, the recommended amounts of certain of these nutrients have been established by the Food and Nutrition Board, Institute of Medicine, of the National Academy of Sciences. The first set of recommendations, Recommended Dietary Allowances (RDA), was published in 1941 and revised periodically over the years. In general, scientists with considerable knowledge of a specific nutrient would meet to evaluate the totality of scientific data concerning the need for that nutrient in the diet. Based on their analysis, specific dietary intake recommendations were made. In the past the Recommended Dietary Allowances (RDA) were developed to prevent deficiency diseases. For example, the RDA for Vitamin C was set to prevent scurvy. However, more recently scientists have discovered that higher amounts of some nutrients may confer some health benefits in specific population

C H A P T E R 2 Healthful Nutrition for Fitness and Sport: The Consumer Athlete

groups, such as prevention of birth defects by adequate folic acid intake in the early stages of pregnancy and the prevention of various chronic diseases by sufficient intake of nutrients found in fruits and vegetables. Conversely, scientists have also noted that overconsumption of some nutrients may increase health risks. Expert scientists still meet to evaluate the available scientific data that serve as the basis for dietary recommendations, but the basis for such recommendations has been expanded beyond the objective of simply preventing deficiency diseases. The current philosophy relative to the development of recommendations for dietary intake focuses on a continuum of nutrient intake. Several points along this continuum for a specific nutrient may be (1) the amount that prevents a nutrient-deficiency disease, (2) the amount that may reduce the risk of a specific health problem or chronic diseases, and (3) the amount that may increase health risks. Based on this concept, the Food and NutriEARs tion Board, working with Health Canada, is involved in a multiyear project to develop RDAs new standards for nutrient intake, the AIs Dietary Reference Intakes (DRI), for Americans and Canadians. The DRI DRIs replace and expand on the Recommended AMDRs Dietary Allowances (RDA). The DRI is an umbrella term. Allison Yates, director of the Food and Nutrition Board, noted that the EERs DRI consist of various reference intakes: ULs The Recommended Dietary Allowance (RDA) The RDA represents the average daily dietary intake that is sufficient to meet the nutrient requirement of nearly all (97 percent to 98 percent) healthy individuals in a group. The RDA is to be used as a goal for the individual. You may use the RDA to evaluate your intake of a specific nutrient. The RDA term will be used throughout this book as the means to express nutritional adequacy. The Adequate Intake (AI) The AI is a recommended daily intake level based on observed or experimentally determined approximations of nutrient intake by a group of healthy people. When an RDA cannot be set because extensive scientific data are not available, an AI may be established because the limited data available may provide grounds for a reasonable judgment. You may also use the AI to evaluate your intake of a specific nutrient, but remember that it is not as well established as the RDA. The AI term will be used throughout this book as appropriate. The Acceptable Macronutrient Distribution Range (AMDR) The AMDR is defined as a range of intakes for a particular energy source that is associated with reduced risk of chronic disease while providing adequate intakes of essential nutrients. The AMDR is expressed as a percentage of total energy intake and has both an upper and lower level. Individuals consuming below or above this range are at more risk for inappropriate intake of essential nutrients and development of chronic diseases. AMDRs have been set for carbohydrate, fat, and protein. The Tolerable Upper Intake Level (UL) The UL is the highest level of daily nutrient intake that is likely to pose no risks of

adverse health effects to most individuals in the general population. The UL is given to assist in advising individuals what levels of intake may result in adverse effects if habitually exceeded. The UL is not intended to be a recommended dietary intake; you should consider it as a maximum for your daily intake of a specific nutrient on a long-term basis. The UL will be cited throughout this book when data are available. The Estimated Average Requirement (EAR) The EAR represents a nutrient intake value that is estimated to meet the requirement of half the healthy individuals in a group. Conversely, half of the individuals consuming the EAR will not meet their nutrient needs. The EAR is used to establish the RDA. Depending on the data available, the RDA is some multiple of the EAR, mathematically calculated to provide adequate amounts to 97 percent to 98 percent of the general population. When sufficient scientific data are not available to calculate an EAR, then an AI may be provided. Estimated Energy Requirement (EER) The EER is an estimate of the amount of energy needed to sustain requirements for daily physical activity. The EER is covered in detail in chapter 3. Figure 2.1 highlights several of these terms in relation to nutritional deficiency, adequacy, and excess. These terms, and others, are described in detail in the National Academy of Sciences series on Dietary Reference Intakes. Currently, DRI have been established for all classes of essential nutrients, including carbohydrate, fat, protein and amino acids, vitamins, minerals, and water. The new DRI also, for the first time, provide recommendations for those 70 years and older. Tables containing the current DRI may be found on the inside of the front and back covers of this text. The current DRI will be updated, with inclusion of additional substances like phytochemicals, as future research data merits. www.nap.edu You may access the full version of the DRI for specific nutrients free of charge. Click on Special Collections and Dietary Reference Intakes.

The DRI have been developed for several purposes, one of the most important being the assessment of dietary intake and planning diets for individuals and groups. In this context, the DRI for specific nutrients will be provided in the appropriate chapter. However, another term, Daily Value (DV), is used with food labels and may be useful in helping you plan your dietary intake. The DV is discussed later in this chapter. These new standards are designed to ensure adequate nutrition for most individuals in the population. They may also be used to plan diets for individuals with special needs. If individuals in a population consume foods in amounts adequate to meet these standards, there will be very little likelihood of nutritional inadequacy or impairment of health. An individual does not necessarily have a deficient diet if the recommendation for a given nutrient is not received daily. The daily recommendation for any nutrient should average over a five- to eight-day period, so that one may be deficient in iron consumption one day but compensate for this one-day www.mhhe.com/williams9

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deficiency during the remainder of the week. Thus, comparison of our nutrient intake to these standards over a sufficient period may be useful in estimating our risk for deficiency. However, one should realize that only a clinical and biochemical evaluation can reveal an individual’s nutritional status in regard to any specific nutrient. Although the RDA are useful because they state approximately how much of all the essential nutrients we need, they are not designed to inform us as to which specific foods we may need to consume to obtain these nutrients. Other dietary guidelines have been developed to help us select foods that will provide us with the RDA for all essential nutrients.

Ke y C o n c e p t s 䉴 Balance, variety, and moderation are the three keys to a healthful

diet. 䉴 The principal purposes of the nutrients we eat are to provide

energy, build and repair body tissues, and regulate metabolic processes in the body. 䉴 More than forty specific nutrients are essential to life processes. They may be obtained in the diet through consumption of the six major nutrient classes: carbohydrates, fats, proteins, vitamins, minerals, and water. 䉴 The Dietary Reference Intakes (DRI) provide us with a set of standards for our nutritional needs and are being developed with the goal of promoting optimal health.

C h e c k f o r Yo u r s e l f Using the tables on the inside of the front and back covers of the text, list the DRI for yourself, including the RDA, AI, and UL.

The Balanced Diet and Nutrient Density One of the major concepts advanced by nutritionists over the years to teach proper nutrition is that of the balanced diet, stressing variety and moderation. In order to obtain the nutrients that we need, guides to food selection have been developed, establishing various food groups with key nutrients, and in more recent years focusing on the concept of nutrient density.

Milk, yogurt, cheese

Vegetables

Fruits

What is a balanced diet? As noted previously, the human body needs more than forty different nutrients to function properly. The concept of the balanced diet is that by eating a wide variety of foods in moderation you will obtain all the nutrients you need to support growth and development of all tissues, regulate metabolic processes, and provide adequate energy for proper weight control (see figure 2.2). You should obtain the RDA or AI for all essential nutrients and adequate food energy to achieve a healthy body weight. Although everyone’s diet requires the essential nutrients and adequate energy, the proportions differ at different stages of the life cycle. The infant has needs differing from his grandfather, and the pregnant or lactating woman has needs differing from her adolescent daughter. There also are differences between the needs of males and females, particularly in regard to the iron content of the diet. Moreover, individual variations in lifestyle may impose different nutrient requirements. A long-distance runner in training for a marathon has some distinct nutritional needs compared to a sedentary colleague. The individual trying to lose weight needs to balance Calorie losses with nutrient adequacy. The diabetic individual needs strict nutritional counseling for a balanced diet. Thus, there are a number of different conditions that may influence nutrient needs and the concept of a balanced diet. The food supply in the United States is extremely varied, and most individuals who consume a wide variety of foods do receive an adequate supply of nutrients. However, there appears to be some concern that many Americans are not receiving optimal nutrition because they consume excessive amounts of highly processed foods. This may be true, as improper food processing may lead to depletion of key nutrients and the addition of high-Calorie and low-nutrient ingredients, such as fat and sugar. Over half of the Calories that the average American eats are derived from fat and sugar. An unbalanced diet is due not to the unavailability of proper foods but rather to our choice of foods. To improve our nutritional habits we need to learn to select our foods more wisely.

What foods should I eat to obtain the nutrients I need? Although the RDA, AI, and AMDR provide us with information relative to the nutrients we need, they don’t guide us in appropriate food selection. Thus, over the years a number of different edu-

Bread, cereal, rice, pasta

Meat, poultry, fish, dry beans, eggs, nuts

Fats, oils, sweets

F I G U R E 2 . 2 The key to sound nutrition is a balanced diet that is high in nutrients and low in Calories. For balance, select a wide variety of

foods from among and within the food groups in the MyPyramid food guide or the Exchange Lists (appendix E). 40

C H A P T E R 2 Healthful Nutrition for Fitness and Sport: The Consumer Athlete

cational approaches have been used to convey the concept of a balanced diet to help individuals select foods that will provide sufficient amounts of all essential nutrients. In essence, foods with similar nutrient content were grouped into categories. In the past, foods were grouped into the Basic Seven or the Basic Four Food Groups, but today there is some consensus that six general categories of foods may be used to represent the grouping of various nutrients. Although different terminology may be used with various food guides, the six categories are: (1) milk, yogurt, and cheese; (2) meat, poultry, fish, eggs, dry beans, and nuts; (3) bread, cereal, rice, and pasta; (4) vegetables; (5) fruits; and (6) fats, oils, and sweets. Table 2.3 lists some of the major nutrients found in each of these six food categories. One concept of balance focuses on the macronutrients, from which we derive our food energy. Although a RDA for protein had previously been established, the National Academy of Sciences recently released DRI for carbohydrate, fat, and protein as a guide to provide adequate energy but also to help minimize the risk of chronic disease. For adults, the AMDR should be composed of approximately 45–65 percent of carbohydrate, 20–35 percent of fat, and 10–35 percent of protein. Similar percentages are recommended for children, except younger children need a slightly higher percentage of fat. Carbohydrates are found primarily in the bread, cereal, rice, pasta category, the vegetable category, and the fruit category, but also in beans and sweets in other categories. Protein and fats are both found primarily in the milk, yogurt, cheese category, and the meat, poultry, fish, dry beans, eggs, nuts category, while solid fats and added sugars are major components of the fats, oils, sweets category. Two contemporary food guides using a six-level classification system are the MyPyramid and the Food Exchange System.

What is the MyPyramid Food Guide? The most recent government food guide designed to provide sound nutritional advice for daily food selection is the MyPyramid, developed by the United States Department of Agriculture (USDA). MyPyramid represents the 2005 Dietary Guidelines for Americans. Health Canada has developed a similar Eating Well with Canada’s Food Guide, as have many other countries.

TABLE 2.3

www.healthierus.gov/dietaryguidelines Use to access full documentation of the development of the 2005 Dietary Guidelines for Americans.

MyPyramid, Steps to a Healthier You, designed to stress variety, proportionality, and moderation in your diet and the value of physical activity, is presented in figure 2.3. The figure also stresses personalization and gradual improvement in both diet and physical activity. Variety is symbolized by the six color bands, representing the five food groups (orange, green, red, blue, purple) and oils (yellow), illustrating that foods from all groups are needed daily for good health. Although there are six food groups represented in MyPyramid, the USDA does not regard oils as an actual food group; thus, officially there are only five food groups in MyPyramid. Proportionality, or balance, is shown by the different widths of the food group bands. The widths at the base serve as a general guide to how much food a person should choose from each group. Moderation is represented by the narrowing of each food group from bottom to top. Each color band is wider at the base and narrows as it reaches the top of the pyramid. Although implied but not depicted in the pyramid, the wide base for each food group represents those foods which should be consumed more often, while the narrow segment represents those foods which should be eaten less often. For example, in the grain group, whole wheat, high-fiber foods are represented at the base while highly refined grains, those with added sugar and fat, are represented at the top of the pyramid. Activity is represented by the steps and the person climbing them, as a reminder of the importance of daily physical activity. Gradual improvement is encouraged by the slogan, Steps to a Healthier You. It suggests that individuals can benefit from taking small steps to improve their diet and lifestyle each day. Personalization is shown by the person on the steps, the slogan, and the URL MyPyramid.gov. MyPyramid is designed to be simple, yet motivational, with the intent to help individuals make healthier lifestyle choices relative to diet and exercise. Serving sizes for each food group are presented in table 2.4, while key points for healthful eating and physical activity are presented in figure 2.4. One of the key points of MyPyramid is to make changes in your diet and physical activity levels gradually,

Major nutrients found in the six food categories of the MyPyramid food guide

Milk, yogurt, cheese

Meat, poultry, fish, Dry beans, eggs, nuts

Bread, cereal, rice, pasta

Calcium Protein Riboflavin Vitamins A, D

Protein B Vitamins Iron Zinc

B Vitamins Iron Fiber

Vegetables

Fruits

Fats, oils, sweets*

Vitamin A (carotene) Vitamin C Iron Fiber

Vitamin A (carotene) Vitamin C Fiber

Vitamin A Vitamin D Vitamin E

*Mainly contains Calories. Fat-soluble vitamins found in some foods.

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Gradual Improvement Gradual improvement is encouraged by the slogan. It suggests that individuals can benefit from taking small steps to improve their diet and lifestyle each day.

Personalization Personalization is shown by the person on the steps, the slogan, and the Website. Find the kinds and amounts of food to eat each day at MyPyramid.gov.

MyPyramid STEPS TO A HEALTHIER YOU MyPyramid.gov

Activity Activity is represented by the steps and the person climbing them, as a reminder of the importance of daily physical activity.

Proportionality Proportionality is shown by the different widths of the food group bands. The should choose from each group. The widths are just a general guide, not exact proportions. Check the Website for how much is right for you.

Moderation Moderation is represented by the narrowing of each food group from bottom to top. The wider base stands for foods with little or no solid fats or added sugars. These should be selected more often. The narrower top area stands for foods containing more added sugars and solid fats. The more active you are, the more of these foods can fit into your diet. GRAINS

TABLE 2.4

Variety Variety is symbolized by the 6 color bands representing the 5 food groups of the Pyramid and oils. This illustrates that foods from all groups are needed each day for good health.

VEGETABLES

FRUITS

OILS

Serving sizes for the MyPyramid food guide

MyPyramid food group

Serving size

Milk

1 cup of milk or yogurt 1 1/2 ounces natural cheese 2 ounces of processed cheese

Meat

1 ounce of cooked lean meat, poultry, or fish 1/4 cup of cooked dry beans 1 egg 1 tablespoon peanut butter

Grains

1 slice of bread 1 ounce of ready-to-eat cereal 1/2 cup of cooked cereal, rice, or pasta

Vegetable

1 cup of raw, leafy vegetables 1/2 cup of other vegetables, cooked or chopped raw 1 cup vegetable juice

Fruit

1 medium apple, banana, or orange 1 cup of chopped, cooked, or canned fruit 1 cup of fruit juice 1/2 cup dried fruit

Oils (Not an official food group)

1Teaspoon

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MILK

F I G U R E 2 . 3 The new food

guide for Dietary Guidelines for Americans is MyPyramid.The guide contains five food groups, plus oils, and emphasizes the concepts of variety, proportionality, and moderation. Physical activity is incorporated in the design for the first time. Overall, personalization is the key to MyPyramid, and it may be accessed at www.MyPyramid.gov. See text for discussion. Source: U.S. Department of Agriculture/U.S. Department of Health and Human Services.

MEAT & BEANS

or in small steps one at a time. A list of 120 small steps to improve your diet and physical activity is presented in appendix H. The beauty of the new MyPyramid, as the name implies, is its design to individualize dietary recommendations. Here is what you can do when you access the MyPyramid Website. • You are asked to input your age, gender, and activity level. You will be provided with one of 12 dietary patterns, ranging from 1,000 to 3,200 Calories, based on your individual nutrition needs. • You can develop an individualized food plan of the types and amount of foods to suit your dietary preferences and daily caloric needs, including dietary plans for a healthier body weight. • You can print a personalized pyramid to use as a guide for one day or a week, and a worksheet to help you track your progress and choose goals for tomorrow and the future. An example of a 7-day meal plan for 2,000 Calories is presented in appendix I. • You may use MyPyramid Tracker, an excellent dietary assessment tool. MyPyramid Tracker provides a more detailed assessment and analysis of your current eating and physical activity habits, which may be compared to the 2005 Dietary Guidelines recommendations, nutrient intake, and energy balance. • You may use MyPyramid Tracker to track your diet and physical activity history for up to one year. • You may obtain detailed information about each food group and physical activity. For example, for each food group information is provided relative to the foods in that group, and appropriate serving size (accompanied by a food photo gallery to illustrate serving sizes), associated nutrients, and health benefits. • You may obtain information for special populations, such as pregnant women, overweight children and adults, and the elderly. Of particular interest, MyPyramid for Kids presents the first food

C H A P T E R 2 Healthful Nutrition for Fitness and Sport: The Consumer Athlete

Source: United States Department of Agriculture; MyPyramid.gov

F I G U R E 2 . 4 MyPyramid provides guidelines for healthful eating and physical activity.

guide for children age 6–11, which is presented in appendix J. Computer games are designed to promote healthy eating and daily exercise as a means of preventing childhood obesity. • If you are a health professional, you may access materials for educational purposes. Although the MyPyramid figure representing the dietary guidelines has been criticized as being too simple, the Website contains an impressive amount of very useful information. You may also find some helpful information in The Pocket Idiot’s Guide to the New Food Pyramids by Ward. www.MyPyramid.gov Provides an impressive amount of valuable information regarding diet and exercise, personalized for you with the MyPyramid Tracker program.You may also access MyPyramid for Kids at this site. www.healthcanada.org Click on Food and Nutrition to access Eating Well with Canada’s Food Guide.

What is the Food Exchange System? A food guide similar to MyPyramid is the Food Exchange System, a grouping of foods developed by the American Dietetic Association, American Diabetes Association, and other professional and

governmental health organizations. Foods in each of the six exchanges contain similar amounts of Calories, carbohydrate, fat, and protein. As with the MyPyramid food guide, eating a wide variety of foods from the various food exchanges will help guarantee that you receive the RDA for essential nutrients. The basic content of the six primary food exchanges is presented in table 2.5. There are several differences between the food groups in MyPyramid and the Food Exchange Lists. First, the milk exchange list has three levels based on fat content. Second, cheese is found in the meat and meat substitutes exchange list. Third, the meat and meat substitutes exchange list has four levels based on fat content. Fourth, the starch exchange list includes starchy vegetables. And fifth, nuts and seeds are found in the fat exchange list. A detailed list of common foods in the various exchanges may be found in appendix E. The Food Exchange System was developed for diabetics and for weight control. Because it may be an effective means to judge the caloric content of foods during a weight management program, it will be covered in greater detail in chapter 11.

What is the key-nutrient concept for obtaining a balanced diet? As already noted, humans require many diverse nutrients, including twenty amino acids, thirteen vitamins, and more than fifteen

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TABLE 2.5

Carbohydrate, fat, protein, and Calories in the six food exchanges (typical serving sizes)

Food exchange

Carbohydrate

Fat

Protein

Calories

12 12 12

0–3 5 8

8 8 8

90 120 150

0 0 0 0

0–1 3 5 8

7 7 7 7

35 55 75 100

Starch (1 ounce; 1/2 cup)

15

0–1

3

80

Fruit (1 medium; 1/2 cup)

15

0

0

60

Vegetable (1/2 cup)

5

0

2

25

Fat (1 teaspoon)

0

5

0

45

Milk (1 cup) Skim/very low fat Low fat Whole Meat and meat substitutes (1 ounce) Very lean* Lean Medium fat High fat

Carbohydrate, fat, and protein in grams (g) 1 g carbohydrate = 4 Calories 1 g fat = 9 Calories 1 g protein = 4 Calories *Legumes (beans) are meat substitutes, but per ounce have more carbohydrate (~7 grams) and less protein (~2 grams) than very lean meat, fish, or poultry.

minerals. To plan our daily diet to include all of these nutrients would be mind-boggling, so simplified approaches to diet planning have been developed. The nutritional composition of foods varies tremendously. If you wish, you may evaluate the nutrient content of your favorite foods on the MyPyramid Website, or for a more detailed evaluation go to the USDA Website. http://www.ars.usda.gov/ba/bhnrc/ndl Provides a detailed analysis of the nutrient content, over sixty individual nutrients, of various foods.

This site analyzes for nearly 120 nutrients and food components. If you examine a food-composition table, you will quickly see that no two foods are exactly alike in nutrient composition. However, certain foods are similar enough in nutrient content to be grouped accordingly. This fact is the basis for approaching nutrition education by way of the MyPyramid food guide and the Food Exchange Lists. In essence, foods are grouped or listed according to approximate caloric content and nutrients in which they are rich. Eight nutrients are central to human nutrition: protein, thiamin, riboflavin, niacin, vitamins A and C, iron, and calcium (figure 2.5). When found naturally in plant and animal sources, these nutrients are usually accompanied by other essential nutrients. The central theme of the key-nutrient concept is simply that if these eight key nutrients are adequate in your diet, you will probably receive an ample supply of all nutrients essential to humans. It is important to note that in order for the key-nutrient concept to work, you must obtain the nutrients from a wide variety of mini44

F I G U R E 2 . 5 The key-nutrient concept. Obtaining the RDA or

AI for these eight key nutrients from a balanced diet of wholesome, natural foods among the six food exchanges will most likely support your daily needs for all other essential nutrients.

mally processed whole foods. For example, highly processed foods to which some vitamins have been added will not contain all of the trace elements, such as chromium, that were removed during processing. Table 2.6 presents the eight key nutrients and some significant plant and animal sources. You can see that the food groups and food

C H A P T E R 2 Healthful Nutrition for Fitness and Sport: The Consumer Athlete

TABLE 2.6

Eight key nutrients and significant food sources from plants and animals Food group/

Nutrient

RDA or AI M

Plant source

Animal source

Food exchange

Meat, milk

F

Protein

58 g

46 g

Dried beans and peas, nuts

Meat, poultry, fish, cheese, milk

Vitamin A

0.9 mg

0.7 mg

Dark-green leafy vegetables, orange-yellow vegetables, margarine

Butter, fortified milk, liver

Vegetable, fat, meat

Vitamin C

90 mg

75 mg

Citrus fruits, broccoli, potatoes, strawberries, tomatoes, cabbage, dark-green leafy vegetables

Liver

Fruit, vegetable

Thiamin (vitamin B1)

1.2 mg

1.1 mg

Breads, cereals, pasta, nuts

Pork, ham

Grain (starch), meat

Riboflavin (vitamin B2)

1.3 mg

1.1 mg

Breads, cereals, pasta

Milk, cheese, liver

Grain (starch), milk

Niacin

16 mg

14 mg

Breads, cereals, pasta, nuts

Meat, fish, poultry

Grain (starch), meat

Iron

8 mg

18 mg

Dried peas and beans, spinach, asparagus, dried fruits

Meat, liver

Meat, grain (starch)

Calcium

1,000 mg

1,000 mg

Turnip greens, okra, broccoli, spinach, kale

Milk, cheese, sardines, salmon

Milk, meat (fish) vegetable

Recommended Dietary Allowance (RDA) or Adequate Intake (AI) for males (M) and females (F) age 19–50. See inside of text cover for other age groups.

exchanges can be a useful guide to securing these eight key nutrients. Keep in mind, however, that there is some variation in the proportion of the nutrients, not only between the food groups but also within each food group. For example, the grain food group does contain some protein, but it is not as good a source as the meat or milk group. Within the fruit group, oranges are an excellent source of vitamin C, but peaches are not, although peaches are high in vitamin A. If you select a wide range of foods within each group, the nutrient intake should be balanced over time. Table 2.7 presents a daily diet based upon the food exchanges. An example of a lowCalorie diet plan based upon the food exchanges is presented in chapter 11, together with methods for planning a diet based upon a specific number of Calories.

What is the concept of nutrient density? As mentioned before, the nutrient content of foods varies considerably, and the differences between food groups are more distinct than the differences between foods in the same group. Nutrient density is an important concept relative to the proportions of essential nutrients such as protein, vitamins, and minerals that are found in specific foods. In essence, a food with high nutrient density possesses a significant amount of a specific nutrient or nutrients per serving compared to its caloric content. We refer to these as quality Calories. Let’s look at an extreme example between two different food groups. Consider the nutrient differences between six ounces of baked Yellowfin tuna (meat and meat substitute exchange) and

six strips of fried bacon (fat exchange), each containing about 220 Calories. The tuna fish would provide a young adult female with 100 percent of her requirement for two key nutrients (protein and niacin) along with substantial amounts of several other vitamins, and minerals, but very little fat. The bacon would contain less than 25 percent of the protein requirement and about 10 percent of the niacin requirement, with greater amounts of total and saturated fat. Hence, the tuna fish has greater nutrient density and considerably greater nutritional value. Another example is presented in figure 2.6, which compares the nutrient density of milk and sweetened cola. Let’s also look at a comparison of two foods within the same group, the meat and meat substitute exchange. Consider the following nutritional data for three ounces of tuna fish and three ounces of clams:

3 oz. tuna: 3 oz. clams:

Calories 118 126

Protein 24 g 22 g

Iron 0.8 mg 24 mg

The protein density is similar in the two foods. However, clams contain more than thirty times the amount of iron per serving. Both foods are excellent sources of protein for the amount of Calories consumed, and although tuna fish is also a good source of iron, clams are a much superior source. These examples illustrate the need to consume a wide variety of foods among food groups and within each food group to satisfy your nutrient needs. www.mhhe.com/williams9

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TABLE 2.7

Example of a daily menu based on the food exchanges

Exchange

Food selections

Exchange

Breakfast

Food selections

Dinner

Meat Starch Milk Fruit Fat

Canadian bacon English muffin, whole wheat Skim milk Orange juice Low-fat margarine, trans fat free

Meat substitute Starch

Tuna fish (water pack) Whole wheat bread Skim milk Apple Lettuce and tomato Low-fat mayonnaise

Snacks

Milk Fruit Vegetable Fat

Lunch Meat Starch Milk Fruit Vegetable Fat

Baked beans Rice or pasta Bagel Yogurt Sliced peaches (in yogurt) Mixed salad Low-fat salad dressing

Fruit

Banana

Note: This table presents some common examples of foods within each of the six food exchanges. As discussed in the text, however, you should select food wisely among exchanges and within each exchange. For example, to avoid excessive amounts of Calories, cholesterol, and saturated fats, you should select skim milk, lean meats such as skinless turkey and chicken, water-packed tuna fish, low-fat yogurt, and low-fat, soft tub margarine.

Percent contribution to adolescent female RDAs 40%

30%

20%

10%

0%

0%

10%

20%

30%

Energy (Calories) Protein Vitamin A Vitamin C Thiamin Riboflavin Niacin Calcium Iron Sugared soft drink, 12 fl. oz.

Yale University’s Griffin Prevention Research Center recently developed an Overall Nutritional Quality Index (ONQI), which rates individual foods on a scale from 1 to 100 based on nutrient content and effects on health concerns. For example, broccoli scores 100 while soda scores 1. This ONQI will serve as the basis for the NuVal™ Nutritional Scoring System to rate foods in supermarkets and is scheduled to begin by early 2009. www.nuval.com Go the the NuVal™ site to obtain the ONQI score for a wide variety of foods found in local supermarkets.

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40%

FIGURE 2.6 Comparison of the nutrient density of a sugared soft drink with that of nonfat milk. Both contribute fluid to the diet. However, choosing a glass of nonfat milk makes a significantly greater contribution to nutrient intake in comparison with a sugared soft drink. An easy way to determine nutrient density is to see how many of the nutrient bars in the graph are longer than the Energy (Calories) bar. The soft drink has no longer nutrient bars. Nonfat milk has longer nutrient bars for protein, vitamin A, thiamin, riboflavin, and calcium. Including many nutrient-dense foods in your diet aids in meeting nutrient needs.

Nonfat milk, 1 cup

Will use of MyPyramid Food Guide or the food exchange system guarantee me optimal nutrition? If you use the key-nutrient and nutrient density concepts, MyPyramid or the Food Exchange System may be an effective means to obtain optimal nutrition and help sustain a healthful body weight. However, although the MyPyramid food guide and the Food Exchange System represent a significant improvement over previous food guides to help ensure proper nutrition, both have some flaws if foods are not selected carefully. For example, the Food Exchange

C H A P T E R 2 Healthful Nutrition for Fitness and Sport: The Consumer Athlete

System does provide some classification for high-fat and low-fat foods in the milk and meat exchanges, but individuals who predominantly choose the high-fat and high-sugar foods from among the food lists may be more susceptible to the development of chronic health problems. Krebs-Smith and Kris-Etherton noted that the recommendations in MyPyramid are remarkably consistent with the various recommendations to control most chronic diseases, including diabetes, heart disease and stroke, hypertension, cancer, and osteoporosis. Moreover, Reedy and Krebs-Smith compared the food-based recommendations and nutrient values of three food guides: the U.S. Department of Agriculture's MyPyramid; the National Heart, Lung, and Blood Institute's Dietary Approaches to Stop Hypertension Eating Plan, and Harvard University's Healthy Eating Pyramid. In essence, they concluded that the recommendations are similar regarding almost all food groups for both types and amount of foods people should eat. They also called the guidelines future proof, suggesting the basic pattern of eating nutrient-rich foods and limited calories from added sugar and fat is unlikely to change even though the research base for optimal eating practices continues to evolve. Nevertheless, the new MyPyramid has been criticized by some health professionals for various reasons. One of the main criticisms is MyPyramid by itself lacks clarity because it does not indicate what specific foods may be more healthful and which foods may be less healthful. Another criticism indicates the basic diet plan does not use height and weight to help determine caloric requirement. Still another is that you need to be computer literate and have access to a computer with an Internet connection to access the Website. These, as well as others, may be legitimate criticisms, but are not insurmountable. Although the MyPyramid figure by itself does not indicate which foods are healthful or unhealthful, the accompanying guidelines do. For example, the seven key guidelines presented in figure 2.4 provide individuals with suggestions for selecting healthier foods and limiting less healthful foods. More detailed information concerning healthful food selection is presented on the Website. Although the basic diet plan does not use your height and weight to calculate caloric needs, the MyPyramid Tracker program does. Those without Internet access may find assistance available in local libraries. Prior to the development of the MyPyramid food guidelines, the previous Food Guide Pyramid received considerable criticism, so much so that other more healthful models were proposed, such as the Mediteranean Food Guide Pyramid, the California Cuisine Food Pyramid, the Harvard Pyramid, and the Vegetarian Food Guide Pyramid. Basically, all proposed healthy modifications to the former Food Guide Pyramid attempt to reduce the consumption of or modify the type of fat, to increase the consumption of whole-grain products, and to increase the consumption of plant products, particularly beans and other legumes, fruits, and vegetables. http://www.hsph.harvard.edu/nutritionsource/ Click on Food Pyramids to view the Harvard Healthy Eating Pyramid.

The American Dietetic Association developed a position stand focusing on the message that healthful eating should emphasize the total diet, or overall pattern of food eaten, rather than any one food or meal, and that if consumed in moderation all foods can fit into a healthful diet. In concert with this ADA viewpoint, and reflecting healthful recommendations in MyPyramid, the major guidelines for healthier food choices are presented in the following section.

Ke y C o n c e p t s 䉴 If most healthy individuals in a given population consume whole-

some, natural foods in amounts adequate to meet their RDA, there will be very little likelihood of nutritional inadequacy or impairment of health. 䉴 The MyPyramid food guide and the related Food Exchange System—meat, milk, starch, fruit, vegetable, and fat—should be viewed as an educational approach to help individuals obtain proper nutrition. Foods of similar nutrient value are found in each of the six exchanges. 䉴 There are eight key nutrients (protein, vitamin A, thiamin, riboflavin, niacin, vitamin C, calcium, and iron) that, if adequate in the diet and obtained from wholesome foods, should provide an ample supply of all nutrients essential to human nutrition. 䉴 Some foods contain a greater proportion of these key essential nutrients than other foods and thus have a greater nutrient density or nutritional value.

C h e c k f o r Yo u r s e l f Using the record of all the food you consumed in one day, as recommended in chapter 1, try to categorize the food you have eaten by the Food Exchange System.

Healthful Dietary Guidelines In the past most morbidity and mortality in industrialized nations were caused by nutrient-deficiency diseases and infectious diseases, but advances in nutritional and medical science have almost eliminated most of the adverse health consequences associated with these diseases. Today, most morbidity and mortality are associated with various chronic diseases (e.g., coronary heart disease, stroke, cancer, diabetes, osteoporosis, obesity), and most dietary guidelines for healthful nutrition are targeted to prevent these chronic diseases. Nutrition scientists are using both epidemiological and experimental research in attempts to determine what types of diet, specific foods, and specific nutrients or food constituents may either cause or prevent the development of chronic diseases. Such research, coupled with the application of nutrigenomics, may provide each of us with individualized diets for optimal health.

What is the basis underlying the development of healthful dietary guidelines? In general, healthful dietary guidelines are based on appropriate research. Over the years, epidemiologists have attempted to determine the relationship between diet and the development of chronic diseases. www.mhhe.com/williams9

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In early research, the focus was simply on the overall diet and its relationship to disease, such as comparing the typical American diet to the Mediterranean (Greece, Italy, Spain) or Japanese diet. If a significant relationship was found between the diets of two nations, say more heart disease among Americans compared to those consuming the Mediterranean diet, scientists then attempted to determine what specific foods, particularly which macronutrients (carbohydrate, fat, and protein) in those foods, may have been related to either an increased or decreased risk for heart disease. In more recent years, scientists have been investigating the roles of specific nutrients or food constituents and their potential to prevent or deter chronic diseases. Based on the evaluation of current research findings, nutritional scientists believe that the development of most chronic diseases may be associated with either deficiencies or excesses of various nutrients or food constituents in the diet. As mentioned previously, most Americans eat more food than they need and eat less of the food they need more. In general, many Americans eat too many Calories, consume too much fat, saturated fat, cholesterol, refined sugars and starches, and salt and sodium, and drink too much alcohol. Such dietary practices may predispose one to several chronic diseases, including obesity, heart disease, hypertension, and cancer. Conversely, possibly because they rely more on highly processed foods, many Americans do not consume a diet rich in whole grain products, legumes, fruits, and vegetables, foods that are rich in dietary fiber and other healthful nutrients such as antioxidant vitamins. Some may not obtain adequate amounts of calcium and iron. These dietary practices may lead to such chronic diseases as cancer, osteoporosis, and anemia. To help prevent chronic diseases, over the years numerous governmental and professional health organizations have developed general dietary guidelines for good health. Some of these guidelines have been criticized, possibly because they were not based on the best science, as recently noted in the book Good Calories, Bad Calories: Challenging the Conventional Wisdom on Diet, Weight Control, and Disease by Gary Taubes. Most of the early research relating diet to disease was epidemiological in nature, which may have led to some erroneous dietary recommendations. However, experimental studies involving randomized controlled trials (RCTs) have predominated in recent years and, as noted by Woolf, rigorous procedures involving evidence-based approaches are currently used to develop dietary guidelines to promote health. For example, a recent RCT by Appel and others provided some evidence that modifying the type of carbohydrate, fat, and protein intake, referred to as the OmniHeart diet, could have favorable effects on several risk factors for heart disease. Although there is no absolute proof that dietary changes will enhance the health status of every member of the population, scientists involved in the development of healthful dietary guidelines believe that they are prudent recommendations for most individuals and are based on the available scientific evidence. www.omniheart.org Provides general and specific tips to improve the quality of your diet. www.hsph.harvard.edu/nutritionsource Excellent Website for nutrition information from the Harvard School of Public Health.

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What are the recommended dietary guidelines for reducing the risk of chronic disease? These prudent dietary recommendations represent a synthesis of various recent reports from governmental, educational, and professional health organizations, including the following: • • • • • • • •

American Cancer Society American Diabetes Association American Dietetic Association American Heart Association American Institute of Cancer Research Harvard School of Public Health United States Department of Agriculture United States Department of Health and Human Services

These recommendations are also in accord with Dietary Guidelines for Americans, 2005. The guidelines are not considered to be static, and may be modified somewhat as we gain more knowledge through research. In particular, healthful dietary recommendations may be individualized in the future when the full impact of nutrigenomics is realized. Taken together, these recommendations may be helpful in preventing most chronic diseases, including cardiovascular diseases and cancer. The rationale as to how these dozen healthful dietary recommendations may promote good health is presented in later chapters where appropriate. These guidelines do, however, come with several caveats. Remember, diet is only one factor that may influence the development of chronic diseases. As recently noted by the American Heart Association Nutrition Committee, other positive lifestyle behaviors, such as exercise and avoiding tobacco use, are also important. Most dietary guidelines have been developed for Americans over age 2, but some organizations, such as the American Heart Association, have developed separate dietary guidelines for children. Children and adolescents need energy to support growth and development, so it is important that adequate Calories be provided if dietary fat is restricted. Several of the guidelines presented below have special implications for children. Although research may show that some foods, such as fruits and vegetables, may be protective against the development of chronic diseases, it is the total diet that is important. The benefits that may accrue from adhering to only a few healthful eating recommendations may be negated if most dietary guidelines are ignored. You can maximize your health benefits by adopting as many of these healthful dietary guidelines as possible. In general, your diet should focus on good carbohydrates, good fats, and good protein, some of which are highlighted in Table 2.8. 1. Balance the food you eat with physical activity to maintain or achieve a healthy body weight. Consume only moderate food portions. Be physically active every day. Preventing obesity helps to reduce the risk of numerous chronic diseases, such as heart disease and cancer. To avoid becoming overweight, you should consume only as many Calories as you expend daily. Methods of regulating your body weight are presented in detail in chapter 11. An appropriate exercise program and

C H A P T E R 2 Healthful Nutrition for Fitness and Sport: The Consumer Athlete

TABLE 2.8

Examples of healthy,or so-called good carbohydrates, good fats,and good proteins that should comprise the majority of the daily caloric intake.

Good carbohydrates

Good fats

Good proteins

Whole wheat or grain Bread Cereal Rice Pasta Fruits Vegetables

Plant oils Olive oil Canola oil Unsalted nuts and seeds Pecans, walnuts, almonds Fish and seafood oil Avocados and olives

Very lean meat, fish, poultry Egg whites or substitutes Legumes, beans Vegetables Meat substitutes Unsalted nuts and seeds Pecans, walnuts, almonds

adherence to the concept of nutrient density, which includes a number of the following recommendations, could serve as the basis for a sound weight-control program. 2. Eat a nutritionally adequate diet consisting of a wide variety of nutrient-rich foods. Build a healthy base. Eating a wide variety of natural foods from within (and among) the MyPyramid food groups or the Food Exchange Lists will assure you of obtaining a balanced and adequate intake of all essential nutrients. Stress foods that are nutrient dense, particularly those that are rich in the key nutrients. However, keep the concept of variety in perspective. Research has shown that the more food choices we have, the more likely we are to eat more. Our supermarket society, with over 50,000 food products in the typical store, provides us with so many choices that it is very easy to overeat and become overweight. Thus, although consuming a wide variety of foods is a good strategy to get the nutrients we need, we must keep in mind the first point, to maintain or achieve a healthy body weight. An excellent book by Marion Nestle, a renowned professor of nutrition at New York University, entitled What to Eat: An Aisle-to-Aisle Guide to Savvy Food Choices and Good Eating provides some excellent advice about supermarket shopping. 3. Choose a diet moderate in total fat, but low in saturated and trans fats and cholesterol. There is no specific requirement for fat in the diet. However, a need exists for essential fatty acids (linoleic and alpha-linolenic fatty acids) and vitamins that are components of fat. Since almost all foods contain some fat, sufficient amounts of the essential fatty acids and related vitamins are found in the average diet. Even on a vegetarian diet of fruits, vegetables, legumes, and grain products, about 5 to 10 percent of the Calories are derived from fat, thus supplying enough of these essential nutrients. The following are some healthful recommendations for daily fat and cholesterol intake: • 20–35 percent of Calories from fat, which is consistent with the AMDR • 10 percent or less of Calories from saturated fat

• Less than 1 percent of Calories from trans fat • 300 milligrams or less of cholesterol However, some health groups specifically recommend lower amounts. The Consumers Union suggests that females with a personal or family history of breast cancer cut back on fat to 15 percent. The American Heart Association suggests limiting saturated fat to less than 7 percent of Calories. The following practical suggestions will help you meet the recommended dietary goal. a. Choose plant oils or other healthy fats. In general, most dietary fat should come from sources of monounsaturated and polyunsaturated fatty acids, such as fish, nuts, seeds, and vegetable oils, particularly olive and canola oil. b. Eat less meat with a high-fat content. Avoid hot dogs, luncheon meats, sausage, and bacon. Trim off excess fat before cooking. Eat only limited amounts of meat, mostly lean red meat and white meat, such as turkey and chicken, which have less fat. Remove the skin from poultry. Eat no more than 3–6 ounces of animal meat per day. c. Eat more fish. Many fish, such as sardines, salmon, tuna, and mackerel, are rich in omega-3 fatty acids. White fish, such as flounder, is very low in fat Calories. However, as noted in chapter 5, children and some women should avoid fish that may be polluted with mercury. d. Eat only several eggs per week. One egg yolk contains about 220–250 milligrams of cholesterol, close to the limit of 300 milligrams per day. Egg whites have no cholesterol and are an excellent source of high-quality protein. You may use commercially prepared egg substitutes, particularly those that are low in fat. e. Eat fewer dairy products that are high in fat. Switch from whole milk to low-fat or skim milk. Eat other dairy products made from skim or nonfat milk, such as yogurt and cottage cheese. Most cheeses, except low-fat cottage cheese, are high in fat and Calories, but some fat-free cheeses are now available. f. Eat less butter, which is high in saturated fats, by substituting soft margarine made from liquid oils that are monounsaturated or polyunsaturated, such as corn oil. Avoid hard margarine made from hydrogenated or partially hydrogenated oils that produce trans fatty acids, which basically are metabolized like saturated fats. Eat butter and margarine sparingly. Some fat-free and other healthier margarines are also available. g. Eat fewer commercially prepared baked goods made with eggs and saturated or hydrogenated fats. Many of these foods may also contain significant amounts of trans fatty acids. h. Limit your consumption of fast foods. Although fast-food chains generally serve grade A foods, many of their products are high in fat. The average fast-food sandwich contains approximately 50 percent of its Calories in fat. Appendix F provides a breakdown of the fat Calories and milligrams of cholesterol in products served by popular fast-food restaurants. Some fast-food restaurants do serve nutrient-dense foods. Wise choices, such as baked fish, www.mhhe.com/williams9

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F I G U R E 2 . 7 Nutritional labeling as a guide to sugar and fat in processed foods. Refined sugar and fats may appear in processed foods in a

variety of forms. Check for these terms on nutrition labels.

grilled skinless chicken, lean meat, baked potatoes, and salads, can provide healthy nutrition. But, avoid high-fat sauces. For example, the mayonnaise serving on a Burger King TENDERGRILL® chicken sandwich adds 110 Calories, or 12 grams of fat, which accounts for 21 percent of the total Calories of the sandwich. i. Use food labels to help you select foods low in total fat, saturated fat, trans fat, and fat Calories, all of which are listed on the food label for most products. In the ingredients list, look for the terms presented in figure 2.7, all of which contain fat. j. Broil, bake, or microwave your foods. Limit frying. If you must use oil in your cooking or food preparation, try to use monounsaturated oils such as olive, canola, or peanut oil. For other health reasons, as noted later, avoid charring foods when grilling or broiling. 4. Choose a plant-rich diet with plenty of fruits and vegetables, whole-grain products, and legumes, foods which are rich in complex carbohydrates, phytochemicals, and fiber (see figure 2.8). In general, about 45–65 percent or more of your daily Calories should come from carbohydrates, about 35–55 percent from complex carbohydrates, and the other 10 percent from simple, naturally occurring carbohydrates. To accomplish this, you need to eat more whole-grain breads, cereal, rice, and pasta, more legumes such as beans and peas, more fruits and vegetables, and less refined grain products, such as white bread, rice, and pasta. Numerous epidemiological studies have shown that diets rich in plant foods confer significant health benefits, which are attributable mainly to the complex mixture of phytochemicals and dietary fibers. The health benefits of phytochemicals and dietary fiber are discussed, respectively, in the next section on vegetarianism and in chapter 4. Health professionals recommend that 50 percent or more of our total grain intake should be whole grains, but currently Americans consume less than 15 percent. When buying cereal, bread, rice, and other grain products, ensure that they 50

F I G U R E 2 . 8 Include in your diet foods high in plant starch and

fiber. Eat more fruits, vegetables, and whole-grain products.

contain whole grains, preferably 100 percent Whole Grain on the food label. Whole-grain products are rich in dietary fiber and phytochemicals as well as several key nutrients. Select whole wheat bread where you can see the grain, whole-grain cereals such as Cheerios, Wheaties, and Quaker Oatmeal, and whole-grain pasta. Consume three or more ounce equivalents of whole-grain products per day, and check food labels that provide for grams of fiber per serving. In particular, eat a wide variety of fruits and vegetables, including legumes. The slogan Eat Your Colors Every Day to Stay Healthy and Fit refers to the health benefits associated with eating fruits and vegetables of different colors and the associated phytochemicals that appear to protect you against heart disease, strokes, and several forms of cancer. Eat at least five servings of fruits and vegetables daily, but this is a minimum. Another slogan, Fruits & Veggies—More Matters, reflects the importance of consuming more than the minimum. Grill vegetables and bake fruits to add flavor. Eat larger portions. For example, one-half cup of cooked vegetables is a standard serving size, so a full cup represents two servings.

C H A P T E R 2 Healthful Nutrition for Fitness and Sport: The Consumer Athlete

5. Choose beverages and foods to moderate your intake of added sugars. Natural sugars are found in fruits and milk, while added sugars are defined as sugars eaten separately, such as table sugar to sweeten coffee, or used as ingredients in processed or prepared foods. The National Academy of Sciences recently recommended that the maximum amount of added sugars in the diet be 25 percent. However, this recommendation has been challenged by dietitians who indicate that taking in a quarter of your Calories from added sugars does not appear to represent healthful dietary advice, and trying to reduce intake to 10 percent is a healthier alternative. Excessive consumption of refined sugar has been associated with high blood triglyceride levels. Sticky sugars are a major contributing factor to dental cavities. Sugars also significantly increase the caloric content of foods without an increase in nutritional value, so they may contribute to body weight problems. Americans eat the equivalent of about 30 teaspoons of added sugar daily, which is the equivalent of about 500 Calories. To meet this goal you should reduce your intake of common table sugar and products high in refined sugar, such as nondiet soft drinks, the largest source of added sugars in the American diet. Sugar is one of the major additives to processed foods, so check the labels. If sugar is listed first, it is the main ingredient. Also look for terms such as high-fructose corn syrup, dextrose, fructose, malt sugar, and even fruit juice concentrate which are also primarily refined sugars (figure 2.7). Food labels list the total amount of sugar per serving. Use naturally occurring sugars to satisfy your sweet tooth. Most fruits have a high sugar content, but also contain vitamins, minerals, and fiber as well. 6. Choose and prepare foods with less salt and sodium. Restrict sodium intake to less than 1,500 mg daily, which is the equivalent of 3,750 milligrams, or 3.75 grams, of table salt. This lower amount will provide sufficient sodium for normal physiological functioning. Sodium is found naturally in a wide variety of foods, so it is not difficult to get an adequate supply. Several key suggestions may help you reduce the sodium content in your diet. a. Get rid of your salt shaker. One teaspoon of salt is 2,000 mg of sodium; the average well-salted meal contains about 3,000 to 4,000 mg. Put less salt on your food both in your cooking pot and on your table. b. Reduce the consumption of obviously high-salt foods such as most pretzels and potato chips, pickles, and other such snacks. c. Check food labels for sodium content. Salt is a major additive in many processed foods, and food labels list the sodium content per serving. d. Eat more fresh fruits and vegetables, which are very low in sodium. Fruits, both fresh and bottled or canned, have less than 8 mg of sodium per serving. Fresh and frozen vegetables may have 35 mg or less, but if bottled or canned may contain up to 460 mg. e. Use fresh herbs, spices that do not contain sodium, or lite salt as seasoning alternatives.

The OmniHeart and DASH (Dietary Approaches to Stop Hypertension) diets, discussed in chapter 9, are low-sodium diets. 7. If you drink alcoholic beverages, do so in moderation. The current available scientific evidence does not suggest that light to moderate daily alcohol consumption will cause any health problems to the healthy, nonpregnant adult. A drink is defined as one 12-ounce bottle of beer, one 4-ounce glass of wine, or 1.5 ounces of 80-proof distilled spirits. Current guidelines for moderate alcohol intake recommend no more than two drinks per day for males and one for females. However, even small amounts may pose health problems to some individuals. Certainly, excessive alcohol consumption is one of the most serious health problems in our society today. An expanded discussion is presented in chapter 13. 8. Maintain protein intake at a moderate, yet adequate level, obtaining much of your daily protein from plant sources complemented with smaller amounts of fish, skinless poultry, and lean meats. The recommended dietary intake is 0.8 grams of protein per kilogram body weight, which averages out to about 50 to 60 grams per day for the average adult male and somewhat less for the average adult female or about 10 percent of daily Calories. The current recommendation of the National Academy of Sciences is to obtain 10–35 percent of daily Calories from protein. Since the average daily American intake of protein is about 100 grams, we appear to be staying within the guidelines. However, most of the protein Americans eat is of animal origin. Although animal products are an excellent source of complete protein, they tend to be higher in saturated fats and cholesterol compared with foods rich in plant protein. On the other hand, animal protein is usually a better source of dietary iron and other minerals like zinc and copper than plant protein is. Three to six ounces of lean meat, fish, or poultry, together with two glasses of skim or soy milk, will provide the average individual with the daily RDA for protein, totaling about 40–60 grams of high-quality protein. Combining this animal protein intake with plant foods high in protein, such as wholegrain products, soy-protein meat substitutes, beans and peas, and vegetables, will substantially increase your protein intake and more than meet your needs. Soy protein products, such as tofu, soy milk, tempeh, and miso, as well as commercial products such as soy sausages and burgers, are excellent meat substitutes. Soy offers a complete protein profile and may also provide some health benefits, as highlighted in chapter 6. The general recommendation is to eat less meat, and that which is eaten preferably should be fish. White poultry meat, such as turkey breast, and lean red meats, such as beef eye of round or pork tenderloin, may also be incorporated into the diet. One healthful recommendation is to use meat as a condiment, such as helping to add flavor to stir-fried vegetable dishes. In a recent review, Mann noted scientific evidence is accumulating that meat itself is not a risk factor for chronic disease, but rather the risk stems from the excessive fat found in modern-day domesticated animals. Lean meat is a healthy www.mhhe.com/williams9

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and beneficial component of any well-balanced diet as long as it is fat trimmed and consumed as part of a varied diet. On average, the recommended total meat intake should range between 3 to 6 ounces daily; of that total, men and women should consume, respectively, less than 3 and 2 ounces of red or processed meat. Why this recommendation? Epidemiological studies report that a diet rich in red and processed or well-done meat is associated with an increased risk of colon cancer, breast cancer, and lung cancer. Possible reasons may be that red and processed meat tends to contain lots of fat (particularly saturated fat), cooking meat at high temperatures can create potentially cancer-causing compounds, and meat of hormone-treated animals may have adverse effects on human health. 9. Choose a diet adequate in calcium and iron. Individuals susceptible to tooth decay should obtain adequate fluoride. Adequate calcium and iron are particularly important for women and children. Skim or low-fat milk and other low-fat dairy products are excellent sources of calcium. For example, one glass of skim milk provides nearly one-third the RDA for calcium. Certain vegetables, such as broccoli, are also good sources of calcium. Iron is found in good supply in the meat and starch exchanges. Small amounts of lean or very-lean meats should be selected so as to limit fat intake, and wholegrain or enriched products should be chosen over those made with bleached, unenriched white flour. Some foods rich in calcium and iron are listed in table 2.9. Adequate flouride is particularly important during childhood when the primary and secondary teeth are developing, for fluoride helps prevent tooth decay by strengthening the tooth enamel. Your water supply may contain sufficient fluoride— naturally or artificially—to provide an adequate amount, but if not, fluoride supplements or use of fluoride toothpaste may be recommended. 10. Practice food safety, including proper food preservation and preparation. Food should be stored in ways that minimize contamination with bacteria. Use refrigeration to preserve perishable foods. Food preparation techniques should also minimize possible bacteria contamination. Using careful washing techniques is very helpful.

TABLE 2.9

Foods rich in calcium and iron

Mineral

Food source

Calcium

All dairy products: milk, cheese, ice milk, yogurt; egg yolk; dried peas and beans; dark-green leafy vegetables such as beet greens, spinach, and broccoli; cauliflower

Iron

Organ meats such as liver; meat, fish, and poultry; shellfish, especially clams and oysters; dried beans and peas; whole-grain products such as breads and cereals; dark-green leafy vegetables such as spinach and broccoli; dried fruits such as figs, raisins, apricots, and dates

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One specific recommendation, as related to the preceding point discussing meat consumption, is to avoid excess grilling or broiling of foods, particularly meat. Charring meats may lead to the formation of various carcinogens known as heterocyclic amines (HCA). Frying foods may also produce HCA, but steaming, boiling, and microwaving meat is much safer because these techniques produce fewer HCA that may cause cancer. If you enjoy the flavor of grilled or broiled foods, marinating meats may dramatically reduce HCA formation. A healthful technique is to precook marinated meat in a microwave, and then grill or broil briefly for flavor, but not to the point of charring. More detailed information on food safety is presented later in this chapter. 11. Consider the benefits and risks of food additives and dietary supplements. The general consensus is that most additives used in processed foods are safe, but several health agencies, such as the Center for Science in the Public Interest, recommend caution with additives such as sulfites and certain food colors, which may cause allergic reactions in some individuals. Wilson and Bahna note that although adverse reactions to additives seem to be rare, they are likely to be underdiagnosed in part due to a low index of suspicion. Some research has shown that certain additives such as food dyes and preservatives in soft drinks can cause some children to become measurably more hyperactive and distractible. Eating fresh, natural foods is one of the best approaches to avoiding additives. However, nutrients such as vitamins and minerals are often used as food additives to increase the nutritional quality of a food product, which may benefit some individuals. As noted in chapters 7 and 8, dietary supplements of most vitamins and minerals are not necessary for individuals consuming a balanced diet. If you adhere to the recommendations listed here, you are not likely to need any supplementation at all, for the consumption of natural, whole, nutrient-dense foods should guarantee adequate vitamin and mineral nutrition. If you feel a supplement is needed, the ingredients should not exceed 100 percent of the daily RDA for any vitamin or mineral. Many one-a-day vitamin-mineral supplements do adhere to this standard. Moreover, many health professionals are recommending dietary supplements for certain segments of the population. For example, in their position statement the American Dietetic Association notes that additional vitamins and minerals from fortified foods and/or supplements can help some people meet their nutritional needs as specified by such standards as the DRI. The American Heart Association recommends fish oil supplements, under guidance of a physician, for some who have heart disease or heart disease risk factors. The Consumers Union, in recommending nutrition to help lessen the adverse health effects of aging, suggested the possibility of vitamin (B12, D) and mineral (calcium) supplementation as one ages past 50. The American Academy of Pediatrics recommends fluoride supplementation for children if the water supply does not contain fluoride, or if the child drinks only bottled water. As shall be noted in

C H A P T E R 2 Healthful Nutrition for Fitness and Sport: The Consumer Athlete

chapter 7, some health professionals believe it may be prudent for most individuals to take a daily multivitamin. Conversely, excess supplementation with some vitamins and minerals, as well as other dietary supplements, may elicit some serious adverse health effects. The possible health benefits of dietary supplements, as well as possible adverse effects, will be discussed in later chapters where appropriate. 12. Enjoy your food. Eat what you like, but balance it within your overall healthful diet. It is important to note that you can eat whatever you want with the Prudent Healthy Diet. There are no unhealthy foods, only unhealthy diets. The dietary advice to moderate intake of certain foods, such as high-fat meats and ice cream, does not mean that they have to be eliminated from the diet, but that their intake be limited and balanced with other nutrient-dense foods in the total diet. Portion control is an important concept to limit caloric intake. It is balance, variety, and moderation in the overall diet that is important, not any single food. In this context, it is important to note that although healthful eating may confer numerous health benefits, some may take it to extremes whereby it may become counterproductive. In his book, Health Food Junkies: Overcoming the Obsession with Healthful Eating, Bratman indicates that taking the quest for a healthful diet to excess can become a disease in its own. Enjoy eating; it is one of life’s pleasures. To make healthier foods such as chicken, fish, and vegetables taste better, season them with spices. Spices not only enhance flavor of some foods, but also contain various phytochemicals that may have beneficial health effects. Some suggestions include the following: • Cinnamon: Use on beef, oatmeal, rice, yogurt, and fruit • Turmeric: Use on chicken, eggs, and fish • Cayenne: Use on chicken, beef, fish, vegetables, and in pasta sauce • Nutmeg: Use on oatmeal, rice, yogurt, vegetables, and fruit • Ginger: Use on chicken, beef, yogurt, and fruit The Healthy Prudent Diet Your health depends on a variety of factors such as heredity and certain aspects of your environment. Adherence to these twelve simple guidelines will not guarantee you good health; however, the available data indicate that these dietary changes have the potential to keep you healthy or even to improve upon your current health status. The sooner in life one develops healthy eating habits, the better. Research has shown that preadolescent children can modify their lifestyle, eating healthier foods and engaging in exercise. The National Institute of Health has launched a national public education program entitled We Can! Ways to Enhance Children’s Activity & Nutrition.

A Dietary Guidelines Alliance, with representatives from several leading health, government, and food industry organizations, has proposed five simple messages to motivate you into positively, changing your eating and physical activity routines. They are: • Be realistic. Make small changes over time in what you eat and the level of activity you do. Small steps work better than giant leaps. • Be adventurous. Expand your tastes to enjoy a variety of foods. • Be flexible. Balance what you eat and the physical activity you do over several days. No need to worry about just one meal or one day. • Be sensible. Enjoy all foods, just don’t overdo it. • Be active. Start moving, even in small steps. Walk the dog, don’t just watch the dog walk. (See appendix H.) Although it may not appear obvious, the general nature of the Prudent Healthy Diet is a shift toward vegetarianism, so it may be important to address the nature of this dietary regimen.

Ke y C o n c e p t 䉴 Here are twelve recommendations for healthier nutrition.

1. Maintain or improve a healthy weight. 2. Consume a wide variety of natural, whole, nutrient-rich foods. 3. Choose a diet moderate in total fat and low in saturated and trans fats and cholesterol. 4. Choose a plant-rich diet with plenty of whole-grain products, legumes, fruits, and vegetables. 5. Choose a diet moderate in sugars. 6. Choose a diet with less salt and sodium. 7. Drink alcoholic beverages in moderation, if at all. 8. Eat protein at a moderate, yet adequate level. 9. Choose a diet adequate in calcium, iron, and fluoride. 10. Practice food safety. 11. Consider the benefits and risks of food additives and dietary supplements. 12. Enjoy your food!

C h e c k f o r Yo u r s e l f Think about your dietary habits and then determine how many of the twelve healthful dietary guidelines you follow.

Vegetarianism Many individuals have been changing their diets to improve their health. One of the major changes has been a shift toward a vegetarian-type diet.

What types of foods does a vegetarian eat? http://wecan.nhlbi.nih.gov Check this national program entitled We Can! to find ways in which to enhance children’s participation in physical activity and encourage healthy eating.

There are a variety of ways to be a vegetarian. A strict vegetarian, known also as a vegan, eats no animal products at all. Most nutrients are obtained from fruits, vegetables, breads, cereals, www.mhhe.com/williams9

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legumes, nuts, and seeds. Ovovegetarians include eggs in their diet, while lactovegetarians include foods in the milk group such as cheese and other dairy products. An ovolactovegetarian eats both eggs and milk products. These latter classifications are not strict vegetarians, because eggs and milk products are derived from animals. Others may call themselves semivegetarians because they do not eat red meat such as beef and pork products, although they may eat fish and white poultry meat. Those who eat fish, but not poultry, are known as pescovegetarians. In practice, then, vegetarians range on a continuum from those who eat nothing but plant foods to those who eat a typical American diet with the exception

TABLE 2.10

of red meat. The concern over obtaining a balanced intake of nutrients depends upon where the vegetarian is on that continuum. The more you restrict your food groups, the more difficult it is to get the nutrients you need. As a general guide, table 2.10 presents the amounts of food that should help meet daily nutrient requirements for the vegan. The amounts may be increased to provide additional Calories. Foods rich in iron, calcium, zinc, and riboflavin should be included daily. Use of fortified foods or supplements can be helpful in meeting recommendations for individual nutrients. Other classes of vegetarians may obtain nutrients from cow milk, eggs, cheese, yogurt, and in the case of semivegetarians, from fish or poultry.

Daily food guidelines for a vegetarian (vegan) diet

Grains and starchy vegetables

Fruits

Servings: 8–11 or more daily Note: Use whole wheat or other whole grains. Products made of oats, rice, rye, corn, and whole wheat are good sources of protein, B vitamins, and iron, more so if they are fortified products. Fortified cereals may provide adequate vitamin B12. Food examples: Barley Macaroni, enriched Bran flakes Oatmeal Bread, whole wheat Potatoes Buckwheat pancakes Rice, brown Corn Rye wafers Corn muffins Spaghetti, enriched Farina, cooked Sweet potatoes Fortified cereals Wheat, shredded

Servings: 4 or more daily Note: Fruits are generally good sources of vitamins and minerals. At least one fruit should come from the citrus group and one from the high-iron group. Select fruits of different colors. Food examples: Regular Citrus High iron Apples Oranges Dried apricots Bananas Orange juice Dried prunes Grapes Grapefruit Dried dates Peaches Grapefruit juice Dried figs Pears Lemon juice Dried peaches Pineapple Raisins Prune juice Vegetables

Legumes Servings: 3 or more daily Note: Good sources of protein, niacin, iron, and Calories. Food examples: Great northern beans Soybeans Navy beans Tofu Red kidney beans Split peas Pinto beans Chickpeas Lima beans Lentils Nuts and seeds Servings: 3 or more daily Note: Good sources of Calories, protein, niacin, and iron. May be excellent snack foods. Food examples: Almonds Pecans Brazil nuts Walnuts Cashew nuts Sesame seeds Peanuts Sunflower seeds Peanut butter Pumpkin seeds

Servings: 4–6 or more daily Note: Vegetables are good sources of vitamins and minerals. At least one serving should come from the dark-green or deep-yellow vegetables. Select other color vegetables as well. Food examples: Regular Dark-green or deep-yellow Artichokes Beet greens Asparagus Broccoli Beans, green Carrots Cabbage Collard greens Cauliflower Lettuce Cucumbers Spinach Eggplant Squash Radishes Tomatoes Milk products (calcium-rich foods) Servings: 3 or more daily Note: Good source of protein and calcium, if fortified. Food examples: Non-dairy soy milk Non-dairy rice milk

Sweets and vegetable oils may be added to increase caloric intake.

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C H A P T E R 2 Healthful Nutrition for Fitness and Sport: The Consumer Athlete

What are some of the nutritional concerns with a vegetarian diet? In their position statement, the American Dietetic Association and Dietitians of Canada noted that planned vegetarian diets are healthful, nutritionally adequate, and provide health benefits in the prevention and treatment of certain diseases. However, if foods are not selected carefully, the vegetarian may suffer nutritional deficiencies involving Calories, vitamins, minerals, and protein. Vegetarian diets, particularly vegan diets, should be well-planned, especially for children. Messina and Mangels noted that vegetarian diets can be, but are not necessarily, adequate for children. The major threats to the diet of children are lack of variety of foods and too much reliance on vegetarian convenience foods, which may not possess the nutritional quality of unprocessed plant foods. Calories Caloric deficiency is one of the lesser concerns of a vegetarian diet. However, because plant products are generally low in caloric content, a vegetarian may be on a diet with insufficient Calories for proper body weight maintenance. This may be particularly true for children, who need energy for growth and development, and for the active individual who may be expending over 1,000 Calories per day through exercise. The solution is to eat greater quantities of the foods that constitute the diet, and to include some of the higher-Calorie foods like nuts, beans, corn, green peas, potatoes, sweet potatoes, avocados, orange juice, raisins, dates, figs, whole wheat bread, and pasta products. These foods may be used in main meals and as snacks. On the other hand, the low caloric content of vegetarian diets may be a desirable attribute for some, as it may be useful in weight-reduction programs or helpful in maintenance of proper body weight. However, Martins and others have voiced concern that some individuals may adopt a vegetarian dietary style in an attempt to mask their dieting behavior from others. Adopting a vegetarian-type diet may be a very useful strategy for weight control, but may be detrimental if associated with an eating disorder. Vitamins Strict vegetarians may incur a vitamin B12 deficiency because this vitamin is not found in plant foods. Vitamin B12 is found in many animal products such as meat, eggs, fish, and dairy products, so the addition of these foods to the diet will help prevent a deficiency state. An ovolactovegetarian should have no problem getting the required amounts. A vegan will need a source of B12, such as fortified soy milk, fortified breakfast cereal, or a B12 supplement. If not exposed to sunlight, vegans will also need dietary supplements of vitamin D, which is not found in plant foods. Minerals Mineral deficiencies of iron, calcium, and zinc may occur. During the digestion process, some plant foods form compounds known as phytates and oxalates that can bind these minerals so that they cannot be absorbed into the body. Avoidance of unleavened bread helps reduce this effect, as does thorough cooking of legumes such as beans. In general, research has revealed that a balanced intake of grains, legumes, and vegetables will not significantly impair mineral absorption. Foods rich in iron, calcium, and zinc should also be included in the vegetarian diet.

Iron-rich plant foods include nuts, beans, split peas, dates, prune juice, raisins, green leafy vegetables, and many iron-enriched grain products. Special attention should be given to dietary practices that promote absorption of iron and zinc from plant foods. For example, consuming foods rich in vitamin C will increase the absorption of dietary iron from plant sources. Semivegetarians may obtain highquality iron in fish and poultry. Calcium-rich plant foods include many green vegetables like broccoli, cabbage, mustard greens, and spinach. Dairy products added to the diet supply very significant amounts of calcium, as do calcium-fortified soy milk or orange juice. Key and others noted that vegetarian diets may be low in calcium, which may be associated with the findings that vegans do have lower bone mineral density than their nonvegan counterparts. However, Smith noted that the evidence is inconclusive as to whether calcium intake in vegans increases the risk of fracture incidence. Zinc-rich plant foods include whole wheat bread, peas, corn, and carrots. Egg yolk and seafood also add substantial zinc to the diet. Iodine deficiency may occur with strict vegetarian diets, particularly when plant foods grown in iodine-depleted soils are ingested. In such cases, use of iodized salt will prevent iodine deficiency. Protein The major concern of the vegetarian is to obtain adequate amounts of the right type of protein, particularly in the case of young children. Generally speaking, consuming enough Calories to maintain an optimal body weight will provide adequate amounts of protein. As will be noted in chapter 6, proteins are classified as either complete or incomplete. A protein is complete if it contains all of the essential amino acids that the human body cannot manufacture. Animal products generally contain complete proteins, whereas plant proteins are incomplete. However, certain vegetable products may also provide good sources of protein. Grain products such as wheat, rice, and corn, as well as beans (particularly soybeans), peas, and nuts, have a substantial protein content. However, most vegetable products lack one or more essential amino acids in sufficient quantity. They are incomplete proteins and, eaten individually, are not generally adequate for maintaining proper human nutrition. But, if certain plant foods are eaten together, they may supply all the essential amino acids necessary for human nutrition and may be as good as animal protein (see Figure 2.9). The strict vegetarian must receive nutrients from breads and cereals, nuts and seeds, legumes, fruits, and vegetables. To receive a balanced distribution of the essential amino acids, the vegan must eat plant foods that possess complementary proteins. In essence, a vegetable product that is low in a particular amino acid is eaten with a food that is high in that same amino acid. For example, grains and cereals, which are low in lysine, are complemented by legumes, which have adequate amounts of lysine. The low level of methionine in the legumes is offset by its high concentration in the grain products. These types of food combinations are practiced throughout the world. Traditionally, many Hispanic peoples have eaten beans and corn; many Asians, soybeans and rice. Through the proper selection of foods that contain complementary proteins, the vegan can get an adequate intake of the essential amino acids. Because all amino acids need to be present for tissue www.mhhe.com/williams9

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formation, a deficiency of one or two essential amino acids will limit the proper development of protein structures in the body. In their position statement regarding vegetarian diets, the American Dietetic Association and Dietitians of Canada stated that complementary proteins should be consumed over the course of the day. The ADA noted that since endogenous sources of amino acids are available, it is not necessary that complementation of amino acids occur at the same meal. Table 2.11 provides some examples of food combinations that achieve protein complementarity. Milk is included because it is a common means of enhancing the quality of plant protein for lactovegetarians, but eggs could also be substituted by ovovegetarians where appropriate. The two most common plant foods that vegans combine to achieve protein complementarity are grains and legumes. Grains such as wheat, corn, rice, and oats are combined with legumes such as soybeans, peanuts, navy beans, kidney beans, lima beans, black-eyed peas, and chickpeas. F I G U R E 2 . 9 It is important for the vegetarian to eat protein foods that comple-

Is a vegetarian diet more healthful than a nonvegetarian diet?

ment each other (e.g., nuts and bread, rice and beans) so that all the essential amino acids are obtained in the diet.

Numerous epidemiological studies have suggested that a vegetarian diet, when compared to the typical nonvegetarian Western diet, is associated with reduced risk for numerous chronic diseases and health problems, including obesity, hypertension, blood sugar and lipid control, heart disease, stroke, and some types of cancer. For example, Bazzano and oth-

TABLE 2.11

Combining foods for protein complementarity

Milk and grains Pasta with milk or cheese Rice and milk pudding Cereal with milk Macaroni and cheese Cheese sandwich Cheese on nachos* Milk and legumes Creamed bean soups* Cheese on refried beans* Grains and legumes Rice and bean casserole Wheat bread and baked beans Corn tortillas and refried beans* Pea soup and toast Peanut-butter sandwich *Low-fat, low-sodium versions should be selected to minimize excessive saturated fat and sodium intake.

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ers recently reported that an increased intake of fruits and vegetables was associated with a decreased risk of strokes, cardiovascular disease, and all-cause mortality in nearly 10,000 Americans over a 19-year period. Key and others noted that the nature of the vegetarian diet is based on certain nutritional concepts that may reduce health risks, including the following. Nutrient Density Vegetarian diets contain substantial amounts of nutrient-dense foods, particularly vegetables. For example, one 54-Calorie cup of cooked broccoli contains the following: • • • • • • • •

4 grams of protein 5 grams of dietary fiber 10 or more vitamins and minerals 170 percent of the Daily Value for vitamin C 50 percent of the Daily Value for vitamin A, as carotenoids 42 percent of the Daily Value for folate 30 percent of the Daily Value for potassium 6 percent of the Daily Value for calcium and iron

Low Fat and Cholesterol The total fat and saturated fat content in a vegetarian diet is usually low because the small amounts of fats found in plant foods are generally polyunsaturated. Plants also do not contain cholesterol; this compound is found only in animal products. These two factors account for the finding that vegetarians generally have lower blood triglycerides and cholesterol than meat eaters, and these lower levels may be important to the prevention of coronary heart disease. High Fiber Plant foods possess a high content of fiber, which may help reduce levels of serum cholesterol and help in the preven-

C H A P T E R 2 Healthful Nutrition for Fitness and Sport: The Consumer Athlete

tion of heart disease. Diets rich in fiber may also prevent certain disorders in the gastrointestinal tract. Moreover, increased fiber intake may help maintain normal blood glucose levels and a healthy body weight, two factors involved in the prevention of diabetes. More details on the health benefits of fiber are presented in chapter 4. Low Calorie If the proper foods are selected, the vegetarian diet supplies more than an adequate amount of nutrients and is rather low in caloric content. Plant foods can be high in nutrient density, providing bulk in the diet without the added Calories of fat. Hence, the vegetarian diet can be an effective dietary regimen for losing excess body weight. However, vegetarians who consume dairy products need to select low-fat versions instead of high-fat cheeses and whole milk. High Vitamin and Phytochemical Content Plant foods are rich in various vitamins, including folic acid. As discussed in chapter 7, diets containing good sources of folic acid may be associated with lower risks of cardiovascular disease. Plant foods are also rich in antioxidant vitamins, particularly vitamin C and beta-carotene, a precursor to vitamin A. Polyunsaturated plant oils provide substantial amounts of vitamin E. Selenium, an antioxidant mineral, is found in other plant foods. Other than nutrients, plants also contain numerous phytochemicals (plant chemicals), compounds, such as phenols, plant sterols, and terpenes, which are not considered essential nutrients but may still influence various metabolic processes in the body. Collectively, these antioxidant nutrients and phytochemicals are referred to as nutraceuticals, parts of food that may provide a medical or health benefit, as suggested in a recent position stand of the American Dietetic Association on phytochemicals. Table 2.12 provides a list of some antioxidant nutrients and phytochemicals and their common plant sources. Although the exact mechanisms whereby antioxidant nutrients and phytochemicals may help prevent chronic diseases such as cancer or heart disease have not been identified, several hypotheses are being studied. Potential health benefits of antioxidants and phytochemicals may be related to one or more of their possible roles in human metabolism: • • • • • •

affect enzyme activity detoxify carcinogenic compounds block cell receptors for natural hormones prevent formation of excess oxygen-free radicals alter cell membrane structure and integrity suppress DNA and protein synthesis

Some of these actions may favorably affect health, as in the following two examples. Antioxidants, such as carotenoids, may block the oxidation of certain forms of serum cholesterol, reducing their potential to cause atherosclerosis and possible heart disease. Also, phytochemicals known as phytoestrogens may compete with natural forms of estrogen in the body for estrogen receptors in various tissues, blocking estrogen’s natural proliferative activity and possibly suppressing cancer development. Considerable epidemiological research has suggested that foods rich in antioxidants and phytochemicals may possess therapeutic value. Conversely, a few studies have suggested that excess of some

TABLE 2.12 Some antioxidant nutrients and

phytochemicals with common food sources Antioxidant nutrients

Common plant sources

Vitamin C

Citrus fruits Potatoes Strawberries Dark-green leafy vegetables Margarine Vegetable oils Wheat germ Whole grains

Vitamin E

Phytochemicals

Common plant sources

Allium sulfides

Garlic Onions Blueberries Hot peppers Carrots Dark-green leafy vegetables Sweet potatoes Tomatoes Citrus fruits Apples Tea Cruciferous vegetables Broccoli Brussels sprouts Cabbage Cauliflower Kale Soybeans Peanuts Soy milk Cruciferous vegetables Broccoli Brussels sprouts Cabbage Cauliflower Kale Carrots Citrus fruits Tomatoes Whole grains Grapes Red wines Grapes Beans Legumes Cherries Citrus fruits

Anthocyanins Capsaicin Carotenoids Beta-carotene Lycopene Lutein Flavonoids Quercetin Catechin Indoles

Isoflavones Phytoestrogens Genistein Isothiocyanates Sulforaphane

Phenolic acids

Polyphenols Resveratrol Saponins Terpenes Limonene

phytochemicals may be harmful. For example, Skibola and Smith note that excess flavonoid intake may be mutagenic or pro-oxidant, generating free radicals. Experimental research in this area is limited. Studies involving supplementation with soy protein, which contains numerous phytochemicals, have reported beneficial health www.mhhe.com/williams9

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effects. However, Mares-Perlman and others noted that although certain phytochemicals in foods, such as the carotenoids lutein and zeaxanthin, may protect against the development of several chronic diseases, research is needed to evaluate the effect of their consumption independent of other nutrients in fruits and vegetables. www.ars-grin.gov/duke/plants.html Obtain a list of all the vitamins and other phytochemicals found in your favorite food or plant, like strawberries.

Most nutrition scientists indicate that many of these nutrients and phytochemicals share the same food sources, so the protective health effect associated with a plant-rich diet may not be attributed to a single food constituent, but may be due to the collective effect of multiple nutraceuticals. Thus, health professionals currently recommend that consuming natural plant foods, rather than supplements, is the best way to obtain these purported nutraceuticals. To help ensure that you obtain a wide variety of healthful phytochemicals in your diet, eating foods of many different colors is one proposed strategy recommended by health professionals. Details are provided in several books, including The Color Code: A Revolutionary Eating Plan for Optimal Health by Joseph and Nadeau. Fruits and vegetables may contain numerous vitamins and phytochemicals, each of which may have some beneficial health effect. Table 2.13 lists the key colors and some examples of foods found within each color group. In brief, the following highlights one of the main health effects for one food of each color. Red—Tomatoes and tomato products contain lycopene, which may help prevent prostate cancer. Blue/purple—Blueberries contain anthocyanins, which may help lower blood pressure and risk of heart disease. Yellow/orange—Carrots contain carotenoids, which may reduce risk of heart disease. Green—Broccoli contains sulforaphane, which may help prevent cancer. White/brown—Onions contain allicin, which may help lower cholesterol and risk of heart disease. In summary, although a vegetarian diet is more healthful than a typical high-fat diet, it should be emphasized that the nonvegetarian who carefully selects foods from the meat and milk group, including limited amounts of lean red meat, may attain the same

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health benefits as the vegetarian. The major nutritional difference between a vegetarian and a nonvegetarian diet appears to be the higher content of saturated fats and cholesterol and lower amounts of fruits and vegetables in the latter. Selection of animal products with a low-fat and low-cholesterol content helps avoid one of these problems and also assures consumption of very high-quality proteins. In two recent reviews, Mann and Truswell noted that lean meat may not be as detrimental to health as once assumed, although adverse health effects may be associated with high-fat meats and unsafe methods of preparation. The National Research Council, in Diet and Health: Implications for Reducing Chronic Disease Risk, did not recommend against eating meat, but advised eating leaner meat in smaller and fewer portions than is customary in the United States.

How can I become a vegetarian? People become vegetarians for a number of reasons, including weight control, improved health, religion, love for all animals, protecting the environment, and taste preferences. Choosing to adopt a vegetarian diet is up to the individual and represents a significant change in dietary habits. Anyone desiring to make an abrupt change to a vegetarian diet should do some serious reading on the matter beforehand. Once you have done some reading on vegetarianism, there may be several ways to gradually phase yourself into a vegetarian diet. • You may become a part-time vegetarian simply by eating less red meat. For example, you may have several meatless meals each day by skipping the ham or sausage at breakfast and having a big salad for lunch. Eventually, you may move toward having several meatless days per week, possibly incorporating vegetarian “meats” such as meatless chicken, meatless smoked turkey, or tasty veggie burgers in your meals. • You may become a semivegetarian, substituting white meat such as chicken and turkey breast, with its generally lower fat content, for red meat. You may become a pescovegetarian, eating fish as your main animal food. • You may wish to become an ovolactovegetarian, eating eggs and dairy products. These excellent sources of complete protein can be blended with many vegetable products or eaten separately. • You may use the above methods as forerunners to a strict vegan diet, gradually phasing out animal products altogether as you

TABLE 2.13

Food colors of various fruits and vegetables

Red

Yellow/orange

Green

Blue/purple

White/brown

Cherries Cranberries Raspberries Red cabbage Red grapes Strawberries Tomatoes Watermelon

Apricots Cantaloupe Corn Carrots Lemons Mangos Oranges Pineapple

Artichokes Avocados Collards Cucumbers Green grapes Kiwi fruit Lettuce Spinach

Blackberries Blueberries Dried plums Eggplant Plums Purple cabbage Purple grapes Raisins

Bananas Cauliflower Garlic Jicama Onions Pears Potatoes Turnips

C H A P T E R 2 Healthful Nutrition for Fitness and Sport

learn to select and prepare vegetable foods to obtain protein complementarity and adequate intake of essential nutrients. The following simple suggestions may help you incorporate more fruits, vegetables, and whole grains in your diet. • Keep 100-percent fruit juices available, but limit those which provide few nutrients, such as apple and white grape juice. • Buy only bread products that list whole wheat as the first ingredient on the food label. • Keep a variety of raw fruits handy for snacks, such as bananas, grapes, apples, and oranges. • Keep a bowl of raw vegetables in the refrigerator, such as small carrots, cut-up celery, broccoli, cauliflower, and radishes, along with a tasty dip, for handy snacks. • Use frozen vegetables for quick stir-fry meals. • Add vegetables, such as onions, tomatoes, lettuce, spinach, and peppers, to your sandwiches. • Load up on fresh vegetables at the supermarket salad bar, putting meal-sized portions in small containers to take for lunch during the week. • Add cut-up vegetables to canned beans, soups, or omelets to increase their nutrient value. • Use your microwave to cook sweet potatoes and baked potatoes, and to steam vegetables with a little water. • Bake fruits for dessert. The scope of this book does not permit a discussion of food preparation. A number of excellent cookbooks for vegetarian meals are available at local bookstores, the titles of which may be obtained from a local dietician or local branch of the American Heart Association. These cookbooks provide the vegetarian with a variety of appetizing recipes that not only incorporate complementary proteins with a balance of vitamins and minerals but also make vegetarianism a gastronomical delight. An excellent example is the Vegetarian Times Complete Cookbook. www.goveg.com www.thevegetariansite.com www.vegan.com Learn how to become a vegetarian with useful guidelines.

Will a vegetarian diet affect physical performance potential? As noted previously, a diet that follows vegetarian principles is considered to be more healthful than the typical American diet today. But will such a diet have any significant impact upon physical performance? In a recent review of nutritional considerations for vegetarian athletes, Barr and Rideout noted that well-controlled long-term studies assessing the effects of vegetarian diets on athletes have not been conducted. Nevertheless, based on their review and the reviews of others such as Venderley and Campbell, the following observations can be made. • Well-planned, appropriately supplemented vegetarian diets appear to effectively support athletic performance. Including









fortified foods, such as soy milk and whole-grain cereals, may help provide adequate amounts of some vitamins and minerals that may be low in vegetarian diets. Plant and animal protein sources appear to provide equivalent support to athletic training and performance provided protein intakes are adequate to meet needs for total nitrogen and the essential amino acids. Vegetarian athletes (particularly women) are at increased risk for non-anemic iron deficiency, which may limit endurance performance. Vegetarian diets may be low in creatine, and thus vegetarian athletes may have lower muscle creatine concentrations than meat-eating athletes. Lower creatine levels may impair veryhigh intensity exercise. Details are presented in chapter 6. Vegetarian diets may be high in healthful carbohydrates and be effective for weight control, which could be to the advantage of some athletes, particularly endurance runners. However, if used improperly as a strategy for weight control, vegetarian diets could lead to eating disorders and impaired performance and health, a topic discussed in chapter 10.

Some world-class athletes have been vegetarians, and on occasion their diets have been cited as a reason for their success. On the other hand, there are a far greater number of world-class athletes who eat a balanced diet including animal products. Both types of diet may supply the nutrients necessary for the physically active individual if foods are selected properly. However, as noted previously, if you want to shift toward a vegetarian diet, you would need to do some careful reading beforehand and then initiate the process gradually. During the process, you should listen to your body—a common phrase among many athletes today. If you are active, how do you feel during your workouts? Do you have more or less stamina? Are you gaining or losing weight? Is your physical performance getting better or worse? The answers to these questions, together with other body reactions, may offer you some feedback as to whether the dietary change is beneficial. Remember, there is nothing magical about a vegetarian diet that will increase your physical performance capacity. It can be a healthful way to obtain the nutrients your physically active body needs, but so too is a well-balanced diet containing animal products.

Ke y C o n c e p t s 䉴 Vegetarians must be careful in selecting foods in order to obtain

a balanced mixture of amino acids and adequate amounts of B12, calcium, iron, and zinc. 䉴 Vegetarian diets are based on healthful nutritional concepts that may help reduce chronic disease, particularly cardiovascular disease, but nonvegetarian diets may confer similar health and performance benefits if limited animal foods are carefully chosen.

C h e c k f o r Yo u r s e l f If you are not a vegetarian, eat a vegetarian diet for a day or two to see if it may fit into your lifestyle.

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Consumer Nutrition— Food Labels and Health Claims Guidelines for a healthful diet will not be effective unless people change their behavior to buy and eat healthier foods. A model often used to explain the development of a set of behaviors involves a sequence of (1) acquisition of knowledge, (2) formation of an attitude or set of values, and (3) development of a particular behavior. In this sequence, knowledge is the first step that may enhance the development of proper health behaviors. Knowing how to interpret food labels may guide you in developing a nutritious, safe, and healthful diet.

What nutrition information do food labels provide? Food manufacturers view labels as a device for persuading you to buy their product instead of a competitor’s product. Just walk down the cereal aisle next time you visit the supermarket and notice the bewildering number of choices. As manufactured food products multiplied over the years, and as competition for your food dollar intensified, food companies began to manipulate their labels to enhance sales. Unfortunately, many of these practices were deceptive, and the consumer had a difficult time determining the nutritional quality of many processed foods. Thus, Congress passed a law designed to establish a set of standards to help Americans base their food choices on sound nutritional information. This set of standards resulted in nutritional labeling, whereby major nutrients found in a food product must be listed on the label. It is not the total solution to the problem of poor food selection existing among many Americans, but combined with an educational program to increase nutritional awareness, it may effectively improve the nutritional health of our nation. Initial food labeling legislation was passed in 1973, but it contained numerous flaws. Because of pressure from a variety of consumer interest groups, a major overhaul of the nutritional labeling program was signed into law as the Nutrition Labeling and Education Act in 1990, and it was in full effect in 1994. Under this law, nutrition labeling is mandatory for almost all foods regulated by the Food and Drug Administration (FDA). However, there are some exceptions. Food produced by very small businesses; food served in restaurants, hospital cafeterias, and airplanes; ready-to-eat food prepared primarily on site; and several other categories are exempt from these regulations. Other modifications may be used for children under the age of 2, and others for children under the age of 4. Additionally, providing nutrition information is currently voluntary for many raw foods such as fresh fruits, vegetables, meat, and fish, but may become mandatory in the future. 60

The food label illustrated in figure 2.10 is called Nutrition Facts, and it is designed to provide information on the nutrients that are of major concern for consumers. Food labels must contain the following information: List of ingredients Ingredients will be listed in descending order by weight. Serving size Serving size has been standardized. Servings per container Amount per serving of the following: Total Calories Calories from fat Total fat Saturated fat Trans fat Cholesterol Sodium Total carbohydrate Dietary fiber Sugars Protein Vitamin A Vitamin C Calcium Iron The following are optional: Calories from saturated fat Polyunsaturated fat Monounsaturated fat Potassium Soluble fiber Insoluble fiber Sugar alcohols Other carbohydrates Vitamins D, E, K All B vitamins

Phosphorus Magnesium Zinc Selenium Copper Manganese Molybdenum Iodine Potassium Chloride

How can I use this information to select a healthier diet? The Daily Value (DV), which is based on dietary standards discussed earlier in this chapter, represents how much of a specific nutrient you should obtain in your daily diet. DVs have been established for macronutrients and micronutrients that may affect our health. In essence, a food label indicates how much of a given nutrient is present in that product, and for some nutrients, what percentage of the DV is provided by one serving. The DVs cover the macronutrients that are sources of energy, consisting of carbohydrate (including fiber), fat, and protein, as well as cholesterol, sodium, and potassium, which contain no Calories. The DVs for the energy-producing nutrients are based on the number of Calories consumed daily. On the food label, the percent of the DV that a single serving of a food contains is based on a 2,000 Calorie diet, which has been selected because it is believed to have the greatest public health benefit for the nation. However,

C H A P T E R 2 Healthful Nutrition for Fitness and Sport: The Consumer Athlete

Serving size is listed in household units (and grams). Pay careful attention to serving size to know how many servings you are eating: e.g., If you eat double the serving size, you must double the % Daily Values and calories. The % Daily Values shows how a food fits into an overall 2000-kcal daily diet. Nutrient claims, such as “Good source,” and health claims, such as “Reduce the risk of osteoporosis,” must follow legal definitions.

There is no % Daily Values for sugar. Limiting intake is the best advice. % Daily Value for protein is generally not included due to expensive testing required to determine protein quality.

A Quick Guide to Nutrient Sources % Daily Value 20% or more = High source 10% –19% = Good source 0% –5% = Low source

The package must include the name and address of the food manufacturer.

Only vitamin A, vitamin C, calcium, and iron are required to be listed on the label.

Ingredients are listed in descending order by weight.

F I G U R E 2 . 1 0 The Nutrition Facts panel on a current food label.This nutrition information is required on virtually all processed food products.The % Daily Value listed on the label is the percentage of the generally accepted amount of a nutrient needed daily that is present in one serving of the product. See text for additional discussion.

the DV may be higher or lower depending on your Calorie needs. Values for some of the macronutrients are also provided for a 2,500 Calorie diet on the food label. The DVs are based on certain minimum and maximum allowances, including the following for a 2,000 Calorie diet: Total fat: Maximum of 30 percent of Calories, or less than 65 grams. Saturated fat: Maximum of 10 percent of Calories, or less than 20 grams. Carbohydrate: Minimum of 60 percent of Calories, or more than 300 grams.

Protein: Based on 10 percent of Calories. Applicable only to adults and children over age 4; 50 grams for a 2,000 Calorie diet. Fiber: Based on 12.5 grams of fiber per 1,000 Calories. Cholesterol: Less than 300 milligrams. Sodium: Less than 2,400 milligrams. The DVs for vitamins and minerals, based on previously established RDA, are presented in table 2.14. The list includes those whose listing is mandatory and some selected others. Although the RDA for several nutrients has changed with recent DRI updates, the DVs are still based on 1968 standards of the RDA. However, the Food and Drug Administration, along with Health Canada, is www.mhhe.com/williams9

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TABLE 2.14 DVs for protein, dietary fiber, and Some

vitamins and minerals on food labels Mandatory listing Protein Vitamin A Vitamin C Calcium Iron Dietary Fiber

56 grams 5,000 IU; 1 milligram 60 milligrams 1,000 milligrams 18 milligrams 25 grams

Optional listing Thiamin Riboflavin Niacin Vitamin D Vitamin E Vitamin B6 Folic acid Vitamin B12 Zinc Copper Magnesium

1.5 milligrams 1.7 milligrams 20 milligrams 400 IU 30 IU 2 milligrams 400 micrograms 6 micrograms 15 milligrams 2 milligrams 400 milligrams

collaborating with the Institute of Medicine in the process of revamping current food labels, changing the DV for various nutrients and focusing on caloric content. For example, one proposal is to reduce the DV for iron from 18 to 8 milligrams and another is to develop a DV for Calories and to list caloric content on the front of the label. Some important points to consider in reading a food label are as follows: 1. The DV for a nutrient represents the percentage contribution one serving of the food makes to the daily diet for that nutrient based on current recommendations for healthful diets. A lower DV is desirable for total fat, saturated fat, cholesterol, and sodium; a DV of 5 percent or less is a good indicator. There is no DV for trans fat; only the number of grams is listed, and intake should be as low as possible, preferably 0 grams. A higher DV is desirable for total carbohydrates, dietary fiber, iron, calcium, vitamins A and C, and other vitamins and minerals that may be listed, with 10 percent or more representing a good source. 2. To calculate the percentage of fat Calories in one serving, divide the value for Calories from fat by the total Calories and multiply by 100. For example, if one serving contains 70 Calories from fat and the total number of Calories is 120, the food consists of 58 percent fat Calories (70/120 × 100). It should be noted that this percentage is not the same as the DV percentage for fat, which is based on your total daily diet, not an individual serving of the food product. 3. Related to carbohydrates, sugars include both natural and added sugars. Dietary fiber is the total amount of fiber per serving. Other carbohydrates represent total carbohydrates minus sugars and dietary fiber. 62

4. Be aware of serving size tricks. A serving size for a cola drink may be 8 ounces (100 Calories), so a 20-ounce bottle of soda is 2.5 servings (250 Calories). However, most people drink it all at one time, thinking it is only one serving and may consume more than twice the Calories as expected. Recommended changes are to provide nutrition information for a single serving as well as for the entire package; so for a 20-ounce bottle of soda, you will get the nutrition breakdown for 8 ounces as well as for the entire 20 ounces. Labels also must disclose certain ingredients, such as sulfites, certain food dyes, and eight food allergens, so food-sensitive consumers may avoid foods that may cause allergic responses. Others may be added as deemed necessary. Food allergies are discussed later in this chapter. In the past, many terms used on food labels, such as “lean” and “light,” had no definite meaning. However, under the new regulations, most terms used have specific definitions. A summary of these terms is presented in table 2.15. Additionally, new milk labels are based on fat content, expressed as percent or grams of fat, as follows: fat-free, skim, or nonfat milk (0 grams); low-fat or light milk (1% or 2.5 grams); reduced fat milk (2% or 5 grams); and whole milk (3.5% or 8 grams). In a recent survey, Rothman and others reported that many Americans, even well-educated individuals with good literacy and math skills, do not know how to interpret food labels. However, other studies have shown that reading food labels carefully helps individuals to limit their fat intake, one of the most significant changes we can make in our diet. Individuals with high blood pressure have also used food labels to reduce their consumption of sodium, a dietary risk factor for some. Take time to learn to read food labels; it’s a smart thing to do. www.cfsan.fda.gov/labelman The FDA provides a program, Make Your Calories Count, featuring the animated character Labelman, to help people read food labels to plan a healthy diet while balancing caloric intake.

What health claims are allowed on food products? Food manufacturers want your business. Given the public’s growing awareness of the relationship between nutrition and health, many food labels now list various health claims that may entice you to buy that product. And consumers do view a food product as healthier if it carries a health claim. The FDA permits food manufacturers to make specific health claims on food labels only if the food meets certain minimum standards. These health claims are permitted because the FDA believes there may be significant scientific agreement supporting a relationship between consumption of a specific nutrient and possible prevention of a certain chronic disease. However, there are several requirements, such as not stating the degree of risk reduction, using only terms such as “may” or “might” in reference to reducing health risks, and indicating that other foods may provide similar benefits. Figure 2.11 provides an example.

C H A P T E R 2 Healthful Nutrition for Fitness and Sport: The Consumer Athlete

TABLE 2.15

Definitions for comparative and absolute nutrient claims on food labels

Sugar • Sugar free: less than 0.5 g per serving • No added sugar; without added sugar; no sugar added: • No sugars were added during processing or packing, including ingredients that contain sugars (for example, fruit juices, applesauce, or jam). • Processing does not increase the sugar content above the amount naturally present in the ingredients. (A functionally insignificant increase in sugars is acceptable for processes used for purposes other than increasing sugar content.) • The food that it resembles and for which it substitutes normally contains added sugars. • If the food doesn’t meet the requirements for a low- or reduced-Calorie food, the product bears a statement that the food is not low Calorie or Calorie reduced and directs consumers’ attention to the Nutrition Facts panel for further information on sugars and Calorie content. • Reduced sugar: at least 25% less sugar per serving than reference food Calories • Calorie free: fewer than 5 kcal per serving • Low Calorie: 40 kcal or less per serving and, if the serving is 30 g or less or 2 tbsp or less, per 50 g of the food • Reduced or fewer Calories: at least 25% fewer kcal per serving than reference food Fiber • High fiber: 5 g or more per serving. (Foods making high-fiber claims must meet the definition for low fat, or the level of total fat must appear next to the high-fiber claim.) • Good source of fiber: 2.5 to 4.9 g per serving • More or added fiber: at least 2.5 g more per serving than reference food Fat • Fat free: less than 0.5 g of fat per serving • Saturated fat free: less than 0.5 g per serving, and the level of trans fatty acids does not exceed 0.5 g per serving • Low fat: 3 g or less per serving and, if the serving is 30 g or less or 2 tbsp or less, per 50 g of the food. 2% milk can no longer be labeled low-fat, as it exceeds 3 g per serving. Reduced fat is the term used instead. • Low saturated fat: 1 g or less per serving and not more than 15% of kcal from saturated fatty acids

• Reduced or less fat: at least 25% less per serving than reference food • Reduced or less saturated fat: at least 25% less per serving than reference food Cholesterol • Cholesterol free: less than 2 mg of cholesterol and 2 g or less of saturated fat per serving • Low cholesterol: 20 mg or less cholesterol and 2 g or less of saturated fat per serving and, if the serving is 30 g or less or 2 tbsp or less, per 50 g of the food • Reduced or less cholesterol: at least 25% less cholesterol and 2 g or less of saturated fat per serving than reference food







Sodium • Sodium free: less than 5 mg per serving • Very low sodium: 35 mg or less per serving and, if the serving is 30 g or less or 2 tbsp or less, per 50 g of the food • Low sodium: 140 mg or less per serving and, if the serving is 30 g or less or 2 tbsp or less, per 50 g of the food • Light in sodium: at least 50% less per serving than reference food • Reduced or less sodium: at least 25% less per serving than reference food Other Terms • Fortified or enriched:Vitamins and/or minerals have been added to the product in amounts in excess of at least 10% of that normally present in the usual product. Enriched generally refers to replacing nutrients lost in processing, whereas fortified refers to adding nutrients not originally present in the specific food. • Healthy: An individual food that is low fat and low saturated fat and has no more than 360 to 480 mg of sodium or 60 mg of cholesterol per serving can be labeled “healthy” if it provides at least 10% of the Daily Value for vitamin A, vitamin C, protein, calcium, iron, or fiber. • Light or lite: The descriptor light or lite can mean two things: first, that a nutritionally altered product contains one-third fewer kcal or half the fat of reference food (if the food derives 50% or more of its kcal from fat, the reduction must be 50% of the fat) and, second, that the sodium content of a low-calorie, low-fat food has been reduced by 50%. In addition,“light in sodium” may be used for foods in which the sodium content has been reduced by at least 50%.The term light



may still be used to describe such properties as texture and color, as long as the label explains the intent—for example,“light brown sugar” and “light and fluffy.” Diet: A food may be labeled with terms such as diet, dietetic, artificially sweetened, or sweetened with nonnutritive sweetener only if the claim is not false or misleading.The food can also be labeled low calorie or reduced calorie. Good source: Good source means that a serving of the food contains 10 to 19% of the Daily Value for a particular nutrient. If 5% or less of it is a low source. High: High means that a serving of the food contains 20% or more of the Daily Value for a particular nutrient. • Organic: Federal standards for organic foods allow claims when much of the ingredients do not use chemical fertilizers or pesticides, genetic engineering, sewage sludge, antibiotics, or irradiation in their production. At least 95% of ingredients (by weight) must meet these guidelines to be labeled “organic” on the front of the package. If the front label instead says “made with organic ingredients,” only 70% of the ingredients must be organic. For livestock, the animals need to be allowed to graze outdoors and as well be fed organic feed.They also cannot be exposed to large amounts of antibiotics or growth hormones. Natural: The food must be free of food colors, synthetic flavors, or any other synthetic substance.

Milk • Fat-free, skim, or nonfat: Contains 0 grams of fat • Low-fat or light: Contains 1% or 2.5 grams of fat • Reduced fat: Contains 2% or 5 grams of fat • Whole: Contains 3.5% or 8 grams of fat The following terms apply only to meat and poultry products regulated by USDA. • Extra lean: less than 5 g of fat, 2 g of saturated fat, and 95 mg of cholesterol per serving (or 100 g of an individual food) • Lean: less than 10 g of fat, 4.5 g of saturated fat, and 95 mg of cholesterol per serving (or 100 g of an individual food)

Many definitions are from FDA’s Dictionary of Terms, as established in conjunction with the 1990 Nutrition Education and Labeling Act (NELA).

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What are functional foods?

F I G U R E 2 . 1 1 An example of a Nutrition Fact food label with an approved health claim. Credit: Sabina Dowell

The FDA ranks health claims for food labels based on the quality of the underlying scientific evidence. In brief, the following system is used: A—Significant scientific evidence supports the claim. B—Scientific evidence supports the claim, but the evidence is not conclusive. C—Some scientific evidence supports the claim, but the evidence is limited and not conclusive. D—Little scientific evidence supports the claim. The current FDA-approved model for A-level health claims, or qualified health claims, is presented in table 2.16. The FDA also may approve a “qualified health claim” for food products that evidence suggests, but does not prove, may reduce disease risk. One example is omega-3 fatty acids and reduced risk of coronary heart disease. www.fda.gov In the search box type in “Qualified Health Claims” to obtain details on currently approved health claims for food labels.

Although food labeling in the United States continues to improve to help us select healthier foods, many still find it is too complex. Some countries, such as Sweden and Great Britain, have a national system that uses traffic light symbols (Red = High; Yellow = Medium; Green = Low) to instantly highlight the contents of less healthy ingredients, such as fat, saturated fat, sugars, and sodium. Consumer groups in the United States have petitioned the FDA to develop a similar national system for supermarkets. The FDA is currently considering major changes to the current Nutrition Facts label, but has not set any timetable. In the meantime, the FDA has a Website to help consumers use the food label to select healthier foods. Some food companies have already developed healthy food logos for their products, such as Kraft’s Sensible Solution, that help to identify healthier foods. www.cfsan.fda.gov/~dms/foodlab.html Consult for a detailed description on how to use the current Nutrition Facts food label to improve your dietary choices.

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In 1994, the FDA permitted dietary supplement manufacturers to make structure and function claims on their products. Basically, a structure and function claim simply means that the food product may affect body physiology in some way, usually in some way beneficial to health or performance. These claims may not be as authoritative as the FDA-approved claims cited above (such as reducing the risk of heart disease or cancer), but these claims may use such terminology as “helps to maintain healthy cholesterol levels” or “supports your immune system” that the consumer may interpret as preventing heart disease or cancer. Technically, these health claims must be correct, but they do not need to have as much supportive scientific evidence nor do they have to have approval from the FDA. Dietary supplements sales have skyrocketed in the last 15 years, and the food industry jumped on the bandwagon. In recent years, numerous food manufacturers, including some giants such as Kellogg, Tropicana, and Procter & Gamble, have marketed products that have been referred to as functional foods. Functional foods are food products designed to provide health benefits beyond basic nutrition, the benefits being attributed mostly to vitamins, minerals, phytochemicals, and herbals. Some refer to them as medical foods. Many natural foods have been modified in attempts to make them more healthful. For example, meat animals have been bred for lower fat content and plant fatty acid content has been altered to achieve desired ratios of beneficial fatty acids in the extracted oil. In its position stand, the American Dietetic Association indicated that functional foods, including whole foods and fortified, enriched, or enhanced foods, have a potentially beneficial effect on health when consumed as part of a varied diet on a regular basis. Indeed, some contend that in the future it may be possible to design foods and diets to help regulate gene expression that may enhance health. Fortification with nutrients or nutraceuticals is a current technique to make functional foods. In a sense, functional foods have been around for nearly a century, as salt was fortified with iodine, and milk was fortified with vitamins A and D, to help prevent nutrient deficiencies. More recently, calcium-fortified orange juice and multivitamin/mineral-fortified cereals are breakfast mainstays designed, in part, to help us obtain adequate amounts of specific nutrients. Some of these products may be worthwhile, for they may be in accord with the principles underlying FDA approval of food health claims. For example, the Consumers Union notes that calciumfortified orange juice may be an excellent source of calcium for someone who does not drink milk. Cereals fortified with psyllium may be an excellent source of soluble dietary fiber. On the other hand, a sugar drink with added vitamins is a different story, as it is simply a vitamin pill with added sugar. Some functional foods are designed to satisfy the criteria for qualified health claims on food labels. Many other products marketed as functional foods are simply dietary supplements in disguise, and use structure and function claims to suggest health benefits. Such products include soups with St. John’s wort, snack foods with kava kava, cereals with ginkgo biloba, and energy drinks with caffeine.

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TABLE 2.16 Qualified health claims. FDA-approved model health claims for foods

that have significant scientific evidence supporting the claim Calcium and osteoporosis: Regular exercise and a healthy diet with enough calcium helps teen and young adult white and Asian women maintain good bone health and may reduce their high risk of osteoporosis later in life. Dietary fat and cancer: Development of cancer depends on many factors. A diet low in total fat may reduce the risk of some cancers. Dietary saturated fat and cholesterol and risk of coronary heart disease: Development of heart disease depends upon many factors, but its risk may be reduced by diets low in saturated fat and cholesterol and healthy lifestyles. Dietary sugar alcohols and dental caries: Frequent eating of foods high in sugars and starches as between-meal snacks can promote tooth decay. The sugar alcohol used to sweeten this food may reduce the risk of dental caries. Fiber-containing grain products, fruits, and vegetables and cancer: Low fat diets rich in fiber-containing grain products, fruits, and vegetables may reduce the risk of some types of cancer, a disease associated with many factors. Folate and neural-tube defects (spina bifida): Healthful diets with adequate folate may reduce a woman’s risk of having a child with a brain or spinal cord birth defect. Fruits and vegetables and cancer: Low fat diets rich in fruits and vegetables (foods that are low in fat and may contain dietary fiber, vitamin A, and vitamin C) may reduce the risk of some types of cancer, a disease associated with many factors. Fruits, vegetables, and grain products that contain fiber, particularly soluble fiber, and risk of coronary heart disease: Diets low in saturated fat and cholesterol and rich in fruits, vegetables, and grain products that contain some types of dietary fiber, particularly soluble fiber, may reduce the risk of heart disease, a disease associated with many factors. Sodium and hypertension: Diets low in sodium may reduce the risk of high blood pressure, a disease associated with many factors. Soluble fiber from certain foods and risk of coronary heart disease: Soluble fiber from foods such as oats and barley, as part of a diet low in saturated fat and cholesterol, may reduce the risk of heart disease. A serving of this food supplies 0.75 gram of the soluble fiber from oats necessary per day to have this effect. Soy protein and risk of coronary heart disease: Diets low in saturated fat and cholesterol that include 25 grams of soy protein a day may reduce the risk of heart disease. One serving of this food provides 8 grams of soy protein. Plant sterol/stanol esters and risk of coronary heart disease: Foods containing at least 0.65 g per serving of plant sterol esters eaten twice a day with meals for a daily total intake of at least 1.3 g (or 1.7 g per serving of plant stanol esters for a total daily intake of at least 3.4 g) as part of a diet low in saturated fat and cholesterol may reduce the risk of heart disease. A serving of this food supplies 0.75 gram of vegetable oil sterol (stanol) esters. Source: U. S. Food and Drug Administration. Health Claims that Meet Significant Scientific Agreement.

In the next section we shall discuss dietary supplements and health claims. However, in the meantime, remember that fruits, vegetables, whole grains, and other plant foods are the optimal functional foods. Their health benefits have been well established.

Ke y C o n c e p t s 䉴 Information provided through nutritional labeling on most food

products may serve as a useful guide in finding foods that have a high nutrient density and are healthy choices. 䉴 The Daily Value (DV) for a single serving on a food label represents the percentage of a nutrient, such as saturated fat or carbohydrate, that is recommended for an individual who consumes 2,000 Calories daily. 䉴 Terms used on food labels, such as fat free, must meet specific standards. In this case, use of fat free indicates that a serving of the food contains less than 0.5 grams of fat.

䉴 Health claims may be placed on food labels only if they are

supported by adequate scientific data and have been approved by the Food and Drug Administration (FDA). 䉴 Some functional foods may provide some health benefits, adhering to qualified health claims. Other products marketed as functional foods may use structure and function claims, which do not have the scientific support of qualified health claims.

C h e c k f o r Yo u r s e l f Go to a supermarket and compare food labels for various products. In particular, compare the caloric content of some fat-free products with their non–fat-free counterparts to see the Calorie reduction, if there is any.

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Consumer Nutrition—Dietary Supplements and Health Nutrition scientists indicate that foods, particularly fruits and vegetables, contain numerous nutrients or other food substances that may have pharmaceutical properties when taken in appropriate dosages. The potential health benefits of specific nutrients will be covered in appropriate chapters. The purpose of this section is to provide a broad overview of possible health effects of dietary supplements.

What are dietary supplements? The dietary supplement industry is a multi-billion dollar business. According to Rock, about 40 percent of Americans use dietary supplements (figure 2.12). In the United States, the Dietary Supplement Health and Education Act (DSHEA) defines a dietary supplement as a food product, added to the total diet, that contains at least one of the following ingredients: • • • • • • • •

vitamin mineral herb or botanical amino acid metabolite constituent extract combination of any of these ingredients

It is important to note that the DSHEA stipulates that a dietary supplement cannot be represented as a conventional food or as the sole item of a meal or diet. As noted by this definition, dietary supplements may contain essential nutrients such as essential vitamins, minerals, and amino acids, but also other nonessential substances such as ginseng, ginkgo, yohimbe, ma huang, and other herbal products. The technical definition of a supplement is something added, particularly to correct a deficiency. Theoretically then, dietary supplements should be used to correct a deficiency of a specific nutrient, such as vitamin C. However, numerous dietary supplements contain substances other than essential nutrients and are marketed not to correct a deficiency, but rather to increase the total dietary intake of some food or plant substance that allegedly may enhance one’s health status. Like foods, dietary supplements must carry labels, or supplement facts; an example is presented in figure 7.5 on page 298.

Will dietary supplements improve my health? Dietary supplements are usually advertised to the general public as a means to improve some facet of their health, and are usually under governmental regulation. In the United States, dietary supplements are regulated under food law by the Food and Drug Administration (FDA), and thus are eligible for FDA-authorized health claims, as discussed previously. Dietary supplement health claims in Canada are governed by Health Canada’s Natural Health Products Directorate. In some countries, such as Germany, a med66

F I G U R E 2 . 1 2 Dietary supplements are marketed as a means of enhancing both health and physical performance.

ical prescription is needed to obtain some dietary supplements containing strong herbal products. Blendon and others noted that a substantial percentage of Americans regularly take dietary supplements as a part of their routine health regimen. Can dietary supplements improve your health? Possibly, but there are several caveats. In its position statement on dietary supplements, the American Dietetic Association (ADA) indicated that the best nutritional strategy for promoting health and reducing the risk of chronic disease is to wisely choose a wide variety of foods. Essential nutrients and phytochemicals found in most dietary supplements are readily available for us in fruits, vegetables, legumes, fish, and other healthy foods. However, the ADA also notes that additional vitamins and minerals from supplements can help some people meet their nutritional needs as specified by the Dietary Reference Intakes. Individuals such as the elderly, women of childbearing age, vegans, and those on weight-loss diets may not be obtaining adequate amounts of various vitamins and minerals. Fletcher and Fairfield note that most people do not consume an optimal amount of vitamins by diet alone. Such individuals may benefit from a daily multivitamin/mineral. However, consumers should be aware of exceeding recommended upper limits of some vitamins and minerals. The American Dietetic Association reinforces this viewpoint in their position statement. Some prudent recommendations for vitamin and mineral supplementation will be presented in chapters 7 and 8. In general, as shall be noted in chapter 6, individual amino acid supplements may not enhance health if adequate protein is consumed in the diet. However, research is ongoing with several amino acids.

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Of the other classes of nonvitamin, nonmineral dietary supplements (herb or botanical, metabolite, constituent, extract, or combinations), numerous products are marketed for their purported health benefits. In a recent survey of college students by Newberry and others, nearly 50 percent had used such supplements within the past year. Although we have no specific requirement for these substances as they are not essential for normal physiological function, some may affect physiological functions in the body associated with health benefits. Using a broad interpretation of the FDA health claim regulations for dietary supplements, some supplement companies advertise their supplements as “miracle products” that can produce “magical results” in a short period of time. The Consumers Union notes that, under current federal law, any dietary supplement can be marketed without advance testing. The only restriction is that the label cannot claim that the product will treat, prevent, or cure a disease. However, as noted previously, the label may make vague claims, referred to as structure/function claims, like “enhances energy” or “supports testosterone production.” Unfortunately, as Nesheim notes, for most of these dietary supplements there are few research data to support their claims. Most advertisements are based on theory alone, testimonials or anecdotal information, or on the exaggeration or misinterpretation of research findings relative to the health effects of specific nutrients or other food constituents. Many labels carry a notice stating that This statement has not been evaluated by the FDA, a disclaimer regarding their health claim. Moreover, although advertisers may not make unsubstantiated health claims, the 1994 DSHEA stipulates that the burden of proving the claims false rests with the government. Currently, under the DSHEA, the FDA must show in court that an unreasonable risk is posed by consumption of a dietary supplement. Thus, numerous unsupported health claims are being made in advertisements and even on dietary supplement labels. Help is on the way. The Center for Food Safety and Applied Nutrition of the FDA recently launched a ten-year plan to develop a science-based regulatory program that will provide consumers with a high level of confidence in the safety, composition, and labeling of dietary supplement products. The FDA has established current good manufacturing practice requirements noting that manufacturers are required to evaluate the identity, purity, quality, strength, and composition of dietary supplements. By 2010 the FDA intends to ensure that dietary supplements do not have too much or too little of a dietary ingredient, improper labeling, or contamination with bacteria, pesticide, or other toxic substances. The Federal Trade Commission recently indicated that marketers of dietary supplements must have above-board scientific evidence to support any health claims. Additionally, U.S. Pharmacopeia, a respected nonprofit medical agency, recently launched a certification program for dietary supplements. If the dietary supplement contains what the label indicates, then it may carry the USP seal of approval. However, the USP seal does not mean the product is effective or even that it is safe to use, just simply that it contains what the label promises. It should be noted that some of these types of dietary supplements, such as herbals and food extracts, have been the subject of recent research to evaluate their health effects. Such effects will be discussed in later chapters as appropriate.

Again, to reiterate the point, dietary supplements may exert some beneficial healthful effects in certain cases, but as Thomas points out, for most of us the substances found in most dietary supplements are readily available in familiar and attractive packages called fruits, vegetables, legumes, fish, and other healthy foods. Although the Prudent Healthy Diet is the optimal means to obtain the nutrients we need, dietary supplements may be recommended under certain circumstances. When deemed to be prudent behavior, such recommendations will be provided at specific points in this text.

Can dietary supplements harm my health? In his review of dietary supplements, Thomas noted that although they may be beneficial to some individuals their use may be harmful in some ways. Some of his key points, and others, are: 1. Nutrition is only one factor that influences health, well-being, and resistance to disease. Individuals who rely on dietary supplements to guarantee their health may disregard other very important lifestyle behaviors, such as appropriate exercise and a healthy diet. 2. Dietary supplements may provide a false sense of security to some individuals who may use them as substitutes for a healthful diet, believing they are eating healthfully and not attempting to eat right. 3. Taking supplements of single nutrients in large doses may have detrimental effects on nutritional status and health. Although large doses of some vitamins or minerals may be taken to prevent some conditions, excesses may lead to other health problems. 4. Individuals who use dietary supplements as an alternative form of medicine may avoid seeking effective medical treatment. 5. Dietary supplements vary tremendously in quality. Numerous independent analyses of specific dietary supplements, such as those by ConsumerLab.com, reveal that some may contain less than that listed, sometimes even none of the main ingredient. Some products often contain substances not listed on the label. This may pose a health risk. 6. Numerous case studies have shown that the use of various dietary supplements may impair health, and may even be fatal. Use of ephedrine-containing dietary supplements for weight loss have resulted in deaths. www.ConsumerLab.com Check the content analysis of various brands of popular dietary supplements. Fee charged for some reports. www.ods.od.nih.gov/factsheets Provides detailed information on specific dietary supplements. http://dietarysupplements.nlm.nih.gov Check dietary supplements by specific brands or active ingredient. Indicates uses for the product. Provides list of research studies regarding effectiveness.

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as Germany, herbs are approved for medical use by agencies comparable to the U.S. FDA. On the other hand, in a recent Consumers Union report various herbal preparations were associated with stomach disorders, nonviral hepatitis (rapid liver damage), obstructed blood flow to the liver and possible cirrhosis, and even death. Where appropriate, the effectiveness and safety of various dietary supplements will be discussed in later sections of this book, but some general safeguards recommended by the Consumers Union to protect your health represent sound advice. • Before trying a dietary supplement to treat a health problem, try changing your diet or lifestyle first. • Check with your doctor before taking any dietary supplement, particularly herbal preparations. This is especially important for pregnant and nursing women, children, and individuals taking prescribed drugs whose effects may be impaired by herbal interactions. • Buy standardized products. Most dietary supplements in the United States should be standardized according to federal regulations. “Supplement Facts” labels should provide information comparable to the “Nutrition Facts” food label. • Use only single-ingredient dietary supplements. Use of combination supplements may make it difficult to determine the cause of any side effects. • Be alert to both the positive and negative effects of the supplement. Try to keep an objective record of the effects. • Stop taking the supplement immediately if you experience any health-related problems. Contact your physician and local health authorities to report the problem. This may help establish a database for the safety of dietary supplements.

Ke y C o n c e p t s 䉴 As defined by the Dietary Supplement Health and Education

Act (DSHEA) a dietary supplement is a food product, added to the total diet, that may contain vitamins, minerals, herbs or botanicals, amino acids, metabolites, constituents, extracts, or any combination of the above. 䉴 Although some people may need dietary supplements for various reasons, particularly vitamins and minerals, the use of supplements should not be routine practice for most individuals. Obtain nutrients through natural foods.

Consumer Nutrition— Food Quality and Safety We Americans and Canadians have the basic assumption that the food we eat is safe and of high quality. Several federal agencies, such as the FDA’s Center for Food Safety and Applied Nutrition, effectively regulate food quality and safety, so in general this assumption is correct. However, foods are not necessarily risk free or high quality. Many factors may influence food quality and safety in the development of a food product. For example, from the time a plant seed is created until the final food product hits our kitchen 68

table, the food may have been treated with plant chemicals, loaded with additives, contaminated with bacteria, or prepared improperly, all of which may affect food quality and safety. Food safety is an important consideration in healthful eating, and thus has been included in the 2005 Dietary Guidelines for Americans. The purpose of this section is to discuss several of the major factors and concerns influencing food quality and safety in developed nations. www.foodsafety.gov Represents the gateway to food safety information presented by the FDA.

Is current food biotechnology effective and safe? Food biotechnology has been around for thousands of years as farmers used plant breeding techniques to enhance desired traits, such as the ability of plants to produce higher yields or to resist pests and diseases. Today, genetic engineering, which involves the insertion of favorable genes into plants or animals, is a key feature of food biotechnology. Genetically engineered (GE) foods are also known as genetically modified (GM) foods. Ackerman noted that genetic engineering is designed to enhance human nutrition in both developing and developed countries. Genetic engineering may enable the production of greater quantities of foods or prevention of food spoilage to meet the needs of the world’s growing population without damaging the environment. Genetic engineering may also enhance food quality by increasing the nutrient content. For example, rice could be designed to contain more beta-carotene, a precursor to vitamin A, and help prevent several million deaths per year that are caused by vitamin A deficiency. Fish, such as salmon, could be engineered to grow much faster and larger, producing a source of high-quality, healthful protein. Although GM plants and animals are designed to enhance food quality, the technique has raised some public concern over the safety of GM foods. In a recent review, the International Food Information Council (IFIC) discussed some myths and facts about genetic engineering of plants. In the United States, since 1992 the FDA determined that crops produced by biotechnology must meet the same rigorous standards for safety as those created through traditional means. Although nutrition scientists indicate that there is no such thing as “zero risk” for any food, the scientific consensus is that the risks associated with food biotechnology products are basically the same as for other foods. Bioengineered foods are regulated by three federal agencies, the FDA, the USDA, and the Environmental Protection Agency (EPA). The IFIC notes that consumers can be confident that foods produced through genetic engineering meet the government’s most stringent safety standards, and the FDA is not aware of any information that bioengineered foods differ from conventional foods in quality, safety, or any other characteristic. Although most of us are probably unaware of the fact, we have eaten GM products. About 70 percent of foods in a typical supermarket contain at least one GM ingredient, typically from corn or soybeans. Are they safe for us to eat? In her review, Ackerman answers this question with the response, “Yes, as far as we know.” In its review, the Center for Science in the Public Interest (CSPI) also indicated that GM foods currently on the market are safe.

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However, Ackerman notes that although GM foods represent a field of promise, they are also a subject of debate. Critics fear that GM products have been marketed without adequate research. One of the key problems with GM foods may be the development of a protein that may cause an allergic response in some individuals. Another concern is the possible long-term effect on children. Thus, although GM foods are generally regarded as safe for the present, the CSPI also notes that governmental agencies should become increasingly involved to help assure safety in the future. One possible future action may be to mandate labeling of GM foods. Currently, genetically modified (GM) foods need not be identified on food labels in the United States unless the food is significantly different in nutrient content from its conventional counterpart, unless a known food allergen has been introduced, or unless the food is to be exported. GM foods must be identified on food labels in the European Union.

Do pesticides in food present significant health risks? Modern production techniques are designed to increase both the quantity and quality of plant and animal food and yet maintain appropriate safety standards. One potential problem is bacterial contamination, discussed later, and another is the potential health risks of pesticides. As noted previously, plants contain substances called phytochemicals, which may contribute to various health benefits associated with a diet high in fruits, vegetables, and other wholesome plant foods. Many of these phytochemicals also help the plant survive, primarily by acting as herbicides or pesticides to prevent damage from naturally occurring weeds and insects. Nevertheless, over two thousand insects, weeds, or plant diseases damage nearly onethird of our nation’s farm crop each year. To help minimize crop damage from these pests, agriculturalists have developed synthetic herbicides and pesticides to augment plants’ natural defenses. Although synthetic herbicides and pesticides may effectively control weeds and pests harmful to plants, they appear to function differently in the human body than do natural plant phytochemicals. Synthetic chemicals may cause health problems. A number of illnesses, including cancer and nervous system disorders, along with genetic mutations, birth defects, miscarriages, and deaths, have been attributed to prolonged exposure to these chemicals. On the one hand, we need to control those pests destructive to our food supply, but on the other hand, the health of the public should not be harmed by the chemicals being used. This is the dilemma concerning the use of pesticides and similar chemicals. Most of the serious diseases from pesticide use have been associated with occupational exposure, such as in farm workers and crop-dusting pilots, who may be exposed to high concentrations on a daily basis, or in people who live near sprayed areas. However, direct exposure to even small amounts of household insect spray has been known to alter brain function, causing irritability, insomnia, and reduced concentration. The prudent individual should avoid direct contact with these substances as much as possible, for even thorough washing with soap and water has little effect upon the absorption through the skin of some insect sprays. Ames and Gold note that 99.99 percent of the pesticides we eat are naturally present in plants, but synthetic pesticides may also be

on the food we eat and in the water we drink. The FDA and state government agencies conduct spot surveys to analyze the pesticide content of produce for sale. In a recent report that analyzed data on more than 200 known carcinogens in foods, the National Research Council of the National Academy of Sciences concluded that both synthetic and naturally occurring pesticides are consumed at such low levels that they pose little threat to human health. Moreover, in its recent comprehensive, worldwide review, the American Institute for Cancer Research found no convincing evidence that eating foods containing trace amounts of chemicals, such as pesticides and herbicides, and drugs used on farm animals, changes our risk for cancer. There is increasing concern that children may be exposed to higher levels of pesticides because children are smaller and normally consume greater amounts of fruits and vegetables per unit of body weight. However, available evidence is inconclusive. Weiss and others have noted that in the absence of direct conclusive evidence, some observations have led some investigators to infer that chronic low-dose exposure to certain pesticides may pose a potential hazard to the health and development of infants and children, but others have noted such inferences can be neither supported nor refuted at the present time. Nevertheless, the impact of pesticides on the developing brain and nervous system is a concern, and health professionals recommend baby foods contain no pesticides. Government agencies are attempting to reduce pesticide residues in the food we eat, and more farmers are turning to pesticide-free farming, producing more organic foods certified to be free of any pesticide residue. Genetically engineered plants may also reduce the need for pesticides. According to Needham and others, these efforts are working as the level of environmental chemicals in humans is decreasing. Unfortunately, at the present time there is little understanding of how varying levels of pesticide exposure will affect human health. Scientists note the difficulty in studying the effects of pesticides on neurological development during infancy and childhood. Based on current knowledge, the following points appear to be sound advice to help reduce, but may not completely eliminate, the pesticide content in the foods we eat. 1. Avoid direct skin contact or breathing exposure to pesticides. 2. Food preparation may reduce pesticide residues. Wash produce thoroughly; some, but not all, pesticides on fruits and vegetables are water soluble. Washing may be particularly helpful to remove pesticide residues from apples, bananas, corn, grapes, lettuce, peaches, and tomatoes. Peeling some fruits and vegetables also helps. Peeling is effective for apples, carrots, cucumbers, grapes, oranges, peaches, and potatoes. Remove outer leaves of produce. Cooking may also help, particularly with broccoli, green beans, potatoes, and tomatoes. 3. Eat less animal fat and seafood from contaminated waters. Pesticides may concentrate in animal fat. In particular, farmed fish such as Atlantic salmon may contain high concentrations of several contaminants. 4. Buy fruits and vegetables locally and in season. Farmers are less likely to use pesticides if the food is to be sold locally. 5. Eat a wide variety of foods. A food that contains pesticides will then contribute only a small amount as part of your overall diet. www.mhhe.com/williams9

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6. Buy certified organic foods because they contain fewer pesticide residues than conventionally grown alternatives. An environmental research agency recently categorized fruits and vegetables based on their pesticide levels, including a clean dozen and a dirty dozen (see table 2.17). If you want the least pesticides in your diet, you might consider choosing organic alternatives for the dirty dozen. www.foodnews.org Provides a complete list of forty-five fruits and vegetables ranked on level of pesticides from highest to lowest amount.

Are organic foods safer and healthier choices? The USDA has established rules regarding certified organic foods. One stipulation is prohibition of certain synthetic pesticides and fertilizers in plant production. Additionally, the use of antibiotics and growth hormones in animal production are prohibited, as is the use of irradiation and genetically modified organisms. Foods that are 95–100 percent organic can carry the USDA organic label (see table 2.15), while foods with the notation “Made With Organic Ingredients” must contain at least 70 percent organic ingredients, but cannot use the organic label. Are such foods safer or healthier? Let’s look at several proposed differences between organic and conventional food products. Pesticides Baker and others, analyzing data representing over 94,000 food samples, concluded that organically grown foods have fewer and generally lower pesticide residues than conventionally grown foods. However, Magkos and others note that although organic foods may contain less pesticide residues than conventionally grown foods, the significance of this difference is questionable, inasmuch as actual levels of contamination in both types of food are generally well below acceptable limits. This is especially so with the clean dozen fruits and vegetables. Most health professionals agree that you should not cut back on fruits

and vegetables because the associated health benefits discussed previously far outweigh potential risks from pesticides. Bacteria Bacteria levels in organic foods are comparable to those in conventional foods. The Center for Science in the Public Interest indicated that organic fruits or vegetables are no less likely to be contaminated with bacteria, such as E. coli, than conventional ones. The Consumers Union also notes that chickens labeled as organic were more likely to harbor salmonella bacteria than were conventionally produced broilers. Magkos and others indicate that what should be made clear is that organic does not automatically equal safe. However, the Centers for Disease Control and Prevention indicated that there is no evidence that foodborne diseases, such as food poisoning, are a greater or lesser risk with organic foods. As discussed later in this chapter, food poisoning may have serious health consequences. Nutritional Value The British Nutrition Foundation indicates that there is no strong scientific evidence to show that crops grown organically have a better nutrient content than those produced nonorganically. Conversely, Worthington noted that there appear to be genuine differences in the nutrient content of organic and conventional foods, with higher amounts of vitamin C, iron, and magnesium in organic foods. Moreover, organic meat may have a different fatty acid profile because of the differences in the diet provided for the animals. The Consumers Union notes that as more companies enter the organic market, government standards come under attack. Today we have numerous organic products in the marketplace, some of which have been termed organic junk foods, such as peanut butter cookies, sweetened cereals, potato chips, and soda, which may contain significant amounts of sugar and fat; although organic, such foods may not be healthful. All in all, Williams notes that whether or not organic foods are healthier than conventional foods is debatable, and along with the

TABLE 2.17 Fruits and vegetables ranked according to pesticide content from highest to lowest levels.The

clean dozen has the lowest pesticide levels while the dirty dozen contains the highest levels.The scoring system is presented by the Environmental Working Group, an organization dedicated to exposing threats to our health and environment and helping to provide solutions. The clean dozen (lowest pesticide content) Onions Avocado Sweet corn–Frozen Pineapples Mango Sweet peas–Frozen Asparagus Kiwi Bananas Cabbage Broccoli Eggplant

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1 1 2 7 9 11 11 14 16 17 18 19

The dirty dozen (highest pesticide content) Peaches Apples Sweet bell peppers Celery Nectarines Strawberries Cherries Lettuce Grapes (Imported) Pears Spinach Potatoes

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100 96 86 85 84 83 75 69 68 65 60 58

British Nutrition Foundation indicates that we need higher quality research than that currently available. Beyond health considerations, many promote buying organic as a means to help protect the environment. Organic farming practices may reduce pollution of our waters, while organic animal farming may be more humane.

Does commercial food processing affect food quality and safety? Ideally, commercial food processing would make food more healthy, safe, delicious, attractive, and stable. In many cases it does, but certain commercial food-processing practices may be detrimental to our health in several ways. Potential health risks of several food-processing practices, such as the intentional inclusion of food additives and the unintentional inclusion of bacteria, are discussed later in this chapter. The major problem with some forms of commercial food-processing techniques is adding the wrong stuff and taking away the good stuff. One potential health risk of commercial food processing is the conversion of a healthful food into a potentially harmful one. The major feature of the Prudent Healthy Diet is the consumption of wholesome, natural, low-fat foods. But most of us do consume a wide variety of packaged foods, some of which may be highly processed and may be of questionable nutritional value. There has been increasing concern over the years that the nutritional quality of our food has been declining because many of our foods are overprocessed. They contain too much refined sugar, extracted oils, or white flour, all products of a refinement process. Refined sugar is pure carbohydrate with no nutritional value except Calories. The same can be said for extracted oils, which are pure fat. In the bleaching and processing of wheat to white flour, at least twenty-two known essential nutrients are removed, including the B vitamins, vitamin E, calcium, phosphorus, potassium, and magnesium. In addition, many fruits and vegetables are artificially ripened before they have reached maturity and contain smaller quantities of vitamins and minerals than naturally ripened ones do. We also consume many totally synthetic products such as artificial orange juice, nondairy creamers, and imitation ice cream, which do not possess the same nutrient value as their natural counterparts. Concern about the declining nutritional value of our food supply appears to be legitimate. Much of the blame is assigned to the processing of food, rightfully so but not necessarily so. In the mind of the public, processed foods more and more are thought to be inferior foods as compared with natural sources— for example, frozen peas versus fresh peas. The major purpose of food processing is to prevent waste through deterioration or spoilage. There are a variety of ways to do this, including heat, irradiation, dehydration, refrigeration, freezing, and the use of chemicals. Commercial food processing results in the loss of some nutrients, but preservation techniques in common use today do not cause major nutrient losses in the foods we eat. Commercial food processing may actually cause less nutrient loss than home processing. For example, some frozen foods may have higher concentrations of nutrients than their fresh counterparts because they are usually “flash-frozen” soon after picking. Processed tomatoes may

increase the bioavailability of phytochemicals, such as lycopene, by breaking cell walls. In addition, food companies may enrich or fortify certain products before marketing. Examples include the addition of some B vitamins and iron to grain products, vitamins A and D to milk, vitamin A to margarine, and iodine to table salt. In some cases not all of the nutrients that were removed in processing are returned, but in some products a greater amount is returned or added. Nevertheless, a few nutrients may be susceptible to loss through processing. Finley and others indicated that heat is particularly destructive to nutrients, especially vitamins. However, processing at optimal temperature and time may minimize nutrient loss. The key point is that commercial processing of food will not necessarily lead to a nutritionally inferior product. Even if commercial food processing does cause a slight decrease in nutritional quality, it helps provide a greater and more varied food supply with adequate amounts of dietary nutrients. The major problem with food processing is the excessive use of highly refined products like sugar, oils, fats, unenriched white flour, and salt. Additionally, some foods are fortified with vitamins and minerals up to 100 percent of the RDA. Consumption of multiple servings of such products may exceed the UL for several nutrients. Wise food selection can help avoid these problems, though this may be somewhat tricky in today’s food marketplace. It requires careful reading of food labels. Another potential health problem with commercial food processing is the inadvertent inclusion of bacteria. Although bacteria may be added unintentionally during commercial processing, improper food preparation at home also may contribute to the development of health problems, as discussed below.

Does home food processing affect food quality and safety? Somewhat like commercial food processing, you process food at home. You may wash, cut, blend, freeze, and cook a variety of foods at home in preparation for a meal, and home food processing, like commercial food processing, may lead to loss of some nutrients, particularly several water-soluble vitamins. You can minimize nutrient losses and preserve the healthful quality of foods by following these procedures at home: • Keep most fruits and vegetables chilled in the refrigerator to prevent enzymic destruction of nutrients. For similar reasons, keep frozen foods in the freezer until ready for preparation to eat. • After cutting, wrap most fruits and vegetables tightly to prevent exposure to air, which may accelerate oxidation and spoiling, and store them in the refrigerator. • Buy milk in cardboard or opaque plastic containers to prevent light from destroying riboflavin, a B vitamin. For similar reasons, keep most grain products stored in opaque containers or dark cupboards. • Steam or microwave vegetables in very little water to prevent the loss of water-soluble vitamins and some minerals. Microwaving is very effective in preserving the nutrient value of food. Use microwave-safe dishes or glass cookware. Do not use plastic wrap, plastic containers, or Styrofoam because www.mhhe.com/williams9

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chemicals can leach into the food when heated. Cover food with a paper towel instead. • Avoid cooking with high temperatures and prolonged cooking of foods, particularly in hot water, which may increase nutrient losses such as water-soluble vitamins. • Avoid excess cooking of foods, which may produce several carcinogens. Recent research indicates prolonged, high-temperature cooking, such as when French fries and other starchy foods are fried or baked at high temperatures (over 250ºF), may produce acrylamide, a cancer-causing agent. In particular, avoid grilling or broiling foods, especially meats, over open flames on a daily basis as charring may lead to the formation of heterocyclic amines (HCA), a known carcinogen. Frying foods may also produce HCA, but steaming, boiling, stir frying, poaching, or microwaving meat are probably the healthiest cooking methods. Using these techniques, nutrient losses incurred with home food processing are minimal, and an adequate nutrient intake will be obtained if you consume a wide variety of foods.

What is food poisoning? The major health problem associated with home food processing is the presence of foodborne bacteria. Food bacteria are of two types. One type causes food spoilage, which probably won’t make you sick, while the other type doesn’t spoil food, but can make you sick. Food poisoning is caused primarily by consuming foods contaminated with certain bacteria, particularly Salmonella, Escherichia, Staphylococcus, Clostridium, Campylobacter, and Listeria. Campylobacter jejuni and Salmonella are the most commonly reported bacterial causes of food poisoning in the United States. With increasing globalization of food distribution, foodborne illness is likely to become a major public health focus worldwide. Bacteria that cause food poisoning are found mainly in animal foods. The Consumers Union reported that 83 percent of whole chicken broilers bought nationwide, even premium and organic broilers, harbored Campylobacter or Salmonella. Bacteria are also common in produce. The contamination of fresh spinach with the bacteria Escherichia coli (E. coli) led to one of the largest and deadliest outbreaks of foodborne illness in recent years. There were thirty-one cases of kidney failure, with three deaths. The most common sources of food poisoning are • • • • •

1. Wash hands thoroughly and often before and during food preparations. 2. Treat all raw meat, poultry, fish, seafood, and eggs as if they were contaminated. When shopping, place meat in separate

Raw and undercooked meat and poultry Raw or undercooked eggs Raw or undercooked shellfish Contaminated produce Improperly canned foods

The most common symptoms of food poisoning include nausea, vomiting, or diarrhea, which normally clear up in a day or two. However, individuals should seek medical help in cases involving headache, stiff neck, and fever occurring together; bloody diarrhea; diarrhea lasting longer than three days; fever that lasts more than 24 hours; or sensations of weakness, numbness, and tingling in the arms and legs. Some cases of food poi72

soning may lead to lifelong health problems and may be fatal if not treated properly. Most cases of food poisoning occur at home, and may be associated with inappropriate commercial food processing. Although governmental health agencies attempt to control the spread of bacteria to food through appropriate regulations governing the food industry, the Consumers Union recently noted occasional outbreaks do occur because of food contamination during industrial processing, such as ground meat contamination with Escherichia coli (E. coli). E. coli can lead to kidney failure. Millions of Americans experience a significant foodborne illness each year, with several thousand fatalities. Food poisoning may be prevented by improving both commercial and home food processing. The Consumers Union notes that government action within recent years has reduced bacterial contamination of the food supply. New processes to eradicate bacteria are being used, such as pulsed electrical fields and ultrasound. One procedure is irradiation, a process whereby food products are subjected to powerful gamma rays from ionizing radiation, such as radioactive cobalt-60. Parnes and Lichtenstein indicate that irradiating food can greatly reduce illness from foodborne pathogens and extend food shelf life by delaying ripening, inhibiting spoilage, and minimizing contamination, and may do so without affecting nutritional or taste qualities. Irradiation may also reduce the need for many food preservatives. The FDA has approved irradiation for poultry, beef, pork, and lamb. Irradiated food products must have a label containing a statement that they have been treated and the international symbol of irradiation known as a “radura”, which is depicted in figure 2.13. The position of the American Dietetic Association, developed by Wood and Bruhn, is that food irradiation enhances the safety and quality of the food supply and helps protect consumers from foodborne illness. If you prefer to not purchase irradiated meats, at the minimum the following guidelines should be helpful in preventing the spread of bacteria in food prepared at home. Even if you buy irradiated foods, which may reduce the possibility of bacterial contamination, these guidelines are still recommended.

F I G U R E 2 . 1 3 The radura, the international symbol of

irradiation.

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3.

4.

5.

6. 7.

8. 9. 10.

bags, and store them that way in the refrigerator. Rinsing raw meat is more likely to contaminate the kitchen than decontaminate the food. Handle raw meat in just one part of the kitchen, on a cutting board used only for such food. Prevent juices from getting on other foods. Eating raw fruits and vegetables is healthy. However, produce is often coated with wax, which can trap potentially dangerous pesticides. Wash all fruits and vegetables thoroughly with running water, even if you are going to peel them with a knife. The knife can transfer bacteria to the fruit as you recut it. Thoroughly clean with hot soapy water all utensils used in food preparation. Microwaving your sponges and other food preparation utensils for about 30 to 60 seconds may help kill bacteria. Use a clean preparation surface. After preparing poultry or other animal foods, clean the preparation surface thoroughly before using it to prepare other foods. When using the same surface, prepare animal foods last. Do not use canned foods that are extensively dented or bulging. Cook all meat, poultry, seafood, and eggs thoroughly according to directions. Use a meat thermometer inserted deep into the meat, especially with ground meat, because bacteria may get from the surface to the interior. Heat meat to the desired temperature, usually noted on the meat package. Guidelines include heating beef, pork, lamb, and veal to 160° and poultry to 170°–180°. However, do not overcook or char meats, as this process may produce carcinogens. Do not eat raw shellfish. Store heated foods promptly in the refrigerator or freezer. Reheat foods thoroughly. Use leftovers within a few days. When in doubt, throw it out.

Are food additives safe? Do you ever read the list of ingredients on the labels of highly processed food products? If not, check one out soon. My guess is you will not know what half the ingredients are or why they are there (unless the reason is listed). A recently purchased box of Long Grain & Wild Rice with Herb Seasoning, thought to be totally natural, had the main ingredients of enriched parboiled long grain rice, wild rice, and dehydrated vegetables (onion, parsley, spinach, garlic, celery) as the herb seasoning—along with hydrolyzed vegetable protein, salt, sugar, monosodium glutamate, autolyzed yeast, sodium silicoaluminate, disodium inosinate, disodium guanylate, and sodium sulfite. The rice was delicious, but were all the additives necessary? The Food and Drug Administration (FDA) classifies a food additive as any substance added directly to food. There are more than forty different purposes for the additives in the foods we eat, but the four most common are to add flavor, to enhance color, to improve texture, and to preserve the food. For example, vanilla extract may be added to ice cream to impart a vanilla flavor, vitamin C (ascorbic acid) may be added to fruits and vegetables to prevent discoloration, emulsifiers may be added to help blend oil evenly throughout a product, and sodium propionate may be used to prolong shelf life. Nutrients may also be added to increase the quality of the product, a process called fortification.

To earn FDA approval, additives must be generally recognized as safe (GRAS). The Office of Food Additive Safety of the FDA has determined an acceptable daily intake (ADI) for some, but not all, food additives. The ADI represents the amount of food additive that an individual may consume daily without any adverse effect, and includes a 100-fold safety factor. Additives may be added only to specific foods for specific purposes, and in general must improve the quality of the food without posing any hazards to humans. Only the minimum amount necessary to achieve the desired purpose may be added. Although we realize that absolute safety does not exist in anything we do, including eating, we do have a right to expect that the food we purchase is generally safe for consumption. The government and food manufacturers must take utmost care to ensure that food additives do not create any appreciable health risks. On the other hand, we as consumers also have a responsibility to select foods necessary for good nutrition. Food product labeling has helped us in this regard, for we now can tell what ingredients we are eating, although we may not always know why they are there. In the past, the major concern with most additives was the possibility that they could cause cancer. The Delaney Clause to the Food, Drug, and Cosmetic Act prohibits the addition of any additive to foods if it has been shown to cause cancer in animals or humans at any dose. Saccharin, which has been shown to cause cancer in laboratory animals when given in high doses, was exempted from the Delaney Clause by an act of Congress. More recently, in its position statement on food and water safety, the American Dietetic Association cited a National Research Council report indicating that people should worry less about the risk of cancer from food additives and be more concerned about the carcinogenic effects of excess macronutrients (sugar and fat), evidenced by the linkage of obesity to various cancers. In general, the additives in today’s food are regarded safe. Nevertheless, in a recent review of over 70 food additives, the Center for Science in the Public Interest (CSPI) noted that although most were safe, others could pose some health problems. The CSPI recommended that individuals cut back on some additives because, although not toxic, large amounts may be unsafe or unhealthy. Included in this list are corn syrup, partially hydrogenated vegetable oil, and sugar, all products with high caloric content. Some additives were recommended to be treated with caution, as they may pose a risk and need to be better tested, such as some artificial colorings and aspartame. The CSPI noted that certain people should avoid other additives, such as caffeine and sulfites. Finally, the CSPI recommended everyone should avoid several products because they are unsafe or very poorly tested and not worth the risk, such as ephedrine and the fat-substitute olestra. The health aspects of many of these food additives will be discussed in later chapters where appropriate. www.cspinet.org/reports/chemcuisine.html The Center for Science in the Public Interest has developed a guide to safety of food additives, including the following five categories: Safe; Cut Back; Caution; Certain People Should Avoid; Everyone Should Avoid.

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Why do some people experience adverse reactions to some foods? Although most food we eat is safe and causes no acute health problems, some individuals may experience mild to severe reactions, or possibly death, from eating certain foods. These reactions may be attributed to food intolerance or food allergy. Food intolerance, the most common problem, is a general term for any adverse reaction to a food or food component that does not involve the immune system. The body cannot properly digest a portion of the food because it lacks the appropriate enzyme, resulting in gastrointestinal distress such as bloating, abdominal pain, nausea, and diarrhea. For example, many African Americans lack lactase, the enzyme needed to digest lactose (milk sugar), and thus suffer from lactose intolerance, a topic that is covered in chapter 4. Other common causes of food intolerance are fructose, as found in fruit juice and high-fructose corn syrup, and gluten, a protein found in wheat, rye, and barley. Food allergy, also known as food hypersensitivity, involves an adverse immune response to an otherwise harmless food substance. Many foods contain allergens, usually proteins, that may stimulate the immune system to manufacture antibodies (immunoglobulin E, or IgE) specific to that food. When individuals who have inherited a food allergy are first exposed to that food, their immune system produces millions of IgE antibodies. These antibodies reside in some white blood cells and mast cells in the body, particularly in the skin, respiratory tract, and gastrointestinal tract, the parts of the body that come into contact with air and the food we eat. These cells also contain substances, such as histamine, that are released when the antibodies are exposed again to the offending food allergen. Histamine and other chemicals cause the allergic reaction, which may involve the skin (swelling, hives, itchy skin and eyes), gastrointestinal tract (nausea, vomiting, abdominal cramps, diarrhea), or respiratory tract (runny nose, sneezing, coughing). In severe cases, an allergic response may involve anaphylactic shock and death by respiratory failure. Food allergies affect approximately 2–4 percent of adults and 6–8 percent of children in the United States, or more than 6 million individuals. Keet and Wood note that some allergies are mostly outgrown, while others are usually lifelong. Over 700 food allergens have been identified. Although allergens may be found in many foods, 90 percent of the offenders are proteins found in several common foods. The FDA mandates clear labeling and source of ingredients derived from commonly allergenic sources. Labels are required to state clearly whether the food contains one of the eight “major food allergens” listed: • • • • • • • • 74

Milk Fish Tree nuts Wheat Eggs Crustacean shellfish Peanuts Soybeans

Some additives also may cause allergic responses, particularly sulfites used as preservatives. For individuals who know which food substances may trigger an allergic response, food labels may be helpful in determining the allergen’s presence. Food manufacturers are placing notices on food labels for “Food Allergic Consumers” to check the ingredient list, and also note that the product may have been manufactured in a factory that makes other products containing allergenic foods. If you experience problems when you consume certain foods, you may be able to make a self-diagnosis by simply avoiding that food and noting whether or not you experience a recurrence. But, because there may be many causes of food-related illness, you should consult an allergist or other appropriate physician to determine whether you have either food intolerance or food allergy. Once the offending food is determined, you may need to eliminate that food from your diet or reduce the amount you consume. In some cases this is relatively simple. For example, if you develop a reaction to clams, a common problem, you should have no difficulty finding other sources of high-quality protein. However, if you react to milk, it may be more difficult to obtain an adequate dietary intake of calcium. A dietician will be able to assist you in planning a diet that compensates for the reduced intake of calcium. Some suggestions are presented in chapter 8. If you want to complain to the FDA about food-related illnesses, adverse events after taking dietary supplements, products not labeled for allergens, or other problems with food products, you may use the Consumer Complaint System. www.fda.gov/opacom/backgrounders/complain.htm To complain to the FDA about various food-related health problems, this site provides a contact phone number for your state and information to include in your report.

Ke y C o n c e p t s 䉴 In general, current food biotechnology techniques, such as









genetically modified (GM) food, help provide a food supply that is high quality and safe. However, preventing the introduction of allergy-causing ingredients in GM foods is a concern. Pesticide residues in most foods are minimal, but some foods may contain more than others.The major concern is reducing pesticide intake in children as some scientists believe neurological development may be impaired. Although organic foods may contain lesser amounts of pesticides than conventional foods, they may not contain fewer bacteria or higher nutrient density. The available research is insufficient to determine whether or not consumption of organic foods confers any health benefits. Commercial food processing can provide safe and healthful foods. However, excess sugar and fat added during commercial food processing may dilute health benefits. Proper food preparation practices may help preserve the nutrient quality and safety of foods prepared at home.

C H A P T E R 2 Healthful Nutrition for Fitness and Sport: The Consumer Athlete

䉴 Certain individuals may be intolerant to various foods or experi-

ence allergic responses to others and thus should take precautions to avoid such foods.

C h e c k f o r Yo u r s e l f Check the food label for several commercial food products you love most. Check the list of ingredients. Do you recognize any of the additives?

Healthful Nutrition: Recommendations for Better Physical Performance Sports nutrition for the physically active person may be viewed from two aspects: nutrition for training and nutrition for competition. Of the three basic purposes of food—to provide energy, to regulate metabolic processes, and to support growth and development— the first two are of prime importance during athletic competition, while all three need to be considered during the training period in preparation for competition. Articles about nutrition for athletes in popular sports magazines, and food supplements advertised therein, give the impression that athletes have special nutritional requirements above those of nonathletes. In general, however, the diet that is optimal for health is also optimal for physical or sport performance. The Prudent Healthy Diet will provide adequate food energy and nutrients to meet the need of almost all athletes in training and competition. Nevertheless, modifications to the Prudent Healthy Diet may help enhance performance for certain athletic endeavors, and subsequent chapters will focus on specific recommendations relative to the use of various nutrients and dietary supplements to enhance physical performance. The purpose of this section is to provide some general recommendations regarding the use of the Prudent Healthy Diet by the athlete for training and competition. However, it is very important for athletes to individualize their dietary practices. Each athlete should keep track of what, how much, and when they eat and drink during training and competition, and experiment with dietary strategies to find those that are optimal. The United States Anti-Doping Agency has developed a pamphlet, Optimal Dietary Intake for Sport, for Life with a focus on a healthy diet and appropriate modifications for sport performance. www.usada.org Click on the Clean Sport and You logo to access the 32-page pamphlet Optimal Dietary Intake for Sport, for Life.

What should I eat during training? Sport scientists and coaches both stress the importance of proper nutrition during training. Ron Maughan, an expert in exercise metabolism and sports nutrition, notes that the main role of nutrition for the athlete may be to support consistent intensive training,

while Chris Carmichael, coach and nutritionist for seven-time Tour de France champion Lance Armstrong, indicates that athletes need to match their nutritional intake to the demands of their training. As noted in chapter 1, optimal training is the most important factor contributing to improved sport performance. Because energy expenditure increases during a training period, the caloric intake needed to maintain body weight may increase considerably—an additional 500–1,000 Calories or more per day in certain activities. By selecting these additional Calories wisely from a wide variety of foods, you should obtain an adequate amount of all nutrients essential for the formation of new body tissues and proper functioning of the energy systems that work harder during exercise. A balanced intake of carbohydrate, fat, protein, vitamins, minerals, and water is all that is necessary. For endurance athletes, dietary carbohydrates should receive even greater emphasis. However, there may be some circumstances during sport training that particular attention to the diet is important. For example, during the early phases of training, the body will begin to make adjustments in the energy systems so that they become more efficient. This is the so-called chronic training effect, and many of the body’s adjustments incorporate specific nutrients. For example, one of the chronic effects of long distance running is an increased hemoglobin content in the blood and increased myoglobin and cytochromes in the muscle cells; all three compounds need iron in order to be formed. Hence, the daily diet would need to contain adequate amounts of iron not only to meet normal needs but also to make effective body adjustments due to the chronic effects of training. Timing of nutrient intake during training may also be very important. In a recent review, John Hawley, a renowned sports scientist from Australia, noted that the beneficial effects of exercise training are believed to occur during recovery from each exercise bout, and evidence is accumulating that nutrient supplementation can serve as a potent modulator of many of the acute responses to both endurance and resistance training. Consuming a carbohydrate/protein combination shortly after strenuous exercise may be a recommended procedure. Breakfast may be especially important during training. A balanced breakfast provides a significant amount of Calories and other nutrients in the daily diet of the physically active person. A breakfast of skim milk, a poached egg, whole-grain toast, fortified high-fiber cereal, and orange juice will help provide a substantial part of the RDA for protein, calcium, iron, fiber, vitamin C, and other nutrients and is also relatively high in complex carbohydrates. A balanced breakfast high in fiber with an average amount of protein also will help prevent the onset of mid-morning hunger. The fiber and protein may help maintain a feeling of satiety throughout the www.mhhe.com/williams9

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morning, whereas a breakfast of refined carbohydrates, like doughnuts, may trigger an insulin response and produce hypoglycemia (low blood sugar) in the middle of the morning. The resultant hunger is typically satisfied by eating other refined carbohydrates, which will satisfy the hunger urge only until about lunchtime. A balanced breakfast having a high nutrient density is therefore preferable to a breakfast based on refined carbohydrate products. Nontraditional breakfast foods, such as pizza, may also provide a balanced meal for breakfast. Skipping breakfast would be comparable to a small fast, as the individual might not eat for 12 to 14 hours. This could conceivably produce hypoglycemia with resultant symptoms of weakness and possible impairment of training. Indeed, Schabort and others recently reported that when compared to no breakfast after an overnight fast, subjects who ate a breakfast containing 100 grams of carbohydrate improved their cycling endurance time by 36 percent. Moreover, for young athletes, Nicklas and others have noted that breakfast consumption is an important factor in their nutritional well-being, enhancing their academic performance, an important consideration for those aspiring to college scholarships. Although individual preferences should be taken into account, a balanced breakfast could provide a good source of some major nutrients to the individual who is involved in a physical conditioning program. For those on a tight time schedule, a bowl of ready-toeat, fortified high-fiber cereal with skim milk and fruit may be an ideal choice. Nancy Clark, a nationally acclaimed sports nutritionist, notes that this breakfast is not only quick, easy, and convenient but also rich in carbohydrate, fiber, iron, calcium, and vitamins. Proper nutrition should enhance the physiological responses to training, and thus enhance competitive sports performance. The nutrient needs of athletes in training will be highlighted throughout the remainder of this text where relevant.

When and what should I eat just prior to competition? In competition an athlete will utilize specific body energy sources and systems, depending upon the intensity and duration of the exercise. The three human energy systems will be discussed in detail in chapter 3. Briefly, however, high-energy compounds stored in the muscle are utilized during very short, high-intensity exercise; carbohydrate stored in the muscle as glycogen may be used without oxygen for intense exercise lasting about 1 to 3 minutes; and the oxidation of glycogen and fats becomes increasingly important in endurance activities lasting longer than 5 minutes. The release of energy in each of these three systems may require certain vitamins and minerals for optimal efficiency. If an individual is well nourished, athletic competition normally will not impose any special demands for any of the six major classes of nutrients. Body energy stores of carbohydrate and fat are adequate to satisfy the energy demands of most activities lasting less than 1 hour. Protein is not generally considered a significant energy source during exercise. The vitamin and mineral content of the body will be sufficient to help regulate the increased levels of metabolic activity, and body-water supply will be adequate under normal environmental conditions. 76

However, content and timing of the precompetition may be critical. It is a well-established fact that the ingestion of food just prior to competition will not benefit physical performance in most athletic events, yet the pregame meal, so to speak, is one of the major topics of discussion among athletes. A number of special meals have been utilized throughout the years because of their alleged benefits to physical performance, and special products have been marketed as pre-event nutritional supplements. Although research has not substantiated the value of any one particular precompetition meal, some general guidelines have been developed from practical experience over the years. There are several major goals of the precompetition meal that may be achieved through proper timing and composition. In general, the precompetition meal should do the following: 1. Allow for the stomach to be relatively empty at the start of competition. In general, a solid meal should be eaten about 3 to 4 hours prior to competition. This should allow ample time for digestion to occur so that the stomach is relatively empty, and yet hunger sensations are minimized. However, pre-event emotional tension or anxiety may delay digestive time, as will a meal with a high-fat or high-protein content. Hence, the composition of the meal is critical. It should be high in carbohydrate, low in fat, and low to moderate in protein, providing for easy digestibility. 2. Help to prevent or minimize gastrointestinal distress. The composition of the precompetition meal should not contribute to any gastrointestinal distress, such as flatulence, increased acidity in the stomach, heartburn, or increased bulk that may stimulate the need for a bowel movement during competition. In general, foods to be avoided include gas formers like beans, spicy foods that may elicit heartburn, and bulk foods like bran products. High-sugar compounds may delay gastric emptying or create a reverse osmotic effect, possibly increasing the fluid content of the stomach, which may lead to a feeling of distress, cramps, or nausea. High-sugar loads, particularly fructose, may also lead to other forms of gastrointestinal distress, such as diarrhea. Individuals with known food intolerances, such as lactose intolerance, should use due caution. Through experience, you should learn what foods disagree with you during performance, and of course, you should avoid these prior to competition. 3. Help avoid sensations of hunger, lightheadedness, or fatigue. A small amount of protein in a carbohydrate meal will help delay the onset of hunger. Large amounts of concentrated sugars can cause a reactive drop in blood sugar in susceptible individuals, which may cause lightheadedness and fatigue. 4. Provide adequate energy supplies, primarily carbohydrate, in the blood and muscles. A wide variety of foods may be selected for the precompetition meal. The meal should consist of foods that are high in complex carbohydrates with moderate to low amounts of protein. Examples of such foods are presented in later chapters and also may be found in appendix E, particularly those in the starch list. The foods should be agreeable to you. You should eat what you like within the guidelines presented above.

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5. Provide an adequate amount of body water. Adequate fluid intake should be assured prior to an event, particularly if the event will be of long duration or conducted under hot environmental conditions. Diuretics such as alcohol, which increase the excretion of body water, should be avoided. Large amounts of protein increase the water output of the kidneys and thus should be avoided. Fluids may be taken up to 15 to 30 minutes prior to competition to help ensure adequate hydration. Two examples of precompetition meals, each containing about 500–600 Calories with substantial amounts of carbohydrate, are presented in table 2.18. Bloch and Wheeler recently presented an excellent overview of practical approaches to feeding athletes. A similar approach, based on the Food Exchange System, is presented in chapter 11 as a means of designing comprehensive diet plans for physically active individuals. One important last point. Meals other than the precompetition meal eaten on the same day should not be skipped. They should adhere to the basic principles set forth earlier in this chapter. Follow these general recommendations. 1. For events in the morning, eat a precompetition meal similar to breakfast; for example, meal A in table 2.18. 2. For events in early to mid-afternoon, eat breakfast and lunch. You might consume a more substantial breakfast, along with meal B in table 2.18 as a precompetition meal for lunch. 3. For events in the late afternoon, eat breakfast, lunch, and a snack. Again, eat a substantial breakfast and lunch and consume snacks that appeal to you, such as fruit, bagels with jelly, or other easily digestible foods. 4. For events in the evening, eat breakfast, lunch, and a precompetition meal for dinner. Pre-event nutritional strategies will vary somewhat for athletes involved in prolonged exercise tasks, such as running a marathon. As noted by prominent Australian exercise scientist Mark Hargreaves, body stores of both carbohydrate and fluids should be optimized. To achieve this goal, athletes may engage in practices such as carbohydrate loading and water hyperhydration, which will be detailed in chapters 4 and 9.

What should I eat during competition? There is no need to consume anything during most types of athletic competition with the possible exception of carbohydrate and TABLE 2.18 Two examples of precompetition meals

containing 500–600 Calories Meal A

Meal B

Glass of orange juice One bowl of oatmeal Two pieces of toast with jelly Sliced peaches with skim milk

One cup low-fat yogurt One banana One toasted bagel One ounce of turkey breast One-half cup of raisins

water. Carbohydrate may provide additional supplies of the preferred energy source during high-intensity intermittent and prolonged exercise, while water intake may be critical for regulation of body temperature when exercising in warm environments. In ultradistance competition, a hypotonic salt solution also may be recommended. Appropriate details are presented in chapters 4 and 9.

What should I eat after competition? In general, a balanced diet is all that is necessary to meet your nutrient needs and restore your nutritional status to normal following competition or daily, hard physical training. Carbohydrate and fat are the main nutrients used during exercise and can be replaced easily from foods among the food exchange lists. The increased caloric intake that is needed to replace your energy expenditure also will help provide you with the additional small amounts of protein, vitamins, minerals, and electrolytes that may be necessary for effective recovery. Thirst will normally help replace water losses on a day-to-day basis; you can check this by recording your body weight each morning to see if it is back to normal. As noted previously, timing of food intake may be an important consideration. Simple sugars eaten immediately after a hard workout may help restore muscle glycogen fairly rapidly. Consuming a small amount of high-quality protein may also be prudent. Specific guidelines are presented in chapters 4 and 6. For those who must compete several times daily and eat between competitions, such as in tennis tournaments or swim meets, the principles relative to pregame meals may be relevant, with a focus on carbohydrate-rich foods or fluids and moderate protein intake.

Should athletes use commercial sports foods? The sports nutrition industry is booming. Numerous products are marketed to athletes, including sports liquid meals, sports drinks, sports bars, sports gels, sports candy, and sports supplements. It is important to note that although many of these products may be convenient and appropriate for a pregame, post-training, or postcompetition meal, they do not contain all the healthful nutrients found in natural foods and thus should not be used on a long-term basis to replace the Prudent Healthy Diet. Liquid Sports Meals Liquid meals, many of them designed specifically for athletes, usually contain high-quality sources of carbohydrate and protein, a low-to-moderate fat content, vitamins and minerals, and various other supplements. The food label will provide the amounts of each. They are very convenient for precompetition meals as well as for recovery nutrition after training or competition. Liquid meals available include Nutrament, Ensure, Slim-Fast, Boost, Gatorade Nutrition Shake, and PowerBar ProteinPlus. Some liquid meals come premixed, while others come as powders. You can make your own liquid sports meal, or smoothie, from high-quality carbohydrate/protein powders, such as nonfat dry www.mhhe.com/williams9

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milk powder, and/or other healthful sources of carbohydrate and protein, such as yogurt and fruits. The following formula will provide one quart of a tasty liquid meal: ⁄2 cup water/ice cubes ⁄2 cup of nonfat dry milk powder 1 ⁄4 cup of a glucose polymer 1 frozen banana 3 cups of cold skim milk 1 teaspoon of flavoring for palatability (cherry, vanilla) 1 1

A liquid meal may be assimilated more readily than a solid meal, and thus may be useful as a precompetition meal because it may be taken closer to competition, say 2 to 3 hours before. Research has shown that there is no difference between a liquid and a solid meal relative to subsequent hunger, nausea, diarrhea, or physical performance. Sports Bars Sports bars have become increasingly popular in recent years, and several dozen products are targeted to physically active individuals. Sports bars vary in composition. Some are high carbohydrate, some high protein, and some have nearly equal mixtures of carbohydrate, protein, and fat. Many are vitamin and mineral fortified, and some are designed to serve as a meal replacement. Others contain drugs, such as caffeine. As with liquid meals, the food label on the sports bar will describe its contents. When compared to comparable energy sources from ordinary food, sports bars do not possess any magical qualities to enhance physical performance, but they possess some advantages similar to liquid meals, such as convenience. Because the major ingredient in many sports bars is carbohydrate, an expanded discussion is presented in chapter 4. Sports Drinks Sports drinks are generally referred to as carbohydrate and electrolyte replacement fluids, and may be consumed by athletes before, during, and after training and competition. Examples include Gatorade and PowerAde. They are designed to provide carbohydrate, water, and electrolytes, and their role in sport is discussed in chapters 4 and 9. Sports Gels and Candy Sports gels and candy normally provides carbohydrate, but may contain other substances such as vitamins, minerals, and caffeine. Their primary purpose is to provide a source of easily digested carbohydrates for energy during exercise. Sports Supplements As noted in chapter 1, numerous sports supplements are marketed to athletes, including various forms of carbohydrates, fats, and protein, many vitamins and minerals, several food drugs, and selected herbal or botanical products. Based on the available scientific data, the use of most sports supplements does not appear to be necessary for the well-nourished athlete during training. However, nutrient supplementation may be warranted in some cases. For example, in activities where excess body weight may serve to handicap performance, a loss of some body fat may be helpful. During weight loss, vitamin-mineral supplements may be recommended to prevent a nutrient defi78

ciency. Furthermore, use of several sport supplements has been supported by research because they may enhance physical performance, may not pose any health risks, and may be legal. Research evaluating the effectiveness of purported sport ergogenics is presented throughout the book. Pertinent discussion topics include the following: Chapter 4: Carbohydrate ergogenics Chapter 5: Ergogenics that affect fat metabolism Chapter 6: Amino acids, creatine, and other protein-related ergogenics Chapter 7: Vitamins and other vitamin-related ergogenics Chapter 8: Mineral ergogenics Chapter 9: Glycerol Chapter 13: Alcohol, caffeine, and other food–drug and herbal ergogenics

How can I eat more nutritiously while traveling for competition? Athletes who must travel to compete are often faced with the problem of obtaining proper pre-event and postevent nutrition. After reading this chapter, you should be aware of how to select foods that are high in carbohydrate, low in fat, and moderate in protein. More guidelines are presented in chapters 4 through 6. One possible solution is to pack your own food and fluids in a traveling bag or cooler. Foods from each of the Food Exchange Lists can be easily packed or kept on ice, such as skim milk; precooked low-fat meats; bagels and cereal; fruits, juices, and vegetables; sports drinks; and high-carbohydrate snacks including whole wheat crackers and pretzels, and low-fat cookies such as Fig Newtons and vanilla wafers. Small containers of condiments can also be easily transported in the cooler, along with proper eating utensils. Taking your own food means you can eat your pre-event or postevent meal as planned, and you may save money as well. Such an approach may be very effective for short, one-day trips and may also be used to complement other meals on longer journeys. Some easily packed snack foods are presented in table 2.19. While traveling, you have a variety of eating places from which to select your food, including full-service restaurants, restaurants with all-you-can-eat buffets, steakhouses and fishhouses, fast-food restaurants, pizza parlors, sub shops, supermarkets, convenience stores, and even vending machines. With a solid background on the nutritional principles presented in this chapter, you should be able to select healthful, high-carbohydrate and low-fat foods at any of these establishments, but of course the variety of food choices will vary depending on the place you choose. Keep in mind that you can always ask to see if they will create a meal for you. For example, order a salad and ask to have extra vegetables and fish or chicken breast added, with the dressing on the side. Although all fast foods can be part of a healthy diet when consumed in moderation, many are relatively high in fat content, and their intake should be restricted. However, many restaurants do provide a few healthier choices with individual sandwiches containing less than 30 percent of their Calories from fat, including grilled or broiled chicken, lean roast beef, and veggie burgers. In

C H A P T E R 2 Healthful Nutrition for Fitness and Sport: The Consumer Athlete

TABLE 2.19

Easily packed snacks for traveling or brown bag lunches

Grains

Meats

Vegetables

Bagels Pita bread Muffins Fig Newtons Vanilla wafers Whole wheat crackers Graham crackers Dry cereals Wheat Chex Grapenuts Plain popcorn

Small can of baked beans Cooked chicken or turkey, small 2-ounce commercial packages, packed in airtight plastic bags Small can of tuna fish, salmon, or sardines Peanut butter Reduced-fat cheese slices String cheese

Sliced carrots Broccoli stalks Cauliflower pieces Tomatoes Canned vegetable juices

Fruits

Milk

Nuts

Small cans of fruit in own juice Small containers of fruit juice, aseptic packages Oranges Apples Other raw fruits Dried fruits

Small containers of skim or low-fat milk; chocolate milk; aseptic packaging if available Dried skim milk powder, to be reconstituted Packaged yogurt

Almonds Walnuts

some cases, particularly with grilled, skinless chicken sandwiches, much of the fat content is in the sauce added to the sandwich, so ordering the sauce on the side allows you to control the amount added. Other sandwich shops, such as Au Bon Pain and Subway may serve healthful sandwiches, but unwise selections in these stores may also contain substantial amounts of fat. You can eat fast food and stay within the recommended nutrition guidelines for a healthy diet, but obtaining a healthful diet requires careful selection of foods. Fast-food restaurants provide materials detailing the nutrient content of each of their products. In some cases the materials may be obtained in the restaurant, and all have Websites detailing nutrient analysis of their products. See appendix F for the fat percentages of specific fast-food products and appropriate Websites. The following suggestions may be helpful if you are dining in a fast-food or budget-type restaurant, such as McDonald’s, Wendy’s, Arby’s, Pizza Hut, Baja Fresh, Applebee’s, or Ruby Tuesday. Many supermarkets also have takeout departments or salad bars from which to select lunch or dinner. Breakfast selections English muffins, unbuttered, with jelly English muffins with Canadian bacon Whole wheat pancakes with syrup French toast Bran muffins, fat-free or low-fat Hot whole-grain cereal, oatmeal Ready-to-eat fortified, high-fiber cereal Skim or low-fat milk Orange juice Hot cocoa

Lunch or dinner selections Any low-fat sandwiches, no mayonnaise or high-fat sauces Grilled chicken breast sandwich, on whole-grain bun Baked or broiled fish sandwich Lean roast beef sandwich, on whole-grain bun Single, plain hamburger, on whole-grain bun Baked potato, with toppings on the side (add sparingly) Pasta dishes, spaghetti, and macaroni, with low-fat sauces Rice dishes Lo mein noodles, not chow mein (fried noodles) Soups, rice and noodle Salsas, made with tomatoes Chicken or seafood tostadas, made with cornmeal tortillas Bean and rice dishes All whole-grain and other breads Salads, low-fat dressing Salad bar, focus on vegetables and high-carbohydrate foods; avoid high-fat items Pizza, thick crust, vegetable type with minimum cheese topping Skim or low-fat milk; chocolate milk Orange juice Frozen yogurt, fat-free or low-fat Sherbet With any of these selections, it is always a good idea to order toppings, for example, mayonnaise, salad dressing, and so on, on the side so that you can control portions. When selecting sandwiches, ask for those that are either baked, broiled, or grilled. For the most part, research supports the general finding that the diet that is optimal for your health is also the optimal diet for your www.mhhe.com/williams9

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performance. Eating right, both for health and performance, does not mean you need to eat bland foods because all foods, some in moderation, can be tastefully prepared and blended into the Prudent Healthy Diet.

How do gender and age influence nutritional recommendations for enhanced physical performance? The diet that is optimal for health is the optimal diet for physical performance. This is the key principle of sports nutrition and it applies to physically active males and females of all ages. However, as shall be noted at certain points in this text, specific nutrient needs may vary by gender and age, and various forms of exercise training may influence nutrient requirements as well. Gender Seiler and others note that exercise performance is, in general, about 10 percent greater in males than females, mainly because males have greater levels of muscle mass and strength, anaerobic power and capacity, and maximal aerobic capacity, as well as lower levels of body fat. Nevertheless, most physiological adaptations to exercise are similar for males and females. Moreover, Maughan and Shirreffs, discussing nutrition and hydration needs of football (soccer) players, noted that the differences between males and females are smaller than differences between individuals, so that principles developed for male players also apply to women. However, several metabolic differences between males and females could influence nutritional requirements. For example, as shall be noted in chapter 5, female endurance athletes oxidize more fat and less carbohydrate during exercise as compared to males, which may influence various dietary strategies such as carbohydrate loading. Adolescent and adult premenopausal females need more dietary iron than males. Female athletes, especially those participating in aerobic endurance sports such as distance running, must include iron-rich foods in their diet or risk incurring iron-deficiency anemia and impaired running ability. Being smaller in size, women need fewer Calories than men, yet many may not consume adequate energy and may develop disordered eating practices as they attempt to lose body mass for competition purposes. Disordered eating is more prevalent in female athletes and may contribute to the development of premature osteoporosis, prompting the American College of Sports Medicine to develop a position stand on the Female Athlete Triad, an important issue discussed in chapters 8 and 10. Such athletes may need more dietary calcium. Because of gender differences, some sports nutrition products have been designed for women only. Age Youth sports competition is worldwide, ranging from community-based games to Olympic competition, and proper nutrition is important for these young athletes. Petrie and others have noted that child and adolescent athletes typically consume more food to meet their energy expenditure and thus are more likely to obtain an adequate supply of nutrients. However, one of the leading authorities on sports nutrition for children, Oded Bar-Or from McMaster University in Canada, noted that while nutritional considerations are similar for all athletes irrespective of age, children have several 80

physiological characteristics that may require specific nutritional considerations. For example, their relative protein needs may be greater to support growth, and their relative calcium needs may be greater for optimal bone development. Young athletes may experience greater thermal stress during exercise. Roberts indicates it may be unwise to allow children to exercise hard in high heat and humidity conditions, but also notes there are few data to support this concern. Those that participate in weight-control sports involving excessive exercise and inadequate energy intake may be at risk for nutrient deficiencies and impaired growth and development. The American Academy of Pediatrics has developed a policy stand on promotion of healthy weight-control practices in young athletes. Sport participation is also very popular at the other end of the age spectrum, and older athletes may also have special nutrient needs. In general, resting metabolism declines in older age, so caloric need may decrease. Older people also eat less, so they need to make wiser food choices, that is, foods with high nutrient density. Campbell and Geik recently noted that nutrition is a tool that the older athlete should use to enhance exercise performance and health. In particular, they noted that older athletes may need to focus on obtaining sufficient micronutrients, such as the B vitamins and vitamin D. Supplements may be recommended to obtain adequate vitamin B12 and calcium if not obtained from the diet, such as from fortified foods. Female athletes over age 50, because of decreased estrogen levels associated with menopause, need to focus on obtaining adequate calcium. However, they may need less dietary iron compared to their younger counterparts. Older individuals also need to ensure adequate fluid intake because of increased susceptibility to dehydration. The special nutrient requirements of females, the young, and the elderly, as they relate to physical activity, will be incorporated in the text where relevant. However, most of the nutritional principles underlying exercise and sport performance that are presented in this text apply to most physically active individuals.

Ke y C o n c e p t s 䉴 The precompetition meal should be easily digestible, high in car-

bohydrates, moderate in protein, and low in fat, and it should be consumed about 3–4 hours prior to competition. Athletes should determine what types of foods are compatible with their sport. 䉴 Liquid meals and sports bars may be convenient as an occasional meal replacement, including use as a precompetition meal, but should be used only occasionally and not serve as a substitute for healthy whole foods. 䉴 A healthful diet is the key to nutrition for male and female athletes at all age levels. However, female, young, and older athletes may have some specific nutritional needs in certain circumstances.

C h e c k f o r Yo u r s e l f Interview a coach or some athletes at your school about their meal strategies prior to competition. How do their strategies compare with general recommendations?

C H A P T E R 2 Healthful Nutrition for Fitness and Sport: The Consumer Athlete

A P P L I C AT I O N In chapter 1 we recommended that you consume your normal daily diet, record the foods you have eaten, and then rate your diet using

the quiz on pp. 28–30. Do the same but switch to a vegetarian diet, as close to a vegan diet as

E X E R C I S E

possible, for the day and compare the two rating scores.

Review Questions—Multiple Choice and botanicals, and various extracts and metabolites. (b) Genetically modified foods may be designed to increase the content of a specific nutrient. (c) Organic foods are healthier than conventional foods because they contain fewer bacteria and substantially more healthful nutrients. (d) Various products in foods may cause food intolerance or food allergies in susceptible individuals. (e) Food poisoning may be fatal. 5. Which of the following is not a key (indicator) nutrient as defined by the keynutrient concept? (a) iron (b) calcium (c) vitamin A (d) protein (e) vitamin D (f) riboflavin (g) niacin (h) all are key nutrients 6. The recommended dietary goals for healthy Americans suggest that the intake of saturated fat, as a percentage of daily Calories, be less than what percent? (a) 10 (b) 20 (c) 30 (d) 40 (e) 50 7. Which key nutrient is not usually found in substantial amounts in the meat group? (a) vitamin C (b) iron (c) protein (d) niacin (e) thiamin

8. A food label lists the amount of complex carbohydrates as 5 grams, the amount of simple sugars as 10 grams, the amount of protein as 5 grams, and the amount of fat as 10 grams. Which of the following is true? (a) Simple sugars make up the majority of the Calories. (b) Carbohydrate makes up the majority of the Calories. (c) The amount of Calories from protein and carbohydrate is equal. (d) The majority of the Calories is derived from fat. (e) None of the above statements is true. 9. A vegetarian-type diet may be more healthful than the current typical American diet for all of the following reasons except which? (a) higher in iron (b) higher in fiber (c) lower in saturated fats (d) a higher polyunsaturated to saturated fat ratio (e) lower in cholesterol 10. Which of the following is a recommendation for the precompetition meal for an endurance athlete who will be competing in warm environmental conditions? (a) water (b) sports drinks (c) high carbohydrate content (d) moderate protein content (e) moderate salt content (f) all of the above

Answers to multiple choice questions: 1. c; 2. d; 3. d; 4. c; 5. e; 6. a; 7. a; 8. d; 9. a; 10. f.

1. The guide to eating from the United States Department of Agriculture, MyPyramid, has six colors representing foods, but which of the following is not considered a food group by the USDA? (a) grains (b) meat (c) oils (d) fruits (e) milk (f) vegetables 2. Which of the following is not an acceptable definition for food labels with the listing “free”? (a) fat free—less than 0.5 grams of total fat per serving (b) cholesterol free—less than 2 milligrams per serving (c) sugar free—less than 0.5 grams per serving (d) Calorie free—less than 40 Calories per serving (e) sodium free—less than 5 milligrams per serving 3. Approximately how many Calories are in a meal with two starch/bread exchanges, four lean meat exchanges, one fruit exchange, two vegetable exchanges, three fat exchanges, and one skim milk exchange? (a) 450 (b) 540 (c) 670 (d) 715 (e) 780 4. Which of the following statements regarding consumer nutrition is false? (a) Dietary supplements include vitamins, minerals, amino acids, herbals

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Review Questions—Essay 1. Name the eight key nutrients and identify a food source that is particularly rich in each nutrient. For example, lean meat is a rich source of iron. 2. Discuss the six categories of foods depicted in the MyPyramid design in respect to the concepts of variety, proportionality, and moderation.

3. Compare and contrast the MyPyramid food guide with the Food Exchange System. What similarities and differences do you note? 4. List and explain the potential health benefits of a vegan diet as compared to the typical American diet today.

5. Identify the nutrients that must be listed on food labels, how the DV is determined for each, and why you may want to have a high percent of the DV for some and a low percent for others.

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National Academy of Sciences. Institute of Medicine, Food and Nutrition Board. 2000. Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids. Washington, DC: National Academy Press. National Academy of Sciences. Institute of Medicine, Food and Nutrition Board. 1999. Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride. Washington, DC: National Academy Press. National Research Council. 1989. Diet and Health: Implications for Reducing Chronic Disease Risk. Washington, DC: National Academy Press. Nestle, M. 2006. What to Eat: An Aisle-to-Aisle Guide to Savvy Food Choices and Good Eating. New York: North Point Press. Otten, J., et al. 2000. Dietary Reference Intakes: The Essential Guide to Nutrient Requirements. Washington, DC: National Academies Press. Shils, M., et al. (Eds.). 2006. Modern Nutrition in Health and Disease. Philadelphia: Lippincott Williams & Wilkins. Taubes, G. 2007. Good Calories, Bad Calories: Challenging the Conventional Wisdom on Diet, Weight Control, and Disease. New York: Alfred A. Knopf. United States Anti-Doping Agency. 2005. Optimal Dietary Intake. Colorado Springs, CO. U.S. Department of Agriculture and U.S. Department of Health and Human Services. 2005. Nutrition and Your Health: Dietary Guidelines for Americans. Washington, DC: U.S. Government Printing Office. U.S. Department of Health and Human Services. 2000. Healthy People 2010: National Health Promotion and Disease Prevention Objectives. Washington, DC: U.S. Government Printing Office. Ward, M. S. 2006. The Pocket Idiot’s Guide to the New Food Pyramids. Indianapolis: Alpha Books/Penguin.

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Katsilambros, N., et al. 2006. Critical review of the international guidelines: What is agreed upon—what is not? Nestle Nutrition Workshop Series: Clinical & Performance Programme 11:207–18. Kavanaugh, C., et al. 2007. The U.S. Food and Drug Administration’s evidence-based review for qualified health claims: Tomatoes, lycopene, and cancer. Journal of the National Cancer Institute 99:1074–85. Keet, C., and Wood, R. 2007. Food allergy and anaphylaxis. Immunology and Allergy Clinics of North America 27:193–212. Kennedy, D. 2004. Dietary diversity, diet quality, and body weight regulation. Nutrition Reviews 62:S78–S81. Kennedy, E. 2006. Evidence for nutritional benefits in prolonging wellness. American Journal of Clinical Nutrition 83:410S–14S. Key, T., et al. 2006. Health effects of vegetarian and vegan diets. Proceedings of the Nutrition Society 65:35–41. King, J. 2002. Biotechnology: A solution for improving nutrient bioavailability. International Journal of Vitamin and Nutrition Research 72:7–12. Krebs-Smith, S., and Kris-Etherton, P. 2007. How does MyPyramid compare to other populationbased recommendations for controlling chronic disease? Journal of the American Dietetic Association 107:830–37. Lichtenstein, A., and Russell, R. 2005. Essential nutrients: Food or supplements? Where should the emphasis be? Journal of the American Medical Association 294:351–58. Liu, R. 2004. Potential synergy of phytochemicals in cancer prevention: Mechanism of action. Journal of Nutrition 134:3479S–85S. Lynn, A., et al. 2006. Cruciferous vegetables and colorectal cancer. Proceedings of the Nutrition Society 65:135–44. Magkos, F., et al. 2006. Organic food: Buying more safety or just peace of mind? A critical review of the literature. Critical Reviews in Food Science and Nutrition 46:23–56. Mann, N. 2000. Dietary lean meat and human evolution. European Journal of Nutrition 39:71–79. Mares-Perlman, J., et al. 2002. The body of evidence to support a protective role for lutein and zeaxanthinin delaying chronic disease: Overview. Journal of Nutrition 132:518S–24S. Massey, B. 2002. Dietary supplements. Medical Clinics of North America 86:127–47. Maughan, R. 2002. The athlete’s diet: Nutritional goals and dietary strategies. Proceedings of the Nutrition Society 6:87–96. Maughan, R., and Shirreffs, S. 2007. Nutrition and hydration concerns of the female football player. British Journal of Sports Medicine 41 (Supplement 1):60–63. Meadows, M. 2007. How the FDA works to keep produce safe. FDA Consumer 41 (2):13–19. Meadows, M. 2002. Plastics and the microwave. FDA Consumer 36 (6):30. Messina, V., and Mangels, A. 2001. Considerations in planning vegan diets: Children. Journal of the American Dietetic Association 110:661–69.

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Michels, K., et al. 2007. Diet and breast cancer: A review of the prospective observational studies. Cancer 109:2712–49. Mozaffarian, D., and Rimm, E. 2006. Fish intake, contaminants, and human health: Evaluating the risks and the benefits. Journal of the American Medical Association 296:1885–99. Needham, L., et al. 2005. Concentrations of environmental chemicals associated with neurodevelopmental effects in U.S. population. Neurotoxicology 26:531–45. Nesheim, M. C. 1999. What is the research base for the use of dietary supplements? Public Health Nutrition 2:35–38. Neuhouser, M. 2004. Dietary flavonoids and cancer risk: Evidence from human population studies. Nutrition and Cancer 50:1–7. Nicklas, T. A., et al. 1998. Nutrient contribution of breakfast, secular trends, and the role of ready-toeat cereals: A review of data from the Bogalusa Heart Study. American Journal of Clinical Nutrition 67:757S–763S. Ortega, R. 2006. Importance of functional foods in the Mediterranean diet. Public Health Nutrition 9:1136–40. Parnes, R., and Lichtenstein, A. 2004. Food irradiation: A safe and useful technology. Nutrition in Clinical Care 7:149–55. Petrie, H., et al. 2004. Nutritional concerns for the child and adolescent competitor. Nutrition 20:620–31. Reedy, J., and Krebs-Smith S. 2008. A comparison of food-based recommendations and nutrient values of three food guides: USDA’s MyPyramid, NHLBI’s Dietary Approaches to Stop Hypertension Eating Plan, and Harvard’s Healthy Eating Pyramid. Journal of the American Dietetic Association 108:522–28. Roberts, W. O. 2007. Can children and adolescents run marathons? Sports Medicine 37:299–301. Rock, C. 2007. Multivitamin-multimineral supplements: Who uses them? American Journal of Clinical Nutrition 85:277S–79S. Rosenbloom, C., et al. 2006. Special populations: The female player and the youth player. Journal of Sports Sciences 24:783–93. Schardt, D. 2007. Organic foods: Worth the price? Nutrition Action Health Letter 34 (6):3–8. Seal, C. 2006. Whole grains and CVD risk. Proceedings of the Nutrition Society 65:24–34. Seiler, S., et al. 2007. The fall and rise of the gender difference in elite anaerobic performance 1952–2006. Medicine& Science in Sports & Exercise 39:534–40. Skibola, C., and Smith, M. 2000. Potential health impacts of excessive flavonoid intake. Free Radicals in Biology and Medicine 29:375–83. Smith, A. 2006. Veganism and osteoporosis: A review of the current literature. International Journal of Nursing Practice 12:302–6. Thomas, P. 1996. Food for thought about dietary supplements: Scientific review. Nutrition Today 31 (March/April):46–54. Thompson, L. 2000. Are bioengineered foods safe? FDA Consumer 34 (1):18–23.

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Truswell, A. 2002. Meat consumption and cancer of the large bowel. European Journal of Clinical Nutrition 56:S19–24. Tufts University. 2008. Can you afford to eat right? Health & Nutrition Letter 26 (3):4–5. Tufts University. 2007. Eating to beat cancer. Health & Nutrition Letter 25 (3):Special. Tufts University. 2007. Five new reasons to get whole grains. Health & Nutrition Letter 25 (6):1–2. Tufts University. 2005. Beef: Is it still what’s for dinner? Tufts University Health & Nutrition Letter 23 (8): Supplement, 1–4. Van Duyn, M., and Pivonka, E. 2000. Overview of the health benefits of fruit and vegetable consumption for the dietetics professional: Selected literature. Journal of the American Dietetic Association 100:1511–21. Van Maele-Fabry, G., et al. 2006. Review and metaanalysis of risk estimates for prostate cancer in pesticide manufacturing workers. Cancer Causes & Control 17:353–73. Venderley, A., and Campbell, W. 2006. Vegetarian diets: Nutritional considerations for athletes. Sports Medicine 36:293–305. Volek, J., et al. 2006. Nutritional aspects of women strength athletes. British Journal of Sports Medicine 40:742–48. Weiss, B., et al. 2004. Pesticides. Pediatrics 113:1030–36. Willett, W. 2006. The Mediterranean diet: Science and practice. Public Health & Nutrition 9:105–10. Williams, C. 2006. Nutrition to promote recovery from exercise. Sports Science Exchange 19 (1):1–6. Williams, C. 2002. Nutritional quality of organic food: Shades of grey or shades of green? Proceedings of the Nutrition Society 61:19–24. Williams, M. 2008. Nutrition for the School Aged Child Athlete. In The Young Athlete, eds. H. Hebestreit and O. Bar-Or. Oxford: Blackwell Publishing. Wilson, B., and Bahna, S. 2005. Adverse reactions to food additives. Annals of Allergy, Asthma & Immunology 95:499–507. Wood, O., and Bruhn, C. 2000. Position of the American Dietetic Association: Food irradiation. Journal of the American Dietetic Association 100:246–53. Woolf, S. 2006. Weighing the evidence to formulate dietary guidelines. Journal of the American College of Nutrition 25:277S–84S. Worthington, V. 2001. Nutritional quality of organic versus conventional fruits, vegetables, and grains. Journal of Alternative and Complementary Medicine 7:161–73. Yates, A. A., et al. 1998. Dietary Reference Intakes: The new basis for recommendations for calcium and related nutrients, B vitamins, and choline. Journal of the American Dietetic Association 98:699–706.

Specific Studies Appel, L., et al. 2005. Effects of protein, monounsaturated fat, and carbohydrate intake on blood pressure and serum lipids: results of the OmniHeart randomized trial. Journal of the American Medical Association 294:2455–64.

C H A P T E R 2 Healthful Nutrition for Fitness and Sport

Baker, B., et al. 2002. Pesticide residues in conventional, integrated pest management (IPM)-grown and organic foods: Insights from three US data sets. Food Additives and Contaminants 19:427–46. Bazzano, L., et al. 2002. Fruit and vegetable intake and risk of cardiovascular disease in US adults: The first National Health and Nutrition Examination Survey Epidemiologic Follow-up Study. American Journal of Clinical Nutrition 76:93–99. Bray, G., et al. 2007. Hormonal responses to a fastfood meal compared with nutritionally comparable meals of different composition. Annals of Nutrition & Metabolism 51:163–71. Chao, A., et al. 2005. Meat consumption and risk of colorectal cancer. JAMA 293:172–82. Cho, E., et al. 2006. Red meat intake and risk of breast cancer among premenopausal women. Archives of Internal Medicine 166:2253–59. Dragsted, L., et al. 2006. Biological effects of fruits and vegetables. Proceedings of the Nutrition Society 65:61–67. Jensen, M., et al. 2004. Intakes of whole grains, bran, and germ and the risk of coronary heart disease in men. American Journal of Clinical Nutrition 80:1492–99. Maffucci, D.M., and McMurray, R.G. 2000. Towards optimizing the timing of the pre-exercise meal. International Journal of Sport Nutrition and Exercise Metabolism 10:103–13. Martins, Y., et al. 1999. Restrained eating among vegetarians: Does a vegetarian eating style mask concerns about weight? Appetite 32:145–54. McCann, D., et al. 2007. Food additives and hyperactive behaviour in 3-year-old and 8/9-year-old children in the community: a randomised, doubleblinded, placebo-controlled trial. Lancet 370:1560–67. Neuhouser, M. L., et al. 1999. Use of food nutrition labels is associated with lower fat intake. Journal of the American Dietetic Association 99:45–53. Newberry, H., et al. 2001. Use of nonvitamin, nonmineral dietary supplements among college students. Journal of the American College of Health 50:123–29. Nicholls, S., et al. 2006. Consumption of saturated fat impairs the anti-inflammatory properties of high-density lipoproteins and endothelial function. Journal of the American College of Cardiology 48:715–20. Pereira, M., et al. 2005. Fast-food habits, weight gain, and insulin resistance (the CARDIA study): 15-year prospective analysis. The Lancet 365:36–42. Rothman, R., et al. Patient understanding of food labels: The role of literacy and numeracy. American Journal of Preventive Medicine 31:391–98. Schabort, E. J., et al. 1999. The effect of a preexercise meal on time to fatigue during prolonged cycling exercise. Medicine & Science in Sports & Exercise 31:464–71. Steck, S., et al. 2007. Cooked meat and risk of breast cancer—lifetime versus recent dietary intake. Epidemiology 18:373–82. Taylor, E., et al. 2007. Meat consumption and risk of breast cancer in the UK Women’s Cohort Study. British Journal of Cancer 96:1139–46.

Human Energy

K E Y

T E R M S

adenosine triphosphate (ATP) 91 aerobic glycolysis 93 aerobic lipolysis 94 anaerobic glycolysis 93 ATP-PCr system 92 basal energy expenditure (BEE) 96 basal metabolic rate (BMR) 96 Calorie (kilocalorie) 89 calorimetery 88 chronic fatigue syndrome 110 crossover concept 110 dietary-induced thermogenesis (DIT) 96 electron transfer system 93 energy 86

CHAPTER THREE L E A R N I N G

O B J E C T I V E S

After studying this chapter, you should be able to: 1. Understand the interrelationships among the various forms of chemical, thermal, and mechanical energy, and be able to perform mathematical conversions from one form of energy to another. 2. Identify the three major human energy systems, their major energy sources as stored in the body, and various nutrients needed to sustain them. 3. List the components of total daily energy expenditure (TDEE) and how each contributes to the total amount of caloric energy expended over a 24-hour period. 4. Describe the various factors that may influence resting energy expenditure (REE). 5. List and explain the various means whereby energy expenditure during exercise, or the thermic effect of exercise (TEE), may be measured, and be able to calculate conversions among the various methods. 6. Describe the three different muscle fiber types and the major characteristics of each in relation to energy production during exercise. 7. Explain the relationship between exercise intensity, particularly walking and running, and energy expenditure, and relate walking and running intensity to other types of physical activities. 8. Understand the concept of the physical activity level (PAL) and how it relates to estimated energy expenditure (EER). Calculate your EER based on an estimate of your PAL and the physical activity coefficient (PA). 9. Describe the role of the three energy systems during exercise. 10. Explain the various causes of fatigue during exercise and discuss nutritional interventions that may help delay the onset of fatigue.

ergometer 87 estimated energy requirement (EER) 106 exercise metabolic rate (EMR) 99 fatigue 110 glycolysis 93 joule 87 kilojoule 89 Krebs cycle 93 lactic acid system 93 maximal oxygen uptake 100 metabolic aftereffects of exercise 105 metabolism 96 METS 101 mitochondria 93 nonexercise activity thermogenesis (NEAT) 106 onset of blood lactic acid (OBLA) 100 oxygen system 93 phosphocreatine (PCr) 91 physical activity level (PAL) 106 power 87 resting energy expenditure (REE) 96 resting metabolic rate (RMR) 96 steady-state threshold 100 thermic effect of exercise (TEE) 99 thermic effect of food (TEF) 96 total daily energy expenditure (TDEE) 96 VO2 max 100 work 86

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Introduction As noted in chapter 1, the body uses the food we eat to provide energy, to build and repair tissues, and to regulate metabolism. Of these three functions, the human body ranks energy production first and will use food for this purpose at the expense of the other two functions in time of need. Energy is the essence of life. Through technological processes, humans have harnessed a variety of energy sources such as wind, waterfalls, the sun, wood, and oil to operate the machines invented to make life easier. However, humans cannot use any of these energy sources for their own metabolism but must rely on food sources found in nature. The food we eat must be converted into energy forms that the body can use. Thus, the human body is equipped with a number of metabolic systems to produce and regulate energy for its diverse needs, such as synthesis of tissues, movement of substances between tissues, and muscular contraction. Sport energy! The underlying basis for the control of movement in all sports is human energy, and successful performance depends upon the ability of the athlete to produce the right amount of energy and to control its application to the specific demands of the sport. Sports differ in their energy demands. In some events, such as

the 100-meter dash, success is dependent primarily upon the ability to produce energy very rapidly. In others, such as the 26.2-mile marathon, energy need not be produced so rapidly but must be sustained at an optimal rate for a much longer period. In still other sports, such as golf, the athlete need not only produce energy at varying rates (compare the drive with the putt) but must carefully control the application of that energy. Thus, each sport imposes specific energy demands upon the athlete. A discussion of the role of nutrition as a means to help provide and control human energy is important from several standpoints. First, inadequate supplies of necessary energy nutrients, such as muscle glycogen or blood glucose, may cause fatigue. Fatigue also may be caused by the inability of the energy systems to function optimally because of a deficiency of other nutrients, such as selected vitamins and minerals. In addition, the human body is capable of

Measures of Energy What is energy? For our purposes, energy represents the capacity to do work. Work is one form of energy, often called mechanical or kinetic energy. When we throw a ball or run a mile, we have done work; we have produced mechanical energy. Energy exists in a variety of other forms in nature, such as the light energy of the sun, nuclear energy in uranium, electrical energy in lightning storms, heat energy in fires, and chemical energy in oil. The six forms of energy—mechanical, chemical, heat, electrical, light, and nuclear—are interchangeable according to various laws of thermodynamics. We take advantage of these laws every day. One such example is the use of the chemical energy in gasoline to produce mechanical energy—the movement of our cars. In the human body, four of these types of energy are important. Our bodies possess stores of chemical energy that can be used to

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storing energy reserves in a variety of body forms, including body fat and muscle tissue. Excess body weight in the form of fat or decreased body weight due to losses of muscle tissue may adversely affect some types of athletic performance. One purpose of this chapter is to review briefly the major human energy systems and how they are used in the body under conditions of exercise and rest. Following this, chapters 4 through 9 discuss the role of each of the major classes of nutrients as they relate to energy production in the human body, with the primary focus on prevention of fatigue caused by impaired energy production; chapter 13 details the effects of various food drugs and supplements on human energy systems. Another purpose of this chapter is to discuss the means by which humans store and expend energy. Chapters 10 through 12 focus on weight control methods and expand on some of the concepts presented in this chapter.

produce electrical energy for creation of electrical nerve impulses, to produce heat energy to help keep our body temperature at 37°C (98.6°F) even on cold days, and to produce mechanical energy through muscle shortening so that we may move about. The sun is the ultimate source of energy. Solar energy is harnessed by plants, through photosynthesis, to produce either plant carbohydrates, fats, or proteins, all forms of stored chemical energy. When humans consume plant and animal foods, the carbohydrates, fats, and proteins undergo a series of metabolic changes and are utilized to develop body structure, to regulate body processes, or to provide a storage form of chemical energy (figure 3.1). The optimal intake and output of energy is important to all individuals, but especially for the physically active person. To perform to capacity, body energy stores must be used in the most efficient manner possible.

Sun (solar energy)

TABLE 3.1

Animals (chemical energy) carbohydrates fats protein

Plants (chemical energy)

Humans (chemical energy)

carbohydrates fats protein

carbohydrates fats protein ATP-PCr

F I G U R E 3 . 1 Through photosynthesis, plants utilize solar energy and convert it to chemical energy in the form of carbohydrates, fats, or proteins. Animals eat plants and convert the chemical energy into their own stores of chemical energy—primarily fat and protein. Humans ingest food from both plant and animal sources and convert the chemical energy for their own stores and use.

How do we measure work, physical activity, and energy expenditure? Energy has been defined as the ability to do work. According to the physicist’s definition, work is simply the product of force times vertical distance, or in formula format, Work = Force × Distance. When we speak of how fast work is done, the term power is used. Power is simply work divided by time, or Power = Work/Time. Two major measurement systems have been used in the past to express energy in terms of either work or power. The metric system has been in use by most of the world, while England, its colonies, and the United States have used the English system. In an attempt to provide some uniformity in measurement systems around the world, the International Unit System (Systeme International d’Unites, or SI) has been developed. Most of the world has adopted the SI. Although legislation has been passed by Congress to convert the United States to the SI, and terms such as gram, kilogram, milliliter, liter, and kilometer are becoming more prevalent, it appears that it will take some time before this system becomes part of our everyday language. The SI is used in most scientific journals today, but the other two systems appear in older journals. Terms that are used in each system are presented in table 3.1. For our purposes in this text, we shall use several English terms that are still in common usage in the United States, but if you read scientific literature, you should be able to convert values among the various systems if necessary. For example, work may be expressed as either foot-pounds, kilogram-meters

Terms in the English, metric, and international systems

Unit

English system

Metric system

International system

Mass

slug

kilogram (kg)

kilogram (kg)

Distance

foot (ft)

meter (m)

meter (m)

Time

second (s)

second (s)

second (s)

Force

pound (lb)

newton (N)

newton (N)

Work

foot-pound (ft-lb)

kilogram-meter (kgm)

joule (J)

Power

horsepower (hp)

watt (W)

watt (W)

(kgm), joules, or watts. If you weigh 150 pounds and climb a 20-foot flight of stairs in one minute, you have done 3,000 foot-pounds of work. One kgm is equal to 7.23 foot-pounds, so you would do about 415 kgm. One joule is equal to about 0.102 kgm, so you have done about 4,062 joules of work. One watt is equal to one joule per second, so you have generated about 68 watts of power. Some basic interrelationships among the measurement systems are noted in table 3.2. Other equivalents may be found in appendix A. In general, exercise and nutrition scientists are interested in measuring work output and energy expenditure under two conditions. One condition involves specific techniques in controlled laboratory research, whereas the other condition involves normal daily activities, including actual sports performance. To measure work we need to know the weight of an object and the vertical distance through which it is moved. This is fine according to the formal definition of work, but are you doing work while holding a stationary weight out in front of your body? According to the formal definition, the answer is no, because the distance the weight moved is zero. How about when you come down stairs as compared to going up? It is much easier to descend the stairs, and yet according to the formula you have done the same amount of work. Also, how about when you run a mile? You know you have worked, but most of the distance you covered was horizontal, not vertical. To accurately measure work output under laboratory conditions, scientists use devices known as ergometers. An ergometer, such as a cycle or arm ergometer, is designed to provide accurate measurements of work, including measures of power and total work output over specific periods of time. To measure work output during normal daily physical activity, devices such as pedometers and accelerometers have been developed. They are attached to the body and detect motion throughout the day, providing an estimate of total daily work output. However, research comparing such devices to more accurate determinations of energy expenditure has shown that they may underestimate energy expenditure for some activities and overestimate it for others. For example, Leenders and others compared the use of various accelerometers to the doublly labeled water method, a gold standard method discussed later, as a measure of total daily energy expenditure, and found that the www.mhhe.com/williams9

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TABLE 3.2

Some interrelationships between work measurement systems

Weight

Distance

Work

Power

1 kilogram = 2.2 pounds

1 meter = 3.28 feet

1 kgm = 7.23 foot-pounds

1 watt = 1 joule per second

1 kilogram = 1,000 grams

1 meter = 1.09 yards

1 kgm = 9.8 joules

1 watt = 6.12 kgm per minute 1 watt = 0.0013 horsepower

454 grams = 1 pound

1 foot = 0.30 meter

1 foot-pound = 0.138 kgm

1 horsepower = 550 footpounds per second

1 pound = 16 ounces

1,000 meters = 1 kilometer

1 foot-pound = 1.35 joules

1 horsepower = 33,000 footpounds per minute

1 ounce = 28.4 grams

1 kilometer = 0.6215 mile

1 newton = 0.102 kg

1 horsepower = 745.8 watts

3.5 ounces = 100 grams

1 mile = 1.61 kilometers 1 inch = 2.54 centimeters 1 centimeter = 0.39 inch

1 joule = 1 newton meter 1 kilojoule = 1,000 joules 1 megajoule = 1,000,000 joules 1 joule = 0.102 kgm 1 joule = 0.736 foot-pound 1 kilojoule = 102 kgm

differences between the methods were large and variable. They noted that the results reemphasize the difficulty in converting body movement into energy expenditure. However, although they indicated that accelerometers should not be used by researchers to predict energy expenditure in free-living conditions, they may be used to measure patterns of physical activity. Also, as we shall see in chapter 11, such devices may be helpful in weight-control programs. Moreover, newer techniques are being developed. For example, Zhang and others indicated that the Intelligent Device for Energy Expenditure and Activity (IDEEA), a portable device that records body motion and postural changes second by second on a 24-hour basis, has shown promise as a means to evaluate total daily body energy expenditure. Additionally, Global Positioning Systems (GPS) have recently been used in conjunction with accelerometers to help improve accuracy of recording daily physical activity. Nevertheless, measuring work output is not the same as measuring energy expenditure, and so we need to have means to express the energy expenditure of the human body other than simply the amount of work done. Several methods are available to measure energy expenditure in humans. One is calorimetry, which measures heat energy. Figure 3.2 illustrates a bomb calorimeter, which may be used to measure the energy content of a given substance. For example, a gram of fat contains a certain amount of chemical energy. When placed in the calorimeter and oxidized completely, the heat it gives off can be recorded. We then know the heat energy of one gram of fat and can equate it to chemical or work units of energy if needed. Large, expensive whole-room calorimeters (metabolic chambers) are available that can accommodate human beings and measure their heat production under normal home activities and some conditions of exercise. This technique is known as direct calorimetry. A second, more commonly used method of measuring energy expenditure is to determine the amount of oxygen an individual 88

C H A P T E R 3 Human Energy

consumes, an indirect calorimetry technique. This procedure is normally done under laboratory conditions (see figure 3.3), but lightweight portable oxygen analyzers are also available to record energy expenditure in freely moving individuals. The volume of oxygen one uses is usually expressed in liters (L) or milliliters (ml); one L is equal to 1,000 ml. One liter is slightly larger than a quart. In

Thermometer

Insulation around chamber Air space

Wire to ignite food

Chamber for food Water

F I G U R E 3 . 2 A bomb calorimeter.The food in the calorimeter is combusted via electrical ignition.The heat (Calories) given off by the food raises the temperature of the water, thereby providing data about the caloric content of specific foodstuffs.

Indirect calorimetry may be used to measure metabolism by determining the amount of oxygen consumed and the carbon dioxide produced.The test may also be used to measure VO2 max and other measures of cardiovascular and respiratory function.

FIGURE 3.3

What is the most commonly used measure of energy? Although there are a number of different ways to express energy, the most common term used in the past and still most prevalent and understood in the United States by most people is Calorie. A calorie is a measure of heat. One gram calorie represents the amount of heat needed to raise the temperature of one gram of water one degree Celsius. A kilocalorie is equal to 1,000 small calories. It is the amount of heat needed to raise 1 kg of water (1 L) one degree Celsius. In human nutrition, because the gram calorie is so small, the kilocalorie is the main expression of energy. It is usually abbreviated as kcal, kc, or C, or capitalized as Calorie. Throughout this book, Calorie or C will refer to the kilocalorie. According to the principles underlying the first law of thermodynamics, energy may be equated from one form to another. Thus, the Calorie, which represents thermal or heat energy, may be equated to other forms of energy. Relative to our discussion concerning physical work such as exercise and its interrelationships with nutrition, it is important to equate the Calorie with mechanical work and the chemical energy stored in the body. As will be explained later, most stored chemical energy must undergo some form of oxidation in order to release its energy content as work. The following represents some equivalent energy values for the Calorie in terms of mechanical work and oxygen utilization. Some examples illustrating several of the interrelationships will be used in later chapters. 1 C = 3,086 foot-pounds 1 C = 427 kgm 1 C = 4.2 kilojoules (kJ) or 4,200 joules

general, humans need oxygen, which helps metabolize the various nutrients in the body to produce energy. It is known that when oxygen combines with a gram of carbohydrate, fat, or protein, a certain amount of energy is released. If we can accurately measure the oxygen consumption (and carbon dioxide production) of an individual, we can get a pretty good measure of energy expenditure. The amount of oxygen used can be equated to other forms of energy, such as work done in foot-pounds or heat produced in Calories. Another method is the doubly labeled water (DLW) technique in which stable isotopes of hydrogen and oxygen in water (2H218O) are ingested. This is a safe procedure as the isotopes are stable and emit no radiation. Analysis of urine and blood samples provide data on 2H and 18O excretion. The labeled oxygen is eliminated from the body as water and carbon dioxide, whereas the hydrogen is eliminated only as water. Subtracting the hydrogen losses from the oxygen losses provides a measure of carbon dioxide fluctuation, which may be converted to energy expenditure. Although expensive, the advantage of this technique is that it may be used with individuals while they perform their normal daily activities, and they need not be confined to a metabolic chamber or be attached to equipment to measure oxygen consumption. Although all of these techniques to measure work and energy expenditure have limitations, they do provide useful data relative to the approximate energy cost of exercise and normal daily activities.

1 C = 200 ml oxygen (approximately) Although the Calorie is the most commonly used expression in the United States for energy, work, and heat, the kilojoule is the proper term in the SI and is used by the rest of the world. It is important for you to be able to convert from Calories to kilojoules, and vice versa. To convert Calories to kilojoules, multiply the number of Calories by 4.2 (4.186 to be exact); to convert kilojoules to Calories, divide the number of kilojoules by 4.2. Simply multiplying or dividing by 4 for each respective conversion will provide a ballpark estimate. In some cases megajoules (MJ), a million joules, are used to express energy. One MJ equals about 240 Calories, or 4.2 MJ is the equivalent of about 1,000 Calories. Through the use of a calorimeter, the energy contents of the basic nutrients have been determined. Energy may be derived from the three major foodstuffs—carbohydrate, fat, and protein— plus alcohol. The caloric value of each of these three nutrients may vary somewhat, depending on the particular structure of the different forms. For example, carbohydrate may exist in several forms—as glucose, sucrose, or starch—and the caloric value of each will differ slightly. In general, one gram of each of the three nutrients and alcohol, measured in a calorimeter, yields the following Calories: 1 gram carbohydrate = 4.30 C 1 gram fat = 9.45 C www.mhhe.com/williams9

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1 gram protein = 5.65 C 1 gram alcohol = 7.00 C Unfortunately, or fortunately if one is trying to lose weight, humans do not extract all of this energy from the food they eat. The human body is not as efficient as the calorimeter. For one, the body cannot completely absorb all the food eaten. Only about 97 percent of ingested carbohydrate, 95 percent of fat, and 92 percent of protein are absorbed. In addition, a good percentage of the protein is not completely oxidized in the body, with some of the nitrogen waste products being excreted in the urine. In summary, then, the caloric value of food is reduced somewhat in relation to the values given previously. Although the following values are not exactly precise, they are approximate enough to be used effectively in determining the caloric values of the foods we eat. Thus, the following caloric values Carbohydrate are used throughout this text as a 4 kcal per gram practical guide: Protein 4 kcal per gram

1 gram carbohydrate = 4 C 1 gram fat = 9 C

Energy sources for body functions

Fat 9 kcal per gram

Alcohol 7 kcal per gram

1 gram protein = 4 C 1 gram alcohol = 7 C

For our purposes, the Calories in food represent a form of potential energy to be used by our bodies to produce heat and work (figure 3.4). However, the fact that fat has about twice the amount of energy per gram as carbohydrate (figure 3.5) does not mean that it is a better energy source for the active individual, as we shall see in later chapters when we talk of the efficient utilization of body fuels. Eight ounces of orange juice will provide enough chemical energy to enable an average man to produce enough mechanical energy to run about one mile.

FIGURE 3.4

1 teaspoon sugar = 5 grams carbohydrate = 20 Calories

1 teaspoon salad oil = 5 grams fat = 45 Calories

FIGURE 3.5

The Calorie as a measure of energy.

Ke y C o n c e p t s 䉴 Energy represents the capacity to do work, and food is the

source of energy for humans. 䉴 Energy expenditure in humans may be measured in a variety of

ways, including both direct and indirect calorimetry and the doubly labeled water technique, all of which provide accurate measurements. 䉴 The Calorie, or kilocalorie, is a measure of chemical energy stored in foods; this chemical energy can be transformed into heat and mechanical work energy in the body. A related measure is the kilojoule. One Calorie is equal to 4.2 kilojoules. 䉴 Carbohydrates and fats are the primary energy nutrients, but protein may also be an energy source during rest and exercise. In the human body 1 gram of carbohydrate ⫽ 4 Calories, 1 gram of fat ⫽ 9 Calories, and 1 gram of protein ⫽ 4 Calories. Alcohol is also a source of energy; 1 gram ⫽ 7 Calories.

C h e c k f o r Yo u r s e l f Measure the height of a step on a flight of stairs or bleachers and convert it to feet (9 inches = 0.75 foot). Stepping in place, count the total number of steps you do in one minute. Multiply your count by the step height to determine the number of feet you have climbed. Next, multiply this value by your body weight in pounds to determine the number of foot-pounds of work you have done. Then, convert this number of foot-pounds to the equivalent amount of kilogram-meters (kgm), kilojoules (kJ), and Calories.

Human Energy Systems How is energy stored in the body? The ultimate source of all energy on earth is the sun. Solar energy is harnessed by plants, which take carbon, hydrogen, oxygen, and nitrogen from their environment and manufacture either carbohydrate, fat, or protein. These foods possess stored energy. When we consume these foods, our digestive processes break them down into simple compounds that are absorbed into the body and transported to various cells. One of the basic purposes of body cells is to transform the chemical energy of these simple compounds into

forms that may be available for immediate use or other forms that may be available for future use. Energy in the body is available for immediate use in the form of adenosine triphosphate (ATP). It is a complex molecule constructed with high-energy bonds, which, when split by enzyme action, can release energy rapidly for a number of body processes, including muscle contraction. ATP is classified as a high-energy compound and is stored in the tissues in small amounts. It is important to note that ATP is the immediate source of energy for all body functions, and the other energy stores are used to replenish ATP at varying rates. Myburgh notes that muscle contraction is totally dependent on ATP, so the body has developed an intricate system to help replenish ATP as rapidly as needed. Another related high-energy phosphate compound, phosphocreatine (PCr), is also found in the tissues in small amounts. Although it cannot be used as an immediate source of energy, it can rapidly replenish ATP. ATP may be formed from either carbohydrate, fat, or protein after those nutrients have undergone some complex biochemical changes in the body. Figure 3.6 represents a basic schematic of how ATP is formed from each of these three nutrients. PCr is actually derived from excess ATP. Because ATP and PCr are found in very small amounts in the body and can be used up in a matter of seconds, it is important to have adequate energy stores as a backup system. Your body stores of carbohydrate, fat, and protein can provide you with ample amounts of ATP, enough to last for many weeks even on a starvation diet. The digestion and metabolism of carbohydrate, fat, and protein are discussed in their respective chapters, so it is unnecessary to present that full discussion here. However, you may wish to preview figure 3.12 in order to visualize the metabolic interrelationships between the three nutrients in the body. For those who desire more detailed schematics of energy pathways, appendix G provides some of the major metabolic pathways for carbohydrate, fat, and protein. It is important to note that parts of each energy nutrient may be converted to the other two nutrients in the body under certain circumstances. For example, protein may be converted into carbohydrate during prolonged exercise, whereas excess dietary carbohydrate may be converted to fat in the body during rest. Table 3.3 summarizes how much energy is stored in the human body as ATP, PCr, and various forms of carbohydrate, fat, and protein. The total amount of energy, represented by Calories, is approximate and may vary considerably between individuals. Carbohydrate is stored in limited amounts as blood (serum) glucose, liver glycogen, and muscle glycogen. The largest amount of energy is stored in the body as fats. Fats are stored as triglycerides in both muscle tissue and adipose (fat) tissue; triglycerides and free fatty acids (FFA) in the blood are a limited supply. The protein of the body tissues, particularly muscle tissue, is a large reservoir of energy but is not used to any great extent under normal circumstances. Table 3.3 also depicts how far an individual could run using the total of each of these energy sources as the sole supply. The role of each of these macronutrient energy stores during exercise is an important consideration that is discussed briefly in this chapter and more extensively in their respective chapters.

Protein

Carbohydrate

Fat

Glucose ATP

Amino acids

Fatty acids

Acetyl CoA

Krebs cycle Electron transport chain

ATP

F I G U R E 3 . 6 Simplified schematic of ATP formation from carbohydrate, fat, and protein. All three nutrients may be used to form ATP, but carbohydrate and fat are the major sources via the aerobic metabolism of the Krebs cycle. Carbohydrate may be used to produce small amounts of ATP under anaerobic conditions, thus providing humans with the ability to produce energy rapidly without oxygen for relatively short periods. For more details, see appendix G.

What are the human energy systems? Why does the human body store chemical energy in a variety of different forms? If we look at human energy needs from an historical perspective, the answer becomes obvious. Sometimes humans needed to produce energy at a rapid rate, such as when sprinting to safety to avoid dangerous animals. Thus, a fast rate of energy production was an important human energy feature that helped ensure survival. At other times, our ancient ancestors may have been deprived of adequate food for long periods, and thus needed a storage capacity for chemical energy that would sustain life throughout these times of deprivation. Hence, the ability to store large amounts of energy was also important for survival. These two factors—rate of energy production and energy capacity— appear to be determining factors in the development of human energy systems. One need only watch weekend television programming for several weeks to realize the diversity of sports popular throughout the world. Each of these sports imposes certain requirements on humans www.mhhe.com/williams9

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TABLE 3.3

Major energy stores in the human body with approximate total caloric value*

Energy source

Major storage form

Total body Calories

Total body kilojoules

ATP

Tissues

1

4.2

PCr

Tissues

4

16.8

Carbohydrate

Serum glucose Liver glycogen Muscle glycogen

Fat

Protein

Distance covered** 17.5 yards 70 yards

20 400 1,500

88 1,680 6,300

350 yards 4 miles 15 miles

Serum-free fatty acids Serum triglycerides Muscle triglycerides Adipose tissue triglycerides

7 75 2,500 80,000

29.2 315 10,500 336,000

123 yards 0.75 mile 25 miles 800 miles

Muscle protein

30,000

126,000

300 miles

See text for discussion. *These values may have extreme variations depending on the size of the individual, amount of body fat, physical fitness level, and diet. **Running at an energy cost of 100 Calories per mile (1.6 kilometers).

who want to be successful competitors. For some sports, such as ATP breakdown. No matter what you do, scratch your nose or lift weight lifting, the main requirement is brute strength, while for others 100 pounds, ATP breakdown makes the movement possible. ATP such as tennis, quick reactions and hand/eye coordination are impormust be present for the muscles to contract. The body has a limited tant. A major consideration in most sports is the rate of energy prosupply of ATP and must replace it rapidly if muscular work is to conduction, which can range from the explosive power needed by a tinue.The main purpose of every other energy system, including PCr, shot-putter to the tremendous endurance capacity of an ultramais to help regenerate ATP to enable muscle contraction to continue at rathoner. The physical performance demands of different sports the optimal desired rate. require specific sources of energy. PCr, which is also a high-energy compound found in the muscle, As noted previously, the body stores energy in a variety of can help form ATP rapidly as ATP is used. Energy released when ways—in ATP, PCr, muscle glycogen, and so on. In order for this PCr splits is used to form ATP from ADP and P. PCr is also in short energy to be used to produce muscular contractions and movesupply (but more than ATP) and needs to be replenished if used. PCr ment, it must undergo certain biochemical reactions in the muscle. breakdown to help resynthesize ATP is illustrated in figure 3.8. These biochemical reactions serve as a basis for classifying The ATP-PCr system is critical to energy production. Because human energy expenditure by several energy, or power, systems. these phosphagens are in short supply, any all-out exercise for 5 to In the text Sports Physiology, one of the first to discuss the 10 seconds could deplete the supply, particularly PCr, in a given application of human energy systems to sport, Edward L. Fox muscle. Hence, the phosphagens must be replaced, and this is the named three human energy systems—the ATP-PCr system, the function of the other energy sources. Although some supplements, lactic acid system, and the oxygen system. As noted below, other terminology may be used to describe the metabolic relation1 ships to these three energy systems, but the original classification is still useful when discussing the application of human energy 2 to sport performance. The ATP-PCr system is also known as the phosphagen system because both adeno3 sine triphosphate (ATP) and phosphocreatine (PCr) contain phosphates. ATP is the immediate source of energy for almost all F I G U R E 3 . 7 ATP, adenosine triphosphate. (1) ATP is stored in the muscle in body processes, including muscle contraclimited amounts. (2) Splitting of a high-energy bond releases adenosine diphosphate tion. This high-energy compound, stored in (ADP), inorganic phosphate (P), and energy, which (3) can be used for many body the muscles, rapidly releases energy when an processes, including muscular contraction.The ATP stores may be used maximally for fast, electrical impulse arrives in the muscle. See all-out bursts of power that last about one second. ATP must be replenished from other figure 3.7 for a graphical representation of sources for muscle contraction to continue. 92

C H A P T E R 3 Human Energy

lactic acid is a by-product of the process necessary to increase ATP production. This process has been referred to as anaerobic, because of Cr 1 inadequate aerobic processing by the mitochondria, and the term anaerobic glycolysis has 2 Cr been used as a scientific term for the lactic acid energy system. The lactic acid system is diagrammed in fig3 ATP ure 3.9. It is used in sport events in which energy production is near maximal for 30–120 seconds, such as a 200- or 800-meter run. F I G U R E 3 . 8 Phosphocreatine (PCr). (1) PCr is stored in the muscle in limited amounts. (2) Splitting of the high-energy bond releases energy, which (3) can be used to Anaerobic capacity is a term often associated rapidly synthesize ATP from ADP and P. ATP and PCr are called phosphagens and together with the lactic acid energy system. represent the ATP-PCr energy system.This system is utilized primarily for quick, maximal The lactic acid system has the advantage of exercises lasting about 1 to 6 seconds, such as sprinting. producing ATP rapidly. Its capacity is limited in comparison to aerobic glycolysis, for only about 5 percent of the total ATP production from muscle glycogen can be released. Moreover, the lacGlycolysis tic acid produced as a by-product may be Blood glucose associated with the onset of fatigue, as discussed Carbohydrate Lactic acid (glycogen) later in this chapter. In brief, a prevailing hypothesis suggests anaerobic glycolysis ATP releases hydrogen ions, increasing the acidity within the muscle cell and disturbing the normal cell environment. The processes of energy F I G U R E 3 . 9 The lactic acid energy system. Muscle glycogen and glucose can break release and muscle contraction in the muscle cell down without the utilization of oxygen.This process is called anaerobic glycolysis. (See are controlled by enzymes whose functions may appendix G, figure G.1, for more details.) ATP is produced rapidly, but lactic acid is the end be impaired by the increased acidity in the cell. product. Lactic acid may be a major cause of fatigue in the muscle.The lactic acid energy However, it is important to note that the lactate system is utilized primarily during exercise bouts of very high intensity, those conducted at present after loss of the hydrogen ion still has maximal rates for about 30 to 120 seconds. considerable energy content, which may be used by other tissues for energy or converted back into glucose in the liver. such as creatine, discussed in later chapters are theorized to facilitate The third system is the oxygen system. It is also known as the ATP or PCr replenishment, we do not eat ATP-PCr per se, but we can oxidative or aerobic system. Aerobics is a term used by Dr. Kenneth produce it from the other nutrients stored in our body. PCr replenishCooper in 1968 to describe a system of exercising that created an ment will not be discussed, but keep in mind that when ATP is being exercise revolution in this country. In essence, aerobic exercises are regenerated, so is some PCr. In summary, the value of the ATP-PCr sysdesigned to stress the oxygen system and provide benefits for the tem is its ability to provide energy rapidly, for example, in sport events heart and lungs. Figure 3.10 represents the major physiological such as competitive weight lifting or sprinting 100 meters. Anaerobic processes involved in the oxygen system. The oxygen system, like power is a term often associated with the ATP-PCr energy system. the lactic acid system, cannot be used directly as a source of energy The lactic acid system cannot be used directly as a source of for muscle contraction, but it does produce ATP in rather large quanenergy for muscular contraction, but it can help replace ATP rapidly tities from other energy sources in the body. Muscle glycogen, liver when necessary. If you are exercising at a high intensity level and glycogen, blood glucose, muscle triglycerides, blood FFA and need to replenish ATP rapidly, the next best source of energy besides triglycerides, adipose cell triglycerides, and body protein all may be PCr is glucose. Glucose may enter the muscle from the bloodultimate sources of energy for ATP production and subsequent musstream, or may be derived from the breakdown of glycogen stored cle contraction. To do this, glycogen, fats, and protein must be presin the muscle. The glucose molecule undergoes a series of reactions ent within the muscle cell or must enter the muscle cell as glucose, to eventually form ATP, a process called glycolysis. One of the FFA, or amino acids. Through a complex series of reactions metamajor factors controlling the metabolic fate of glucose is the capacbolic by-products of carbohydrate, fat, or protein combine with oxyity of the mitochondria, which are cell organelles that need oxygen gen to produce energy, carbon dioxide, and water. These reactions to process glucose to ATP. If the muscle cell mitochondria can occur in the energy powerhouse of the cell, the mitochondrion. The process the available glucose, then adequate oxygen is assumed to whole series of events of oxidative energy production primarily be available. This is known as aerobic glycolysis. Conversely, if the involves aerobic processing of carbohydrates and fats (and small rate of glycolysis surpasses the capacity of mitochondrial oxidation amounts of protein) through the Krebs cycle and the electron to meet the energy demands of the exercise task or to maintain a transfer system. The oxygen system is depicted in figure 3.11. The high level of aerobic glycolysis, then insufficient ATP is formed and Krebs cycle and the electron transfer system represent a highly www.mhhe.com/williams9

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Respiration Lungs take in oxygen from the atmosphere. Cardiovascular 1 Central circulation. Heart pumps oxygenenriched blood.

Blood

2 Peripheral circulation. Arteries carry oxygenrich blood to muscle tissues. Amino no aci ac cid ds Gluco Gl cos ose se FFA FA Metabolism Muscle cells take in and use oxygen to produce energy (ATP) mainly from carbohydrates and fats, but also small amounts from protein.

FIGURE 3.10

Physiological processes involved in oxygen uptake.

structured array of enzymes designed to remove hydrogen, carbon dioxide, and electrons from substrates such as glucose. At different steps in this process, energy is released and ATP is formed, with most of the ATP produced during the electron transfer process. The hydrogen and electrons eventually combine with oxygen to form water (see appendix G for more details). Although the rate of ATP production is lower, the major advantage of the oxygen system over the other two energy systems is the production of large amounts of energy in the form of ATP. However, oxygen from the air we breathe must be delivered to the muscle cells deep in the body and enter the mitochondria to be used. This process may be adequate to handle mild and moderate levels of exercise but may not be able to meet the demand of very strenuous exercise. The oxygen system is used primarily in sports emphasizing endurance, such as distance runs ranging from 5 kilometers (3.1 miles) to the 26.2-mile marathon and beyond. Hawley and Hopkins subdivided the oxygen energy system into two systems. The scientific terms for these two subdivisions are aerobic glycolysis, which uses carbohydrates (muscle glycogen and blood glucose) for energy production, and aerobic lipolysis, which uses fats (muscle triglycerides, blood FFA). As discussed in the next two chapters, carbohydrate is the more effi94

C H A P T E R 3 Human Energy

Krebs cycle and ETS

O2

F I G U R E 3 . 1 1 The oxygen energy system.The muscle stores of glycogen and triglycerides, along with blood supplies of glucose and free fatty acids (FFA), as well as small amounts of muscle protein and amino acids, undergo complex biochemical changes for entrance into the Krebs cycle and the associated electron transfer system (ETS). In this process, in which oxygen is the final acceptor to the electron, large amounts of ATP may be produced.The oxygen energy system is utilized primarily during endurance-type exercises, those lasting longer than 4 or 5 minutes. (See appendix G for more details.)

cient fuel during high-intensity exercise, whereas fat becomes the predominant fuel used at lower levels of exercise intensity. Thus, aerobic glycolysis provides most of the energy in high-intensity aerobic running events such as 5 kilometers (3.1 miles), 10 kilometers (6.2 miles), and even races up to two hours, while aerobic lipolysis may contribute significant amounts of energy in more prolonged aerobic events, such as ultramarathons of 50 to 100 kilometers (31 to 62 miles). Aerobic glycolysis and aerobic lipolysis may respectively be referred to as aerobic power and aerobic capacity. Details relative to the role of these energy systems during exercise are presented in chapters 4 and 5. Figure 3.12 presents a simplified schematic reviewing the three human energy systems. The energy systems for exercise are discussed later in this chapter, but in brief, human energy systems for exercise may be classified as anaerobic or aerobic, and each may be subdivided into energy systems for power and capacity as follows:

energy transformation and utilization would not occur without the participation of the other major nutrients—water, vitamins, and minerals. These three classes of nutrients function very closely with protein in the Blood structure and function of numerous Glucose Free fatty acids Amino acids Oxygen enzymes, many of which are active in the muscle-cell energy processes. Water is used to help break up and transform some energy compounds by a process known as hydrolysis. Muscle Acetyl CoA Several vitamins are needed for energy glycogen to be released from the cell sources. For example, niacin serves an important function in glycolysis, thiamin is needed to convert glycolytic end products to acetyl CoA Lactic acid for entrance into the Krebs cycle, and riboflavin is essential to forming ATP 2 Krebs through the Krebs cycle and electron transATP cycle fer system. A number of other B vitamins Electron are also involved in facets of energy transCO2 3 transport formation within the cell. system H2O ATP Minerals, too, are essential for cellular energy processes. Iron is one of the more critical compounds. Aside from helping 1 hemoglobin deliver oxygen to the muscle Phosphocreatine (PCr) ATP cell, it is also a component of myoglobin and ATP the cytochrome part of the electron transfer 1 system. It is needed for proper utilization of Energy for muscle contraction oxygen within the cell itself. Other minerals such as zinc, magnesium, potassium, F I G U R E 3 . 1 2 Simplified flow diagram of the three energy systems.The major sodium, and calcium are involved in a varinutrients and oxygen are transported to the cells for energy production. In the muscles, ATP ety of ways, either as parts of active is the immediate source of energy for muscle contraction. (1)The ATP-PCr system is enzymes, in energy storage, or in the musclerepresented by muscle stores of ATP and phosphocreatine (PCr); PCr can replenish ATP rapidly. contraction process. (2) Glucose or muscle glycogen can produce ATP rapidly via the lactic acid system. (3)The Proper utilization of body energy sources oxygen system can produce large amounts of ATP via the aerobic processes in the Krebs cycle, primarily oxidation of carbohydrate and fatty acids. Numerous other energy pathways exist, and requires attention not only to the major some are described in chapter 4 (carbohydrates), chapter 5 (fats), and chapter 6 (protein). energy nutrients but also to the regulatory nutrients—water, vitamins, and minerals. In addition, other nutrients and non-nutrients (such as creatine and • Anaerobic power—ATP-PCr energy system caffeine) found in food may affect energy metabolism. • Anaerobic capacity—Lactic acid energy system (anaerobic glycolysis) • Aerobic power—Aerobic glycolysis Ke y C o n c e p t s • Aerobic capacity—Aerobic lipolysis Liver

Adipose tissue

Active muscle

Lungs

Glucose

Triglycerides

Amino acids

Oxygen

As noted, protein may be used as an energy source during exercise, and has been referred to as aerobic proteolysis, but its contributions are considered minor and it is not classified here as a separate energy system. Its contributions to energy production during exercise are covered in chapter 6.

What nutrients are necessary for the operation of the human energy systems? Although the energy for the formation of ATP is derived from the energy stores in carbohydrate, fat, and sometimes protein, this

䉴 The potential energy sources in the body include ATP and PCr;

serum glucose; glycogen in the liver and muscle; serum-free fatty acids (FFA); triglycerides in the muscle and in adipose tissue; and muscle protein. 䉴 Three human energy systems have been classified on the basis of their ability to release energy at different rates of speed; they are the ATP-PCr, lactic acid, and oxygen energy systems.The ATP-PCr system is for anaerobic power; lactic acid system for anaerobic capacity; aerobic glycolysis system for aerobic power; and aerobic lipolysis system for aerobic capacity.

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Human Energy Metabolism during Rest What is metabolism? Human metabolism represents the sum total of all physical and chemical changes that take place within the body. The transformation of food to energy, the formation of new compounds such as hormones and enzymes, the growth of bone and muscle tissue, the destruction of body tissues, and a host of other physiological processes are parts of the metabolic process. Metabolism involves two fundamental processes, anabolism and catabolism. Anabolism is a building-up process, or constructive metabolism. Complex body components are synthesized from the basic nutrients. For the active individual, this may mean an increased muscle mass through weight training or an increased amount of cellular enzymes to better use oxygen following endurance-type training. Energy is needed for anabolism to occur. Catabolism is the tearing-down process. This involves the disintegration of body compounds into their simpler components. The breakdown of muscle glycogen to glucose and eventually CO2, H2O, and energy is an example of a catabolic process. The energy released from some catabolic processes is used to support the energy needs of anabolism. Metabolism is life. It represents human energy. The metabolic rate reflects how rapidly the body is using its energy stores, and this rate can vary tremendously depending upon a number of factors. For all practical purposes, the total daily energy expenditure (TDEE) may be accounted for by three factors: basal energy expenditure, increases due to eating a meal, and physical activity. Basal energy expenditure accounts for the largest component of TDEE, whereas physical activity is the most variable. We shall examine basal energy expenditure and the effect of eating in this section, while the role of physical activity, or exercise, will be covered in the section “Human Energy Metabolism during Exercise.”

What factors account for the amount of energy expended during rest? The body is constantly using energy to build up and tear down substances within the cells. Certain automatic body functions such as contraction of the heart, breathing, secretion of hormones, and the constant activity of the nervous system also are consuming energy. Basal metabolism, or the basal metabolic rate (BMR), represents the energy requirements of the many different cellular and tissue processes that are necessary to continuing physiological activities in a resting, postabsorptive state throughout most of the day. Other than sleeping, it is the lowest rate of energy expenditure. The determination of the BMR is a clinical procedure conducted in a laboratory or hospital set-

96

C H A P T E R 3 Human Energy

ting. The individual fasts for 12 hours. Then, with the subject in a reclining position, the individual’s oxygen consumption and carbon dioxide production are measured. Through proper calculations, the BMR is determined. Basal energy expenditure (BEE) represents the BMR extrapolated over a 24-hour period. The resting metabolic rate (RMR) is slightly higher than the BMR. It represents the BMR plus small amounts of additional energy expenditure associated with eating and previous muscular activity. According to the National Research Council, the BMR and RMR differ by less than 10 percent. Consequently, although there are some fine differences in the two terms, they are often used interchangeably. Additionally, the National Research Council uses the term resting energy expenditure (REE) to account for the energy processes at rest when extrapolated over 24 hours. In general, we shall use REE to also represent RMR. Although some of the energy released during oxidative processes at rest supports physiological functions, such as pumping activity of the heart muscle, the majority of energy is released as heat, a thermal effect that keeps our body temperature at about 98.6° Fahrenheit (37° Celsius). Eating a meal and exercise are two other factors that induce a thermal effect.

What effect does eating a meal have on the metabolic rate? The significant elevation of the metabolic rate that occurs after ingestion of a meal was previously known as the specific dynamic action of food but is now often referred to as dietary-induced thermogenesis (DIT) or thermic effect of food (TEF). This elevation is usually highest about 1 hour after a meal and lasts for about 4 hours, and it is due to the energy necessary to absorb, transport, store, and metabolize the food consumed. The greater the caloric content of the meal, the greater this TEF effect. Also, the type of food ingested may affect the magnitude of the TEF. The TEF for protein approximates 20–30 percent, carbohydrate approximates 5–10 percent, while the effect of fat is minimal (0–5 percent). Crovetti and others noted that a very high protein meal (68% of Calories) elicited a greater TEF for seven hours post-eating than did corresponding diets high in carbohydrate and fat. However, the increased TEF averaged only about six Calories more per hour, not an appreciable amount. Alcohol intake also causes about a 15 percent rise in the REE. The TEF is expressed as a percent of the energy content of the ingested meal. The normal increase in the BMR due to TEF from a mixed meal of carbohydrate, fat, and protein is about 5–10 percent. A TEF of 10 percent will account for 50 Calories of a 500 Calorie meal. The remaining 450 Calories are available for energy use by other body processes. The TEF effect accounts for approximately 5–10 percent of the total daily energy expenditure. de Jonge and Bray, in a review of 49 studies, reported that obesity is associated with a decreased TEF, suggesting that the obese are more efficient in storing fat. The composition of some diets for weight-loss purposes has been based upon this TEF effect; this topic is discussed in chapters 10 and 11 concerning diets for weight control.

How can I estimate my daily resting energy expenditure (REE)? There are several ways to estimate your REE, but whichever method is used, the value obtained is an estimate and will have some error associated with it. To get a truly accurate value you would need a clinical evaluation, such as a standard BMR test. Accurate determination of REE is important for clinicians dealing with obesity patients, for such testing is needed to rule out hypometabolism. However, a number of formula estimates may give you an approximation of your daily REE. Table 3.4 provides a simple method for calculating the REE of males and females of varying ages. Examples are provided in the table along with calculation of a 10-percent variability. Keep in

TABLE 3.4

Estimation of the daily resting energy expenditure (REE)

Age (years)

Equation

Males 3–9 10–17 18–29 30–60 > 60

(22.7 × body weight*) + 495 (17.5 × body weight) + 651 (15.3 × body weight) + 679 (11.6 × body weight) + 879 (13.5 × body weight) + 487

Example 154-lb male, age 20 154 lbs/2.2 = 70 kg (15.3 × 70) + 679 = 1,750

What genetic factors affect my REE? Your REE is directly related to the amount of metabolically active tissue that you possess. At rest, tissues such as the heart, liver, kidneys, and other internal organs are more metabolically active than muscle tissue, but muscle tissue is more metabolically active than fat. Changes in the proportion of these tissues in your body will therefore cause changes in your REE. Many factors influencing the REE, such as age, sex, natural hormonal activity, body size and surface area, and to a degree, body composition, are genetically determined. The effect of some of these factors on the REE is generally well known. Because infants have a large proportion of metabolically active tissue and are growing rapidly, their REE is extremely high. The REE declines through childhood, adolescence, and adulthood as full growth and maturation are achieved. Individuals with naturally greater muscle mass in comparison to body fat have a higher REE; the REE of women is about 10–15 percent lower than that of men, mainly because women have a higher proportion of fat to muscle tissue. Genetically lean individuals have a higher REE than do stocky individuals because their body surface area ratio is larger in proportion to their weight (body volume) and they lose more body heat through radiation.

How does body composition affect my REE?

Females 3–9 10–17 18–29 30–60 >60

mind that this is only an estimate of the daily REE, and additional energy would be expended during the day through the TEF effect and the effect of physical activity, as noted later. A very simple, rough estimate of your REE is one Calorie per kilogram body weight per hour. Using this procedure, the estimated value for the male in table 3.4 is 1,680 Calories per day (1 × 70 kg × 24 hours) and for the female is 1,320 Calories (1 × 55 kg × 24 hours), values which are not substantially different from those calculated by the table procedure.

(22.5 × body weight*) + 499 (12.2 × body weight) + 746 (14.7 × body weight) + 496 ( 8.7 × body weight) + 829 (10.5 × body weight) + 596

Example 121-lb female, age 20 121 lbs/2.2 = 55 kg (14.7 × 55) + 496 = 1,304 To get a range of values, simply add or subtract a normal 10-percent variation to the RMR estimate. Male example: 10 percent of 1,750 = 175 Calories Normal range = 1,575–1,925 Calories/day Female example: 10 percent of 1,304 = 130 Calories Normal range = 1,174–1,434 Calories/day *Body weight is expressed in kilograms (kg).

Body composition may be changed so as to alter REE. Losing body weight, including both body fat and muscle tissue, generally lowers the total daily REE. The REE may be decreased significantly in obese individuals who go on a very low-Calorie diet of less than 800 Calories per day. The decrease in the REE, which is greater than would be due to weight loss alone, may be caused by lowered levels of thyroid hormones. In one study, the REE of obese subjects dropped 9.4 percent on a diet containing only 472 Calories per day. This topic is covered in more detail in chapters 10 and 11. The possibility of decreased REE in some athletes who maintain low body weight through exercise, such as female distance runners and male wrestlers, has been the subject of recent debate and will be covered in chapter 10 when we discuss body composition. On the other hand, maintaining normal body weight while reducing body fat and increasing muscle mass may raise the REE slightly because muscle tissue has a somewhat higher metabolic level than fat tissue or because the ratio of body surface area to

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body weight is increased. The decline in the REE that occurs with aging may be attributed partially to physical inactivity with a consequent loss of the more metabolically active muscle tissue and an accumulation of body fat. Methods to lose body fat and increase muscle mass are covered in chapters 11 and 12.

Ke y C o n c e p t s 䉴 Human metabolism represents the sum total of all physiological



What environmental factors may also influence the REE? Several lifestyle and environmental factors may influence our metabolism. For example, although caffeine is not a food, it is a common ingredient in some of the foods we may eat or drink. Caffeine is a stimulant and may elicit a significant rise in the REE. One study reported that the caffeine in 2–3 cups of regular coffee increased the REE 10–12 percent. Smoking cigarettes also raises the REE. Apparently the nicotine in tobacco stimulates the metabolism similarly to caffeine. This may be one of the reasons why some individuals gain weight when they stop smoking. Climatic conditions, especially temperature changes, may also raise the REE. Exposure to the cold may stimulate the secretion of several hormones and muscular shivering, which may stimulate heat production up to 400 percent. Exposure to warm or hot environments will increase energy expenditure through greater cardiovascular demands and the sweating response. Altitude exposure will also increase REE due to increased ventilation. Many of these factors influencing the REE are important in themselves but may also be important considerations relative to weight control programs and body temperature regulation. Thus, they are discussed further in later chapters. The most important factor that can increase the metabolic rate in general is exercise. As we shall see in the next section, exercise also may exert some effects upon the REE.

What energy sources are used during rest? The vast majority of the energy consumed during a resting situation is used to drive the automatic physiological processes in the body. Because the muscles expend little energy during rest, there is no need to produce ATP rapidly. Hence, the oxygen system is able to provide the necessary ATP for resting physiological processes. The oxygen system can use carbohydrates, fats, and protein as energy sources. However, as noted in chapter 6, protein is not used as a major energy source under normal dietary conditions. Carbohydrates and fats, when combined with oxygen in the cells, are the major energy substrates during rest. Several factors may influence which of the two nutrients is predominantly used. In general, though, on a mixed diet of carbohydrate, protein, and fat, about 40 percent of the REE is derived from carbohydrate and about 60 percent comes from fat. However, eating a diet rich in carbohydrate or fat will increase the percent of the REE derived, respectively, from carbohydrate and fat. Also, when carbohydrate levels are low, such as after an overnight fast, the percentage of the REE derived from fat increases. 98

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䉴 䉴

processes in the body, and the metabolic rate reflects the speed at which the body utilizes energy. The basal metabolic rate (BMR) represents the energy requirements necessary to maintain physiological processes in a resting, postabsorptive state, while the resting metabolic rate (RMR) is a little higher due to the effects of prior eating and physical activity.The terms BEE and REE represent basal energy expenditure and resting energy expenditure, respectively, totaled over a 24-hour period. Eating a meal increases the metabolic rate as the digestive system absorbs, metabolizes, and stores the energy nutrients, a process termed the thermic effect of food (TEF). A meal will increase the RMR by about 5–10 percent, and some meals will elevate the RMR more so than others. Various methods may be used to estimate daily resting energy expenditure (REE), but one simple means is to use the value of one (1) Calorie per kilogram body weight per hour. For a 60-kilogram (132-pound) individual, this would represent 1,440 Calories over the course of 24 hours (60 ⫻ 1.0 ⫻ 24). A number of different factors may affect the REE, including body composition, drugs, climatic conditions, and prior exercise. Fats stored in the body serve as the main source of energy during rest.

C h e c k f o r Yo u r s e l f Using the formula in table 3.4, estimate your daily resting energy expenditure (REE) in Calories. Keep this record for later comparisons.

Human Energy Metabolism during Exercise Exercise is a stressor to the body, and almost all body systems respond. If the exercise is continued daily, the body systems begin to adapt to the stress of exercise. As noted previously and as we shall see in later chapters, these adaptations may have significant health benefits. The two body systems most involved in exercise are the nervous system and the muscular system. The nervous system is needed to activate muscle contraction, but it is in the muscle cell itself that the energetics of exercise occur. Most other body systems are simply designed to serve the needs of the muscle cell during exercise.

How do my muscles influence the amount of energy I can produce during exercise? Muscles comprise a significant percentage of our body weight, approximating 45 percent in the typical adult male and 35 percent in the typical adult female. However, in any given individual these percentages may vary tremendously depending on level and type of

physical activity. We shall discuss the potential health and sports performance benefits associated with modifying muscle mass in later chapters, but our focus here is on energy production for exercise. The muscle cell, or muscle fiber, is a rather simple machine in design but extremely complex in function. It is a tube-like structure containing filaments that can slide by one another to shorten the total muscle. The shortening of the muscle moves bones, and hence work is accomplished, be it simply the raising of a barbell as in weight training or moving the whole body as in running. Like most other machines, the muscle cell has the capability of producing work at different rates, ranging from very low levels of energy expenditure during sleep to nearly a ninety-fold increase during maximal, short-term anaerobic exercise. The human body possesses several different types of muscle fibers, and their primary differences are in the ability to produce energy. Various types of proteins are found in muscle cells, and the production of energy is dependent on the specific type of proteins present. In general, three different types of muscle fiber types have been differentiated based on their rate of energy production, and table 3.5 presents various characteristics associated with each. Type I muscle fiber is also known as the slow twitch red fiber, and as this name implies is used for slow muscle contractions, such as during rest and light aerobic physical activity. It is often referred to as the slow-oxidative (SO) fiber. The characteristics associated with it, such as high mitochondria and myoglobin content, support its high oxidative capacity and resistance to fatigue. Use of the type I fiber is important during events associated with aerobic capacity and aerobic power. The type IIa muscle fiber, also known as the fast twitch red fiber, also possesses good aerobic capacity, but not as high as the type I fiber. However, it may also produce energy anaerobically via the lactic acid energy system. Hence, it is often referred to as the fast-oxidative glycolytic (FOG) fiber. It also has high ATP-PCr capacity. Use of the type IIa fiber is important during events associated with aerobic power and anaerobic capacity, but it fatigues sooner than the type I muscle fiber.

TABLE 3.5

The type IIb muscle fiber, also known as the fast twitch white fiber, possesses poor aerobic capacity and is used primarily for anaerobic energy production. It is often referred to as the fast glycolytic (FG) fiber. Like the type IIa fiber, it also has high ATP-PCr capacity. Use of the type IIb muscle fiber is important during events associated with anaerobic power and anaerobic capacity, but it fatigues very rapidly Most muscles contain all three types of muscle fibers, and all fibers are used during exercise tasks of varying intensity. However, the use of one fiber type will usually predominate, dependent on the intensity of the exercise task and the associated human energy system. Physical training can improve the efficacy of each muscle fiber type, and the benefits that accrue to each depend on the type and extent of exercise training. Moreover, the distribution of muscle fiber types will vary among different individuals due to genetic predisposition, and such differences may influence the level of success in certain sport endeavors.

What effect does muscular exercise have on the metabolic rate? As noted in the previous section, the REE is measured with the subject at rest in a reclining position. Any physical activity will raise metabolic activity above the REE and thus increase energy expenditure. Accounting for changes in physical activity over the day may provide a reasonable, although imprecise, estimate of the total daily energy expenditure. Very light activities such as sitting, standing, playing cards, cooking, and typing all increase energy output above the REE, but we normally do not think of them as exercise as noted later in this chapter. For purposes of this discussion, the exercise metabolic rate (EMR), represents the increase in metabolism brought about by moderate or strenuous physical activity such as brisk walking, climbing stairs, cycling, dancing, running, and other such planned exercise activities. The EMR is known more appropriately as the thermic effect of exercise (TEE). The most important factor affecting the metabolic rate is the intensity or speed of the exercise. To move faster, your muscles

Characteristics associated with the three types of muscle fibers

Type

I

IIa

IIb (IIx)

Twitch speed Color Size (diameter) Fatigability Force production Oxidative processes Mitochondria Myoglobin Blood flow Triglyceride use Glycogen use Phosphocreatine levels Phosphocreatine levels Energy for sports

Slow Red Small Slow Low Highest Highest Highest Highest Highest Lowest Lowest Lowest Aerobic capacity; aerobic power

Faster Red Medium Moderate High Moderate Moderate Moderate Moderate Moderate Moderate Higher Higher Aerobic power; anaerobic capacity

Fastest White Large Fast Highest Lowest Low Low Lowest Lowest Highest Higher Higher Anaerobic power; anaerobic capacity

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must contract more rapidly, consuming proportionately more energy. Use of type I muscle fibers predominates during lowintensity exercise, and type II fibers are increasingly recruited with more intense exercise. The following represents approximate energy expenditure in Calories per minute for increasing levels of exercise intensity for an average-sized adult male. However, for most of us it would be impossible to sustain the higher levels of energy expenditure for a minute, and the highest level could be sustained for only a second or so. Level of intensity Resting metabolic rate Sitting and writing Walking at 2 mph Walking at 3 mph Running at 5 mph Running at 10 mph Running at 15 mph Running at 20 mph Maximal power weightlift

Caloric expenditure per minute 1.0 2.0 3.3 4.2 9.4 18.8 29.3 38.7 >90.0

Although the intensity of the exercise is the most important factor affecting the magnitude of the metabolic rate, there are some other important considerations. In some activities the increase in energy expenditure is not directly proportional to speed, for the efficiency of movement will affect caloric expenditure. Very fast walking becomes more inefficient, so the individual burns more Calories per mile walking briskly compared to more leisurely walking. A beginning swimmer wastes a lot of energy, whereas one who is more accomplished may swim with less effort, saving Calories when swimming a given distance. Swimming and cycling at very high speeds exponentially increase water or air resistance, so caloric expenditure also increases exponentially. Moreover, the individual with a greater body weight will burn more Calories for any given amount of work in which the body has to be moved, as in walking, jogging, or running. It simply costs more total energy to move a heavier load.

How is exercise intensity measured? The intensity of a given exercise may be measured in two general ways. One way is to measure the actual work output or power of the activity, such as foot-pounds per second, kilojoules per second, or watts. In some cases this is rather easy to do because some machines, such as bicycle ergometers, are designed to provide an accurate measure of work output. However, the actual work output of a basketball player during a game is more difficult to measure, although use of accelerometers and other motion-detection devices help. Data, such as watt production, derived from these techniques may be used to infer the predominant energy system being used. However, as noted previously, measurement accuracy with such devices, particularly for research purposes, is a concern. A second way is to measure the physiological cost of the activity by monitoring the activity of the three human energy systems. WardSmith noted that due to accurate measurements of oxygen uptake and carbon dioxide output, the energy contributions from aerobic metabolism are readily quantifiable, while the energy contribution from anaerobic metabolism is far more difficult to determine. 100

C H A P T E R 3 Human Energy

Energy production from the ATP-PCr energy system has been measured by several procedures. One procedure involves a muscle biopsy with subsequent analysis for ATP and PCr levels to determine use following exercise, but the small muscle biopsy may not represent ATP-PCr use in other muscles. ATP and PCr levels may also be determined by computerized imaging procedures, a noninvasive procedure, but the exercise task needs to be confined to specific movements due to the nature of the imaging equipment. Thus, Lange and Bury indicate that it is difficult to obtain precise physiological or biochemical data during common explosive-type exercise tests, such as short sprints. Laboratory techniques are also available to measure the role of the lactic acid system in exercise, primarily by measuring the concentration of lactic acid in the blood or in muscle tissues. One measure of exercise intensity is the so-called anaerobic threshold, or that point where the metabolism is believed to shift to a greater use of the lactic acid system. This point is often termed the onset of blood lactic acid (OBLA), or lactate threshold. The anaerobic threshold may also be referred to as the steady-state threshold, indicating that endurance exercise may continue for prolonged periods if you exercise below this threshold value. Exercise physiologists disagree about which is the better term, but all terms may be found in scientific literature. Some sport scientists also use specific measurements to define these terms, such as a certain level of blood lactic acid. Laboratory tests also are necessary to measure the contribution of the oxygen system during exercise, and this is the most commonly used technique for measuring exercise intensity (see figure 3.3). The most commonly used measurement is the maximal oxygen uptake, which represents the highest amount of oxygen that an individual may consume under exercise situations. In essence, the technique consists of monitoring the oxygen uptake of the individual while the exercise intensity is increased in stages. When oxygen uptake does not increase with an increase in workload, the maximal oxygen uptake has been reached. Maximal oxygen uptake is usually expressed as VO2 max, which may be stated as liters per minute or milliliters per kilogram body weight per minute. An example is provided in figure 3.13. A commonly used technique to indicate exercise intensity is to report it as a certain percentage of an individual’s VO2 max, such as 50 or 75 percent. If blood samples are taken periodically to measure serum levels of lactic acid, the percent of VO2 max at which the steady-state threshold occurs may be determined. Additionally, measurement of oxygen during recovery from exercise may be used to calculate the maximal accumulated oxygen deficit (MAOD), an indirect marker for anaerobic contributions to energy expenditure during exercise. Proper training may increase both VO2 max and the steady-state threshold, as illustrated in figure 3.14. In summary, measurement of the three energy systems during exercise provides us with a measure of the energy cost of the physical activity.

How is the energy expenditure of exercise metabolism expressed? A number of research studies have been conducted to determine the energy expenditure of a wide variety of sports and other physical activities.

The energy costs have been reported in a variety of ways, including Calories, kilojoules (kJ), oxygen uptake, and METS. The MET is a unit that represents multiples of the resting metabolic rate (see figure 3.15). These concepts are, of course, all interrelated, so an exercise can be expressed in any one of the four terms and converted into the others. For our purposes, we will express energy cost in Calories per minute based upon body weight, as that appears to be the most practical method for this book. However, just in case you see the other values in another book or magazine, here is how you may simplify the conversion. We know the following approximate values:

FIGURE 3.13

Maximal oxygen uptake (VO2 max).The best way to express VO2 max is in milliliters of oxygen per kilogram (kg) of body weight per minute (ml O2/kg/min). As noted in the figure, the smaller individual has a lower VO2 max in liters but a higher VO2 max when expressed relative to weight. In this case, the smaller individual has a higher degree of aerobic fitness, at least as measured by VO2 max per unit body weight.

1 C = 4 kJ 1 L O2 = 5 C 1 MET = 3.5 ml O2/kg body weight/min (amount of oxygen consumed during rest) These values are needed for the following calculations: Example: Exercise cost = 20 kJ/minute To get Calorie cost, divide kJ by the equivalent value for Calories. 20 kJ/min/4 = 5 C/min Example: Exercise cost = 3 L of O2/min To get Calorie cost, multiply liters of O2 × Calories per liter.

VO2 max: liters/minute

3.6 L (3600 ml)

4.0 L (4000 ml)

kg body weight

60

80

VO2 max: ml O2/kg/minute

60

50

Caloric cost = 3 × 5 = 15 C/min Example: Exercise cost = 25 ml O2/kg body weight/min You need body weight in kg, which is weight in pounds divided by 2.2. For this example 154 lbs = 70 kg. Determine total O2 cost/min by multiplying body weight times O2 cost/kg/min. 70 × 25 = 1,750 ml O2 Convert ml to L: 1,750 ml = 1.75 L Multiply liters O2 × Calories per liter

VO2 max (ml O2/kg/minute)

m 50

Caloric cost = 1.75 × 5 = 8.75 C/min Example: Exercise cost = 12 METS You need body weight in kg—for this example, 70 kg. Multiply total METS times O2 equivalent of 1 MET.

40 O Steady e state r

30

12 × 3.5 ml O2/kg/min = 42.0 ml O2/kg/min

20

Multiply body weight times this result O

70 × 42 ml O2/kg/min = 2,940 ml O2/min

10

Convert ml to L: 2,940 ml O2/min = 2.94 L O2/min 0

1

2

3

4

5

6

Training (months)

The effect of training upon VO2 max and the steady-state threshold.Training increases both your VO2 max and your steady-state threshold, which is the ability to work at a greater percentage of your VO2 max without producing excessive lactic acid—a causative factor in fatigue. For example, before training the VO2 max may be 40 ml while the steady-state threshold is only 20 ml (50% of VO2 max). After training,VO2 max may rise to 50 ml, but the steady-state threshold may rise to 40 ml (80% of the VO2 max).

Multiply liters O2 × Calories per liter Caloric cost = 2.94 × 5 = 14.70 C/min

FIGURE 3.14

How can I tell what my metabolic rate is during exercise? The human body is basically a muscle machine designed for movement. Almost all of the other body systems serve the muscular system. The nervous system causes the muscles to contract. www.mhhe.com/williams9

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Rest

Slow walk (2 mph)

Fast walk (5 mph)

Run (8 mph)

Liters of oxygen/minute

.25

.5–.75

1.5–1.75

2.5–3.0

Calories/minute

1.25

2.5–3.75

7.5–8.75

12.5–15.0

Kilojoules/minute

5

10–15

30–35

50–60

METS

1

2–3

6–7

10–12

F I G U R E 3 . 1 5 Energy equivalents in oxygen consumption, Calories, Kilojoules, and METS.This figure depicts four means of expressing energy expenditure during four levels of activity.These approximate values are for an average male of 154 pounds (70 kg). If you weigh more or less, the values will increase or decrease accordingly.

The digestive system supplies nutrients. The cardiovascular system delivers these nutrients along with oxygen in cooperation with the respiratory system. The endocrine system secretes hormones that affect muscle nutrition. The excretory system removes waste products. When humans exercise, almost all body systems increase their activity to accommodate the increased energy demands of the muscle cell. In most types of sustained exercises, however, the major demand of the muscle cells is for oxygen. As noted previously, the major technique for evaluating metabolic rate is to measure the oxygen consumption of an individual during exercise. Athletes may benefit from such physiological testing. Measurements of VO2 max, maximal heart rate, and the anaerobic threshold may help in planning an optimal training program, and subsequent testing may illustrate training effects. Such testing is becoming increasingly available at various universities and comprehensive fitness/wellness centers. 102

C H A P T E R 3 Human Energy

Unfortunately, this may not be practical for most of us. However, because of some interesting relationships among exercise intensity, oxygen consumption, and heart rate, the average individual may be able to get a relative approximation of the metabolic rate during exercise. A more or less linear relationship exists between exercise intensity and oxygen uptake. As the intensity level of work increases, so does the amount of oxygen consumed. The two systems primarily responsible for delivering the oxygen to the muscles are the cardiovascular and respiratory systems. There is also a fairly linear relationship between their responses and oxygen consumption. In general, maximal heart rate (HRmax) and VO2 max coincide at the same exercise intensity level. A simplified schematic is presented in figure 3.16. Because the heart rate (HR) generally is linearly related to oxygen consumption (the main expression of metabolic rate), and because it is easy to measure this physiological response during exercise either at the wrist or neck pulse, it may prove to be a practical guide to your metabolic rate. The higher your heart rate, the greater your metabolic rate. However, a number of factors may influence your specific heart rate response to exercise, such as the type of exercise (running vs. swimming), your level of physical fitness, sex, age, skill efficiency, percentage of body fat, and a number of environmental conditions.

4. Not all body weights could be listed, but you may approximate by going to the closest weight listed. 5. There may be small differences between men and women, but not enough to make a marked difference in the total caloric value for most exercises.

High

Magnitude of response

As one example, suppose we calculate the energy expenditure of a 154-pound individual who ran 5 miles in 30 minutes. You must calculate either the minutes per mile or miles per hour (mph). 1. 30 minutes / 5 miles = 6 min/mile 2. 60 minutes / 6 minutes/mile = 10 mph

Low Maximal xercise intensity

F I G U R E 3 . 1 6 Relationships between oxygen consumption, heart rate, and respiration responses to increasing exercise rates. In general, as the intensity of exercise continues, there is a rise in oxygen consumption, which is accompanied by proportional increases in heart rate and respiration.VO2 max and HRmax usually occur at the same exercise intensity.

Thus, it is difficult to predict your exact metabolic rate from your exercise HR. As we shall see in chapter 11, however, the HR data during exercise may be used as a basis for establishing a personal fitness program for health and weight control, either directly by measuring the heart rate or indirectly by how intense we perceive the exercise to be, or our rating of perceived exertion.

How can I determine the energy cost of exercise? To facilitate the determination of the energy cost of a wide variety of physical activities, appendix B has been developed. This is a composite table of a wide variety of individual reports in the literature. When using this appendix, keep the following points in mind. 1. The figures include the REE. Thus, the total cost of the exercise includes not only the energy expended by the exercise itself, but also the amount you would have used anyway during that same period. Suppose you ran for 1 hour and the calculated energy cost was 800 Calories. During that same time at rest you may have expended 75 Calories as your REE. The net cost of the exercise is only 725 Calories. 2. The figures in the table are only for the time you are doing the activity. For example, in an hour of basketball you may exercise strenuously for only 35–40 minutes, as you may take timeouts and rest during foul shots. In general, record only the amount of time that you are actually moving during the activity. 3. The figures may give you some guidelines to total energy expenditure, but actual caloric cost might vary somewhat because of such factors as your skill level, running against the wind or uphill, and so forth.

Consult appendix B and find the caloric value per minute for a body weight of 155 lbs and a running speed of 10 mph, a value of 18.8 Calories/minute. Multiply this value times the number of minutes of running, and you get the total caloric cost of that exercise. In this example, 30 × 18.8 = 564 total Calories expended. If the activity you do does not appear in appendix B, try to find one you think closely matches the movements found in your activity. Then check the caloric expenditure for the related activity. http://prevention.sph.sc.edu/tools/compendium.htm Presents a complete compendium of the metabolic cost, in MET values, for hundreds of different activities of daily living, specific exercises, and sports.The compendium was developed by Barbara Ainsworth, from Arizona State University, and other health professionals.

What are the best types of activities to increase energy expenditure? Activities that use the large muscle groups of the body and are performed continuously usually will expend the greatest amount of Calories. Intensity and duration are the two key determinants of total energy expenditure. Activities in which you may be able to exercise continuously at a fairly high intensity for a prolonged period will maximize your total caloric loss. Although this may encompass a wide variety of different physical activities, those that have become increasingly popular include walking, running, swimming, bicycling, and aerobic dance. A few general comments about these common modes of exercising would appear to be in order. Walking and Running Walking and running are popular exercises because they are so practical to do. All you need is a good pair of shoes. Walking Walking is more economical than running. Kuo and others note that walking is a pendular motion, with the stance leg behaving like an inverted pendulum and the swing leg like a regular pendulum. Thus, walking appears to be optimized with respect to metabolic cost. A good rule of thumb is that you expend about 1 Calorie per kilogram/body weight per mile walking at a speed of 2–4 miles per hour, and the following represents the number of Calories expended walking a kilometer or mile for an average adult male and female. www.mhhe.com/williams9

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Walking

Kilometer Mile

Running

Male (165 lbs, 75 kg)

Female (132 lbs, 60 kg)

47 75

37 60

However, walking faster may increase energy expenditure exponentially. A study by Thomas and Londeree has shown that the caloric cost of walking at 4.7 mph is only about 5 percent less than jogging at the same speed. At high walking speeds (above 5 mph), you may possibly expend more energy than if you jogged at the same speed. Fast, vigorous walking, known as aerobic walking, can be an effective means to expend Calories. However, as with other exercise activities, it takes practice to become a fast walker. Walking intensity can be increased in other ways. Climbing stairs, at home, at work, in an athletic stadium, or on step machines, is one means to make walking more vigorous. Skipping is also more vigorous but may lead to injuries. Many individuals use small weights in conjunction with their walking or running programs either by carrying them or strapping them to the ankles or wrists. The most popular technique is to carry small weights of 1–3 pounds. A number of research studies have reported that this technique, particularly if the arms are swung vigorously through a wide range of motion during walking, may increase the energy expenditure about 5–10 percent or higher above unweighted walking at the same speed. Use of walking poles, similar to ski poles, may increase caloric expenditure by 15 percent. Increases in energy expenditure greater than 30 percent have been reported with vigorous pumping of 1-pound hand weights as compared with just running at the same speed. The heart rate response also increases, and using hand weights with fast walking is an adequate stimulus to promote a training effect on the cardiovascular system. However, use of hand weights exaggerates the blood pressure response, and thus should be used with caution by individuals with blood pressure problems. Since some researchers have noted that simply walking a little faster without weights will have the same effect on energy cost and heart rate response, this may be a good alternative. Nevertheless, at any given walking speed, hand weights will increase energy expenditure. Addition of weights to the ankle also will increase energy expenditure, but it may also change the normal walking style and may predispose one to injury. Running Running a given distance expends more energy than walking the same distance. As a general rule, the caloric cost of running a given distance does not depend on the speed. It will take you a longer time to cover the distance at a slower running speed, but the total caloric cost will be similar to that expended at a faster speed. A good rule of thumb is that you expend about 1 Calorie per kilogram/body weight per kilometer, which approximates about 0.73 Calorie per pound/body weight per mile. The following represents the number of Calories expended running a kilometer or mile for an average adult male and female. In general, research indicates that running expends approximately 30–40 percent more energy per mile or kilometer compared to walking the same distance.

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Kilometer Mile

Male (165 lbs, 75 kg)

Female (132 lbs, 60 kg)

75 120

60 96

Swimming Because of water resistance, swimming takes more energy to cover a given distance than does either walking or running. Although the amount of energy expended depends somewhat on the type of swimming stroke used and the ability of the swimmer, swimming a given distance takes about four times as much energy as running. For example, swimming a quarter-mile is the energy equivalent of running a mile. Water aerobics and water running (doing aerobics or running in waist-deep, chest-deep, or deep water) may be effective exercise regimens that help prevent injuries due to impact. Cycling Bicycling takes less energy to cover a given distance in comparison to running on a level surface. The energy cost of bicycling depends on a number of factors such as body weight, the type of bicycle, hills, and body position on the bike (assuming a streamlined position to reduce air resistance). Owing to rapidly increasing air resistance at higher speeds such as 20 mph, the energy cost of bicycling increases at a much faster rate at such speeds. A detailed method for calculating energy expenditure during bicycling is presented in the article by Hagberg and Pena. In general, cycling 1 mile is approximately the energy equivalent of running one-third the distance. Aerobic Dance Aerobic dance, as it is now known, has been a popular form of exercise for over 30 years. There is a variety of styles of aerobic dance varying in intensity and the degree of impact with the floor. Several studies have shown that highintensity, high-impact aerobic dancing approximates 10 Calories per minute in women, which is indicative of strenuous exercise. Unfortunately, other research has shown that high-impact dancing is more traumatic and may lead to a higher incidence of leg injuries. Thus, the low-impact, or soft-impact, technique in which one foot usually remains in contact with the floor was introduced. Several studies have also shown that if done at a high intensity, low-impact aerobic dance may also use approximately 9–10 Calories per minute and be less likely to induce injuries to the legs. The use of step benches may also increase exercise intensity. Home Aerobic Exercise Equipment Home exercise equipment may also provide a strenuous aerobic workout. Recent research suggests that for any given level of perceived effort, treadmill running burned the most Calories. Exercising on elliptical trainers, cross-country ski machines, rowing ergometers, and stairclimbing apparatus also expended significant amounts of Calories, more so than bicycling apparatus. Many modern pieces of exercise equipment are electronically equipped with small computers to calculate approximate energy cost as Calories per minute and total caloric cost of the exercise.

Resistance or Weight Training Resistance training, or weight training, may be an effective way to expend energy, but it is not as effective as aerobic types of exercise. For example, Bloomer compared energy expenditure during resistance training (free-weight squatting at 70% maximal) to aerobic training (cycling at 70 percent VO2 max) for 30 minutes. Although the heart rates were the same for both types of exercise, the cycling protocol expended 441 Calories while the squatting protocol expended only 269 Calories, a 64 percent difference. Although this is a significant difference, Bloomer noted that the resistance exercise, if performed 4–5 days a week, would meet the recommendations for energy expenditure as suggested by the ACSM. www.MyPyramid.gov Go to MyTracker to calculate energy cost of your daily physical activities. www.internetfitness.com Click on Calorie Burning Calculator for the energy cost of various physical activities.

Table 3.6 provides a classification of some common physical activities based upon rate of energy expenditure. The implications of these types of exercises in weight control programs are discussed in later chapters.

Does exercise affect my resting energy expenditure (REE)? Exercise not only raises the metabolic rate during exercise but, depending upon the intensity and duration of the activity, will also keep the REE elevated during the recovery period. The increase in body temperature and in the amounts

TABLE 3.6

of circulating hormones such as adrenaline (epinephrine) will continue to influence some cellular activity, and some other metabolic processes, such as circulation and respiration, will remain elevated for a limited time. This effect, which has been labeled the metabolic aftereffects of exercise, is calculated by monitoring the oxygen consumption for several hours during the recovery period after the exercise task. The amount of oxygen in excess of the preexercise REE, often called excess postexercise oxygen consumption (EPOC), reflects the additional caloric cost of the exercise above and beyond that expended during the exercise task itself. Some older research noted that the average number of additional Calories expended after each exercise session would be about 45–50. However, in a series of more recent studies with more appropriate controls, although most investigators did report an increased REE following exercise of varying durations and intensities, the magnitude of the response was generally lower. Depending on the intensity and duration of the exercise bout in these studies, the REE during the recovery period ranged from 4–16 percent higher than the preexercise REE, and it remained elevated for only 15–20 minutes in some studies but up to 4–5 hours in others. Both aerobic and resistance-type exercises increase EPOC, with greater increases associated with high-intensity, long duration exercise. Burleson and others reported that when matched for oxygen consumption during exercise, weight training exhibited a greater postexercise oxygen consumption, but the amount was rather small. Using the oxygen consumption values presented in these studies, the additional energy expenditure ranged from 3–30 Calories. For example, Haddock and Wilkin

Classification of physical activities based upon rate of energy expenditure*

Light, mild aerobic exercise (< 5 Calories/min) Archery Badminton, social Baseball Bicycling (5 mph)

Bowling Dancing, waltz Golf (Cart)

Horseback riding (walk) Swimming (20–25 yards/min) Walking (2–3 mph)

Golf (carrying clubs) Rope skipping (60 rpm) Running (5 mph) Skiing, cross-country (2.5 mph)

Swimming (30–40 yards/min) Tennis, recreational Walking (3–4.5 mph) Weight training

Moderate aerobic exercise (5–10 Calories/min) Badminton, competitive Basketball, recreational Bicycling (10 mph) Dancing, aerobic

Moderately heavy to heavy aerobic exercise (> 10 Calories/min) Bicycling (15–20 mph) Calisthenics, vigorous In-line skating (10–15 mph)

Rope skipping (120–140 rpm) Running (6–9 mph) Skiing, cross-country (5–6 mph)

Swimming (50–70 yards/min) Tennis, competitive Walking (5.0–6.0 mph)

*Calories per minute based upon a body weight of 70 kg, or 154 pounds.Those weighing more or less will expend more or fewer Calories, respectively, but the intensity level of the exercise will be the same.The actual amount of Calories expended may also depend on a number of other factors, depending on the activity. For example, bicycling into or with the wind will increase or decrease, respectively, the energy cost. See appendix B for more details. Source: Modified from M.H.Williams, Nutritional Aspects of Human Physical and Athletic Performance, 1985, Charles C Thomas Publishers, Springfield, IL.

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found that although a bout of resistance training increased the resting metabolic rate for 120 minutes afterwards, subjects expended only about 23 more Calories above the normal resting level for that time frame. Although the metabolic aftereffects of exercise would not appear to make a significant contribution to weight loss, exercise may help mitigate the decrease in the REE often seen in individuals on very low-Calorie diets. This point is explored further in chapter 11.

Many studies have been conducted to investigate the effect of exercise on the thermic effect of food (TEF). Unfortunately, no clear answer has been found. Some studies have reported an increase in TEF when subjects exercise either before or after the meal, while others revealed little or no effects. Some research even suggests that exercise training decreases the TEF. Other studies have investigated differences between exercise-trained and untrained individuals relative to TEF, and although some preliminary research noted a decreased TEF in endurance-trained athletes, Tremblay and others also noted that it is still unclear if training causes any significant alterations in TEF. In any case, the increases or decreases noted in the TEF due to either exercise or exercise training were minor, averaging about 5–9 Calories for several hours.

1,800

TEE

1,600 TEF 1,400 Total daily energy expenditure (Calories)

Does exercise affect the thermic effect of food (TEF)?

2,000

1,200

1,000

800 BEE 600

400

How much energy do I need to consume daily? The National Academy of Sciences, through the Institute of Medicine, recently released its DRI for energy in conjunction with DRI for carbohydrate, fat, and protein, as noted in chapter 2. Because of possible problems in developing obesity, no RDA or UL were developed for energy. Instead, the Institute of Medicine uses the term Estimated Energy Requirement (EER), which it defines as the dietary intake that is predicted to maintain energy balance in a healthy adult of a defined age, gender, weight, height, and level of physical activity consistent with good health. In essence, the EER estimates your REE based on age, gender, weight, and height, and then modifies this value depending on your daily level of physical activity, which we refer to in this book as TEE. Your total daily energy expenditure (TDEE) is the sum of your BEE, your TEF, and your TEE. Figure 3.17 provides some approximate values for the typical active individual, indicating that BEE accounts for 60–75 percent of the total daily energy expenditure, TEF represents 5–10 percent, and TEE explains 15–30 percent. These values are approximate and may vary tremendously, particularly TEE, which may range from near 0 percent in the totally sedentary individual to 50 percent or more in ultraendurance athletes. In order to illustrate the effect that physical activity, or TEE, may have on your TDEE, the Institute of Medicine developed four physical activity level (PAL) categories, which are presented in table 3.7. The PAL describes the ratio of the TDEE divided by the BEE over a 24-hour period. The PAL in figure 3.17 is 1.43, or low active. The higher the ratio, the greater the amount of daily physical activity. 106

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200

0

F I G U R E 3 . 1 7 Total daily energy expenditure.Three major factors account for the total daily energy expenditure. Basal energy expenditure (BEE) accounts for 60–75 percent, the thermic effect of food (TEF) accounts for 5–10 percent, and 15–30 percent is accounted for by the thermic effect of exercise (TEE). However, all of these percentages are variable in different individuals, with exercise being the most modifiable component. In the figure, the BEE is 70 percent, the TEF is 10 percent, and the TEE is 20 percent.

The energy expenditure in individuals in the Sedentary category represents their REE, including the TEF, plus various physical activities associated with independent living, such as walking from the house or work to the car, typing, and other forms of very light activity. Levine has coined the term nonexercise activity thermogenesis (NEAT) for these very light activities, which represent all the energy we expend daily that is not sleeping, eating, or sports-related exercise. NEAT includes such activities as playing the piano, dancing, housework, washing the car, and similar daily physical activities. We shall discuss the role of NEAT in weight control in chapter 10.

TABLE 3.7

Males, 19 years and older:

The Physical Activity Level Categories

EER = 662 – 9.53 × age + [PA × (15.91 × Weight + 539.6 × Height)]

Category

Physical Activity Level (PAL)

Physical Activity Coefficient (PA) Males/Females

Sedentary

≥ 1.0 – < 1.4

1.00/1.00

Age: In years.

Low Active

≥ 1.4 – < 1.6

1.11/1.12

Active

≥1.6 – < 1.9

1.25/1.27

Weight: In kilograms (kg). To convert weight in pounds to kilograms, multiply by 0.454.

Very Active

≥1.9 – < 2.5

1.48/1.45

Females, 19 years and older: EER = 354 – 6.91 × age + [PA × (9.361 × Weight + 726 × Height)]

Height: In meters (m). To convert height in inches to meters, multiply by 0.0254.

For the other categories, the Institute of Medicine bases the PAL on the amount of daily physical activity that is the equivalent of walking at a rate of 3–4 miles per hour. For example, an adult male who weighs 154 pounds (70 kg) and who, in addition to the normal daily activities of independent living, expended the physical activity equivalent of walking 2.2 miles per day would be in the Low Active category, with a PAL of 1.5. To be in the Active category with a PAL of 1.75, he would need to expend the physical activity energy equivalent of walking 7.0 miles per day, and to be in the Very Active category with a PAL of 2.2, the energy equivalent of 17 miles per day. Keep in mind that you do not need to walk this many miles per day, but simply do a multitude of physical activities, such as climbing stairs, golfing, swimming, and jogging, that add up to this energy equivalent. Table 3.6 provides examples of physical activities ranging from light to heavy that may be used to total the required energy equivalents of walking. A more detailed table, based on body weight, is presented in appendix B. Based on a number of doubly labeled water studies, the Institute of Medicine developed equations for the Estimated Energy Requirement (EER). Here are two:

PA: PA is the physical activity coefficient, which is based on the PAL. Based on mathematical consideration to equate energy expenditure between the various PAL categories, the PA coefficient for the Sedentary category was set at 1.0 and the PA for the other categories adjusted accordingly. The PAs for the four PAL categories are presented for adult males and females in table 3.7. Although there may be variances in this estimate of your EER, the estimate may provide you with a ballpark figure of your daily energy needs. Let’s look at an example, as depicted in figure 3.18, of the difference that physical activity may have on the daily energy needs of a sedentary and very active adult female. Both are 20 years old, weigh 132 pounds (60 kg), and are 55 inches (1.4 m) tall. Sedentary: EER = 354 – 6.91 × 20 + [1.0 × (9.361 × 60 + 726 × 1.4)] EER = 354 – 138.2 + [1.0 × (561.66 + 1,016.4)] EER = 215.8 + [1,578.06] = 1,794 Calories

F I G U R E 3 . 1 8 Estimated Energy Requirement (EER) for two 20-year-old females. Both weigh 132 pounds (60 kg) and are 55 inches (1.4 m) tall.The sedentary female has a Physical Activity Coefficient (PA) of 1.0, whereas the very active female has a PA of 1.45. Compared to her sedentary counterpart, the very active female needs about 700 additional Calories to sustain her physically active lifestyle.

Sedentary lifestyle

Very Active lifestyle

PA = 1.0

PA = 1.45

EER = 1,794 Calories

EER = 2,504 Calories

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Very active: EER = 354 – 6.91 × 20 + [1.45 × (9.361 × 60 + 726 × 1.4)] EER = 354 – 138.2 + [1.45 × (561.66 + 1,016.4)] EER = 2,15.8 + [2,288.19] = 2,504 Calories The total caloric difference between the sedentary and very active women approximates 700 Calories per day, which may be important in several ways for the very active female. First, as noted in chapter 1, increased physical activity is an important aspect of a healthy lifestyle to prevent a variety of chronic diseases. Second, this additional 700 Calories of energy expenditure daily could have a significant impact on her body weight over time, approximating a loss of over a pound per week if not compensated for by increased food intake. Third, if she is at an optimal body weight, she may consume an additional 700 Calories per day without gaining weight. If you are interested in increasing your PAL, then your best bet is to incorporate more light, moderate, and moderately heavy to heavy physical activities into your daily lifestyle. Some additional guidelines for estimating your daily TDEE and EER, particularly in the design of a proper weight control program, are presented in chapter 11. www.nap.edu Full details concerning the EER and PAL are provided by the National Academies Press.Type in Dietary Reference Intake for Energy in the search box. Review chapters 5 and 12, which focus on energy and physical activity.

Ke y C o n c e p t s 䉴 The three major muscle fiber classifications are type I,type IIa,and











type IIb.Type I is also known as a slow-oxidative fiber,and produces ATP aerobically.Type IIa is also known as a fast-oxidative glycolytic fiber,and produces ATP both aerobically and anaerobically.Type IIb is also known as a fast glycolytic fiber,and produces ATP anaerobically. The thermic effect of exercise (TEE), or exercise metabolic rate (EMR) provides us with the most practical means to increase energy expenditure. The metabolic rate during exercise is directly proportional to the intensity of the exercise, and the exercise heart rate may serve as a general indicator of the metabolic rate. Activities that use the large muscle groups of the body, such as running, swimming, bicycling, and aerobic dance, facilitate energy expenditure. Resistance training of sufficient intensity and duration may also help expend enough energy to satisfy exercise recommendations for caloric expenditure. The total daily energy expenditure (TDEE) is accounted for by BEE (60–75 percent),TEF (5–10 percent), and TEE (15–30 percent), although these percentages may vary considerably among individuals. The Estimated Energy Requirement (EER) is defined as the dietary intake that is predicted to maintain energy balance in a healthy adult of a defined age, gender, height, weight, and level of physical activity consistent with good health. Changing from a sedentary Physical Activity Level (PAL) to a very active PAL is a very effective means to increase TDEE and EER.

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C h e c k f o r Yo u r s e l f Record the types and amounts (in minutes) of your daily physical activity (or use the record from Chapter 1) and consult appendix B to determine your total amount of daily energy expenditure through physical activity and exercise.The application exercise on page 113 may be useful.

Human Energy Systems and Fatigue during Exercise What energy systems are used during exercise? In sport, energy expenditure can vary tremendously. For example, Asker Jeukendrup and his associates recently noted that in one sport, World Class Cycling, events may range in duration from 10 seconds to 3 weeks, involving race distances between 200 meters to 4,000 kilometers. Exercise intensity in a 200-meter event would be extremely high, and much lower during the prolonged event. The most important factor determining which energy system will be used is the intensity of the exercise, which is the rate, speed, or tempo at which you pursue a given activity. In general, the faster you do something, the higher your rate of energy expenditure and the more rapidly you must produce ATP for muscular contraction. Very rapid muscular movements are characterized by high rates of power production. If you were asked to run 100 meters as fast as you could, you would exert maximal speed for a short time. On the other hand, if you were asked to run 5 miles, you certainly would not run at the same speed as you would for the 100 meters. In the 100-meter run your energy expenditure would be very rapid, characterized by a high-power production. The 5-mile run would be characterized by low-power production, or endurance. The requirement of energy for exercise is related to a powerendurance continuum. On the power end, we have extremely high rates of energy expenditure that a sprinter might use; on the endurance end, we see lower rates that might be characteristic of a marathon runner. The closer we are to the power end of the continuum, the more rapidly we must produce ATP. As we move toward the endurance end, our rate of ATP production does not need to be as great, but we need the capacity to produce ATP for a longer time. It should be noted from the outset that all three energy systems—ATP-PCr, lactic acid, and oxygen—are used in one way or another during most athletic activities. (Gastin provides an excellent overview.) However, one system may predominate, depending primarily upon the intensity level of the activity. In this regard, the three human energy systems may be ranked according to several characteristics, which are displayed in table 3.8. Both the ATP-PCr and the lactic acid systems are able to produce ATP rapidly and are used in events characterized by high intensity levels that occur for short periods, because their capacity for total ATP production is limited. Because both of these systems may function without oxygen, they are called anaerobic. Relative to running performance, the ATP-PCr system predominates in short, powerful bursts of muscular activity such as the short dashes like 100 meters,

TABLE 3.8

Major characteristics of the human energy systems*

Main energy source Intensity level Rate of ATP production Power production Capacity for total ATP production Endurance capacity Oxygen needed Anaerobic/aerobic Characteristic track event Time factor

ATP-PCr

Lactic acid

Oxygen

Oxygen

ATP; phosphocreatine Highest Highest Highest Lowest Lowest No Anaerobic 100-meter dash 1–10 seconds

Carbohydrate High High High Low Low No Anaerobic 200–800 meters 30–120 seconds

Carbohydrate Lower Lower Lower High High Yes Aerobic 5,000-meter (5 km) run 5 minutes or more

Fat Lowest Lowest Lowest Highest Highest Yes Aerobic Ultradistance Hours

*Keep in mind that during most exercises, all three energy systems will be operating to one degree or another. However, one system may predominate, depending primarily on the intensity of the activity. See text for further explanation.

whereas the lactic acid system begins to predominate during the longer sprints and middle distances such as 200, 400 and 800 meters. In any athletic event where maximal power production lasts about 1–10 seconds, the ATP-PCr system is the major energy source. The lactic acid system begins to predominate in events lasting 30–120 seconds, but studies have noted significant elevations in muscle lactic acid in maximal exercise even as brief as 10 seconds. The oxygen system possesses a lower rate of ATP production than the other two systems, but its capacity for total ATP production is much greater. Although the intensity level of exercise while using the oxygen system is by necessity lower, this does not necessarily mean that an individual cannot perform at a relatively high speed for a long time. The oxygen system can be improved through a physical conditioning program so that ATP production may be able to meet the demands of relatively high-intensity exercise, as discussed previously and highlighted in figure 3.14. Endurance-type activities, such as those that last 5 minutes or more, are dependent primarily upon the oxygen system, but the oxygen system makes a very significant contribution even in events as short as 30–90 seconds, as recently documented by Spencer and Gastin. In summary, we may simplify this discussion by categorizing the energy sources as either aerobic or anaerobic. Anaerobic sources include both the ATP-PCr and lactic acid systems while the oxygen system is aerobic. Table 3.9 illustrates the approximate percentage contribution of anaerobic and aerobic energy sources, dependent upon the level of maximal intensity that can be sustained for a given time period. Thus, for a 100-meter dash covered in 10 seconds, 85 percent of the energy is derived from anaerobic sources. For an elite marathoner (26.2 miles) with times of approximately 125–130 minutes in international-level competiTABLE 3.9 Time Anaerobic Aerobic

tion, the aerobic energy processes contribute 99 percent. Although Ward-Smith, using a mathematical approach to predict aerobic and anaerobic contributions during running, noted that these percentage values may be modified slightly for elite athletes, the concept is correct. For example, using track athletes as subjects, Spencer and Gastin found that the relative contribution of the aerobic energy system was 29 percent in the 200-meter run and increased progressively to 84 percent in the 1,500-meter run, noting that the contribution of the aerobic energy system during track running events is greater than traditionally thought. These values are somewhat higher than the aerobic percentage values presented in table 3.9, but support the concept. The key point is that the longer you exercise, the less your intensity has to be, and the more you rely on your oxygen system for energy production.

What energy sources are used during exercise? The ATP-PCr system can use only adenosine triphosphate and phosphocreatine, but as noted previously, these energy sources are in short supply and need to be replaced by the other two energy systems. The lactic acid system uses only carbohydrate, primarily the muscle glycogen stores. At high-intensity exercise levels that may be sustained for 1–2 minutes or less, such as exercising well above your VO2 max, carbohydrate will supply over 95 percent of the energy. However, the accumulation of lactic acid may be associated with the early onset of fatigue. On the other hand, the oxygen system can use a variety of different energy sources, including protein, although carbohydrate and fat are the primary ones. The carbohydrate is found as muscle glycogen, liver glycogen, and blood glucose. The fats are stored primarily as triglycerides in the muscle and adipose cells. As we

Percentage contribution of anaerobic and aerobic energy sources during different time periods of maximal work 10 sec

1 min

2 min

4 min

10 min

30 min

60 min

120 min

85 15

70 30

50 50

30 70

15 85

5 95

2 98

1 99

*Percentages are approximate and may vary between sedentary individuals and elite athletes.

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shall see in this section and in chapters 4, 5, and 6, a number of different factors can influence which energy source is used by the oxygen system during exercise, but exercise intensity and duration are the two most important factors. Under normal conditions, exercise intensity is the key factor determining whether carbohydrate or fat is used. Holloszy and others note that both absolute and relative (i.e., percent of VO2 max) exercise intensities play important roles in the regulation of substrate metabolism. The absolute work rate determines the total quantity of fuel required, while relative exercise intensity plays a major role in determining the proportions of carbohydrate and fat oxidized by the working muscles. Hoppeler and Weibel noted that as one does mild to moderate exercise, say up to 50 percent of one’s VO2 max, blood glucose and fat may provide much of the needed energy. However, the transfer of glucose and fat from the vascular system to the muscles becomes limited at about 50 percent of VO2 max. Thus, as you start to exceed 50 percent of your VO2 max, you begin to rely more on your intramuscular stores of glycogen and triglycerides. As you continue to increase your speed or intensity, you begin to rely more and more on carbohydrate as an energy source. Apparently the biochemical processes for fat metabolism are too slow to meet the increased need for faster production of ATP, and carbohydrate utilization increases. The major source of this carbohydrate is muscle glycogen. The transition from use of fat to carbohydrate as the primary fuel source during increasing intensity of exercise has been referred to as the crossover concept, and although the technicalities of specific fuel contributions are the subject of debate, exercise scientists agree that at some specific point in the increase of exercise intensity an individual will begin to derive more energy from carbohydrate than fat. At high levels of energy expenditure, 70–80 percent of VO2 max, carbohydrates may contribute more than 80 percent of the energy sources. Houston notes that elite marathoners burn about 19–20 Calories per minute, and need about 4–5 grams of carbohydrate per minute. This speaks for the need of adequate muscle glycogen stores when this level of exercise is to be sustained for long periods, say in events lasting over 60–90 minutes. In events of long duration, when body stores of carbohydrate are nearly depleted, the primary energy source is fat. In the later stages of ultramarathoning events, fat may become the only fuel available. However, protein may become an important energy source in these circumstances; its role is detailed in chapter 6. Other than exercise intensity and duration, a number of different factors are known to influence the availability and use of human energy sources during exercise. Gender, hormones, state of training, composition of the diet, time of eating prior to competition, nutritional status, nutrient intake during exercise, environmental temperature, and drugs are some of the more important considerations. For example, warm environmental temperatures may increase the use of carbohydrates, whereas fasting may facilitate the use of fats. These considerations will be incorporated in the following chapters where appropriate. For the interested reader, Hargreaves provides an excellent detailed review.

What is fatigue? Fatigue is a very complex phenomenon. It may be chronic, or it may be acute. Both types may affect the athlete. 110

C H A P T E R 3 Human Energy

Chronic Fatigue Chronic fatigue in the athlete may develop over time, usually in endurance athletes involved in prolonged, intense training that may involve conditions known as overreaching and overtraining. Overreaching is a condition of physical and mental stress that may impair physical performance, but may be a planned phase of training in elite athletes followed by short-term recovery with return to previous or improved levels of performance. Overtraining is a term often used to characterize a syndrome in athletes involving prolonged periods of fatigue. However, Halson and Jeukendrup note that although some scientific and anecdotal evidence support its existence, there appear to be no clear markers for overtraining and more research is needed to establish its existence with certainty. Some contend the term overtraining is misleading, and may actually be related to underrecovery, particularly involving inadequate nutrition. The chronic fatigue syndrome is a genuine medical condition characterized by numerous symptoms, the most prevalent being prolonged incapacitating fatigue. For those who exercise, fatigue is disproportionate to the effort. Roy Shephard, the renowned Canadian sport scientist, indicated that overtraining and/or a negative energy balance may be related to the development of the chronic fatigue syndrome. In such cases, training would be adversely affected and performance certainly would suffer. Given the debilitating effects on exercise and sports performance, scientists are attempting to identify the causes, prevention, and treatment of both overtraining and the chronic fatigue syndrome. Wyller indicates various factors may be associated with the chronic fatigue syndrome, including disturbances of the immune system, infections, endocrine disorders, mental stress, and personality traits. Treatment involves behavioral therapy and graded exercise, but recovery is a long process. Although the chronic fatigue syndrome is a serious medical condition, its prevalence in the general population, including athletes, appears to be very low. It is most prevalent in females, primarily in the 40–50 year age group. Acute Fatigue Acute mental or physical fatigue is experienced by most athletes at one time or another during maximal efforts.. For purposes of the present discussion, fatigue will be defined as the inability to continue exercising at a desired level of intensity. Relative to this definition, fatigue may be due to a failure of the rate of energy production in the human body to meet the demands of the exercise task. In simple terms, ATP production rates are unable to match ATP utilization rates. As acute fatigue can adversely affect sports performance, it has been the subject of considerable research. In general, sports scientists classify the site of acute fatigue in the body as either central or peripheral (see figure 3.19). Central fatigue involves the brain or spinal cord of the central nervous system (CNS), while peripheral fatigue is associated primarily with the muscles and, under some conditions, other body organs such as the heart or lungs.

What causes acute fatigue in athletes? Robert Fitts, an expert on muscular fatigue during prolonged exercise, recently noted that the etiology of fatigue is not fully understood despite more than a century of research. He indicated that the mechanisms of muscle fatigue are complex and depend on the

Central sites 1 Brain

FIGURE 3.19

Fatigue sites.The causes of fatigue are complex and may involve central sites such as the brain and spinal cord or peripheral sites in the muscles. Hypoglycemia, or low blood sugar, could adversely affect the functioning of the brain, while the acidity associated with the production of lactic acid could possibly interfere with optimal energy production in the muscle cells.

2 Spinal cord

Peripheral sites 3 Neuromuscular junction

ated with the depletion of critical neurochemicals or the accumulation of “toxic” concentrations of neurotransmitters at neural synapses, which could reduce neural impulses to the muscles. In this regard, Edgerton and Roy noted that elevated levels of serotonin, a neurotransmitter in the brain, are associated with fatigue, and exercise may increase levels of serotonin in the brain. On the other hand, the neurotransmitter norepinephrine is a stimulant and may help prevent fatigue; its reduction may help induce fatigue. Relative to central fatigue, Noakes highlights the fact that the single variable that is always maximal at exhaustion during all forms of exercise is the rating of perceived exertion, a mental perception. Peripheral and Central Fatigue Weir and others propose that fatigue involves both peripheral and central aspects. Depletion of substrate or accumulation of metabolites in the muscle may provide sensory feedback to the spinal cord or brain, which could then adjust the neural output back to the muscles. A decreased output from the central nervous system could decrease energy production and induce fatigue. Dempsey and others note that most scientists agree that the decision to reduce power output during exercise clearly involves the higher areas of the central nervous system, but the real mystery is to identify those sources of input that trigger these decisions. Some possible causes of fatigue are listed in table 3.10. Keep in mind that fatigue is complex and several of these factors may be involved simultaneously in the etiology of fatigue in certain TABLE 3.10

Some possible causes of fatigue during exercise

4 Muscle cells

Increased formation of depressant neurotransmitters

type of exercise, one’s state of fitness, and the fiber type composition of the muscle. Although the cause of acute exercise-induced fatigue has not been determined, numerous hypotheses exist, involving both peripheral and central fatigue. Peripheral Fatigue Hargreaves indicates that fatigue occurs when the compounds needed to produce ATP are depleted. For example, depletion of phosphocreatine would decrease the rate of ATP resynthesis. Hargreaves also notes that fatigue occurs when the by-products of metabolism accumulate in the muscle and interfere with optimal energy metabolism, specifically the actions of calcium which is essential for muscle contraction. For example, Fitts indicates that hydrogen ion accumulation can decrease sensitivity of the myofibrils to calcium. Some potential factors involve the following:

Increased serotonin levels Decreased levels of energy substrates Decrease in phosphocreatine levels Depletion of muscle glycogen Decrease in blood-sugar levels Decrease in plasma branched-chain amino acids Increased levels of reactive oxygen and nitrogen species Impaired calcium recycling Decreased muscle contraction force Disturbed acid-base balance Increase in hydrogen ions due to excess lactic acid production Decreased oxygen transport

Substrate Depletion

Metabolic By-Products Accumulation

ATP Phosphocreatine Muscle glycogen Blood glucose

Hydrogen ions ADP and inorganic phosphate Ammonia Reactive oxygen species

Decreased blood volume due to dehydration Increased core body temperature resulting in hyperthermia Decreased cooling effect due to dehydration Disturbed electrolyte balance

Central Fatigue Hargreaves notes that substrate depletion and accumulation of metabolic by-products may also induce central fatigue. For example, Noakes suggests central fatigue may be associ-

Increased or decreased concentration due to sweat losses and inadequate water replacement

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sport-type events. For example, Houston indicates that fatigue in the 400-meter dash may involve depletion of PCr and muscle glycogen, but may also be associated with increases in hydrogen ion concentration.

How can I delay the onset of fatigue? The most important factor in the prevention of premature fatigue is proper training, including physiological, psychological, and biomechanical training. Physiologically, athletes must train specifically on the energy system or systems that are inherent to their event. Under the guidance of sport physiologists and coaches, appropriate physiological training for each specific energy system may increase its energy stores, enzymatic activity, and metabolic efficiency, thus enhancing energy production. Physiological training enhances physical power. Psychologically, athletes must train the mind to tolerate the stresses associated with their specific event. Sport psychologists may help provide the athlete with various mental strategies, such as inducing either a state of relaxation or arousal, whichever may be appropriate for their sport. Physiological training may also confer some psychological advantages, such as tolerating higher levels of pain associated with intense exercise. Psychological training enhances mental strength. Biomechanically, athletes must maximize the mechanical skills associated with their sport. For any sport, sport biomechanists can analyze the athlete’s skill level and recommend modifications in movement patterns or equipment to improve energy production or efficiency. In many cases, modification of the amount of body fat and muscle mass may provide the athlete with

TABLE 3.11

a biomechanical advantage. Biomechanical training helps provide a mechanical edge. Proper physiological, psychological, and biomechanical training represents the best means to help deter premature fatigue. However, what you eat may affect physiological, psychological, and biomechanical aspects of sport performance. Thus, nutrition is an important consideration in delaying the onset of fatigue during sport training and competition.

How is nutrition related to fatigue processes? As noted in our discussion of the power-endurance continuum, we can exercise at different intensities but the duration of our exercise is inversely related to the intensity. We can exercise at a high intensity for a short time or at a low intensity for a long time. The importance of nutrition to fatigue is determined by this intensityduration interrelationship. In very mild aerobic activities, such as distance walking or lowspeed running in a trained ultramarathoner, the body can sustain energy production by using fat as the primary fuel when carbohydrate levels diminish. Because the body has large stores of fat, energy supply is not a problem. However, low blood-sugar levels, dehydration, and excessive loss of minerals may lead to the development of both mental and physical fatigue in very prolonged activities. In moderate to heavy aerobic exercise, the body needs to use more carbohydrate as an energy source and thus will run out of muscle glycogen faster. As we shall see later, carbohydrate is a more efficient fuel than fat, so the athlete will have to reduce the pace of the activity when liver and muscle carbohydrate stores are depleted, such as during endurance-type activities lasting over 90

Examples of some nutritional ergogenic aids and, theoretically, how they may influence physiological, psychological, or biomechanical processes to delay fatigue

Provide energy substrate

Attenuate fatigue-related metabolic by-products

Carbohydrate: Energy substrate for aerobic glycolysis Creatine: Substrate for formation of phosphocreatine (PCr)

Aspartate salts: Amino acids that mitigate ammonia production Sodium bicarbonate: Buffer to reduce effects of lactic acid

Enhance energy-generating metabolic pathways

Prevent catabolism of energy-generating cells

B vitamins: Coenzymes in aerobic and anaerobic glycolysis Carnitine: Enzyme substrate to facilitate fat metabolism

Antioxidants:Vitamins to prevent unwanted oxidation of cell membranes HMB: By-product of amino acid metabolism to prevent protein degradation

Increase cardiovascular-respiratory function

Ameliorate psychological function

Iron: Substrate for hemoglobin formation and oxygen transport Glycerol: Substance to increase blood volume

BCAA: Amino acids that favorably modify neurotransmitter production Choline: Substrate for formation of acetylcholine, a neurotransmitter

Increase size or number of energy-generating cells

Improve mechanical efficiency

Arginine and ornithine: Amino acids that stimulate production of human growth hormone, an anabolic hormone Chromium: Mineral to potentiate activity of insulin, an anabolic hormone

Ma huang: Stimulant to increase metabolism for fat loss Hydroxycitrate (HCA): Supplement to increase fat oxidation for fat loss

Note:These examples as to how nutritional aids may delay fatigue are based on theoretical considerations. As shall be shown in respective chapters, supplementation with most of these nutritional ergogenic aids has not been shown to enhance exercise or sport performance.

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minutes. Thus, energy supply may be critical. Low blood sugar, changes in blood constituents such as certain amino acids, and dehydration also may be important factors contributing to the development of mental or physical fatigue in this type of endeavor. In very high-intensity exercise lasting only 1 or 2 minutes, the probable cause of fatigue is the disruption of cellular metabolism caused by the accumulation of hydrogen ions resulting from excess lactic acid production. There is some evidence to suggest that sodium bicarbonate (discussed in chapter 13) may help reduce this disruptive effect of lactic acid to some extent. Furthermore, a very low supply of muscle glycogen in fast-twitch muscle fibers may impair this type of performance. In extremely intense exercise lasting only 5–10 seconds, a depletion of phosphocreatine (PCr) may be related to the inability to maintain a high force production. Although some nutritional practices, such as phosphate loading or gelatin supplements, have been used in attempts to increase PCr, they have not been regarded to be effective. However, recent research involving creatine supplements has shown some beneficial effects, which are discussed in chapter 6. In summary, a deficiency of almost every nutrient may be a causative factor in the development of fatigue. A poor diet can hasten the onset of fatigue. Proper nutrition is essential to assure the athlete that an adequate supply of nutrients is available in the diet not only to provide the necessary energy, such as through carbohydrate and fat, but also to ensure optimal metabolism of the energy substrate via protein, vitamins, minerals, and water. The role of specific nutrients or dietary supplements relative to fatigue

processes will be discussed in later sections of the book where appropriate. Table 3.11 provides some examples of how some nutrients or dietary supplements are thought to delay fatigue.

Ke y C o n c e p t s 䉴 The ATP-PCr and lactic acid energy systems are used primarily

during fast, anaerobic, power-type events, while the oxygen system is used primarily during aerobic, endurance-type events. 䉴 Fats serve as the primary source of fuel during mild levels of aerobic exercise intensity, but carbohydrates begin to be the preferred fuel as the exercise intensity increases. 䉴 Fatigue may be classified as central (neural) or peripheral (muscular) fatigue. Fatigue may also be caused by a variety of factors, including the depletion of energy substrate or the accumulation of fatigue-causing metabolites. 䉴 A sound training program and proper nutrition are important factors in the prevention of fatigue during exercise.

C h e c k f o r Yo u r s e l f Check the world records in running for 100 meters, 400 meters, 1,500 meters, and the marathon (42,200 meters). Calculate the average speed for each distance. Can you relate your findings to the human energy systems and their relationship to fatigue?

A P P L I C AT I O N Borrow, rent, or buy a pedometer or an accelerometer and keep a record of your daily movement (recording the amount every 2 hours). This will provide you with an estimate of your daily physical activity involving movement and will be useful in determining your estimated energy requirement (EER) and maintaining an optimal body weight as discussed in chapter 11.

Distance Distance logged logged Sunday Monday

Distance logged Tuesday

E X E R C I S E

Distance Distance Distance Distance logged logged logged logged Wednesday Thursday Friday Saturday

12:00–2:00 A.M. 2:00–4:00 A.M. 4:00–6:00 A.M. 6:00–8:00 A.M. 8:00–10:00 A.M. 10:00–12:00 A.M. 12:00–2:00 P.M. 2:00–4:00 P.M. 4:00–6:00 P.M. 6:00–8:00 P.M. 8:00–10:00 P.M. 10:00–12:00 P.M.

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Review Questions—Multiple Choice (b) The BMR is higher in women than in men due to the generally higher levels of body fat in women. (c) The resting metabolic rate is the equivalent of one MET. (d) The resting metabolic rate is higher than the BMR. (e) Dietary-induced thermogenesis raises the resting metabolic rate. 5. Which of the following is not likely to be a cause of fatigue? (a) depletion of PCr in fast-twitch fibers in a 200-meter dash (b) depletion of muscle glycogen in fasttwitch fibers in a 400-meter dash (c) depletion of adipose cell fatty acids in a marathon (d) depletion of muscle glycogen in a marathon (e) accumulation of hydrogen ions in a 400-meter dash 6. Of the following statements concerning the interrelationships between various forms of energy, which one is false? (a) A kilojoule is greater than a kilocalorie. (b) A kilogram-meter is equal to 7.23 foot-pounds. (c) A gram of fat has more Calories than a gram of carbohydrate. (d) A gram of fat has more Calories than a gram of protein. (e) A liter of oxygen can release more than one kilocalorie when metabolizing carbohydrate. 7. Approximately how many Calories will a 200-pound individual use while jogging a mile?

(a) 70 (d) 255 (b) 145 (e) 440 (c) 200 8. Which of the following statements relative to exercise and metabolic rate is false? (a) The intensity of the exercise is the most important factor to increase the metabolic rate. (b) Increased efficiency for swimming a set distance will decrease the energy cost. (c) The heavier person will burn more Calories running a mile than a lighter person. (d) Oxygen consumption and heart rate are two ways to monitor the metabolic rate. (e) Walking a mile slowly or jogging a mile cost the same amount of Calories. 9. Which energy system has the greatest capacity for energy production, (i.e., endurance?) (a) ATP-PCr (b) lactic acid (c) anaerobic glycolysis (d) oxygen (e) phosphagens 10. Which of the following is not needed to calculate the estimated energy requirement (EER)? (a) body fat percentage (b) age (c) height (d) weight (e) physical activity level (PAL) 1. b; 2. e; 3. c; 4. b; 5. c; 6. a; 7. b; 8. e; 9. d; 10. a.

1. Which energy system would predominate in an all-out, high-intensity, 400-meter dash in track? (a) ATP-PCr (b) lactic acid (c) oxygen–carbohydrate (d) oxygen–fat (e) oxygen–protein 2. If a 50 kilogram body-weight athlete was exercising at an oxygen consumption level of 2.45 liters (2,450 ml) per minute, approximately how many METS would she be attaining? (a) 8 (b) 10 (c) 11 (d) 12 (e) 14 (f) insufficient data to calculate the answer 3. Which of the following classifications of physical activity is rated as light, mild aerobic exercise—because it is likely to burn less than 7 Calories per minute? (a) competitive racquetball (b) running at a speed of 7 miles per hour (c) walking at a speed of 2.0 miles per hour (d) competitive singles tennis (e) bicycling at a speed of 12 miles per hour 4. Which of the following statements relative to the basal metabolic rate or resting metabolic rate is false? (a) The BMR is high in infancy but declines throughout adolescence and adulthood.

Review Questions—Essay 1. If an individual performed 5,000 footpounds of work in one minute, how many kilojoules of work were accomplished? 2. Name the sources of energy stored in the human body and discuss their role in the three human energy systems.

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3. Differentiate between BMR, RMR, BEE, REE, TEF, TEE, EER, and TDEE as defined in this text. 4. Explain the role of the three energy systems during exercise and provide an example using track running events. Which muscle

fiber types are the major source of energy production during these track events? 5. List the major causes of fatigue during exercise and indicate how various nutritional interventions may help prevent premature fatigue.

References Books Fox, E. L. 1979. Sports Physiology. Dubuque, IA: Wm. C. Brown. Houston, M. 2006. Biochemistry Primer for Exercise Science. Champaign, IL: Human Kinetics. Lee, R., and Nieman, D. 2003. Nutritional Assessment. Boston: McGraw-Hill. Mooren, F., and Völker, K. 2005. Molecular and Cellular Exercise Physiology. Champaign, IL: Human Kinetics. National Academy of Sciences. 2002. Dietary Reference Intakes for Energy, Carbohydrates, Fiber, Fat, Protein, and Amino Acids (Macronutrients). Washington, DC: National Academy Press. Welk, G. 2002. Physical Activity Assessments for Health-Related Research. Champaign, IL: Human Kinetics.

Review Articles Ainsworth, B. 2003. The compendium of physical activities. President’s Council on Physical Fitness and Sports Research Digest 4 (2): 1–8. Baker, L., and Kenney, W. L. 2007. Exercising in the heat and sun. President’s Council on Physical Fitness and Sports Research Digest 8 (2):1–8. Brooks, G. A. 1998. Mammalian fuel utilization during sustained exercise. Comparative Biochemistry and Physiology: Part B. Biochemistry and Molecular Biology 120:89–107. Budgett, R. 1998. Fatigue and underperformance in athletes: The overtraining syndrome. British Journal of Sports Medicine 32:107–10. Cairns, S., et al. 2005. Evaluation of models used to study neuromuscular fatigue. Exercise and Sports Sciences Reviews 33:9–16 Conley, K., et al. 2001. Limits to sustainable muscle performance: Interaction between glycolysis and oxidative phosphorylation. Journal of Experimental Biology 204:3189–94. Coyle, E. 2007. Physiological regulation of marathon performance. Sports Medicine 37:306–11. Davis, J. M., et al. 2000. Serotonin and central nervous system fatigue: Nutritional considerations. American Journal of Clinical Nutrition 72:573S–78S. de Jonge, L., and Bray, G. A. 1997. The thermic effect of food and obesity. Obesity Research 5:622–31. Dempsey, J., et al. 2008. Respiratory system determinants of peripheral fatigue and endurance performance. Medicine & Science in Sports & Exercise 40:457–61. Edgerton, V. R., and Roy, R. R. 2006. The nervous system and movement. In ACSM’s Advanced Exercise Physiology, ed. C. M. Tipton. Philadelphia: Lippincott Williams & Wilkins. Evans, W., and Lambert, C. 2007. Physiological basis of fatigue. American Journal of Physical Medicine & Rehabilitation 86:S29–S46.

Fitts, R. 2008. The cross-bridge cycle and skeletal muscle fatigue. Journal of Applied Physiology 104:551–58. Fitts, R. H. 2006. The muscular system: Fatigue processes. In ACSM’s Advanced Exercise Physiology, ed. C. M. Tipton. Philadelphia: Lippincott Williams & Wilkins. Gastin, P. 2001. Energy system interaction and relative contribution during maximal exercise. Sports Medicine 31:725–41. Goran, M. I. 1997. Genetic influence on human energy expenditure and substrate utilization. Behavior Genetics 27:389–99. Green, H. 2004. Mechanisms and management of fatigue in health and disease: Symposium introduction. Canadian Journal of Applied Physiology 29:264–73. Hagberg, J., and Pena, N. 1989. Bicycling’s exclusive calorie counter. Bicycling 30:100–103. Halson, S., and Jeukendrup, A. 2004. Does overtraining exist? An analysis of overreaching and overtraining research. Sports Medicine 34:967–81. Hargreaves, M. 2005. Metabolic factors in fatigue. Sports Science Exchange 18 (3):1–6. Hargreaves, M. 2000. Skeletal muscle metabolism during exercise in humans. Clinical and Experimental Pharmacology and Physiology 27:225–28. Hawley, J., and Hopkins, W. 1995. Aerobic glycolytic and aerobic lipolytic power systems. Sports Medicine 19:240–50. Holloszy, J. O., et al. 1998. The regulation of carbohydrate and fat metabolism during and after exercise. Frontiers in Bioscience 3:D1011–27. Hoppeler, H., and Weibel, E. 2000. Structural and functional limits for oxygen supply to muscle. Acta Physiologica Scandinavica 168:445–56. International Life Sciences Institute. 2000. Measurement of moderate physical activity: Advances in assessment techniques. Medicine & Science in Sports & Exercise 32: S438–516. Jeukendrup, A., et al. 2000. The bioenergetics of World Class Cycling. Journal of Science and Medicine in Sport 3:414–33. Kearney, J. T., et al. 2000. Measurement of work and power in sport. In Exercise and Sport Sciences, eds. W. E. Garrett and D. T. Kirkendall. Philadelphia: Lippincott Williams & Wilkins. Knuttgen, H. 1995. Force, work, and power in athletic training. Sports Science Exchange 8(4):1–6. Kovacs, M. 2007. Tennis physiology: training the competitive athlete. Sports Medicine 37:189–98. Kuo, A., et al. 2005. Energetic consequences of walking like an inverted pendulum: Step-to-step transitions. Exercise and Sports Sciences Reviews 33:88–97. Lambert, C., and Flynn, M. 2002. Fatigue during high-intensity intermittent exercise: Application to bodybuilding. Sports Medicine 32:511–22. Lambert, E., et al. 2005. Complex systems model of fatigue: Integrative homeostatic control of periph-

eral physiological systems during exercise in humans. British Journal of Sports Medicine 39:52–62. Lange, B., and Bury, T. 2001. Physiologic evaluation of explosive force in sports. Revue Medicale de Liege 56:233–38. Levine, J. 2005. Measurement of energy expenditure. Public Health Nutrition 8:1123–32. Levine, J. 2004. Non-exercise activity thermogenesis. Nutrition Reviews 62:S82–S97. McMahon, S., and Jenkins, D. 2002. Factors affecting the rate of phosphocreatine resynthesis following intense exercise. Sports Medicine 32:761–84. Meeusen, R., et al. 2006. The brain and fatigue: New opportunities for nutritional interventions? Journal of Sports Sciences 24:773–82. Mooren, F., et al. 2005. Inter- and intracellular signaling. In Molecular and Cellular Exercise Physiology, eds. F. Mooren and K. Völker. Champaign, IL: Human Kinetics. Myburgh, K. 2004. Protecting muscle ATP: Positive roles for peripheral defense mechanisms. Medicine & Science in Sports & Exercise 37:16–19. Neiss, A. 2005. Generation and disposal of reactive oxygen and nitrogen species. In Molecular and Cellular Exercise Physiology, eds. F. Mooren and K. Völker. Champaign, IL: Human Kinetics. Newsholme, E. 1993. Application of knowledge of metabolic integration to the problem of metabolic limitations in sprints, middle distance and marathon running. In Principles of Exercise Biochemistry, ed. J. Poortmans. Basel, Switzerland: Karger. Noakes, T. D. 2007. The central governor model of exercise regulation applies to the marathon. Sports Medicine 37:374–77. Nybo, L., and Rasmussen, P. 2007. Inadequate cerebral oxygen delivery and central fatigue during strenuous exercise. Exercise and Sport Sciences Reviews 35:110–118. O’Connor, P., and Puetz, T. 2005. Chronic physical activity and feelings of energy and fatigue. Medicine & Science in Sports & Exercise 37:299–305. Peters, A., et al. 2004. The selfish brain: Competition for energy resources. Neuroscience and Biobehavior Reviews 28:143–80. Shephard, R. 2001. Chronic fatigue syndrome: An update. Sports Medicine 31:167–94. Skinner, J. 2004. Chronic fatigue syndrome. Physician and Sportsmedicine 32 (2): 28–32. Stager, J., et al. 1995. The use of doubly labelled water in quantifying energy expenditure during prolonged activity. Sports Medicine 19:166–72. Thompson, J., et al. 1996. Effects of diet and dietplus-exercise programs on resting metabolic rate: A meta-analysis. International Journal of Sport Nutrition 6:41–61. Tremblay, A., et al. 1985. The effects of exercisetraining on energy balance and adipose tissue

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morphology and metabolism. Sports Medicine 2:223–33. Vaz, M., et al. 2005. A compilation of energy costs of physical activities. Public Health Nutrition I8:1153–83. Ward, D., et al. 2005. Accelerometer use in physical activity: Best practices and research recommendations. Medicine & Science in Sports & Exercise 37:S582–S588. Weir, J., et al. 2006. Is fatigue all in your head? A critical review of the central governor model. British Journal of Sports Medicine 40:573–86. Wyller, V. 2007. The chronic fatigue syndrome—an update. Acta Neurologica Scandinavica Supplementum 187:7–14.

Specific Studies Biewener, A., et al. 2004. Muscle mechanical advantage of human walking and running: Implications for energy cost. Journal of Applied Physiology 97:2266–74. Bloomer, R. 2005. Energy cost of moderateduration resistance and aerobic exercise. Journal of Strength and Conditioning Research 19:878–82. Burleson, M. A., et al. 1998. Effect of weight training exercise and treadmill exercise on postexercise oxygen consumption. Medicine & Science in Sports & Exercise 30:518–22. Coutts, A., et al. 2007. Monitoring for overreaching in rugby league players. European Journal of Applied Physiology 99:313–24. Crovetti, R., et al. 1998. The influence of thermic effect of food on satiety. European Journal of Clinical Nutrition 52:482–88.

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Esliger, D., and Tremblay, M. 2006. Technical reliability assessment of three accelerometer models in a mechanical setup. Medicine & Science in Sports & Exercise 38:2173–81. Gillette, C., et al. 1994. Postexercise energy expenditure in response to acute aerobic or resistive exercise. International Journal of Sport Nutrition 4:347–60. Graves, J., et al. 1987. The effect of hand-held weights on the physiological responses to walking exercise. Medicine & Science in Sports & Exercise 19:260–65. Haddock, B., and Wilkin, L. 2006. Resistance training volume and post-exercise energy expenditure. International Journal of Sports Medicine 27:143–48. Hall, C., et al. 2004. Energy expenditure of walking and running: Comparison of prediction equations. Medicine & Science in Sports & Exercise 36:2128–34. Leblanc, J. 1992. Mechanisms of adaptation to cold. International Journal of Sports Medicine 13 (Supplement 1): S169–78. Leenders, N., et al. 2006. Energy expenditure estimated by accelerometry and doubly labeled water: Do they agree? Medicine & Science in Sports & Exercise 38:2165–72. Nijs, J., et al. 2005. Chronic fatigue syndrome: Exercise performance related to immune dysfunction. Medicine & Science in Sports & Exercise 37:1647–54. Reed, G., and Hill, J. 1996. Measuring the thermic effect of food. American Journal of Clinical Nutrition 63:164–69.

Schoeller, D., and Hnilicka, J. 1996. Reliability of the doubly labeled water method for the measurement of total daily energy expenditure in freeliving subjects. Journal of Nutrition 126:348S–354S. Sjodin, A., et al. 1996. The influence of physical activity on BMR. Medicine & Science in Sports & Exercise 28:85–91. Spencer, M., and Gastin, P. 2001. Energy system contribution during 200- to 1500-m running in highly trained athletes. Medicine & Science in Sports & Exercise 33:157–62. Thomas, T., and Londeree, B. 1989. Energy cost during prolonged walking vs jogging exercise. Physician and Sportsmedicine 17 (5):93–102. Tremblay, A., et al. 1990. Long-term exercise training with constant energy intake. 2: effect of glucose metabolism and resting energy expenditure. International Journal of Obesity 14:75–81. Ward-Smith, A. J. 1999. Aerobic and anaerobic energy conversion during high-intensity exercise. Medicine & Science in Sports & Exercise 31:1855–60. Wilmore, J. H., et al. 1998. Alterations in resting metabolic rate as a consequence of 20 wk of endurance training: The HERITAGE Family Study. American Journal of Clinical Nutrition 68:66–71. Zhang, K., et al. 2004. Improving energy expenditure estimation for physical activity. Medicine & Science in Sports & Exercise 36:883–89.

Carbohydrates: The Main Energy Food

K E Y

active transport 122 added sugars 120 carbohydrate loading 145 carbohydrates 118 complex carbohydrates 119 Cori cycle 128 cortisol 132 dietary fiber 119 disaccharide 118 epinephrine 132 facilitated diffusion 122 fructose 118 functional fiber 119 galactose 118

CHAPTER L E A R N I N G

T E R M S

O B J E C T I V E S

After studying this chapter, you should be able to: 1. List the different types of dietary carbohydrates and identify foods typically rich in the different types. 2. Calculate the approximate number of Calories from carbohydrate that should be included in your daily diet. 3. Describe how dietary carbohydrate is absorbed, how it is distributed in the body, and what its major functions are in human metabolism. 4. Explain the role of carbohydrate in human energy systems during exercise. 5. Describe the various mechanisms whereby inadequate amounts of dietary carbohydrate may contribute to fatigue during exercise. 6. Understand the mechanisms whereby various dietary strategies involving carbohydrate intake (amount, type, and timing) before, during, and after exercise may help to optimize training for and competition in sport. 7. Identify athletes for whom carbohydrate loading may be appropriate, and describe the full carbohydrate loading protocol, highlighting dietary intake and exercise training considerations.

FOUR

glucagon 132 gluconeogenesis 128 glucose 118 glucose-alanine cycle 128 glucose polymer 119 gluten intolerance 158 glycemic index (GI) 124 glycemic load (GL) 125 hyperglycemia 125 hypoglycemia 125 insulin 125 lactose intolerance 157 millimole 125 monosaccharides 118 polysaccharide 119 reactive hypoglycemia 125 simple carbohydrates 118 total fiber 119

8. Evaluate the efficacy of metabolic by-products of carbohydrate metabolism as ergogenic aids. 9. Identify carbohydrate-containing foods that are considered to be more healthful and explain why. 10. Describe the effects of chronic endurance exercise training on the subsequent use of carbohydrate as an energy source during exercise, including underlying mechanisms and potential health benefits.

117

Introduction One of the most important nutrients in your diet, from the standpoint of both health and athletic performance, is dietary carbohydrate. Over the years the reputation of carbohydrate, particularly as a component of a weight-control diet, has seesawed between friend and foe. Most recently, some have dubbed carbohydrate as foe, alleging that high-carbohydrate diets are contributing to the epidemic of obesity within industrialized nations. However, most dietitians and nutrition scientists consider consumption of carbohydraterich foods to be one of the most important components of a healthful diet, not only for its potential in preventing certain chronic diseases but also as an integral part of a proper diet to lose excess body fat. However, as noted in the OmniHeart study, choosing good carbohydrates is the key. The possible health benefits of a diet high in complex carbohydrates and fiber and low in added sugars were introduced in chapter 2 and are explained further in this chapter. The role of carbohydrate foods in a weight-control plan will be addressed in chapter 11 and, as we shall

see, carbohydrates per se do not cause obesity, but excess Calories do. As noted in chapter 3, the major role of carbohydrate in human nutrition is to provide energy, and scientists have long known that carbohydrate is one of the prime sources of energy during exercise. Of all the nutrients we consume, carbohydrate has received the most research attention in regard to a potential influence upon athletic performance, particularly in exercise tasks characterized by endurance such as long-distance running, cycling, and triathloning. Such research is important to athletes who are concerned about optimal carbohydrate nutrition during training and competition. Indeed, continued research over the past quarter century has enabled sports nutritionists to provide more specific and useful responses to athletes’ questions. For example, compared to the first edition of this book published in 1983, readers of this ninth edition will note

Dietary Carbohydrates What are the different types of dietary carbohydrates? Carbohydrates represent one of the least expensive forms of Calories and hence are one of the major food supplies for the vast majority of the world’s peoples. They are one of the three basic energy nutrients formed when the energy from the sun is harnessed in plants through the process of photosynthesis. Although the energy content of the various forms of carbohydrate varies slightly, each gram of carbohydrate contains approximately 4 Calories. Carbohydrates are organic compounds that contain carbon, hydrogen, and oxygen in various combinations. A wide variety of different forms exist in nature and in the human body, and novel manufactured carbohydrates, including sports drinks, have been developed for the food industry. In general terms, the major categories of importance to our discussion are simple carbohydrates, complex carbohydrates, and dietary fiber. Simple carbohydrates, which are usually known as sugars, can be subdivided into two categories: disaccharides and mono118

C H A P T E R 4 Carbohydrates: The Main Energy Food

several significant differences concerning dietary carbohydrate recommendations to athletes. In this chapter, we explore the nature of dietary carbohydrates, their metabolic fates and interactions in the human body, their possible influence upon health status, and their potential application to physical performance, including the following: the adverse effects of lowcarbohydrate diets; the value of carbohydrate intake before, during, and after exercise; the efficacy of different types of carbohydrates; the role of carbohydrate loading; and carbohydrate foods or compounds, with alleged ergogenic properties. Although the role of sports drinks containing carbohydrate, such as Gatorade and PowerAde, is introduced in this chapter, additional detailed coverage of these beverages and their effect upon performance is presented in chapter 9: Water, Electrolytes, and Temperature Regulation.

saccharides. Saccharide means “sugar” or “sweet.” Think of saccharin, a noncaloric sweetener. The three major monosaccharides (single sugars) are glucose, fructose, and galactose. Glucose and fructose occur widely in nature, primarily in fruits, as free monosaccharides. Glucose is often called dextrose or grape sugar, while fructose is known as levulose or fruit sugar. Galactose is found in milk as part of lactose. Figure 4.1 presents two configurations illustrating the structure of monosaccharides. The combination of two monosaccharides yields a disaccharide. The disaccharides (double sugars) include maltose (malt sugar), lactose (milk sugar), and sucrose (cane sugar or table sugar). Upon digestion these disaccharides yield the monosaccharides as follows: sucrose glucose

lactose

fructose

glucose maltose

glucose

glucose

galactose

Fructose

Glucose

Galactose

H

H

H H

C

OH

C

O

HO

C

H

H

C

H H

C

O

H

C

OH

H

HO

C

H

C

OH

HO

C

H

H

C

OH

H

C

OH

H

C

OH

H

C

OH

C

O

H

C

OH

HO

C

OH

H

C

OH

C

OH

H CH2OH O

CH2OH

CH2OH

HO

O OH

HO CH OH

H

H

CH2OH O OH

OH

OH OH

OH OH

F I G U R E 4 . 1 Chemical structure of the three monosaccharides is depicted in both the linear and ring configurations. Each corner in the ring structure contains a carbon atom, for a total of six carbons for each monosaccharide.

Monosaccharides and disaccharides, such as glucose and sucrose, may be isolated from foods in purified forms known as refined sugars. Trisaccharides and higher saccharides also exist, and may be found in commonly used sweeteners such as corn syrup. For example, highfructose corn syrup, a common food additive, is a manufactured carbohydrate derived from the conversion of glucose in corn starch to fructose. Other food additives that are primarily sugar include honey, brown sugar, maple syrup, molasses, and fruit juice concentrate. Complex carbohydrates, commonly known as starches, are generally formed when three or more glucose molecules combine. This combination is known as a polysaccharide when more than ten glucose molecules are combined and may contain thousands of linked glucose molecules. Starches, which exist in a variety of forms such as amylose, amylopectin, and resistant starch, are the storage form of carbohydrates. The vast majority of carbohydrates that exist in the plant world are in polysaccharide form. Of prime interest to us are the plant starches, through which we obtain a good proportion of our daily Calories along with a wide variety of nutrients, and the animal starch, glycogen, about which we shall hear more later in relation to energy for exercise. Additionally, glucose polymers are polysaccharides prepared commercially by controlled hydrolysis of starch. Maltodextrins are common glucose polymers used in sports drinks, which are discussed later. Unfortunately, because of disagreements over the classification of various forms of carbohydrate, the term “complex carbohydrate” does not appear on the Nutrition Facts food label. You may obtain a rough estimate of the complex carbohydrate content by subtracting the grams of sugar from the grams of total carbohydrate. In some cases, the term “other carbohydrates” is used, which could include complex carbohydrates and other forms of carbohydrate as well. Fiber is a complex carbohydrate. In its recent report on Dietary Reference Intakes, the National Academy of Sciences settled on three terms to define fiber. Dietary fiber consists of nondigestible carbohydrates and lignin that are intrinsic and intact in plants; this

would include resistant starch. Functional fiber consists of isolated, nondigestible carbohydrates that have beneficial physiological effects in humans. Total fiber is the sum of dietary fiber and functional fiber. These nondigestible substances, which means that they are not digested and absorbed in the human small intestine, are usually a mixture of polysaccharides found in the plant wall or intracellular structures. The National Academy of Sciences carefully defines both dietary and functional fiber, particularly as they may impact health. In essence, dietary fiber is consumed as part of intact foods (even if mechanically altered) containing other macronutrients, such as digestible carbohydrate and protein. For example, cereal brans derived from whole grains contain carbohydrate and protein, along with nondigestible fiber. Some examples of dietary fiber are cellulose, hemicellulose, lignin, pectin, and gums. When studying the health effects of dietary fiber, it is difficult to determine if health benefits are attributed to dietary fiber or to other potential healthful substances, such as certain phytochemicals, found in the food. The definition of dietary fiber includes the phytochemicals that come with it. Functional fibers, on the other hand, may be isolated or extracted from foods by chemical or other means, and may be manufactured synthetically. For example, various gums may be extracted from seeds and used as food ingredients for various purposes. Some examples of functional fiber are pectin, gums, and resistant starch. The specific fiber needs to demonstrate a physiological effect in the body to be classified as a functional fiber, and this effect may be associated with a specific health benefit. Total fiber is the sum of dietary fiber and functional fiber. A specific fiber may be classified as both dietary fiber and functional fiber. For example, cellulose can be classified as dietary fiber as a natural ingredient of an intact food, or it may be considered to be a functional fiber if extracted from a natural source and added to another food. Previously, the various components of dietary and functional fiber have been classified on the basis of their solubility in water. Some fibers have been referred to as water soluble because they have been found to dissolve or swell in water and may be metabolized by bacteria in the large intestine. Others which do not possess these characteristics have been referred to as water-insoluble fibers. Common water-soluble fibers include gums, beta-glucans, and pectins. Common water-insoluble fibers include cellulose, hemicellulose, and lignin. Each of these types of fibers may confer specific health benefits, which will be discussed later in this chapter. Sugar substitutes are designed to provide the sweetness of sugars, but with no or fewer Calories. Two of the most commonly used sugar substitutes include aspartame, a derivative of two amino acids, and sucralose, made from sugar. Health aspects of sugar substitutes are discussed later. A summary of the different types of carbohydrates is presented in table 4.1, and the effects of different forms of carbohydrate on physical performance or health are presented later in this chapter.

What are some common foods high in carbohydrate content? Three of the six Food Exchanges are the primary contributors of carbohydrate in the diet; per serving, the starch exchange contains 15 grams, the fruit exchange 15 grams, and the vegetable www.mhhe.com/williams9

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bohydrate, over 50 percent of its energy content. Table 4.2 shows some foods in the different Food Exchanges that have high Monosaccharides Disaccharides Polysaccharides Other carbohydrates carbohydrate content. A more extensive listing is provided in appendix E. Complex-carbohyGlucose Sucrose Plant starch Sorbitol (sugar alcohol) drate foods are accentuated, as they are highly Fructose Maltose Amylose Ribose (a five-carbon sugar) recommended in the Prudent Healthy Diet. Galactose Lactose Amylopectin Miscellaneous foods such as sodas, fruit Resistant starch ades, candy, pies, cake, and other processed Animal starch sweets are high in carbohydrates. Added sugGlycogen ars is the term applied to refined sugars that Dietary/ are added to foods during production. ReadDietary fiber Functional fiber Functional fiber** ing food labels will provide you with the total amount of carbohydrate in grams, grams of Hemicellulose Polydextrin Beta-glucans sugar, and grams of fiber. The label will also Resistant starch* Psyllium Cellulose provide you with the percentage of your recResistant starch* Gums ommended Daily Value for total carbohydrate Pectins and fiber, as explained on pages 60–62. *Certain forms As carbohydrates are the major fuel for **Dietary fiber if found intact in food; Functional fiber if extracted and added to foods. most exercise tasks, several products have ***See text for food sources of the types of dietary carbohydrates. been marketed to athletes, particularly sports exchange 5 grams. Some foods in the meat and milk groups also drinks, sports gels, and sports bars. Sports drinks, like Gatorade and contain moderate to high amounts of carbohydrate. Dried beans and PowerAde, usually contain about 6–8 percent carbohydrates, or peas, because their protein content is comparable to meat, may be about 14–18 grams of carbohydrate per 8 fluid ounces. The carbolisted in the meat and meat substitute group. One-third cup of navy hydrate source in each varies, but usually contains a mixture of one beans contains 15 grams of carbohydrate, which is nearly 70 percent of the following: glucose, fructose, sucrose, and glucose polymers. of its energy content. A glass of skim milk contains 12 grams of carMore details on sports drinks are presented in chapter 9. Sports gels, TABLE 4.1

Types of dietary carbohydrates***

TABLE 4.2

Foods high in carbohydrate content (grams per serving)†

Starch exchange (15 grams)

Fruit exchange (15 grams)

Vegetable exchange (5 grams)

Milk exchange (12 grams)

Meat exchange (15 grams)

Whole grain Brown rice Corn tortillas Granola Oatmeal Ready-to-eat cereal* Rye crackers Whole wheat bread Enriched Bagels English muffins Pasta Ready-to-eat cereal* White bread White rice Starchy vegetables Corn Green peas Potatoes

Apples Apricots Bananas Blueberries Cantaloupe Cherries Dried fruits Fruit juices Oranges Peaches Pineapple Plums Raspberries

Asparagus Broccoli Carrots Mushrooms Radishes Rutabaga Squash, summer Tomatoes Zucchini

Ice milk Rice milk Skim milk Soy milk Yogurt, fruit

Kidney beans Navy beans Split peas Lentils

Sports drinks/ sports gels/ sports bars (14–52 grams) Gatorade Gatorade Energy Drink PowerAde ReLode GU Power Gel Power Bar Clif Bar PRBar

Miscellaneous (10–40 grams) Candy Cookies Fruit ades Soft drinks

*May be whole wheat or enriched, depending on the brand. † Typical serving sizes are: Starch exchange (1 slice bread, 1⁄2 cup cereal); Fruit exchange (1 medium; 1⁄2 cup); vegetable exchange (1⁄2 cup); Milk exchange (1 cup; 8 fluid ounces); Meat substitute exchange (1⁄2 cup). Check food labels as grams of carbohydrate per serving, especially for cereals and sports products, may vary considerably.

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TABLE 4.3

Fiber content in some common foods†

Beans Vegetables Fruits Breads and cereals* Nuts and seeds

7–9 grams per 1⁄2 cup, cooked 3–5 grams per 1⁄2 cup, cooked 1–3 grams per piece 1–3 grams per serving 2–5 grams per ounce

*Fiber content may vary considerably in bran-type cereals, ranging up to 13–14 grams per serving. Select whole-grain products for higher fiber content. † Check food labels for grams of fiber per serving.

such as ReLode, GU, Power Gel, and Clif-Shot, contain forms of carbohydrates similar to those used in sports drinks, but in a more solid gel form. They come in small squeeze containers (usually about 1 ounce) and contain roughly 20–30 grams of carbohydrate. Sports bars are also high in carbohydrate, usually with small amounts of protein and fats. The amount and type of carbohydrate per bar varies, the amount generally ranging between 20 to 45 grams. So-called “energy” drinks may contain substantial amounts of carbohydrate, often 30 to 50 or more grams in 8 ounces. Again, Nutrition Facts food labels on sports and “energy” drinks, sports gels, and sports bars provide information on the nutrient content, including amount of total carbohydrate, sugar, and fiber, as well as other ingredients such as caffeine, amino acids, vitamins, and minerals. By careful label reading and price comparisons, you may be able to get a better buy on some products. For example, sports bars are rather expensive, so purchasing lower-cost granola bars that contain similar nutrient value may provide some financial savings. Foods high in dietary fiber include most vegetables and fruits, foods in the starch exchange made from whole grains, and dried beans and peas in the meat exchange. Wheat products are good sources of insoluble fiber, while oats, beans, dried peas, fruits, and vegetables are excellent sources of soluble fiber. Because of the purported health benefits of fiber, cereal manufacturers have released new products containing 13–14 grams of fiber per serving. Psyllium, rich in both soluble and insoluble fiber, is now added to several breakfast cereals. Table 4.3 presents the average fiber content in some common foods. Food labels also document fiber content per serving. Currently food labels document total fiber content per serving, but future labels may contain both dietary and functional fiber content.

How much carbohydrate do we need in the diet? As we shall see, the human body can convert part of dietary protein and fat to carbohydrate. Thus, the National Academy of Sciences indicated that the lower limit of dietary carbohydrate compatible with life apparently is zero, provided that adequate amounts of protein and fat are consumed. Several populations around the world have subsisted on a diet with minimal amounts of carbohydrate without any apparent adverse effects. However, given that a very low carbohydrate diet may be associated with various micronutrient deficiencies and health problems in Western societies, DRI recently have been developed for carbohydrate and total fiber, and may be found in the DRI table for macronutrients in the front inside cover. The RDA for carbohydrates is set at 130 grams per day for adults and children, which is based on the average minimum amount of glu-

cose utilized by the brain. Fehm and others noted that although the brain constitutes only 2 percent of body mass, its metabolism accounts for 50 percent of total body glucose utilization. The Academy developed an Acceptable Macronutrient Distribution Range (AMDR), recommending that 45–65 percent of the daily energy intake be derived from carbohydrate. The AMDR for individuals has been set for carbohydrate based on scientific evidence suggesting such an intake may play a role in the prevention of increased risk of chronic diseases and may also ensure sufficient intakes of essential nutrients. Most of us consume carbohydrate within this range and meet the RDA, as men consume an average 200–330 grams per day while women average 180–230 grams per day. The Daily Value (DV) for carbohydrate on the food label is based on a recommendation of 60 percent of the caloric intake. The Daily Value (DV) for a 2,000 Calorie diet is 300 grams of carbohydrate, which represents 60 percent of the daily caloric intake (4 × 300 = 1,200 carbohydrate Calories; 1,200/2,000 = 60 percent). The Academy also recommended that no more than 25 percent of total Calories should come from added sugars. This standard was set based on evidence that individuals who exceed this level may not be obtaining adequate amounts of essential micronutrients that are not present in foods and beverages that contain added sugars. It should be stressed that the 25 percent is the maximal amount, not a recommended goal. In fact, the recommendation from most health professionals is to reduce this amount to approximately 10 percent. Current estimates of sugar intake approximate 12–14 percent of daily energy intake. The Academy recommends an Adequate Intake (AI) for total fiber as follows: • Men 38 grams up to age 50 30 grams over age 50 • Women 25 grams up to age 50 21 grams over age 50 The DV for a 2,000 Calorie diet is 25 grams of fiber, or 12.5 grams per 1,000 Calories. Thus, the DV is in accord with the AI for women but somewhat lower than the AI for men. The current average amount of total fiber intake is approximately 12–14 grams per day, so most individuals are not meeting this recommendation. An increased intake of complex carbohydrates would help meet this recommendation. Inadequate intake of dietary carbohydrate can have a negative impact on physical performance. Sports nutritionists also recommend a high-carbohydrate diet for individuals engaged in athletic training programs. The general recommendation for most athletes parallels the recommended dietary goals noted above. For an athlete consuming 3,000 Calories per day, 55–60 percent from carbohydrate would be 1,650–1,800 Calories, or about 400–450 grams. However, Melinda Manore, an international authority in sports nutrition, noted that the amount of carbohydrate recommended will depend on the type of sport, level of fitness, and body composition. Thus, the amount of carbohydrate needed by an individual exercising to lose weight will be quite different from the amount needed by an individual in training to run a marathon. These considerations will be discussed later in this chapter and in chapter 11. www.mhhe.com/williams9

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Many recent dietary surveys conducted with athletes, including endurance athletes, often reveal a carbohydrate intake significantly lower than these recommendations. Inadequate intake of dietary carbohydrate can have a negative impact on physical performance.

Daily Value (DV) for carbohydrate is 300 grams and for dietary fiber 25 grams, based on a 2,000 Calorie diet.

C h e c k f o r Yo u r s e l f Ke y C o n c e p t s 䉴 Dietary carbohydrates include monosaccharides and disaccha-

rides (simple sugars) and polysaccharides (complex carbohydrates). Most foods in the starch, fruit, and vegetable exchanges contain a high percentage of carbohydrate, primarily complex carbohydrates. 䉴 The RDA for carbohydrate is 130 grams daily, while the AMDR is 45–65 percent of energy intake.The AI for total fiber is 38 and 25 grams per day for young men and women, respectively, and somewhat lower for older men and women. However, the

Peruse food labels of some of your favorite foods and check carbohydrate. Pay particular attention to percent of daily value for total carbohydrates, sugars, and fiber.

Metabolism and Function

The food we eat needs to be processed before the nutrients it contains may be used in the body for their various purposes. This process includes digestion, absorption, and excretion of nutrients, which is the responsibility of our gastrointestinal (GI) system, or alimentary canal, which extends from the mouth to the anus. Figure 4.2 presents the main organs involved in the GI system, some of their basic digestive functions, and site of nutrient absorption, which will be discussed in the following chapters. Organ Digestive Functions Digestion is the process by which Release of starch-digesting (amylase) enzyme 1 Mouth and food is broken down mechanically salivary glands and chemically in the digestive tract Move food to stomach by peristaltic waves 2 Esophagus and converted into absorbable forms. Store, mix, dissolve, and continue digestion of food Specific enzymes break down foods 3 Stomach Absorb alcohol (20% of total) and water into smaller substances that may be Production of bile to aid in fat digestion and 4 Liver absorption absorbed. Specific enzymes of interReceives most nutrients from the small intestine est regarding carbohydrates, fats, and 1 Storage, concentration, and later release of bile 5 Gallbladder protein will be discussed where into the small intestine appropriate. Absorption of nutrients, Pancreas Secretion of sodium bicarbonate and carbohydrate-, 6 fat-, and protein-digesting enzymes as noted in figure 4.2, may occur in Digestion and absorption of most substances using 7 Small intestine the stomach and large intestine, but enzymes made by the pancreas and small intestine 2 Duodenum the vast majority of nutrients are Monosaccharides Calcium absorbed through the millions of villi Magnesium Iron Water Alcohol lining the small intestine. Some subJejenum Monosaccharides Fatty acids stances are absorbed by diffusion, 4 Peptides Fat-soluble vitamins 3 which may be passive or facilitated. Amino Acids Water-soluble vitamins Water Alcohol In passive diffusion the substance 5 6 Ileum simply diffuses across the cell memPeptides Vitamin B Amino acids Bile acids brane. Osmosis is the passive diffuWater sion of water. In facilitated diffusion, Absorption of sodium, potassium, and water 7 8 8 Large intestine Formation of feces a receptor in the cell membrane is Store feces and expel via the anus needed to transport the substance 9 Rectum and Anus from the intestine into the villi. No 9 energy is required for diffusion, but other substances need energy supF I G U R E 4 . 2 The alimentary canal. The alimentary canal includes the mouth, the esophagus, plied by the villi cells in order to be the stomach, the small intestine (duodenum, jejunum, ileum), the large intestine (colon), the rectum, absorbed, a process known as active and the anal canal.Various glands and organs including the salivary glands, the gallbladder, and the transport. Figure 4.3 presents a cross pancreas secrete enzymes and other constituents into the digestive tract. Most blood draining from section of a villus and highlights the intestines goes to the liver for processing. Note the general sites in the digestive tract where some of the key nutrients and the principal nutrients and other substances are absorbed (although there is some overlap in the exact associated process of absorption. site of absorption). Most absorption of nutrients occurs throughout the small intestine. 12

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C H A P T E R 4 Carbohydrates: The Main Energy Food

pancreas. Saliva amylase initiates digestion of the polysaccharides to disaccharides, but most occurs in Osmosis Diffusion Active the small intestine by pancreatic transport amylase. Enzymes then digest the disaccharides to monosaccharides, which are absorbed by specific Epithelial cells receptors in the villi. Amino acids Monosacchrides The composition of the dietary Electrolytes carbohydrate may influence delivFatty acids Monosacchrides ery into the body. For example, as Electrolytes noted later in this chapter, sports Water drinks may be designed to take advantage of the different monosaccharide receptors in the villi. Moreover, sports drinks containing carbohydrate and sodium may enhance water absorption via a cotransport mechanism, a topic that is discussed in chapter 9. Simple columnar epithelium Optimal functioning of the GI tract following carbohydrate Lacteal intake has been studied extensively Blood or lymph vessel because improper functioning may Villus Capillary network impair athletic performance. For (b) example, although there is very little digestion of carbohydrate in the stomach, the rapidity with F I G U R E 4 . 3 (a) Basic structure of the villus. which carbohydrate leaves the Millions of villi in the small intestine absorb the stomach, and its impact upon the digested nutrients. Most nutrients are absorbed into absorption of water, may be the capillaries and are transported in the blood. Fats important considerations for athare absorbed primarily in the lacteal, being letes involved in prolonged exertransported to the lymph vessels and eventually into cise under warm environmental the blood. (b) Nutrients are absorbed into the body in conditions. various ways.Water enters the cell by osmosis, most Arteriole Certain dietary practices may Venule fatty acids by diffusion, and amino acids enter via predispose individuals to gastroinLymph vessel active transport, a process that requires energy. testinal distress, which will comMonosaccharides and electrolytes may use two path(a) ways, (i.e., diffusion and active transport). promise exercise performance. High concentrations of simple sugars, particularly fructose, may exert a reverse osmotic effect in the intestines, drawing water from the circulatory system into the intestinal lumen. The resulting symptoms How are dietary carbohydrates digested and are referred to as the dumping syndrome and include weakness, absorbed and what are some implications for sweating, and diarrhea. Lactose may present a problem to some athsports performance? letes, and its possible effects are discussed later in the chapter. Carbohydrates usually are ingested in the forms of polysaccharides (starches), disaccharides (sucrose, maltose, and lactose), and monosaccharides (glucose and fructose). In addition, special carWhat happens to the carbohydrate bohydrate compounds, such as glucose polymers, have been develafter it is absorbed into the body? oped for athletes. In order to be useful in the body, these Of the three monosaccharides, glucose is of most importance to carbohydrates must be digested, absorbed, and transported to human physiology. Most dietary carbohydrates are broken down appropriate cells for metabolism. to glucose for absorption into the blood, while the majority of the The digestion and absorption of dietary carbohydrates are absorbed fructose and galactose are converted to glucose by the highlighted in figure 4.4. The enzyme that digests complex carboliver. Glucose is the blood sugar. hydrates is amylase, which is secreted by the salivary glands and Lumen of Intestine

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Carbohydrates Salivary gland

1 1

2 Esophagus

3

4 5 Liver

2

Stomach

3 Pancreas

5

6 Large intestine 4 Small

6

intestine

7 7

Some starch is broken down to maltose in the mouth by salivary amylase.

Salivary amylase is inactivated by strong acid in the stomach. Pancreatic amylase breaks down starch into maltose in the small intestine. Enzymes in the wall of the small intestine break down the disaccharides sucrose, lactose, and maltose into monosaccharides glucose, fructose, and galactose.

Glucose, fructose, and galactose are absorbed into blood to be taken to the liver by a portal vein.

Some soluble fiber is fermented into various acids and gases by bacteria in the large intestine.

Insoluble fiber escapes digestion and is excreted in feces, but little other dietary carbohydrate is present.

Anus

Carbohydrate digestion and absorption. Enzymes made by the mouth, pancreas, and small intestine participate in the process of digestion. Most carbohydrate digestion and absorption take place in the small intestine.

FIGURE 4.4

The glycemic index (GI) represents a ranking system relative to the effect that consumption of 50 grams of a particular carbohydrate food has upon the blood glucose response over the course of two hours. The normal baseline measure is 50 grams of glucose, and the resultant blood glucose response is scored as 100. In general, the following values are used to rank the glycemic index of foods: • 70 or more—High GI foods • 69-55—Medium GI foods • 55 or less—Low GI foods Many factors other than its carbohydrate content, such as the physical form (coarse or fine) and serving mode (raw or cooked), may influence the glycemic index of any given food. Moreover,

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C H A P T E R 4 Carbohydrates: The Main Energy Food

the glycemic index for any given food may vary considerably between individuals, so although some general values of the glycemic index may be given, the effects of different foods should be tested individually in those who are concerned about their blood sugar levels. In general, foods containing high amounts of refined sugars have a high glycemic index because they lead to a rapid rise in the blood sugar, but some starchy foods also have a high glycemic index. On the other hand, foods high in fiber, such as beans, generally have a low glycemic index. Interestingly, fructose has a low glycemic index, which is one of the reasons its use as the primary carbohydrate source in sports drinks had been advocated for endurance athletes. We discuss the role of fructose later in this chapter. Table 4.4 classifies some common foods according to their glycemic index.

The glycemic load (GL) also represents a ranking system relative to the effect that eating a carbohydrate food has on the blood glucose level, but also includes the portion size. While the glycemic index is based on 50 grams of a particular food, a typical serving size for that food may be 6–8 ounces (180–240 grams). The GL is calculated by the following formula: GL ⫽ (Glycemic index) ⫻ (grams of non-fiber carbohydrate in one serving) 100 The following values are used to rank the glycemic load of foods: • 20 or more—High GL foods • 19-11—Medium GL foods • 10 or less—Low GL foods The GL for some foods is presented in table 4.4. Keegan has noted that the usefulness of the glycemic index or glycemic load is the subject of debate. As noted, one person’s glycemic response to a given food may be very different from someone else’s response. Moreover, individuals do not normally consume carbohydrate foods by themselves, but usually with other foods containing fat and protein such as a hamburger on a bun. The addition of fat and protein will usually reduce the glycemic index and glycemic load. Nevertheless, Keegan indicates the glycemic index and glycemic load have been used to help select more healthful carbohydrates. In general, the lower the glycemic index or glycemic load, the more healthful the source of carbohydrate, as discussed later in this chapter. www.mendosa.com/gilists.htm Check the glycemic index and the glycemic load for a wide variety of carbohydrate-containing foods.

What is the metabolic fate of blood glucose? Normal blood glucose levels (normoglycemia) range between 80–100 milligrams per deciliter of blood (80–100 mg/ml, or 80–100 milligram percent). The maintenance of a normal blood glucose level is very important for proper metabolism. Thus, the human body possesses a variety of mechanisms, primarily hormones, to help keep blood glucose levels under precise control. The rise in blood glucose, also known as serum glucose, stimulates the pancreas to secrete insulin into the blood. Insulin is a hormone that facilitates the uptake and utilization of glucose (facilitated diffusion) by various tissues in the body, most notably the muscles and adipose (fat) tissue. Cell membranes contain receptors to transport glucose into the cell. The primary receptors in muscle and fat cell membranes are known as GLUT4 receptors, which are directly activated by insulin (see figure 4.5). Exercise also activates these receptors to transport blood glucose into the muscle cell, independently of the effect of insulin. Other hormones, discussed later in this chapter, are also involved in regulating blood glucose. With normal amounts of carbohydrate intake in a mixed meal, blood glucose levels remain normal.

However, foods with a high glycemic index may lead rapidly to high blood glucose levels, possibly hyperglycemia (> 140 mg percent), which will cause an enhanced secretion of insulin from the pancreas. High serum levels of insulin will then lead to a rapid, and possibly excessive, transport of blood glucose into the tissues. This may lead in turn to hypoglycemia (< 40–50 mg percent), or low blood glucose level. This insulin response and reactive hypoglycemia following carbohydrate intake may be an important consideration for some athletes and is discussed later. Foods with a low glycemic index, particularly soluble fiber forms, lead to a slower insulin response and a more stable blood glucose level. Consuming a diet based on the glycemic index has been studied as a possible means to enhance health, as well as sports performance, as noted later in this chapter. The fate of blood glucose is dependent upon a multitude of factors, and exercise is one of the most important. The following points represent the major fates of blood glucose. Figure 4.6 schematically represents these fates. 1. Blood glucose may be used for energy, particularly by the brain and other parts of the nervous system that rely primarily on glucose for their metabolism. Hypoglycemia can impair the normal function of the brain. Although hypoglycemia as a clinical condition is quite rare in the general population, transitory hypoglycemia may occur in very prolonged endurance exercise. 2. Blood glucose may be converted to either liver or muscle glycogen. It is important to note that liver glycogen may later be reconverted to blood glucose. However, this does not occur to any appreciable extent with muscle glycogen. In essence, glucose is locked in the muscle once it enters, owing to the lack of a specific enzyme needed to change its form so it can cross the cell membrane back into the bloodstream. Most of the muscle glycogen is converted to this locked form of glucose during the production of energy. Researchers discovered two forms of muscle glycogen, proglycogen and macroglycogen. Hargreaves indicates that the functional significance of these glycogen forms remains to be fully elucidated. Houston indicates that proglycogen seems to be preferentially used during muscle activity, while the macroglycogen may be more of a reserve supply of carbohydrate for prolonged exercise. In this text we shall use the term glycogen to represent both forms. 3. Blood glucose may be converted to and stored as fat in the adipose tissue. This situation occurs when the dietary carbohydrate, in combination with caloric intake of other nutrients, exceeds the energy demands of the body and the storage capacity of the liver and muscles for glycogen. 4. Some blood glucose also may be excreted in the urine if an excessive amount occurs in the blood because of rapid ingestion of simple sugars.

How much total energy do we store as carbohydrate? A common method to express the concentration of carbohydrate stored in the body is in millimoles (mmol). A millimole is 1/1000 of a mole, which is the term representing gram molecular weight.

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TABLE 4.4

Glycemic Index (GI) and Glycemic Load (GL) of common foods

Reference food glucose = 100 Low GI foods—below 55 Intermediate GI foods—between 55 and 69 High GI foods—more than 70

Low GL foods—below 10 Intermediate GL foods—between 11 and 19 High GL foods—more than 20

Serving

Glycemic

Carbohydrate

Glycemic

Size (grams)

Index (GI)*

(grams)

Load (GL)

1 cup 1 cup 1 cup 1 cup

55 56 72 41

46 45 53 40

25 25 38 16

1 cup 1 cup 1 cup 1 cup

49 55 85 62

16 39 57 29

8 21 48 18

1 cup 1 cup 1 cup 1 cup

27 32 33 61

11 12 17 31

3 4 6 19

1 cup 1 cup 1 cup 1 cup

48 27 30 38

54 38 40 54

26 10 12 21

1 tsp 1 tsp 1 tsp 1 tsp

73 65 23 46

6 5 5 5

4 3 1 2

1 small 1 slice 1 slice 1 small

72 69 70 67

30 13 10 26

22 9 7 17

1 medium 1 medium 1 medium 1 medium

38 55 25 44

22 29 32 15

8 16 8 7

1 cup 1 cup 1 cup 1 cup

40 46 78 63

29 26 15 26

12 13 12 16

1 oz 5 cookies 1 oz 1 oz

54 77 49 80

15 15 18 26

8 12 9 21

Pastas/grains Brown rice White, long grain White, short grain Spaghetti

Vegetables Carrots, boiled Sweet corn Potato, baked New (red) potato, boiled

Dairy foods Milk, whole Milk, skim Yogurt, low-fat Ice cream

Legumes Baked beans Kidney beans Lentils Navy beans

Sugars Honey Sucrose Fructose Lactose

Breads and muffins Bagel Whole-wheat bread White bread Croissant Fruits Apple Banana Grapefruit Orange

Beverages Apple juice Orange juice Gatorade Coca-Cola

Snack foods Potato chips Vanilla wafers Chocolate Jelly beans *Based on a comparison to glucose Source: Foster-Powell, K. and others: International table of glycemic index and glycemic load. American Journal of Clinical Nutrition 76:5, 2002.

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C H A P T E R 4 Carbohydrates: The Main Energy Food

Without insulin Most GLUTs are stored in membrane-bound vesicles inside the cell, but a few are in the plasma membrane.

With insulin Glucose molecule

Vesicles fuse with the plasma membrane, exposing more GLUTs to the extracellular fluid.

More glucose is taken up by cell.

GLUT

Insulin promotes the transport of glucose across plasma membranes.This is done by the recruitment of intracellular vesicles containing glucose transporter (GLUT) proteins to the plasma membrane, where they facilitate glucose diffusion into the cell.

FIGURE 4.5

Blood glucose

Muscle glycogen

Liver glycogen

Adipose tissue fat deposits

Kidney excretion in urine

Other tissues: CO2 + H2O + Energy

F I G U R E 4 . 6 Fates of blood glucose. After assimilation into the blood, glucose may be stored in the liver or muscles as glycogen or be utilized as a source of energy by these and other tissues, particularly the nervous system. Excess glucose may be partially excreted by the kidneys, but major excesses are converted to fat and stored in the adipose tissues.

In essence, a mole represents the weight in grams of a particular substance such as glucose. The chemical formula for glucose is C6H12O6, so it contains six parts of carbon and oxygen and twelve parts of hydrogen. The atomic weight of carbon is 12, hydrogen is 1, and oxygen, 16. If you multiply the number of

parts by the respective atomic weights of each of the elements for glucose [(6 × 12) + (12 × 1) + (6 × 16)], you would get a total of 180. Thus, one mole of glucose is 180 grams, or about 6 ounces. One millimole is 1/1000 of 180 grams, or 180 milligrams. (See figure 4.7.) As an illustration, the normal glucose concentration is about 5 mmol per liter of blood, or 90 mg/100 ml, (90 mg/dL). To calculate, 5 mmol × 180 mg = 900 mg/liter, which is the same as 90 mg/100 ml. The normal individual has about 5 liters of blood. Thus, this individual would have a total of 25 mmol of glucose in the blood, or a total of 4,500 milligrams (25 × 180), or 4.5 grams. These calculations have been presented here because this is the means whereby concentrations of glucose, glycogen, and other nutrients are expressed in contemporary scientific literature. A knowledge of these mathematical relationships should help you interpret research more effectively. However, because we are using the Calorie as the measure of energy in this book, and because each gram of carbohydrate equals approximately 4 Calories, an estimate of the energy content of the major human energy sources of carbohydrate may be obtained. For our purposes, the body has three major energy sources of carbohydrate—blood glucose, liver glycogen, and muscle glycogen. Some glucose (about 10–15 grams) is also found in the lymph and intercellular fluids. Initial stores of blood glucose are rather limited, totaling only about 5 grams, or the equivalent of 20 Calories (C). However, blood glucose stores may be replenished from either liver glycogen or absorption of glucose from the intestine. The liver has the greatest concentration of glycogen in the body. However, because its size is limited, the liver normally contains only about 75–100 g of glycogen, or 300–400 C. One hour of aerobic exercise uses over half of the liver glycogen supply. It is also important to note that the liver glycogen content may be decreased by starvation or increased by a carbohydrate-rich diet. Fifteen hours or more of starvation will deplete the liver glycogen, while certain dietary patterns may nearly double the glycogen content of www.mhhe.com/williams9

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number of different substrates from each of the three energy nutrients may be used and are depicted graphically in figure 4.8. 6 oz. 180 grams = 180 milligrams = Protein may be a significant source of blood glucose. Protein breaks down to 6 ounces = 0.006 ounce = amino acids in the body, and certain of 36 teaspoons 0.036 teaspoon these amino acids, notably alanine, may be converted to glucose in the liver. This is referred to as the glucose-alanine cycle, F I G U R E 4 . 7 The millimole concept.The concentration of some nutrients in the body is which is explained further in chapter 6. A often expressed in millimoles. See text for explanation. number of other amino acids also are gluconeogenic. Glucose is essential for the the liver, a condition that may be useful in certain tasks of physical brain and several other tissues. If about 130 grams of carbohydrate performance. are not consumed daily, then the body will produce the glucose it The greatest amount of carbohydrate stored in the body is in the needs, primarily from protein in the body. form of muscle glycogen. This is because the muscles compose Fats in the body break down into fatty acids and glycerol. such a large proportion of the body mass as contrasted to the liver. Although there is no mechanism in human cells to convert the One would expect large differences in total muscle glycogen confatty acids to glucose, glycerol may be converted to glucose tent between different individuals because of differences in body through the process of gluconeogenesis in the liver. size. However, for an average-sized, untrained man with about Through gluconeogenesis, one gram of protein will yield about 30 kg of his body weight consisting of muscle tissue, one could 0.56 gram of glucose. Triglycerides are about 10 percent glycerol, expect a total muscle glycogen content of approximately 360 g, or and each gram of glycerol may be converted to a gram of glucose. 1,440 C. This would represent a concentration of about 66 mmol, In addition, certain by-products of carbohydrate metabolism, or 12 grams, per kg of muscle tissue. As with liver glycogen, the notably pyruvate and lactate, may be converted back to glucose in muscle glycogen stores also may be decreased or increased, with the liver. Some of the lactic acid produced in the muscle during considerable effects on physical performance. For example, a intense exercise may be released into the blood and carried to the trained endurance athlete may have twice the amount of stored liver for reconversion to glucose. The glucose may then return to the muscle glycogen that an untrained sedentary individual has. muscles to be used as an energy source or stored as glycogen. This is If we calculate the body storage of carbohydrate as blood gluthe Cori cycle. Figure 4.9 illustrates some of the basic interrelationcose, liver glycogen, and muscle glycogen, the total is only about ships among carbohydrate, fat, and protein in human nutrition. 1,800–1,900 C, not an appreciable amount. One full day of starvation could reduce it considerably. Some normal ranges of carbohyWhat are the major functions drate stores are presented in table 4.5, although these normal ranges of carbohydrate in human nutrition? may be increased or decreased considerably by diet or exercise. The major function of carbohydrate in human metabolism is to supply energy. Some body cells, such as the nerve cells in the Can the human body make carbohydrates brain and retina and the red blood cells, are normally totally from protein and fat? dependent upon glucose for energy and require a constant source. Because the carbohydrate stores in the body are rather limited, Through a series of biochemical reactions in the body cells, gluand because blood glucose is normally essential for optimal cose is oxidized, eventually producing water, carbon dioxide, and functioning of the central nervous system, it is important to be energy. Zierler notes that although carbohydrate is an excellent able to produce glucose internally if the stores are depleted by source of energy, it is not the major fuel when the body is at rest; starvation or a zero-carbohydrate diet. This process in the body is fats are. Carbohydrate is the main fuel for certain tissues during called gluconeogenesis, meaning the new formation of glucose. A rest, such as the brain, central nervous system, and red blood cells, but provides only about 15–20 percent of muscle energy needs during rest. Thus, the body conserves its limited carbohydrate TABLE 4.5 Approximate carbohydrate stores in the body stores by using fats as the primary energy source during resting of a normal, sedentary adult conditions. As noted in chapter 3, carbohydrate can be used to produce energy either aerobically or anaerobically. Recall that in the Equivalent amount lactic acid system, ATP is produced rapidly via anaerobic glycolySource Amount in grams in calories sis, but for this system to continue functioning, the end product of glycolysis, pyruvic acid or pyruvate, must be converted into lactic Blood glucose 5 20 acid. In the oxygen system, aerobic glycolysis predominates and Liver glycogen 75–100 300–400 pyruvic acid is converted into acetyl CoA, which enters into the Krebs cycle and electron transfer system for complete oxidation Muscle glycogen 300–400 1,200–1,600 and the production of relatively large amounts of ATP. For the 1 mole glucose =

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1 millimole glucose =

C H A P T E R 4 Carbohydrates: The Main Energy Food

Fat cells

Protein

Carbohydrate

Fat

Amino acids

Glucose

Glycerol

Muscle cells

Triglycerides

Muscle protein

Muscle glycogen

Glucogenic amino acids

Pyruvate

Alanine

Lactate

Fatty acids Fatty acids

Glycerol

Pyruvate

Acetyl CoA

Blood stream

Krebs cycle Electron transport system Liver Glucose

F I G U R E 4 . 8 Gluconeogenesis.The liver is the major site for gluconeogenesis in the body.The breakdown products of fats, protein, and carbohydrate from other parts of the body may be transported to the liver by the blood for eventual reconversion into glucose. Glycerol, glucogenic amino acids, lactate, and pyruvate may be important sources for the new formation of glucose.The Cori cycle involves the transport of lactate to the liver and conversion to glucose, which may then be transported back to the muscle.

same amount of carbohydrate, anaerobic metabolism yields only two ATP, whereas aerobic metabolism yields thirty-six to thirtyeight ATP. See appendix G, figures G.1 to G.3, for more detail. Carbohydrates have some functions in the body other than energy production. Monosaccharides can be used to form other smaller carbohydrate molecules such as trioses and pentoses. These substances may combine with other nutrients and form body chemicals essential to life, such as glycolipids or glycoproteins. Glycoproteins are very important components of cell membranes, serving as receptors to help regulate cell function. Ribose is a key pentose (5-carbon sugar) that is a part of a number of indispensable compounds in the body. One of those compounds is RNA, or ribonucleic acid, which plays an important part in anabolic processes in the cells.

CO2 + H2O + Energy (ATP)

F I G U R E 4 . 9 Interrelationships among carbohydrate, fat, and protein metabolism in humans. All three nutrients may be utilized for energy, although the major energy sources are carbohydrate and fat. Excess carbohydrate may be converted to fat; the carbohydrate structure also may be used to form protein, but nitrogen must be added. Fat cannot be used to generate carbohydrate to any large extent because acetyl CoA cannot be converted to pyruvate.The glycerol component of fat possibly may form very small amounts of carbohydrate. Fats may serve as a basis for the formation of protein, but again nitrogen must be added. Excess protein cannot be stored in the body but can be converted to either carbohydrate or fat.

but is based on the typical serving size for carbohydrate foods. Different numerical rankings are used for the GI and GL. 䉴 The three sources of carbohydrate in the body of an average adult male are blood glucose (5 grams; 20 Calories), liver glycogen (75–100 grams; 300-400 Calories), and muscle glycogen (350–400 grams; 1,400–1,600 Calories). 䉴 The liver is the main organ that can produce glucose from certain by-products of protein and fat, a process known as gluconeogenesis. 䉴 The major function of carbohydrates in human metabolism is to supply energy; blood glucose is essential for optimal functioning of the nervous system, whereas muscle glycogen is essential for both anaerobic capacity and aerobic power exercise.

Ke y C o n c e p t s 䉴 Most ingested carbohydrates are initially converted into blood

glucose and used for energy or stored as liver and muscle glycogen, but excess carbohydrates may be converted into fat. 䉴 The glycemic index (GI) is a measure of the rate of digestion and absorption of 50 grams of a carbohydrate food and the resultant effect on the blood glucose level.The glycemic load (GL) is similar,

Carbohydrates for Exercise Both hypoglycemia and depleted muscle glycogen may precipitate fatigue, so maintaining optimal levels of blood glucose, liver glycogen, and muscle glycogen is essential in various athletic endeavors, particularly prolonged exercise tasks. Some sports authorities indicate carbohydrate is the master fuel for athletes. www.mhhe.com/williams9

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Indeed, Kenyan runners, who dominate world competition in endurance running events, subsist on a diet that is about 76.5 percent carbohydrate. In this section we discuss the role of carbohydrate as an energy source during exercise, the effect of training to enhance carbohydrate use for energy when needed, and various methods to provide adequate carbohydrate nutrition to the athlete before, during, and after competition, and carbohydrate intake during training.

In what types of activities does the body rely heavily on carbohydrate as an energy source? Carbohydrate supplies approximately 40 percent of the body’s total energy needs during rest with about 15–20 percent used by the muscles. During very light exercise fat is an important energy source, but van Loon and others found that muscle glycogen and plasma glucose oxidation rates increased with every increment in exercise intensity. When exercise becomes more intense, such as when a person is working at 65–85 percent of capacity, carbohydrate becomes the preferred energy source; this is the crossover concept discussed in chapter 3. At maximal or supramaximal exercise levels, carbohydrate is used almost exclusively. Thus, carbohydrate may be the prime energy source for high-intensity anaerobic events lasting for less than one minute and high-intensity aerobic events lasting over an hour or two. As Holloszy and others recently summarized, carbohydrate use, then, is associated with the intensity level of the exercise. The more intense the exercise, the greater the percentage contribution of carbohydrate. Of course, the more intense the exercise, the sooner exhaustion occurs. A fairly well-conditioned person may be able to exercise for many hours at 40–50 percent of VO2 max, for 1 to 2 hours or so at 70–80 percent of VO2 max, but only for minutes at maximal or supramaximal levels of VO2 max. As noted by Hargreaves, the fatigue that occurs in very high-intensity exercise of short duration, such as a 400-meter run, may be associated with the accumulation of hydrogen ions, a by-product of lactic acid production. On the other hand, the fatigue associated with more prolonged exercise may be connected with depleted supplies of liver and muscle glycogen, both of which may be affected by dietary practices and exercise intensity and duration. Carbohydrate intake is most important for prolonged endurance events lasting more than 90–120 minutes. Data from such endurance tasks as the Tour de France, the bicycle Race Across America, and the Ironman Triathlon, illustrate the importance of dietary carbohydrate in sustaining high energy output for prolonged periods. Most of the athletes in these events consumed high-caloric diets rich in carbohydrates both before and during competition. A classic example is the ultradistance runner from Greece, Yannis Kouros, who won the Sydney to Melbourne race in Australia, a distance of approximately 600 miles, in 5 days and 5 hours, or about 114 miles of running per day. He consumed up to 13,400 Calories per day, with up to 98 percent being derived from carbohydrates. Cyclists in major multiday races consume more than 800 grams of carbohydrate daily. Data obtained from exercise tasks of lesser magnitude, such as 130

C H A P T E R 4 Carbohydrates: The Main Energy Food

marathons (26.2 miles; 42.2 kilometers) and ultramarathons (50 kilometers and longer), also provide evidence for the importance of carbohydrate as the prime energy fuel, as evidenced in the recent review by Peters. Carbohydrate is also an essential energy fuel for prolonged sports involving many intermittent bouts of high-intensity exercise such as soccer, rugby, field hockey, ice hockey, and tennis. For example, Bangsbo recently noted that although soccer players are engaged in low-intensity exercise for about 70 percent of the time, there may be 150–250 bouts of brief intense actions during a game. Athletes in these sports repeatedly use muscle glycogen stored in their fast-twitch muscle fibers, which may lead to a selective depletion in these fibers. Bangsbo indicated muscle glycogen is the most important substrate for energy production in sports such as soccer. Environmental conditions may also increase carbohydrate use during exercise. Carbohydrate oxidation, particularly muscle glycogen, is increased during exercise in the heat. Sawka and Young indicated that the increased glycogen utilization is probably mediated by elevated epinephrine and muscle hyperthermia. They also note that lactate uptake and oxidation by the liver are impaired during exercise heat stress. However, heat acclimatization helps reduce muscle glycogen use and lactate accumulation. Mazzeo and Fulco indicate that exercising at high altitude increases blood glucose compared to sea level, possibly because hypoxia may induce translocation of glucose transporters to the cell membrane, which may facilitate glucose entry and utilization in the muscle cell. Braun indicates that under conditions of low oxygen availability, glucose utilization will provide more ATP per unit of oxygen available.

Why is carbohydrate an important energy source for exercise? Carbohydrate is the most important energy food for exercise. Besides being the only food that can be used for anaerobic energy production in the lactic acid system, it is also the most efficient fuel for the oxygen system. If we look at the caloric value of carbohydrate (1 gram = 4 C) and fat (1 gram = 9 C), we might think that fat is a better source of energy. Indeed, this is so if we just look at Calories per gram. However, more oxygen is needed to metabolize the fat, and if we look at how many Calories we get from one liter of oxygen, we will find that carbohydrate yields about 5.05 Calories and fat gives only 4.69. Thus, carbohydrate appears to be a more efficient fuel than fat, by about 7 percent. Houston notes an even greater benefit if we look at ATP production. You get more ATP from glucose than you do from a fatty acid. For each unit of oxygen consumed, glucose produces 2.7 ATP whereas palmitic fatty acid produces 2.3 ATP, a 17 percent difference. The metabolic pathways for carbohydrate are also more efficient than those for fat. In essence, during aerobic glycolysis carbohydrate is able to produce ATP for muscle contraction up to three times more rapidly than fat and even faster during anaerobic glycolysis. The primary carbohydrate source of energy for physical performance is muscle glycogen, specifically the glycogen in the muscles that are active. Elite marathon runners may use about 4–5 grams of

carbohydrate per minute. As the muscle glycogen is being used during exercise, blood glucose enters the muscles and the energy pathways. In turn, the liver will release some of its glucose to help maintain or elevate blood glucose levels and prevent hypoglycemia. Coyle noted that during moderate exercise, muscle glycogen and liver glycogen contribute equally to carbohydrate oxidation. At higher intensities, muscle glycogen use increases. Thus, all body stores of carbohydrate—blood glucose, liver glycogen, and muscle glycogen—are important for energy production during various forms of exercise. Proper physical training is essential to optimize carbohydrate utilization during exercise, as is proper carbohydrate nutrition.

What effect does endurance training have on carbohydrate metabolism? Since carbohydrate is a primary fuel for exercise, as you initiate an endurance exercise program a major proportion of your energy will be derived from your muscle glycogen stores. A single bout of exercise can activate the genes that produce GLUT-4 receptors, which can exert an insulin-type effect by facilitating the transport of blood glucose into the muscle both during and immediately following the exercise bout. As you continue your endurance exercise program, such as running or bicycling, the physical activity serves as a metabolic stressor to the body, and various tissues begin to adapt to better accommodate the exercise stress. Houston reported that as few as five days of training can exert favorable effects, such as decreasing the production of lactic acid for a standardized exercise task. These adaptations have implications for physical performance and the fuels used. Figure 4.10 schematically represents some of these changes at the cellular level. The following have been noted to occur in both males and females, young and old, after several months of endurance training: 1. You will increase your VO2 max through beneficial changes in your cardiovascular system and the oxygen system in your muscle tissues. This will help your body deliver and utilize more oxygen at the muscle tissue, significantly increasing your endurance capacity. 2. Of equal or greater importance, you will be able to work at a greater percentage of your VO2 max without fatigue. At the beginning of your training program you may reach your steady-state threshold at about 50 percent of your VO2 max and start producing lactic acid more rapidly, which may cause an early onset of fatigue. Stallknecht and others noted that training not only decreases lactic acid production during a standardized exercise task, but also increases lactic acid clearance by the liver, heart, and resting and working muscles. Thus, after training you may be able to perform at 70 percent or higher of your VO2 max without excess lactic acid accumulation. World-class marathoners may operate above 80 percent. You may wish to refer back to figure 3.14. 3. Endurance training improves insulin sensitivity by inducing an increase in the glucose transporter GLUT-4, which enables a more rapid inflow of glucose from the blood into the muscle

during exercise, and more rapid replenishment of muscle glycogen during recovery. However, Richter and others noted that although the muscle generates more GLUT-4 transporters, they are not translocated from the interior of the muscle cell to the cell membrane unless needed. Hargreaves notes that exercise training results in a lower muscle glucose uptake during exercise at the same intensity. Thus, the endurance-trained muscle may use less glucose at low-intensity exercise, but have the capacity to use more during intense, maximal exercise. 4. Endurance-trained muscle has an increased maximal capacity to utilize carbohydrates. Turcotte notes that the mitochondria readily adapt to changes in muscle use and disuse to meet functional demands of the muscle. Muscle cell mitochondria density increases. Also, LeBlanc and others reported that the enzymes that metabolize carbohydrate in the muscle cells will increase, especially oxidative enzymes associated with the Krebs cycle. This allows your muscles to process carbohydrate more efficiently. All muscle fiber types can increase their oxidative capacity to metabolize carbohydrates during exercise. 5. As we shall see in chapter 5, training also enhances the use of fat during exercise. By doing so, there is less reliance on carbohydrate oxidation during submaximal exercise. Recent research by Friedlander and others, from George Brooks’ laboratory, reveals that the oxidation of blood glucose decreases in men during both absolute and relative exercise intensity tasks; but, although noting decreased glucose flux in women during exercise for absolute exercise intensity, they found no changes during relative exercise intensity tasks. In general, these changes are beneficial and may minimize the possibility of hypoglycemia. Other research from Brooks’ laboratory suggests that training decreases the use of muscle glycogen during exercise at an absolute intensity level. 6. More glycogen is stored in the muscle. The increase in GLUT-4 receptors is partly responsible for this response, but research also reveals an increased activity of the enzyme that synthesizes glycogen. Synthesis of muscle glycogen may be twofold faster in trained versus untrained individuals. What do all these changes mean? You may be able to run a 10-kilometer (6.2 miles) road race at a 7-minute-per-mile pace instead of 8 minutes. You can cruise in high gear for longer periods because you have increased your ability to produce energy from carbohydrates. Also, by reducing your reliance on carbohydrates at lower running speeds, you may compete in more prolonged races, such as marathons, without becoming hypoglycemic.

How is hypoglycemia related to the development of fatigue? As noted previously, blood glucose is in very short supply, so as it is being used during exercise it must be replenished from liver glycogen stores. A depletion of liver glycogen may lead to hypoglycemia during high-intensity aerobic exercise because gluconeogenesis normally cannot keep pace with glucose utilization by the muscles. Hypoglycemia is known to impair the functioning of the central nervous system and is often accompanied by acute feelings of www.mhhe.com/williams9

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GLUT T

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F I G U R E 4 . 1 0 Some of the effects of aerobic or endurance training upon skeletal muscle. Increases in glycogen (G) and triglyceride (T) provide a greater energy store, increased levels of GLUT-4 receptors (GLUT) provide the potential to increase glucose delivery to the muscle as needed, while the increase in mitochondria size and number (M), myoglobin content (My), oxidative enzymes (ox), and slow-twitch muscle fiber size facilitates the use of oxygen for production of energy.

dizziness, muscular weakness, and fatigue. The normal blood glucose level usually ranges from 80–100 mg of glucose per 100 ml of blood (4.4–5.5 mmol per liter). As this level gets progressively lower, hypoglycemic symptoms may develop. The point usually used to identify hypoglycemia during research studies with exercise is 45 mg per 100 ml, or 2.5 mmol per liter, although some investigators have used higher levels. Since hypoglycemia may disrupt functioning of the central nervous system (brain and spinal cord), the body attempts to maintain an optimal blood glucose level. Zierler noted that exercise increases muscle glucose uptake, in part due to increased cell membrane GLUT-4 receptors. Exercise may also increase the sensitivity to insulin, so more glucose is transported into the muscle for the same level of insulin. Thus, insulin levels normally drop during exercise so as to help maintain normal serum glucose. Other hormones—epinephrine (adrenaline), glucagon, 132

C H A P T E R 4 Carbohydrates: The Main Energy Food

and cortisol—also help maintain, and even increase, blood glucose levels during exercise. Epinephrine is secreted from the adrenal gland during exercise, particularly intense exercise, and stimulates the liver to release glucose; it also accelerates the use of glycogen in the muscle. However, during the early phases of exercise, liver glucose output may exceed muscle glucose uptake, which may result in hyperglycemia. Glucagon and cortisol levels generally increase during the stress of exercise, cortisol particularly during prolonged exercise. Glucagon is released from the pancreas and generally increases the rate of gluconeogenesis in the liver. Kjaer noted that liver gluconeogenesis may contribute substantially during prolonged aerobic exercise when liver glycogen levels decline and gluconeogenic substrate becomes more abundant. Cortisol is secreted from the adrenal gland and facilitates the breakdown and release of amino acids from muscle tissue to provide some substrate to the liver for gluco-

TABLE 4.6

Major hormones involved in regulation of blood glucose levels

Hormone

Gland

Stimulus

Action

Insulin

Pancreas

Increase in blood glucose

Helps transport glucose into cells; decreases blood glucose levels

Glucagon

Pancreas

Decrease in blood glucose; exercise stress

Promotes gluconeogenesis in liver; helps increase blood glucose levels

Epinephrine

Adrenal

Exercise stress; decrease in blood glucose

Promotes glycogen breakdown and glucose release from the liver; helps increase blood glucose levels

Cortisol

Adrenal

Exercise stress; decrease in blood glucose

Promotes breakdown of protein and resultant gluconeogenesis; helps increase blood glucose levels

neogenesis. Blood glucose normally increases during the initial stages of exercise and is normally well maintained by these hormonal mechanisms. A summary of hormonal actions in the regulation of blood glucose is presented in table 4.6. Hypoglycemia may be a concern of athletes in several situations. One possibility is a reactive hypoglycemia following the consumption of a high-carbohydrate meal 30–60 minutes or more prior to an athletic event. If hypoglycemia develops just prior to or during the early stages of the event, the effect could impair performance. This possibility will be covered later in this section. Hypoglycemia may also develop during prolonged exercise tasks, but it may be dependent upon the intensity level of the exercise. In low-intensity exercise, such as 30–50 percent of VO2 max, the primary fuel is fat, and hence the use of carbohydrate is minimized. Moreover, at this low intensity level, gluconeogenesis can help maintain blood glucose above hypoglycemic levels. During the early part of prolonged moderate- to high-intensity aerobic exercise, muscle glycogen is the major source of energy derived from carbohydrate, although some blood glucose is utilized. However, Weltan and others recently found that as muscle glycogen levels get low in the latter stages of an endurance task, the muscle increases its fat oxidation and blood glucose, derived from liver glycogen, now accounts for most of the muscular energy from carbohydrate. Gluconeogenesis is increased, but Hargreaves indicates that it cannot completely compensate for decreased liver glycogen availability. Thus, the blood glucose levels fall toward hypoglycemia. Whether hypoglycemia impairs physical performance may depend upon the individual. In a recent study, Utter and others reported that a lower rating of perceived exertion (RPE) during prolonged running was associated with higher blood glucose, suggesting that maintenance of optimal blood glucose levels could help prevent psychological distress. Some earlier research reported that exercise-induced hypoglycemia led to the expected symptoms, including dizziness and partial blackout. However, more contemporary research from three different laboratories has revealed that a number of subjects may become hypoglycemic during the latter stages of a prolonged exercise task to exhaustion at 60–75 percent of their VO2 max, and yet are able to continue exercising while hypoglycemic, even at levels as low as 25 mg per 100 ml. It appears that the role hypoglycemia plays in the etiology

of fatigue in prolonged exercise has not been totally elucidated, although there appears to be individual susceptibility. Nevertheless, it is well documented that with increased exercise duration there is a progressive decrease in muscle glycogen and a progressive increase in blood glucose uptake by the muscle. However, liver supplies of glycogen are limited, and thus blood glucose levels eventually fall. Prevention of hypoglycemia is one of the major objectives of carbohydrate consumption during prolonged exercise because every individual will eventually suffer ill effects when they reach their minimum blood glucose threshold.

How is lactic acid production related to fatigue? In review, as noted in chapter 3, lactic acid is an end product of anaerobic glycolysis. Anaerobic glycolysis represents the lactic acid energy system, found primarily in the type IIb white muscle fibers, but also the type IIa red fibers. Anaerobic glycolysis is increased at the onset of high-intensity exercise, such as 200- to 400-meter track events, as a means to rapidly replenish ATP for muscle contraction or for the rapid resynthesis of PCr. The process of aerobic glycolysis can also generate ATP, but it is too slow during high-intensity exercise. Thus, lactic acid, or lactate, is produced when the production of pyruvate from glycolysis exceeds the oxidative capacity of the mitochondria. Blood lactic acid (lactate) levels increase during high-intensity exercise and for years have been thought to be the cause of fatigue. However, Coyle notes that the lactate molecule per se does not cause fatigue, but rather that its accumulation in blood reflects a disturbance of muscle cell homeostasis. One factor that may disturb muscle cell homeostasis is an increased concentration of hydrogen ions, reflecting an increased acidity. In two recent reviews of muscular fatigue, Fitts and Hargreaves implicated the hydrogen ion as a causative factor during high-intensity exercise. Fitts noted that it is now generally thought that the component of fatigue correlated with lactate results from the effects of an increased free hydrogen ion rather than lactate or the undissociated lactic acid.The hydrogen ion and associated increased acidity could elicit fatigue by inhibiting a number of physiological processes in the muscle cell associated with contraction. As noted in chapter 13, sodium bicarbonate, a buffer of acidity in the muscle www.mhhe.com/williams9

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cell, may be an effective means to enhance performance in highintensity exercise tasks. The lactate produced during exercise is not a waste product. Lactate is a carbohydrate; one molecule of lactate contains about half the energy of one molecule of glucose. Years ago, George Brooks from the University of California at Berkeley, proposed the lactate shuttle, whereby the lactate produced during exercise in white muscle fibers would be shuttled to other tissues, such as the heart and red oxidative muscle fibers, where it could be oxidized for energy. Hashimoto and Brooks also hypothesize the lactate produced in the cell cytoplasm may be oxidized by mitochondria in the same cell. Research supports the lactate shuttle hypothesis and, as discussed later in this chapter, some sports scientists have actually tested lactate salt supplementation as a means to provide energy to enhance exercise performance.

How is low muscle glycogen related to the development of fatigue? Low muscle glycogen may impair both aerobic and anerobic exercise performance. Low Muscle Glycogen and Aerobic Exercise Muscle glycogen is the major energy source for prolonged, moderately high- to high-intensity aerobic exercise. Elite marathon runners can maintain a fast race pace primarily through oxidation of carbohydrate, primarily muscle glycogen, and to a lesser extent fatty acids stored in the muscle. Coyle indicates that exercise at 70 to 85 percent of VO2 max cannot be maintained without sufficient carbohydrate oxidation and thus the severe lowering of muscle glycogen, often coupled with hypoglycemia, results in the need to reduce exercise intensity to 40–60 percent of VO2 max. A number of studies have shown that physical exhaustion was correlated with very low muscle glycogen levels, but others have shown some glycogen remaining even though subjects were exhausted. Several mechanisms have been postulated to explain the development of fatigue even with some muscle glycogen remaining. • Location of glycogen. Costill has indicated that performance would be adversely affected only when muscle glycogen levels went below 40 mmol/kg of muscle tissue. It may be that complete depletion of muscle glycogen is not necessary for performance to suffer, for glycolysis may be impaired with lower glycogen levels or the glycogen in the muscle fiber may be located where it is not readily available for glycolysis. • Rate of energy production. Shulman and Rothman propose a model in which energy is supplied in milliseconds via glycogenolysis, and indicate that one possible mechanism for muscle fatigue is that at low, but nonzero glycogen concentrations, there is not enough glycogen to supply millisecond energy needs. In a related vein, Fitts notes that low levels of muscle glycogen may interfere with maintenance of optimal levels of Krebs cycle intermediates, which can reduce the rate of aerobic ATP production, and further notes that the metabolism of blood-borne sub134

C H A P T E R 4 Carbohydrates: The Main Energy Food

strates (blood glucose and FFA) is simply too slow to maintain heavy exercise intensities. • Muscle fiber type. The fatigue that develops may be related to the depletion of muscle glycogen from specific muscle fiber types. In prolonged exercise at 60–75 percent of VO2 max, Type I fibers (red, oxidative slow twitch) and Type IIa fibers (red, oxidativeglycolytic fast twitch) are recruited during the early stages of the task, but as muscle glycogen is depleted, the athlete must recruit Type IIb fibers (white, glycolytic fast twitch) to maintain the same pace. However, it takes more mental effort to recruit the Type IIb fibers, which will be more stressful to the athlete. Type IIb fibers also are more likely to produce lactic acid, increasing the acidity, which may increase the perceived stress of the exercise. In a recent study, Krustrup and others recently reported that glycogen depletion of the slow-twitch muscle fibers, necessitating recruitment of fast-twitch muscle fibers and increased energy demands, is a factor that may predispose to fatigue. • Use of fat for energy. As muscle glycogen becomes depleted in the slow-twitch muscle fibers, the muscle cell will rely more on fat as the primary energy source. Since fat is a less efficient fuel than carbohydrate, the pace will slow down. • Role of the brain. Signals sent from peripheral tissues to the brain may regulate energy metabolism. A low glycogen level in exercising muscle may be such a signal, and may invoke neural responses causing fatigue. Low Muscle Glycogen and Anaerobic Exercise Fatigue in very high-intensity, anaerobic-type exercise generally is attributed to the detrimental effects of the acidity in the muscle cell associated with lactic acid production. Research has now shown that maximal high-intensity exercise, lasting only about 60 seconds, is not impaired by a very low muscle glycogen concentration, approximately 30 mmol/kg muscle. However, it is possible that performance in such very high-intensity, short-term exercise tasks may be impaired with extremely low muscle glycogen in the fasttwitch muscle fibers. Moreover, with somewhat longer anaerobic tasks, approximating 3 minutes, one laboratory study reported a reduced performance in the time to exhaustion test after 4 days of a low-carbohydrate, high-fat diet when compared to a normal, mixed diet and a high-carbohydrate diet. Although muscle glycogen levels were not measured, a logical assumption is that they were lower on the low-carbohydrate diet. In addition, field research has suggested that slower overall sprint speed, such as in the latter parts of prolonged athletic contests like soccer and ice hockey, may be due to muscle glycogen depletion. Muscle biopsies of these athletes revealed very low glycogen levels, which were attributed not only to the strenuous exercise in the contest but also to the fact that these athletes were consuming diets low in carbohydrates. In support of these field studies, Balsom and others recently reported that low muscle glycogen levels impaired laboratory exercise performance in repeated bouts of very high-intensity intermittent exercise bouts, 6-second cycle ergometer performance followed by 30 seconds of rest. Krustrup and others reported that almost 50 percent of muscle fibers were completely

or almost empty of glycogen following a soccer game, and suggested slower sprint performance in the latter part of a game may be explained by low glycogen levels in individual muscle fibers. Also, low muscle glycogen stores may lead to a decrease in exercise intensity during training. Low muscle glycogen levels, because they are associated with premature fatigue, have been theorized to be a major cause of the overtraining syndrome in endurance athletes. However, in a recent review, Ann Snyder noted that cyclists who met the criteria of short-term overtraining maintained their muscle glycogen levels. Thus, she concluded that some other mechanism than reduced muscle glycogen levels must be responsible for the development of the overtraining syndrome. In summary, low levels of glycogen in the white, fast-twitch IIb muscle fibers may limit performance in intermittent, anaerobictype exercise tasks. Both hypoglycemia and low glycogen in the red muscle fiber types, most likely a combination of the two, may be contributing factors to fatigue in prolonged endurance exercise.

How are low endogenous carbohydrate levels related to the central fatigue hypothesis? As noted previously, hypoglycemia and low muscle glycogen levels may impair exercise performance, and one mechanism for each involves adverse effects on brain function. Collectively, they may contribute to central fatigue in a different way. In the latter stages of prolonged exercise bouts, low muscle glycogen, in combination with decreased blood glucose levels, will stimulate gluconeogenesis from muscle protein. In particular, branched-chain amino acids (BCAA) in the muscle will be catabolized to provide energy. Because BCAA release from the liver may be decreased or uptake by the muscle may increase, blood levels of BCAA decline. The central fatigue hypothesis during prolonged exercise suggests that this decline in blood BCAA may contribute to fatigue. In general, fatigue is hypothesized to occur when BCAA levels drop and the concentration of another amino acid—tryptophan—increases in its free form, or free tryptophan (fTRP). BCAA compete with fTRP for similar receptors that facilitate their entry into the brain, so high BCAA levels prevent brain uptake of fTRP. With an increased fTRP:BCAA ratio, entry of fTRP into the brain cells will be facilitated. Increased brain levels of tryptophan may stimulate the formation of serotonin, a neurotransmitter in the brain that may be related to fatigue sensations (see figure 4.11). Preventing the increase in the fTRP:BCAA ratio is theorized to prevent the premature development of fatigue, and the use of BCAA supplements in this regard will be covered in chapter 6. However, carbohydrate intake during exercise may also be helpful, as discussed later in this section.

Will eating carbohydrate immediately before or during an event improve physical performance? Because hypoglycemia or muscle glycogen depletion may be causes of fatigue during endurance exercise, supplementation with glucose or other forms of carbohydrate before or during exercise may be the-

Brain capillary

Nerve cell

Tryptophan Endothelial cells

A. BCAA

Brain capillary

increased serotonin production

Receptor

Nerve cell

Tryptophan

B. BCAA

Decreased serotonin production

F I G U R E 4 . 1 1 BCAA and the central fatigue hypothesis. (A) An increased level of serum free tryptophan (fTRP ) resulting in a high fTRP:BCAA ratio will bind to receptors in the capillary for transport to nerve cells and increased serotonin formation, which may be associated with central fatigue. (B) An increased level of BCAA( )will compete with the fTRP for receptors, blocking them from entering the nerve cell and decreasing production to serotonin, helping to prevent central fatigue.

orized to delay the onset of fatigue and improve performance. Thousands of studies have been conducted on this topic ever since carbohydrates were identified as the most efficient energy source for exercise over 80 years ago, and researchers’ interest in this topic remains unabated today. In recent years the research designs have usually been highly sophisticated as investigators have attempted to provide specific answers relative to the type, amount, and timing of carbohydrate ingestion before and during performance. Although some problems remain in providing quantitative data, the use of stable isotopes of ingested carbohydrates (referred to as exogenous carbohydrates in comparison to endogenous stores in the body) as detailed by Wolfe and George has enhanced our understanding of their metabolic fate when ingested prior to or during exercise. However, the reviewer attempting to synthesize the available research is confronted with a difficult task since the experimental designs varied considerably. The amount and type of carbohydrate ingested, the use of liquid or solid forms, the method of administration (oral ingestion or venous infusion), the time prior to or during the exercise that it was taken, the diet of the subject several days prior to the study, the amount of glycogen in the muscle and liver, the intensity and duration of the exercise, the type of exercise task (running, swimming, cycling, etc.), the fitness level of the subjects, the environmental temperature, and the method used to evaluate blood glucose and muscle glycogen utilization are some of the important differences between studies. Although the results from all of these studies were not similar, some general consistencies have evolved. The role of carbohydrate supplementation on exercise performance has been the www.mhhe.com/williams9

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subject of numerous reviews, and a number of contemporary reviews may be found in the reference list at the end of this chapter. Based on these reviews and an overall review of specific studies, the following generalizations appear to be logical. More specific information relative to practical recommendations is provided following this discussion. Initial Endogenous Stores If the individual has normal liver and muscle glycogen stores, glucose feedings are unnecessary for continuous moderately high-intensity exercise bouts lasting 60–90 minutes or less but may be beneficial for high-intensity exercise tasks of similar duration, as noted below. Since the body can store carbohydrate in the muscles and liver, the usefulness of glucose or other carbohydrate intake before or during exercise depends on the adequacy of those supplies already in the muscle and liver to meet energy needs. For competition, the muscle and liver glycogen stores should be adequate to meet carbohydrate energy needs. The critical point is to consume substantial amounts of carbohydrates a day or two prior to the event and to decrease the duration and intensity of training to assure ample endogenous glycogen supplies. The available research has shown that the consumption of glucose, fructose, sucrose, maltodextrin (a glucose polymer), or other carbohydrate combinations immediately prior to events of short or moderate duration has a negligible effect upon performance. Adding a gallon of gas to a full tank will not make a car go faster during a short ride. The same is true of sugar to a muscle already filled with glycogen. On the other hand, if muscle glycogen levels are low and the exercise task is somewhat prolonged, then ingestion of carbohydrate just prior to the exercise bout may improve performance. It is important to note, however, that in order to enhance performance, the exogenous carbohydrate source must be able to delay the onset of fatigue that might otherwise occur as a result of premature depletion of endogenous carbohydrate sources, a viewpoint also proposed by Tsintzas and Williams in a recent review. Exercise Intensity and Duration The potential beneficial effects of carbohydrate supplementation depend on the interaction of exercise intensity and duration, which of course are interrelated. The shorter the duration, the greater the exercise intensity can be. The following time frames are representative of those that have been studied to evaluate the effects of carbohydrate supplementation. A summary of the science-based recommendations for carbohydrate intake before, during, and after exercise or sport performance is presented in table 4.7. Very high-intensity exercise for less than 30 minutes Research suggests that carbohydrate supplementation will not enhance performance in high-intensity exercise bouts less than 30 minutes in length. For example, Palmer and others recently noted that consuming carbohydrate 10 minutes before competing in a 20-kilometer cycle time trial did not enhance performance in well-trained cyclists. Nevertheless, if carbohydrate supplements could ameliorate a muscle or liver glycogen deficiency, performance might improve. For example, Walberg-Rankin reported that carbohydrate supplementation improved high-intensity anaerobic exercise performance in wrestlers following a drastic weight reduction program with very

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limited carbohydrate intake. Presumably, the carbohydrate supplement, consumed in a 5-hour period before testing, increased muscle glycogen levels, particularly in fast-twitch fibers, enhancing carbohydrate utilization and subsequent performance. Very high-intensity resistance exercise training In a recent review, Conley and Stone noted that resistance, or strength, training, may use considerable amounts of muscle glycogen, which can lead to fatigue and strength loss. However, they noted that there are inadequate data to determine whether or not carbohydrate supplements increase performance if consumed before or during training. Subsequent to this review, Dalton and others reported that carbohydrate supplementation did not improve muscular endurance performance as evaluated by the number of repetitions of the bench press and leg extension at 80 percent of 10 repetition maximum, even under conditions of energy restriction. Moreover, Utter and others reported no significant effects of carbohydrate supplementation (sports drink) on ratings of perceived exertion during a 2-hour resistance training workout. High-intensity exercise for 30 to 90 minutes Normally, with adequate muscle and liver glycogen, carbohydrate supplements have not been found to improve exercise performance in this time frame. For example, two recent studies found that neither consumption of a 6 percent carbohydrate solution nor infusing glucose at the rate of 1 gram per minute improved performance in a one-hour maximal cycling protocol. Additionally, Burke and others reported no effect of a commercial gel supplying about 1.1 grams of carbohydrate per kilogram body weight on halfmarathon performance compared to the placebo. However, they cited twelve studies involving the effect of carbohydrate supplementation on performance in endurance tasks approximating one hour, and about half of the studies indicated improved performance. Moreover, some recent research has suggested that supplementation may benefit well-trained athletes who may be able to exercise at high intensity for about an hour. For example, Jeukendrup and el-Sayed, with their associates, recently reported that cyclists exercising for about an hour at high intensity significantly improved their performance following ingestion of a carbohydrate supplement, as compared to a placebo. Also, Ball and others reported that carbohydrate intake during a simulated time trial improved performance in a sprint at the end of 50 minutes of highintensity cycling. In such cases, it is possible that the ingested carbohydrates may help provide glucose to the fast-twitch muscle fibers or prevent premature depletion in the slow-twitch fibers. Jeukendrup hypothesizes that carbohydrate intake seems to positively affect the central nervous system during more intense exercise. Research from his laboratory, by Carter and others, found that simply swishing a carbohydrate (maltodextrin) solution in the mouth periodically during exercise enhanced performance in a 1-hour cycle time trial, an effect suggested to be due to increased central nervous system drive or motivation from carbohydrate receptors in the mouth. Intermittent high-intensity exercise for 60 to 90 minutes Research has shown that individuals engaged in endurance-type contests with intermittent bouts of sprinting, such as soccer, ice

TABLE 4.7

Some recommended guidelines for carbohydrate intake as a means to help optimize exercise/sport performance. Carbohydrate intake before and during exercise may help optimize performance, whereas carbohydrate intake after exercise may facilitate recovery for subsequent training or competition. In general, the lower the intensity and the shorter the duration of exercise, the less the need for additional carbohydrate. Recommendations are based on scientific studies. Physically active individuals should consume various types and amounts of carbohydrate before and during exercise and sport training to determine personal optimal dietary strategies. See the text for additional information and guidelines.

Exercise intensity/sport

Duration

Before exercise*

During exercise**

After exercise***

Very high-intensity aerobic (5K run)

< 30 minutes

None needed

None needed

None needed

High-intensity aerobic (10K run)

30–90 minutes

20–25 grams

30–60 grams

60–80 grams/hour for 3–4 hours

Intermittent high-intensity (Team sports, such as soccer)

60–90 minutes

20–25 grams

30–60 grams

60–80 grams/hour for 3–4 hours

Moderate- to high-intensity aerobic (half-marathon; marathon)

>90 minutes

20–50 grams Carbohydrate loading

60–80 grams/hour

60 grams/hour for 3–4 hours

Moderate-intensity aerobic

>6 hour

20–50 grams Carbohydrate loading

60–100 grams/hour

60–80 grams/hour for 3–4 hours

1–2 hours

None needed

None needed

60–80 grams/hour for 3–4 hours

(Ironman-distance triathlon; 140 miles; 226 kilometers) High-intensity resistance training (Lifting weights)

*Within 10–15 minutes of the start of exercise. All individuals should consume a pregame meal sometime between 1–4 hours prior to exercise in order to ensure normal muscle glycogen and blood glucose levels. Carbohydrate intake 3–4 hours before should average about 3–4 grams per kilogram body weight, but only 1–2 grams per kilogram body weight if consumed within 1–2 hours exercise. **Fluids such as sports drinks are recommended. Drinking about 8 ounces (240 milliliters) of a typical sport drink every 15 minutes will provide about 60 grams of carbohydrate per hour. ***For most athletes, consuming a diet with substantial amounts of healthful carbohydrates over the course of 24 hours will replace muscle glycogen levels to normal. For those who want a speedy recovery of muscle glycogen for subsequent intense training or competition the same or following day, using this rapid muscle glycogen replacement protocol may be recommended. Athletes may also benefit by consuming some protein with the carbohydrate, about 1 gram of protein for every 4 grams of carbohydrate.

hockey, or tennis, may benefit from carbohydrate supplements taken before and during the game. In a recent controlled laboratory protocol representative of a 60-minute intermittent, high-intensity competitive sport such as soccer or field hockey, Welsh and colleagues from Mark Davis’s laboratory reported that carbohydrate intake before and during the exercise task resulted in significant improvements in various tests of physical and mental functions performed throughout the experimental trial. Toward the end of the 60minute period, the carbohydrate trial resulted in faster 20-meter sprint time, longer time to fatigue in a shuttle run, enhanced whole body motor skills, and decreased self-reported perceptions of fatigue. The results suggested a beneficial role of carbohydrateelectrolyte ingestion on physical and mental functions during intermittent exercise similar to that of many competitive team sports. Similar findings were reported by Winnick and others. Other field research studies, although not universally supportive, have shown similar benefits of carbohydrate intake under game conditions. Several reviewers, such as Kirkendall and Kovacs, indicate carbohydrate intake before and during prolonged, intermittent high-intensity exercise sports may enhance performance. High- to moderate-intensity exercise greater than 90 minutes Research generally supports a beneficial effect of carbohydrate intake on exercise performance tasks greater than

90 minutes (if the exercise intensity is high enough), particularly so when the task is more prolonged, such as 2 hours or more. For example, Kimber and others reported a significant inverse correlation between the amount of carbohydrate consumed and the finishing time of male triathletes in an Ironman triathlon, suggesting that increasing carbohydrate consumption during such a prolonged event may enhance performance. Jeukendrup indicates that the performance benefits of carbohydrate ingestion are likely achieved by maintaining or raising plasma glucose concentrations to help sustain high rates of carbohydrate oxidation. Timing of Carbohydrate Intake Athletes may consume diets rich in carbohydrate for several days prior to competition, as discussed later under carbohydrate loading. Most of the studies evaluating the effect of carbohydrate supplements on subsequent exercise performance have used time frames ranging from 4 hours prior to immediately prior to the task, and at various times during the exercise task. Athletes should experiment in training with several of the carbohydrate-intake strategies presented below and find that which works best. For prolonged endurance events, carbohydrate intake several hours before, immediately before, and during the event may be recommended.

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Four hours or less before exercise Carbohydrate intake 60–240 minutes prior to prolonged exercise tasks (longer than 90 minutes) may enhance performance. Research has demonstrated improved performance when adequate carbohydrate was consumed either 1, 3, or 4 hours prior to a prolonged exercise task involving simulated racing conditions during the latter stage. Other research revealed no significant differences in 30-kilometer run performance when equal amounts of carbohydrate were supplemented either 4 hours before or during the run, suggesting the ingested carbohydrate was available for energy production using either strategy. Less than 1 hour before exercise Although one prominent early study suggested that consuming simple carbohydrates less than an hour before exercise may impair subsequent performance by several means, Zierath and others contend that finding is the exception rather than the rule as many subsequent studies have shown the benefits of pre-exercise carbohydrate intake. Prudence suggests that individuals who may be prone to reactive hypoglycemia should avoid carbohydrate intake, particularly highglycemic-index foods, 15–60 minutes prior to performance. Simple sugars ingested within this time frame may actually impair physical performance in such individuals because of the adverse effects of reactive hypoglycemia, such as muscular weakness. Moreover, this same insulin response may speed up muscle glycogen utilization. This may be a disadvantage to the marathoner, whose glycogen levels may be depleted too early in the race. Several earlier studies showed that run time to exhaustion was shorter by about 20–25 percent after athletes consumed 2–3 ounces of glucose within an hour before the endurance test. However, not all individuals experience reactive hypoglycemia. Kuipers and others noted that about one-third of welltrained subjects experienced hypoglycemia following the ingestion of 50 grams of glucose after a 4-hour fast. However, the hypoglycemia was transient as blood glucose levels returned to normal after 20 minutes of exercise at 60 percent VO2 max. No performance data were measured. In a study by John Seifert and others, subjects were given various carbohydrate solutions to raise their insulin levels; when their insulin levels peaked, they undertook an exercise task at 60 percent of VO2 max for 50 minutes. No hypoglycemia developed, nor were there any adverse sensory or psychological responses. Other well-controlled studies have reported no adverse effects of glucose, fructose, or maltodextrin ingestion 30–45 minutes prior to prolonged exercise. Compared to placebo conditions with artificially sweetened water, the various carbohydrate solutions elicited no significant differences in muscle glycogen utilization or exercise capacity when subjects were exercising at 55–75 percent of VO2 max. For individuals not prone to reactive hypoglycemia, the consumption of carbohydrates within 15–60 minutes prior to performance may confer some benefits. Possible increases in liver and muscle glycogen may offset the reported increase in muscle glycogen utilization. Immediately before exercise As noted previously, consuming carbohydrate immediately before exercise of short duration, and even exercise tasks less than 90 minutes or so, normally will not enhance performance. For example, Marjerrison and others 138

C H A P T E R 4 Carbohydrates: The Main Energy Food

found that the ingestion of a carbohydrate solution 30 minutes before undertaking four 30-second anaerobic Wingate tests had no effect on power output, while Smith and others reported no significant effect on swim time performance of ingesting a 10-percent glucose solution 5 minutes before a 4-kilometer swim of approximately 70 minutes. However, carbohydrate intake immediately prior to (within 5–10 minutes) prolonged endurance exercise tasks of 2 hours or more may help delay the development of fatigue and improve performance if the athlete is exercising at a level greater than 50 percent VO2 max, such as 60–75 percent. The majority of the studies, including controlled laboratory investigations and field research involving different types of endurance athletes, support this point of view. At this level of exercise intensity, the insulin response to glucose ingestion is suppressed; in addition, the secretion of epinephrine is increased. These two hormonal responses interact to help maintain or elevate the blood glucose level and prevent the hypoglycemic response that typically may occur in reactive individuals if more time elapses between the ingestion of the carbohydrate and the initiation of exercise. During exercise Carbohydrate ingested during prolonged exercise can help maintain blood glucose levels and reduce the psychological perception of effort, as measured by the ratings of perceived exertion, during the latter stages of an endurance task. As the exercise task continues and the muscle glycogen level falls, the amount of energy derived from the ingested carbohydrates increases. Most research supports the benefits of consuming carbohydrates early in and throughout the exercise task, but even a single carbohydrate feeding late in a prolonged exercise bout may help replenish blood glucose levels, increase carbohydrate oxidation, and delay fatigue. All major investigators who have published extensive reviews, most recently Mark Hargreaves and Asker Jeukendrup, conclude that carbohydrate intake during prolonged exercise, when contrasted with placebo conditions, will enhance performance. This general finding is supported by both laboratory and field studies and applies to both females and males. Use of the Ingested Carbohydrate Using labeled carbohydrate sources and analyzing the expired carbon dioxide for radioactivity, investigators have shown that some of the ingested, or exogenous, carbohydrate may be used as an energy source within 5–10 minutes, indicating that it may empty rapidly from the stomach, be absorbed from the small intestine into the blood, and enter into metabolic pathways. Peak use of exogenous carbohydrate appears to occur 75 to 90 minutes after ingestion. A number of studies have shown that the ingested carbohydrate may contribute a significant percentage of the carbohydrate energy source during exercise, ranging from 20–40 percent in some studies, but as much as 60–70 percent during the latter stages of exercise when endogenous liver and muscle glycogen stores become depleted. Possible Fatigue-Delaying Mechanisms The precise mechanism whereby glucose ingestion helps delay the onset of fatigue during moderate- to high-intensity exercise (i.e., > 65 percent VO2 max) has not been totally elucidated, but several theories have been studied.

Maintenance of blood glucose levels The available data suggest that the ability of carbohydrate intake to delay fatigue may be related to the maintenance of higher blood glucose levels, possibly by sparing liver glycogen until late in the exercise, and the prevention of hypoglycemia in susceptible individuals; blood glucose would be available to enter the muscle and provide a source of energy for aerobic glycolysis, and may also provide glucose to the brain to prevent premature central fatigue. As noted, exogenous glucose is used increasingly as the exercise task becomes prolonged. Reduction of psychological effort Some research has shown that glucose ingestion could make an endurance task psychologically easier and suggested that the physiological effects of the glucose, either in the brain or in the muscles, reduced the stressful effects of exercise. Several studies by Utter and others found that carbohydrate ingestion reduced the ratings of perceived exertion during prolonged running and cycling. For example, they reported that marathoners ingesting carbohydrate compared to placebo beverages were able to run at a higher intensity during a competitive marathon, and yet the ratings of perceived exertion (RPE) were similar in both groups of runners, suggesting the carbohydrate may have permitted them to run at a faster rate with similar psychological effort. However, it has not been determined whether these ergogenic effects may be attributed to the effect of glucose as a source of energy in the muscle or to its effect on the central nervous system, either as a direct energy source for brain metabolism or through its effect on BCAA levels. In several recent studies carbohydrate supplementation during exercise has been reported to prevent the decrease in serum BCAA during the later stages of prolonged exercise, possibly by mitigating secretion of cortisol. According to the central fatigue hypothesis, preventing an increase in the fTRP:BCAA ratio would deter the onset of mental fatigue. Sparing of muscle glycogen Although sparing of muscle glycogen could be another benefit of carbohydrate ingestion before or during moderate- to high-intensity exercise, research findings are equivocal. In a unique experiment from the University of Texas, subjects received venous glucose infusions to maintain a hyperglycemic state during 2 hours of exercise at 73 percent of VO2 max, but the net rate of muscle glycogen utilization was not affected compared to control conditions. Arkinstall and Chryssanthopoulos and their colleagues also noted no muscle glycogen sparing effect with carbohydrate supplementation during the exercise task. On the other hand, Yaspelkis and others, also from the University of Texas, noted that during low-intensity exercise (i.e., < 50 percent VO2 max) or during low- to moderate-intensity exercise tasks, carbohydrate supplementation during exercise could spare use of muscle glycogen in slow-twitch muscle fibers and enhance performance. They noted that during low-intensity exercise the serum levels of both glucose and insulin were elevated, which could promote muscle use of serum glucose and sparing of muscle glycogen. Bosch and others, as well as Tsintzas and others, recently reported that carbohydrate intake during prolonged exercise at about 70 percent VO2 max did spare muscle glycogen use,

and the Tsintzas group reported the sparing effect occurred in the Type I, slow-twitch muscle fibers, but not in the Type II fasttwitch fibers. Williams noted that although other reviewers concluded that consuming carbohydrate during exercise did not spare use of muscle glycogen in cyclists, research findings from his laboratory did find glycogen sparing in runners who consumed carbohydrate drinks throughout prolonged exercise, and the glycogen sparing occurred early in the exercise task. Hargreaves noted also that the breakdown of muscle glycogen may be slowed because the supply of blood glucose is improved when carbohydrate is consumed. Limitations to Prevent Fatigue Although glucose ingestion may help delay fatigue during moderately high-intensity exercise, it cannot totally prevent the onset of fatigue. It appears that a maximum of about 1.5 to 1.7 grams of the ingested carbohydrate may be available each minute, which is much lower than the required energy needs at 65–85 percent of VO2 max. Jeukendrup and Jentjens indicate the intestines and liver may be limiting factors, the intestines being unable to absorb the ingested carbohydrate at a faster rate while the liver may limit the amount of glucose released into the blood. When blood glucose, BCAA, and/or muscle glycogen levels are eventually reduced to a critical level, fatigue occurs. Optimal Supplementation Protocol Several studies have indicated that although the intake of carbohydrate either before or during exercise may separately enhance performance, the best effect was observed when carbohydrate was consumed both before and during exercise. For example, Chryssanthopoulos and others had subjects run to exhaustion at 70 percent VO2 max and found that although a high-carbohydrate meal 3 hours prior to performance improved endurance time, the combination of the meal and a carbohydrate-electrolyte solution during exercise further improved endurance running capacity.

When, how much, and in what form should carbohydrates be consumed before or during exercise? The most common athletic events or physical performance activities that may benefit from carbohydrate feedings are those associated with long duration (90–120 minutes or more) at moderate- to highintensity levels. Marathon running, cross-country skiing, and endurance cycling are common sports of this kind. Other sports that require intermittent bouts of intensive activity over a prolonged period, such as soccer, may also benefit. However, the individual participating in these activities, particularly under warm or hot environmental conditions, also needs to replenish fluid losses incurred through sweating. In such cases, fluid replenishment is more critical than carbohydrate. The topic of fluid replacement during exercise is covered in more detail in chapter 9, but since carbohydrate is one of the contents in the majority of the sport drinks developed as fluid replacements for athletes, its role is discussed briefly here. Many studies have been conducted in recent years to determine the best carbohydrate feeding regimen to prevent fatigue during www.mhhe.com/williams9

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prolonged exercise. A number of different variables have been studied, such as the timing of the feeding and the type, amount, and concentration of carbohydrate. Again, based on current reviews by the primary investigators regarding carbohydrate supplementation for exercise performance and a careful analysis of individual studies, the following points represent the general conclusions and recommendations for individuals who may be exercising at 60–80 percent of their VO2 max or greater for 1–2 hours or longer. These points may also be applicable to athletes engaged in intermittent high-intensity exercise sports that last an hour or more. But remember, individuals may have varied reactions to carbohydrate intake, so athletes should experiment in training before using these recommendations in actual competition. Pre-exercise:When and How Much? The amount of carbohydrate ingested 4 hours prior to performance should be based upon body weight. Several studies have used 4–5 grams/kg (1.8–2.3 grams/pound) with good results. For an athlete who weighs 60 kg (132 pounds), the recommended amount would be 240–300 grams. The carbohydrates could be consumed in any of several forms, including fluids such as juices or glucose polymer solutions, or solid carbohydrates such as fruits or starches. The fiber content should be minimized to prevent possible intestinal problems during exercise. Keep in mind that 300 grams of carbohydrate is about 1,200 Calories, a somewhat substantial meal. You may consult appendix E for an expanded list of foods high in carbohydrate. Table 4.8 presents a quick estimate of carbohydrates in the various food exchanges and sports products. The guidelines presented on pages 76–77 relative to precompetition meals provide appropriate guidelines. If carbohydrate is consumed approximately 1 hour prior to performance, about 1–2 grams/kg (60–120 grams for a 60-kg athlete) may be recommended, for these levels have been shown to enhance performance in several studies. One study using only 12 grams 1 hour prior to performance has shown no beneficial effect. Both glucose polymers and foods with a low glycemic index have been used successfully. If carbohydrates are consumed immediately before exercise, that is, within 10 minutes of the start, about 50–60 grams of a glucose polymer in a 40–50 percent solution has been used effectively in some studies. Dry glucose polymers are available commercially. One tablespoon is about 15 grams. To make a 50 percent solution containing 50 grams of the polymer, put about 3 level tablespoons of the polymer into 100 milliliters (about 3–4 ounces) of water. To make a 7.5 percent solution containing 15 grams, put 1 tablespoon of the polymer into 200 milliliters (about 7 ounces) of water. As noted in table 4.8, several commercial “energy” drinks contain 25–50 grams of carbohydrate per 8 fluid ounces, which are about 10–20 percent solutions. During Exercise: When and How Much? During exercise, feedings every 15–20 minutes appear to be a reasonable schedule, but possibly more frequently when attempting to maximize carbo-

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C H A P T E R 4 Carbohydrates: The Main Energy Food

TABLE 4.8

Grams of carbohydrate in selected food exchanges and sports products

1 fruit exchange = 15 grams carbohydrate 1 apple 1 orange 1/2 banana 4 ounces orange juice 1 starch exchange = 15 grams carbohydrate 1 slice bread 1/2 cup cereal 1/4 large bagel 1/2 cup cooked pasta 1 small baked potato Sports drinks: 7–8 ounces = 15 grams carbohydrate Gatorade PowerAde SportAde Sports bars = 20–50 grams carbohydrate 1 PR Bar 1 Power Bar Sports gels = 20–30 grams carbohydrate 1 Power Gel packet 1 ReLode packet Energy Drinks: 8 ounces = 25–50 grams carbohydrate Gatorade Energy Drink SoBe Energy

hydrate intake or to obtain fluids when exercising under warm or hot environmental conditions. Although you may consume considerable quantities of carbohydrate during exercise, your ability to use this exogenous source for energy is limited. The reason is not known, but as noted previously may be related to insufficient intestinal absorption or impaired delivery from the liver. In the past, reasonable evidence-based estimates suggested that athletes could use approximately 0.5–1 gram of ingested carbohydrate per minute, or about 30–60 grams of carbohydrate per hour. In general, research indicates that equally trained males and females can oxidize equivalent amounts of ingested carbohydrate. More recently, studies have shown that ingesting various combinations of carbohydrates could increase this amount to 1.2–1.7 grams per minute, or about 72–102 grams per hour. The rationale is presented in the next section. Sports drinks averaging 6–10 percent carbohydrate have been found to enhance prolonged endurance performance. A typical serving of a sport drink (8 ounces) would contain about 14–24 grams of carbohydrate, so depending on the concentration, an athlete who wanted to maximize utilizable carbohydrate intake would need to drink about 32–56 ounces to obtain about 100 grams of carbohydrate per hour. Drinking 8 ounces every 15 minutes would provide 32 ounces (1 quart) over the course of an hour, but consumption would need to be more frequent to obtain 56 ounces. Consuming 56 ounces of fluid over the course of an hour might be difficult, and may pose a potential health risk for some individuals. Although the fluids could provide the desired amount of car-

bohydrate, excessive fluid consumption could lead to overhydration and a serious medical condition known as hyponatremia, as shall be discussed in chapter 9. Several other protocols have been effective. One involved consumption of a high concentration (about 1 gram carbohydrate/kg body weight) immediately before or during the first 20 minutes of the exercise, and then use lower concentrations such as found in commercial sports drinks at regular intervals. Other investigators have noted that taking a single more concentrated dose of carbohydrate, such as 100–200 grams total, in the latter stages of prolonged exercise may be beneficial. Additionally, because of the nature of their sport, soccer players and other such athletes may need to consume a high concentration before the game and during halftime, or breaks in the game as they occur. It should be noted that consumption of carbohydrate solutions above 10 percent during exercise may cause gastrointestinal distress, as may other high concentrations of simple carbohydrates. However, some athletes may learn to tolerate larger concentrations, such as 15–20 percent. Ultradistance athletes, who exercise at a lower intensity, may tolerate even higher concentrations ranging from 20–50 percent. Although athletes may learn to tolerate higher amounts of carbohydrate intake during exercise, Asker Jeukendrup, an authority on carbohydrate use during exercise, has recently recommended the following, which are less likely to cause gastrointestinal disturbances: • Maximal exercise lasting less than 45 minutes • Maximal exercise lasting about 45–60 minutes • Team sports lasting about 90 minutes • Submaximal exercise lasting more than 2 hours • Near-maximal and maximal exercise lasting more than 2 hours • Ultraendurance events

None required Less than 30 grams/ hour Up to 50 grams/hour Up to 60 grams/ hour Up to 50–70 grams/ hour 60–90 grams/ hour

Type of Carbohydrate A number of different types of carbohydrates have been studied, including glucose, fructose, galactose, sucrose, maltose, glucose polymers such as maltodextrins, both individually and in various combinations, as well as soluble starch (a very long polymer), high-glycemic-index foods like potatoes, and low-glycemic-index foods such as legumes. In general, there appears to be no difference between these different types of carbohydrates as a means to enhance endurance performance when used appropriately. However, there may be some important considerations relative to the use of various carbohydrate combinations, fructose, solid carbohydrates, and lowglycemic-index foods. Carbohydrate combinations Jeukendrup noted studies have shown that a single carbohydrate ingested during exercise will be oxidized at rates up to about 1 gram/minute, even when large amounts of carbohydrate are ingested. However, combinations of

Lumen of small intestine

Small intestine epithelial cell

Interstitial Capillary fluid

Facilitated diffusion Fructose

Fructose

Secondary active transport

Absorption Na⫹ Glucose

Glucose

Na⫹ Galactose

Galactose

F I G U R E 4 . 1 2 The villi in the intestines contain different receptors for the monosaccharides, which may increase carbohydrate absorption when multiple sources of carbohydrate are ingested.

carbohydrate, particularly glucose and fructose, that use different intestinal transporters for absorption have been shown to result in higher oxidation rates (see figure 4.12) This seems to be the way to increase exogenous carbohydrate oxidation rates, up to 1.7 grams/ minute. Combinations of carbohydrates are recommended to increase glucose oxidation at a rate of more than 60 grams per hour. Currell and Jeukendrup reported that ingestion of a drink containing multiple carbohydrates (glucose and fructose), as compared to either a glucose drink or water, improved performance by 8 and 19 percent, respectively, in time trial performance following a 2-hour bout of cycling. Power output was greater throughout the approximate onehour time trial with the glucose/fructose drink. Single sources of carbohydrate, such as glucose, appear to be adequate when less is needed. As noted later in this chapter, lactate has also been incorporated into a sports drink and preliminary research suggests a potential ergogenic effect. Thus, check food labels for ingredients to ensure obtaining a sports drink containing such combinations. Fructose Fructose has been theorized to be a better source of carbohydrate than glucose because it is absorbed more slowly from the intestine and hence will not create an insulin response and the potential reactive hypoglycemia. Indeed, research has shown that fructose, compared to glucose, may lead to a more stable blood sugar during the early stages of prolonged exercise when ingested 45 minutes prior to the activity, for most ingested fructose is eventually converted to glucose in the liver. However, when fructose is ingested immediately before or during exercise, its effect on the blood sugar and carbohydrate metabolism appears to be little different than that of glucose. Most people can tolerate small amounts of fructose. It is found naturally in fruits, and is an ingredient in some sports drinks.

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However, consuming larger amounts may pose problems. Since fructose is absorbed slowly from the intestinal tract, it can create a significant osmotic effect in the intestines leading to diarrhea and gastrointestinal distress in some individuals. Research has indicated that a 6 percent solution of fructose, when compared to similar solutions of glucose and sucrose, caused significant gastrointestinal distress and an impairment in exercise performance. The athlete should be cautious in using fructose as the sole source of carbohydrate before or during exercise. Sports drinks containing fructose do so in small concentrations. Additionally, high-fructose corn syrup, although rich in fructose, is treated as an added sugar. The health risks of added sugars are covered later in this chapter. Solid and liquid carbohydrates In her review, Ellen Coleman noted that solid and liquid forms of carbohydrate were equally effective in maintaining blood glucose levels and enhancing exercise performance. Robergs and others recently confirmed this viewpoint, finding that the ingestion of a solid food containing carbohydrate, protein, and fat with added water produced similar blood glucose, metabolic, and exercise performance responses to those seen with the ingestion of liquid carbohydrate. However, Peters and others noted that triathletes who consumed a liquid form of carbohydrates performed better on a 3-hour cycling-running exercise task when compared to both a placebo trial and a trial in which the triathletes consumed isocaloric semi-solid carbohydrate foods (orange juice, white bread, marmalade, and bananas). The authors did note that the athletes may have had a negative perception toward eating solid foods during performance, which could have adversely affected their performance in that trial. On the other hand, concentrated forms of carbohydrate, as found in products marketed to endurance athletes, appear to provide similar benefits. Campbell and others studied the effect of different forms of carbohydrate (liquid, gel, and jellybeans) on endurance exercise performance and found that all carbohydrate-supplement forms were equally effective in maintaining blood glucose levels during exercise and improving exercise performance compared to water only. Although the effects of consuming equivalent amounts of carbohydrate in either liquid or solid form would appear to be minimal (providing adequate fluid intake in each case), more research is desirable to explore this issue, particularly with ultraendurance performance events where many athletes may consume both liquid and solid carbohydrate sources. Low-glycemic-index foods In a review, Guezennec indicated that a low-glycemic-index meal, such as lentils, consumed prior to prolonged exercise might provide an advantage over a highglycemic-index meal, such as potatoes. The underlying mechanism might be a slower rate of absorption resulting in a blunted insulin response and maintenance of higher blood glucose levels during prolonged exercise, an effect associated with soluble fiber. Guezennec indicated some preliminary research showed improved performance with low-glycemic-index foods, but recommended verification of these findings. Subsequent research suggested that there are no differences between low-glycemic-index and high-glycemic-index meals relative to their effects on performance. Febbraio and Stewart provided 142

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either a low-glycemic-index meal, a high-glycemic-index meal, or a control meal to trained individuals before cycling at 70 percent VO2 max for 2 hours followed by a 15-minute performance ride. Although the high-glycemic-index food increased blood glucose levels and depressed free fatty acid levels during the early stages, there were no differences later in the exercise task and no effects on the rate of muscle glycogen use or exercise performance. Several other well-controlled studies from Febbraio’s laboratory, using similar glycemic-index meal and exercise protocols, reported no significant differences between the meals and performance. Other studies support this viewpoint. Most recently, Erith and others reported no significant differences between diets of different glycemic indices on performance following overnight recovery. Semi-professional soccer players performed a fatiguing intermittent high-intensity shuttle run test, and during the succeeding day interval consumed either a high-glycemic-index diet (GI = 70) or a low-glycemicindex diet (GI = 35). No differences were noted between trials for performance or rate of fatigue as measured by the test. Earnest and others also found no differences between a high GI and low GI diet on performance in a 64-kilometer cycling time trial. Chen and others compared the effects of preexercise meals with different glycemic indices and glycemic loads on performance in an exercise test involving running for 60 minutes at 70 percent VO2 max followed by a 10-kilometer performance run. Although the high- and low-glycemic meals modified carbohydrate and fat oxidation somewhat, there was no effect on 10-kilometer time. Conversely, recent preliminary research from Clyde Williams’s laboratory at the University of Loughborough has suggested some beneficial effects of a low-GI diet on endurance exercise performance. Several well-controlled studies by Stevenson and others compared the effects of a high- and low-GI diet on substrate utilization during exercise at 65 to 70 percent of VO2 max, and reported a higher rate of fat oxidation following the low-GI meal. In one of these studies, run time to exhaustion at 70 percent of VO2 max was greater following the low-GI diet. In another study, Wu and Williams also reported higher rates of fat oxidation and a greater run to exhaustion at 70 percent of VO2 max following a low-GI meal (GI = 37) as compared to a high-GI meal (GI = 77). They speculated that the enhanced oxidation of fats may have optimized carbohydrate metabolism in some way to enhance performance. Given the conflicting data, additional research is needed to evaluate the effect of a low-GI diet on endurance exercise performance. Carbohydrate with protein Several studies have compared the effects of carbohydrate supplementation alone to carbohydrate/ protein supplementation on performance following recovery from previous exercise. In general, recent research indicates that adding protein to carbohydrate does not enhance endurance exercise performance. For example, although Berardi and others found that a carbohydrate/protein combination increased muscle glycogen levels more so than carbohydrate alone, there was no beneficial effect on a subsequent cycling test. Betts and others had subjects complete a 90-minute run at 70 percent of VO2 max, followed by a 4-hour recovery period during which they consumed either a carbohydrate or a carbohydrate/protein mixture. The subjects then ran to exhaustion at 85 percent of VO2 max, but there was no difference between

treatments. Romano-Ely and others investigated the effect of a carbohydrate-protein-antioxidant drink, as compared to an isocaloric carbohydrate drink, on cycling time to exhaustion at 70 percent VO2 max and, 24 hours later, at 80 percent VO2 max. The drinks were consumed every 15 minutes during exercise and immediately afterwards. There were no significant differences between the treatments on performance time during either of the cycling tests. Millard-Stafford and others also reported no differences between carbohydrate and carbohydrate/protein supplementation, provided during a 22-hour recovery period following an exhaustive running protocol, on subsequent 5-kilometer track time trial performance. Individuality Probably the most important recommendation is for the athlete to experiment with different types and amounts of carbohydrate during training before using them in competition. Just as it is important for you to know your optimal race pace for an endurance event, so too must you know how well you can tolerate different amounts and concentrations and types of carbohydrates. Williams noted that the type of event may influence the amount of carbohydrate ingested, as runners may be more prone to gastrointestinal distress than cyclists. “Runner’s trots” is a form of diarrhea which may be associated with excess consumption of highly concentrated sugar solutions, such as “energy” drinks. Just as you train your muscles to learn their capacity, you may also be able to train your digestive system to know its limits. During training, experiment with various types and concentrations of carbohydrate, both before and during exercise. Ron Maughan, an internationally respected authority in sport nutrition, indicated that the optimal strategy relative to carbohydrate utilization is to use your own subjective experience, which you can gain during training.

What is the importance of carbohydrate replenishment after prolonged exercise? There are several possible applications of this question. One is the athlete who may be involved in a prolonged exercise bout, have a rest period of 1–4 hours, and then must exercise again, such as athletes who train two or three times daily. Benefits may accrue to anaerobic endurance-, aerobic endurance-, and resistance-trained individuals. A second application is the athlete who trains intensely every day and must have an adequate recovery in the one-day rest interval. A third application, covered in the next section, is the technique of carbohydrate loading. After prolonged exercise, increased levels of GLUT-4 receptors in the muscle cell membrane help move available blood glucose into the muscle for resynthesis to muscle glycogen. Several studies have shown that ingesting carbohydrate during the rest interval between two prolonged exercise bouts improves performance in the second bout. This finding is comparable to the beneficial effects of carbohydrate intake during prolonged exercise bouts. The carbohydrate can help restore blood glucose levels but may also be used to resynthesize muscle glycogen. In cases such as this, where the rate of muscle glycogen resynthesis is important, high-glycemic-index foods such as potatoes, bread, glucose, or glucose polymers would be the preferred source of carbohydrate,

for they apparently lead to a faster restoration of muscle glycogen than does a meal rich in low-glycemic-index foods. For repeat prolonged exercise tasks with about a 4-hour interval, a general recommendation is to consume 1 gram of carbohydrate per kilogram body weight immediately after the first event and again 2 hours prior to the second event. Additional carbohydrate may also be consumed immediately before and during the second event. Carbohydrate with protein Carbohydrate has been combined with other nutrients, particularly protein, in attempts to enhance muscle glycogen resynthesis. Protein and some amino acids, such as arginine, may stimulate the release of insulin which, if added to the effects of carbohydrate-mediated insulin release, could increase the rate at which glucose is transported into the muscle cell. Some earlier studies found that consuming a protein/carbohydrate mixture after exercise would promote glycogen resynthesis more effectively compared to carbohydrate alone. However, these studies simply added protein to the standard amount of carbohydrate provided, and thus provided more total energy. Other studies, such as those by Jentjens, Rotman, van Loon, and their associates, have shown that although adding protein and amino acids to a carbohydrate solution may increase muscle glycogen synthesis after exercise compared to the carbohydrate alone, adding an equivalent amount of carbohydrate for the protein will elicit the same results. However, Berardi and others recently found that following a 60-minute cycling time trial, supplementation with a carbohydrate/ protein solution, as compared to an equal caloric carbohydrate supplement, resulted in an almost 30 percent increase in muscle glycogen. Several recent studies, such as those by Millard-Stafford and Romano-Ely and their colleagues, have shown that carbohydrate/ protein supplementation may also reduce the incidence of muscle soreness following exercise, including lower levels of serum enzymes used as markers of muscle tissue damage. Moreover, as shall be noted in chapter 6, consuming some additional protein following strenuous exercise may have some beneficial effects, such as improved muscle protein balance. John Ivy, an international scholar on carbohydrate metabolism, recently reviewed dietary strategies to promote glycogen synthesis after exercise. He indicated that supplementing at 30-minute intervals at a rate of 1.2–1.5 grams of carbohydrate per kilogram body mass per hour appears to maximize synthesis for a period of 4–5 hours post exercise. Consuming carbohydrate early after completion of exercise may facilitate glycogen synthesis, possibly because of an exercise-induced insulin-like action. Ivy further notes that if a lighter carbohydrate supplement is desired, protein and certain amino acids may be used in place of some of the carbohydrates. A ratio of 3 or 4 grams of carbohydrate for each gram of protein is one recommended protocol; some commercial products that combine high amounts of carbohydrate and protein are available. For example, a PowerBar contains about 40 grams of carbohydrate and 10 grams of protein, but similar amounts may be obtained from natural foods, such as a turkey breast sandwich on a large whole wheat bagel. If rapid resynthesis of muscle glycogen is not important, it is good to note that studies have shown consumption of adequate amounts of carbohydrate over a 24-hour period will restore muscle glycogen www.mhhe.com/williams9

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levels to normal. For athletes who train intensely on a daily basis with either resistive or aerobic exercise that leads to muscle glycogen depletion, sport nutritionists normally recommend that approximately 8–10 grams of carbohydrate per kilogram body weight should be consumed daily in order to restore muscle glycogen levels to normal. For an individual who weighs 70 kilograms, this approximates 560–700 grams of carbohydrate, or 2,240–2,800 carbohydrate Calories. This amount of carbohydrate would represent about 65–80 percent of the daily caloric intake of an athlete consuming 3,500 Calories. Over the 24-hour period, the rate of muscle glycogen recovery is approximately 5–7 percent per hour. Sports drinks may be a convenient means to consume carbohydrate immediately after exercise. The remaining carbohydrate should be derived from other natural sources in the diet, including both simple carbohydrates in fruits and complex carbohydrates in grains, potatoes, and other foods with adequate dietary fiber and other nutrients. The inclusion of high-glycemic-index foods in the daily diet will help speed resynthesis of muscle glycogen over the 24-hour period, and may be very compatible with the Prudent Healthy Diet. Regular meals consumed during the 24-hour recovery period should include healthful low-glycemic-index foods with adequate amounts of protein. Following prolonged, high-intensity competitive exercise performance, such as running a marathon, the resulting muscle damage will limit muscle glycogen replenishment for several days. Rest is important during this time, and muscle glycogen levels may return to normal following seven or more days of high-carbohydrate meals.

Will a high-carbohydrate diet enhance my daily exercise training? Most scientists and sport nutritionists who study carbohydrate metabolism in athletes recommend a high-carbohydrate diet for most athletes, particularly endurance athletes, because success in athletic competition is contingent upon optimal training, and for the endurance athlete, optimal training may be contingent upon adequate nutrition, primarily the ingestion of sufficient carbohydrate every day. In a recent review Louise Burke, a prominent sports nutritionist, and her associates recommended that athletes in general training should consume daily approximately 5–7 grams of carbohydrate per kilogram body weight, but endurance athletes should consume about 7–10 grams per kilogram. These recommendations are comparable to those of Melinda Manore, another sport nutrition expert. Burke and others noted that most male athletes may be meeting these needs, but many female endurance athletes, particularly those attempting to lose weight for competition, may not. Older athletes may need to ensure adequate carbohydrate intake during training. According to Mittendorfer and Klein, aging causes a shift in energy substrate use during exercise with an increased oxidation of glucose and less fat, presumably caused by age-related changes in skeletal muscle. There are some limited data supporting the concept of enhanced training following a high-carbohydrate diet. A number of field and laboratory studies with athletes have attempted to mimic actual sport conditions. For example, one group of soccer players improved 144

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performance on an intermittent exercise task designed to mimic physical activity in a game, while another group improved performance in a standardized intermittent running task and a run to exhaustion. In other studies, runners were able to endure longer on a treadmill run to exhaustion, swimmers were better able to maintain 400-meter swim velocity, while triathletes experienced a significant improvement in treadmill endurance following 30 minutes of swimming, cycling, and running. Based on the available data, Edward Coyle, an international authority in carbohydrate metabolism during exercise, indicated that physical performance seems better maintained with a high versus moderate carbohydrate diet. In general, the normal carbohydrate intake of athletes in training studies was increased from approximately 40–45 percent to 55–70 percent of the daily Calories for varying periods, but usually a week or more. This level of carbohydrate approximates the upper levels of the AMDR for carbohydrate. Not all athletes, including endurance athletes, may need highcarbohydrate diets all the time. In a recent meta-analysis, Erlenbusch and others indicated that subjects following a high-carbohydrate diet could exercise longer until exhaustion, but this finding applied more so to untrained individuals than trained individuals. As you may recall, aerobic exercise training improves the ability of the muscles to use fat as an energy source, so they may be somewhat less dependent on carbohydrate for a given training protocol. Thus, a moderatecarbohydrate diet may be adequate for trained athletes. For example, obtaining 45 percent of daily energy needs from carbohydrate might be considered moderate, as it is at the lower end of the AMDR. On such a diet, an endurance athlete who consumes 3,000 Calories per day during training would derive 1,350 Calories from carbohydrate (0.45 ⫻ 3,000), which is about 340 grams of carbohydrate. For a 60-kilogram athlete, this is about 5.6 grams of carbohydrate per kilogram body weight. Although this is slightly less than that recommended for endurance athletes, research has shown such amounts may be sufficient to maintain training on a daily basis. However, training may appear more stressful psychologically. In several studies, the psychological status of athletes, as measured by the vigor and fatigue components of the Profile of Mood States (POMS) questionnaire and their rating or perceived exertion (RPE) during exercise, was improved when they switched from moderate to higher carbohydrate diets. In his recent review, Coyle concluded that mood state seems better maintained with a high-versus-moderate carbohydrate diet. Utter and others recently reported reduced ratings of perceived exertion in subjects involved in prolonged (2.6 hours), intermittent cycling following ingestion of carbohydrate before and during the exercise bout. Coyle also indicates that a high-carbohydrate diet may help reduce symptoms of overreaching and, possibly, overtraining. Gleeson and others note that heavy prolonged exertion is associated with numerous hormonal and biochemical changes in the body, many of which may have detrimental effects on immune function. A well-balanced diet helps promote optimal immune function, and reviews by Gleeson and Nieman indicate that consuming carbohydrate during exercise attenuates rises in stress hormones such as cortisol and appears to limit the degree of exercise-induced immunosuppression. An impaired immune response is one possible factor associated with the overtraining syndrome. Carbohydrate intake following exercise also promotes

protein synthesis via the insulin effect, which may enhance muscle and overall recovery. Some nutritionists indicate that many athletes do not eat high carbohydrate diets because it may be impractical for them to do so. Selecting foods high in carbohydrate content, highlighted earlier in this chapter, provides a sound guide to increase the carbohydrate content of the diet, as do some of the recommendations in the following section regarding carbohydrate loading. Chapter 11 will provide additional information specific to daily caloric intake for planning a diet. In summary, as Coyle notes, athletes don’t train hard every day, so they do not require a high intake of carbohydrate every day of training. Nevertheless, a diet rich in healthful carbohydrates not only may have several major health benefits, but may also help guarantee optimal energy sources for daily exercise training. Moreover, as Louise Burke points out, experts in the field of energy metabolism indicate that there is no evidence that diets which are restricted in carbohydrate, such as the “zone” diet discussed in chapters 5 and 6, enhance training. Carbohydrate is the major fuel for most athletes in training. The slogan Train high and compete high refers to the concept of training and competing with high carbohydrate intake.

Ke y C o n c e p t s 䉴 Carbohydrate is the most important energy source for moder-

ately high- to high-intensity exercise. 䉴 Regular training increases the ability of the muscles to store and

use carbohydrate for energy production. 䉴 Low levels of blood glucose or muscle glycogen may be













contributing factors in the premature onset of fatigue in prolonged exercise. Low levels of muscle glycogen may contribute to impaired performance in prolonged, moderate- to high-intensity endurance exercise and in sports involving intermittent high-intensity exercise for 60–90 minutes. Consuming carbohydrate before and during prolonged, intermittent high-intensity or continuous exercise may help delay the onset of fatigue, but unless carbohydrate intake corrects a muscle glycogen deficiency, such practices will not improve performance in most athletic events of shorter duration. Combinations of carbohydrates, such as glucose and fructose, consumed during exercise appear to optimize the amount of exogenous carbohydrate that can be oxidized. Athletes should experiment with different carbohydrate supplementation strategies during training to help determine the amount, type, and timing of intake that may be suitable for them in competition. Glucose, sucrose, glucose polymers, and solid carbohydrates appear to be equally effective as a means of enhancing performance, but fructose may be more likely to cause gastrointestinal distress if used alone. Carbohydrates with a high glycemic index may facilitate muscle glycogen replenishment when consumed immediately after exercise and every 2 hours thereafter.

䉴 In order to maintain the quality of training, athletes who train at

moderate to high intensity on a daily basis should eat a healthful diet rich in complex carbohydrates, complemented with some high-glycemic-index foods, to replenish muscle glycogen.

C h e c k f o r Yo u r s e l f Given the recommendation to consume about 1.0 to 1.5 grams of carbohydrate per kilogram body weight per hour for 4–5 hours after exercise in order to rapidly replenish muscle glycogen, calculate how much carbohydrate you would need per hour and list specific foods, and amounts, that you might need to consume each hour.

Carbohydrate Loading What is carbohydrate, or glycogen, loading? Because carbohydrate becomes increasingly important as a fuel for muscular exercise as the intensity of the exercise increases, and because the amount of carbohydrate stored in the body is limited, muscle and liver glycogen depletion could be factors that may limit performance capacity in distance events characterized by high levels of energy expenditure for prolonged periods. Carbohydrate loading, also called glycogen loading and glycogen supercompensation, is a dietary technique designed to promote a significant increase in the glycogen content in both the liver and the muscles in an attempt to delay the onset of fatigue. It is generally used for 3–7 days in preparation for major athletic competitions.

What type of athlete would benefit from carbohydrate loading? In general, carbohydrate loading is primarily suited for those individuals who will sustain high levels of continuous energy expenditure for prolonged periods, such as long-distance runners, swimmers, bicyclists, triathletes, cross-country skiers, and similar athletes. In addition, athletes who are involved in prolonged stop-and-go activities, such as soccer, lacrosse, and tournament-play sports like tennis and handball, may benefit. For example, in a recent study Rico-Sanz and others concluded that exhaustion during soccer-specific performance is related to the capacity to use muscle glycogen, underlying the importance of glycogen loading. In essence, carbohydrate loading may be effective for athletes engaged in events that use muscle glycogen as the major energy source and that may lead to a depletion of glycogen in the muscle fibers. Athletes who compete in sports involving highintensity, short-duration energy expenditure will not benefit from carbohydrate loading. For example, Hatfield and others reported no effects of carbohydrate loading on performance in resistance training involving multiple sets of maximal jump squats. However, bodybuilders have been reported to carbohydrate load in attempts to appear more muscular owing to increased muscle glycogen levels and associated water retention. www.mhhe.com/williams9

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Recall from chapter 3 that humans have several different types of skeletal muscle fibers. In general, the slow-twitch red and fast-twitch red fibers are used mainly during long, continuous activities and are aerobic in nature, whereas the fast-twitch white fibers are used for short, fast activities and are anaerobic in nature. Consider the differences between a distance runner and a soccer player. The former may run at a steady pace for hours, whereas the latter will constantly be changing speeds, with many bouts of full speed interspersed with recovery periods of slower running. Research has shown that glycogen depletion patterns of the two different muscle fiber types are related to the type of exercise. Long, continuous exercise depletes glycogen principally in the slow-twitch red and fast-twitch red fibers, whereas fast, intermittent bouts of exercise with periods of rest, actually a form of interval training, primarily deplete glycogen in the fasttwitch white fibers. However, it should be noted that glycogen depletion may occur in all types of fibers in either prolonged continuous or intermittent exercise and may be quite appreciable, depending upon intensity and duration of the exercise bouts. If carbohydrate loading works for the specific muscle fiber involved, then both types of athletes may benefit. Both should have greater glycogen stores in the latter stages of their respective athletic contests.

How do you carbohydrate load? As you might suspect, the key to carbohydrate loading is to switch from the normal, balanced diet to one very high in carbohydrate content. The original, classic carbohydrate loading technique, emanating from earlier Scandinavian research, involved a glycogen depletion stage induced by prolonged exercise and a restricted diet. For example, a runner might go for an 18- to 20-mile run to use as much stored glycogen as possible, and then ingest very little carbohydrate in the following 2- to 3-day period.

TABLE 4.9

Exercise is continued during this 2- to 3-day period to keep glycogen stores low. Following the depletion stage, the loading stage began. During this phase, carbohydrate may contribute 70 or more percent of the caloric intake. The intensity and duration of exercise during this phase was reduced considerably. The usual case was to rest fully for 2 to 3 days. Thus, the classic carbohydrate loading pattern involved three stages: depletion, carbohydrate deprivation (high-fat/protein diet), and carbohydrate loading. However, this original method may be particularly difficult to tolerate, especially if one tries to exercise at high levels during the depletion phase. The lack of carbohydrate in the diet combined with the exercise bouts may elicit symptoms of hypoglycemia (weakness, lethargy, irritability). Moreover, prolonged exhaustive exercise may lead to muscle trauma, which may actually impair the storage of extra glycogen. This classic, original method is presented in table 4.9. Although some early research supported this technique, more recent data suggest that this strict routine may be unnecessary, particularly the total program of depletion. For example, in trained runners, research has shown that simply changing to a very highcarbohydrate diet, combined with 1 or 2 days of rest or reduced activity levels (tapering), will effectively increase muscle and liver glycogen. Well-controlled research has revealed that exhaustive running is not necessary to achieve muscle glycogen supercompensation. It appears to be important to continue endurance training, or other high-intensity training specific to the sport, during the 7–14 days prior to competition. Such training will serve to maintain adequate levels of GLUT-4 receptors to transfer blood glucose into the muscle cell and of glycogen synthase, the enzyme in the muscle that synthesizes glycogen from glucose. Evidence also suggests that if the total carbohydrate content is consumed over the entire week, in contrast to concentrating it in 2–3 days, there will be little difference in the muscle glycogen content between the two techniques.

Different methods for carbohydrate loading

A recommended method

Original, classic method

1st day:

tapering exercise

1st day:

depletion exercise

2nd day:

mixed diet, moderate carbohydrate; tapering exercise

2nd day:

high-protein/fat diet; low carbohydrate; tapering exercise

3rd day:

mixed diet, moderate carbohydrate; tapering exercise

3rd day:

high-protein/fat diet; low carbohydrate; tapering exercise

4th day:

mixed diet, moderate carbohydrate; tapering exercise

4th day:

high-protein/fat diet; low carbohydrate; tapering exercise

5th day:

high-carbohydrate diet; tapering exercise

5th day:

high-carbohydrate diet; tapering exercise

6th day:

high-carbohydrate diet; tapering exercise or rest

6th day:

high-carbohydrate diet; tapering exercise or rest

7th day:

high-carbohydrate diet; tapering exercise or rest

7th day:

high-carbohydrate diet; tapering exercise or rest

8th day:

competition

8th day:

competition

High-carbohydrate diet: 400–800 g per day depending on body weight; about 70–80 percent of dietary Calories should be carbohydrate.

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should consume about 10–12 grams per kilogram body weight over the 36–48 hours prior to the race. These Dietary sources of fats, Grams of carbohydrate, recommendations could total about proteins, and carbohydrates Amount and calories protein, and fat 400–800 grams per day, depending on the size of the individual, which is Meat, fish, poultry, eggs, cheese, 6–8 oz 0 grams carbohydrate* not too different from the generally select low-fat items Calories: 330–440 42–56 grams protein recommended dietary content of car18–24 grams fat bohydrate for the endurance athlete in Breads, cereals, and grain products 10–20 servings 150–300 grams carbohydrate regular training; Burke recommends Calories: 800–1,600 24–60 grams protein marathoners consume 7–12 grams of carbohydrate per kilogram body mass Vegetables, high Calorie (such as corn) 4 servings 60 grams carbohydrate during training. It is important to note Calories: 280 8 grams protein that the athlete should not change his or her diet drastically prior to compeFruits 4 servings 60 grams carbohydrate tition. Consuming a high-carbohydrate Calories: 240 diet during training will condition the Fats and oils 2–4 teaspoons 10–20 grams fat body to metabolize carbohydrate Calories: 90–180 properly during this loading phase. Table 4.10 represents a general Milk, skim 2 servings 24 grams carbohydrate dietary plan for carbohydrate loading. Calories: 180 16 grams protein The total caloric value and grams of Desserts, like pie 2 servings 102 grams carbohydrate carbohydrate should be adjusted to Calories: 700 6 grams protein individual needs. They are dependent 30 grams fat upon the size of the individual and daily energy expenditure in exercise. Beverages, naturally sweetened 8–24 ounces 20–60 grams carbohydrate It is important not to consume excess Calories: 80–240 Calories, for they may be converted Water 8 or more servings into body fat if in excess of the maxiCalories: 0 mal storage capacity of the muscle and liver for glycogen. TOTAL KCAL 2,700–3,860 Some guidelines for replenishment of glycogen were presented earlier. TOTAL GRAMS AND APPROXIMATE % OF DIETARY CALORIES Because glycogen loading for longCarbohydrate 416–606 65% distance events occurs over 2 to 3 days, it would be wise to stress comProtein 96–146 15% plex carbohydrates in the diet because of their higher nutrient content. HowFat 58–74 20% ever, simple carbohydrates may also Consult table 4.2 for specific high-carbohydrate foods in each of the food sources. be used effectively to increase muscle glycogen stores, as can high-carbohy*Beans are listed in the meat group because of their high protein content; however, they are also low in fat and high in carbohydrates, so drate sports drinks such as Gatorade they are an excellent selection from this food group. Substitution of beans for meat will increase the total grams of carbohydrate and the percentage of dietary Calories from carbohydrate. Energy Drink. Moreover, the diet Including high-carbohydrate drinks, such as glucose polymers, can add significant amounts of carbohydrate to the diet and may substitute should also include the daily requirefor other foods, such as desserts. ments for protein and fat. Source: Adapted from M. Forgac,“Carbohydrate Loading: A Review” in Journal of the American Dietetic Association 75:42–5, 1979. If, for some reason, the athlete cannot carbohydrate load over the 3–7 day period, a rapid protocol may be effective. Fairchild and Although there may be a number of variations in the carbohyothers found that one day of a high-carbohydrate intake, approxidrate loading protocol, a generally recommended format is also mately 10 grams of high-glycemic-index carbohydrate per kilopresented in table 4.9. The interested athlete may want to experigram body mass, nearly doubled the muscle glycogen ment with both techniques, and also make adjustments through concentration, from 109 to 198 mmol/kg wet weight muscle. The experience. carbohydrate feeding was preceded by a short bout of near maxiSports scientists have generally recommended that carbohydrate mal-intensity exercise for 3 minutes. They reported that these intake during carbohydrate loading should be about 8–10 grams muscle glycogen levels were comparable to those achieved over a per kilogram body weight, and Louise Burke, from the Australian 2–6 day regimen. Institute of Sport, recently recommended that marathon runners TABLE 4.10 Daily food plan for carbohydrate loading

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Most prolonged endurance events begin in the morning. The last large meal should be about 15 hours prior to race time, possibly topped off with a simple carbohydrate snack before retiring for the night. Some athletes drink a glucose polymer for the last major meal to avoid the presence of intestinal residue the morning of competition. A carbohydrate breakfast such as orange juice, toast, jelly, or other carbohydrates along with some protein may be eaten 3 to 4 hours prior to competition. Review the discussion of precompetition meals on pagess 76–77. This overall dietary regimen should help maximize muscle and liver glycogen stores. The athlete should then follow the guidelines presented previously relative to carbohydrate intake before and during performance.

Will carbohydrate loading increase muscle glycogen concentration? Most, but not all, studies show that an appropriate carbohydrate loading protocol, compared to normal or low dietary carbohydrate intake, will substantially increase muscle glycogen levels. Although some previous research found that muscle glycogen levels in the early phases of loading did not increase as much in females as in males, more recent, better controlled research by James, Paul, and Tarnopolsky, with their associates, revealed that carbohydrate loading increased muscle glycogen concentration in both men and women provided total energy intake was adequate. No gender differences were noted. McLay and others noted that women generally have lower resting muscle glycogen levels during the midfollicular phase of the menstrual cycle, as compared to the midluteal phase, but the lower glycogen storage in the midfollicular phase could be overcome by carbohydrate loading. In general, carbohydrate intakes of 8 grams or more per kilogram body weight will provide optimal muscle glycogen concentrations for both males and females. Glycogen content in the muscle has been reported to increase about two to three times beyond normal and liver glycogen content nearly doubled following a carbohydrate loading regimen, and this increase may last at least 3 days in a rested athlete. However, it may be important to taper and rest about 2 days prior to the event. Fogelholm and others reported no increase in muscle glycogen following the classic loading protocol if athletes continued to train 45–60 minutes per day, even though the training was easy. This finding merits confirmation, as other studies have shown muscle glycogen supercompensation when individuals tapered, although most studies use at least 1 day of rest before the competitive exercise test. Carbohydrate loading has been shown to increase muscle glycogen stores after exhaustive exercise, but apparently the process does not work repeatedly within a short time frame. McInerney and others reported that muscle glycogen supercompensation did not occur when subjects attempted to increase muscle glycogen levels repeatedly during a 5-day period while performing exhaustive exercise every other day. In general, the full carbohydrate loading procedure should be used sparingly, mainly in preparation for a peak event. However, athletes should experiment with the procedure, or at least experiment with various forms of carbohydrate to be used, sometime during training before using it in competition. 148

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How do I know if my muscles have increased their glycogen stores? The most accurate way would be to have a muscle biopsy taken (a needle is inserted into the muscle and a small portion is extracted and analyzed), but this is not very practical. A practical method that has been recommended is to monitor changes in body weight. Kreitzman and others noted that glycogen is stored in the liver, muscles, and fat cells in hydrated form (three to four parts water), and weight gain may occur with carbohydrate loading. Thus, keeping an accurate record of your body weight, which should be recorded every morning as you arise and after you urinate, may help you determine the answer to this question. Approximately 3 grams of water are bound to each gram of stored glycogen. If your body stores an additional 300–400 grams of glycogen, along with 900–1,200 grams of water, your body weight will increase about 1,200–1,600 grams, or 2.5–3.5 pounds above your normal training weight during the loading phase. The weight gain would be greater with additional glycogen storage. This is indicative that the carbohydrate loading has been effective, since rapid weight gains from one day to another are usually due to changes in body water content. However, based on research with animals, Cheuvront and others noted the possibility that common estimates of water associated with glycogen are exaggerated and body mass does not change appreciably from baseline during glycogen supercompensation in humans. Additional research is recommended to explore the effect of muscle glycogen supercompensation on body weight in humans. Bodybuilders may use carbohydrate loading because the increased muscle water content may hypertrophy the muscles, leading to a more muscular, aesthetic appearance in competition. However, Balon and others reported no increase in the girths of seven different muscle groups following a carbohydrate loading regimen in resistance-trained bodybuilders. Possibly the white fast-twitch muscle fibers in bodybuilders, which are already large, may not respond as much to carbohydrate loading as might the red slow-twitch, oxidative muscle fibers.

Will carbohydrate loading improve exercise performance? Although athletes in most sports may benefit from an increased carbohydrate content in the diet, the full procedure of carbohydrate loading is not necessary for the vast majority of athletes. In general, carbohydrate loading has not been found to enhance performance in single highintensity exercise tasks ranging up to 60 minutes or so. For example, Vandenberghe and others found no effect of muscle glycogen levels (manipulated by carbohydrate loading) on muscle glycolytic rate during very high-intensity exercise (125 percent VO2 max) or on all-out performance at this exercise intensity, a time approximating 3 minutes. Various other studies have reported that carbohydrate loading does not increase the speed of runners in events ranging from 10 kilometers to the half-marathon or in cycling time-trials up to 60 minutes. However, Pizza and others,

using an exercise task consisting of a 15-minute submaximal run followed by a run to exhaustion at 100 percent VO2 max, reported an increase in performance associated with carbohydrate loading. The run to exhaustion approximated 5 minutes. In general, this finding is an exception to the rule, so additional research is warranted. Carbohydrate loading may benefit athletes involved in prolonged, intermittent high-intensity exercise tasks. Akermark and others, using elite Swedish ice hockey players on two competitive teams as subjects, reported that the team that carbohydrate loaded between two games had higher muscle glycogen levels, which were associated with improvement in distance skated, number of shifts skated, and skating speed in the second game. Carbohydrate loading has been studied most extensively as a means to improve performance in more prolonged aerobic endurance exercise tasks. In general, the results are supportive of an ergogenic effect. Laboratory studies have shown that exercise time to exhaustion is closely associated with the amount of muscle glycogen available or the amount of carbohydrate in the diet. When endurance performance is compared after subjects have been on either a high-fat/high-protein diet, a mixed, balanced diet, or a high-carbohydrate diet for 4–7 days, performance on the highfat/high-protein diet is worse than on the other two. However, research findings comparing a mixed, balanced diet with a highcarbohydrate diet have been equivocal, with some results favoring the high-carbohydrate diet and others revealing no difference between the two. A number of studies have shown that carbohydrate loading, as compared to a normal carbohydrate intake, does not enhance endurance performance. However, in many of these studies the performance tests may not have been long enough for the individual to derive the full benefit from carbohydrate loading as the duration was less than two hours. On the other hand, one of the best-designed, placebo-controlled studies also found no beneficial effect of carbohydrate loading. Using a cycling exercise protocol designed to be similar to a competitive 100-km road race (about 2.5 hours), Burke and others found that a 3-day carbohydrateloading regimen (9 grams carbohydrate/kg), as compared to a moderate carbohydrate diet (6 grams carbohydrate/kg), did not enhance performance even though muscle glycogen content increased significantly. They also provided carbohydrate (1 gram per kilogram body mass) during the exercise test and suggested that the availability of blood glucose during exercise may offset any detrimental effects on performance of lower preexercise muscle and liver glycogen concentrations. Additionally, the authors noted that carbohydrate loading may possibly be effective in prolonged endurance events in which the exercise intensity is relatively more constant. In this study, the exercise task included repeated high-intensity sprints, which are common in cycling races but not in other events, such as marathon running. Additionally, the cyclists consumed over 60 grams of carbohydrate per hour, which although recommended for runners as well, is often more difficult to do in running than cycling. Finally, the investigators also indicated that although the time to finish the 100-km ride (about 1.6 minutes faster with carbohydrate loading) was not statistically significant, such an effect, if real, could make a difference in the finishing order of top cyclists.

On the other hand, a number of studies suggest that carbohydrate loading may be an effective technique to enhance endurance exercise performance. However, it should be noted that most of these studies have not used a true placebo, as was done in the aforementioned study by Burke and others. Hargreaves and others note that the increased muscle glycogen associated with carbohydrate loading may be used more readily in exercise tasks approximating 65–70 percent VO2 max, which might be a reasonable pace for an average runner competing in a marathon. If muscle glycogen were used more rapidly during the early stages of a marathon, theoretically carbohydrate loading would provide no advantage during the latter stages of the race. However, Bosch and others note that although carbohydrate loading may reduce the relative contribution of blood glucose to overall carbohydrate oxidation, the improved performance may be attributed to the initially greater amount of muscle glycogen as a means to spare the premature use of blood glucose and liver glycogen. A supportive study was conducted by Clyde Williams in England. Male and female runners performed a 30-kilometer (18.6 miles) run on a treadmill and then were divided into two groups. One used a carbohydrate loading technique for a week while the other group maintained their normal carbohydrate intake. Although there were no significant differences between the groups for overall performance time in the 30 kilometers, the carbohydrateloading group ran the last 5 kilometers significantly faster compared to their initial trial. A study by Rauch and others compared the effects of a 3-day carbohydrate loading protocol (10 grams carbohydrate per kilogram body weight per day, versus a normal mixed diet at 6 grams per kilogram) on performance in a 3-hour cycling task. Endurance-trained cyclists rode 2 hours at 75 percent VO2 max, interspersed with five 60-second sprints every 20 minutes, and then completed a 60-minute performance ride. The carbohydrateloading regimen significantly increased the distance covered in the performance ride. In another cycling study, Walker and others studied the effect of a carbohydrate-loading and exercise-tapering regimen in well-trained women on performance of a cycling test to exhaustion at 80 percent VO2 max. The high carbohydrate diet (approximately 78 percent carbohydrate), as compared to the moderate diet (approximately 48 percent carbohydrate), induced a 13 percent greater muscle glycogen content and an 8 percent improvement in cycling time. Moreover, several field studies with runners and cross-country skiers have shown improved performances with carbohydrate loading. In general, carbohydrate loading, in contrast to a mixed diet, did not enable these athletes to go faster during the early stages of their events, but the high glycogen levels enabled them to perform longer at a given speed. The end result was an overall faster time. Failure to carbohydrate load has also been identified as one of the factors contributing to collapse of runners in an ultramarathon. Indeed, in a recent review, Peters noted that current evidence continues to support high carbohydrate intakes for ultraendurance athletes to increase muscle glycogen stores before the event. Based on studies published prior to that of Burke and others, several major reviews support the performance-enhancing effectiveness of carbohydrate loading. Clyde Williams reported that an www.mhhe.com/williams9

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International Consensus Conference on sports nutrition concluded that the most significant influence on performance was the amount of carbohydrate stores in the athlete’s body prior to heavy endurance exercise, which is the purpose of carbohydrate loading. Hawley and others concluded that carbohydrate loading would postpone fatigue in endurance events lasting over 90 minutes, and may improve performance in events where a set distance is covered as fast as possible, such as cycling and running, by about 2–3 percent according to some scientists. In the most recent review, Williams and Lamb generally support these viewpoints relative to male athletes. However, they note that although carbohydrate loading can increase muscle glycogen stores in women, it appears to offer no benefit to their endurance performance; Tarnopolsky indicates that women oxidize more lipid and less carbohydrate compared to men during endurance exercise, a finding that may underlie this viewpoint. Although carbohydrate loading may be an effective technique to enhance performance in prolonged aerobic endurance events, research suggests the most effective protocol is to carbohydrate load and use carbohydrate supplements during the event. Kang and others recently noted this method can exert an additional ergogenic effect by preventing a decline in blood glucose levels and maintaining carbohydrate metabolism during the later stages of prolonged aerobic exercise. Given the findings of the recent study by Burke and others, this method appears to be the most appropriate as it will help provide increases in muscle glycogen before exercise as well as replenishment of blood glucose during exercise, two factors that may be associated with enhancement of endurance performance.

Are there any possible detrimental effects relative to carbohydrate loading? From a performance standpoint, the extra body weight associated with the increased water content may be a disadvantage. In activities where moving the body weight is important, extra energy will be required to lift the extra 2–3 pounds of body water. However, in most performance events for which carbohydrate loading is advocated, the benefits from the energy aspects of the increased glycogen should more than offset the additional water weight. Moreover, if the individual is performing in a hot environment, the extra water, even small amounts, could be available as a source of sweat and may be helpful in controlling body temperature during exercise in the heat. Although one study suggested that the water stored with glycogen did not confer any advantage in regulation of body temperature while exercising in heat, the duration of the exercise, only 45 minutes, would not be sufficient to benefit from the increased water levels. Another study conducted in South Africa revealed no beneficial or detrimental effects of carbohydrate loading on body temperature during 2.5 hours of exercise in a moderate environment (70° Fahrenheit; 21° Celsius). However, performance in longer exercise tasks with greater levels of water losses might be benefited. Additional research is needed to study the potential effects of increased muscle glycogen levels on body water availability and temperature 150

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regulation during prolonged exercise under warm environmental conditions. From a health standpoint there may be some potential hazards to individuals with certain conditions. Although diabetics have been known to carbohydrate load, they should consult their physicians prior to using the technique. Individuals with high bloodlipid or cholesterol levels might avoid the high-fat/high-protein diet phase of the depletion stage if, for some reason, they prefer the original, classic method of carbohydrate loading. Blood serum lipids and cholesterol have been reported to rise significantly during this phase. In addition, these individuals should eat mostly low-glycemic-index carbohydrates during the loading phase because an increased intake of high-glycemic-index carbohydrates may raise blood-lipid levels. Furthermore, hypoglycemia may occur during the high-fat/high-protein phase. Several laboratory studies and one case study have reported electrocardiographic (ECG) abnormalities in individuals who used the classic carbohydrate loading technique. Although no cause and effect relationship was determined, these investigators speculated that hypoglycemia or glucose intolerance may be involved. On the other hand, other well-controlled research with marathoners and typical joggers revealed no ECG changes following the classic method of carbohydrate loading. Several investigators theorized that carbohydrate loading could possibly lead to destruction of muscle fibers by excessive glycogen storage, but no data were presented to support their contentions. It appears that the muscle has a maximal capacity to store glycogen, approximately 4 grams/100 grams of muscle, and beyond that level excess carbohydrate would apparently be converted to fat and stored in adipose tissues. Other potential problems with the high-carbohydrate phase are diarrhea, nausea, and cramping, particularly when the diet is changed drastically or large amounts of simple carbohydrates are consumed. Individuals who wish to carbohydrate load should experiment with such diets during their training and not just before competition. In general, however, the recommended carbohydrate loading technique presented in table 4.9, which at the most is only a 7-day dietary regimen, poses no significant health hazards to the normally healthy individual.

Ke y C o n c e p t s 䉴 Carbohydrate loading is not a technique for all types of athletes,

but it may benefit athletes involved in long-distance competition such as marathoning. 䉴 Various carbohydrate-loading techniques may effectively increase muscle glycogen stores, but tapering exercise or rest and a high-carbohydrate diet are the essential points.

C h e c k f o r Yo u r s e l f If you know any marathon runners or prolonged endurance athletes, interview them about their dietary strategies prior to a major competition. Do they practice carbohydrate loading?

Carbohydrates: Ergogenic Aspects Throughout this chapter you have learned that carbohydrate intake, in a variety of ways, may be used to enhance physical performance. Truly, carbohydrates represent one of our most important ergogenic nutrients. In this brief section we shall look at several forms of carbohydrate that might possess ergogenic properties. Additionally, numerous carbohydrate-based products, such as the sports “energy” drinks, have been marketed to athletes and many contain purported ergogenic substances, such as caffeine, ephedrine, and amino acids. These specific nutritional ergogenics will be discussed in later chapters where appropriate.

Do the metabolic by-products of carbohydrate exert an ergogenic effect? Recall that the primary mechanism in the transformation of muscle glycogen into energy is glycolysis. The end product during aerobic metabolism is normally pyruvate. However, glycolysis leading to the formation of pyruvate involves production of a number of metabolic by-products in a chain of about a dozen sequential steps, each step being controlled by an enzyme (see appendix G, figure G.1). One theory of fatigue is that if one of these steps is blocked by inactivation of an enzyme, glycolysis may not continue at an optimal rate since a necessary metabolic by-product may be in short supply. This blocked step could represent a weak link in the chain, possibly reducing the formation of pyruvate and subsequent ATP production. Pyruvate has been studied as a potential ergogenic aid, as have other metabolic by-products of carbohydrate metabolism. Pyruvate Pyruvate is a three-carbon metabolic by-product of glycolysis. Although the mechanism of its underlying potential as an ergogenic aid is unknown, pyruvate is theorized to accelerate the Krebs cycle or use glucose more efficiently, both of which could enhance exercise performance. DHAP is a combination of pyruvate and dihydroxyacetone, another three-carbon metabolic by-product of glycolysis. Pyruvate administered alone has been used in attempts to decrease body fat and increase muscle mass, possibly by speeding up Krebs-cycle activity. In a recent review, Antonio and others reported significantly more body weight and fat loss in obese women following pyruvate supplementation (19 grams/day) as well as in obese males and females with a smaller dose of pyruvate (6 grams/day). Kalman and others reported also a significant decrease in body weight and fat mass in healthy, overweight men and women following 6 weeks of pyruvate supplementation (6 grams per day). No exercise performance data were reported from these studies. Although these findings may be important to the obese, they may not be applicable to the healthy, nonobese, well-trained individual as a means of shedding additional body fat for sports competition. Research investigating the ergogenic effect of pyruvate supplementation is very limited, and generally has not shown any beneficial effects on exercise performance in either untrained or trained subjects. Koh-Banerjee and others studied the effects of supple-

mentation with calcium pyruvate (5 grams daily for 30 days) on body composition and metabolic responses to submaximal and maximal exercise in untrained females undertaking exercise training. No beneficial effects were noted. In a double-blind, crossover study, Morrison and others found that pyruvate supplementation (7 grams/day for one week) did not enhance cycle time to exhaustion in well-trained male cyclists in an aerobic endurance test. However, some research suggests beneficial effects of DHAP supplementation. Previous studies with animals have shown that DHAP increases muscle glycogen content, so Ronald Stanko and his associates at the University of Pittsburgh investigated the potential ergogenic effect of DHAP in humans. Two studies were conducted, both using untrained males as subjects. The dosage of DHAP in both studies was 100 grams per day for 7 days; DHAP was prepared in a 3:1 ratio of dihydroxyacetone (75 g) to sodium pyruvate (25 g) and administered either in Jello or artificially sweetened fluids. The placebo in both studies was 100 grams of Polycose, a carbohydrate. The DHAP or Polycose was substituted for a portion of the carbohydrate in the diet. Both studies were well designed, using a double-blind, placebo, repeated-measures crossover approach. In the first study, the diet was standardized at 55 percent carbohydrate of the daily caloric intake. The criterion test was an arm ergometer exercise task to exhaustion at 60 percent VO2 peak following a week of supplementation. DHAP significantly increased endurance time, attributed primarily to an increased muscle glycogen concentration and increased extraction of blood glucose, both factors providing more glucose to the exercising muscle. In the second experiment, subjects consumed a high-carbohydrate diet (70 percent of the daily caloric intake). The criterion test was a cycle ergometer exercise task to exhaustion at 70 percent VO2 peak. DHAP improved performance in an identical fashion to the first study, the effect being attributed to an increased blood glucose extraction by the exercising muscle. The results of these two well-controlled studies indicate an ergogenic effect of DHAP with untrained subjects, but confirming data are needed with well-trained athletes. Lactate Salts As noted previously, lactic acid is a metabolic byproduct of anaerobic glycolysis. We also indicated that although lactic acid is often associated with fatigue, most sport scientists theorize it is the hydrogen ion release that increases the acidity and impairs performance, not the lactate itself. Lactate is actually a small metabolite of glucose; its formula is C3H5O3, about half of that of glucose, C6H12O6. Thus, lactate still possesses considerable energy and, as Van Hall recently noted, may be converted back to pyruvate to enter the energy pathway in the skeletal muscles. Lactate may also be converted back to glucose by the liver. Various lactate supplements have been studied as a means to enhance endurance performance. For example, CytomaxTM is a sports drink that contains lactate in a patented form, alpha-LPolylactate. CytomaxTM also contains fructose, glucose, and a glucose polymer. In an early study, Fahey and others investigated the effect of polylactate (80 percent polylactate, 20 percent sodium lactate, in 7 percent solution with water), a glucose polymer, and an artificially www.mhhe.com/williams9

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sweetened placebo on various psychological, physiological, and metabolic parameters during cycling at 50 percent of VO2 max for 3 hours. The fluids were consumed 5 minutes before exercise and at 20-minute intervals during exercise. There were no differences between treatments in perceived exertion, lactate, heart rate, oxygen consumption, rectal temperature, or selected skin temperatures. Moreover, Fred Brouns and his colleagues at Maastricht in the Netherlands reported that 3 weeks of supplementation with oral lactate salts did not influence the removal of lactate during and following exercise, suggesting no value to lactate supplementation in this regard. Bryner and others compared the effects of four sports drinks (2 percent lactate; 8 percent carbohydrate; 2 percent lactate/8 percent carbohydrate combination; placebo) on performance in a cycle ergometer exercise test to exhaustion which also incorporated a 30-second Wingate cycle power test. Subjects consumed 100 grams of carbohydrate several hours before the test, and then consumed the sport drinks during the test. There were no significant differences among the sports drinks for endurance time, peak power, glucose, insulin, or blood pH, indicating that lactate supplementation, either alone or in combination with carbohydrate, provided no advantage over carbohydrate alone. More recently, Azevedo and others compared the effects of CytomaxTM with a leading sports drink (containing glucose and fructose) on performance of experienced cyclists. In a crossover study, the subjects consumed either drink both before and during the cycling task, which consisted of cycling at 62 percent VO2 peak for 90 minutes, followed by high-intensity cycling to exhaustion at 86 percent VO2 peak. The investigators reported that lactate was used more rapidly and to a greater extent than fructose or glucose, and endurance time with CytomaxTM more so than other sports drinks was 25 percent longer in the high-intensity cycling test. Based on the current data, it would appear that lactate preparations may provide additional energy, somewhat comparable to carbohydrate sources. The preliminary research findings showing an ergogenic effect of CytomaxTM more so than other sports drinks need confirmation from other research laboratories. Ribose Ribose is a 5-carbon monosaccharide found throughout body cells as part of various compounds, such as RNA (ribonucleic acid) in the cell nucleus. Ribose also comprises the sugar portion of adenosine, the nucleotide found in ATP (adenosine triphosphate). ATP, as you recall, is the immediate source of energy for muscle contraction both in the heart and skeletal muscles. Although found in nature, very little ribose is consumed in a natural diet. Instead, a specific metabolic pathway (pentose phosphate pathway) produces ribose from glucose to meet our body needs. Recently, ribose supplements (made from corn sugar) have been marketed to physically active individuals as a means to promote faster recovery in heart and skeletal muscles, presumably by facilitating the formation of adenosine, one of the major components of ATP. Research indicates that strenuous exercise may necessitate rapid recovery of adenosine within muscle cells, which might benefit from adequate ribose. Pliml and others found that ribose ingestion (60 grams daily for 3 days) improved exercise performance time in patients with severe coronary artery disease, while 152

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other studies have suggested that ribose, when supplemented, could serve as an energy source and promote adenosine synthesis in various patient groups. The effect of ribose supplementation has been evaluated using healthy, physically active individuals and athletes. Several studies used an acute supplementation protocol. Kerksick and others reported that 3 grams of ribose, provided to moderately trained male cyclists about 25 minutes prior to exercise, had no effect on five maximal 30-second anaerobic capacity cycling tests with a 3-minute recovery. In a crossover study, Peveler and others also found no effect of an acute 625-milligram dose of ribose on peak power, mean power, or rate of fatigue in three intermittent 30-second Wingate tests of anaerobic capacity in healthy males. Research using chronic supplementation of ribose also does not support an ergogenic effect. Berardi and Ziegenfuss studied the effect of oral ribose supplementation (32 grams over a 36-hour period) on high-intensity, intermittent, anaerobic cycle ergometer performance; the exercise task consisted of six 10-second sprints with a 60-second recovery. They concluded that ribose supplementation does not have a consistent or substantial effect on anaerobic cycle sprinting as evaluated by peak and mean power output. Hellsten and others reported that 3 days of ribose supplementation (based on body weight, approximately 45 grams daily) elicited a greater resynthesis of ATP compared to the placebo. However, the slight increase in ATP availability did not enhance performance, as there were no differences between the placebo and ribose supplement for mean and peak power outputs. The authors note that a small reduction in muscle ATP does not appear to limit high-intensity exercise performance. In a well-designed study, Op ’T Eijnde and others evaluated the effect of oral ribose supplementation (16 grams/day for 6 days) on two maximal knee-extension exercise protocols and ATP recovery. The exercise bouts were separated by a 60-minute rest period. They concluded that oral ribose supplementation had no effect on maximal intermittent exercise performance or ATP recovery. In the longest supplementation protocol, Dunne and others compared the effects of ribose or dextrose (10 grams each before and after practice) supplementation for 8 weeks on 2,000-meter rowing performance in female collegiate rowers. Over the course of the 8 weeks performance in both groups improved, but the dextrose group (about 10 seconds faster) showed significantly more improvement at 8 weeks than the ribose group. The investigators thought that the ribose did not impair performance, but the dextrose simply may have elicited a greater improvement. In their recent review, Dhanoa and Housner note that although ribose manufacturers claim it provides an ergogenic benefit, scientific research does not support this claim. Current data do not support an ergogenic effect of ribose supplementation. Multiple Carbohydrate By-Products Sports supplements manufacturers often combine multiple nutrients in a single supplement on the theory that each may exhibit an ergogenic effect, but the effect will be amplified with multiple components. Limited research is available with multiple by-products of carbohydrate metabolism, but Brown and others recently investigated the ergogenic potential of a multi-nutrient supplement composed primarily of intermediates of the Krebs cycle, which may be derived

from carbohydrate, fat, or protein. Three weeks of supplementation did not improve cycling time to exhaustion at approximately 70–75 percent VO2 max, nor did it improve the rate of recovery.

Ke y C o n c e p t 䉴 Metabolic by-products of carbohydrate metabolism have been

tested as ergogenics. Most have been found to be ineffective, although research with physically trained individuals is limited with several purported ergogenic products.

C h e c k f o r Yo u r s e l f Go to a health food store that sells sports supplements and ask the clerk for carbohydrate products, including metabolites, that may help you train or compete more effectively. Evaluate the supplement fact labels for content and performance claims. What is your judgment?

Dietary Carbohydrates: Health Implications Although improving somewhat, the diet of the typical American and Canadian still appears to be unbalanced. In general, we consume too many Calories for the level of physical activity we do, and we eat too much of the unhealthy fats and carbohydrates. Such a diet may pose several health problems. As we shall see in chapter 5, excessive consumption of total and saturated fat appears to be of major concern relative to the development of several chronic diseases. In this section, we discuss the health aspects of dietary carbohydrates. In general, the health effects associated with various sugars and starches is not in the substances themselves, but rather in the nutrients that accompany them in the foods we eat. For example, sugar in orange juice is little different from sugar in a soda, but the orange juice contains substantial amounts of vitamin C, potassium, and other nutrients, whereas the soda has none unless fortified. Whole grains contain more fiber and more of some micronutrients than refined grains. In the recent past, low-carbohydrate diets have been all the rage. As shall be noted in chapter 10, research has indicated that such diets may have some health benefits, but these health benefits appear to be attributed more to decreased caloric intake than to diet composition. The pendulum, rightfully so, has shifted toward a diet rich in carbohydrate, specifically healthier carbohydrate choices. Nutritional objectives in Healthy People 2010 and in the 2005 Dietary Guidelines for Americans recommend that we should consume more carbohydrates, particularly complex carbohydrates and fiber-containing foods, often referred to as the good carbs. We should also moderate intake of refined carbohydrates and added sugars, often referred to as the bad carbs. Although no foods, or carbohydrates, are inherently good or bad, following these two general guidelines may produce some significant health benefits. Additionally, an appropriate exercise program may have a healthful influence on carbohydrate metabolism.

How do refined sugars and starches affect my health? As noted previously, sugars may be found naturally in foods, or they may be manufactured from starches, such as high fructose corn syrup, and added to foods. Refined starches are predominant in many foods, such as white bread, pasta, and rice. Consumption of refined sugars and starches in excess may be associated with various health risks, attributed mainly to their high glycemic index. Dental Caries One of the most common health problems that has been associated with dietary sugar is tooth decay, or dental caries. However, the National Institutes of Health in its consensus statement on management of dental caries throughout life noted that effective preventive practice involves a number of factors, including proper oral hygiene (brushing, flossing, use of fluoride) and dietary modifications (use of sugarless products). Tooth decay is not necessarily a matter of how much sugar one eats, but in what form and how often. Dental erosion is increasing and is associated with dietary acids, a major source of which is soft drinks. Sticky, chewy, sugary foods eaten often between meals increase the risk of developing dental caries. Starchy foods that adhere to teeth, like bread, are also cariogenic. Such foods may increase the presence of dental plaque, which may lead to periodontal infection. Seymour and others cite epidemiological research supporting a relationship between periodontal infection and various systemic diseases, such as coronary heart disease, stroke, and diabetes. The infection may lead to systemic inflammation, which may induce adverse effects, such as atherosclerosis. Seymour and others indicate that the control of oral disease is essential in the prevention and management of these systemic conditions. Of particular interest to athletes, von Fraunhofer and Rogers reported far greater enamel dissolution in flavored and energy (sports) drinks than previously noted for water. They noted that sipping sports drinks over long periods of time may erode tooth enamel; therefore, drink quickly. On the other hand, Mathew and others recently reported no relationship between consumption of sports drinks and dental erosion in university athletes. Nevertheless, scientists have developed a prototype sports drink, containing substantial amounts of calcium and maltodextrins, which is alleged to cause less dental enamel erosion than the typical commercial sports drink. Chronic Diseases Over the years, dietary intake of refined sugar has been alleged to contribute to a wide variety of health problems, including obesity, diabetes, heart disease, and cancer, as well as various psychological afflictions such as hyperactivity in children, premenstrual syndrome (PMS), and seasonal affective disorder (SAD). Such allegations have been based mainly on theoretical considerations, but with support from some recent epidemiological studies. An habitual diet rich in high-glycemicindex foods theoretically may lead to insulin resistance and high serum triglyceride levels, risk factors for diabetes and heart disease, respectively. This may be especially so in individuals who are obese, and will be discussed in detail in chapter 10. Bantle also indicated that fructose, which is a low-glycemic-index www.mhhe.com/williams9

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sugar, may increase serum triglycerides and may be a contributing factor to obesity. Individuals should avoid high-fructose corn syrup, but eating fruits with naturally occurring fructose is not a cause for concern. Added sugars can increase caloric intake and predispose to obesity. High-sugar intake has been associated with development of cancer. Two recent, large epidemiological studies by Larsson and Stattin and their associates found that increased consumption of sugar and high-sugar foods, particularly sugar-sweetened sodas, increases the risk of pancreatic cancer. The increased sugar intake may cause the pancreas to produce more insulin, which may cause hyperinsulinemia and increased insulin-like growth factor, factors that may stimulate cell division in the pancreas and lead to cancer. Additionally, as discussed previously, a high-carbohydrate diet can affect the fTRP:BCAA ratio and the formation of the neurotransmitter serotonin. Serotonin may influence mood and behavior associated with PMS and SAD or other psychological states. However, the National Academy of Sciences in its recent DRI recommendations for carbohydrate noted that given the currently available scientific evidence relative to the effect of dietary sugar on dental caries, psychological behavior, cancer, risk of obesity, and risk of hyperlipidemia, there is insufficient evidence to set a UL for total or added sugar in the diet. Nevertheless, the Academy noted that the theory linking a high-glycemic index to certain health problems, such as diabetes and CHD, appears to be valid and supported by some studies, but the evidence at this time appears to be insufficient to substantiate the theory. Furthermore, the Academy noted that individuals who consume excess amounts of added sugars may not obtain sufficient amounts of various micronutrients, and that this may lead to adverse health effects. Thus, although the Academy did not set a UL, it did set a maximal intake level of 25 percent or less of energy from added sugars. Given these considerations, and the fact that many health organizations recommend a reduced intake of refined sugars to about 10 percent or less of the daily caloric intake, it appears to be prudent to moderate your consumption of refined sugars and starches. Suggestions to decrease intake of refined starches and sugars were presented in chapter 2. To reiterate some of these points: • Eat refined starches and grains sparingly, mainly as a side dish; eat them with added protein or small amounts of healthier fats to reduce the glycemic load. • Read food labels and select foods low in sugar. Most of the sugar we eat has been added to our foods during commercial processing. Sugar is everywhere. Even “healthy-type” foods such as yogurt and instant oatmeal may contain substantial amounts of sugar. • Know the different ways in which sugar may appear on a food label. Sugar is sugar. There is no additional nutritional value of added “natural” sugars, such as fruit juice concentrate, compared to ordinary table sugar (sucrose). • Reduce the sugar in foods prepared at home. Use less sugar at the table. • Eat more fruits for a naturally occurring source of sugar.

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• Decrease intake of soft drinks. A typical regular soft drink contains 10 teaspoons of sugar, about 150 Calories and constitutes the largest source of added sugars in the diet. Drink diet soda, or better yet, water. • Use other sweeteners, such as cinnamon, nutmeg, ginger, or artificial sweeteners.

Are artificial sweeteners safe? Artificial sweeteners are products designed to provide sweetness, but fewer or no Calories, as a means for individuals to reduce refined sugar consumption. However, in a recent review Liebman noted that although dietary intake of artificial sweeteners has increased over the past ten years, so too has the consumption of refined sugars. As these products have been used as food additives, their safety has been evaluated. A number of artificial sweeteners have been produced over the years, and currently several are approved for use by the FDA in the United States (see table 4.11). Saccharin is a noncaloric derivative of coal tar. Aspartame is derived from two amino acids (aspartic acid and phenylalanine) and contains 4 Calories per gram. Neotame is derived from the same amino acids as aspartame. Acesulfame-K is a naturally occurring potassium salt. Sucralose is produced by altering the sugar molecule. Sugar alcohols, such as sorbitol, erythritol, mannitol, and lactitol, are not absorbed, so they are low glycemic and provide no Calories. Years ago saccharin in extremely large doses had been shown to cause urinary bladder cancer in laboratory animals, and according to the Delaney clause, it should be banned as an additive to food products. However, the United States Congress passed a law exempting saccharin from the Delaney clause. Nevertheless, a warning relative to the association between saccharine and cancer was required on food labels for products containing saccharin. Epidemiological data with humans have not shown any relationship between urinary bladder cancer and saccharin at levels normally consumed by the general population, so it is assumed to be safe and has been removed from the government’s list of carcinogens. The food label warning is no longer required in the United States. However, Canada still prohibits the use of saccharin in foods, and some consumer protection groups, such as the Center for Science in the Public Interest, recommend avoidance of saccharincontaining products. The safety of aspartame, also known as Equal or NutraSweet, has been questioned because some reports have associated it with headaches, dizziness, or fatigue in some individuals, which may have been an allergic reaction. Previous studies also have associated aspartame use with brain tumors. More recently, an Italian study, with rats, found that aspartame use was linked to leukemia and lymphoma (cancers of the blood cells and lymphatic system); however, in a review the FDA noted that the European Food Safety Authority indicated the conclusions were not supported by the data. In a major review, Magnuson and others noted that current use levels of aspartame, even by high users in special subgroups, remain well below the U.S. FDA established acceptable daily intake levels. Moreover, they conducted a critical review of

TABLE 4.11 Artificial sweeteners approved for use in the United States Name

Brand name

Times sweeter than sugar

Calories per typical serving

Acesulfame-K (potassium)

Sunett Sweet One

200

0

Aspartame

Equal NutraSweet

200

0

Neotame

*

7,000-13,000

0

Saccharin

Sweet’n Low Sweet Twin

200-700

0

Sucralose

Splenda

600

0

*No brand name yet

all carcinogenicity studies conducted on aspartame and found no credible evidence that aspartame is carcinogenic. The data from the extensive investigations into the possibility of neurotoxic effects of aspartame, in general, do not support the hypothesis that aspartame in the human diet will affect nervous system function, learning, or behavior. They concluded that the weight of existing evidence is that aspartame is safe at current levels of consumption as a nonnutritive sweetener. Other research by Lim and Gallus and their colleagues support this conclusion. Additionally, the Food and Drug Administration and other federal health agencies consider aspartame to confer no significant health risks, with the exception of individuals who have phenylketonuria (PKU), a rare genetic disease that limits the ability to metabolize phenylalanine. Such individuals are aware of their condition, and products containing aspartame must carry a warning on the label that the product contains phenylalanine. In a recent review, the Consumers Union concluded that all artificial sweeteners appear to be safe in small amounts. In particular, studies have raised no safety concerns at all about sucralose. However, the Consumers Union states several caveats. For one, high intakes of sugar alcohols, because they are not absorbed, may cause gastrointestinal distress. For another, individuals who may suffer from headaches or other symptoms from aspartame should avoid it. Some contend that use of sugar substitutes perpetuate cravings for sweet foods, and do nothing to promote good health. However, artificial sweeteners may be effective in weight-control programs, and their role will be discussed in chapter 11. Nevertheless, one should keep in mind that sugar free does not mean low-Calorie; check the food label for Calories per serving.

Why are complex carbohydrates thought to be beneficial to my health? To increase consumption of total carbohydrate in the diet while reducing the consumption of refined sugars, one must increase the consumption of complex carbohydrates. Some diet plans developed for health, such as the Pritikin program, recommend that

80 percent of the dietary Calories be supplied by carbohydrates, mostly complex and unrefined. More recently, the OmniHeart diet focuses on healthy carbohydrates, fats, and proteins. The OmniHeart diet plan includes the following tips for increasing consumption of healthier carbohydrates: • Eat 1–2 servings of fruit at every meal and have an extra fruit at breakfast. • Have 2–3 servings of vegetables at lunch and dinner. • Create a fruit and nut trail mix for snacks: 1⁄4 cup dried fruit with 1 oz unsalted nuts. • Use whole grains rather than refined grains as often as possible. • Select legumes for a carbohydrate and protein source several times a week. A diet rich in complex carbohydrates may reduce the percentage contribution from fats if excessive, which may confer significant health benefits, as noted in chapter 5. Complex carbohydrates are found primarily in starchy vegetables, whole grains, and legumes, but small amounts are also found in fruits. Whole-grain products are one of the best sources of healthy carbohydrates. As recently defined by the FDA, whole grains contain all three ingredients of a cereal grain, namely the outer bran and the inner germ and endosperm, and in the same proportion as found in nature (see figure 4.13). Seal noted that an increasing body of evidence from both epidemiological and prospective studies supports an inverse relationship between consumption of whole-grain foods and risk of coronary heart disease. For example, Djoussé and Gaziano found that those who ate the most whole-grain cereals over the course of the week had the greatest reduction in risk of heart failure. Over the course of approximately 20 years, those who consumed no whole-grain cereals weekly had a relative risk (RR) of heart failure of 1.0; those who consumed 2–6 servings weekly had a RR of 0.79, while those who consumed 7 or more servings had a RR of 0.71, which represents about a 22–28 percent lower risk of heart failure. When shopping, look for products with 100% Whole Wheat or 100% Whole Grains. Products labeled 100% wheat, multigrain, or stone ground may be made primarily from refined grains. The first

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(a)

Pectin: soluble fiber Cellulose in the skin: insoluble fiber

Endosperm (b) Bran layers (Hemicellulose: insoluble fiber)

Germ

Various forms of fiber. (a) The skin of an apple consists of the insoluble fiber cellulose, which provides structure for the fruit.The soluble fiber pectin "glues" the fruit cells together. (b) The outside layer of a wheat kernel is made of layers of bran— insoluble fiber—making this grain a good source of fiber. Fruits, vegetables, whole grains, and legumes such as beans are rich in fiber.

FIGURE 4.13

ingredient listed should be whole oats, whole rye, whole wheat, or other whole grains such as brown rice, bulgur, or oatmeal. Many vitamins, minerals, phytonutrients, antioxidants, and fiber may be lost in processing of whole grain to refined grain. Some, but not all, may be replaced during processing, so you may not get the synergistic health effects of the multiple nutrients. Current thinking supports the concept that the beneficial health effects of a diet rich in complex carbohydrates, which may be considered to be a low-glycemic-index diet, may be linked to several important attributes of such a diet, including the collective presence of various phytochemicals, vitamins, minerals, and dietary fiber. The health benefits of phytochemicals were discussed in chapter 2, while the benefits of vitamins and minerals will be covered in chapters 7 and 8. Most research relative to the healthful benefits of complex carbohydrates has focused on dietary fiber.

Why should I eat foods rich in fiber? The National Academy of Sciences, for the first time, recently established dietary recommendations for fiber. The daily AI for total fiber has been set at 14 grams per 1,000 Calories, or 38 grams for men and 25 grams for women up to age 50 and slightly lesser amounts thereafter. Recall that total fiber consists of both dietary fiber and functional fiber, and various specific forms of fiber are 156

C H A P T E R 4 Carbohydrates: The Main Energy Food

found in each category; some specific forms of fiber may be classified as both dietary and functional fiber. Although the Academy indicates that specific forms of fibers have properties that result in different physiological effects that may impact health, it did not feel that the evidence was sufficient to establish separate recommendations for each type of fiber. Nevertheless, some feel that the use of the water-solubility classifications system, as discussed previously, might be useful conceptually to illustrate the potential health benefits of certain forms of fiber. As noted earlier, dietary fiber is found naturally in various plant foods. Exactly how dietary fiber may be protective is not known, but several mechanisms have been proposed that may help in the prevention of certain forms of cancer, coronary heart disease, obesity, diabetes, hypertension, and various disorders of the gastrointestinal tract. Here are some of the theories relative to the potential health benefits of total fiber: 1. Water-insoluble fibers are considered to be those with the greatest effect on fecal bulk. Adding bulk to the contents of the large intestine stimulates peristalsis and speeds up the transit time of food through the intestines. The increased bulk has been shown to dilute any possible cancer-causing (carcinogens) that might attack cell walls, while faster transit diminishes the time carcinogens may have to act. Increased bulk—and peristalsis—also decreases the incidence rate of diverticulosis, an inflammatory disorder in the large intestine that may cause rupture, leading to serious complications. 2. Fiber-rich foods are low-glycemic-index foods, and may increase insulin sensitivity and prevention of weight gain. Fiber slows down gastric (stomach) emptying and thereby slows glucose absorption in the small intestine. The high viscosity of soluble fiber also decreases intestinal absorption. These effects may lead to better control of blood sugar and may also lengthen the sensation of fullness or satiety, which may be important to individuals on weight-loss diets. Fiberrich diets are frequently lower in fat and added sugars, and thus contain fewer Calories. So, high-fiber diets may be useful in the prevention or treatment of obesity and obesityrelated chronic diseases such as diabetes and hypertension. 3. Fiber, particularly gummy forms of water-soluble fiber like beta-glucans in oats, may bind with various substances in the gastrointestinal tract. Soluble fiber may bind with carcinogens so that they are excreted by the bowel. Soluble fibers may also bind with and lead to the excretion of bile salts, which contain cholesterol; normally bile salts are reabsorbed into the body, but excretion of bile salts, along with their cholesterol content, may help reduce serum cholesterol levels. This effect may decrease the risk of coronary heart disease. (Lower serum cholesterol levels decrease the risk of atherosclerosis, a major cause of heart disease.) 4. Some water-soluble fibers may be fermented in the large intestine to form short-chain fatty acids (SCFA). Wong and others noted that several of these SCFA are theorized to help prevent gastrointestinal disorders, cancer, and cardiovascular disease. Some act in the colon while others are absorbed into the blood, delivered to the liver, and may help decrease synthesis of cholesterol.

Although it may be illustrative to view the health benefits of fiber based on its water solubility, Joanne Slavin, a scholar on the health effects of dietary fiber, notes that it is difficult to generalize as to the physiological effects of fiber based on this classification system. For example, she notes that rice bran, which is devoid of soluble fiber, has been shown to reduce serum cholesterol, while recent research has also supported the effect of insoluble fiber to reduce the risk of heart disease. Thus, health benefits may be attributable to total fiber. Numerous studies, including major epidemiological studies and clinical trials, have investigated the effect of total fiber on reducing the risk or incidence of chronic diseases. Based on these studies, the National Academy of Sciences established the AI for total fiber because it may reduce the risk of coronary heart disease, and more recent research supports this concept. The Academy cited studies showing a beneficial effect of total fiber and a low-glycemic-index diet on other health problems, particularly in individuals with diabetes or hyperlipidemia, but the evidence was not as convincing as that for prevention of heart disease. Scientists have expressed different opinions regarding the use of the glycemic index, which is associated with fiber intake, as a means to design a diet for enhanced health. For example, in a meta-analysis of 45 studies, Livesey and others concluded that consumption of reduced glycemic response diets are followed by favorable changes in various health markers. Kendall and others also note that sufficient positive research findings have emerged to suggest that the glycemic index is an aspect of diet of potential importance in the treatment and prevention of chronic diseases, such as diabetes and cardiovascular disease. On the other hand, Howlett and Ashwell, summarizing a workshop on the glycemic index and health, reported that although lower GI and GL diets are beneficial for health in persons with impaired glucose metabolism, it is as yet unclear what they mean for healthy persons. Even though there may be debate over the usefulness of the glycemic index as a means to design a healthful diet for chronic diseases other than heart disease, consuming a fiber-rich diet is certainly prudent dietary behavior given that coronary heart disease is the number one cause of death in Western societies. And, although the National Academy of Sciences indicates that the relationship of fiber intake to other health problems is the subject of ongoing investigation and currently unresolved, there appear to be no adverse health effects associated with a fiber-rich or low-glycemic-index diet. Indeed a fiber-rich diet may be useful for other possible health benefits. Prevention of colon cancer has been one of the main theories underlying the promotion of a high-fiber diet. Rock has indicated that the relationship between dietary fiber intake and colorectal cancer has been inconsistent. However, she noted that no significant relationship between fiber intake (or major food sources of fiber) and risk for colorectal cancer was observed in a recently reported, large pooled analysis of several studies. Nevertheless, she notes limitations in epidemiological studies and indicates that the effect of increased dietary fiber intake on risk for colorectal cancer has not been adequately addressed in studies conducted to date. More research, including longer-term trials and higher levels of fiber intake are strategies that have been suggested to increase knowledge in this area.

As the different types of fiber appear to convey health benefits in different ways, a balanced intake of total fiber appears to be the best approach. The Academy notes that although the AI are based on total fiber, the greatest health benefits may come from the ingestion of cereal fibers and various viscous fibers, including gums and pectins, which are found in fruits and vegetables. Obtaining 25–38 grams of fiber daily is not difficult, but you have to eat more whole grains, fruits, vegetables, and legumes. Total fiber is listed on food labels. In particular, check food labels on breads and cereals, staples of the daily diet. Cleveland notes that on the average, Americans consume nearly seven servings of grain products per day but that only one of the seven is whole grain. Refined grains contain little or no fiber, whereas whole grains are usually rich in fiber. Some brands of bread contain 3 grams of fiber per slice, and only 50 Calories. Breakfast cereals may also be very high in fiber, some containing 10 or more grams per serving. The following general equivalencies may help you reach your goal: 3 fruits 3 vegetables 3 slices of whole-grain bread 1/2 cup beans 1 serving bran cereal Total

= = = = = =

6 grams fiber 9 grams fiber 6 grams fiber 7 grams fiber 9 grams fiber 37 grams fiber

According to one physician, a good way to see if you are eating enough fiber is to observe the buoyancy of your stool in the toilet. It should float, or at least appear flaky and break apart. If it sinks or does not break apart, you are not eating enough fiber. There appear to be few or no health disadvantages to a highfiber diet. As we shall see in chapter 8, there has been some concern that high-fiber diets could lead to increased losses of certain minerals, such as iron and zinc, but research has shown that such concerns are generally unwarranted if one follows the recommendations just given. Schneeman, discussing development of a scientific consensus on the importance of dietary fiber, notes that fiber serves as a marker for diets rich in plant foods, which provide additional benefits for maintaining health. Liebman notes that it is important to recognize that the health benefits attributed to dietary fiber may be associated with the form in which the fiber is consumed—as part of a whole, natural food containing other potential health-promoting nutrients such as vitamins and phytochemicals, rather than by consumption of a purified supplement form. This is in accord with the position stand of the American Dietetic Association, written by Marlett and others, on dietary fiber. Get more plant foods in your diet!

Do some carbohydrate foods cause food intolerance? About one in nine Americans may develop gastrointestinal distress when they consume dairy products containing substantial amounts of lactose, particularly milk. African-Americans are more likely to suffer lactose intolerance. Such individuals lack the enzyme lactase and hence cannot metabolize lactose in the digestive tract. The most common symptoms of lactose intolerance are gas, bloating, abdominal pain, and diarrhea, although headache and fatigue may www.mhhe.com/williams9

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also occur. Levey has noted that lactose intolerance may be the cause of runner’s diarrhea that often occurs during exercise. Individuals may be diagnosed as being lactose intolerant through a lactose tolerance test administered by a physician. One physician suggests, however, that a self-detection technique may be an effective approach. If you experience problems such as gas and diarrhea after consuming milk, abstain from all dairy products for 2 weeks and then evaluate the results. If the symptoms resolve, and then reoccur when you resume dairy food consumption, you may need to reduce the amount of lactose in your diet. Unfortunately, usually this means a reduced intake of dairy foods, which are considered to be the main dietary source of not only lactose, but calcium as well. Di Stefano and others indicated that lactose intolerance may prevent the achievement of adequate peak bone mass in young adults and may, therefore, predispose to severe osteoporosis. Calcium will be discussed in detail in chapter 8, but here are several strategies lactose-intolerant individuals may use to obtain adequate calcium intake. In a meta-analysis of well-designed studies, Savaiano and others indicated that symptoms of lactose intolerance may be minimal with small amounts of dairy foods, such as one cup or less. Consuming small amounts of milk over the course of the day may provide significant amounts of calcium. Reducedlactose milk is available, as are enzyme supplements, such as Lactaid, to help prevent indigestion. Other dairy products which have been fermented, such as yogurt, may be tolerated and provide a good calcium source. Cheese may also be a good source of calcium, although it is high in fat. Dark-green leafy vegetables, tofu, sardines, and salmon are all nondairy sources of calcium. Additionally, calcium supplements may be useful either in tablet form or as added to various foods, such as soy milk, rice milk, or orange juice. Wheat products may produce gastrointestinal symptoms comparable to lactose intolerance. The problem is not the wheat itself, but rather a protein called gluten. Gluten is found in wheat, rye, and barley that are the main constituents in most of the grain-based products we eat, such as cereals, breads, and pasta. Gluten intolerance represents a sensitivity to gluten; the immune system recognizes gluten as a foreign substance, but does not induce an allergic response. Some sports nutritionists note that simple gluten intolerance can be uncomfortable, but the symptoms are fleeting. Symptoms may vary from none to severe. Simple gluten intolerance could be problematic for endurance athletes. Alternate sources of carbohydrate, such as corn, potatoes, rice, soybeans, and similar foods, will be needed to replace grain-based foods. Gluten-free products are currently available in the marketplace. Gluten intolerance is also known as celiac (coeliac) disease, and in severe cases the gluten damages the lining of the small intestine. This leads to impaired nutrient absorption and a variety of nutrient-deficiency diseases, including weight loss, anemia, and osteoporosis. Celiac disease necessitates medical treatment and a lifelong gluten-free diet.

Does exercise exert any beneficial health effects related to carbohydrate metabolism? As noted in chapter 1, an appropriate exercise program may provide a variety of health benefits. In subsequent chapters, we shall 158

C H A P T E R 4 Carbohydrates: The Main Energy Food

detail the preventive health effects of exercise as related to several major health problems, such as obesity, diabetes, hypertension, and coronary heart disease. Some of these beneficial effects may be attributed to the effect of exercise on carbohydrate metabolism. Aging is normally associated with impaired glucose tolerance, which is associated with decreased insulin sensitivity. As shall be noted in chapter 10, such effects may contribute to metabolic aberrations associated with the development of coronary heart disease. However, Holloszy and Greiwe noted that these deleterious changes are not inevitable but are most likely related to a sedentary lifestyle and increased body weight. They found that athletic individuals 60 years and older had glucose tolerance and insulin action as good as young athletes nearly half their age. Exercise may enhance glucose tolerance and insulin sensitivity in several ways. In their review, Borghouts and Keizer noted that both acute and chronic exercise may affect blood glucose and insulin activity favorably. Up to two hours after an acute bout of exercise, glucose uptake is in part elevated due to insulin-independent mechanisms, probably involving an increase in GLUT-4 receptors in the cell membrane induced by exercise. Additionally, an exercise bout can increase insulin sensitivity for up to 16 hours afterwards. Chronic exercise training potentiates the effect of exercise on insulin sensitivity through multiple adaptations in glucose transport and metabolism. Frøsig and others suggested that improved insulin-stimulated glucose uptake associated with endurance training may result from hemodynamic adaptations, such as greater blood flow to the muscle, as well as increased cellular protein content of individual insulin signaling components and molecules involved in glucose transport and metabolism. Borghouts and Keizer conclude that exercise plays an important, if not essential, role in the prevention and treatment of impaired insulin sensitivity. Given the epidemic of obesity and type 2 diabetes in the United States and other industrialized nations, these beneficial effects of exercise on carbohydrate metabolism underscore its importance as preventive medicine. More details are presented in chapter 10.

Ke y C o n c e p t s 䉴 Added sugars should be limited in the diet.The maximal recom-

mended amount is 25 percent of daily energy intake, but some health professionals recommend lower amounts of about 10 percent. Intake of refined starches should also be limited. 䉴 An increase in the amount of total fiber to about 25–38 grams per day may be helpful as a protective measure against the development of heart disease, and possibly other chronic diseases. Consuming more whole grains, more fresh fruits, more nonstarchy vegetables, and more legumes, which are low-GI foods, will help ensure adequate fiber intake.

C h e c k f o r Yo u r s e l f Check the food labels of various breads for fiber content. Do some brands have significantly more than others? What impact could switching breads have on meeting the recommended daily fiber intake of 25 grams for females and 38 grams for males?

A P P L I C AT I O N If you are not currently eating enough fiber, try this experiment. Keep a record of your appetite and your bowel movements for a week or so, and then switch to a high-fiber diet, consuming fruits and vegetables, whole wheat and whole-grain breads, and other high-fiber foods as documented by food labels. Record

E X E R C I S E

approximate grams of total fiber consumed daily. Also record an increase (↑ ), decrease (↓), or no change (NC) for appetite, and record the number of daily bowel movements. Compare your appetite and bowel movements to the previous week. Did the high-fiber diet influence either?

Week 1 (Normal diet) Sunday

Monday

Tuesday

Wednesday Thursday

Friday

Saturday

Friday

Saturday

Breakfast Lunch Dinner Snacks Appetite Bowel Movement(s) Week 2 (High-fiber diet) Sunday

Monday

Tuesday

Wednesday Thursday

Breakfast Lunch Dinner Snacks Appetite Bowel Movement(s)

Review Questions—Multiple Choice 1. Which of the following statements relative to carbohydrate loading is false? (a) It is beneficial primarily for athletes involved in prolonged endurance events, such as the typical marathon (26.2 miles). (b) It involves the intake of about 500–600 grams of carbohydrate each day for several days prior to competition. (c) Research generally supports its effectiveness as a means of improving performance by helping to delay the onset of fatigue in the latter stages of prolonged exercise tasks.

(d) The major advantage of carbohydrate loading is the increased storage of glycogen in the adipose cells for use during exercise. (e) The increase in carbohydrate stores in the body may be detected by the increased body weight attributed to the water-binding effect of stored glycogen. 2. If you were to recommend to a runner a fluid replacement protocol, including carbohydrate content, for use during a marathon, which of the following would you not recommend?

(a) Use a 50–60 percent solution of galactose. (b) Provide approximately 10–15 grams of carbohydrate per feeding. (c) Provide feedings about every 15–20 minutes. (d) Limit the amount of fructose in the solution. (e) Choose a combination of carbohydrates.

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5.

6.

7.

8.

(c) hypoglycemia which stimulates insulin secretion and a return to normal blood glucose levels (d) hyperglycemia with a suppression of insulin and movement of blood glucose into the liver and muscle tissues (e) no change in blood glucose level Which of the following is not one of the potential health benefits of dietary fiber? (a) It may increase the bulk in the large intestine and dilute possible carcinogens. (b) It may increase the bulk in the large intestine and help speed up intestinal transit. (c) It may bind with carcinogens and help to excrete them. (d) It may help excrete bile salts and reduce serum cholesterol levels. (e) It may bind with certain minerals such as zinc and help to excrete them. Which of the following food exchanges is least likely to be high in dietary fiber? (a) vegetable (b) starch/bread (c) milk (d) fruit (e) legumes (meat exchange) What two tissues in the body store the most carbohydrate? (a) adipose and kidney (b) kidney and liver (c) liver and muscles (d) muscles and kidney (e) adipose and muscles Common table sugar is: (a) glucose.

(b) dextrose. (c) fructose. (d) sucrose. (e) maltose. 9. The total amount of carbohydrate, as a percentage of the daily calories, that represents the Acceptable Macronutrient Distribution Range (AMDR) for Americans and Canadians is: (a) 12–15. (b) 20–30. (c) 30–45. (d) 45–65. (e) 85–90. 10. The glycemic index represents: (a) the degree to which an athlete suffers from hypoglycemia. (b) the amount of glucose released into the blood in response to exercise. (c) the effect a particular food has on the rate and amount of increase in the blood glucose level. (d) the amount of stored glycogen in the muscle and liver. (e) the total amount of insulin released in response to food intake.

Answers to multiple-choice questions: 1. d; 2. a; 3. e; 4. b; 5. e; 6. c; 7. c; 8. d; 9. d; 10. c.

3. Which of the following statements relative to the intake of carbohydrates and physical performance is false? (a) If an individual has normal glycogen levels in the muscle and liver, carbohydrate feedings are usually not necessary if the exercise task is only about 60–90 minutes. (b) The intake of concentrated sugar solutions may actually impair performance if they lead to osmosis of fluids into the stomach and precipitate the feeling of gastric distress. (c) Carbohydrate intake may help delay the onset of fatigue in prolonged exercise by either preventing the early onset of hypoglycemia or delaying the depletion of muscle glycogen levels. (d) Carbohydrate intake prior to and during endurance exercise tasks lasting more than 2 hours may be helpful as a means of enhancing performance. (e) If consumed during exercise, it takes approximately 60–90 minutes for the carbohydrate to find its way into the muscle and be used as an energy source. 4. Following a meal high in simple carbohydrate, which of the following is most likely to occur in the next 1–2 hours? (a) suppression of insulin with a resultant hyperglycemia (b) hyperglycemia which stimulates insulin secretion followed by a possible hypoglycemia

Review Questions—Essay 1. Differentiate between dietary fiber and functional fiber, and contrast the new AI for total fiber with the current Daily Value (DV) used on food labels. 2. You have eaten a high-carbohydrate meal for lunch. Explain the digestion and metabolic fate of this carbohydrate

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over the next five hours, including an hour of running at the end of this time frame. 3. Explain three possible mechanisms of fatigue due to inadequate carbohydrate intake prior to and during the running of a 26.2 mile marathon.

C H A P T E R 4 Carbohydrates: The Main Energy Food

4. Identify athletes who might benefit from carbohydrate loading and present details of the dietary and exercise training protocol. 5. Discuss the possible health benefits associated with a diet rich in complex carbohydrates and low to moderate in refined carbohydrates.

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Stevenson, E., et al. 2006. Influence of highcarbohydrate mixed meals with different glycemic indexes on substrate utilization during subsequent exercise in women. American Journal of Clinical Nutrition 84:354–60. Stevenson, E., et al. 2005. Improved recovery from prolonged exercise following the consumption of low glycemic index carbohydrate meals. International Journal of Sport Nutrition and Exercise Metabolism 15:350–65. Tarnopolsky, M., et al. 2001. Gender differences in carbohydrate loading are related to energy intake. Journal of Applied Physiology 91:225–30. Tsintzas, K., et al. 2001. Phosphocreatine degradation in type I and type II muscle fibers during submaximal exercise in man: Effect of carbohydrate ingestion. Journal of Physiology 537:305–11. Utter, A., et al. 2007. Carbohydrate attenuates perceived exertion during intermittent exercise and recovery. Medicine & Science in Sports & Exercise 39:880–85. Utter, A., et al. 2005. Carbohydrate supplementation and perceived exertion during resistance training. Journal of Strength and Conditioning Research 19:939–43. Utter, A., et al. 2004. Carbohydrate supplementation and perceived exertion during prolonged running. Medicine & Science in Sports & Exercise 36:1036–41. Utter, A., et al. 2002. Effect of carbohydrate ingestion on ratings of perceived exertion during a marathon. Medicine & Science in Sports & Exercise 34:1779–84. Vandenberghe, K., et al. 1995. No effect of glycogen level on glycogen metabolism during high intensity exercise. Medicine & Science in Sports & Exercise 27:1278–83. van Loon, L., et al. 2001. The effects of increasing exercise intensity on muscle fuel utilisation in humans. Journal of Physiology 536:295–304. van Loon, L., et al. 2000. Maximizing postexercise muscle glycogen synthesis: Carbohydrate supplementation and the application of amino acid or protein hydrolysate mixtures. American Journal of Clinical Nutrition 72:106–11. Venables, M., et al. 2005. Erosive effect of a new sports drink on dental enamel during exercise. Medicine & Science in Sports & Exercise 37:39–44. von Fraunhofer, J., and Rogers, M. 2005. Effects of sports drinks and other

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Weltan, S. M., et al. 1998. Influence of muscle glycogen content on metabolic regulation. American Journal of Physiology 274:E72–E82. Weltan, S. M., et al. 1998. Preexercise muscle glycogen content affects metabolism during exercise despite maintenance of hyperglycemia. American Journal of Physiology 274:E83–E88. Williams, C., et al. 1992. The effect of a high carbohydrate diet on running performance during a 30-km treadmill time trial. European Journal of Applied Physiology 65:18–24. Winnick, J., et al. 2005. Carbohydrate feedings during team sport exercise preserve physi-

C H A P T E R 4 Carbohydrates: The Main Energy Food

cal and CNS function. Medicine & Science in Sports & Exercise 37:306–15. Wong, J., et al. 2006. Colonic health: Fermentation and short chain fatty acids. Journal of Clinical Gastroenterology 40:235–43. Wu, C., and Williams, C. 2006. A low glycemic index meal before exercise improves endurance running capacity in men. International Journal of Sport Nutrition and Exercise Metabolism 16:510–27. Yaspelkis, B., et al. 1993. Carbohydrate supplementation spares muscle glycogen during variable-intensity exercise. Journal of Applied Physiology 75:1477–85.

Fat: An Important Energy Source During Exercise

K E Y

adipokines 178 alpha-linolenic acid 174 angina 192 apolipoprotein 175 arteriosclerosis 192 atherosclerosis 192 beta-oxidation 179 carnitine 180 cholesterol 172 chylomicron 175 cis fatty acids 169 conjugated linoleic acid (CLA) 174 coronary artery disease 191 coronary heart disease 191

CHAPTER L E A R N I N G

T E R M S

O B J E C T I V E S

After studying this chapter, you should be able to: 1. List the different types of dietary fatty acids and identify general types of foods in which they are found. 2. Calculate the approximate amount, in grams or milligrams, of total fat, saturated fat, and cholesterol that should be included in your daily diet. 3. Describe how dietary fat is absorbed, how it is distributed in the body, and what its major functions are in human metabolism. 4. Explain the role of fat in human energy systems during exercise and how endurance exercise training affects exercise fat metabolism. 5. Explain the theory underlying the role of increased fat oxidation to enhance prolonged aerobic endurance performance. 6. List the various dietary fat strategies and dietary supplements that have been investigated as a means of enhancing exercise performance, and highlight the major findings. 7. Describe the proposed process underlying the development of atherosclerosis and cardiovascular disease, including the role that dietary fat and cholesterol may play in its etiology. 8. List and describe at least 8 of the 10 dietary strategies that are proposed to help treat or prevent the development of atherosclerosis and cardiovascular disease. 9. Explain the role of exercise as a means of helping prevent the development of atherosclerosis and cardiovascular disease.

FIVE

coronary occlusion 192 coronary thrombosis 192 eicosanoids 178 ester 168 fat loading 183 fat substitutes 171 fatty acids 168 glycerol 169 hidden fat 169 HDL (high-density lipoproteins) 177 ischemia 192 ketones 179 LDL (low-density lipoproteins) 177 lecithin 173 linoleic acid 174 lipids 168 lipoprotein 175 lipoprotein (a) 177 medium-chain triglycerides (MCTs) 175 monounsaturated fatty acid 169 myocardial infarct 192 omega-3 fatty acids 169 omega-6 fatty acids 169 partially hydrogenated fats 169 phosphatidylserine 186 phospholipids 173 plaque 192 polyunsaturated fatty acid 169 saturated fatty acid 169 trans fatty acids 169 triglycerides 168 VLDL (very low-density lipoproteins) 177 167

Introduction From a health standpoint, dietary fat is the nutrient of greatest concern to the American Heart Association because excessive consumption of certain types of fat has been associated with the development of coronary heart disease. Excessive consumption of dietary fat may also contribute to the development of obesity, a risk factor for several other chronic diseases, such as diabetes. Thus, one of the major recommendations advocated in Healthy People 2010 for a healthier diet is to reduce the amount of dietary fat intake to a reasonable level. Part of the rationale for this recommendation and some general guidelines for implementing it are presented in this chapter, but additional information may also be found in chapters 2 and 11. We need some fat in our diet. Despite its potential health hazards when consumed in excess, dietary fat contains several essential nutrients that serve a variety of important functions in human nutrition. The National Academy of Sciences recently set an Acceptable Macronutrient Distribution Range (AMDR) for total fat of 20–35 percent of daily energy intake. Because some types of fat may confer various health benefits, the Academy also set Adequate Intakes (AI) for several fatty acids. Moreover, in their position statement regarding nutri-

tion and athletic performance, the American Dietetic Association, Dietitians of Canada, and the American College of Sports Medicine noted that, overall, diets should provide moderate amounts of energy from fat (20 to 25 percent of energy) and that there is no health or performance benefit to consuming a diet containing less than 15 percent energy from fat. For the endurance athlete, one of the most important functions of fat is to provide energy during exercise, and researchers have explored a variety of techniques in attempts to improve

Dietary Fats

Fatty acid

endurance performance by increasing the ability of the muscle to use fat as a fuel. To clarify the role of dietary fat in health and its possible relevance to sports, this chapter presents information on the basic nature of dietary fats and associated lipids, the metabolic fate and physiological functions of fats and cholesterol in the body, the role of fat as an energy source during exercise, the use of various dietary practices or ergogenic aids in attempts to improve fat metabolism and endurance performance, and possible health problems associated with excessive dietary fat.

Glycerol

Fatty acid

What are the different types of dietary fats? What we commonly call fat in our diet actually consists of several substances classified as lipids. Lipids represent a class of organic substances that are insoluble in water but soluble in certain solvents like alcohol or ether. The three major dietary lipids of importance to humans are triglycerides, cholesterol, and phospholipids. All three have major functions in the body.

What are triglycerides? The triglycerides, also known as the true fats or the neutral fats, are the principal form in which fats are eaten and stored in the human body. Triglycerides are composed of two different compounds—fatty acids and glycerol. When an acid (fatty acid) and an alcohol (glycerol) combine, an ester is formed, the process being known as esterification. (Three fatty acids are attached to 168

Fatty acid

F I G U R E 5 . 1 Structure of a triglyceride.Three fatty acids combine with glycerol to form a triglyceride.

each glycerol molecule.) Figure 5.1 is a diagram of a triglyceride. Another term used for triglyceride is triacylglycerol. Some triglycerides may be modified commercially to contain only two fatty acids, known as diglycerides, or diacylglycerols. Fatty acids, one of the components of fat, are chains of carbon, oxygen, and hydrogen atoms that vary in length and in the degree of saturation of carbon with hydrogen. Short-chain fatty acids (SCFAs)

C H A P T E R 5 Fat: An Important Energy Source during Exercise

contain fewer than six carbons, medium-chain fatty acids (MCFAs) have six to twelve carbons, and long-chain fatty acids (LCFAs) have fourteen or more carbons. Fatty acids may be saturated or unsaturated. A saturated fatty acid contains a full quota of hydrogenated ions so that all of its carbon bonds are full; saturated fats such as butter are solid at room temperature. Carbon molecules in unsaturated fatty acids may incorporate more hydrogen because they have some unfilled bonds, or double bonds. These unsaturated fatty acids may be classified as monounsaturated, having a single double bond and capable of incorporating two hydrogen ions, and polyunsaturated, having two or more double bonds and capable of incorporating four or more hydrogen ions; monounsaturated and polyunsaturated fats as oils are liquid at room temperature. Polyunsaturated fatty acids are further identified according to the location of the first carbon double bond from the last, or omega, carbon. Omega-3 and omega-6 fatty acids are the two major types, and the numeric represents the location of the first double bond. Other terminology to identify these two fatty acids are ω-3 and n-3, and ω-6 and n-6. Adequate amounts of omega-3 and omega-6 fatty acids may confer health benefits, as noted later in the chapter. At room temperature, saturated fats are usually solid, while unsaturated fats are usually liquid. Partially hydrogenated fats or oils have been treated by a process that adds hydrogen to some of the unfilled bonds, thereby hardening the fat or oil. In essence, the fat becomes more saturated. During the hydrogenation process, the normal position of hydrogen ions at the double bond is on the “same side” (cis). This is known as a cis fatty acid, but if partially hydrogenated so that hydrogen ions are on opposite sides of the double bond, it results in a trans fatty acid. Figure 5.2 represents the structural difference between a saturated, a monounsaturated, a polyunsaturated (cis and trans), and an omega-3 polyunsaturated fatty acid. The health implications of these different types of fats are discussed later in this chapter. In general though, excess intake of saturated and trans fatty acids is associated with increased health risks, whereas adequate intake of monounsaturated, polyunsaturated, and omega-3 fatty acids may be associated with neutral or some beneficial health effects. Bell and others noted recently that food technology is evolving to create structured triglycerides that may possess health benefits. Glycerol is an alcohol, a clear, colorless syrupy liquid. It is obtained in the diet as part of triglycerides, but it also may be produced in the body as a by-product of carbohydrate metabolism. On the other hand, glycerol can be converted back to carbohydrate in the process of gluconeogenesis in the liver.

What are some common foods high in fat content? The fat content in foods can vary from 100 percent, as found in most cooking oils, to minor trace amounts, less than 5–10 percent, as found in most fruits and vegetables. Some foods obviously have a high-fat content: butter, oils, shortening, mayonnaise, margarine, and the visible fat on meat. However, in other foods the fat content may be high but not as obvious. This is known as hidden fat. Whole milk, cheese, nuts, desserts, crackers, potato chips, and a wide variety of commercially prepared foods may contain considerable amounts of hidden fat. For example, a 5-ounce baked potato contains 145 Calo-

H H H H OH R C C C C C O H H H H Saturated fatty acid

H H H H H OH R C C C C C C O H

H H

Monounsaturated fatty acid

H H H H H H OH R C C C C C C C O H

H

Polyunsaturated fatty acid

H

H H

H H OH

R C

C C

C C C O

H

H H

Unsaturated fatty acid (cis)

H

H H OH

H

R C

C C

H

H

C C C O H H

Unsaturated fatty acid (trans)

OH

H

H H

H

H C

C C

C R C O

H

H

Omega-3 fatty acid

F I G U R E 5 . 2 Structural differences between saturated, monounsaturated, and polyunsaturated fatty acids (including the cis and trans forms) and the omega-3 fatty acid. Note there is a single double bond between carbon atoms in the monounsaturated fatty acid and two or more in the polyunsaturated fatty acid. In the omega3 fatty acid, the double bond is located three carbons from the last, or omega, carbon.The R represents the radical, or the presence of many more C–H bonds. In the trans configuration, one of the hydrogen ions is moved to the opposite side.

ries with about 3 percent fat, while a 5-ounce serving of potato chips contains 795 Calories, over 60 percent of them from fat. In general, animal foods found in the meat and milk groups are high in fat, particularly saturated fat. Hamburger meat contributes the most saturated fat to the typical American diet. However, careful selection and preparation of foods in these groups will considerably reduce fat content. The percentage of fat in meat and milk products may vary considerably; beef, pork, and cheese products usually contain considerable amounts of fat, up to 70 percent or more fat Calories. The meat and dairy industries are responding to dietary modifications by many Americans and are making low-fat red meats and low-fat cheeses available to consumers. For example, 3 ounces of beef eye of round or pork tenderloin contain about 140 Calories, 4 grams of total fat, and 1.5 grams of saturated fat; both cuts of meat contain fewer than 30 percent of their Calories as fat. Lean cuts of poultry and fish have much lower levels of fat. Trimming the fat from meats or removing the skin from poultry drastically reduces the fat content. Some fish, such as flounder and tuna, are remarkably low in fat while others, such as salmon and mackerel, are higher in total fat content but contain greater amounts of omega-3 fatty acids. Look for foods in the very lean meat exchange list in appendix E. In the milk group, whole milk contains about 8 grams of fat per cup; skim milk contains about 0.5–1.0 grams, which is much less than whole milk. Low-fat cheese alternatives containing soy or rice are available. www.mhhe.com/williams9

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How do I calculate the percentage of fat Calories in a food?

Small amounts of trans fatty acids are found naturally in beef, butter, and milk, but deep-fried foods and commercially prepared products, particularly stick margarine and snack foods such as chips, cakes, and cookies, may contain substantial amounts. The health risks associated with trans fatty acids are discussed later in this chapter. Most plant foods, such as vegetables, fruits, beans, and natural whole-grain products, generally are low in fat content, and the fat they do contain is mostly unsaturated. On the other hand, some plant foods, such as nuts, seeds, and avocados, are very high in fat, but again primarily unsaturated fats. However, coconuts and palm kernels are extremely high in both total and saturated fats. All fats contain a mixture of saturated, monounsaturated, and polyunsaturated fatty acids. Since later in this chapter we discuss some health implications relating to the types of fats we eat, figure 5.3 presents an approximate percentage of the amount of saturated, monounsaturated, and polyunsaturated fatty acids found in some common oils and fats. Several high-content sources for each of the various types of fatty acids are noted.

Saturated Fatty Acids

It is important to realize that a product advertised as 95 percent fat free (or only 5 percent fat) may contain a considerably higher percentage of its Calories as fat: The advertised percentage refers to the weight of the product, not its caloric content. The product may contain a considerable amount of water, which contains no Calories. Thus, luncheon meat advertised as 95 percent fat free may actually contain more than 40 percent of its Calories from fat depending upon the water weight. Foods with a high water content contain even higher percentages of fat Calories. A striking example is whole milk, which is only 3.5 percent fat by weight; however, one glass of milk contains about 150 Calories and 8 grams of fat, which accounts for 48 percent of the caloric content (8 × 9 ⫽ 72; 72/150 ⫽ 48). Even low-fat milk (2 percent fat) contains about 37 percent fat Calories. If you want to calculate the percentage of fat calories in most foods you eat, you can get the information you need from the

Monounsaturated Fatty Acids

Polyunsaturated Fatty Acids

Primarily Trans Fatty Acids

Saturated Fatty Acids Coconut oil **

Butter Palm oil Lard or beef fat Monounsaturated Fatty Acids Olive oil Canola oil* Peanut oil Soybean oil* Polyunsaturated Fatty Acids Safflower oil Sunflower oil Corn oil Trans Fatty Acids Tub margarine Stick margarine Shortening 0

20

40

60

80 100 0

20

40

60

80 100 0

20

40

60

80 100 0

20

40

60

80 10

Note that fats are also typically rich in monounsaturated fatty acids (40 to 50% of total fatty acids). *Rich source of the omega-3 fatty acid alpha-linolenic acid (7% and 12% of total fatty acid content for soybean oil and canola oil, respectively). **Natural trans fatty acids in butter are not harmful.

Saturated, monounsaturated, polyunsaturated, and trans fatty acid composition of common fats and oils (expressed as % of all fatty acids in the product.

FIGURE 5.3

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C H A P T E R 5 Fat: An Important Energy Source during Exercise

Nutrition Facts Serving Size 1 Link (45g) Servings Per Container 10 Amount Per Serving

Calories 140 Calories from Fat 120 % Daily Value*

Total Fat 13g 20% Saturated Fat 5g 23% Trans Fat 0g ** Cholesterol 20mg 7% Sodium 420mg 17% 1% Total Carbohydrate 2g Dietary Fiber 0g 0% Sugars 1g Protein 5g Vitamin A 0% • Vitamin C 0% Calcium 0% • Iron 2%

F I G U R E 5 . 4 Reading labels helps locate hidden fat.Who would think that wieners (hot dogs) can contain about 85 percent of energy content as fat? Looking at the hot dog itself does not suggest that almost all its energy content comes from fat, but the label shows otherwise. Do the math: 120/140 Calories ⫽ 0.85 or 85 percent.

*Percent Daily Values are based on a 2,000 calorie diet. **Intake of trans fat should be as low as possible.

food label, which will include the total Calories and the Calories from fat; additional mandatory information is the total fat, saturated fat, and trans fatty acid content. The label optionally may list the Calories from saturated fat and the amounts of polyunsaturated and monounsaturated fat. Figure 5.4 presents a food label to help illustrate the hidden fat in a hot dog (wiener). If you do not have a food label, then you will need to know the Calories and grams of fat for the food. Both of these values can be obtained from a food composition table found in most basic nutrition texts or online. Table 5.1 presents the methods for calculating the percent of fat Calories and percent of saturated fat Calories from either a food label or food composition table. Table 5.2 represents the percentage of food energy that is derived from fat in some common foods; the percentages are indicated for both total fat and saturated fat. Additional information is presented in chapter 11, where the focus is on reducing high-fat foods in the diet as a means to Calorie control. www.ars.usda.gov/ba/bhnrc/ndl To obtain the total Calories and grams of fat for a given food, click on search and enter the name of the food.The amounts of all types of fats and cholesterol, as well as numerous other nutrients, are also provided.

What are fat substitutes? Fat substitutes, or fat replacers, are supposedly designed to provide the taste and texture of fats, but without the Calories (9 Calories per gram), saturated fat, or cholesterol. They are found in many normally high-fat products, such as ice cream, that are marketed as fat free. Fat substitutes may be manufactured from carbohydrate, protein, or fats. Although a number of fat substitutes are under development, the following are commonly used. Some carbohydrates, such as starches and gums, provide thickness and structure and are useful as fat substitutes. Guar gum, gum arabic, and cellulose gel are examples. Oatrim, made from oats, is being used to replace fat in milk. Depending on the form used, the

TABLE 5.1

Calculation of the percentage of Calories in foods that are derived from fat

Method A. Data from food label Amount per serving Calories ⫽ 90 Calories from fat ⫽ 30 To calculate percentage of food Calories that consists of fat, simply divide the Calories from fat by the Calories per serving and multiply by 100 to express as a percent. 30/90 ⫽ 0.33 0.33 × 100 ⫽ 33 percent fat Calories Method B. Data from food composition table Amount per serving Calories ⫽ 90 Total fat, grams ⫽ 8 Saturated fat, grams ⫽ 3 To calculate percentage of food Calories that consists of total fat or saturated fat, use the caloric value for fat of 1 gram ⫽ 9 Calories. Total fat ⫽ 8 grams Total fat Calories ⫽ 8 grams × 9 Calories/gram ⫽ 72 Calories Use the same procedure as in Method A. 72/90 ⫽ 0.80 0.80 × 100 ⫽ 80 percent fat Calories Saturated fat ⫽ 3 grams Saturated fat Calories ⫽ 3 grams × 9 Calories/gram ⫽ 27 Calories 27/90 ⫽ 0.30 0.30 × 100 ⫽ 30 percent saturated fat Calories

caloric content may range from 0–4 Calories per gram. Simplesse is manufactured from milk or egg protein by a microparticulation process so that it has the taste and texture of fat. The caloric value of Simplesse is only 1.3 Calories per gram. The use of Simplesse has been approved by the FDA. Salatrim, which is an acronym for shortand long-chain fatty acid triglyceride molecule, is a modified fat containing only 5 Calories per gram. Olestra is an ester of sucrose with www.mhhe.com/williams9

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TABLE 5.2

Percentage of total fat Calories and saturated fat Calories in some common foods* % Calories total fat

Food

% Calories saturated fat

Food

Meat group Bacon Beef, lean and fat (untrimmed) Beef, lean only (trimmed) Hamburger, regular Chicken, breast (with skin) Chicken, breast (without skin) Luncheon meat (bologna) Salmon Flounder, tuna Egg, white and yolk Egg, white

80 70

30 32

35

15

62 35

29 11

19

5

82

35

37 8 67 0

7 2 22 0

45 5 74 56

28 2.5 47 35

49 31 29

28 18 14

4 28

85.0

>29.0

Cancel all athletic activities

Modifications of the recommendations on climatic heat stress in exercising children and adolescents proposed by the American Academy of Pediatrics Committee on Sports Medicine and Fitness.

C H A P T E R 9 Water, Electrolytes, and Temperature Regulation

heat stress, possibly because temperature-regulating centers in the brain are irreversibly damaged. The transfer of heat from the core to the skin becomes impaired and the body temperature rises faster. Acclimatization One of the more important factors determining an individual’s response to exercise in the heat is degree of acclimatization, which is discussed on the following pages. Although some individuals may be susceptible to heat illnesses, all individuals who exercise under warm or hot environmental conditions may benefit from the following recommendations.

How can I reduce the hazards associated with exercise in a hot environment? In his review, Eichner indicated that the best treatment for heat illness is prevention. The following list represents a number of guidelines which, if followed, will reduce considerably your chances of suffering heat injury. 1. Check the temperature and humidity conditions before exercising. Even if the dry temperature is only 65–75°F, a high humidity will increase the heat stress. Warm, humid conditions cause fatigue sooner, so slow your pace or shorten your exercise session. As noted previously, local news stations and several Websites may provide information on heat stress conditions. 2. Exercise in the cool of the morning or evening to avoid the heat of the day. 3. Exercise in the shade, if possible, to avoid radiation from the sun. If you run in the sun, wear an appropriate sunscreen to prevent sun damage to the skin. 4. Wear sports clothing designed for exercise in the heat, such as CoolMax type material. Clothing should be loose to allow air circulation, white or a light color to reflect radiant heat, and porous to permit evaporation. Do not wear a hat if running in the shade, but wear a loose hat if running in the sun. 5. If you are running and there is a breeze, plan your route so that you are running into the wind during the last part of your run. The breeze will help cool you more effectively at the time you need it most. 6. Hyperhydrate if you plan to perform prolonged, strenuous exercise in the heat. In general, drink about 16 ounces of fluid 30–60 minutes prior to exercising. 7. Drink cold fluids periodically. For a long training run, plan your route so that it passes some watering holes, such as gas stations or other sources of water. Alternatively, you may purchase a special water-bottle belt or backpack that will help you carry your own water supply. Take frequent water breaks, consuming about 6–8 ounces of water every 15 minutes or so. 8. Replenish your water daily. Keep a record of your body weight. For each pound you lose, drink about 20–24 ounces of fluid. Your body weight should be back to normal before your next workout. 9. Replenish lost electrolytes (salt) if you have sweated excessively. Put a little extra salt on your meals and eat foods high in potassium, such as bananas and citrus fruits.

10. Avoid excessive intake of protein, as extra heat is produced in the body when protein is metabolized. This may contribute slightly to the heat stress. 11. Avoid dietary supplements containing ephedrine. Ephedrine is a potent stimulant that can increase metabolism and heat production, leading to an increased body temperature during exercise in warm environmental conditions and predisposing to heat illness. 12. If you drink caffeinated beverages, check your responses. Current research indicates that caffeinated beverages may not affect hydration status or temperature regulation during exercise. However, some individuals may respond differently to caffeine intake. Caffeine can increase heat production at rest, which could raise the body temperature before exercise. 13. Because alcohol is a diuretic, excess amounts should be avoided the night before competition or prolonged exercise in the heat. 14. If you are sedentary, overweight, or aged, you are less likely to tolerate exercise in the heat and should therefore use extra caution. 15. Be aware of the signs and symptoms of heat exhaustion and heat stroke, as well as the treatment for each. Chills, goose pimples, tingling arms, dizziness, weakness, fatigue, mental disorientation, nausea, and headaches are some symptoms that may signify the onset of heat illness. Stop activity, get to a cool place, and consume some cool fluids. 16. Do not exercise if you have been ill or have had a fever within the last few days. 17. Check your medications. Some medications, such as antihistamines used to treat cold symptoms, may block sweat production. Drugs used to treat high blood pressure, such as beta-blockers and calcium-channel blockers, may impair skin blood flow and decrease heat loss from the body. 18. If you plan to compete in a sport held under hot environmental conditions, you must become acclimatized to exercise in the heat. www.gssiweb.com The Gatorade Sports Science Institute (GSSI) provides very useful information on a wide variety of topics in sports nutrition, especially information relative to proper hydration practices to help enhance performance and prevent heat illness when exercising in the heat.

How can I become acclimatized to exercise in the heat? It is a well-established fact that acclimatization to the heat will help increase performance in warm environments as compared with an unacclimatized state. Simply living in a hot environment confers a small amount of acclimatization. Physical training, in and of itself, provides a significant amount of acclimatization, possibly up to 50 percent of that which can be expected, and also increases body-water levels. However, neither of these two adjustments, either singly or together, can prevent the deterioration of exercise performance in the heat by an unacclimatized individual. Thus, a period of active acclimatization is necessary to optimize performance when exercising in the heat. www.mhhe.com/williams9

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The technique of acclimatization is relatively simple. Simply cut back on the intensity or duration of your normal activity when the hot weather begins. Do not avoid exercise in the heat completely, but after an initial reduction in your activity level, increase it gradually. For example, if you were running five miles a day, cut your distance back to two to three miles in the heat; if you need to do five a day, do the remaining miles in the evening. Eventually build up to three, four, and five miles. The acclimatization process usually takes about 10 to 14 days to complete. However, even when acclimatized, an athlete’s endurance capacity in the heat, particularly with high humidity, still will be less than under cooler conditions. If you live in a cool climate, like New England, and want to compete in a marathon in Florida in January, how do you become acclimatized? Exercising indoors at a warmer temperature will help. Extra layers of clothes can help prevent evaporation and build a hot, humid microclimate around your body. Research has shown that this technique can provide a degree of acclimatization. However, this is advisable only in cool weather and should not be attempted under hot conditions. Wearing a sweat suit or rubberized suit while exercising in the heat may precipitate heat illness. Moreover, even in a cool environment this technique may cause heat injury. Again, be wary of the symptoms of impending heat illness. Repeated exposure to a high core temperature during exercise helps the body make the following important adjustments during acclimatization to the heat. The ACSM indicates 10–14 days of exercising in the heat will improve heat acclimatization in adults. Bar-Or notes that heat acclimatization in children takes several weeks. Here are some of the benefits of heat acclimatization that will help improve performance and reduce the risk of heat stroke and heat exhaustion. 1. Total body water increases considerably, which usually includes increased plasma volume. Blood vessels may conserve more sodium, which tends to hold plasma water. This occurs because the blood vessels conserve more protein and sodium, which tend to hold water. 2. The increased blood volume allows the heart to pump more blood per beat, so the stress on the heart is reduced. 3. When volume increases, more blood flows to the muscles and skin. The muscles receive more oxygen and skin cooling increases, improving endurance performance. 4. Less muscle glycogen may be used as an energy source at a given rate of exercise, sparing this energy source in endurance events. 5. The sweat glands hypertrophy and secrete about 30 percent more sweat, allowing for greater evaporative heat loss. 6. Body salt losses decrease. The amount of salt in the sweat decreases considerably; evaporation becomes more efficient and electrolytes are conserved. Sweat losses of calcium, magnesium, copper, zinc, and iron also decrease with acclimatization. 7. Sweating starts at a lower core temperature, leading to earlier cooling. 8. The core temperature will not rise as high or as rapidly as in the unacclimatized state. 9. The psychological feeling of stress is reduced at a given exercise rate. 390

Higher

Sweating Blood volume

Core temperature Heart rate Sodium loss Lower

Day 1

Day 14 Days of acclimatization

F I G U R E 9 . 1 3 Changes with acclimatization. Acclimatization to the heat for 7 to 14 days will lead to an increase in the blood volume and the ability to sweat. For a standardized exercise task in the heat, these changes will lead to a lower heart rate, less sodium loss, and a lower core temperature. These changes will lead to improved exercise performance in the heat.

In essence, as illustrated in figure 9.13, these changes increase the ability of the body to dissipate heat with less stress on the cardiovascular system. The end result is a more effective bodytemperature control and improved performance when exercising in the heat. These adaptations may be maintained by exercising in the heat several days per week but are lost in about 7–10 days in a cool environment. If you are interested in learning more about acclimatization, consult the review by Sawka and Young.

Ke y C o n c e p t s 䉴 Heat injuries, of which heat stroke is potentially the most

dangerous, may be due to increased body core temperature, loss of body fluids, or loss of electrolytes. Some individuals, such as the obese, are more susceptible to heat injury. 䉴 The general treatment for heat-stress illnesses is to rest, drink cool liquids, and cool the body. Rapid body cooling is essential in cases of heat stroke. 䉴 If you exercise in the heat, you should be aware of signs of impending heat injury, such as chills, dizziness, and weakness.You should also be aware of methods to reduce heat gain to the body and methods to facilitate heat loss. 䉴 Acclimatization to exercise in the heat takes about 10–14 days, but endurance capacity in the heat is still limited somewhat even when one is fully acclimated.

Health Aspects: High Blood Pressure What is high blood pressure, or hypertension? Everybody has blood pressure. Without it we would not be able to sustain body metabolism. Simply speaking, blood pressure is the force that the blood exerts against the blood vessel walls.

C H A P T E R 9 Water, Electrolytes, and Temperature Regulation

Although pressure is present in all types of blood vessels, the arterial blood pressure is the one most commonly measured and most important to our health. Blood pressure is usually measured by a sphygmomanometer, which records the pressure in millimeters of mercury (mmHg) (see figure 9.14). Blood pressure readings are given in two numbers, for example 120/80 mmHg. The higher number represents the systolic phase, when the heart is pumping blood through the arteries. The lower number represents the diastolic phase, when the heart is resting between beats and blood is flowing back into it. Two important determinants of blood pressure are the volume of blood in the circulation and the resistance to blood flow, known as peripheral vascular resistance. High blood pressure, also known as hypertension (hyper = high; tension = pressure), is known as a silent disease. Israili and others recently noted that hypertension affects approximately 1 billion individuals worldwide. At least 65 million individuals in the United States have hypertension. Surprisingly, Hansen and others estimated that about 2 million American youth have high blood pressure, which they associated with rising levels of obesity

in children. The Consumers Union referred to high blood pressure as an uncontrolled epidemic, noting that most individuals with hypertension do not have it under control. One reason is that nearly a third do not even know they are hypertensive, mainly because it has no outstanding symptoms. Some general symptoms include headaches, dizziness, and fatigue, but since they can be caused by a multitude of other factors, they may not be recognized as symptoms of high blood pressure. Although a great deal of research about the cause of high blood pressure has been conducted, the exact cause is unknown in about 90 percent of all cases. In these cases, the condition is known as essential hypertension, which cannot be cured. High blood pressure is dangerous for several reasons. The heart must work much harder to pump the extra blood volume or to overcome the peripheral vascular resistance. This normally leads to an enlarged heart. Over time the increase in heart size becomes excessive and the efficiency of the heart actually decreases, making it more prone to a heart attack. Second, high blood pressure may directly damage the arterial walls. It is thought to be a major contributing factor in the development of atherosclerosis and a predisposing

1. No sound is heard because there is no blood flow when the cuff pressure is high enough to keep the brachial artery closed. 2. Systolic pressure is the pressure at which a Korotkoff sound is first heard. When cuff pressure decreases and is no longer able to keep the brachial artery closed during systole, blood is pushed through the partially opened brachial artery to produce turbulent blood flow and a sound. The brachial artery remains closed during diastole. 3. As cuff pressure continues to decrease, the brachial artery opens even more during systole. At first, the artery is closed during diastole, but, as cuff pressure continues to decrease, the brachial artery partially opens during diastole. Turbulent blood flow during systole produces Korotkoff sounds, although the pitch of the sounds changes as the artery becomes more open. 4. Diastolic pressure is the pressure at which the sound disappears. Eventually, cuff pressure decreases below the pressure in the brachial artery and it remains open during systole and diastole. Nonturbulent flow is reestablished and no sounds are heard.

Degree to which brachial artery is open during:

300

Systole Diastole

250 Starting with a high pressure No sound

200 150 Systolic pressure (120 mm Hg) Diastolic pressure (80 mm Hg)

Korotkoff sounds

100 50 0

Sound first heard

Sound disappears No sound

1

Blocked

2

3

Blocked or partially open

4 Open

Arm

Pressure cuff Elbow

FIGURE 9.14

Blood pressure measurement

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factor to coronary disease and stroke. High blood pressure is itself a disease and is also involved in the etiology of other diseases. It is one of the primary risk factors for heart disease and stroke. The National Research Council has noted that any definition of high blood pressure is arbitrary. Traditionally, physicians have used elevations in diastolic blood pressure as the basis for their diagnosis, but the Joint National Committee on Detection, Evaluation, and Treatment of High Blood Pressure (JNCDET) of the National Institutes of Health, in its recent classification of blood pressure for adults age 18 years and older, includes both systolic and diastolic pressures. The classification system is presented in table 9.11.

cases of mild to moderate hypertension. The Canadian Hypertension Education Program emphasizes the point that lifestyle modifications are the cornerstone of antihypertensive therapy.

What dietary modifications may help reduce or prevent hypertension? How much and what you eat may influence your blood pressure. The following are the key points to help reduce or prevent hypertension.

www.americanheart.org Consult the American Heart Association Website for your personal risk factor assessment for high blood pressure.

How is high blood pressure treated? Although essential hypertension is incurable, Israili and others suggest that gene therapy or the use of vaccines may be feasible to prevent its development, but are not likely to be available in the near future. Currently, many individuals with essential hypertension need to take medications to control their blood pressure. A variety of drugs are available to treat hypertension, including diuretics, beta-blockers, angiotensin-converting enzyme (ACE) inhibitors, and calcium-channel blockers. The Consumers Union recommends that if your blood pressure is elevated, you and your doctor need to take aggressive action. If drug therapy is recommended, you may need to experiment with your physician as to type and dose of medicine to use. This is especially important for athletic individuals. Niedfeldt suggests using drugs that are less likely to have adverse effects on exercise performance. For example, diuretics and beta-blockers may impair aerobic endurance performance. Physicians should also be aware that use of beta-blockers is prohibited for competition in some sports. Tanji and Batt provide a detailed discussion of the pharmacological treatment of hypertension in physically active individuals. Other than impairment of aerobic endurance capacity, bloodpressure drugs may cause other adverse health effects. Thus, a nonpharmacologic approach is often a first choice of treatment in

TABLE 9.11

Category

Classification of blood pressure for adults age 18 years and older Systolic (mmHg)

Diastolic (mmHg)

100

Normal

Source: National Heart, Lung, and Blood Institute.

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1. Achieve and maintain a healthy body weight. Numerous studies have shown that reducing body weight, even as little as 10 pounds, will reduce blood pressure in overweight, hypertensive individuals. Maintaining a healthy body weight may be one of the most effective preventive measures. Thus, restriction of caloric intake to either lose or maintain body weight may be a helpful dietary strategy. Healthful methods of losing excess body fat are presented in chapter 11. 2. Reduce or moderate sodium intake. This remains one of the most controversial recommendations, but it may be a prudent behavior for most individuals. Some researchers, such as Alderman, indicate the available data provides no support for any universal recommendation for a particular level of sodium intake. In support of this viewpoint, Cohen and Alderman reported a “J shape” relationship between sodium intake and cardiovascular disease mortality, noting a direct association at high levels of average intake (over 4 g), an inverse association at lower levels (less than 2 g), and no measurable effect for the widely prevalent intakes in between. They suggest both high and very low levels of sodium intake may be related to cardiovascular-related deaths. Others suggest sodium restriction has only modest effects on blood pressure in normotensive individuals. On the other hand, others recommend a significant reduction in current sodium intake in industrialized societies. Cappuccio has noted that most prospective studies have shown that higher salt intake predicts the incidence of cardiovascular events, but the lack of large and long randomized trials on the effects of salt reduction has encouraged some people to argue against a policy of salt reduction in populations. However, Cook and others recently conducted such a study, the longterm Trials of Hypertension Prevention (TOHP) study. Adults with pre-hypertension reduced sodium intake by about 800 to 1,000 milligrams daily for 18 months and up to 4 years. In a follow-up assessment of 10–15 years, the sodium reduction resulted in a 25 percent lower risk of experiencing a cardiovascular event, such as a heart attack, stroke, or cardiovascular death. The investigators concluded that sodium reduction, previously shown to lower blood pressure, may also reduce longterm risk of cardiovascular events. Most health governmental agencies and professional groups promote dietary sodium restriction. Penner and others noted that one in four Canadians have hypertension, and with the lifetime risk of developing hypertension being more than 90 percent in an average life span, the need for a population-

based approach to reducing hypertension is clear. Thus, the Canadian Hypertension Education Program, in its recent scientific summary, recommended reducing sodium in the diet of all Canadians to less than 2,300 milligrams/day, and 1,500 milligrams/day in hypertensive individuals. The AI for Americans is 1,500 milligrams/day, while the UL is 2,300 milligrams/day. The American Medical Association (AMA) has developed a campaign to reduce sodium intake nationwide. The AMA is urging the FDA to remove salt from the GRAS (generally recognized as safe) list and also require high-salt foods to carry a distinctive label, such as pictures of salt shakers bearing the word High. Although some question the wisdom in recommending salt restriction in all individuals, many health professionals suggest this is a good policy. Why might it be prudent for most normotensive individuals to moderate salt intake? It is true that most individuals possess physiological control systems that effectively maintain a proper balance of sodium in the body. However, many individuals are sodium-sensitive, or salt-sensitive, in that their blood pressure may increase with excessive consumption of salt. Possibly because of a defect in excretion, sodium accumulates in the body and holds fluids, particularly blood, thereby raising the blood pressure. In their review, McCarron and Reusser report that salt sensitivity is present in about 30 percent of normotensive and 50 percent of hypertensive persons, and is more prevalent among African Americans and older individuals. Franco and Oparil also note that salt sensitivity in both normotensive and hypertensive persons has been associated with increased cardiovascular disease events. That being so, and since many individuals do not know their blood pressure, millions of Americans may benefit from the recommendation to moderate salt intake. Moreover, the recent American Institute for Cancer Research report on nutrition and cancer indicates that high salt intake may damage the stomach lining and may have a synergistic interaction with gastric carcinogens. The research panel concluded that salted and salty foods are a probable cause of stomach cancer. The current prudent medical recommendation for dietary prevention or treatment of hypertension is to decrease sodium consumption simply by eating a wide variety of foods in their natural state. Avoid highly salted foods, restrict intake of processed foods, and hide your salt shakers. The recommended upper limit is somewhat less than 6 grams of salt per day, just a little over 1 teaspoon, the equivalent of about 2.3 grams of sodium. The AI, based on potential healthful effects on blood pressure, is only 1.5 grams, or less than 4 grams of salt daily. Individuals who sweat during training most likely do not need to be concerned with the sodium content in sports drinks. Over the course of a month, Roberts reported no change in blood pressure in normotensive individuals who worked strenuously outside and consumed about 4.5 liters of a typical CES daily. It should be noted that decreasing salt and sodium intake poses some practical difficulties. Most salt we eat comes from the packaged foods we buy. Even minimally processed foods, such as milk and bread, may contain significant amounts of

sodium. Salt is also high in most restaurant foods; some single servings of fast food have over 1,000 milligrams of sodium, some up to nearly 5,000 milligrams. Thus, one might have to buy most foods in their natural state and prepare and cook them at home, from scratch. For those with hypertension, it may be a challenge—but worth it. 3. Consume a diet rich in fruits, vegetables, and low-fat, proteinrich foods and with reduced saturated and total fat. McCarron and Reusser note that large-scale studies have shown that whereas manipulation of single nutrients may have beneficial health effects for some individuals, it is improving the total dietary profile that will consistently provide health benefits, such as reducing high blood pressure. The DASH (Dietary Approaches to Stop Hypertension) diet emphasizes fruits and vegetables, nuts, low-fat dairy foods, fish, and chicken instead of red meat, low-sugar and low-refined carbohydrate foods, and reduced saturated and total fat. The DASH eating plan for a 2,000 Calorie diet is presented in table 9.12. The number of servings may be modified to meet other caloric requirements. The DASH diet is rich in potassium, magnesium, calcium, and fiber, which have been suggested to help prevent high blood pressure. The JNCDET, in its seventh report, particularly recommends increased consumption of potassium, which is abundant in fruits and vegetables. www.nhlbi.nih.gov For a detailed DASH eating plan, visit this Website and click on Heart/Vascular and then scroll down to High Blood Pressure and information on the DASH diet. This site also provides other detailed information on high blood pressure.

As noted in earlier chapters, Appel and others modified the DASH diet by replacing about 10 percent of the DASH’s carbohydrates (mostly desserts and fruits) with either good proteins (fish, poultry, beans, tofu) or good fats (olive oil, canola oil, nuts). They found that such replacements resulted in additional decreases in blood pressure, and called it the OmniHeart diet. However, in a meta-analysis of randomized controlled trials, Shah and others concluded that although diets rich in carbohydrate may be associated with slightly higher blood pressure than diets rich in monounsaturated fat, the magnitude of the difference may not justify making recommendations to alter the carbohydrate and monounsaturated fat content of the diet to manage blood pressure. www.omniheart.org The OmniHeart Website provides the scientific basis for the OmniHeart diet, and also provides menus and diet plans for individuals who desire to adopt this diet.

Both the DASH and OmniHeart diets are based on healthy concepts, being rich in fruits and vegetables, healthy protein, and phytonutrients, and low in bad fats, sweets, and salt. Both diet plans may help reduce blood pressure, and may also help reduce the risks of other risk factors associated with heart disease and stroke. For example, Azadbakht and others indicated that the DASH diet can likely produce multiple health benefits other than reduced blood pressure, including higher www.mhhe.com/williams9

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TABLE 9.12

The DASH Eating Plan Significance to the DASH eating plan

Food group

Servings

Serving sizes

Examples and notes

Grains and grain products

7–8 per day

1 slice bread 1 oz dry cereal 1 /2 cup cooked rice, pasta, or cereal

Whole wheat bread, English muffin, pita bread, bagel, cereals, oatmeal, unsalted pretzels, popcorn

Major sources of energy and fiber

Vegetables

4–5 per day

1 cup raw leafy vegetable /2 cup cooked vegetable 6 oz vegetable juice

Tomatoes, potatoes, carrots, green peas, broccoli, kale, spinach, lima beans, sweet potatoes

Rich sources of potassium, magnesium, and fiber

1

Fruits

4–5 per day

6 oz fruit juice 1 medium fruit 1 /4 cup dried fruit

Apricots, bananas, dates, grapes, oranges, orange juice, melons, peaches pineapples, raisins, strawberries

Important sources of potassium, magnesium, and fiber

Lowfat or fat free dairy foods

2–3 per day

8 oz milk 1 cup yogurt 11/2 oz cheese

Fat-free (skim) milk, fat-free or low-fat regular or frozen yogurt, low-fat and fat-free cheese

Major sources of calcium and protein

Meats, poultry, and fish

2 or less per day

3 oz cooked meats, poultry, or fish

Select only lean; trim away visible fats; broil, roast, or boil, instead of frying; remove skin from poultry

Rich sources of protein and magnesium

Nuts, seeds, and dry beans

4–5 per week

1

/3 cup or 11/2 oz nuts 2 Tbsp or 1/2 oz seeds 1 /2 cup cooked dry beans or peas

Almonds, mixed nuts, peanuts, walnuts, sunflower seeds, kidney beans

Rich sources of energy, magnesium, potassium, protein, and fiber

Fats and oils

2–3 per day

1 tsp soft margarine 1 Tbsp low-fat mayonnaise 2 Tbsp light salad dressing 1 tsp vegetable oil

Soft margarine, low-fat mayonnaise, light salad dressing, vegetable oil (olive, corn, canola)

DASH has 27 percent of Calories as fat, including fat in or added to foods. 1 Tbsp fat-free dressing equals 0 servings

Sweets

5 per week

1 Tbsp sugar 1 Tbsp jelly or jam 1 /2 oz jelly beans

Sugar, jelly, jam, jelly beans, hard candy, sorbet, ices

Adapted from The DASH Eating Plan. National Heart, Lung, and Blood Institute. For more details, go to www.nhlbi.nih.gov/health/public/heart/hbp/dash.

HDL-cholesterol and lower triglycerides, fasting blood glucose, and body weight. In a recent prospective cohort study, Fung and others assessed the association between adherence to a DASH-style diet and risk of coronary heart disease (CHD) and stroke in middle-aged women. They found, over the course of 24 years, that adherence to a DASH-style diet was associated with a lower risk of CHD and stroke. For those with hypertension, and even normotensive individuals, some health professionals recommend the DASH or OmniHeart diet and the extra effort to cut back to 1,500 milligrams of sodium per day. In a recent randomized, controlled trial, Sacks and others found that the DASH diet for 30 days resulted in significant reductions in both systolic and diastolic blood pressure. All individuals in this study were also randomly assigned to three different levels of salt intake for a

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30-day period, and the decrease in blood pressure was greatest when subjects consumed the diet with the lowest amount of salt, only 1,500 milligrams per day. 4. Moderate alcohol consumption. As noted in chapter 4, moderate alcohol consumption may actually confer some health benefits, particularly the prevention of cardiovascular disease. However, excess alcohol intake may increase the heart disease risk, possibly because it is linked to high blood pressure. 5. Be cautious with dietary supplements. Haddy and others report that potassium serves as a vasodilating substance, and indicate that potassium supplementation can lower blood pressure, but it is slow to appear, taking about 4 weeks. In a meta-analysis, Dickinson and others analyzed six randomly controlled trials and found that potassium supple-

mentation resulted in a large but statistically nonsignificant reduction in both systolic and diastolic blood pressure. They noted that given the data from these studies, the evidence about the effect of potassium supplementation on blood pressure is not conclusive, and additional research is needed. In another meta-analysis, Dickinson and others concluded that neither calcium nor magnesium supplementation reduced blood pressure. Given the potential health risks of potassium supplementation, as noted earlier, individuals considering such supplementation should do so only under the guidance of their physician. As you probably noticed, all of these recommendations are in accord with the Prudent Healthy Diet. The more of these recommendations you follow, the better. In one study, subjects who lost weight, increased physical activity, and reduced sodium and alcohol intake experienced significant reductions in blood pressure, but subjects who also adhered to the DASH diet experienced the greatest reduction.

Can exercise help prevent or treat hypertension? Regular mild- to moderate-intensity aerobic exercise, such as jogging, brisk walking, swimming, cycling, and aerobic dancing, has also been recommended to reduce high blood pressure. The exercise does not need to be continuous. Elley and others found that four 10-minute exercise snacks consisting of brisk walking, as compared to a single 40-minute continuous bout of brisk walking, done over the course of a day elicited similar reductions in both systolic and diastolic blood pressure. Individuals can work these exercise snacks into their daily schedule when they can’t find a large block of free time. Since exercise may be an effective means of losing excess body fat, it may exert a beneficial effect on blood pressure through this avenue. However, the exact role or mechanism of exercise as an independent factor in lowering blood pressure has not been totally resolved. Kramer and others theorize that exercise may exert favorable effects on the hypothalamus, inducing the sympathetic nervous system to decrease constriction of blood vessels and reduce vascular resistance, which is one factor contributing to elevated blood pressure. Although a number of studies have shown that exercise training helps decrease resting systolic blood pressure in those who are hypertensive and may even elicit a slight decrease in those with normal blood pressure, not all studies are in agreement. Not all individuals will experience a decrease in blood pressure from an exercise program; they may be exerciseinsensitive, or nonresponders. Nevertheless, most health professionals find the available information sufficient to justify an aerobic exercise program as a useful adjunct for the treatment of high blood pressure. Most research has focused on the chronic effect of exercise training on blood pressure. Most recent reviews and meta-analyses report significant reductions in both diastolic and systolic blood pressure,

more so in hypertensive than normotensive individuals. In a recent meta-analysis of 72 studies, Fagard concluded that aerobic endurance exercise training reduced blood pressure by about 3.0 mmHg, and the reduction was greater in subjects with hypertension (⫺6.9 mmHg) than those who were normotensive (⫺1.9 mmHg). Although the number of studies were limited, Fagard also noted that resistance training was able to reduce blood pressure. These overall reductions in blood pressure appear to be small, but Israili and others note that even small reductions in systolic blood pressure (for example, 3–5 mm Hg) produce dramatic reduction in adverse cardiac events and stroke. The American College of Sports Medicine, in its recent position stand on exercise and hypertension, stated that exercise is the cornerstone therapy for the primary prevention, treatment, and control of hypertension. These are some of the major points of the position stand. • Exercise programs that involve endurance activities, such as walking, jogging, running, or cycling, coupled with resistance training, help to prevent the development of hypertension and to lower blood pressure in adults. • Exercise should be done daily for 30 minutes or more at a moderate level. • A higher level of physical activity and fitness resulting from long-term exercise training has a protective effect against hypertension; fitter people with hypertension will have lower blood pressure than those who are less fit. • Even a single session (acute) exercise bout provides an immediate reduction in blood pressure, which can last for a major portion of the day. Promoting the benefits of lowering blood pressure through single bouts of exercise may help motivate people to exercise. Special considerations for exercise with hypertension include the following: • Individuals with controlled hypertension and no cardiovascular or kidney disease may participate in an exercise program. • Overweight adults should use exercise to lose weight. • People on medications, such as beta-blockers, should be cautious of developing heat illness when exercising. • Adults with hypertension should extend the cool-down period of the workout; some medications may cause blood pressure to lower too much after abruptly ending exercise. Individuals who have high blood pressure and who have concerns about exercising should consult with their physicians about mode and intensity of exercise. Although aerobic exercise may help reduce blood pressure at rest and may evoke a lessened blood pressure rise during exercise, a protective effect, other exercises may be harmful. For example, high-intensity anaerobic exercise and activities that require intense straining, lifting, or hanging, such as isometric exercises, weight lifting, or pull-ups might be inappropriate for some individuals. The use of hand-held weights in aerobic exercises may also be a concern. These activities may create a physiological response that rapidly raises the blood pressure to rather high levels. This increase may be hazardous to someone

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whose resting blood pressure is already at an elevated level. Thus, hypertensive individuals need to consult with their physicians regarding exercise indications and contraindications. In summary, the more healthful behaviors one adopts, the greater will be the reduction in blood pressure. In a recent review, the JNCDET noted that a healthy lifestyle may be sufficient to avoid pharmacologic therapy for some patients and is a valuable adjunct to drug therapy for most. The JNCDET quantified the potential blood pressure lowering effects of various health behaviors, as follows: • • • • •

Ke y C o n c e p t 䉴 Lifestyle practices to help prevent or treat high blood pressure

include maintaining an optimal body weight, aerobic exercise, moderation in salt and sodium intake, moderation in alcohol consumption, and increased intake of fruits, vegetables, whole grains, and low-fat, high-protein foods.

C h e c k f o r Yo u r s e l f

Weight reduction (5–20 mmHg/10 kg) DASH eating plan (8–14 mmHg) Dietary sodium reduction (2–8 mmHg) Increased physical activity (4–9 mmHg) Moderation of alcohol consumption (2–4 mmHg)

A P P L I C AT I O N Determine your body temperature response and sweating rate. First, measure your body temperature accurately before exercise. An oral thermometer is acceptable, but keep your mouth closed tightly during all measurements. Also, weigh yourself exactly in a pair of dry, light clothes. Second, exercise for about 30–60 minutes, preferably under warm environmental conditions, either indoors or outdoors. Record exactly the amount of fluid you consume during exercise. Third, immediately after exercise, record your body temperature. Then, immediately towel dry and weigh yourself in the same dry set of clothes. Calculate your body temperature increase from the difference between the preexercise and postexercise recordings. Calculate your sweat loss by subtracting your postexercise weight from your initial weight and adding to this amount the number of ounces of fluid you consumed. This will provide you with your sweat rate for the time you exercised, which you can then calculate to sweat rate per hour. If feasible, conduct this little selfexperiment before and after acclimatization to exercise in the heat and compare the responses. What might you expect to find?

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Have your blood pressure checked at rest. If possible, have it checked immediately after both an aerobic-type and resistancetype exercise.

E X E R C I S E Body Temperature Response and Sweating Rate Step 1

Step 2

Step 3

Preexercise temperature

Fluid consumed during exercise

Postexercise temperature

Preexercise weight

Determination of body temperature response and sweating rate to exercise Sweating rate A. Enter your preexercise body weight (nearest 0.25 pound). ________ B. Enter your postexercise body weight in pounds (nearest 0.25 pound). ________ C. Subtract B from A. ________ D. Convert C to ounces (1 pound = 16 fluid ounces). ________ E. Enter the amount of fluid (in ounces) you consumed during the run. ________ F. Add E to D. ________ G. Divide F by the number of minutes of exercise to calculate sweat rate per minute. ________ H. Multiply G by 60 to obtain sweat rate per hour. ________

C H A P T E R 9 Water, Electrolytes, and Temperature Regulation

Postexercise weight

The final figure provides you with a guide to replenish fluids per hour. You need not fully replenish what you lose per hour, but replacing about 60 percent or more will help you prevent excessive dehydration. Body temperature response A. Enter your preexercise body temperature in degrees Fahrenheit or Celsius. ________ B. Enter your postexercise body temperature in degrees Fahrenheit or Celsius. ________ C. Subtract B from A. ________ The final figure represents your core body temperature increase for the intensity and duration of exercise and for the given environmental conditions (air temperature, humidity, solar radiation).

Review Questions—Multiple Choice

5.

6.

7.

8.

(c) magnesium (d) sodium (e) potassium (f) phytonutrients Excessive loss of sweat during exercise in the heat will lead to a condition in the body known as (a) hyperhydration (b) hypohydration (c) homeostasis (d) normohydration (e) euhydration Which of the following is not one of the physical means whereby heat is lost from the human body? (a) condensation (b) conduction (c) evaporation (d) convection (e) radiation A high relative humidity and sunshine impose a heat stress during exercise by their adverse effects on the body, respectively, as: (a) increased condensation of sweat and decreased radiant heat to the body (b) increased convection heat loss and decreased radiant heat to the body (c) decreased evaporation of sweat and increased radiant heat to the body (d) decreased condensation of sweat and decreased convection of heat to the body (e) increased evaporation of sweat and increased convection of heat to the body Calculate the increase in the body temperature, in degrees Celsius, that would

occur if an individual was unable to dissipate heat and was exercising at an intensity of 3 liters of oxygen per minute for 20 minutes. The athlete weighs 60 kg, her mechanical efficiency is 20 percent, and the specific heat of her body is 0.83. (a) 2.2 (b) 4.8 (c) 10.2 (d) 6.0 (e) 9.4 9. Which of the following statements regarding bottled water is false? (a) Bottled water is normally much more expensive than municipal water supplies. (b) Bottled water must conform to the same safety standards as municipal water supplies. (c) Some bottled waters are simply municipal water that has undergone purification. (d) Bottled water normally contains more fluoride than fluoridated municipal water supplies. 10. During prolonged endurance exercise in the heat, excessive intake of water and inadequate intake of salt may lead to a dangerous health condition known as (a) hypercalcemia (b) hypotension (c) hypohydration (d) hyponatremia (e) hyperkalemia Answers to multiple-choice questions: 1. c; 2. e; 3. d; 4. d; 5. b; 6. a; 7. c; 8. b; 9. d; 10. d.

1. Which of the following blood pressure values for adults 18 years of age and older represents the minimal blood pressure for the first stage of hypertension (mild)? The values listed are systolic and diastolic, in that order. (a) 130 and 80 (b) 130 and 90 (c) 140 and 90 (d) 160 and 100 (e) 210 and 120 2. Which of the following does not occur in acclimatization to exercise in the heat? (a) increased sweat production during exercise (b) increased blood volume (c) a lower rise in the core temperature during exercise (d) a lesser rise in the heart rate response to exercise (e) an increased sodium loss in each liter of sweat 3. Which of the following statements is false? (a) The maximal sweat rate appears to be about 2–3 liters per hour. (b) Dehydration as low as 2 percent of the body weight may lead to a decrease in aerobic endurance performance. (c) Sweat is mainly water. (d) The major electrolytes found in sweat are calcium and potassium. 4. Which of the following is most limited in the DASH diet? (a) calcium (b) fiber

Review Questions—Essay 1. Discuss the means whereby your body maintains normal water balance. Include in your discussion the role of the blood, hypothalamus, pituitary gland, antidiuretic hormone, and kidney. 2. Name the four components of heat stress that are recorded by the Wet-Bulb Globe Temperature (WBGT) thermometer, and discuss how each factor may contribute to

heat stress during exercise under warm environmental conditions. 3. Your friend is going to run a marathon. The projected weather forecast is sunny, warm, and humid. What advice would you offer regarding consumption of fluids, including carbohydrate and electrolytes, before and during the race?

4. List and discuss five strategies to help reduce the hazards associated with exercise in a hot environment. 5. What is high blood pressure? Why is it dangerous to your health? What lifestyle behaviors may help in its prevention or treatment?

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Hargreaves, M., et al. 1996. Effect of fluid ingestion on muscle metabolism during prolonged exercise. Journal of Applied Physiology 80:363–66. Hargreaves, M., et al. 1994. Influence of sodium on glucose bioavailability during exercise. Medicine & Science in Sports & Exercise 26:365–68. Hew-Butler, T., et al. 2006. Sodium supplementation is not required to maintain serum sodium concentrations during an Ironman triathlon. British Journal of Sports Medicine 40:255–59. Hitchins, S., et al. 1999. Glycerol hyperhydration improves cycle time trial performance in hot humid conditions. European Journal of Applied Physiology 80:494–501. Hunter, I., et al. 2006. Warming up with an ice vest: Core body temperature before and after crosscountry racing. Journal of Athletic Training 41:371–74. Jentjens, R., et al. 2006. Exogenous carbohydrate oxidation rates are elevated after combined ingestion of glucose and fructose during exercise in the heat. Journal of Applied Physiology 100:807–16. Judelson, D., et al. 2007. Effect of hydration state on strength, power, and resistance exercise performance. Medicine & Science in Exercise & Sports 39:1817–24. Kavouras, S., et al. 2006. Rehydration with glycerol: Endocrine, cardiovascular, and thermoregulatory responses during exercise in the heat. Journal of Applied Physiology 100:442–50. Kenefick, R., et al. 2007. Rehydration with fluid of varying tonicities: Effects on fluid regulatory hormones and exercise performance in the heat. Journal of Applied Physiology 102:1899–1905. Kenefick, R., et al. 2002. Hypohydration adversely affects lactate threshold in endurance athletes. Journal of Strength and Conditioning Research 16:38–43. Lalumandier, J., and Ayers, L. 2000. Flouride and bacterial content of bottled water vs tap water. Archives of Family Medicine 9:246–50. Lambert, G., et al. 1993. Effects of carbonated and noncarbonated beverages at specific intervals during treadmill running in the heat. International Journal of Sport Nutrition 3:177–93. Latzka, W. A., et al. 1998. Hyperhydration: Tolerance and cardiovascular effect during uncompensable exercise-heat stress. Journal of Applied Physiology 84:1858–64. Latzka, W. A., et al. 1997. Hyperhydration: Thermoregulatory effects during compensable exercise-heat stress. Journal of Applied Physiology 83:860–66. Lindeman, A. 1991. Nutrient intake of an ultraendurance cyclist. International Journal of Sport Nutrition 1:79–85. Lyons, T., et al. 1990. Effects of glycerol-induced hyperhydration prior to exercise in the heat on sweating and core temperature. Medicine & Science in Sports & Exercise 22:477–83. Magal, M., et al. 2003. Comparison of glycerol and water hydration regimens on tennis-related performance. Medicine & Science in Sports & Exercise 35:150–56. Marino, F., et al. 2003. Glycerol hyperhydration fails to improve endurance performance and thermoreg-

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Rogers, G., et al. 1997. Water budget during ultraendurance exercise. Medicine & Science in Sports & Exercise 29:1477–81. Rogers, J., et al. 2005. Gastric emptying and intestinal absorption of a low-carbohydrate sport drink during exercise. International Journal of Sport Nutrition and Exercise Metabolism 15:220–35. Ronneberg, K., et al. 2008. Temporal artery temperature measurements do not detect hyperthermic marathon runners. Medicine & Science in Sports & Exercise 40:1373–75. Roti, M., et al. 2006. Thermoregulatory responses to exercise in the heat: Chronic caffeine intake has no effect. Aviation, Space, and Environmental Medicine 77:124–29. Rowland, T., et al. 2008. Exercise tolerance and thermoregulatory responses during cycling in boys and men. Medicine & Science in Sports & Exercise 40:282–87. Ryan, A. J., et al. 1998. Effect of hypohydration on gastric emptying and intestinal absorption during exercise. Journal of Applied Physiology 84:1581–88. Sacks, F., et al. 2001. Effects on blood pressure of reduced dietary sodium and the Dietary Approaches to Stop Hypertension (DASH) diet. New England Journal of Medicine 344:3–10. Sanders, B., et al. 1999. Water and electrolyte shifts with partial fluid replacement during exercise. European Journal of Applied Physiology 80:318–23. Scheett, T. P., et al. 2001. Effectiveness of glycerol as a rehydrating agent. International Journal of Sport Nutrition and Exercise Metabolism 11:63–71. Schoffstall, J., et al. 2001. Effects of dehydration and rehydration on the one-repetition maximum bench press of weight-trained males. Journal of Strength and Conditioning Research 15:102–8. Seifert, J., et al. 2006. Protein added to a sports drink improves fluid retention. International Journal of Sport Nutrition and Exercise Metabolism 16:420–29. Shah, M., et al. 2007. Effect of high-carbohydrate or high-cis-monounsaturated fat diets on blood pressure: A meta-analysis of intervention trials. American Journal of Clinical Nutrition 85:1251–56. Shirreffs, S., et al. 2007. Rehydration after exercise in the heat: A comparison of 4 commonly used drinks. International Journal of Sport Nutrition and Exercise Metabolism 17:244–58. Sims, S., et al. 2007. Preexercise sodium loading aids fluid balance and endurance for women exercising in the heat. Journal of Applied Physiology 103:534–41. Sims, S., et al. 2007. Sodium loading aids fluid balance and reduces physiological strain of trained men exercising in the heat. Medicine & Science in Sports & Exercise 39:123–30. Speedy, D., et al. 2002. Oral salt supplementation during ultradistance exercise. Clinical Journal of Sport Medicine 12:279–84. Speedy, D., et al. 2000. Exercise-induced hyponatremia in ultradistance triathletes is caused by inappropriate fluid retention. Clinical Journal of Sport Medicine 10:272–78. Stofan, J., et al. 2005. Sweat and sodium losses in NCAA football players: A precursor to heat

cramps. International Journal of Sport Nutrition and Exercise Metabolism 15:641–52. Stookey, J. 1999. The diuretic effects of alcohol and caffeine and total water intake misclassification. European Journal of Epidemiology 15:181–88. Sulzer, N., et al. 2005. Serum electrolytes in Ironman triathletes with exercise-associated muscle cramping. Medicine & Science in Sports & Exercise 37:1081–85. Tucker, R., et al. 2004. Impaired exercise performance in the heat is associated with an anticipatory reduction in skeletal muscle recruitment. Pflugers Archive 448:422–30. Twerenbold, R., et al. 2003. Effects of different sodium concentrations in replacement fluids during prolonged exercise in women. British Journal of Sports Medicine 37:300–3. Uckert, S., and Joch, W. 2007. Effects of warm-up and precooling on endurance performance in the heat. British Journal of Sports Medicine 41:380–84. Van Essen, M., and Gibala, M. 2006. Failure of protein to improve time trial performance when added to a sports drink. Medicine & Science in Sports & Exercise 38:1476–83. von Fraunhofer, J., and Rogers, M. 2005. Effects of sports drinks and other beverages on dental enamel. General Dentistry 53:28–31. Watson, P., et al. 2005. Blood-brain barrier integrity may be threatened by exercise in a warm environment. American Journal of Physiology. Regulatory, Integrative, and Comparative Physiology 288:R1689–94. Webster, J., et al. 2005. A light-weight vest enhances performance of athletes in the heat. Ergonomics 48:821–37. Wharam, P., et al. 2006. NSAID use increases the risk of developing hyponatremia during an Ironman triathlon. Medicine & Science in Sports & Exercise 38:618–22. White, J. A., et al. 1998. Fluid replacement needs of well-trained male and female athletes during indoor and outdoor steady state running. Journal of Science and Medicine in Sport 1:131–42. Wing-Gaia, S., et al. 2005. Effects of purified oxygenated water on exercise performance during acute hypoxic exposure. International Journal of Sport Nutrition and Exercise Metabolism 15:680–88. Wingo, J., et al. 2004. Influence of a pre-exercise glycerol hydration beverage on performance and physiologic function during mountain-bike races in the heat. Journal of Athletic Training 39:169–75. Yaspelkis, B., et al. 1993. Carbohydrate metabolism during exercise in hot and thermoneutral environments. International Journal of Sports Medicine 14:13–19. Yeargin, S., et al. 2006. Body cooling between two bouts of exercise in the heat enhances subsequent performance. Journal of Strength and Conditioning Research 20:383–89. Zachwieja, J., et al. 1992. The effects of a carbonated carbohydrate drink on gastric emptying, gastrointestinal distress, and exercise performance. International Journal of Sport Nutrition 2:239–50.

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K E Y

Body Weight and Composition for Health and Sport

T E R M S

activity-stat 414 air displacement plethysmography (APD) 408 aminostatic theory 412 android-type obesity 421 anorexia athletica 430 anorexia nervosa (AN) 428 appestat 412 binge eating disorder 429 bioelectrical impedance analysis (BIA) 409 body image 403 Body Mass Index (BMI) 404 brown fat 413 bulimia nervosa 429

CHAPTER TEN cellulite 405 disordered eating 428 Dual energy X-ray absorptiometry (DXA; DEXA) 409 eating disorders 428 essential fat 405 fat-free mass 405 ghrelin 413 glucostatic theory 412 gynoid-type obesity 421 hunger center 412 hyperplasia 414 hypertrophy 414 lean body mass 406 leptin 414 lipostatic theory 412 metabolic syndrome 422 morbid obesity 410 obesity 410 regional fat distribution 409 satiety center 412 set-point theory 414 settling-point theory 418 skinfold technique 408 storage fat 405 subcutaneous fat 405 underwater weighing 407 very-low-Calorie diets (VLCD) 427 visceral fat 405 waist circumference 409 weight cycling 427

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O B J E C T I V E S

After studying this chapter, you should be able to: 1. List the various components that comprise human body composition. 2. Describe the various techniques used to assess body composition and discuss the general uses and limitations of such techniques. 3. Identify Body Mass Index and body fat values associated with underweight, overweight, and degrees of obesity. 4. Explain the mechanisms whereby the human body regulates body weight, including the role of the central nervous system and feedback from peripheral organs and tissues. 5. List and explain the various genetic and environmental factors that may affect the normal regulation of body weight, particularly factors that may predispose to the development of overweight and obesity. 6. Outline the health problems that are associated with obesity in both adults and youth. 7. Describe the health problems associated with excessive weight loss involving the use of drugs, very-low-Calorie diets, and various eating disorders. 8. Understand the potential health problems associated with the female athlete triad. 9. Understand how either excess or insufficient body weight may impair sport or physical performance.

Introduction The human body is a remarkable machine. In many cases it may consume nearly a ton of food, nearly one million Calories, over a year and not change its weight by a single pound. Individuals are constantly harnessing and expending energy through the intricacies of their bodily metabolism in order to remain in energy balance. To maintain a given body weight, energy input must balance energy output. However, sometimes the energy-balance equation becomes unbalanced, and the normal body weight will either increase or decrease. If you consume only 50 more Calories per day more than you expend, you will gain 5 pounds over the course of a year. The converse is also true as you will lose 5 pounds if you expend 50 more Calories than you consume. The term body image refers to the mental image we have of our own physical appearance, and it can be influenced by a variety of factors, including how much we weigh or how that weight is distributed. Body weight appears to be a major concern of many Americans. Research has revealed that about 40 percent of adult men and 55 percent of adult women are dissatisfied with their current body weight. Similar findings have been reported at the high school and even the elementary school level, primarily with female students, and some research has found that 85 percent of both male and female first-year college students desire to change their body weight. The primary cause of this concern is the value that society, in general, assigns to physical appearance. Being overweight is viewed by many as a handicap to both personal and professional fulfillment, and the term “fattism” has been coined to reflect society’s prejudice toward the obese. Negative judgments of overweight or obese individuals are based on false assumptions of character, such as laziness or low self-discipline. Thinness is currently an attribute that females desire highly. Males generally desire muscularity, which is also becoming increasingly popular among women. Most individuals who are dissatisfied with their physical appearance feel that they are overweight, and federal surveys have shown that about two-thirds of American adults are trying to lose weight

or keep from gaining weight and spending a lot of money to do so. The Federal Trade Commission noted that consumers spend about $35 billion annually on weight-loss products. Meadows reports that one of the biggest concerns of the Food and Drug Administration (FDA) is health fraud, particularly weight-loss products which are rife with fraudulent advertising and marketing of products with no research to support their claims. Obesity is a worldwide epidemic in Western and Westernizing countries, and is also associated with poverty in developing countries. The World Health Organization estimates that approximately 1 billion individuals are overweight, with 300 million being obese. There are now as many overnourished people as undernourished around the world. Some contend obesity is as big a threat as global warming. Overweight and obesity have increased at an alarming rate in the United States over the past three decades, with the weight of the average adult male and female age 40–49 increasing by about 25–27 pounds. Currently, Wang and Beydoun report that 66 percent, or about two out of every three U.S. adults aged 20 years and older are overweight or obese. They contend that by 2015 about 75 percent of American adults will be overweight, and 41 percent will not only be overweight, but obese. Extreme obesity in the United States is growing at an alarming rate,

from 1 in 200 adults in 1986 to 1 in 50 today. Overweight and obesity are also increasing rapidly in children. Ogden and others indicated that over a recent 5-year span, the incidence of overweight among children has increased significantly from 13.9 percent to 17.1 percent. Wang and Beydoun predict that 24 percent of children and adolescents will be overweight or obese in 2015. Sullivan contends that children in this generation might be the first in history to experience a decreased life span due to the health problems associated with excess body weight. Being overweight or obese may have a significant effect upon health and physical performance. Excessive body weight, particularly in the form of body fat, has been associated with a wide variety of health problems. Obesity is one of the most prominent medical concerns in industrialized societies today, with estimated annual health costs approaching $100 billion. The Public Health Service has stated in Healthy People 2010 that one of the major health objectives for the year 2010 is to decrease the proportion of adults and children who are significantly overweight or obese. Some contend that obesity should be targeted for reduction as aggressively as cigarette smoking has been. For some athletes, simply being a little overweight may prove to be detrimental to physical performance because it costs energy to move the extra body mass. On the other hand, increased

body weight, provided it is of the right composition, may be advantageous to other athletes. At the other end of the body-weight continuum, weight losses leading to excessive thinness also may have an impact upon health and physical performance.

Anorexia nervosa and bulimia are two serious health disorders associated with obsessive concern about body weight. Although losing excess body fat may improve performance in some sports, excessive weight losses may have a negative impact upon athletic performance.

Body Weight and Composition What is the ideal body weight? We all have heard at one time or another that there is an ideal body weight for our particular height. But ideal in terms of what? Health? Appearance? Physical performance? There appears to be no sound evidence to suggest a specific ideal weight for a given individual, but some general guidelines have been proposed relative to health and physical performance, the major focus of this chapter. Most of us have our own images of how we would like to look, and indeed most individuals who attempt to attain an ideal body weight do so to enhance their appearance. An enhanced physical appearance may improve one’s body image and self-esteem, factors important to psychological health. An enhanced physical appearance may also influence performance in certain sports that involve judging of aesthetic movements, such as gymnastics and diving. Although society may create a perception of an ideal body weight for appearance, this perceived ideal body weight may or may not be in accord with optimal health and physical performance. Most research efforts have attempted to find an ideal body weight for good health. For example, data collected during the past century, mainly by life insurance companies, have been compiled into normal or desirable ranges of body weight for a given height and age. These height-weight charts represent the ideal weights at which Americans can expect to live the longest. The terminology of ideal weight has changed over the years, today being referred to as a healthy body weight. Although heightweight charts have been used to screen for normal body weight in the past, the Body Mass Index (BMI) is the current standard, which is also based on a height-weight relationship. The Body Mass Index (BMI), also known as Quetelet’s Index, is a weight:height ratio. Using the metric system, the formula is Body weight in kilograms (Height in meters)2 An individual who weighs 70 kg (154 pounds) and is 1.78 meters (70 inches) in height would have a BMI of 22.1 (70 ÷ [1.782]). If you want to use pounds and inches, the formula is (Body weight in pounds) × 705 (Height in inches)2 For the same example using pounds and inches, the BMI is also 22.1 (154 × 705 ÷ [702]). In general, a BMI range of 18.5–25 is considered to be normal. You may calculate your BMI using method A in appendix D or at various Websites. 404

The major focus of this chapter is on the basic nature of body composition and its effect on health and physical performance. The following two chapters deal with weight-control methods used to maintain or modify body composition.

http://www.cdc.gov/nccdphp/dnpa/bmi http://www.consumer.gov/weightloss/bmi.htm Access these Websites to calculate your Body Mass Index (BMI) and learn more about body composition.

What are the values and limitations of the BMI? In relation to determining whether an individual possesses normal body weight for a given height, the BMI may be a useful screening device for health problems. The Consumers Union indicates that a low BMI may be a symptom of a serious disease, while a high BMI may be indicative of obesity. Specific BMI values related to potential health status are presented later. However, for any given individual, the BMI reveals nothing to us about our body composition. The BMI value does not represent percent body fat, as some mistakenly think. As illustrated in figure 10.1, two individuals may be exactly the same height and weight and have the same BMI, but the distribution of their body weight might be so different that one individual could possibly be considered obese while the other might be considered very muscular. For example, Ode and others compared the BMI of college athletes and nonathletes with body fat levels determined by body composition analysis (discussed later). They reported that because of a large muscle mass among male and female athletes, the BMI incorrectly classifies normal-fat athletes as overweight. Conversely, many female nonathletes were classified as normal weight by the BMI but actually were overfat; the authors noted that those who do not exercise, and yet are thin, may have excessive amounts of internal fat and thus may be thin on the outside, but fat on the inside. They concluded that the BMI should be used cautiously when classifying fatness in college athletes and nonathletes. Although the BMI is not perfect and may be inappropriate for use with very muscular individuals, it is a good guide that the average person may use to think about a healthier body weight. However, other methods are needed to evaluate actual body composition.

What is the composition of the body? The human body contains many of the elements of the earth, twenty-five of which appear to be essential for normal physiological functioning. Most of the human body, about 96 percent, consists of four elements (carbon, hydrogen, oxygen, and nitrogen) in various combinations. These four elements are the structural basis for body protein, carbohydrate, fat, and water. The remaining 4 percent of our

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per milliliter (g/ml) or grams per cubic centimeter (g/cc3). The standard for comparison is water, which has a density of 1.0, or 1 g/ml. Corresponding densities for the other components are approximately 1.3–1.4 for bone, 1.1 for fat-free protein tissue, and 0.9 for fat. The density of the human body as a whole may have a wide range, approximately 1.020 to 1.100. The body-density value may be used to determine the body-fat percentage; a higher density represents a greater amount of fat-free mass and a lower amount of body fat. Depending on the purpose, body composition is usually analyzed as two, three, or all four components. The two components most commonly measured are total body fat and fat-free mass; bone mineral content and body water may be measured with more elaborate techniques. Wang and others also introduced a six-component model, which in addition to these four components adds measurement of soft-tissue minerals and glycogen.

Total Body Fat The total body fat in the body consists of both essential fat and storage fat. Essential fat is necessary for proper functioning of certain body structures such as the brain, nerve tissue, bone marrow, heart tissue, and cell membranes. Essential fat in adult males represents about 3 percent of the body weight. Adult females also have additional essential fat associated with their reproductive processes. This additional 9–12 percent of sex-specific fat gives them a total of 12–15 percent essential fat, although this amount may vary considerably among individuals. Storage fat is simply a depot for F I G U R E 1 0 . 1 The Body Mass Index (BMI), although a good general indicator of overexcess energy, and the quantity of body fat in weight and obesity, does not assess body composition in any given individual.Two individuals this form also may vary considerably. may have the same height and weight, but one may have excess body fat while the other may Some storage fat is found around body be very muscular with a low body-fat percentage. organs for protection, but about 70–80 percent of total body fat is found just under the body is composed of minerals, primarily calcium and phosphorus in skin and is known as subcutaneous fat. When this latter type of the bones, but also including others such as iron, potassium, sodium, fat is separated by connective tissue into small compartments that chloride, and magnesium. extrude into the dermis, it gives a dimpled, quilt-like look to the Because body composition may have a significant impact on skin and is popularly known as cellulite. Cellulite is primarily fat, health and physical performance, scientists have developed a varibut may contain high concentrations of glycoproteins, particles ety of techniques to measure various body components. Wang and that can attract water and possibly give cellulite skin that waffleothers noted that, depending on the purpose, body composition like appearance. The appearance of cellulite is much more commay be evaluated at five levels: atomic, molecular, cellular, tissuemon in women than in men. Other storage fat is located deep in the system, and whole-body levels. Of major interest to body composibody, particularly in the abdominal area. This deep fat is referred tion scientists are four major body components: total body fat, to as visceral fat, which as noted below is associated with fat-free mass, bone mineral, and body water; the location of the increased health risks. body fat, either under the skin or deep in the body, is of particular interest in relationship to health status. Each of these components Fat-Free Mass Fat-free mass primarily consists of protein has a different density. Density represents mass divided by volume, and water, with smaller amounts of minerals and glycogen. The and in body composition, analysis is usually expressed as grams tissue of skeletal muscles is the main component of fat-free mass, lbs

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lbs

but the heart, liver, kidneys, and other organs are included also. A more common term often used interchangeably with fat-free mass is lean body mass; technically, however, lean body mass includes essential fat. In a two-component body composition analysis, fat-free or lean body mass complements total body fat. An individual who has 20 percent body fat has 80 percent fat-free mass. Bone Mineral Bone gives structure to our body, but it is also involved in a variety of metabolic processes. Bone consists of about 50 percent water and 50 percent solid matter, including protein and minerals. Although total bone weight, including water and protein, may be 12–15 percent of the total body weight, the mineral content is only 3–4 percent of total body weight. Body Water The average adult body weight is approximately 60 percent water, the remaining 40 percent consisting of dry weight materials that exist in this internal water environment. Some tissues, like the blood, have a high water content, whereas others, like adipose tissue, are relatively dry. The fat-free mass is about 70 percent water, while adipose fat tissue is less than 10 percent. Under normal conditions the water concentration of a given tissue is regulated quite nicely relative to its needs. When we look at the percentage of the body weight that may be attributed to a given body tissue, the weight of that tissue includes its normal water content. Although the amount of fat, lean tissue, bone, and water may vary widely in individuals, the following might represent a normal distribution in a young, lean adult male: 60 percent body water and 40 percent solid matter subdivided into 14 percent fat, 22 percent protein, and 4 percent bone minerals. Body composition may be influenced by a number of factors such as age, sex, diet, and level of physical activity. Age effects are significant during the developmental years as muscle and other body tissues are being formed. Also, during adulthood, muscle mass may decrease, probably because the level of physical activity declines. There are some minor differences in body composition between boys and girls up to the age of puberty, but at this age the differences become fairly great. In general, girls deposit more fat beginning with puberty, while boys develop more muscle tissue. Diet can affect body composition over the short haul, such as during acute water restriction and starvation, but the main effects are seen over the long haul. For example, chronic overeating may lead to increased body-fat stores. Physical activity may also be very influential, with a sound exercise program helping to build muscle and lose fat.

What techniques are available to measure body composition and how accurate are they? The measurement of body fat has become very popular in recent years. Many high school and university athletic departments routinely analyze the body composition of their athletes in attempts to predict an optimal weight for competition. In some sports, such as wrestling, measurement of body composition is mandated by various state or national sport associations. Fitness and wellness centers also usually include a body-fat analysis as one of their 406

services. Unfortunately, some of the individuals who analyze body composition in these situations are unaware of the limitations of the tests they employ. The only direct, accurate method of analyzing body composition is by chemical extraction of all fat from body tissues, which is obviously not appropriate with living humans. Thus, a variety of indirect methods have been developed to assess body composition. Some are relatively simple, such as visual observation by an experienced judge, and others are rather complex, such as nuclear magnetic resonance imaging, using multimillion dollar machines. Indirect methods are used to measure body fat, lean body mass, bone mineral content, and body water. Some techniques are also used to measure fat in specific locations of the body. Before continuing this discussion, it must be emphasized that measurement of body composition is not an exact science. All techniques, even technologically sophisticated ones, currently used to predict body density or percentage of body fat are only estimates and are prone to error, particularly when used to determine the body fat of a given individual. Such errors usually are expressed statistically as standard errors of measurement or estimate, which can be used to show the accuracy of the body-fat measurement. Without going into the statistics of standard errors, look at the following example. Let us suppose that a formula using skinfold techniques predicts your body fat at 17 percent, yet the formula has a standard error of 3 percent. What this means is that your true body fat percentage is probably (about 70 percent probability) somewhere between one standard error of the predicted value, or somewhere between 14–20 percent. It may even be lower than 14 and higher than 20 percent, but less likely so. Thus, you should not think of body-fat determinations as precise measures, but consider them as a possible range associated with the error of measurement. Most field methods used, such as skinfolds and bioelectrical impedance analysis (BIA), are two-component models, as are some laboratory methods, such as underwater weighing. Going indicates that methods based on two-component models are associated with greater errors than are methods based on multicomponent models, such as dual energy X-ray absorptiometery (DEXA). Three- and four-competent models that combine measures of body density with body water and mineral content dramatically reduce the errors associated with the traditional two-compartment model (fat and fat-free mass). A number of body composition measurement techniques are highlighted in table 10.1, but only the more commonly used or promising techniques will be discussed. For more details on body composition analysis, the interested reader is referred to the recent review by Going. Consult the review by Malina for an assessment of body composition in athletes. The book by Heyward and Wagner provides an excellent review, and also provides available prediction formulae for athletic groups. When determining changes in body composition of an individual over time, such as in a weight-loss program, it is important to use the same method throughout the testing to help minimize errors that may occur when using different methods. For example, if you select the skinfold procedure, it should be used consistently throughout, not interspersed with other techniques

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TABLE 10.1

Methods used to determine body composition using the two (2)- or three (3)-component models

Anthropometry (2)

Measures body segment girths to predict body fat

Bioelectrical impedance analysis (BIA) (2)

Measures resistance to electric current to predict body-water content, lean body mass, and body fat

Body plethysmography (2)

Whole-body plethysmograph measures air displacement and calculates body density; comparable to water displacement protocol used in underwater weighing

Computed tomography (CT) (3)

X-ray scanning technique to image body tissues; useful in determining subcutaneous and deep fat to predict body-fat percentage; used to calculate bone mass

Dual energy X-ray absorptiometry (DEXA; DXA) (3) X-ray technique at two energy levels to image body fat; used to calculate bone mass Dual photon absorptiometry (DPA) (3)

Beam of photons passes through tissues, differentiating soft tissues and bone tissues; used to predict body fat and calculate bone mass

Infrared interactance (2)

Infrared light passes through tissues, and interaction with tissue components used to predict body fat

Magnetic resonance imaging (MRI) (3)

Magnetic-field and radio-frequency waves are used to image body tissues similar to CT scan; very useful for imaging deep abdominal fat

Neutron activation analysis (3)

Beam of neutrons passes through the tissues, permitting analysis of nitrogen and other mineral content in the body; used to predict lean body mass

Skinfold thicknesses (2)

Measures subcutaneous fat folds to predict body-fat content and lean body mass

Total body potassium (2)

Measures total body potassium, the main intracellular ion, to predict lean body mass and body fat

Total body water (Hydrometry) (2)

Measures total body water by isotope dilution techniques to predict lean body mass and body fat

Ultrasound (2)

High frequency ultrasound waves pass through tissues to image subcutaneous fat and predict body-fat content

Underwater weighing (Hydrodensitometry) (2)

Underwater-weighing technique based on Archimedes’ principle to predict body density, body fat, and lean body mass

such as BIA. Moreover, Going suggests that when used, twocompartment estimates should employ population-specific equations if available. Population-specific equations include gender and age, and some may be specific to different ethnic and athletic groups. Going has provided a supplement to choosing the best equation for estimating body composition from skinfolds or BIA which can be accessed at the Gatorade Sports Science Institute (GSSI) Website. www.gssiweb.com Type Body Composition in the Search box, and click on Optimizing Techniques for Determining Body Composition.

Underwater Weighing One of the most common research techniques for determining body density is underwater weighing, also known as hydrodensitometry. The technique is based on Archimedes’ principle that a body immersed in a fluid is acted upon by a buoyancy force in relation to the amount of fluid the body displaces (see figure 10.2). Since fat is less dense and bone and muscle tissue are more dense than water, a given weight of fat will displace a larger volume of water and exhibit a greater buoyant effect than the corresponding weight of bone and muscle tissue. Different formulas are recommended for determination of body density, depending upon the age and sex of the individual. Although this technique

F I G U R E 1 0 . 2 Underwater weighing is one of the more common laboratory means for determining body composition. However, all current techniques for estimating percent body fat are subject to error. See text for discussion.

was once referred to as the “gold standard” in body-composition analysis, it is a two-component model with associated weaknesses. For example, the assumption that the density of the fat-free protein www.mhhe.com/williams9

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tissue is 1.10 g/cc3 may not be valid for all individuals, such as athletes and older persons. The standard error is still about 2–2.5 percent. Thus, Wagner and Heyward noted that underwater weighing should not be regarded as the “gold standard” because of these errors. Because the underwater-weighing technique is rather time consuming and difficult for some individuals, other techniques have been developed either for research purposes or practical applications. The interested reader is referred to the review by Going and the book by Heyward and Wagner. Air Displacement Plethysmography (APD) Another technique is air displacement plethysmography (APD), sometimes referred to as body plethysmography. Subjects enter a dualchamber plethysmograph designed to measure the amount of air they displace, somewhat comparable to the water displacement technique of underwater weighing. One commercial product available is called the Bod Pod (see figure 10.3). It is portable, easy to operate, requires little time, and eliminates the necessity of going underwater, several clear advantages compared to underwater weighing. Several reviews, including one by Wagner and Heyward, have noted that it may be more valid and reliable than hydrodensitometry for certain individuals, such as those who fear underwater submersion, but has similar limitations. In this regard, Fields noted that the ADP and underwater weighing agree within 1 percent of body fat for adults and children, but when compared to multicomponent models ADP generally underestimated body fat by 2–3 percent. Several studies compared the Bod Pod to DEXA and reached different conclusions. A study with men reported a 2.2 percent difference in body fat between the two methods, whereas a study with women reported no significant differences. Overall, Noreen and Lemon indicate that the ADP appears to be a reliable method to use in tracking changes in body composition in individuals over time.

F I G U R E 1 0 . 3 The Bod Pod. An application of total body plethysmography, an air displacement technique, to evaluate body composition. Photo courtesy of Life Measurement Instruments.

Skinfolds The skinfold technique is designed to measure the subcutaneous fat (see figure 10.4). It appears to be the most common procedure for nonresearch purposes. The values obtained are inserted into an appropriate formula to calculate the body-fat percentage. The formula chosen should be specific to the sex, age, and ethnicity of the individual. Some formulas also have been developed for specific athletic groups. To improve the accuracy of this technique, skinfold measures should be obtained from a variety of body sites, because using a single skinfold site may be unrepresentative of total storage fat. The test also should be administered with an acceptable pair of skinfold calipers by an experienced tester. Ultrasound techniques are also available to assess skinfold thicknesses, but these are more expensive than calipers. Orphanidou and others found that measurements of subcutaneous body fat with skinfold techniques were comparable to those obtained by ultrasound and computed tomography, suggesting the use of skinfold calipers in the clinical setting is appropriate. In a recent study, Utter and Hager found that ultrasound provided similar estimates of fatfree mass as hydrostatic weighing in high school wrestlers, and suggested it could be an alternative field-based method. Because this method involves some measurement error, and because the formulas are usually based upon the underwaterweighing technique, the standard error for the skinfold technique is about 3–4 percent, which should be kept in mind when using this method to estimate body fat. Nevertheless, Lohman and others indicated the skinfold technique is one of the best practical methods to measure body composition, and Wagner and Heyward noted that it can provide accurate results for lean subjects, such as athletes. Using a population-specific formula for gender, age, ethnicity, and sport, if available, will help reduce prediction errors. For example, Clark and others validated the NCAA skinfold technique as a means to predict minimal weight classes for wrestlers. For those who have access to a good skinfold caliper, some gener-

F I G U R E 1 0 . 4 A schematic drawing showing the skinfold of fat that is pinched up away from the underlying muscle tissue.

Muscle

Bone

Skin Fat

408

C H A P T E R 1 0 Body Weight and Composition for Health and Sport

alized equations for the calculation of body fat may be found in appendix D for males and females of several ages. Moreover, as noted previously, the GSSI Website provides some skinfold formulae for specific populations. Bioelectrical Impedance Analysis (BIA) A more expensive, practical field technique is bioelectrical impedance analysis (BIA). BIA is based on the principle of resistance to an electrical current that is applied to the body. The less the recorded resistance, the greater the water content, and hence the greater the body density. Early research with BIA revealed large standard errors in predicting lean body mass, so it was not considered to be very valid. However, Going recently noted that current BIA techniques may give valid estimates of total body water and fat-free mass. The BIA instrument may have preprogrammed prediction equations to use, which ideally should include age, gender, and ethnicity; most do not have athlete-specific equations. Going notes that with the proper equation, BIA may be comparable to skinfolds. As noted previously, the GSSI Website provides some BIA formulae for specific populations. Pichard and others recently reported valid BIA formulas for female runners, but recommended research to validate formulas for other athletes. Dual Energy X-Ray Absorptiometry (DXA; DEXA) Dual energy X-ray absorptiometry (DXA or DEXA) is a computerized X-ray technique used to image body tissues and has been used to assess bone mineral content, fat-free mass, and body fat concurrently (see figure 10.5). DEXA may also be used to assess deep visceral fat, as can other sophisticated techniques such as magnetic resonance imaging (MRI) and computed tomography (CT). Moreover, DEXA may measure bone density to detect the presence of osteoporosis. Going notes that DEXA has emerged as a criterion method used to validate other methods. However, he also notes that different manufacturers’ scanners and software give different results, which is the main limitation of DEXA. Infrared Interactance Another device marketed commercially is based upon infrared interactance. In essence, infrared light passes through the tissues, and its interaction with tissue components is used to predict body fat. One commercial model is the Futrex 5000. Wagner and Heyward reported somewhat higher standard errors of measurement with infrared interactance, greater than 3.5 percent. Anthropometry Anthropometry, or measurement of body parts, is an inexpensive, practical method to assess body composition. Body measurements include girths such as the neck and abdomen, and bone diameters such as the hip, shoulders, elbow, and wrist. Girth and bone diameter measurements may be incorporated into various formulas to predict body fat and lean body mass. Girth measurements of the abdomen, hips, buttocks, thigh, and other body parts, may be important indicators of regional fat distribution, which is a concept representing the anatomical distribution of fat over the body. As discussed later, regional fat distribution may be associated with several major health prob-

Dual energy X-ray absorptiometry (DEXA). This method measures body fat by releasing small doses of radiation through the body that a detector then quantifies as fat, lean tissue, or bone.The scanner arm moves from head to toe and in doing so can determine body fat as well as bone density. DEXA is currently considered the most accurate method for determining body fat as long as the person is not too obese to fit on the table and/or under the arm of the instrument.The radiation dose is minimal.

FIGURE 10.5

lems. The principal measure of regional fat distribution is the waist circumference, the abdominal or waist girth measured by a flexible tape at the narrowest section of the waist as seen from the front. The waist circumference is a good screening technique for regional fat distribution, but does not provide an accurate measure of deep visceral fat, such as provided by CT or MRI techniques. Multicomponent Models The multicomponent model uses several methods, such as hydrodensitometry, total body water, and DEXA to reduce the errors associated with any single method and to provide information on body fat, body water, bone mass, and lean body mass. Lohman and Going recommend use of a multicomponent model when assessing body composition in children and youths, including waist circumference, selected skinfolds, and DEXA. Wagner and Heyward note that the multicomponent model is now regarded as the “gold standard” in body composition assessment and should be used when feasible.

What problems may be associated with rigid adherence to body fat percentages in sport? Table 10.1 lists most of the methods used to estimate body composition. Several recent studies have attempted to validate these techniques, usually against the underwater-weighing method, and have shown some significant differences. In one study comparing four different methods, some individuals were estimated to have body-fat percentages that ranged as much as 10 percent depending on the method used, while another study using four different prediction equations with the BIA reported predicted body-fat percentages ranging from 12.2 to 22.8 in gymnasts. In addition, Stout and others cross-validated sixteen skinfold formulas for prediction of body fat in wrestlers, and reported error values of almost 5 percent. Given the fact that the wrestlers in this study averaged 10.8 percent fat, the www.mhhe.com/williams9

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researchers concluded that this level of accuracy is not acceptable. More recently, however, Clark and others found that the NCAA skinfold equation is a valid predictor of body fat, and support the NCAA method of estimating body fat in college wrestlers for establishment of minimum weight. Oppliger and others recently developed new infrared interactance equations to predict body fat in high school wrestlers and noted they are comparable to skinfold equations currently used. However, given the problems with assumptions underlying the various methods of body composition determination, estimates of body-fat percentages are approximations only. The rigid use of body-fat percentages in weight-control sports, such as gymnastics and wrestling, may lead to excessive weight loss. For example, suppose you are a wrestler and your college coach requires you to reach the minimal permitted—5 percent body-fat level. Using a skinfold caliper technique, he finds that you are at 8 percent body fat and suggests that you lose 3 percent more body fat. However, given the standard error of 3–4 percent, you may already be at 5 percent. Losing extra weight may be very difficult because you are already near minimal body-fat levels, so additional weight loss may include muscle tissue that may lead to possible decreases in performance. In young athletes, such practices may also lead to disordered eating and, possibly, clinical eating disorders.

How much should I weigh or how much body fat should I have? That is a complex question, and the response depends on whether you are concerned primarily about appearance, health, or physical performance. From the perspective of physical appearance, you are the best judge of how you wish to look. However, a distorted image may lead to serious health problems or impairment in physical performance. A recent Pew Research Report noted that Americans see weight problems everywhere but in the mirror, not recognizing that they are overweight and may suffer adverse health consequences. Already thin individuals who desire to be even thinner may be prone to eating disorders. Muscular bodybuilders who perceive themselves as not sufficiently muscular may suffer psychologically. The effect of body weight and body fat on physical performance is discussed in a later section, although some general guidelines are presented here. The effect of body weight and fat on health has received considerable research attention. Although being underweight may impair health, most of the focus has been on excess body weight and fat, particularly the relationship of obesity to health. By medical definition, obesity is simply an accumulation of fat in the adipose tissue. Obesity is also referred to as a disease or disorder and is the most common nutritional health problem in North America. The actual measurement and determination of clinical obesity is a controversial issue. Several approaches have been used to define the point at which a person is classified as clinically obese. Unfortunately, our present level of knowledge does not provide us with the ability to predict precisely what the optimal weight or percent body fat should be for health in any given individual. 410

However, some general guidelines have been developed by various professional and health organizations. Body Mass Index As a screening method for health, you may calculate your BMI to assess your body weight. See appendix D or previously mentioned Websites for details. The following are some general guidelines presented by the National Institutes of Health regarding the relationship of BMI to health risks. Keep in mind that these are BMI values, not body-fat percentages, which are discussed in the next section. Below 18.5: May signal malnutrition or serious disease 18.5–24.9: Healthy weight range that carries little health risk 25–29.9: Overweight; at increased risk for health problems, especially if you have one or two weight-related medical conditions Above 30: Obesity, more than 20 percent over healthy body weight; poses high risk to your health These values are in accordance with figures presented by the National Academy of Sciences. Additionally, the Food and Agriculture Organization has proposed the use of a BMI less than 18.5 as a criterion for starvation. Other investigators indicate that a BMI greater than 35 or 40 is classified as severe, clinical, or morbid obesity. An expanded BMI health risk table, in association with waist circumference, is presented later. Body Fat Percentage As noted previously, the use of the BMI height-weight relationship does not evaluate body composition. Thus, health professionals note that there are exceptions to these BMI classifications, indicating that a low BMI may be a symptom of a serious disease, not a cause, and that muscular people may have a high BMI and not be obese. For health purposes, the body has a need for the essential fat described previously. At a minimum essential fat approximates 3 percent for males and 12–15 percent for females. Several authorities have included additional levels of storage fat and suggested that minimal levels of total body fat for health range from 5–10 percent for males and 15–18 percent for females. Lower levels of body fat may be required for optimal performance in certain types of athletic events. Certain male athletes such as wrestlers and gymnasts may function effectively at 5–7 percent body fat. Recommendations have been made for females who compete in distance running to have no more than 10 percent body fat. However, some athletes have performed very successfully even though their body-fat percentage was higher than the recommended values. Although different levels of body-fat percentages have been cited as the criterion for obesity, the American Dietetic Association and the National Research Council set the value at 25 percent for males and 30 percent for females. The National Academy of Sciences, in its new DRI on energy intake, also published criteria for obesity setting the level at 25 percent body fat for males but 37 percent for females; the NAS noted that over 31 percent and 42 percent body fat in males and females, respectively, was indicative of clinical obesity. One national fitness organization has proposed a rating scale, as presented in table 10.2, based on body-fat percentages ranging from essential fat to obesity. Keep several points in mind when using such tables. First, remember that all body-fat prediction

C H A P T E R 1 0 Body Weight and Composition for Health and Sport

TABLE 10.2 One proposed rating scale based

䉴 Our present level of knowledge does not provide us with the

on body-fat percentages Rating

ability to predict precisely what the optimal body composition should be for health or physical performance. However, BMI and body-fat levels higher than normal are associated with increased health risks.

Males

Females

Essential fat

2–5

12–15

Athletic

6–13

16–20

C h e c k f o r Yo u r s e l f

Fitness

14–17

21–24

Acceptable

18–25

25–31

Using appendix D, calculate both your Body Mass Index (BMI) and your waist circumference. Compare your findings to the rating scale in table 10.3.

25+

32+

Overweight/obese

Note: Keep in mind that these are approximate values.The essential category represents fat necessary to meet basic physiological needs.The athletic category may apply particularly to athletes who compete in events where excess body fat may be a disadvantage. See text for additional information.

methods contain a source of error. Second, the athletic category is associated with athletes competing in weight-control sports or sports where excess body fat may be a disadvantage. Third, as noted below, although obesity generally increases health risks, some individuals with higher body-fat percentages may not develop obesity-related health problems if they are otherwise physically fit and consume a healthful diet. Fourth, location of the fat in your body may have significant health consequences. Waist Circumference It may not be how much fat you have that affects your health but where that fat is located. The health implications of regional fat distribution are discussed below, but you may use method C in appendix D to calculate your waist circumference and evaluate associated health risks. As a screening measure for deep visceral fat, increased health risks are associated with waist circumferences greater than 35 inches in females and 40 inches in males. However, as discussed later, lower waist circumferences may be associated with increased risks if accompanied by other conditions, such as high blood pressure. Table 10.3 highlights the risk of chronic disease associated with the BMI and waist size.

Ke y C o n c e p t s 䉴 The Body Mass Index (BMI) does not measure body

composition, but it may be useful as a screening device to determine whether one is overweight or obese. Overweight and obese are not synonymous terms. 䉴 The body consists of four components: body fat, protein, minerals, and water. However, for practical purposes, body composition may be classified as consisting of two components: fat-free weight, which is about 70 percent water, and body fat. 䉴 All techniques that are currently used to measure body composition, primarily body fat, are prone to error; even the underwaterweighing technique, once considered to be the most accurate, may be in error by 2.0–2.5 percent.

TABLE 10.3 Risk of associated disease according

to BMI and waist size

BMI

*Waist less than or equal to 40 in. (men) or 35 in. (women)

*Waist greater than 40 in. (men) or 35 in. (women)

18.5 or less

Underweight



N/A

18.5–24.9

Normal



N/A

25.0–29.9

Overweight

Increased

High

30.0–34.9

Obese

High

Very High

35.0–39.9

Obese

Very High

Very High

40 or greater

Extremely Obese

Extremely High

Extremely High

Source: www.consumer.gov/weightloss.bmi.htm

*Note: Recent research suggests waist sizes greater than 37 inches in men and 31.5 inches in women may increase health risks when accompanied by other conditions, such as high blood pressure.

Regulation of Body Weight and Composition How does the human body normally control its own weight? As noted previously, you may eat over a ton of food—nearly a million Calories—a year and yet not gain one pound of body weight. For this to occur, your body must possess an intricate regulatory system that helps to balance energy intake and output both on a shortterm and a long-term basis. The regulation of human energy balance is complex, involving numerous feedback loops to help control energy balance. At the present time we do not know all the exact physiological mechanisms whereby body weight is maintained relatively constant over short or long periods, but some information is available relative to both energy intake and energy expenditure. www.mhhe.com/williams9

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Hypothalamus 176

18

65

1

4 70

15 KG

KG

S LB

S

7

85

8 19

75

90

LB

80

hormones, neural stimuli from other parts of the body, and environmental cues. Some factors may function to control body weight on a short-term basis while others may exert long-term effects. The following afferent stimuli may be involved in body-weight control in one way or another.

• Senses. Stimulation of several senses like sight, sound, and smell may Set Point influence neural or hormonal activity to stimulate or depress our appetites, even before food is ingested. The sense of taste also has a significant impact on appetite and energy intake. • Stomach fullness. An empty or full stomach may influence mechanical F I G U R E 1 0 . 6 The hypothalamus.This site in the brain does most of the processing of sigstretch receptors in the stomach walls nals regarding food intake. Some theorize the hypothalamus regulates a set point for body weight, that generate neural activity. An comparable to its role as a thermostat in regulating body temperature. Increases in the normal empty stomach may stimulate the body weight would lead to compensations, such as decreased appetite or increased basal metabolic hunger center by various neural pathrate that would lead to weight loss and restoration of normal body weight.The opposite would ways, whereas a full stomach may occur with decreases in the normal body weight. stimulate the satiety center. The stomach may also release hormone-like substances that stimuEnergy Intake George Bray, an international authority on late or diminish hunger. weight control, indicates that food intake is a regulated system. • Blood nutrient levels. Nutrient levels in the blood may be able to The central nervous system, the brain in particular, is the center for influence receptors in the hypothalamus. Receptors in the hypoappetite control, either creating a sensation of satiety or stimulatthalamus, liver, or elsewhere may be able to monitor blood leving food-seeking behavior. However, its activity is dependent els of various nutrients. In regard to this, three theories center on upon a complex array of afferent signals from various body systhe three energy nutrients. The glucostatic theory suggests that tems. The interaction of the brain with these afferent signals helps food intake is related to changes in the levels of blood glucose. regulate the appetite on a short-term (daily) basis, or on a longFehm and others indicated that a fall in blood glucose will stimterm basis, as in keeping the body weight constant for a year. ulate glucose-sensitive neurons in the hypothalamus and The forebrain is involved in the conscious selection of foods we increase appetite whereas an increased blood glucose level will eat, while the brainstem controls the motor aspects of eating, such decrease appetite. The lipostatic theory suggests a similar as chewing and swallowing. Between these two structures lies the mechanism for fats as does the aminostatic theory for amino hypothalamus, a small substructure that appears to be the center for acids, or protein. In essence, by-products of carbohydrate, fat, appetite control (see figure 10.6). You may recall from the last and protein metabolism may influence production of neurochapter that the hypothalamus is also involved in body-temperature transmitters that influence appetite, such as serotonin and norepcontrol, involving neural receptors that function as a thermostat to inephrine, in the hypothalamus. either stimulate energy (heat) production or loss. In a similar fash• Body temperature. A thermostat in the hypothalamus may ion, the hypothalamus may contain neural centers that help regulate respond to changes in body temperature and influence the feedappetite, often referred to as an appestat. In general, the appestat ing center. For example, an increase in body temperature may contain a hunger center that may stimulate eating behavior, inhibits the appetite. and a satiety center which when stimulated will inhibit the hunger • Hormones and neuropeptides. A number of different hormones center. As a means of controlling energy intake, specific neural and neuropeptides (neurotransmitters) in the body have been receptors within the appestat monitor various afferent stimuli that shown to affect feeding behavior, including insulin, serotonin, may stimulate or inhibit the appetite. These stimuli may come from norepinephrine, leptin, ghrelin, cortisol, and thyroxine. As disthe stomach, intestines, muscle, fat depots, pancreas, liver, and cussed later, some hormones may function on a short-term other body tissues and organs, and are integrated and interpreted by basis to help control meal size, whereas other hormones may be the hypothalamus and directed to other brain centers and body involved in long-term regulation of body weight. organs to help maintain energy balance. Woods suggests one of these brain centers may involve receptors that induce sensations of pleasure, which may increase the desire to consume food. As depicted in figure 10.7, various stimuli may influence the appetite, including blood levels of various nutrients, metabolites, 412

Energy Expenditure Although all of the above may be involved in the physiological regulation of food intake, the other side of the energy-balance equation is energy expenditure, or

C H A P T E R 1 0 Body Weight and Composition for Health and Sport

Energy input

H Y P O T H A L A M U S

Energy output

Control center for autonomic nervous system and master endocrine gland

DIET EXERCISE

Hunger control center

Vision, taste and smell

Muscle Cells

Satiety control center

Level of stomach fullness

Fat cells

Temperature control center

Blood levels of glucose, fats, amino acids, hormones, and adipokines

Liver

Small intestine

DIET EXERCISE

DIET

F I G U R E 1 0 . 7 Basic control mechanisms for body weight. Although other parts of the brain are involved, the control of food intake (energy intake) and resting metabolism (energy output) is governed primarily by the hypothalamus in the brain.The numerous control centers in the hypothalamus are influenced by feedback from the body, such as the blood concentrations of glucose and other nutrients. In turn, food intake and energy expenditure may influence the hypothalamus. For example, exercise will stimulate the hypothalamus, leading to the secretion of several hormones by the endocrine glands in the body.The effects of exercise will also influence the temperature control center and the blood levels of several nutrients, which will in turn influence the hypothalamus. See the text for an expanded discussion.

metabolism. Although exercise is one way to increase energy expenditure, the vast majority of the energy that is expended by the body on a daily basis is accounted for by the basal energy expenditure (BEE) or resting energy expenditure (REE), as was detailed in chapter 3. Changes in the REE may be involved in the regulation of body weight. Several mechanisms of body-weight regulation have been proposed. • Brown fat. Brown fat, which is distinct from the white fat that comprises most fat tissue in the body, is found in small amounts around the neck, back, and chest areas. It has a high rate of metabolism and releases energy in the form of heat without ATP production. Basically, uncoupling proteins (UCP) in brown fat uncouple respiration from oxidative phosphorylation

and convert fuel to heat without producing ATP. Activity of the brown fat tissue may be increased or decreased under certain conditions, such as after a meal or exposure to the cold. This activity is referred to as nonshivering thermogenesis. Research with rats has indicated low levels of brown fat are associated with a higher incidence of dietary-induced obesity. The amount of brown fat in humans appears to be small (about 1 percent of body fat or less) but Stock indicates that as little as 50 grams (about 2 ounces) could make a contribution of 10–15 percent energy turnover in humans. Its role in the etiology of human obesity is controversial and is being researched. • White fat tissue and muscle tissue. UCP are also found in other tissues. In a recent review, Melby and others noted that both white adipose tissue and muscle tissue may also experience thermogenesis without ATP production under conditions of high energy intake, particularly as dietary fat. • Hormones. Levels of hormones from the thyroid and adrenal glands may rise or fall and affect energy metabolism accordingly. Triiodothyronine and thyroxine, hormones from the thyroid gland, may be involved in the stimulation of brown adipose tissue. Hormones, such as epinephrine, also may increase the activity of certain enzymes resulting in increased energy expenditure. Decreases in such hormonal activity may depress energy metabolism. Other hormones may stimulate or depress thermogenesis in adipose or muscle tissues. • Nonexercise activity thermogenesis (NEAT). Levine indicates that nonexercise activity thermogenesis (NEAT) is the energy expended for everything we do that is not sleeping, eating, or sports-like exercise. Varying levels of NEAT could have a significant impact on daily energy expenditure. Feedback Control of Energy Intake and Expenditure As noted in an earlier chapter, the human body has developed a number of physiological systems, called feedback systems, to regulate most body processes. Temperature control is a good example. Feedback systems controlling body weight may operate on both a short-term (daily) and long-term (yearly) basis. Short-term control mechanisms may either decrease or increase food intake. For example, as the stomach expands while eating a meal, nerve impulses are sent from receptors in the stomach wall to the hypothalamus to help suppress food intake. Additionally, Moran notes that during and after a meal the ingested nutrients alter the release of a variety of peptides from the stomach, intestines, and pancreas. Peptides such as cholecystokinen, pancreatic glucagon, obestatin, and amylin are released rapidly with eating and have short actions leading to meal termination. Body stores of carbohydrate, protein, and fat are also regulated on a short-term basis. The human body has a limited capacity to store excess carbohydrate and protein, so changes in blood glucose and amino acid levels help regulate carbohydrate and protein intake. Although the human body possesses a high capacity to store fat, blood lipids and other factors help maintain body-fat balance on a short-term basis. However, Stubbs indicated that although dietary protein and carbohydrate exert potent effects on satiety, dietary fat is less satiating and may lead to excess energy intake. Other shortterm mechanisms increase food intake. For example, ghrelin is a www.mhhe.com/williams9

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peptide hormone released by the stomach, mainly before mealtime when the stomach is relatively empty. Ghrelin acts on the hypothalamus to stimulate the appetite. On a long-term basis, the set-point theory of weight control is a proposed feedback mechanism. This theory proposes that your body is programmed to be a certain weight, or a set point, something comparable to a set body temperature of 98.6°F. If you begin to deviate from this set point, your body will make metabolic Adipose adjustments to return you to normal. This is often cells referred to as adaptive thermogenesis, which can either increase or decrease energy production to generate heat. Although developed primarily with rats and still only a theory, the set-point concept does involve the interaction of those factors cited previously, particularly the lipostatic theory, which may influence energy intake and expenditure in humans. Keesey and Hirvonen indicate that the hypothalamus appears to play the primary role in establishing the set point for body weight, while Fehm indicates the hippocampus may also be involved. In several reviews, Levin noted that the brain has special sensing neurons which are involved in the control of energy homeostasis. In particular, Levin notes that neuropeptide Y (NPY) neurons in the hypothalamus represent an example of a neuron capable of sensing both glucose and a host of other peripheral metabolic signals, such as leptin. Leptin, an adipokine, is a regulating peptide hormone encoded and produced by the OB gene in the adipose cells. Klok and others note that leptin is a mediator of long-term regulation of energy balance, suppressing food intake and thereby inducing weight loss. Leptin helps to decrease appetite. Long-term imbalances in body weight are usually reflected by changes in bodyfat stores. The more body fat you have, the more leptin you produce; conversely, less leptin is produced when body-fat stores are low. When leptin is released into the blood, it circulates to the hypothalamus and is believed to inhibit the production of NPY (see figure 10.8). NPY is a potent stimulant of food intake and also acts to reduce energy expenditure by decreasing the REE. Thus, as you begin to accumulate body fat your fat cells produce more leptin, which then circulates to the hypothalamus and depresses the formation of NPY. Because NPY stimulates food intake and depresses energy expenditure, decreased levels of NPY will suppress hunger and reduce voluntary food intake, and may also stimulate increases in REE by activating thermogenesis in adipose and muscle tissues. Thus, your body reacts to the increased body fat by decreasing energy intake and increasing energy expenditure. Conversely, if you decrease body fat rapidly via dieting, leptin production is decreased, reducing the inhibitory effect on NPY production. Increased levels of NPY stimulate hunger and reduce energy expenditure, thus resisting the effect of the diet and promoting restoration of the lost weight. Baile notes that leptin and its receptors provide the molecular basis for the lipostatic theory of energy-balance regulation proposed 40 years ago, namely that circulating factors generated in proportion to body-fat stores act as signals to the brain and elicit changes in energy intake and expenditure. 414

Gene Leptin Blood circulation

NPY

Hypothalamus

F I G U R E 1 0 . 8 One possible mechanism of the set-point theory. Leptin is produced in proportion to body-fat stores.When body fat increases, more leptin is released into the bloodstream, circulates to the hypothalamus, and inhibits the formation or release of neuropeptide Y (NPY). NPY is a potent stimulator of food intake and may also decrease energy expenditure.

Less research has been conducted relative to feedback control of physical activity, but Rowland proposed an activity-stat, a center in the brain that functions as a set-point to increase or decrease physical activity. If substantiated, such a center could also support the set-point theory of body-weight control. Although the set point is a theory, it may help explain why some people maintain a normal body weight throughout life.

How is fat deposited in the body? The actual deposition of fat in the human body may occur in two ways: hyperplasia (an increase in the number of adipocytes, or fat cells), or hypertrophy (an increase in the amount of fat in each cell). Earlier research appeared to support the theory that hyperplasia is a major cause in the development of childhood obesity whereas hypertrophy is the primary cause in adulthood. However, Avram and others recently noted that the development of obesity is dependent on the coordinated interplay of an increased fat cell size as well as an increased fat cell number, and evidence suggests that adipocyte hyperplasia occurs throughout life, both in response to normal cell turnover as well as in response to the need for additional fat mass stores that arises when caloric intake exceeds nutritional requirements. Existing fat cells apparently have a maximal size potential (about 1 microgram of fat per cell), which when exceeded stimulates the formation of new fat cells or the accumulation of fat in preadipocytes, small cells in the adipose tissue that have the potential to become adipocytes. Thus, although a genetic predisposition to inherit a greater number of fat cells, thereby facilitating the development of obesity, may exist, individuals without this genetic predisposition may still become obese with a positive energy balance stored as fat. Interestingly, Pi-Sunyer indicated that once fat cells are formed, the number seems to remain fixed even if weight is lost. To lose body fat, one must reduce the amount of fat in the adipose cells to normal, or even below normal.

C H A P T E R 1 0 Body Weight and Composition for Health and Sport

What is the cause of obesity? A recent National Geographic cover story asked the question, Why are we so fat? The answer is simple, but the devil is in the details. Energy processes in the human body, like those of other machines, are governed by the laws of thermodynamics. If the human body consumes less energy in the form of food Calories than it expends in metabolic processes, then a negative energy balance will occur and the individual will lose body weight. Conversely, a greater caloric intake in comparison to energy expenditure will result in a positive energy balance and a gain in body weight. In simple terms, obesity is caused by this latter condition of energy imbalance. Although the first law of thermodynamics provides the basic answer as to how we get fat, it does not provide any insight relative to the specific mechanisms. Claude Bouchard, a prominent international authority on obesity and weight control, noted that at this time there is no common agreement on the specific determinants of obesity, stressing that numerous factors are correlated with bodyfat content. In general, most leading obesity scientists, such as Grundy, support a multicausal theory involving the interaction of a number of genetic and environmental factors. Genetic Factors Heredity appears to be a very important factor in the etiology of obesity, particularly morbid obesity. For example, several genetic diseases result in clinical obesity. Also, studies of adopted children, including both fraternal and identical twins who were separated and adopted by different families, have shown a greater relationship of the body composition between the children and their biological parents as compared to the adoptive parents. For a review of two meticulous studies of the genetic role in obesity, the interested reader is referred to the reports by Bouchard and others on long-term overfeeding of identical twins, and by Stunkard and others on the Body Mass Index of twins who were raised apart. Based on his and others’ research, Bouchard indicated that genetic heritability of obesity approximates 25–40 percent. It appears heredity may determine those internal factors in the body that may predispose one to gain weight. Research into the genetics of obesity has been progressing at a rapid pace. Hirsch and Leibel note several obesity genes have already been identified, which in some persons may maintain an unhealthful set-point. Levin cites one possibility, suggesting that individuals with a genetic susceptibility to obesity may be predisposed to abnormalities in neural function. They establish neural circuits that are not easily abolished. In essence, obesity genes influence appetite to increase energy intake or affect metabolism to decrease energy expenditure. For example, genes in the hypothalamus may decrease the number of protein receptors for leptin, causing leptin resistance, thus preventing leptin from inhibiting the formation of NPY. NPY may then stimulate the appetite. Also, as noted previously, a protein known as the uncoupling protein (UCP) is believed to activate thermogenesis; UCP1 activates thermogenesis in brown fat, whereas UCP2 activates thermogenesis in white fat and muscle tissue. Defects in UCP genes may decrease resting energy expenditure. Over 340 genes may be involved in weight control. Rankinen and others have developed a human obesity gene map whose pur-

pose is to identify loci on chromosomes associated with the development of obesity in humans; the map is updated annually. Genetic factors that have been implicated in the development of obesity include the following: • • • • • • • • • • • • •

a predisposition to sweet, high-fat foods impaired function of hormones such as insulin and cortisol decreased levels of human growth hormone low plasma leptin concentrations leptin resistance inability of nutrients or hormones in the blood to suppress the appetite control center a greater number of fat cells an enhanced metabolic efficiency in storing fat a lower REE a decreased TEF low rates of fat oxidation lower levels of spontaneous physical activity, or NEAT, during the day lower levels of energy expenditure during light exercise

Wells indicates that the capacity to accumulate fat has been a major adaptive feature of the human species, but is now increasingly maladaptive in our modern environment. Some scientists have coined the term the “thrifty gene” to indicate an increased efficiency in the obese to conserve energy, and they consider obesity a metabolic disease. Environmental Factors Although heredity may predispose one to obesity, environmental factors are also highly involved. Capturing the role of environmental factors in a nutshell, Wadden and others indicated that the marked increase in obesity worldwide appears to be attributable to a modern society that explicitly encourages the consumption of supersized portions of high-fat, high-sugar foods while implicitly discouraging physical activity. In particular, Mendoza and others concluded in their review that dietary energy density is a major predictor of obesity. Consuming a high-Calorie diet, either high or low in fat, may lead to excess caloric intake and weight gain. Moreover, Cohen and Farley contend that eating may be an automatic behavior over which the environment has more control than does the individual. The amount of food eaten is strongly influenced by factors such as portion size, food visibility, and the ease of obtaining food. High-Fat, High-Calorie Foods Excess Calories, or overfeeding, may lead to obesity. For example, Pearcey and de Castro evaluated eating behavior and activity levels of weight-gaining and weight-stable men and women, and found that the basic difference was that the weight-gaining individuals consumed about 400 more Calories per day during the period of active weight gain. Eating fast foods may be an important contributing factor. Ebbeling and others note that nutritional factors inherent to fast food, such as high palatability, high-fat content, high content of sugar in liquid form, and high energy density, promote excess energy intake. Additionally, fast foods are relatively inexpensive, mainly because fat and sugar are the cheapest source of Calories www.mhhe.com/williams9

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on earth, and thus are generally high in fat and Calories. Two longitudinal studies linked fast-food consumption with weight gain. In the National Longitudinal Study of Adolescent Health, Niemeier and others reported that fast-food consumption was associated with increased weight gain from adolescence to adulthood. In a 15-year prospective study, Pereira and others found that those who ate at fast-food restaurants more than two times a week gained about 10 pounds more than their peers who dined at such places less than once a week. The fast-food consumption had strong positive associations with weight gain and insulin resistance, suggesting that fast food increases the risk of obesity and type 2 diabetes. Although an excess of caloric input over output will lead to a weight gain, researchers suggest that the main culprit in the diet that leads to obesity is dietary fat. For various reasons, the National Academy of Sciences concluded that higher fat intakes are accompanied with increased energy intake and therefore increased risk for weight gain in populations that are already disposed to being overweight and obese, such as that of North America. Obesity researchers have postulated several of these reasons. First, dietary fat is highly palatable to most individuals, stimulating hedonistic responses and encouraging overconsumption. Dietary fat contains more Calories per gram, and may not provide the same satiety as carbohydrate and protein. Gibbs noted that the body systems respond quickly to protein and carbohydrates but slowly to fat, too slowly to stop ingestion of a high-fat meal before the body has had too much. Green and Blundell also note that high-fat foods give rise to higher energy intake during a meal than do carbohydrate foods, and Calorie for Calorie are less effective in suppressing subsequent food intake. In support of this point, Shah and Garg reported that spontaneous energy intake is higher on an unrestricted high-fat diet compared to a high-carbohydrate diet. Second, dietary fat may be stored as fat more efficiently compared to carbohydrate and protein. It takes some energy to synthesize fat and store it in the adipose tissue, but Dattilo noted that in comparison to dietary fat, it may cost up to three or four times more energy to convert carbohydrate and protein to body fat. Third, other investigators indicate that chronic intake of a high-fat diet will produce resistance in the hypothalamus to various factors that normally suppress appetite, such as leptin, the end result being increased energy intake and body-fat deposition. The interested student is referred to the reviews by Dattilo, Tso and Liu, and Rolls and Shide regarding the relationship of dietary fat to body weight. Low-Fat, Large-Portion Size, High-Calorie Foods Although excess dietary fat, for reasons cited, may be a major culprit in the etiology of obesity, researchers such as Willett have noted that the prevalence of obesity in the United States has increased dramatically over the past two decades even though the energy derived from dietary fat has actually decreased, both in absolute terms and in percent of total dietary energy. One reason for this apparent inconsistency may be an increased daily Calorie intake. Fat-free does not mean Calorie-free. Kelly Brownell, an obesity expert from Yale University, indicated that our society promotes eating, mainly fast foods, to excess. Appetizing low-fat, but high-Calorie

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food is everywhere, and in supersize proportions which significantly increase caloric content. At latest count there are over 300,000 packaged foods available, and a large supermarket may carry 50,000 or more. Portion sizes have increased dramatically; what was once small is now large. Liquid Calories appear to be involved in weight gain. Think about it. A 12-ounce sugar-sweetened soda contains the equivalent of 10 teaspoons of table sugar, or about 150 Calories. However, portion sizes have changed over the years. Today, the average soft drink is more than 50 percent larger compared to past years, containing more sugar and Calories. Geier and others report that people consume food on a “unit” basis. If you buy and consume a 20-ounce bottle of soda, which is one unit, rather than a 12-ounce bottle, you will consume about an additional 100 Calories. Flood and others reported that Americans drink about 22 percent of their total daily caloric intake, many from sweetened high-carbohydrate beverages, and do not compensate by eating less solid food at meals. In their review of 30 high-quality studies, Malik and others found that the weight of epidemiologic and experimental evidence indicates that a greater consumption of sugar-sweetened beverages is associated with weight gain and obesity. In a recent experimental study, Ebbeling and others reported that replacing sugar-sweetened beverages with noncaloric beverages in the diets of adolescents with high BMI values over the course of 25 weeks reduced their BMI levels compared to a similar group that continued to consume sugar-sweetened beverages. Consuming sugar-sweetened drinks per se may not be a cause of obesity, but it may be one avenue to exceed recommended caloric intake. Sugar-sweetened beverages are rather inexpensive, which is one possible reason that leads to increased intake. With excess dietary Calories, Melby and Hill indicate that it is possible for an individual to become obese on a low-fat diet because the body rapidly adjusts to oxidizing excess dietary carbohydrate and protein to meet its energy needs, sparing the use of body-fat stores. Jacobs and others also indicate that significant amounts of body fat may be generated from excess dietary carbohydrate. Recent research by Ma and others indicates that a highglycemic index diet is associated with increased body weight, but confirming data are needed. The FDA recently reported that compared to 15 years ago, the average American consumes 300 more Calories daily. These additional Calories are derived mainly from carbohydrates, such as cookies and soda. An additional 300 Calories daily would lead to a weight gain of about one pound in 12 days. Physical Inactivity and NEAT Although the epidemic of obesity development may be associated with excess consumption of energy-dense foods, Astrup suggests it also may be explained by concomitantly decreasing levels of physical activity. Modern technology is wonderful, helping to make our lives more comfortable and enjoyable in numerous ways. However, technology may also exert a negative effect on our health, as the development of television, computers, and other labor-saving devices may decrease levels of physical activity. In a review, DiPietro noted that the influence of regular physical activity on body composition is complex. However, although there are some methodological problems with the epidemiological research, DiPietro indicated that several

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cross-sectional studies have reported an inverse relationship between physical activity and body weight; that is, those who were physically inactive weighed more. DiPietro and other reviewers, such as Saris, noted that physical activity and exercise is an important factor in the prevention of overweight or obesity. Furthermore, de Groot and van Staveren indicate that once an individual becomes obese, physical activity decreases, setting up a vicious cycle of increasing body weight and even less physical activity. Levine contends that the variability in total daily energy expenditure is attributed mainly to nonexercise activity thermogenesis (NEAT). Technology has decreased the amount of energy we normally expend via NEAT each day, such as walking, standing, and even fidgeting, which may lead to an energy imbalance and weight gain. Researchers followed lean and mildly obese people for 10 days, reporting those who were mildly obese stayed seated for about 2.5 hours longer per day than the lean individuals; they indicated that this could amount to 350 fewer Calories expended daily. Watching television or other such sedentary seated behaviors decrease NEAT, which Levine indicates may be of profound importance in the development of obesity. In a recent review, Levine and others reported that NEAT varies substantially between people, as much as 2,000 Calories per day. Other environmental factors Other environmental factors may predispose to weight gain. Sleep Reduced amounts of sleep are associated with overweight and obesity. Some researchers suggest that lack of sleep may increase serum levels of ghrelin and decrease levels of leptin, which would increase appetite and body weight. However, in a prelude to their study involving the role of exercise in sleep, Littman and others reported no consistent cross-sectional patterns between self-reported sleep measures and ghrelin or leptin. Other factors may be involved. Vorona and others indicate that lack of sleep may cause one to be more tired and less likely to exercise, and being awake longer will provide more chances to eat. Moreover, being overweight may increase the incidence of sleep apnea, a situation in which breathing stops and normal sleep patterns and sleep quality may be disturbed. Emotional stress Emotional stress may also lead to weight gain. Stress may trigger the release of various hormones, particularly cortisol. Dallman and others indicate that cortisol has a major stimulatory effect on caloric intake, and also may redistribute stored energy preponderantly into intraabdominal fat depots. In essence, the body perceives stress as an emergency and responds by attempting to conserve energy by eating more and storing fat. Certain drugs may increase body weight. For example, asthmatics may use oral corticosteroids, whose use is associated with weight gain. Two important factors may be the use of social drugs, alcohol and nicotine. Personal relationships Social and family relationships may contribute to weight gain. In a recent study, Christakis and Fowler studied the role of friendship on weight gain in 12,000 subjects over the course of 32 years. They reported that a person's chances of becoming obese increased by 57 percent if he or she had a friend who became obese in a given interval. Among pairs of adult

siblings, if one sibling became obese, the chance that the other would become obese increased by 40 percent. If one spouse became obese, the likelihood that the other spouse would become obese increased by 37 percent. They concluded obesity appears to be spread through social ties. Although not tested in their study, the possibility of a similar relationship may occur among friends or family who maintain a healthy body weight. Drugs Alcohol is rich in Calories. At 7 Calories per gram, it is comparable to a gram of fat, which contains 9 Calories. The National Academy of Sciences has noted that if the energy derived from alcohol is not utilized, the excess is stored as fat. Moreover, Tremblay and others reported that concurrent alcohol intake does not suppress the appetite nor does it suppress fat intake. Thus, the Calories in alcohol are additive and may lead to an energy surplus and weight gain. Nicotine in cigarettes is a stimulant that may inhibit the appetite and increase REE. Froom and others reported that smokers who quit gained weight (about 11–13 pounds), mostly in a 2-year period immediately following smoking cessation. It is interesting to note that teenagers concerned with weight control and dieting are more likely to start smoking. Although it may be helpful in weight control, smoking carries major health risks itself and there are healthier, more effective methods available. Interaction of Genetics and Environment Perusse and Bouchard indicated that genetic factors play an important role in weight control. Although this is so, Grundy noted that the rapid increase in obesity in the United States over the past 20 years cannot be attributed to genetic changes over such a short time frame, indicating that the environment is more important in the development of moderate obesity. Peters and others support this viewpoint, noting that human physiology developed to function within an environment where high levels of physical activity were needed in daily life and food was inconsistently available. The current environment is characterized by a situation whereby minimal physical activity is required for daily life and food is abundant, inexpensive, high in energy density, and widely available. Many individuals who have maintained a normal body weight during childhood and adolescence begin to put on weight gradually in young adulthood (ages 20–40). The basic cause of this creeping obesity, as depicted in figure 10.9, is usually an increased consumption of Calories, particularly fat Calories, and a decreased level of physical activity, or a combination of the two. In a major epidemiologic study, Simoes and others reported that dietary fat intake and physical activity were strongly and inversely associated, meaning those who ate the most fat had the least physical activity. For young college students, weight gain may be more rapid due to lifestyle changes (i.e., a high-fat, high-Calorie diet and decreased physical activity) during the first year of college life. Although the proverbial “freshman fifteen” suggested freshmen gained 15 pounds during the first year of college, recent studies led by Hoffman, Morrow, and Delinsky and Wilson have shown such weight gains to be somewhat less, ranging from about 2 to 7 pounds. Brown reported that although research studies revealed an average gain of less than 5 pounds (2.268 kg), the popular press publications exaggerated the gain to 15 pounds (6.804 kg).

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F I G U R E 1 0 . 9 Adult-onset obesity is often referred to as creeping obesity, for it creeps up on adults slowly. As little as 200 additional Calories per day above normal requirements would result in a gain of approximately 20 pounds of body fat in 1 year.

Also, several studies have shown that the risk of developing obesity is directly related to the amount of time spent watching television, a sedentary activity usually accompanied by consumption of high-Calorie snack foods.

Can the set point change? If the set-point theory is valid, why do some people attain and maintain body weights higher than their set point? Keesey and Hirvonen indicate that an individual’s set-point is apparently adjustable, possibly shifting with changes in the hypothalamus. Some investigators have proposed a new theory, the “settlingpoint” theory. The settling-point theory suggests that the set point may be modified, and in the case of weight gain, set at a higher level. Gibbs indicates that whatever genes we have that make us susceptible to obesity settle into a happy equilibrium with our environment. For example, a chronic high-fat diet may modify our genes, possibly increasing leptin resistance, and our body weight rises to a new level. Gibbs provides an example of the Pima Indians living in the United States and Mexico. Both groups have similar genetic backgrounds, yet the Pima Indians living in

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the United States who consume a high-fat diet are generally obese, while the Pima Indians living in Mexico who consume a grain/vegetable-based diet are generally normal weight. On the other hand, a weight-loss diet may lower the set point to help maintain body weight at a lower level. Weinsier and others found that caloric restriction in obese women induced a transient decrease in REE, which would be counterproductive to weight loss. However, metabolism returned to normal at the completion of the weight-loss program when energy intake was then adequate to maintain the reduced body weight, suggesting that the set point may settle to a lower level over time. Changes in environmental conditions, such as the diet, may help change neural circuits involved in weight control. Clearly, genetics and environment interact to influence body weight and composition, possibly by their interactive effects in establishing a body weight set point. However, Major and others note that the epidemic of obesity is developing faster than the scientific understanding of an efficient way to overcome it, as reflected by the low success rate of shortand long-term weight loss interventions. From a clinical standpoint, this suggests that the body tends to defend a set point. Prevention of obesity may be the key strategy.

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Why is prevention of childhood obesity so important? As noted previously, there is an obesity epidemic in the United States, and it is affecting children as well as adults. Wang and Beydoun indicate that the percentage of children who will be overweight or obese will increase from 16 percent today to 24 percent in 2015. Once an individual is obese, treatment is not very effective. Levin notes that neural circuits predisposing to obesity are not easily abolished. Most scientists agree that prevention of obesity is of prime importance, particularly in childhood. Gibbs speculates that there must be a window of opportunity in childhood where the environment influences the set point. Probably the earlier, the better. Nader and others, in a longitudinal 12-year study, found that obesity persists from preschool through elementary school and into young adolescence. Children who are chubby at an early age are likely to remain so though childhood and into adolescence. Nevertheless, prevention at any stage of childhood and adolescence is an important consideration, and as with adults, diet and exercise are two key factors. However, the role of diet and physical activity in the development of obesity during childhood is not totally clear. Of the two, an improper diet appears to be the major problem. There may be a familial factor involved here, as the child may be raised in a family where high-fat meals and overeating are common, as suggested in a study by Fisher and Birch. Also, the supermarket diet of today makes it easy for children to consume large amounts of Calories. Sugar and fat are found in a wide variety of foods that we eat and constitute about 50 percent of our daily caloric intake. In particular, Moreno and Rodríguez found that consumption of sugar-sweetened drinks is associated with obesity in children. Bowman also reported fast-food consumption has increased fivefold among children since 1970, noting that children who ate fast food on a regular basis (2 days/week) consumed 187 more daily Calories, which total up to about six pounds more per year. Although some studies have shown that obese children do not consume more Calories than their nonobese peers, the data were not collected during the period when the obese children were gaining weight. Studies in which the investigators actually lived with the children suggest that the obese child does eat more, and also eats faster. Bar-Or and others, in a meeting of experts on physical activity and obesity in children, indicated that physical inactivity may be one cause of juvenile obesity. In children, studies have shown that body weight and the amount of time spent watching television are directly related; that is, the more television is watched the greater the body weight. For example, Andersen and others reported that boys and girls who watch 4 or more hours of television daily have significantly more body fat than those who watch less than 2 hours. However, Marshall and others indicated that relationships between sedentary behavior and youth obesity are unlikely to be explained using single markers of inactivity, such as TV viewing. Thus, watching television per se may not contribute to obesity because any sedentary activity over the same amount of time would produce similar effects. Being physically active during this time frame would burn Calories and help deter weight gain. In

support of this concept, O’brien and others conducted a longitudinal 12-year study and found that how children spent after-school time was an important factor associated with weight gain. They concluded that children who are more physically active and spend less time watching television after school are less likely to become overweight by age 12. The effects of physical inactivity and diet may be intertwined. For example, Wiecha and others studied children in five public schools and concluded that increases in television viewing are associated with increased caloric intake, primarily from energy-dense, low-nutrition foods frequently advertised on television, such as baked snacks, candy, fast foods, and sugar-sweetened beverages. Each hour increase in television viewing was associated with consumption of an additional 167 Calories, which over time could lead to gains in body fat. Russell Pate, an expert in youth fitness, noted the true potential for preventing obesity through physical activity is not known, but some data suggest physical activity and body fatness are moderately and inversely related in youngsters. Research by Bernard Gutin has shown that exercise, independent of diet, may lead to weight loss in obese children. Exercise is important for weight control, as will be documented in the next chapter. As Hills and others note, habitual physical activity established during the early years may provide the greatest likelihood of impact on health and longevity. Individuals with a genetic tendency to obesity do not necessarily have to become obese. Individuals with a weak predisposition to obesity may become obese. Although genetics plays an important role in the etiology of obesity, a desirable body weight may be achieved and maintained in those individuals so predisposed. It may be more difficult and may involve a lifetime of vigilance, but it can be done with an appropriate program of diet and exercise, and the time to start is during childhood. http://www.phe.queensu.ca/epi/obesity/presentations.htm Access this Website for the presentations at the 2007 International Conference on Physical Activity & Obesity in Children held in Toronto, Canada.

Ke y C o n c e p t s 䉴 The brain’s hypothalamus appears to be the central control mech-

anism in appetite regulation, which involves a complex interaction of physiological and psychological factors. Neural and hormonal feedback from the senses, gastrointestinal tract, adipose cells, and other body organs help to drive hunger or signal satiety. 䉴 Although the ultimate cause of obesity is a positive energy balance, the underlying cause is not known but probably involves the interaction of many genetic and environmental factors.

C h e c k f o r Yo u r s e l f As you go about your normal activities for a day, pay particular attention to environmental conditions that may be conducive to consuming high-Calorie foods and discouraging physical activity. Compare your results with those of your classmates.

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Weight Gain, Obesity, and Health Obesity contributes to health problems in several ways. First the increased mass of adipose tissue places extra strain on body systems, such as the heart and the joints. Second, as noted previously, fat cells secrete hormone-like substances called adipokines (adipocytokines) into the bloodstream which may affect metabolic processes; some of these effects are pathogenic, such as increased insulin resistance and inflammation in the blood vessels. Increased fat cell number and size may secrete more of these pathological adipokines. Third, body fat cells may also convert androgen hormones into estrogen hormones, which may influence cellular processes. Given these possible effects, Bays and others suggest pathogenic adipose tissue is no less a disease than diseases of other body organs.

What health problems are associated with overweight and obesity? Recent reviews have listed numerous health problems and associated risk factors associated with obesity. Some of these listed health problems are associated with the strain of the increased body mass, some with the metabolic effects of adipokines or estrogen, some with psychological processes, and some with an interaction of several of these factors. Asthma Cancer Cardiovascular disease Diabetes (type 2) Dyslipidemia Gallstones Gastrointestinal reflux disease Gout Hypertension Insulin resistance Low self-image and self-esteem Osteoarthritis Respiratory dysfunction Sleep apnea Social disabilities Stroke Vertebral disk herniation According to the Centers for Disease Control and Prevention, the health costs of obesity parallel those associated with smokingrelated disease. The American College of Sports Medicine noted that an estimated $100 billion, or 5–10 percent of healthcare costs, is spent on obesity-related conditions annually. The majority of these healthcare costs appear to be associated with the two main chronic diseases associated with obesity, namely cardiovascular disease and cancer. Cardiovascular Disease and Related Health Risks The primary health condition associated with excess body fat is coronary heart disease (CHD). Eckel and Krauss reported that the American Heart Association has classified obesity as a major risk factor for 420

CHD. Quantifying this risk, Kolotkin and others reported that for every one-point increase in the BMI, heart failure risk increased 5 percent in men and 7 percent in women, and indicated that obesity is, in and by itself, a risk factor for heart failure. Some adipokines may be involved in the etiology of cardiovascular disease. Recent reviews by Pi-Sunyer and Fantuzzi and Mazzone indicate that adipokines may directly influence homeostasis in heart blood vessels by influencing the function of endothelial cells, arterial smooth muscle cells, and macrophages in the vessel wall. Some of these effects may be beneficial, while others may be harmful to heart health. For example, Pi-Sunyer has noted that adiponectin has potent anti-inflammatory and anti-atherogenic properties while other adipokines, such as tumor necrosis factor (TNF), may promote inflammation and clotting, two factors contributing to atherosclerosis. Pi-Sunyer notes that adiponectin levels are usually lower in obese individuals, while TNF and other atherogenic adipokines may be elevated. Excess body fat also increases the risk of developing high blood pressure, hypercholesterolemia, and diabetes, all of which are risk factors leading to the development of CHD. In particular, obesity increases the risk of type 2 diabetes, whose rate has increased dramatically over the past decade in concert with the parallel increase in obesity. Shape Up America, a nonprofit organization that promotes a healthy body weight, has coined the term Diabesity™ to highlight the relationship between the two. Trayhurn and Beattie report that adipose tissue secretes an adipokine called resistin, which is reported to induce insulin resistance, linking diabetes to obesity. The greater the amount of adipose tissue, the greater potential for diabetes. Gibbs reports that obesity increases the risk of Type 2 diabetes by an astonishing 1,480 percent with a BMI of 27–29, 2,660 percent with a BMI of 29–31, 3,930 percent with a BMI of 31–33, and 5,300 percent with a BMI of 33–35. The detrimental effects of obesity relative to the development of chronic disease occur when it persists for 10 years or more. This may be a serious health problem in the near future as Peters estimated that given the dramatic rise in overweight children and obesity among children, one in three born in the year 2000 will become diabetic in their lifetime. Moreover, a longitudinal study by Baker and others has shown that the higher the BMI during childhood, the greater the risk of coronary heart disease in adulthood. Cancer Obesity has been regarded as a risk factor for certain cancers for some time, but a large, recent study by Calle and others from the American Cancer Society revealed that obesity plays a much bigger role in causing cancer than previously believed. They estimated that 90,000 Americans die each year by cancer caused primarily by being overweight, accounting for 14 percent of cancer in men and 20 percent in women. Those with the highest BMI (40 or over) were at greatest risk. Additionally, Renehan and others recently reviewed 141 studies with more than 280,000 subjects and reported that over the course of 15 years, men and women who experienced a 5-point increase in their BMI experienced a significant risk of a wide variety of cancers. These findings were recently confirmed by the American Institute of Cancer Research worldwide report on nutrition and cancer, which con-

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cluded there was convincing evidence that increased body fatness was associated with cancer of the breast, colorectum, pancreas, esophagus, and kidney. Obesity may influence the development of cancer in various ways. For example, fat tissue leads to an overproduction of estrogen and other steroid hormones. In women, an increased serum level of estrogen is associated with an increased incidence of breast cancer. Carmichael and Bates reported that most large epidemiological studies have found that overweight or obese women are at increased risk of developing postmenopausal breast cancer, and also indicated that all treatment modalities for breast cancer may be adversely affected by the presence of obesity. Obesity induces insulin resistance, leading to excess production of insulin and insulin-like growth factor receptors which can stimulate proliferation of body cells, a precursor to cancer development. Obesity may also have a local effect, contributing to gastrointestinal reflux in which stomach acids may irritate cells and induce cancer in the lower esophagus. Other unknown factors may also be involved. Maternal Health Women naturally gain weight during pregnancy, but there are some concerns with excess weight gain, particularly the risk of stillbirth. Chu and others, in a recent meta-analysis of nine studies, reported odds ratios (OR) of a stillbirth were 1.47 and 2.07 among overweight and obese pregnant women, respectively, compared with normal-weight pregnant women. They concluded that maternal obesity is associated with an increased risk of stillbirth, although the mechanisms to explain this association are not clear. The Institute of Medicine is considering the possibility of revising current guidelines for weight gain during pregnancy. Mortality, Morbidity, and Quality of Life Obesity shortens life. Even in ancient Greece, Hippocrates recognized that persons who are naturally fat are apt to die sooner than slender individuals. However, a recent analysis by Flegal and others from the Centers for Disease Control (CDC) indicated that body overweight, with a BMI of 25.0–29.9, was not associated with increased mortality, or death. These findings have been supported in an independent meta-analysis of 25 observational studies by McGee, who also reported no increase in morality in individuals classified as overweight. Flegal and others suggested that improvements in medical care, such as better control of blood pressure and serum cholesterol with medications, along with less cigarette smoking, may have decreased deaths from cardiovascular disease in individuals who were classified as overweight. Critics countered that actual deaths from overweight and obesity are only part of the picture. Excess fat contributes to morbidity, or the increase in various diseases such as diabetes and its associated disabilities. Those who are overweight and have such health problems may experience significant impairments in their quality of life. Moreover, critics note that being overweight is the path to obesity, as over time the overweight become obese. Subsequently, a Tufts University report stated that the CDC chief, Julie Gerberding, backed away from the findings of the study, conceding that the results may have been skewed by including people

with chronic diseases, who tend to weigh less but die early. Currently weight control to prevent obesity is one of the top priorities of the CDC. In the same analysis, the CDC indicated that individuals classified as being obese, with a BMI of 30–35, were at a high risk for death, and those with a BMI greater than 35 accounted for the largest majority of deaths. Similar findings were reported in the meta-analysis by McGee. Bren, writing for the Food and Drug Administration, noted that excess weight and physical inactivity account for more than 300,000 premature deaths each year in the United States. Fontaine and others calculated the years of life lost due to obesity and found that those who are obese during young adulthood are at substantial risk for premature death. For example, using data from the National Health and Nutrition Epidemiologic Follow-Up Study, they calculated that white men and women aged 20–30 with severe levels of obesity may lose 13 and 8 years of life, respectively; corresponding years lost for black men and women are 20 and 5, respectively. In general, thinner individuals live longer, particularly if physically fit, as discussed later in this chapter. Epidemiological research clearly indicates that being obese increases one’s health risks. The greater the BMI, particularly above 30, the greater the health risk. The location of the fat in the body is also an important contributing factor underlying these health risks.

How does the location of fat in the body affect health? Classifications of different types of obesity based upon regional fat distribution have been proposed, the most popular differentiation being the android versus the gynoid types. Android-type (male-type) obesity is characterized by accumulation in the abdominal region—particularly the intraabdominal region—of deep, visceral fat, but also of subcutaneous fat. Android-type obesity is also known by other terms, such as abdominal, central, upper body, or lower trunk obesity, and is sometimes referred to as the apple-shape obesity. Although its cause is unknown, researchers have discovered an enzyme in the fat cells of mice that when activated triggers an overproduction of the hormone cortisol, which tends to facilitate the deposition of fat in the abdominal region. Gynoid-type (female-type) obesity is characterized by fat accumulation in the gluteal-femoral region—the hips, buttocks, and thighs. It is also known as lower body obesity, and is often referred to as pear-shape obesity (see figure 10.10). Bouchard has noted that both types of obesity have a strong genetic component. As mentioned earlier, waist measurement may be an appropriate screening technique for android-type or gynoid-type obesity. The procedure for determining waist circumference is described in appendix D and the increase in health risk associated with an increased circumference and various BMI levels is presented in table 10.3 on page 411. Android-type obesity is increasingly being recognized as causing a greater health risk than obesity itself. It appears that android-type fat cells, particularly the deep visceral fat cells, possess dissimilar biochemical functions. These visceral fat cells are www.mhhe.com/williams9

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32" 37"

Lower-body obesity (gynoid - pear shape)

Upper-body obesity (android - apple shape)

F I G U R E 1 0 . 1 0 Android (apple-shape) obesity is associated with a greater risk for chronic diseases, such as diabetes and heart disease, than is gynoid (pear-shape) obesity.

large and highly metabolically active, possibly due to differences in the activity of lipoprotein lipase and higher cortisol levels. PiSunyer indicates that android-type obesity is a cardiovascular health risk factor associated with a state of chronic inflammation and coagulation, which is linked to an increase in the release of adipokines that trigger inflammation and coagulation, and a decrease in adiponectin, a cardioprotective adipokine. Another adipokine, resistin, is theorized to be involved in the development of insulin resistance, one of the characteristics of the metabolic syndrome. Epidemiological data have shown that android-type obesity is associated with a cluster of metabolic disorders, which Dr. Gerald Reaven has labeled the metabolic syndrome; it is also known as the cardiometabolic syndrome and syndrome X. The symptoms of the metabolic syndrome include: • • • • • • • •

hyperinsulinemia insulin resistance impaired glucose tolerance hypertriglyceridemia increased small, dense LDL-cholesterol decreased HDL-cholesterol hypertension increased plasma fibrinogen and clotting

Many of these symptoms are risk factors for CHD and type 2 diabetes, and Lamarche indicated that abdominal obesity predicts CHD and type 2 diabetes better than obesity alone. The metabolic syndrome appears to increase with age, but it may also appear in those with relatively modest BMI levels. Smith recently estimated that 47 million American adults, 25 percent of

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the population, have three or more components of the metabolic syndrome. The percentage is less than 7 percent in those aged 20–29 but increases to more than 40 percent of individuals over age 60. Relative to body weight, you may not need to be obese to develop the metabolic syndrome. Janssen and others recently reported that individuals with a normal BMI (18.5–24.9) and overweight BMI (25.0–29.9) who had a high waist circumference were increasingly likely to have hypertension, diabetes, dyslipidemia, and the metabolic syndrome compared with those with normal waist circumference values. The full metabolic syndrome certainly increases health risks, but Trevisan and others indicated that only a small part of the population possesses the full cluster of symptoms in the metabolic syndrome, and we must not forget the proven health risks of individual risk factors, such as LDL-cholesterol, within the syndrome. Reaven stressed the importance of treating the associated cardiovascular risk factors, such as high blood pressure. The metabolic syndrome has stimulated drug research leading to development of single drugs that simultaneously treat multiple components of the metabolic syndrome, such as high blood pressure and cholesterol levels. In an attempt to provide some standardization, Alberti and others recently convened an international conference to determine a worldwide definition of the metabolic syndrome. Although there are some minor differences among various nations, the presence of the metabolic syndrome in an individual was dependent on waist circumference and having two or more of four metabolic abnormalities. The following apply to North America and Europe:

Waist circumference (inches (cm)) Elevated serum triglycerides (mg/dL) Subnormal HDL-cholesterol (mg/dL) Elevated blood pressure (mmHg) Elevated fasting blood sugar (mg/dL)

Men

Women

37 (94) > 150 < 40 130/85 100

31.5 (80) > 150 < 50 130/85 100

As noted in table 10.3, a waist circumference of 40 inches (102 cm) in men and 35 inches (86 cm) in women has been associated with increased health risks. This new definition lowers the waist circumference to 37 inches (94 cm) for men and 31.5 inches (80 cm) for women. These lower values are in accord with a recent study by Wang and others who reported an increased risk of type 2 diabetes in men with waist sizes greater than 37 inches. Studies show that android-type obesity is a major risk factor for mortality in both men and women. In the Nurses’ Health Study involving nearly 45,000 women, Zhang and others studied the role of abdominal obesity on health over the course of 16 years. They concluded that increased levels of abdominal obesity, particularly waist circumferences of 35 inches or more, significantly increased the risk of all-cause, cardiovascular disease, and cancer mortality independently of body mass index. An elevated waist circumference was associated with significantly increased cardiovascular disease mortality even among normal-weight women. Bigaard and others found that waist circumference, even when accounting for total body fat, remained strongly and directly associated with allcause mortality in middle-aged men and women, suggesting that

C H A P T E R 1 0 Body Weight and Composition for Health and Sport

the increased mortality risk related to excess body fat is mainly due to abdominal adiposity. The increased mortality appears to be due primarily to myocardial infarction. Two recent meta-analyses by Galassi and Gami and their colleagues, one including a metaanalysis of 37 longitudinal studies, revealed similar risk ratios and concluded that individuals with the metabolic syndrome are at increased risk of cardiovascular events. Although abdominal obesity appears to increase health risks, Busetto noted that because of the relatively high rate of visceral fat mobilization, it is a good target for interventions aimed at reducing cardiovascular risk factors. Several recent studies in men, women, and adolescents have shown that weight loss via dieting and exercise will preferentially decrease fat from the abdominal area and, concomitantly, reduce several of the metabolic syndrome risk factors, such as high blood pressure and serum levels of glucose and triglycerides. Gynoid-type fat cells appear to store fat more readily and tend to lose it less readily, and thus the health risks do not appear to be as great as those associated with android-type obesity. A combined diet-exercise program may help to reduce gynoid-type obesity, but the pear-shape figure appears to be more resistant to change compared to the apple type.

Obesity can also cause other health problems in children and adolescents. Huang and others report some studies suggest that the epidemic of obesity is increasing the number of children with the metabolic syndrome and its risk components. For example, Thomas and others studied young adolescents, average age about 13, and reported that body fatness was an independent predictor of triglyceride and blood-pressure levels. Childhood obesity has reached the point at which Daniels reports that diseases once found primarily in adults are now occurring in children, including symptoms of hardening of the arteries, fatty liver disease, and type 2 diabetes. In particular, type 2 diabetes is epidemic among obese youngsters. Although children may not experience the debilitating effects of diabetes early in life, in general children who are overweight and diabetic are likely to stay that way into adulthood. Epidemiological research has shown that obese adolescents are at greater risk for chronic disease in adulthood and all-cause mortality compared to their nonobese peers. Researchers are looking for clues such as genetic, metabolic, or anthropometric markers that can predict which children will become obese so that appropriate interventions may be enacted earlier in life when chances of success to prevent obesity may be greater.

Does being obese increase health risks in youth?

Does losing excess body fat reduce health risks and improve health status?

Childhood obesity is a rapidly emerging epidemic worldwide. Some of the major adverse health effects of excess body fat during childhood and adolescence appear to be social and psychological rather than medical. Because personality development occurs primarily during childhood and adolescence, excessive body fat may contribute more greatly to socialemotional problems at this time than during adult-onset obesity. The Nutrition Committee of the Canadian Pediatric Society noted that obesity interferes with the development of a satisfying selfimage and social status, thereby impairing psychological development. Obese children often are rejected and ridiculed by their peers, superiors, and even parents, resulting in a negative selfimage, low self-esteem, and even serious psychological illness. Warschburger indicates such stigmatization leads to overall poorer psychosocial functioning and an impaired health-related quality of life. A contributing factor to the development of psychological problems may be the adverse effect of excessive body fat on physical fitness and athletic performance. Southern indicates that obese children respond differently emotionally to exercise than do normalweight children, and thus may experience negative consequences to participation in physical activities. A child who is unsuccessful in play activities probably will not participate, and thus will miss the socializing aspects of play. When used in conjunction with appropriate dietary prescriptions and consistent behavior modification, exercise serves as a promising modality that may reverse obese conditions during childhood and, perhaps, prevent the onset of adult obesity.

Numerous studies document the beneficial effects of weight loss by reducing the risk factors for disease, including several major diseases—cardiovascular disease, cancer, and type 2 diabetes. As noted by Mosca, weight control by diet and exercise was one of the key recommendations in the recent American Heart Association report for women to help prevent heart disease. The American Institute of Cancer Research, in its recent worldwide report on nutrition and cancer, placed proper weight control as one of its key recommendations to help prevent a variety of cancers. Additionally, in a recent review of 11 studies, Aucott reported that intentional weight loss reduces the risk of developing diabetes in the long term; individuals with diabetes who lose weight often have reduced clinical symptoms and mortality risk. As noted in chapter 2, the first healthful dietary guideline is to achieve a healthy body weight. As shall be noted in the next chapter, lifestyle changes including adoption of an appropriate diet and exercise program are appropriate for individuals desiring to attain a healthy weight. A variety of diets are available, containing varying percentages of the three macronutrients—carbohydrate, fat, and protein. For weight loss, caloric balance is the key, so weight loss will occur if the total caloric intake, regardless of the macronutrient content of the diet, is less than caloric expenditure. However, as noted in previous chapters, some overall dietary plans, such as the DASH and OmniHeart diets, as well as certain foods, such as fruits, vegetables, and fish, may provide health benefits beyond those associated with weight loss. Chapters 4, 5, and 6 highlight healthful carbohydrates, fats, and protein, while chapter 9 discusses the DASH and OmniHeart diets.

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Does being physically fit negate the adverse health effects associated with being overweight? In general, research findings documenting increased health risks associated with obesity have been derived from the general population, and have been based primarily on BMI values. However, in an article titled Hefty and Healthy, the Consumers Union indicates that the BMI does not do a good job of assessing health, particularly for people who are moderately overweight, and also notes that there is some difference of opinion regarding the role of fitness and fatness in health. As noted previously, the BMI does not evaluate body composition. Although it may be useful in determining health risks in the general population because a high BMI is usually associated with excess body fat, it does not apply to muscular individuals. A high BMI may be associated with the development of various diseases if it does represent obesity and increases various risk factors, such as high serum cholesterol levels and high blood pressure. Glenn Gaesser, an exercise physiologist at the University of Virginia, in his book Big Fat Lies, indicated that being overweight is not necessarily associated with increased health risks. Lifestyle may be an important moderating factor. For example, in the Aerobics Center Longitudinal Study at the Cooper Institute for Aerobics Research, Sui and others conducted a study to determine the association among cardiorespiratory fitness, adiposity, and mortality in older adults (> 60 years). Adiposity was assessed by BMI, waist circumference, and percent body fat. In general, they found that being obese (BMI ≥ 30) or having a large waist circumference (34 inches, women; 40 inches, men) was significantly associated with increased mortality, but not when cardiorespiratory fitness was considered. Some scientists suggest that being overweight does not increase mortality unless it is associated with adverse effects on blood pressure, glucose tolerance, serum cholesterol levels, and physical fitness. Thus, some have proposed use of the term “healthy weight” for overweight individuals who are otherwise healthy. The Health at Any Size movement, as advocated by Jonas, promotes physical activity for the obese individual, suggesting that exercise, even though it may not result in weight loss, may confer health benefits. In support of this contention, Miller and Dunstan found that physical activity intervention for the treatment of type 2 diabetes can lead to small but clinically meaningful improvements in glycemic control, even in the absence of weight loss. Borghouts and Keizer noted that both acute and chronic exercise may affect blood glucose and insulin activity favorably. Up to 2 hours after an acute bout of exercise, glucose uptake in active muscles is in part elevated due to insulin independent mechanisms, probably involving an increase in GLUT-4 receptors in the muscle cell membrane induced by exercise. Additionally, an exercise bout can increase insulin sensitivity for up to 16 hours afterwards. Chronic exercise training potentiates the effect of exercise on insulin sensitivity through multiple adaptations in glucose transport and metabolism. Gerson and Braun reported that when compared with lean fit women, estimated insulin sensitivity was only slightly lower in overweight women with equally high cardiovascular fitness levels. Overall, although exercise training may

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not help some individuals lose weight on the outside, they will improve their health on the inside. Carroll and Dudfield stated that exercise training should be considered an essential part of a therapeutic lifestyle change that may improve the entire cluster of risk factors associated with the metabolic syndrome, but indicated exercise works best when coupled with weight loss. The combination of exercise and weight loss has been shown to produce numerous health effects, including decreased blood pressure, improved serum lipid status, reduced blood glucose, increased self-esteem, improved psychological health, and increased longevity. Stevens and others examined the effects of both fitness (fit, unfit) and fatness (fat, not fat) on mortality from all causes and from cardiovascular disease. They found that fit and not fat individuals had the lowest mortality rates, those who were fit and fat or unfit and not fat had mortality rates about 30–40 percent higher, while fat and unfit individuals had the highest mortality rates. Hu and others recently reported similar findings in a study with women, noting that those who were lean (BMI < 25) and physically active (3.5 or more hours exercise/week) had much lower relative risk of mortality compared to the other groups. Women who were obese and inactive had the highest mortality rate. Weinstein and others, in a prospective study of nearly 39,000 women over the course of nearly 11 years, evaluated the interaction of physical activity and Body Mass Index on the risk of coronary heart disease (CHD). They found that the lowest risk for CHD was found in women who were of normal weight and physically active. Being overweight and physically inactive increased the risk, and women who were obese and inactive had the highest risk. The authors concluded that although the risk of CHD associated with elevated body mass index is considerably reduced by increased physical activity levels, the risk is not completely eliminated, reinforcing the importance of being lean and physically active. These investigators concluded that being fit does not reverse all of the increased health risks associated with excess adiposity. Although being fit and fat appears to be better healthwise than being unfit and fat, losing weight to become fit and unfat may confer some additional health benefits. One should note that a normal BMI does not automatically connote good health. The Consumers Union indicates that individuals with a normal BMI but whose body composition is high in fat, recently referred to as normal-weight obesity, may have increased health risks. One may have a normal BMI but have relatively high amounts of abdominal fat and associated health risk. Prevention of obesity is the key because once individuals become obese, treatment is difficult. When used in conjunction with appropriate dietary prescriptions and consistent behavior modification, exercise serves as a promising modality not only to prevent obesity in the first place, but perhaps also to help reverse it both during childhood and adulthood. www.win.niddk.nih.gov Active at Any Size is a government program to encourage and help overweight individuals plan an exercise program. Access the Weight Control Information Network and click on “Publications for the Public” to access Active at Any Size.

C H A P T E R 1 0 Body Weight and Composition for Health and Sport

Ke y C o n c e p t s 䉴 Excessive body fat is associated with a variety of chronic

diseases and impaired health conditions, including coronary heart disease, diabetes, high blood pressure, and arthritis. 䉴 Although being obese increases health risks, the deposition of fat in the abdominal area exacerbates these risks. Referred to as android-type, or male-type, obesity, increased abdominal fat is associated with the metabolic syndrome and risk factors for heart disease and diabetes. 䉴 For children and adolescents, the major adverse health effects of excessive body fat appear to be social and psychological. However, overweight and obese children are at high risk for type 2 diabetes even when young. Moreover, current research indicates that obese children are more prone to chronic diseases in adulthood than are their nonobese peers. 䉴 Being physically fit and eating a healthful diet may help reduce some of the health risks associated with being overweight. One can be overweight, yet fit, but it appears the greatest health benefits may be associated with being fit and not fat.

C h e c k f o r Yo u r s e l f Conduct an observational study. Learn to use the “eyeball” technique to determine if a child is overweight. One afternoon sit outside a secondary public school in your community and as the students exit, make a check in a notebook as to how many out of the first 50 or 100 you would classify as being overweight. Compare your findings to the text discussion and to the findings of classmates who may also undertake this small observational study.

Excessive Weight Loss and Health Losing excess body fat, even only 5–10 percent of body weight, and attaining a desirable body weight may confer some significant health benefits by counteracting the adverse effects of obesity. However, many individuals attempt to lose weight for other reasons. Slimness is currently very fashionable, particularly among females of all ages. It is desired not only for attractiveness but also for psychological undertones of independence, achievement, and self-control. Also, both male and female athletes, such as distance runners, gymnasts, wrestlers, jockeys, and dancers, practice weight control to improve their performance. Losing body weight for improved performance may also provide some health benefits, for Paul Williams theorized that the elevated HDL-cholesterol concentrations of long-distance runners are primarily a result of reduced adiposity. However, excessive weight loss may actually lead to deterioration of health.

What health problems are associated with improper weight-loss programs and practices? As shall be noted in the next chapter, a well-designed diet and proper exercise are the cornerstones of a sound weight-control program. However, some individuals may establish unrealisti-

cally low body-weight goals, which may lead to pathogenic weight-control behaviors. Such techniques as complete starvation, self-induced vomiting, or the improper or excessive use of drugs, diet pills, laxatives, and diuretics may initially be employed to achieve rapid weight losses but may evolve into serious medical disorders, even death, if prolonged. The following discussion highlights some of the areas of concern in which weight-loss practices may be harmful if abused. Dehydration Dehydration may be induced by exercise, exposure to the heat (as with a sauna), or the use of diuretics and laxatives. The effect of dehydration upon one’s health, particularly in relation to heat illnesses, was detailed in the previous chapter. The use of diuretics and laxatives may increase potassium losses from the body, which may lead to electrolyte imbalances and disturbed neurological function, including heart function. For example, in a case study Sturmi and Rutecki reported life-threatening hyperkalemia associated with ECG changes and indicators of muscle and kidney damage in a bodybuilder who used diuretics and potassium supplements, along with dietary restrictions, in preparation for competition. Vigorous potassium-lowering maneuvers helped resolve these problems, but the patient’s symptoms resembled those of another professional bodybuilder who died after employing similar drug and diet strategies. Disturbed kidney function has also been observed following severe dehydration. Weight-Loss Dietary Supplements Numerous over-thecounter (OTC) and Internet-sales dietary supplements are marketed as weight-loss agents, using marketing ploys such as Lose 30 pounds in 30 days without dieting or exercising! Saper and others note that more than 50 individual dietary supplements and more than 150 combination products are available for weight loss. Many of these products are herbals with no research to support their claims. Others may contain drugs. Meadows indicates that some products made overseas and sold on the Internet may contain prescription drug ingredients; some diet pills contain the active ingredients found in antidepressant or anxiolytic drugs, such as Prozac and Librium, or stimulants comparable to amphetamine. Marketing of weight-loss dietary supplements is one of the biggest concerns of the FDA. In general, OTC weight-loss dietary supplements do not appear to be effective. Three recent reviews concluded that, overall, various herbal products and dietary supplements promoted for weight loss lack sufficient scientific support, and concluded that none of those reviewed could be recommended. Included in the list were the following: chromium chitosan ginseng hydroxycitric acid psyllium St. John’s wort

guar gum conjugated linoleic acid (CLA) green tea carnitine pyruvate

Lenz and Hamilton noted that although pyruvate and CLA have the best supporting evidence, larger and better-controlled trials are needed before these supplements should be recommended for

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weight loss. Pittler and others also indicated that herbal products such as Garcinia cambogia and yerba mate merit further investigation. Saper and others cited evidence of modest weight loss with use of ephedra/caffeine supplements, but marketing of herbal ephedra (ephedrine) products in the United States has been prohibited since 2006. Several of these weight-loss products have been marketed as ergogenic aids, and have been discussed in previous chapters. Caffeine, ephedrine, and ginseng are covered in chapter 13. Rader and others noted recently that the market for botanical dietary supplements in the United States has grown so rapidly that use of new botanical ingredients has often outpaced an adequate scientific understanding of the ingredients themselves. They indicated that this may lead to problems, including misidentification, mislabeling, adulteration, and toxicity. Supplements sold on the Internet may also include prescription drug ingredients, as noted previously, or ephedrine (ephedra). Such weight-loss dietary supplements may contribute to some serious health problems. For example, Pittler and others, in their recent review, found adverse events are reported for a number of herbal food supplements and the reported risks are sufficient to recommend against the use of most of the reviewed supplements. Chitturi and Farrell reported that some herbal slimming aids have been implicated in causing severe and sometimes fatal toxic effects in the liver. As noted above, marketing of ephedra weight-loss products has been banned in the United States. Use of ephedrine-containing weightloss products has been associated with numerous adverse effects, including the deaths of several highly trained athletes. www.cfsan.fda.gov/~dms/ds-savvy.html This Website contains the Food and Drug Administration document: Tips for the Savvy Supplement User: Making Informed Decisions and Evaluating Information.

Weight-Loss Drugs Various drugs have been developed to stimulate weight loss and generally are prescribed for the obese, not for those individuals who want to lose a few pounds. Nevertheless, it appears that individuals across the weight spectrum, including physically active individuals and athletes, are using drugs for weight-control purposes. Some drugs are available without prescription, while others need to be used with medical supervision. Currently, the only two prescription drugs for long-term weight loss available for sale in the United States are sibutramine (Meridia), and orlistat (Xenical). A third drug, rimonabant (Acomplia) is approved in many European countries, but has not yet been approved by the FDA in the United States. Drugs may help reduce body weight by several mechanisms. Some drugs are designed to suppress the appetite by either enhancing or inhibiting the production or activity of various neurotransmitters in the hypothalamus—such as the depressant serotonin, the adrenergic stimulant norepinephrine, or neuropeptide Y (NPY)—involved in appetite control. Increasing serotonin and norepinephrine and decreasing NPY will suppress the appetite. Sibutramine (Meridia) inhibits the reuptake of serotonin and norepinephrine, thus reducing hunger. Other drugs may be used to increase energy expenditure (thermogenesis) in the peripheral tis426

sues, particularly agents designed to increase resting energy expenditure (REE) by stimulating special receptors (Beta-3 receptors) in brown fat and abdominal adipose tissue, and possibly muscle tissue. Sibutramine also stimulates thermogenesis. Other drugs, such as orlistat, may work by blocking gastric and intestinal lipases, thus blocking intestinal absorption of dietary fat and decreasing caloric intake. Recently, orlistat has become an over-the-counter drug called alli , which is half the dose of Xenical. Other weight-loss drugs are available. Rimonabant (Acomplia) helps suppress the appetite, and has been suggested to have independent effects on the metabolic syndrome. Wright and others recently noted that studies with rimonabant show weight losses approximating 14–15 pounds (6.3–6.9 kg) at 1 year. However, as noted, rimonabant has not yet been approved for use in the United States. Tagatose, a monosaccharide similar to fructose, is being studied as a possible drug for weight loss. Lu and others note that currently it is being studied for its role in helping to prevent type 2 diabetes, and studies show promise for inducing weight loss. Nicotine gum or patches have been used to increase the success rate in smoking cessation and may help prevent weight gain. Other than alli , other OTC nonprescription weight-loss drugs are available, such as caffeine. Ephedrine was a popular weight-loss drug, but currently its sale is banned in the United States. Although caffeine and ephedrine, technically, are drugs, they have been marketed as dietary supplements. In a recent review, Chaput and others reported that both sibutramine and orlistat have been shown to be able to induce significant weight loss, with important co-morbidity reduction, allowing the maintenance of reduced body weight for at least 1–2 years. However, there are some possible side effects. Sibutramine use has been associated with various health problems, such as increased blood pressure and heart-rhythm abnormalities. Sibutramine continues to be monitored to determine long-term health concerns. Adverse side effects of orlistat include gastrointestinal problems, such as fatty stools, flatulence, and symptoms of mild diarrhea. However, Anderson reported that alli has been found to be effective for weight loss, and gastrointestinal side effects were minimal when subjects consumed 30 percent of their Calories from fat. Although research shows that many of these drugs may be effective, the lost weight is regained upon cessation of use of the drug if lifestyle is not changed. The Food and Drug Administration (FDA) recommends that weight-control drugs be used only on a short-term basis in conjunction with an education program stressing proper diet, exercise, and behavior modification. A recent one-year study by Wadden and others found that subjects taking Meridia who also exercised and consumed a lowCalorie diet lost 27 pounds, more than twice as much as those who took Meridia without exercising or dieting. Wadden and others also reported that for subjects on a weight-loss diet (1,200 to 1,500 Calories/day), the combination of taking sibutramine along with group counseling led to significantly greater weight loss over the course of one year, almost double the weight loss, as compared to subjects using sibutramine alone or group counseling alone. They concluded that the results underscore the importance of prescribing weight-loss medications in combination with, rather than in lieu of, lifestyle modification.

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Some scientists contend that obesity is an incurable disease, somewhat comparable to type 1 diabetes. Type 1 diabetics need to take insulin daily to control their disease. It is hoped that continued research into the neural mechanisms underlying the etiology of obesity will eventually provide the database for pharmaceutical companies to develop more effective and safe drugs to prevent and treat obesity. For example, a new hormone, obestatin, has been discovered in some animals. Obestatin is derived from the same prohormone as ghrelin, but has the opposite effects; obestatin actually depresses the appetite and thus may serve as the basis for developing an effective and safe weight-loss drug. Very-Low-Calorie Diets Starvation-type diets may involve either complete fasting or very-low-Calorie diets (VLCD) (< 800 Calories/day), often referred to as modified fasts. These diet plans are most often used with inpatient programs in hospitals. The National Task Force on the Prevention and Treatment of Obesity indicated such diets, under proper medical supervision, are generally regarded as safe and have been effective in inducing rapid weight loss in very obese patients. In their meta-analysis, Anderson and others found that successful VLCDs were associated with significantly greater weight-loss maintenance than other successful low-Calorie balanced diets. However, Astrup and Rossner stressed the point that a very-low-Calorie diet should be considered as just the first step of a weight-management program and is successful only when it is followed by a maintenance program consisting of lifestyle interventions involving behavior modification, dietary changes, and increased physical activity. Apparently little or no harm is caused by a 1- or 2-day fast, and some authorities have reported that a healthy man or woman can fast completely for 2 weeks and suffer no permanent ill effect. Although VLCD may be safe and effective for promoting shortterm weight loss, they are not very satisfactory in long-term maintenance of weight loss and fare no better than other dietary approaches. For example, Gilden Tsai and Wadden, in a metaanalysis of six randomized trials, found that VLCDs did induce greater short-term weight losses than typical low-Calorie diets, but there were no significant differences between the two diet plans relative to long-term (1 year) weight loss. Atkinson notes, moreover, that there may be some contraindications to their use and they should be used only after a thorough medical examination. A variety of complications may arise with the use of VLCD, including fatigue, weakness, headaches, nausea, constipation, loss of libido, kidney stones, gallbladder disease, decreased HDL-cholesterol, impaired phagocytic function of the white blood cells, inflammation of the intestines and pancreas, decreases in blood volume, decreases in heart muscle tissue, low blood pressure, cardiac arrhythmias, and even death. Thus, medical supervision is highly recommended for those undertaking VLCD. Weight Cycling Grodner suggested that the chronic dieting syndrome, characterized by intervals of high-Calorie diets and VLCD, may be counterproductive as it may lead to weight cycling (yo-yo syndrome), a vicious cycle involving repeated bouts of weight loss followed by weight gain. Research has revealed that VLCD may lead to a decreased lean body mass, a

decreased thermic effect of food (TEF), a decreased resting energy expenditure (REE), and an enhanced food efficiency (less energy wasted in processing dietary Calories). In essence, your body recognizes that it is being starved and will attempt to conserve body stores of energy by reducing energy output. When you resume normal eating, these energy-conservation mechanisms may continue to function for some time, so you regain the lost weight and possibly more. It is possible that a good proportion of the weight lost during the fasting state is protein, primarily from muscle tissue, which is used to produce glucose for the central nervous system. When you resume eating, the protein tissue is not readily replaced, so the extra Calories may be converted to fat. Moreover, resumption of normal dietary habits may lead to binge eating, episodes in which large amounts of Calories are consumed. Earlier research had suggested that weight cycling would lead to increased amounts of body fat at the same body weight. For example, an individual who started out at 200 pounds with 30 percent body fat would, after several cycles, eventually return to the same weight, but at 35 percent fat. Judith Rodin and her associates at Yale found that weight-cycling women are more prone to deposit fat in the abdominal area, thereby developing an android-type obesity and increased health risks. However, more current research with both animals and humans suggests that weight cycling may not be associated with any adverse effects on body composition or health, as long as the weight regain does not exceed the weight lost. Studies by McCargar and others reported that chronic dieting does not result in a sustained reduction in REE, while Simkin-Silverman and others found no adverse psychological effects in women who had a history of weight cycling. Moreover, a detailed meta-analysis by the National Task Force on the Prevention and Treatment of Obesity revealed that weight cycling does not exert any adverse effect on body composition, metabolism, risk factors for cardiovascular disease, or on the effectiveness of future efforts to lose weight. The Task Force noted that although the evidence currently available indicates weight cycling does not affect morbidity and mortality, conclusive data regarding its long-term health effects are lacking. Currently, the Task Force indicates that obese individuals should not allow any perceived risks of weight cycling to deter them from attempts to lose weight, but the Task Force also notes such individuals should commit to lifelong changes in behavior, diet, and exercise. Some investigators believe the issue of weight cycling and health is still open for debate. Brownell and Rodin have suggested that while there has been no consistent demonstration that, as was first thought, weight cycling makes subsequent weight loss more difficult or regain more rapid, it is possible that this does occur under some conditions or in particular individuals. Although the mechanisms are not clear at present, they also note stronger and more consistent links between body-weight variability and negative health outcomes. In support of this point, Field and others, in the large Nurses’ Health Study, reported that weight cycling was associated with a higher prevalence of binge eating, lower levels of physical activity, and greater weight gain. Given these varying viewpoints there is a clear need for further research on the effects of weight cycling on behavior, metabolism, and health. www.mhhe.com/williams9

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Young Athletes One of the major medical concerns is the effect that severe weight restriction over a longer period may have upon children who are still in the growth and development stages of life. For example, young athletes are at a critical age as far as nutritional needs are concerned, yet the importance of making weight for certain sports often outweighs consideration of a balanced diet, adequate fluid intake, and a minimum caloric requirement. Hence they may go for months without adequate intake of essential nutrients like protein, iron, zinc, and calcium. Although numerous studies have revealed nutrient deficiencies and pathogenic weight-control behaviors in young athletes such as wrestlers and ballet dancers, unfortunately we have very few data on the long-range effects of such practices. Benardot and Czerwinski, comparing the height:age and weight:age percentiles for female gymnasts between the ages of 7 and 10 versus 11 and 14, suggested that the decreased percentiles in the older gymnasts could be attributed to nutritional deficits, sport-specific selection factors favoring retention of small muscular gymnasts, or a combination of the two. In a recent prospective study, Theintz and others studied the growth rate of adolescent female gymnasts and swimmers over a 2- to 3-year period and observed that the growth velocity of the gymnasts was lower than the swimmers. They theorized growth rate was impaired by heavy training (> 18 hours/week), possibly combined with the metabolic effects of dieting, leading to inhibition of the hypothalamus and pituitary gland with resultant suppression of proper sexual development. In their review, Daly and others concluded that adolescent athletes may be at risk of delayed maturation and restricted growth when intense training is combined with insufficient energy intake, but catch-up growth commonly occurs when training is reduced or ceases, so final adult stature is unlikely to be compromised. The American College of Sports Medicine also concluded that participation in high school wrestling, which normally involves weight cycling, does not adversely affect normal growth patterns. However, Daly and others indicated that in athletes who have long-term, clinically delayed maturation, catch-up growth may be incomplete, and recently reported a high frequency of reduced growth velocity in some, but not all, female gymnasts. Within the past 30 years there has been increasing concern over the development of chronic dieting problems, that is, eating disorders in children, adolescents, and young adults that could have serious adverse health consequences.

What are the major eating disorders? Disordered eating reflects atypical eating behaviors. Budd indicates that approximately 5 percent of American women suffer from clinical eating disorders (discussed later), but many more exhibit signs of disordered eating. Disordered eating may involve such behaviors as restrictive dieting, using diet pills or laxatives, bingeing, and purging, which Budd suggests develop when young females, particularly those who lack close relationships with others, adopt them as a means of self-control. The Office on Women’s Health (OWH) notes that disordered eating can involve changes in eating patterns that occur in relation to a stressful event, an illness, 428

personal appearance, or in preparation for athletic competition. In general, disordered eating behaviors occur less frequently or are less severe than those required to meet the full criteria for the diagnosis of an eating disorder. They fit into a category the American Psychiatric Association (APA) classified as Eating Disorders Not Otherwise Specified (EDNOS). For example, Keel and others have identified a condition called purging disorder, which is similar to bulimia but does not involve binge eating, only purging usually by self-induced vomiting. The OWH indicates that while disordered eating can lead to weight loss or weight gain and to certain nutritional problems, it rarely requires in-depth professional attention. On the other hand, disordered eating may develop into an eating disorder. The American Psychiatric Association (APA) defines eating disorders as illnesses in which the victims suffer severe disturbances in their eating behaviors and related thoughts and emotions. Currently, the American Psychiatric Association, in their Diagnostic and Statistical Manual of Mental Disorders, recognizes three clinical eating disorders: • anorexia nervosa (AN) • bulimia nervosa (BN) • binge eating disorder (BED) The American Dietetic Association, in their position stand on treatment of eating disorders, reported that more than 5 million Americans suffer from eating disorders, including 5 percent of females and 1 percent of males. Anorexia nervosa (AN) is a complex disorder that is not completely understood but is thought to be a sign of other psychological problems. Research has suggested that anorexics possess characteristics that underlie compulsive personality disorders, and the prevalence of anorexia nervosa is greatest in groups that abuse psychoactive substances. Genes linked to AN have been identified, possibly some involved in appetite control. The diagnostic criteria for anorexia nervosa, as developed by the American Psychiatric Association, are summarized below: 1. Refusal to maintain the body weight over a minimal normal weight for age and height. A weight loss leading to maintenance of body weight less than 85 percent of that expected, including the expected weight gain during the period of growth. 2. An intense fear of gaining weight or becoming fat, even though underweight. 3. A disturbance in the way one’s body weight or shape is perceived. 4. Amenorrhea, or the absence of at least three consecutive menstrual cycles in normally menstruating females. Individuals with anorexia nervosa may be the binge-eating/ purging type, engaging in binge eating or purging behavior, such as self-induced vomiting or the misuse of laxatives, diuretics, and enemas. The restricting type does not engage in such behaviors. The prevalence of anorexia nervosa is relatively low, about 1 percent or less in the general population, but reported to be as high as 2 percent in college students. Anorexia nervosa is generally found in adolescent women, and about 85–95 percent of those affected are young females, usually under the age of 25. Multiple factors underlie the development of anorexia nervosa, but it prevails more in societies that savor the thin physique and consider dieting normal behavior.

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There appears to be a strong genetic predisposition to AN. Bulik and others found that AN was more prevalent between identical twins as compared to fraternal twins, and they indicated that about 56 percent of causality of anorexia is associated with genetics. Sodersen and others suggest brain mechanisms for reward may be critical; they may be stimulated when food intake is reduced, thus sustaining disordered eating behaviors. Environmental factors also contribute to AN. It appears that the person with the highest probability of developing anorexia nervosa is a perfectionistic and self-critical individual who comes from an upper-middle socioeconomic status, possibly being raised in an overprotective home environment. Susceptible individuals desire to have control over something in their lives. Individuals with AN are more likely to be depressed, anxious, and suffer obsessive-compulsive disorders. Chronic low self-esteem, which may be associated with a poor body image, has been identified as a strong risk factor. Although most anorexics are female, male anorexics possess similar characteristics. Medical consequences of AN can be very serious, including hormonal imbalances, anemia, decreased heart muscle mass, heart beat arrhythmias attributed to electrolyte imbalances, and even death. Treatment involves an interdisciplinary team consisting of professionals from medical, nursing, nutritional, and mental health disciplines, and is generally prolonged for several years and primarily involves psychological therapy. Steinhausen, in a review of 119 studies, found that the outcome for individuals with AN improved little over the last half of the twentieth century. In general, Mayer and others found that women with a lower percent body fat experienced a poorer long-term outcome. Berkman and others noted that mortality is high; in particular, individuals with AN are at high risk for suicide. The term bulimia nervosa means morbid hunger, and the disorder involves a loss of control over the impulse to binge. The bulimic individual repeatedly ingests large quantities of food within a discrete period of time, such as 2 hours, but follows this by self-induced vomiting and other measures to avoid weight gain; this is the binge-purge syndrome. Bulimics may use other techniques, such as fasting or excessive exercise, to compensate for the binge. The American Psychiatric Association criteria for bulimia nervosa include the following: 1. Recurrent episodes of binge eating, at least two per week for 3 months. 2. Lack of control over eating during the binge. 3. Regular use of self-induced vomiting, laxatives, diuretics, fasting, or excessive exercise to control body weight. 4. Persistent concern with body weight and body shape. Bulimia nervosa is more common than anorexia nervosa, the prevalence in the general population being about 2–3 percent. However, the prevalence among college students may be much higher. Haller indicated up to 10 percent of college students may be bulimic. As with anorexia nervosa, certain characteristics may underlie the development of bulimia nervosa, including the desire for thinness and chronic low self-esteem. Although McGilley and Pryor noted that serious medical complications of bulimia nervosa are not common, reported adverse health effects of bulimia nervosa include erosion of tooth enamel,

tears in the esophagus, aspiration pneumonia, electrolyte imbalances, and heart failure, all of which may be vomiting-induced. As with anorexics, bulimics are in need of psychological counseling by qualified medical professionals. Prozac (fluoxetine), an antidepressant drug that helps increase serotonin levels, has been approved for medically supervised use in treating bulimia nervosa. Shapiro and others report that Prozac helps decrease the core symptoms of BN and associated psychological factors, at least on a short-term basis; behavioral treatment may also be effective. According to the OWH, people with binge eating disorder (BED) often eat an unusually large amount of food and feel out of control during the binge, which may include the following behaviors: 1. 2. 3. 4. 5.

Eat more quickly than usual during binge episodes Eat until they are uncomfortably full Eat when they are not hungry Eat alone because of embarrassment Feel disgusted, depressed, or guilty after eating

These behaviors are also common to BN, but the individual with BED does not purge. The causes of BED are similar to BN. Health consequences include weight gain and obesity, along with increases in CHD risk factors, cancer, and other health problems previously discussed. Treatment of BED is comparable to BD, which may involve medication such as antidepressants; treatment for obesity may also be involved. The prevalence of full-blown clinical eating disorders in the general population is only about 1–3 percent. However, as noted previously, many more individuals exhibit signs of disordered eating. Research suggests that disordered eating may be more prevalent in certain professions or personal pursuits, one in particular being sports. www.womenshealth.gov This is the U.S. Department of Health and Human Services Website for women’s health.Type eating disorders, or the specific eating disorder, in the Search box to access detailed information on causes, symptoms, health risks, prevention, and treatment.

What eating problems are associated with sports? Depending on the nature of the sport, the loss of excess body weight may enable an athlete to compete in a lower weight class or improve appearance and/or biomechanics and enhance the potential for success. Thus, some athletes may use weight loss as an ergogenic aid. Examples of such sports include wrestling, gymnastics, ballet, cheerleading, bodybuilding, figure skating, diving, lightweight football, lightweight rowing, and distance running. To lose weight, athletes in these sports, particularly athletes with perfectionistic tendencies, may exhibit some, but not all, of the characteristics associated with clinical eating disorders, thus meeting the criteria for Eating Disorders Not Otherwise Specified (EDNOS). The American Psychiatric Association uses EDNOS for individuals who do not meet the criteria for anorexia nervosa or bulimia nervosa. Included in this category is anorexia athletica. In www.mhhe.com/williams9

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recent years the term anorexia athletica has been applied to those athletes who become overly concerned with their weight and exhibit some of the diagnostic criteria associated with AN or BN According to Jorunn Sundgot-Borgen, an international authority on eating disorders in athletes, individuals must meet five criteria for anorexia athletica: 1. 2. 3. 4. 5.

Excessive fear of becoming obese Restriction of caloric intake Weight loss No medical disorder to explain leanness Gastrointestinal complaints In addition, they must meet one or more of these related criteria:

1. 2. 3. 4. 5. 6.

Disturbance in body image Compulsive exercising Binge eating Use of purging methods Delayed puberty Menstrual dysfunction

Although male athletes, particularly those in bodybuilding, distance running, and wrestling, may be at risk for disordered eating, Beals and Manore note that it is difficult to obtain a good estimate of the number of male athletes with eating disorders as most studies have focused on female athletes. Although Putukian indicated that females in all sports are subject to disordered eating, Smolak and others, in a meta-analysis of 34 studies, found that elite athletes in sports emphasizing thinness are particularly at risk. This finding is supported by several recent studies by Torstveit and Sundgot-Borgen, but they also noted that a significant proportion of nonathletes were at risk for behaviors associated with the Female Athlete Triad. In a study conducted by the National Collegiate Athletic Association (NCAA), Dick indicated that at least one documented case of an eating disorder in athletes was reported in 70 percent of the member institutions surveyed. Studies have revealed that approximately 20–40 percent of female athletes may exhibit such criteria, and rates from 50–74 percent have been reported for certain sports, such as gymnastics, distance running, and competitive bodybuilding, sports that emphasize leanness or a specific body weight. In general, in their review, Currie and Morse reported that eating behaviors improve when the athletic season is completed and the athlete resumes normal dietary habits. For example, O’Conner and others reported that symptoms of eating disorders in female college gymnasts abated after their retirement from the sport. However, what begins as a means to control weight for athletic competition on a short-term basis may develop into a longterm medical problem. Anderson proposed the notion that the development of an eating disorder is analogous to the process whereby an individual gets into a canoe some distance above Niagara Falls. When paddling downstream, the person is in control, but there reaches a point where the current of the falls takes over and the individual loses control. Indeed, in a recent NCAA study with Division I athletes, Johnson and others reported that 13 percent reported clinical signs of eating disorders, about 10 percent with bulimia and 3 percent with anorexia nervosa. 430

Female Athlete Triad Under the leadership of Christine and Leslie Bonci and their associates, the National Athletic Trainers’ Association recently developed an excellent position statement on disordered eating in athletes. The position statement provides 50 recommendations for detecting, preventing, and managing disordered eating in athletes, including predisposing risk factors, clinical features and behavioral warning signs, screening methods, therapeutic interventions, special considerations for adolescent athletes, and prevention strategies. Athletic trainers and others involved in the health care of athletes should be aware of these recommendations. The Female Athlete Triad—disordered eating, amenorrhea, and osteoporosis—was introduced in chapter 8 with a focus on calcium balance. The Triad may have serious health consequences, particularly premature osteoporosis, one of the reasons the American College of Sports Medicine recently revised its position stand on the Female Athlete Triad. Beals and Meyer also noted that alone or in combination, the disorders of the Triad can impair athletic performance. The following discussion highlights the key points of the ACSM position stand along with other research findings. www.acsm-msse.org To view the American College of Sports Medicine position stand on the Female Athlete Triad, click on Position Stands and then the PDF for the Female Athlete Triad.

Disordered eating Two Triad experts, Anne Loucks and Melinda Manore, contend that several characteristics of eating disorders, either decreased energy intake and poor food selection or excessive exercise energy expenditure that is not balanced by energy intake, may be contributing factors to the Triad. In this regard, the ACSM stresses that the key factor in the Triad is low energy availability. Inadequate caloric intake may be inadvertent, intentional, or psychopathological. Whatever the reason, the ACSM notes that most adverse effects of the Triad appear to occur when energy intake availability is below 30 Calories per kilogram of fat-free mass per day, which may lead to impaired reproductive and skeletal health. Manore notes, however, that there appears to be wide individual variability in the response of athletes to factors that may influence low energy availability. Amenorrhea Amenorrhea is the absence of a menstrual period. Primary amenorrhea represents a delay in the onset of puberty and the menarche (first menstrual period) whereas secondary amenorrhea represents an interruption of the normal menstrual cycle, with an interval of 3–6 months or more between periods. Both types of amenorrhea may occur in athletes due to low energy availability, which may be associated with a number of factors, such as exercise intensity and training practices, bodyweight and composition, disordered eating behaviors, and physical and emotional stress. Collectively, the interaction of low energy availability and these other factors may influence the hypothalamus. The hypothalamus helps regulate the secretion of releasing-hormones from the pituitary gland, which stimulate the ovaries to secrete the female sex hormones, estrogen and progesterone. Interruption of the normal hypothalamus-pituitary-ovary

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axis may interfere with the reproductive cycle and contribute to cessation of menstruation. The ACSM indicates that amenorrhea may be related to infertility and other health problems. Although eating disorders and low energy availability may also occur in males, Loucks indicates the consensus is that reproductive dysfunction is uncommon in male athletes and that the long-term physiological consequences of the suppression of the hypothalamic-pituitary-testicular axis in male athletes probably have little clinical significance. Osteoporosis Premature osteoporosis is one of the most serious consequences of the Female Athlete Triad. One of the major consequences in disruption of the normal hypothalamic-pituitaryovary axis may be decreased amounts of estrogen from the ovaries. In addition, hormones released by the adrenal glands may be converted by fat tissue into one form of estrogen; with lower levels of body fat, less estrogen may be produced. As noted in chapter 8, estrogen helps regulate bone metabolism and increase bone mass. Additionally, dietary restrictions will reduce the intake of nutrients important for bone health, such as calcium and protein. Thus, disordered eating predisposes the athlete to osteoporosis. The ACSM notes that bone mineral density decreases as the number of menstrual cycles missed increases. Stress fractures occur more commonly in females with low bone mineral density, and the relative risk for stress fractures is two to four times greater in amenorrheic than eumenorrheic athletes. Moreover, the loss of bone mineral density in young athletes may not be reversible. Prevention Prevention of eating disorders in young athletes should receive more attention. Several investigators have suggested that special attention should be devoted to young female athletes, particularly those involved in such sports as gymnastics and ballet, because they may meet the age, gender, and socioeconomic status criteria that may predispose to anorexia nervosa. The ACSM indicates that for prevention and early intervention, education of athletes, parents, coaches, trainers, judges, and administrators is a priority. Athletes should be assessed for the Triad at the pre-participation physical and/or annual health screening exam, and whenever an athlete presents with any of the Triad’s clinical conditions. Coaches and others should look for the following: • • • • • •

Unexplained weight losses Frequent weight fluctuations Sudden increases in training volume Obsession with exercise Excessive concern with body weight Appearance, and evidence of bizarre eating practices

The NCAA may provide brochures and other materials to help develop awareness among athletes of the potential health risks associated with these disorders. A summary of some possible warning signs developed by the NCAA is presented in table 10.4. The ACSM further notes that sport administrators should also consider rule changes to discourage unhealthy weight loss practices, similar to what has been done with males in the sport of wrestling at both the high school and college level.

TABLE 10.4 National Collegiate Athletic Association

warning signs for anorexia nervosa and bulimia nervosa Warning Signs for Anorexia Nervosa Dramatic loss in weight A preoccupation with food, Calories, and weight Wearing baggy or layered clothing Relentless, excessive exercise Mood swings Avoiding food-related social activities Warning Signs for Bulimia Nervosa A noticeable weight loss or gain Excessive concern about weight Bathroom visits after meals Depressive moods Strict dieting followed by eating binges Increasing criticism of one’s body National Collegiate Athletic Association. Reprinted by permission.

In this regard, coaches and others should be aware of the limitations associated with body composition measurement. Unfortunately, imprecise measurement of body composition may be a predisposing factor to the development of eating disorders in athletes. As noted previously, prediction of body fat may vary considerably, so an athlete who may predict to be 10 percent by one method or prediction equation may predict to be 15–20 percent by others. If, for some reason, a coach believed that an athlete should achieve a set body-fat percentage (e.g., 8 percent), it would be wise to use a variety of techniques to predict body-fat percentages and use the lowest value predicted. This might be the safest approach to help prevent an excessive target loss of body fat that might lead to disordered eating. For young girls, Diane Elliot and Linn Goldberg at Oregon Health & Science University developed a program called ATHENA, or Athletes Targeting Healthy Exercise & Nutrition Alternatives, designed to reduce risky dietary practices and promote a healthy body weight. http://www.ohsu.edu/hpsm/athena.cfm Access this Website for the school-based program ATHENA, or Athletes Targeting Healthy Exercise & Nutrition Alternatives, to promote a healthy body weight in physically active girls.The program includes eight sessions and is peer led and coach facilitated.

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Treatment The ACSM indicates that the first aim of treatment for any Triad component is to increase energy availability by increasing energy intake and/or reducing exercise energy expenditure. A multidisciplinary treatment team should include a physician or other healthcare professional and a registered dietitian. Nutrition counseling and monitoring may be sufficient for many athletes. Simply decreasing the amount of weekly exercise by about 10 percent or gaining several pounds may help. Dietary changes should include additional Calories and increased amounts of dietary protein. However, the ACSM notes that for athletes with eating disorders, a mental health practitioner may be needed as the treatment may warrant psychotherapy. Local dietitians and psychologists are excellent contacts if assistance is needed in dealing with eating disorders. Many hospitals have eating disorder programs that also may be able to provide assistance.

Ke y C o n c e p t s 䉴 Sibutramine (Meridia) and orlistat (Xenical) are the only

prescription weight-loss drugs approved for use in the United States. 䉴 Drugs and very-low-Calorie diets may be very effective for weight loss under medical supervision, but they may be associated with a variety of health risks if not used properly. In general, weight-loss dietary supplements do not appear to be effective and their use may be associated with adverse health effects. 䉴 Excessive weight losses, usually associated with behaviors characteristic of eating disorders, may result in health problems ranging from mild to severe and may also have a negative impact upon physical performance. 䉴 Disordered eating in female athletes, usually excessive dieting and exercise to control body weight, may lead to amenorrhea, impair reproductive health, and lead to the development of premature osteoporosis.

C h e c k f o r Yo u r s e l f Go to a local health food store and ask the clerk for weight-loss products. Check those available and determine the active ingredient in each. How many contain various herbals or caffeine? Alternatively, ask only for those with herbals or herbals with caffeine (guarana), and inquire about the safety of each. Compare your findings to the text discussion.

Body Composition and Physical Performance Modifying body weight and composition is considered by some to be an ergogenic aid. Over the years athletes have used a variety of techniques, including surgery such as liposuction and body sculpting and drugs such as anabolic steroids and human growth hormone (discussed in chapter 13), but most have used diet and specific exercise programs. Healthy diet and exercise programs to 432

lose excess body fat or gain muscle mass are presented in chapters 11 and 12, respectively, but let us look at some examples as to how body weight change may affect sport performance.

What effect does excess body weight have on physical performance? In some sports, extra body weight might prove to be an advantage, especially in football, ice hockey, sumo wrestling, and other sports in which body contact may occur or in which maintaining body stability is important. The effect of the extra weight may be neutralized, however, if the individual loses a corresponding amount of speed. Hence, increases in body weight for sports competition should maximize muscle mass and minimize body-fat gains. In rare instances, such as long-distance swimming in cold water, extra body fat may be helpful for its insulation and buoyancy effects. On the other hand, there are a variety of sports where excess body weight may be disadvantageous. Whenever the body has to be moved rapidly or efficiently, excess weight in the form of body fat serves only as a burden. Take a good look at high jumpers, long jumpers, ballet dancers, gymnasts, sprinters, and long-distance runners. The amount of musculature may vary in each, but the body-fat percentage is extremely low. Research has also shown that even some professional football players have relatively low percentages of body fat. According to basic principles of physics, body fat in excess of the amount necessary for optimal functioning will impair physical performance. Body fat increases the mass, or inertia, of the individual but does not contribute directly to energy production, so excess fat will detract from performance in events in which the body must be moved. For example, a high jumper can develop only so much power through muscular force when taking off. Basic laws of physics tell us that an extra 5 pounds of body fat would decrease the height to which the body center of gravity could be raised, thus decreasing the height that could probably be cleared. Extra poundage on a distance runner could add a considerable energy cost. Adding body fat would slow the running pace. In essence, the body becomes a less efficient machine when it must transport extra weight that has no useful purpose. That extra weight is usually excess body fat. Losing excess fat will not influence the total VO2 max, but will increase VO2 max when expressed in milliliters of oxygen per kilogram body weight. For example, Amby Burfoot, editor-at-large for Runner’s World magazine, wrote a science-based article on the ideal weight for runners. Based on changes in VO2 max expressed in milliliters/kilogram body weight, he calculated that for every pound you lose, you will save about 2 seconds per mile run. For example, if you lose 5 pounds, you will save about 31 seconds in a 5-kilometer (3.1 mile) race, and over 4 minutes in a marathon; if you lose 20 pounds of excess fat, corresponding savings would be 2:04 and 17:28 in the 5K and marathon, respectively. These beneficial effects are most relevant for those runners who have excess body fat to lose, and may not be applicable to runners at their optimal body weight. Losing too much weight may adversely affect running performance. For a number of reasons it is difficult to predict with certainty a precise percentage of body fat for a given athlete that will result in optimal performance. Nevertheless, studies with elite athletes

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have given us some general guidelines. Male sprinters, long-distance runners, wrestlers, gymnasts, basketball players, soccer players, swimmers, bodybuilders, and football backs have functioned effectively with 5–10 percent body fat. Other male athletes such as baseball players, football linemen, tennis players, weight lifters, and weight men in track and field may average 11–15 percent, or just below the average for the nonathletic individual. Several authorities have suggested that female athletes should carry no more than 20 percent fat while others note it should be below 15 percent. Female gymnasts and distance runners have been recorded well below 15 percent; some gymnasts were even below 10 percent. Most other female athletes range between 15 and 20 percent, with some of the strength-type athletes, such as discus throwers, recording values of 25 percent or greater. Although these are some general guidelines, it should be noted that body-fat percentage is only one of many factors that may influence physical performance, and athletes may perform very well even though their body fat is above these levels. However, everything else being equal, excess body fat is a disadvantage when energy efficiency of body movement in sport is an important consideration. Care should be taken in advising athletes to lose body weight to achieve an arbitrary predetermined goal, that is, 5 percent body fat. First, recall that the measurement techniques for body composition have a 2–4 percent error rate or higher for estimating body fat. Second, the nature of the athlete’s body composition may make it impossible to achieve that low level. And third, as suggested by Benardot and Thompson, excessive weight losses may actually lead to a decrease in physical performance, just the opposite of the desired goal.

Does excessive weight loss impair physical performance? In 1998 the National Collegiate Athletic Association adopted a rule mandating testing to establish a minimum wrestling weight for each wrestler. Oppliger and others recently reported that the NCAA weight management program appears effective in reducing unhealthy weight cutting behaviors, such as rapid weight losses and gains associated with competition, and promoting competitive equity. However, some studies found that a significant percent of the high school, college, and international-style wrestlers still used potentially harmful weight-loss methods. Weight-reduction programs used by wrestlers and other athletes have been condemned by sports medicine groups, not only for health reasons but also because these practices may impair physical performance. In its position stand on weight loss in wrestlers, the American College of Sports Medicine noted that the practice of “weight cutting” involving food restriction, fluid deprivation, and dehydration could not only affect physical health and growth and development, but also impair competitive performance. This impairment in performance may be attributed to decreased blood volume, decreased testosterone levels, impaired cardiovascular function, decreased ability to regulate body temperature, hypoglycemia, or depletion of muscle and liver glycogen stores. However, the ultimate effect upon performance may be dependent upon the technique used—dehydration or starvation— and the time over which the weight is lost.

The effect of rapid weight loss by voluntary dehydration upon physical performance was covered in chapter 9. In general, events characterized by power, strength, and speed may not be adversely affected by short-term dehydration, whereas performance in aerobic and anaerobic endurance events is likely to deteriorate, particularly if exercising under warm environmental conditions. Starvation and semistarvation studies have been conducted over periods ranging from 1 day to 1 year. Short-term starvation, involving rapid weight loss, may impair physical performance if blood glucose and muscle glycogen levels are lowered substantially. Although strength and VO2 max generally are not affected by acute starvation, recent studies using a 24-hour fast have shown that anaerobic and aerobic endurance performance will suffer if dependent upon muscle glycogen or normal blood glucose levels. Longterm semistarvation may lead to significant losses of lean muscle tissue and decreased performance in almost all fitness components. For example, Roemmich and Sinning compared body composition and strength measures of adolescent wrestlers with controls over the course of a wrestling season, and found that the wrestlers decreased body weight, body fat, and various measures of strength and power from pre-season to late-season. The wrestlers failed to gain lean tissue during this time frame, which the authors associated with the decrease in strength and power. However, body weight, strength, and power returned to normal during the postseason. Also, wrestlers who weight cycle during the competitive season do not experience sustained decreases in resting energy expenditure, according to a study by Schmidt and others who followed wrestlers over two seasons. It was interesting to note that in some semistarvation studies in which fewer than 1,000 Calories were consumed daily, vigorous exercise programs were maintained even though the subjects were losing substantial amounts of body weight. In general, the authors noted that the key point was to prevent hypoglycemia, dehydration, and excessive loss of lean muscle mass. If these goals could be achieved, physical performance need not deteriorate on weight-loss programs. Nevertheless, Horswill and others found that performance on a high-intensity arm exercise task decreased significantly after subjects lost 6 percent of their body weight by either a hypocaloric low-carbohydrate diet or a hypocaloric high-carbohydrate diet. However, the impairment was less with the high-carbohydrate diet, suggesting that athletes undergoing weight loss for competition should increase the carbohydrate proportion of the hypocaloric diet. Walberg-Rankin and others also reported that although weight loss by Calorie restriction significantly reduced anaerobic performance in wrestlers, those on a high-carbohydrate refeeding diet tended to recover their performance while those on a moderate carbohydrate diet did not. Maffulli, in a case study of two elite Sumo wrestlers, noted that an 8 percent loss of body weight over a 22-day period had no effect on aerobic power (VO2 max) and maximal isometric strength, but prolonged anaerobic exercise performance was impaired. Other recent studies have shown impairment in physical performance with rapid weight-loss techniques. Gutierrez and others studied the effect of 3-day fast on young men during training, and found that fasting decreased both body fat and muscle mass, had no effect on hand-grip strength or perception-reaction time, but significantly decreased physical working capacity based on heart rate www.mhhe.com/williams9

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responses to a cycling exercise protocol. Hall and Lane reported an impaired performance, as evaluated by four 2-minute circuit exercise sessions, in experienced amateur boxers who reduced their body weight to their championship weight over one week. The boxers also experienced increased anger, fatigue, and tension, and reduced vigor. Filaire and others also reported significant impairment in strength and 30-second jumping performance in judo athletes who lost weight rapidly via food restriction over 7 days. Conversely, Fogelholm and others found that body-weight losses approximating 5 percent of body weight, either done rapidly in about 2 days or gradually over 3 weeks, did not impair anaerobic performance in experienced wrestlers and judo athletes. It is difficult to predict the specific body weight at which physical performance will begin to deteriorate for a given individual. For those athletes who are on a weight-loss program, it may be wise to monitor performance through certain standardized tests appropriate for their sport. Some examples include basic fitness tests with measures of strength, local muscular endurance, and cardiovascular endurance. A decrease in performance may be indicative that the weight loss is excessive. Personality changes, excessive tiredness, weakness, and lack of enthusiasm may also be telltale clues. In his review, Fogelholm indicated that although various forms of physical performance were adversely affected by rapid weight loss, a gradual weight loss was less likely to impair performance.

A P P L I C AT I O N Have your body-fat percentage measured with as wide a variety of techniques as possible, such as skinfolds, bioelectrical impedance analysis, air displacement plethysmography, and others. Compare the differences and relate to the text discussion. If access to a variety of techniques is not available, have four or five individuals measure your skinfolds and calculate your body fat according to the directions in appendix D. Compare the differences and compare to the text discussion.

In support of this viewpoint, Zachwieja and others reported that 2 weeks of moderate dietary energy restriction (750 Calories less per day) induced a weight loss of about 3 pounds in physically fit young men and women, but had no effect on muscle strength and endurance, anaerobic capacity as evaluated by the Wingate test, or aerobic endurance as measured by a 5-mile run. Weight losses have the potential to either improve or diminish performance. The key is to lose weight properly, primarily body fat. The basic guidelines for the development of such a weight–control program to improve physical performance, or health, are presented in the next chapter.

Ke y C o n c e p t s 䉴 Although the average body-fat percentages for young men and

women are, respectively, 15–20 percent and 23–30 percent, those involved in certain types of athletic competition may be advised to reduce those levels. 䉴 Excessive loss of body weight may impair sport performance. For athletes in sports where weight loss may enhance performance, basic specific fitness tests may be used periodically to ascertain that performance is maintained or improved.

E X E R C I S E Body-Fat Percentage Measurements Skinfold analysis

Bioelectrical impedance

Air displacement plethysmography

Other

Other

Body-fat percentage Skinfold Measurements Measurement Measurement Measurement Measurement Measurement 1 2 3 4 5 Skinfold measurement

Review Questions—Multiple Choice 1. Which of the following best describes the role of leptin in the human body? (a) It is secreted by the hypothalamus and stimulates lipolysis in adipose cells. (b) It is secreted by the liver and inhibits the digestion of fats.

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(c) It is secreted by the adipose cells and inhibits hunger. (d) It is secreted by the stomach and stimulates appetite. (e) It is secreted by the intestines and stimulates appetite.

C H A P T E R 1 0 Body Weight and Composition for Health and Sport

2. Which of the following statements regarding android/gynoid obesity is false? (a) Gynoid obesity is associated with a higher incidence of certain diseases, such as hypertension.

(b) Android obesity is characterized by excess accumulation of fat deposits in the abdominal area. (c) Android obesity is seen more often in men, while gynoid obesity is more prevalent in women. (d) Gynoid-type fat deposits are more resistant to weight loss compared to android obesity. (e) Development of both types of obesity is influenced by heredity. 3. If a skinfold technique for body composition has a standard error of estimate of 3 percent, you can have 70 percent confidence that for a person who has a predicted body fat of 18%, the actual value is within a range of (a) 6–18 percent (b) 18–21 percent (c) 12–24 percent (d) 15–21 percent (e) 18–30 percent 4. Which of the following ranges of the Body Mass Indexes (BMI) is indicative of a normal height to weight relationship? (a) 5–8 (b) 10–12 (c) 15–17 (d) 20–22 (e) 27–28

5. In which sports might the condition of “anorexia athletica” appear to be more prevalent? (a) football and basketball (b) swimming and baseball (c) wrestling and field hockey (d) ballet and gymnastics (e) tennis and golf 6. The set-point theory of weight control is based upon a feedback system, suggesting that the individual is programmed to be a certain body weight and that the body will always attempt to maintain that weight by regulating hunger and metabolism. What part of the body is believed to be the regulatory center for the control of the various feedback mechanisms? (a) liver receptors (b) stomach receptors (c) blood receptors in the kidney (d) receptors in the hypothalamus in the brain (e) receptors in the small intestine where absorption takes place 7. The disorder of bulimia, which is often characterized by the binge-purge syndrome, is found (a) only in those with anorexia nervosa (b) only in extremely underweight individuals

(c) only in normal weight individuals (d) only in moderately or morbidly obese individuals (e) in individuals across the bodyweight spectrum 8. Which of the following is mainly an environmental rather than a possible hereditarial factor in the multicausal etiology of obesity? (a) a sedentary lifestyle (b) hormonal imbalance (c) disorder in the brain’s hunger and satiety centers (d) lower basal metabolic rate (e) a higher “set point” 9. Obesity has been associated as a potential risk factor in all the following diseases or health problems except which one? (a) coronary heart disease (b) anemia (c) hyperlidemia (d) diabetes (e) hypertension 10. Protein consumed during a starvationtype diet most likely will be: (a) used to rebuild muscle tissue (b) used to replace worn-out cells (c) converted to glucose for energy (d) used to stabilize fluid balance (e) stored as fat Answers to multiple choice questions: 1. c; 2. a; 3. d; 4. d; 5. d; 6. d; 7. e; 8. a; 9. b; 10. c.

Review Questions—Essay 1. List and describe five different techniques used to evaluate body composition, and highlight at least one value of each. 2. Discuss the set-point theory of bodyweight control and relate it to body-fat levels, leptin, and neuropeptide Y.

3. List the various genetic and environmental factors that may be involved in the etiology of obesity. Highlight two of each and explain their possible role. 4. Explain the metabolic syndrome and associated health risks.

5. List the three components of the Female Athlete Triad. Discuss the underlying theories regarding its etiology, the potential effects on hormonal status, and subsequent serious health problems.

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Weight Maintenance and Loss through Proper Nutrition and Exercise

K E Y

aerobic walking 482 behavior modification 449 duration concept 474 exercise frequency 475 exercise intensity 474 interval training 482 long-haul concept 471 maximal heart rate reserve (HR max reserve) 478 rating of perceived exertion (RPE) 480 spot reducing 486 stimulus period 477 target heart rate range/target HR 479 threshold stimulus 478

CHAPTER L E A R N I N G

O B J E C T I V E S

After studying this chapter, you should be able to:

T E R M S

ELEVEN

warm-down 476 warm-up 476

1. Determine how many Calories per day are needed to maintain one’s current body weight with either a sedentary or physically active lifestyle. 2. Calculate the amount of weight loss needed to attain a healthier BMI or body-fat percentage. 3. Identify behavior modification techniques that are appropriate to incorporate into a recommended weight-loss program. 4. Determine the number of daily Calories needed to lose body fat by diet alone, or with a combination diet-exercise program. 5. State the key principles underlying a weight-control diet designed to maintain a healthy body weight for a lifetime. 6. Use the Food Exchange System to plan a healthy, balanced diet containing sufficient Calories to meet one’s daily energy needs for weight loss or weight maintenance. 7. Describe the value of exercise, including type, intensity, duration, and frequency, in a comprehensive weight-loss or weight-maintenance program. 8. Use heart rate responses as a guide to appropriate aerobic exercise intensity. 9. Design a progressive exercise program that will increase caloric expenditure to 300–500 Calories per day as part of a comprehensive weight-loss or weightmaintenance program. 10. Understand how diet and exercise complement each other to help lose or maintain body weight, citing the benefits of each that help compensate for the possible deficiencies of the other.

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Introduction Given the obsession we have with slimness and the fact that millions of Americans and Canadians are overweight, it is no wonder that a multibillion-dollar weight-control industry has developed. Weightloss centers and health and fitness spas cater to this obsession and promise us new bodies just in time for the swimsuit season. Pharmaceutical companies produce drugs, both prescription and over-thecounter types, to help us lose fat the easy way. Food manufacturers market convenient, low-Calorie, prepackaged—but expensive—meals. Newspaper and magazine advertisements claim you can “Lose weight while you sleep” or “Lose 30 pounds in just 30 days.” Each year at least one diet book on the best-seller list is advertised as the last diet we will ever need. A variety of techniques, some useful and some not, are used in attempts to stimulate weight loss. Drugs are used to depress the appetite or increase metabolism. Creams are applied to specific body parts to shrink local fat deposits. Surgical techniques include intestinal bypasses, removal of or stapling part of the stomach, excision or suction removal of subcutaneous fat tissue, and wiring the jaw shut. Weight-loss diets involve almost every possible manipulation, including the high-fat diet, the highprotein diet, the chocolate diet, the grapefruit diet, the starvation diet, and even the “no diet” diet. Advertisements claim specially designed clothing worn during exercise can help you lose inches of fat in hours. Psychological techniques such as hypnosis or behavior modification are designed to change your eating habits. The Committee to Develop Criteria for Evaluating the Outcomes of Approaches to Prevent and Treat Obesity identified three types of programs and approaches to treat obesity or overweight: clinical programs, nonclinical programs, and do-it-yourself programs. No matter which program an individual selects to lose weight, the committee recommended consultation with one’s primary healthcare provider before engaging in a weight-loss program. In severe cases of clinical obesity, treatment usually is administered in a clinical program under medical super-

vision and may involve a combination of many techniques, including surgery, hormone therapy, drugs, and starvationtype diets. An individualized, medically supervised weight-control program is very important for the clinically obese because so many health risks are related to obesity. Surgery may be effective. In two recent studies, Adams and Sjöström reported that gastric bypass surgery in severely obese individuals decreased long-term mortality by 40 percent as compared with that in the control group, mainly attributed to lower death rates from coronary heart disease, diabetes, and cancer. Unfortunately, however, clinical obesity is very resistant to other forms of treatment, particularly dieting, and over 95 percent of those individuals who lose weight regain it within 1–5 years and may do this repeatedly. As noted in chapter 10, these fluctuations in body weight, known as weight cycling, may not exert deleterious effects on metabolism and health and should not deter obese individuals from attempts to lose weight. The National Institute of Health notes that other groups may need medically supervised weight-loss programs, including children, pregnant women, persons over the age of 65, and individuals with medical conditions that could be exacerbated by weight loss. Nonclinical programs for the treatment of obesity are primarily commercial franchises, using packaged

materials provided by counselors who usually are not professional healthcare providers; an example is Weight Watchers. Do-it-yourself programs include any effort by the individual to lose weight by himself or herself or through communitybased and work-site programs. These treatment programs may be well suited for individuals who have accumulated excess body fat through environmental conditions, such as excessive eating and decreased physical activity. Such programs may be beneficial to the typical adult, for substantial amounts of body fat appear to accumulate between the ages of 25 and 35. The prevalence of overweight individuals, as measured by the Body Mass Index (BMI), in the United States has increased in the past quarter-century in both children and adults, and this weight gain has been associated with an increased incidence of health complications. However, Jones and others recently noted that weight losses as small as 5–10 percent of initial weight can improve health, such as reducing the risk of type 2 diabetes. Because the majority of obese people who lose weight put it back on, most weight-control experts indicate the focus should be on prevention and maintenance. Prevention of excess weight gain is more effective than treatment. Prevention should be a lifelong lifestyle, beginning in childhood and continuing through adulthood. Preventive techniques may be espe-

cially helpful during the first 2 years of college, when young females typically gain weight. As noted in a study of twins by Newman and others, prevention may also curtail the weight gain in those genetically predisposed. Many overweight individuals often note that the hard part is not losing weight, it’s keeping it off, but that may not necessarily be so. Maintenance of a healthy body weight is a simple form of prevention; preventing weight regain is comparable to preventing weight gain in the first place. This chapter centers on some basic questions relative to the construction, implementation, and maintenance of a sound weight-control program using the do-it-yourself approach. The principles and suggestions advanced here apply to the overweight individual who wants to lose excess body fat and also to the person with normal body weight who may want to maintain that weight level or even lose additional poundage in order

to improve physical performance. Individuals who are already lean should consult with qualified health professionals before attempting to lose weight. As Fontana and Klein note, it is possible that even moderate caloric restriction may be harmful in some individuals, such as lean persons who have minimal amounts of body fat. One potential problem is the development of an eating disorder, as discussed in the last chapter. For individuals interested in participating in nonclinical or clinical programs, some guidelines are offered later in this chapter. A comprehensive weight-control program involves three components: (1) a dietary regimen stressing balanced nutrition but with reduced caloric intake; (2) an aerobic and resistance exercise program to increase caloric expenditure and maintain lean body mass; and (3) a behavior modification program to facilitate the implementation of the first two

Ke y C o n c e p t 䉴 A comprehensive weight-control program involves a balanced

reduced-Calorie diet, aerobic and resistance exercise program, and appropriate behavior modification.

Basics of Weight Control How many Calories are in a pound of body fat? One pound is equivalent to 454 grams. Because we know that 1 gram of fat is equal to 9 Calories, it would appear that a pound of body fat would equal about 4,086 Calories (9 × 454). However, the fat stored in adipose tissue contains small amounts of protein, minerals, and water, which reduces the caloric content of 1 pound of body fat to approximately 3,500 Calories.

Is the caloric concept of weight control valid? The caloric concept of weight control is relatively simple. As illustrated in figure 11.1, if you take in more Calories than you expend, you will gain weight, a positive energy balance. If you expend more than you take in, you lose weight, a negative energy balance. To maintain your body weight, caloric input and output must be equal. As far as we know, human energy systems are governed by the same laws of physics that rule all energy transformations. The First Law of Thermodynamics is as pertinent to us in the conserva-

components. These components are emphasized in this chapter. Although proper dieting and exercise are the two keys to weight control, the same diet and exercise plan may not be appropriate for all individuals. In a discussion of genotypespecific weight-loss treatment, Adamo and Tesson indicate that like obesity itself, weight loss is a complex phenomenon dependent on many environmental and genetic influences, and thus individual responses to weightloss interventions are incredibly variable. Nevertheless, however one does it, creating a negative energy balance in the body will lead to weight loss. As we shall see, a wide variety of diet and exercise programs may satisfy the criteria for a healthy weight-loss program and most individuals can find a program to meet their individual needs.

tion and expenditure of our energy sources as it is to any other machine. Because a Calorie is a unit of energy, and because energy can neither be created nor destroyed, those Calories that we eat must either be expended in some way or conserved in the body. No substantial evidence is available to disprove the caloric theory. It is still the physical basis for body-weight control. Keep in mind, however, that the total body weight is made up of different components, those notable in weight-control programs being body water, protein in the fat-free mass, small amounts of carbohydrate, and fat stores. Changes in these components may bring about daily body-weight fluctuations of 3–5 pounds that would appear to be contrary to the caloric concept since protein and carbohydrate contain only 4 Calories per gram and water contains no Calories. You may gain water weight by consuming a high-salt diet for a day, or by menstrual cycle changes. You may lose 5 pounds in an hour, but it will be mostly water weight lost through sweating. Starvation techniques may lead to rapid weight losses, but some of the weight loss will be in glycogen stores, body-protein stores such as muscle mass, and the water associated with glycogen and protein stores. In programs to lose body weight, we usually desire to lose excess body fat, and certain dietary and exercise techniques may help to maximize fat losses while minimizing protein losses. The metabolism of human energy sources is complex, and although the caloric theory is valid relative to body-weight control, one must be aware that weight changes will not always be exactly in line with caloric input and output, and that weight losses may not be due to body fat loss alone. Also keep in mind www.mhhe.com/williams9

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140

0 150 16

Weight loss

Negative energy balance

140

0 150 16

Positive energy balance

Weight maintenance

140

0 150 16

Weight gain

F I G U R E 1 1 . 1 Weight control is based upon energy balance. Too much food input or too little exercise output can result in a positive energy balance or weight gain. Decreased food intake or increased physical activity can result in a negative caloric balance or weight loss.

one of the concepts advanced in the last chapter relative to individual variability in metabolic rates; two individuals with the same body weight may consume the same amount of Calories, yet one may gain while the other may maintain or even lose weight. Other than differences in metabolism, this possibility also may be related to the type of Calories in the diet; research has suggested that the body may store dietary fat Calories in the adipose tissue more efficiently than carbohydrate or protein Calories. In essence, compared to dietary fat, it may take more energy to convert dietary carbohydrate and protein into body fat. These concepts are explored further in this chapter.

How many Calories do I need per day to maintain my body weight? This depends on a number of factors, notably age, body weight, sex, resting energy expenditure (REE), the thermic effect of feeding (TEF), and physical activity levels. The caloric requirement per kilogram of body weight is very high during the early years of life when a child is developing and adding large amounts of body tissue. The Calorie/kilogram requirement decreases throughout the years from birth to old age, with exceptions during pregnancy and lactation. Body weight influences the total amount of daily Calories you need, but not the Calorie/kilogram level. The large individual simply needs more total Calories to maintain body weight. Body weight is the most significant factor determining daily caloric intake necessary to maintain weight, although body composition also may be important. Up to the age of 11 or 12, the caloric needs of boys and girls are similar in terms of Calories/kilogram body weight. After puberty, however, males need slightly more Calories/kilogram, probably because of their greater percentage of muscle tissue in comparison to females. Individual variations in REE may either increase or decrease daily caloric needs, depending on whether the REE is above or below normal. Individual variations may vary 10–20 percent from normal. An extended discussion of the REE was presented in chapter 3. 444

The TEF effect may also vary among individuals. The TEF is also covered in more detail in chapter 3. Physical activity levels above resting may have a very significant impact upon caloric needs. Some activities, like bowling, may increase energy needs only slightly, while others, such as running for an hour or more, may add 1,000–1,500 or more Calories to the daily energy requirement. You may wish to review chapter 3 regarding the caloric cost of exercise. All of these factors make it difficult to make an exact recommendation relative to daily caloric needs. As noted in chapter 3, the doubly labeled water (DLW) technique may provide a fairly accurate measure of total daily energy expenditure (TDEE). However, it is rather expensive and not readily available to most individuals. Several other methods are available to help you determine the amount of Calories you need to consume daily in order to maintain a stable body weight. Some are more detailed than others, but keep in mind that all are estimates that may contain some degree of error. Estimated Energy Requirement (EER) Technique In chapter 3 we introduced the concept of Estimated Energy Requirement (EER) as presented by the National Academy of Sciences (NAS) in their recent document focusing on DRI for energy. The EER is defined as the dietary energy intake that is predicted to maintain energy balance in a healthy individual of a defined age, gender, weight, height, and level of physical activity consistent with good health. As you may recall, your total daily energy expenditure (TDEE) includes your resting energy expenditure (REE), the thermic effect of food (TEF), and the thermic effect of exercise (TEE). The EER formulae for gender and different age categories are presented in table 11.1. As noted, the formulae require age, height, weight, and physical activity quotient (PA). You can easily determine the first three criteria, which is all you need to obtain an estimate of your energy requirements if you are sedentary, but determination of your PA requires some effort. To calculate your EER, you should first determine your energy needs for a sedentary lifestyle. Select the appropriate formula for your gender and age category from table 11.1 and use the value of 1.0 as the PA. For example, a 20-year-old sedentary male weigh-

C H A P T E R 1 1 Weight Maintenance and Loss through Proper Nutrition and Exercise

TABLE 11.1 Estimated Energy Requirement (EER)

formulae Females age 19 and over: EER = 354 – 6.91 × Age + [PA × (9.361 × Weight + 726 × Height)] Males age 19 and over: EER = 662 – 9.53 × Age + [PA × (15.91 × Weight + 539.6 × Height)] Females age 9–18: EER = 135.3 – 30.8 × Age + [PA × (10.0 × Weight + 934 × Height)] + 25 (Calories/day for energy deposition) Males age 9–18: EER = 88.5 – 61.9 × Age + [PA × (26.7 × Weight + 903 × Height] + 25 (Calories/day for energy deposition) Age: In years. Weight: In kilograms (kg). To convert weight in pounds to kilograms, multiply by 0.454. Height: In meters (m). To convert height in inches to meters, multiply by 0.0254. Adapted from National Academy of Sciences. 2002. Dietary Reference Intakes for Energy, Carbohydrates, Fiber, Fat, Protein and Amino Acids (Macronutrients). Washington, DC. National Academy Press.

ing 175 pounds (80 kilograms) who is 71 inches (1.8 meters) tall would have a daily EER of 2,715 Calories. EER = 662 – 9.53 × 20 + [1.0 × (15.91 × 80 + 539.6 × 1.8)] = 2,715

mates of exercise caloric expenditure are not exact because different calculations are used. However, both provide reasonable values for the energy cost of daily physical activity. The NAS bases the PAL on the amount of daily physical activity that is the equivalent of walking at a rate of 3–4 miles per hour. To reach a specific PAL category, you are required to expend the energy equivalent of walking a set number of miles. Although the NAS bases the PAL on an energy equivalent of walking, keep in mind that you do not need to walk the required miles to attain a specific PAL category. You may do a multitude of physical activities, such as golfing, swimming, and jogging, that add up to this energy equivalent. For your body weight, use appendix B to find the Calories you expend each minute for walking at a given pace, such as 3 to 4 miles per hour. Then locate other activities that expend similar amounts of Calories per minute. Engaging in such activities for 15–20 minutes is the equivalent of walking a mile. Here is a brief summary of the amount of physical activity needed for each PAL category. Table 11.2 complements this discussion. Some guidelines based on the energy expenditure equivalents of walking (3–4 mph) or jogging are presented. Sedentary category The energy expenditure of individuals in the Sedentary category represents their REE, including the TEF, plus various physical activities associated with independent living, such as walking from the house or work to the car, walking your dog, typing, daily household tasks, and other forms of very light activity. If you engage in no daily physical activity, your PAL will range from 1.00 –1.39, but your PA for the formula is set at a baseline of 1.0. Individuals who walk less than 30 minutes daily generally fall in this category. Low Active category In addition to the normal daily activities of independent living, you need to expend the physical activity equivalent of walking about 2.2 miles per day in order to be in the Low Active category. Your PAL for the Low Active category will range from 1.40–1.59, but the PA for the formula is set at 1.11–1.16 depending on gender and stage of life. Individuals who walk 30–40 minutes, or jog 10–15 minutes, daily generally fit this category.

As you may recall from chapter 3, the PA is based on your physical activity level (PAL), which is the ratio of your TDEE to your BEE, or TDEE:BEE, over a 24-hour period. The NAS indicates that physical activity is the most variable component of TDEE, and also notes that the assessment of physical activityinduced increments in TDEE is fraught with considerable uncertainties. Nevertheless, they have developed four categories of PAL: Sedentary, Low Active, Active, and Very Active. TABLE 11.2 The physical activity level categories www.nap.edu If you would like to calculate your PAL and resultant PA based on the NAS protocol, type in Dietary Reference Intakes for Energy, and then peruse chapters 5 and 12 for details of the procedure.

However, we will use a modified approach to estimate your EER based on your daily record of physical activities and associated caloric expenditure as calculated from appendix B. The correlation between the NAS procedure and our esti-

PAL category

Physical activity level (PAL)

Physical activity coefficient (PA) Males

Females

Boys

Girls

Sedentary

≥ 1.0 –< 1.4

1.00

1.00

1.00

1.00

Low Active

≥ 1.4 –< 1.6

1.11

1.12

1.13

1.16

Active

≥ 1.6 –< 1.9

1.25

1.27

1.26

1.31

Very Active

≥ 1.9 –< 2.5

1.48

1.45

1.42

1.56

Adapted from National Academy of Sciences. 2002. Dietary Reference Intakes for Energy, Carbohydrates, Fiber, Fat, Protein and Amino Acids (Macronutrients). Washington, DC. National Academy Press.

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Active category In addition to the normal daily activities of independent living, you need to expend the physical activity equivalent of walking about 7 miles per day in order to be in the Active category. Your PAL for the Active category will range from 1.60–1.89, but the PA for the formula is set at 1.25–1.31 depending on gender and stage of life. Individuals who walk 1.75 hours, or jog 40–45 minutes, daily generally fall in this category. Very Active category In addition to the normal daily activities of independent living, you need to expend the physical activity equivalent of walking about 17 miles per day in order to be in the Very Active category. Your PAL for the Very Active category will range from 1.90–2.50, but the PA for the formula is set at 1.42–1.56 depending on gender and stage of life. Individuals who walk 4.25 hours, or jog 1.5 hours, daily generally fit this category. Let us continue with the example of our 20-year-old male and determine the number of Calories he would need to expend to move from the Sedentary category (2,715 Calories) into each of the active categories. If we consult table 11.2 we see that the PAs for the Low Active, Active, and Very Active categories are, respectively, 1.11, 1.25, and 1.48. Low Active: EER = 662 – 9.53 × 20 + [1.11 × (15.91 × 80 + 539.6 × 1.8)] = 2,962 Calories Active: EER = 662 – 9.53 × 20 + [1.25 × (15.91 × 80 + 539.6 × 1.8)] = 3,276 Calories Very Active: EER = 662 – 9.53 × 20 + [1.48 × (15.91 × 80 + 539.6 × 1.8)] = 3,793 Calories As his EER for the Sedentary category is 2,715 Calories, he would need to expend about 247, 561, or 1,078 Calories through physical activity to attain, respectively, the Low Active, Active, and Very Active PAL categories. We will talk more about exercise later in this chapter. In chapter 3 we introduced you to appendix B and explained how you might calculate your daily energy expenditure through physical activity. You may wish to review that discussion on page 103. In brief, record the number of minutes of each type of physical activity you do daily. Then, consult appendix B, find your body weight in the top margin, and determine how many Calories you expend per minute doing each activity. Let’s apply this procedure and complete the example of our 20-year-old male. Let us assume that he has engaged in the following physical activities over the course of a week, has calculated his energy expenditure from appendix B, totaled his weekly energy expenditure, and then figured his daily average caloric expenditure.

446

Duration

Calories/ min

Tennis, singles Walking, 3 mph

40 min 20 min

8.8 4.8

352 96

Tuesday

Running, 7 mph

40 min

14.9

596

Wednesday

Tennis, singles Walking, 3 mph

40 min 20 min

8.8 4.8

352 96

Thursday

Running, 8 mph

30 min

17.1

513

Friday

Tennis, singles Bowling

40 min 30 min

8.8 4.9

352 147

Saturday

Golf, carry clubs

180 min

4.8

864

Sunday

Running, 7 mph

40 min

14.9

596

Day

Physical activity

Monday

Total weekly Calories Daily average caloric expenditure (3,700 Calories 7days)

Total calories

3,964 566

Thus, with an average daily energy expenditure through physical activity totaling 566 Calories, he is in the Active PAL category and can use that formula to calculate his EER. Alternatively, he may simply add the 566 Calories to his Sedentary EER to determine the number of Calories needed to maintain his body weight if it has been stable. Using the formula for the Active category, his EER as noted would total 3,276 Calories. Adding the 566 Calories to his Sedentary category EER of 2,715 would total 3,281 Calories. The difference between the two estimates is negligible in this case, but may vary some in other cases. Using this same procedure, you may calculate your EER to maintain your normal body weight. Use the formula in table 11.1 that is appropriate for your gender and age and, using the appropriate PA values from table 11.2, calculate your EER for each of the four PAL categories. Next, as per the previous example, record the type and amount of time devoted to various physical activities over the course of a week and calculate your average daily physical activity energy expenditure; you may then either add this amount to your Sedentary EER or use the appropriate formula to estimate your total daily EER. Estimated Energy Requirement (EER) MyPyramid Technique You may more easily calculate your EER by using the program available in the MyPyramidTracker Website. When you join, you enter your age, height, and weight, which are used as part of the basis to calculate your EER and can be updated as needed. When you access MyTracker, click on “Assess Your Physical Activity” to calculate your EER. There are two options available. In brief, the condensed option is recommended for people with few leisure-time activities or for people who are not regularly physically active. Based on the age, gender, weight, and height information in your personal profile, an estimated Basal Energy Expenditure (BEE) is calculated and adjusted to include routine activities (i.e., personal

C H A P T E R 1 1 Weight Maintenance and Loss through Proper Nutrition and Exercise

hygiene, housework, light yard work, computer use, and driving a car) of estimated duration. You may also enter in some leisure-time activities. However, the Website notes that with or without additional leisure-time physical activity, the assessment of EER using the condensed physical activity entry option may not be accurate. The standard option provides the most accurate assessment of your EER. You must enter all activities you performed in the past 24 hours, including sleeping, eating, sitting while reading or watching television, personal hygiene, housework, transportation, employment, leisure, and exercise. The total duration of these activities should add up to 1,440 minutes (24 hours). www.MyPyramid.gov The MyTracker program on MyPyramid provides a means to calculate your Estimated Energy Requirement (EER). The standard option is the most accurate. Helpful hints are presented in the text. Once enrolled in the program, you may access the site directly at www.MyPyramidTracker.gov.

With the standard option, your level of physical activities over the course of a typical week will provide a good estimate of your EER. You can enter each day of the week separately. If so, you may save your “Frequently Performed Activities” to ease data entry. You may also enter the data once, calculating an average amount of time for each activity beforehand. For example, if you jog 45 minutes four days per week, this totals 180 minutes per week, or an average 26 minutes daily. Calculate a daily average for other activities as well. Once you input the data, click on Energy Balance. Disregard the food input message, and you will be provided with your EER. Calorie Counting Technique If your body weight has been stable, keeping track of the Calories you eat for 3–7 days may provide you with a good estimate of your daily energy requirement. Eat your normal diet, but record everything you consume. Some guidelines for measuring, recording, and calculating your daily caloric intake are presented on pages 458–461. Computerized dietary analysis programs are available to facilitate this task. For example, the MyTracker program also has a dietary analysis program to assess your daily caloric intake. Simplified Technique The National Institutes of Health, in its MedlinePlus Website, has provided some guidelines for the approximate daily caloric intake needed to maintain current body weight. The guidelines are presented in table 11.3. For example, if you are moderately active and weigh 170 pounds, you will need about 2,550 Calories (170 × 15) to maintain a desirable body weight. Keep in mind that no matter which procedure you follow, your actual daily caloric needs may vary somewhat from the estimate obtained. In the section of

TABLE 11.3

this chapter on dietary modifications, we will discuss how many Calories you may need in your diet if you desire to lose weight. If that is the case, you may wish to estimate your daily energy needs by several techniques and use the lowest value obtained in order to optimize the caloric deficit needed for weight loss, as long as it meets the recommendations presented for safe weight loss.

How much weight can I lose safely per week? If you decide to lose weight without medical supervision, keep in mind that the recommended maximal weight loss is 2 pounds per week. Because there are 3,500 Calories in a pound of body fat, this would necessitate a deficit of 7,000 Calories for the week, or 1,000 Calories per day. For growing children who carry excess fat, the general recommendation is about 1 pound per week, or a daily 500-Calorie deficit. Keep in mind that these are maximal recommended weight-loss values for medically unsupervised programs. Lower weight-loss goals, such as 1 pound per week for adults and one-half pound per week for children and adolescents, may be more appropriate, realizable goals. These recommendations are in line with guidelines presented by health professionals, such as the American College of Sports Medicine. As we shall see later in this chapter, weight losses may not parallel the caloric deficit we incur during early stages of a weightreduction program, and the 2-pound limit may be adjusted during this time period. In addition, as mentioned previously, we want our weight loss to be body-fat tissue, not lean body mass. A loss of 10 pounds of body weight may help improve physical performance, but if 5 pounds is muscle tissue, then performance could possibly deteriorate. Thus, you should monitor your weight loss not only with a scale but also with skinfolds and girth measures, or other body composition procedures, to help ensure that you are losing body fat, and in the right places.

How can I determine the amount of body weight I need to lose? As noted in the last chapter, individuals desire to lose weight for one of three reasons—to improve appearance, health, or physical performance. As for your appearance, you are the judge, but consult

Approximate daily caloric intake needed to maintain desirable body weight

Activity level

Calories per pound

Calories per kilogram

1. Sedentary or very obese

10

22

2. Low activity level, or over age 55

13

28.5

3. Regular moderate activity

15

33

4. Regular strenuous activity

18

39.5

• Low activity: No planned, regular physical activity; occasional weekend or weekly activity (such as golf or recreational tennis) is the only type of physical activity • Moderate activity: Participating in physical activities such as swimming, jogging, or fast walking for 30–60 minutes at a time • Strenuous activity: Participating in vigorous physical activity for 60 minutes or more at least 4–5 days per week

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with your physician or other health professional. You do not want your weight-loss program to induce an eating disorder. Losing excess body fat for health is a good reason. Check with your physician, who can also monitor health risks, such as blood pressure, serum lipids, blood glucose, and regional adiposity, associated with excess body weight. A loss of 5–10 percent body weight or 2–4 inches off the waist, easily achieved in 3–4 months, may help reduce several health risk factors. Losing weight in attempts to enhance physical performance should involve interactions between the athlete, coach, and team physician, and in the case of young athletes parents should be involved. Janet WalbergRankin noted that body-weight goals for athletes should be based on current body composition, time remaining until the competitive season, body-weight history, and sport-specific rules. In their review, Brownell and Rodin indicated that weight-loss goals should account for how much weight an individual can reasonably lose and should not be determined solely by health standards. The same reasoning applies for appearance and physical performance standards. They note that pursuit of an unrealistic ideal may lead to various health problems. Several procedures may be used to estimate desired weight loss. Using the Body Mass Index (BMI) as a guide, you will need to calculate your current BMI and determine your target BMI. Calculation of the BMI was presented on page 404 and a healthy BMI range is approximately 18.5–25. The formula to calculate your desired body weight in kilograms is Target body weight (kg) = Target BMI × height in meters2 As an example, if you are 5′7″ (1.70 meters) tall and weigh 170 pounds (77.2 kilograms), then you have a BMI of 26.7 (77.2/1.702). If you want to achieve a healthier BMI of 23, simply multiply 23 by 1.702 to determine your body-weight goal; 23 by 2.89 equals 66.5 kilograms, or 146 pounds. The desired weight loss would be 24 pounds (170 – 146), which represents a 14 percent reduction in total body weight (24/170 = 0.14; 0.14 × 100% = 14%). If you want to use body-fat percentage as the guide to weight loss, you will need to measure your current body-fat percentage and determine your target goal. Methods of determining body-fat percentage are presented on pages 574–578 in appendix D. If you are an athlete with 20 percent body fat but desire to get down to 15 percent, you may use the following formula: Target body weight =

Lean body mass in pounds 1.00 – desired body-fat percentage

As an example, an athlete who weighs 150 pounds and is 20 percent body fat has 30 pounds of body fat, and the remaining 120 pounds (150 – 30) is lean body mass. Substituting in the formula provides the following data: 120 120 = = 141 pounds 1.00 – 0.15 0.85 Thus, this athlete would need to lose 9 pounds of body fat (150 – 141) to achieve a 15 percent body-fat percentage. If proper methods of weight loss are used as discussed later in this chapter, the losses will be in body fat, not lean body mass. 448

Ke y C o n c e p t s 䉴 One pound of body fat contains about 3,500 Calories. 䉴 The caloric deficit, which represents caloric intake minus caloric

expenditure, may be useful as a means to predict body-weight losses on a long-term basis, because 3,500 Calories equals approximately 1 pound of body fat. 䉴 Various procedures are available to estimate daily energy requirements. Although all are estimates, calculating the Estimated Energy Requirement from 24-hour records of activity will provide the best estimate. 䉴 For the overweight adult who desires to lose weight without the guidance of a health professional, the recommended maximal weight loss is 2 pounds per week. Losing 1 pound a week is a more reasonable goal. Weight loss in children and adolescents should be about half the recommendations for adults.

C h e c k f o r Yo u r s e l f Based on your age, gender, height, and weight, calculate your Estimated Energy Expenditure (EER) for a sedentary lifestyle based on the formula in table 11.1. Use a PA value of 1.0. Compare this value to your REE determined in chapter 3. Using the guidelines presented in the text, you may also wish to calculate your EER based on your daily physical activity level. The MyTracker program on the MyPyramid Website facilitates the calculation. If you want to lose weight, use the text information to determine an appropriate total weight loss and recommended weight loss per week.

Behavior Modification What is behavior modification? One of the key components of a successful weight-control program is the need to identify and modify those behaviors that contribute to the weight problem. The subject of human behavior development and change is very complex, but psychologists note that three factors are generally involved—the physical environment, the social environment, and the personal environment. For the person with a weight problem, a refrigerator brimming with food (physical environment), a family that consumes high-Calorie snack foods around the house (social environment), and an acquired taste for high-fat or sweet foods (personal environment) may trigger behaviors that make it very difficult to maintain a proper body weight. A model often used to explain the development or modification of health behaviors, such as a proper diet and exercise program for weight control, involves three steps—knowledge, values, and behavior. First, proper knowledge is essential. A considerable amount of misinformation relative to the roles of nutrition and exercise in weight control exists, so you need to possess accurate information. Second, the health implications of this knowledge may help you develop a set of personal values, or attitudes, toward a specific health behavior. If you perceive excess body fat as a threat to your personal

C H A P T E R 1 1 Weight Maintenance and Loss through Proper Nutrition and Exercise

physical or psychological health, you are more likely to initiate behavioral changes. Third, your health behavior should then reflect the knowledge you acquired and the values you developed. Behavior modification is a technique often used in psychological therapy to elicit desirable behavioral changes. The rationale underlying behavior modification is that many behavioral patterns are learned via stimulus-response conditioning; for example, a stimulus in your environment such as a commercial break in a television program elicits a response of a mad dash to the refrigerator. Because such responses are learned, they also may be unlearned. For a discussion of a comprehensive program conducted by a behavioral psychologist, the reader is referred to the review by Brownell and Kramer. Relative to a self-designed program of weight control, behavior modification is used primarily to reduce or eliminate physical or social stimuli that may lead to excessive caloric intake or decreased physical activity. George Bray, an international authority on obesity treatment, noted that the most important component of any weightcontrol program is the associated behavior modification through which the individual learns new ways to deal with old problems. In a recent study stressing the importance of behavior modification, Haus and others recommended that potential weight-program participants should learn and practice the weight-maintenance behavior of reduced dietary fat and regular exercise, independent of and before any weight-reduction attempts. The Consumers Union notes that exercising more and switching to a leaner, healthier diet will yield innumerable health benefits even if you don’t lose a single pound.

How do I apply behavior-modification techniques in my weight-control program? When breaking any well-established habit, self-discipline, or will power, is the key. The most important component of a weightcontrol program is you. You must want to lose weight, and you must take the major responsibility for achieving your goals. You need to face the fact that being overweight and sedentary is dangerous to your health. You must be convinced that reduced body weight will enhance your life, and you must establish this goal as a high priority. You must be able to tolerate some discomfort as you make lifestyle changes. Data from the National Weight Control Registry, which consists of people who have lost at least 30 pounds and kept it off, indicate the key factor is to do it for yourself. Your desire to lose weight must become more important than the desire to overeat or to not exercise. Both long-range and short-range realistic goals need to be established. Several experts in weight control, such as Tremblay and Wadden, indicated that for overweight individuals a 10–15 percent weight loss is a reasonable goal over 4–6 months. Thus, a long-range goal may be to lose 30 pounds over 6 months, whereas a short-range goal would be to lose about 1–2 pounds per week. Losing 30 pounds may seem like a daunting task, but setting small goals, a few pounds at a time, is one of the keys to success indicated by the National Weight Control Registry. A long-range goal may also include a large number of behavioral changes to achieve the 30-pound weight loss, but the number of changes would be phased in gradually on a short-term basis. Do not expect to make all recommended behavioral changes overnight. (See figure 11.2.)

As the saying goes, nothing breeds success like success, so it is extremely important to set short-term goals that may be attainable in a reasonable length of time so that you may experience multiple successes in pursuit of your long-term goal. When you achieve your first short-term goal, a new short-term goal should be established as you progress toward your long-term goal. It is also important to remember that no initial short-term goal is too small, nor is any new short-term goal too small in the progress toward your long-term goal. The U.S. Department of Health and Human Services has developed a Website focusing on many small steps that may help individuals achieve diet and exercise goals in a weight-loss program. Appendix H lists 120 small steps to a healthier diet and increased physical activity. As you achieve each short-term goal, you should reward yourself with something appropriate to the occasion; a reward will provide you with positive feedback to your commitment to your weightloss program. www.smallstep.gov This Website provides numerous small steps relative to diet, cooking, drinking, and exercise that help promote weight loss. One set of small steps is for children and another for teens and adults.

One of the first steps in a behavior modification program is to identify those physical and social environmental factors that may lead to problem behaviors. Keeping a diary of your daily activities in your daily planner for a week or two may help you identify some behavioral patterns that may contribute to overeating and extra body weight. The following are some of the factors that might be recorded each time you eat, along with a brief explanation of their possible importance. You should also record your daily physical activity. You may use the record of 24-hour activity form as a guide, which also may help in the calculation of your EER in the MyTracker program. Type of food and amount This may be related to the other factors. For example, do you eat a high-Calorie food during your snacks? Meal or snack You may find yourself snacking four or five times a day. Time of day Do you eat at regular hours or have a full meal just before retiring at night? Degree of hunger How hungry were you when you ate—very hungry or not hungry at all? You may be snacking when not hungry. Activity What were you doing while eating? You may find TV watching and eating snack foods are related. Location Where do you eat? The office or school cafeteria may be the place you eat a high-Calorie meal. Persons involved With whom do you eat? Do you eat more when alone or with others? Being with certain people may trigger overeating. Emotional feelings How do you feel when eating? You might eat more when depressed than when happy, or vice versa. Exercise How much walking, stair climbing, or regular aerobic exercise do you get? Do you ride when you could possibly walk? How much time do you just sit? www.mhhe.com/williams9

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FIGURE 11.2

Short-term goals

Long-term goals

Time

1 month

6 months

Running

1 mile nonstop

5 miles nonstop

Weight

Lose 6 pounds

Lose 30 pounds

Goal setting is an important factor in an exercise program.

Self-discipline and self-control, and advanced planning:

Record of 24-hour diet and physical activity

Time of day

Activity

Total minutes

Meal or snack

Degree of hunger*

Activity while eating

Place of eating

Food and quantity

Others present

Reason for choice

Note: Record time, activity such as sleeping, sitting, watching TV, and exercise, and minutes of activity. For meals, fill in the other columns.You may also use these columns for comments regarding activities other than eating. Degree of Hunger: 0 = none; 1 = little; 2= moderate; 3 = high

Recording this information may make you more aware of the physical and social circumstances under which you tend to overeat or be physically inactive. This awareness may be useful to help implement behavioral changes that may make weight control easier. The following suggestions are often helpful:

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1. Establish realistic weight-loss goals. A loss of 10 percent can produce significant health benefits. 2. Establish weight loss as a high priority; commit to permanent lifestyle changes. 3. Think about this priority before eating. 4. Take small helpings deliberately as a means to control your weight. 5. Plan for a modest daily energy deficit, about 300–500 Calories, which will result in a gradual weight loss. 6. Check your body weight and shape on a regular basis, either daily or 2 to 3 times a week. Use this as a motivational tool.

Foods to eat: 1. Use low-Calorie healthful foods for snacks. 2. Plan low-Calorie, high-nutrient meals. 3. Plan your food intake for the entire day.

C H A P T E R 1 1 Weight Maintenance and Loss through Proper Nutrition and Exercise

4. Eat only foods that have had minimal or no processing. 5. Allow yourself very small amounts of high-Calorie foods that you like, but stay within daily caloric limitations. 6. Know the Food Exchange System, particularly, serving size and high-fat foods. Food purchasing: 1. Do not shop when hungry. 2. Prepare a shopping list and do not deviate from it. 3. Buy only foods that are low in Calories and high in nutrient value. Read and compare food labels to limit fat and sugar content. 4. Buy natural foods as much as possible. Food storage: 1. Keep high-Calorie food out of sight and in sealed containers or cupboards. 2. Have low-Calorie snacks like carrots and radishes readily available. Food preparation and serving: 1. Buy only foods that need preparation of some type. 2. Do not add fats or sugar in preparation, if possible. 3. Prepare only small amounts. Be able to visualize one serving size for any given food. 4. Do not use serving bowls on the table. 5. Put the food on the plate, preferably a small one. Location: 1. Eat in only one place, such as the kitchen or dining area. 2. Avoid food areas such as the kitchen or snack table at a party. 3. Avoid restaurants where you are most likely to buy highCalorie items. Restaurant eating: 1. When eating out, select the low-Calorie items. 2. Request your meals be prepared without fat. 3. Have condiments like butter, mayonnaise, and salad dressing served on the side; use sparingly. 4. Order water, not a high-Calorie beverage. 5. Be wary of portion sizes as most restaurant servings contain 2–3 normal servings. Ask for a take-home box before you eat and put half of your meal in the box. Methods of eating: 1. Eat slowly; chew food thoroughly or drink water between bites. 2. Eat with someone, for conversation can slow down the eating process. 3. Cut food into small pieces. 4. Do not do anything else while eating, such as watching TV. 5. Relax and enjoy the meal. 6. Eat only at specified times. 7. Eat only until pleasantly satisfied, not stuffed. 8. Spread your Calories over the day, eating small amounts more often.

Activity: 1. Decrease the amount of time spent in sedentary activities. Increase the amount of nonexercise activity thermogenesis (NEAT) by moving more and sitting less. 2. Walk more. Park the car or get off the bus some distance from work. Briskly walk the dog. 3. Use the stairs instead of the elevator when possible. 4. Do exercise snacks. Take a brisk 10-minute walk instead of a coffee-donut break. Do this several times a day. 5. Get involved in activities with other people, preferably physical activities that will burn Calories. 6. Avoid sedentary night routines. 7. Start a regular exercise program, including both aerobic and resistance exercises. 8. Schedule exercise as an appointment in your daily planner. Mental attitude: 1. Recognize that you are not perfect and lapses may occur. 2. Deal positively with your lapse; put it behind you and get back on your program. 3. Put reminders on the refrigerator door at home or on your telephone at work. 4. Reward yourself for sticking to your plans. For the interested reader, the books by Dusek and Miller provide an in-depth coverage of behavior modification for weight-control purposes. Many of the commercial, medically oriented weightloss centers as well as organizations such as Weight Watchers International also may be sources of information. Self-taught, selfadministered weight-loss programs may also be very effective, as indicated in the study by Wayne Miller and his associates. Stress reduction techniques may also be important in a weightcontrol program. The Consumers Union indicates that emotional stress can hinder weight control by triggering the release of cortisol into the blood, which conserves fat and increases hunger. Exercise in itself may help reduce emotional stress, as may various relaxation techniques such as meditation and yoga. Individuals with clinical obesity may need professional assistance from health counselors to implement a behavior modification program for weight control. However, others with less severe weight problems may be able to initiate their own program if they have adequate accurate information. Research has shown that most individuals initiating a weight-loss program do use acceptable strategies, such as exercising and eating a low-fat, low-Calorie diet, but use of these strategies becomes inconsistent in subsequent years, resulting in weight regain. In a recent position statement, the American Dietetic Association resolved that successful weight management requires a lifelong commitment to healthful lifestyle behaviors emphasizing eating practices and daily physical activities that are attainable and enjoyable. The remainder of this chapter focuses on the development of a proper lifelong diet and exercise program for losing weight safely and keeping it off. What usually happens is individuals suffer a lapse in the weight-loss program, such as an injury that prevents participation in their normal exercise program. If they do not have an alternative exercise program, some weight gain may occur until

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they can resume exercising. Kelly Brownell, in the LEARN (Lifestyle, Exercise, Attitudes, Relationships, Nutrition) program for weight control, indicates that one of the keys in weight control is to prevent a lapse from becoming a relapse, or a resumption of old behaviors and total weight regain. When a lapse occurs, Brownell recommends you stay calm, analyze the lapse, and renew your diet and exercise commitment. By analyzing your lapse, you should be able to find a solution to help you get back on track. If unable to do so, seek some assistance from a qualified health professional.

Ke y C o n c e p t s 䉴 Keeping a record of your daily eating habits will help you identify

behavioral patterns relative to overeating and may be used as a basis for the elimination of cues that trigger eating. 䉴 Behavior modification is a very important part of a weight-control program. In order for weight control to be effective over a lifetime, dietary and exercise behaviors may need adjustments in order to curtail caloric intake and increase energy expenditure.

C h e c k f o r Yo u r s e l f Using information presented in the text, keep a record of your dietary and physical activity behaviors for a period of 3–7 days. Compare your findings to the text discussion regarding dietary and physical activity behaviors that may help you maintain a healthy body weight.

Dietary Modifications Numerous weight-loss dietary plans are available and each is based on some combination of macronutrient—carbohydrate, fat, protein—content. To achieve weight loss, the key to each diet plan is to consume fewer Calories than expended. Most diet plans do so. For example, the Consumers Union recently rated 15 different diet books and plans varying in macronutrient content; the daily range was 1,340 to 1,910 Calories and most averaged about 1,500 Calories, an energy intake that would lead to weight loss in most individuals. As we shall see, there are high-carbohydrate, high-fat, and highprotein diets, and supporters for each. For example, in a recent interview, Taubes, author of Good Calories, Bad Calories, indicates that the key to weight loss is to eat fewer carbohydrates. He recommends the original Atkins diet, which is basically a high-fat diet. On the other hand, Dean Ornish, in his book Eat More, Weigh Less, recommends a diet containing 70 percent or more carbohydrate with no more than 10 percent fat. Barry Sears, who developed The Zone diet, stresses the importance of a high-protein diet. Nutrition scientists have designed experiments to compare specific diet plans. Subjects would be assigned to one plan or another and weight loss would be followed for a period of time, such as a year or so. Although such studies have provided us with some evidence regarding the efficacy of certain diets, Winkler notes that most have a fundamental flaw; the basic problem with compara452

tive diet trials is our inability to measure what people eat so we do not know if subjects actually follow the diets being tested and compared. Brian Wansink, in his book Mindless Eating: Why We Eat More Than We Think, provides examples as how it is so easy to consume extra Calories. As the actual daily caloric intake is not measured in long-term comparative diet studies, consuming an extra 100 Calories daily could distort the research findings. Nevertheless, sufficient evidence is available to provide prudent dietary guidelines for weight loss and maintenance. Such diets should also promote health. Ma and others recently compared the dietary quality of popular weight-loss plans for their capacity to prevent cardiovascular disease, and we discussed the concepts of healthful sources of carbohydrate, fat, and protein in the DASH and OmniHeart diets in chapter 9. In general, healthful, weight-control diets are based on selecting good carbohydrates, good fats, and good proteins. You can use the MyPyramid food guide as a means to plan a healthful diet to achieve your desired body weight goal. www.MyPyramid.gov Click on Steps to a Healthier Weight to obtain information on diet and exercise guidelines for weight control.

How can I determine the number of Calories needed in a diet to lose weight? To answer this question you need to provide two figures. First, you need to provide an estimate of how many Calories you need to consume daily to maintain your current body weight. As noted previously on pages 444–447, several techniques are available, so you should select one to provide an estimate of the number of Calories you may need to consume daily to maintain your current body weight. Second, you need to provide an estimate of the amount of weight that you want to lose, as discussed on pages 447–448, and then determine how much you want to lose per week. One pound is the preferable goal, but you may lose up to 2 pounds safely. Some computerized dietary analysis programs will calculate your estimated energy intake needed to lose about 1–2 pounds per week. For our purposes, we will use the value of 3,500 Calories to represent 1 pound of body-fat, or body-weight, loss. To lose 1 pound of body fat, you must create a 3,500 Calorie deficit. To lose 1 pound per week, your daily caloric deficit should be 500 (3,500/7). To lose 2 pounds per week, the recommended maximum unless under medical supervision, the daily caloric deficit should be 1,000 (7,000/7). Once you calculate your daily energy needs to maintain your current body weight, simply subtract your daily caloric deficit from it; the result will be your recommended daily caloric intake. An example is presented below: Example: 35-year-old woman with low physical activity levels who weighs 140 pounds desires to lose 1 pound per week. 1. From table 11.3, Calories/lb needed to maintain body weight: 13 2. Predicted total number of Calories to maintain body weight: 13 × 140 = 1,820 Calories/day

C H A P T E R 1 1 Weight Maintenance and Loss through Proper Nutrition and Exercise

3. Recommended daily caloric deficit = 500 Calories/day 4. Recommended daily caloric intake = 1,320 Calories (1,820 – 500 = 1,320 Calories/day) However, it is important to note that most health professionals do not recommend weight-loss diets lower than 1,000 Calories unless medically supervised.

How can I predict my body-weight loss through dieting alone?

most of the 500–1,000 daily Calorie deficit be achieved by eating less food. However, 100–200 Calories of this deficit is achievable through daily exercise, such as walking for 30 minutes or so. Using exercise to contribute to your daily caloric deficit means your food caloric deficit may be reduced accordingly.

Why does a person usually lose the most weight during the first week on a reducing diet? The principal objective of a diet is to lose body fat, not just body weight. If you start a diet with a significant caloric deficit, say 1,000 Calories/day, it would normally take you about 3.5 days to lose 1 pound of body fat. However, body-weight loss would be more rapid than this during the first several days, possibly totaling as much as 3–4 pounds. A large percentage of this weight loss would be due to a decrease in body carbohydrate and associated water stores. When you restrict your food intake, the body would then draw on its reserves to meet its energy needs. These reserves consist of both fat and carbohydrate stores, but much of the carbohydrate, stored as liver and muscle glycogen, could be used up in several days, particularly with low-carbohydrate intake, such as the Atkins diet. Because 1 gram of glycogen is stored with about 3 grams of water, a significant weight loss could occur. For example, 300 grams of glycogen, along with 900 grams of water stored with it, would account for a loss of 1,200 grams, or 1.2 kilograms;

As mentioned in the last chapter, the human body is composed of different components, most commonly compartmentalized into body fat and lean body mass; lean body mass is about 70 percent water. On a dietary program, weight loss may reflect decreases in body fat, body water, or muscle mass, all of which present different caloric values. For example, 1 pound of body fat equals about 3,500 Calories, while an equivalent weight of water contains no Calories. Because of this fact, it is difficult to predict exactly how much body weight one will lose on any given diet, but an approximate value of the time it will take to lose excess body fat may be obtained. The key point is the caloric deficit. The number of days it takes for this daily deficit to reach 3,500 is how long it will take you to lose 1 pound. Table 11.4 illustrates the importance of the caloric deficit in determining the rapidity of weight loss by dieting. This table is based upon the value of 3,500 Calories TABLE 11.4 Approximate number of days required to lose weight for a given caloric deficit for a pound of body fat. The higher the deficit, the faster you lose Daily caloric To lose To lose To lose To lose To lose weight. However, rapid weightdeficit 5 pounds 10 pounds 15 pounds 20 pounds 25 pounds loss programs are not usually desirable, and the dieter should realize 100 175 350 525 700 875 that a moderate caloric deficit, say 200 87 175 262 350 438 500 Calories/day, may effectively reduce weight in time and yet pro300 58 116 175 232 292 vide a satisfying diet. As noted below, however, as body weight is 400 44 88 131 176 219 lost the caloric intake needs to be 500 35 70 105 140 175 reduced slightly if one wants to maintain a standard daily caloric 600 29 58 87 116 146 deficit. Although these prediction meth700 25 50 75 100 125 ods are good for the long run, daily 800 22 44 66 88 109 body-weight changes may not coincide with daily caloric deficits. 900 19 39 58 78 97 It is very important to note that although we are discussing dieting 1,000 17 35 52 70 88 alone to create a daily caloric 1,250* 14 28 42 56 70 deficit, exercise also may be used to increase this deficit. When starting a 1,500* 12 23 35 46 58 weight-loss program, the National Institute of Health recommends that See text for explanation. *Note Weight loss greater than 2 pounds per week generally not recommended. www.mhhe.com/williams9

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this would equal over 2.5 pounds alone. About 70 percent of the weight loss during the first few days of a reduced-Caloric diet may be due to body-water losses. About 25 percent comes from body-fat stores and 5 percent from protein tissue. As body protein is used for energy, the excess nitrogen needs to be excreted, and this increases water output, about 4–5 grams of water per gram of protein. As noted later, very-low-Calorie diets may lead to greater protein losses, but slower weight losses, such as with a daily 500-Calorie deficit, will help conserve body protein. If you desired to lose a maximal amount of weight during a 2- to 3-day period, water restriction would cause an even greater weight loss. However, this practice is not recommended, as you would only be decreasing body-water levels. They would return to normal when you returned to normal water intake. There is one additional point relative to body water. At the conclusion of your diet, if you return to a normal caloric diet to maintain your new body weight, you may experience a rapid weight gain of 2 or 3 pounds. This may represent a replenishment of your body glycogen stores with the accompanying water weight. It is important to keep in mind that rather large fluctuations in daily body weight, say in the order of 2 to 3 pounds, are not due to rapid changes in body fat or lean body mass; these fluctuations are due primarily to body-water changes accompanying carbohydrate and protein losses.

Why does it become more difficult to lose weight after several weeks or months on a diet program? Weight loss may be rapid during the first few days on a diet, primarily because of water loss. Because water contains no Calories, our caloric loss does not need to total 3,500 in order to lose 1 pound of weight. We may lose 1 pound of body weight with a deficit of only about 1,200 Calories, because 70 percent of the weight loss is water. The 1,200 Calories are mostly from fat with a small amount of protein. However, by the end of the second week of dieting, water loss may account for only about 20 percent of body-weight loss; one pound of weight loss will now cost us approximately 2,800 Calories. At the end of the third week, water losses are minimal. The energy deficit to lose 1 pound of body weight now approximates 3,500 Calories. In essence, as you continue your diet, weight losses cost you more Calories because less body water is being lost. At the end of three weeks, you still can be losing weight, but at a much slower rate than during the early stages. Another factor also slows down the rate of weight loss. As you lose weight, you need fewer Calories to maintain your new body weight. Let’s take an example. Suppose you are an athlete who weighs 200 pounds and from table 11.3 you see that you need 18 Calories/pound body weight to maintain your weight. At 200 pounds this would represent 3,600 Calories/day (200 × 18). However, if your weight drops to 180 pounds after dieting for 10 weeks, you now need only 3,240 Calories/day (180 × 18), a difference of 360 Calories per day. If you want to continue to have a standard caloric deficit, then you will have to adjust your caloric intake as you lose weight. Suppose our 200-pounder wanted to have a daily caloric deficit of 1,000 Calories. His initial diet 454

should then contain about 2,600 Calories/day (3,600 – 1,000). However, once he is down to 180 pounds, his diet should now include only 2,240 Calories/day (3,240 – 1,000). If he did not adjust his diet from 2,600 Calories, then the daily deficit would only be 640 Calories/day (3,240 – 2,600), not the standard 1,000 he wanted. Weight loss would continue, but at a slower rate. You should realize that the rate of weight loss will slow as a natural consequence of your diet, but the weight you are losing at that point is primarily body fat. Keeping a standard caloric deficit may also require an additional reduction in caloric intake as you progress on your diet. Knowledge of these factors may help you through the latter stages of a diet designed to attain a set weight goal. Other factors associated with very-low-Calorie diets and exercise, discussed later, may also influence the magnitude of the caloric intake necessary to sustain a given rate of weight loss.

What are the major characteristics of a sound diet for weight control? As you probably are aware, literally hundreds of different diet plans are available to help you lose weight. Hardly a month goes by without a new miracle diet being revealed in a leading magazine or Sunday newspaper supplement. Diet books frequently appear on the New York Times Bestseller List. These diet plans are recycled over the years and simply represent variations of different themes. Some of these plans may be highly recommended, for they satisfy the criteria for a safe and effective weight-reduction diet. On the other hand, many of these diets may be nutritionally deficient or even potentially hazardous to your health. Certain types of fad diets should be avoided. Diets that restrict or eliminate various foods, including one-food diets such as the rice diet or the bananas-and-milk diet, may be deficient in certain key nutrients. Avoid miracle diets that are advertised to contain a special weight-reducing formula or fat-burning enzymes, for such compounds simply do not exist or are not effective. In general, you should avoid diets that promise fast and easy weight losses. There is no fast and easy dietary method to lose excess body fat. Carbohydrate, fat, and protein, and alcohol for those who drink, are the only dietary sources of Calories. Alcohol is not an essential nutrient, but as noted later may play a significant role in weight gain. The majority of our dietary Calories come from carbohydrate and fat with smaller amounts from protein. As you may recall, the National Academy of Sciences has published an Acceptable Macronutrients Distribution Range (AMDR) for carbohydrate, fat, and protein, which represents the percent of dietary Calories that should be derived from each. • Carbohydrate AMDR: 45–65% • Fat AMDR: 20–35% • Protein AMDR: 10–35% Most popular weight-control diets have focused on limiting intake of either fat or carbohydrate, while some have stressed increased protein intake. Data comparing the caloric and macronutrient con-

C H A P T E R 1 1 Weight Maintenance and Loss through Proper Nutrition and Exercise

TABLE 11.5

Average daily calories

% carbohydrates

% fat

Weight Watchers

1,450

56

24

Atkins

1,520

11

60

South Beach

1,340

38

39

Volumtetrics

1,500

55

23

Jenny Craig

1,520

62

18

Zone

1,660

40

30

Ornish

1,520

77

6

Diet plan

that four meta-analyses of weight change occurring on ad libitum low-fat diets in intervention trials consistently demonstrate a highly significant weight loss, and con% cluded that the evidence strongly supports the low-fat diet protein as the optimal choice for the prevention of weight gain and obesity. However, they also noted that the nonfat 20 macronutrient composition of the diet is also important. Not all carbohydrates may be equal when it comes to 29 weight loss, and some diets have focused on the 23 glycemic index as the key to carbohydrate intake, as highlighted in such books as The GI Diet and Good 22 Carbs, Bad Carbs. In his review on how to maintain a healthy body weight, Astrup indicated that the role of 20 the glycemic index diet plan for body-weight control is 30 controversial. Although Roberts indicates that consumption of high-glycemic index carbohydrates may increase 17 hunger and promote overeating as compared to consumption of items with a lower glycemic index. Das and others found that Calorie-restricted diets differing substantially in glycemic load can result in similar long-term weight loss. Because individuals respond differently to carbohydrate intake, Pittas and Roberts suggest such diet plans may need to be individualized based on metabolic profiles, such as insulin sensitivity. In particular, Ebbeling and others note that reducing glycemic load may be especially important to achieve weight loss among individuals with high insulin secretion. In this regard, Astrup and others report that several intervention studies show that sugar in drinks is more likely to produce weight gain than solid sugar in foods, which Ludwig and others found to be especially true in the etiology of obesity in children. As noted in chapter 4, healthier, or good, carbohydrates are rich in dietary fiber, which may play an important role in weight-loss diets. For example, Howarth and others reported that increasing dietary fiber in the diet, by as little as 14 additional grams per day, is associated with a 10 percent decrease in energy intake and significant weight loss over time. Going from the average intake of 15 grams per day up to the recommended 25–38 grams may be an effective part of a total overall weightcontrol program. Fiber increases the volume of food you eat, which can suppress hunger, the principle underlying popular diet books such as The Volumetrics Eating Plan and Eat More, Weigh Less. Incidentally, Consumer Reports recently ranked The Volumetrics Eating Plan by Barbara Rolls as the top-rated diet book. Most members in the National Weight Control Registry consume a high-carbohydrate diet, with about 225 grams for a 1,500-Calorie plan, or about 60 percent of Calories from carbohydrate. They also consume about 30 percent of daily Calories from fat. A low-fat or moderate-fat, high-carbohydrate weight-loss diet may be effective, but selection of nutrient-dense carbohydrates is the key. Although some have suggested that low-fat diets may induce weight gain because of the increased carbohydrate in the diet, Howard and others found such was not the case over the course of 7 years if vegetables, fruits, and whole grains replaced the dietary fat. As will be noted, the choice of the fat and protein content in a high-carbohydrate diet is also important.

Calorie and macronutrient content of popular diets

Adapted from Consumers Union, Rating the diets. Consumer Reports 70 (6):21, 2005.

tent of some popular diets are presented in table 11.5. The key point is that each diet is relatively low in Calories. Riley has placed popular self-help weight-loss diets on a continuum of themes ranging from antifat to anticarbohydrate. The benefits and drawbacks of both the high-carbohydrate, low-fat (antifat) and low-carbohydrate, high-fat (anticarbohydrate) diets, along with diets somewhere between the two extremes, have been the subject of detailed reviews. In general, these reviews indicate that weight loss can be achieved with a variety of diet interventions, and that it is unlikely that one diet is optimal for all overweight or obese persons. Both low-fat and low-carbohydrate diets have been shown to induce weight loss and reduce obesity-related comorbidities. Reducing caloric intake is the key to the success of any diet. For example, in a recent one-year study, Dansinger and others compared the effects of the Atkins, Ornish, Weight Watchers, and Zone diets, and reported that each popular diet modestly reduced body weight and decreased several markers for coronary heart disease, but there were no differences among the diets. All reduced-Calorie diets were successful in inducing modest weight loss. Recent studies led by Gardner and Truby support these findings. Most reviews also indicate no significant differences in weight loss with diets of varying macronutrient content, provided caloric intake is similar. The interested reader is referred to the reviews by Brehm and D’Alessio, the Consumers Union, Klein, Nordmann, and Volek. Low-Fat, High-Carbohydrate Weight-Loss Diets At the antifat end of Riley’s continuum are diets such as those proposed by Dean Ornish and Nathan Pritikin that recommend only 10–15 percent of dietary Calories be derived from fat, which is lower than the AMDR. Reducing fat in the diet is a sound strategy to lose weight. The American College of Sports Medicine notes that a 10 percent reduction in fat intake can have a significant impact on energy balance and body weight over the long term. Astrup and others assessed the role of macronutrient content of diets on weight loss. They noted

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Low-Carbohydrate, High-Fat Weight-Loss Diets On Riley’s anticarbohydrate end of the continuum are diets such as Dr. Atkins’ New Diet Revolution. The Atkins diet has various phases, starting off as low as 20 grams of carbohydrate a day, mainly from nutrientdense foods such as leafy green salads. The heart of the diet contains foods high in fat and protein, such as poultry, fish, red meat, and eggs, but gradually progresses to other stages with increasing amounts of carbohydrates, but much lower than AMDR levels. Such diets are also referred to as low-carbohydrate, high-fat, and highprotein weight-loss diets. The South Beach Diet, by Agatston, limits saturated fats and focuses on healthier carbohydrates, which health professionals indicated appears to be a healthier version of the Atkins diet. Research suggests such diets may be effective. Liebman indicated the Atkins diet may work because it virtually eliminates a whole category of food—carbohydrates, while a Tufts University report indicates that individuals who adopt the Atkins diet generally cut an average of 1,000 Calories per day from their diet, which is most likely the reason underlying its success. Correspondingly, Bravata and others reviewed 109 studies involving the use of lowcarbohydrate diets and concluded that participant weight loss was principally associated with decreased caloric intake. One of the criticisms of the Atkins diet was the possible adverse effects on the serum lipid profile and predisposition to cardiovascular disease. However, reviewers such as Volek and Sharman also noted that low-carbohydrate diets had no significant adverse effect on serum lipids, fasting serum glucose, fasting serum insulin levels, or blood pressure. Most recently, Gardner and others found that the Atkins diet plan, over the course of a year, achieved similar weight losses and favorable changes in blood lipid profile as several other diets, including the Ornish plan. The Consumers Union notes that if you have a healthy serum lipid profile, you most likely will do no harm to your health by adopting the Atkins diet plan for 12 weeks to jump start your weight-loss program. Moreover, low-carbohydrate diets may be suitable long term. Over the course of 2 years, Shai and others compared the effects of three diet plans on weight loss in moderately obese subjects, mostly males. The three diets were: low-fat, restricted-Calorie; Mediterranean, restricted-Calorie; or lowcarbohydrate, non-restricted-Calorie. Although subjects in all three groups lost weight, those on the Mediterranean and lowcarbohydrate diets lost more weight. Moreover, improvements in serum lipid levels were greater in the low-carbohydrate group while improvement in glucose metabolism in diabetic subjects was greater in the Mediterranean diet group. Weight loss may be rapid at first, primarily due to body fluid losses associated with decreased carbohydrate intake and the resultant decrease in muscle glycogen and associated bound water. Westman and others found that a very-low-carbohydrate diet (less than 25 grams of carbohydrate per day) led to sustained weight loss during a 6-month period. Subjects lost slightly more than 10 percent of body weight, but only about 3 percent of that was body fat, indicating a significant loss of lean body mass. Preferably, a weight-loss diet should induce body-fat losses, not lean body mass such as muscle. Foster and others also recently found that such a diet, as compared to a conventional low-fat diet, induced significantly greater weight 456

losses over 3–6 months, but there were no differences in weight loss at the end of a year. Adherence was poor and attrition was high in both diet groups, suggesting neither is an appropriate lifelong diet. Based on their comprehensive review, Bravata and others concluded that there is insufficient evidence to make recommendations for or against the use of low-carbohydrate diets. However, although the Atkins diet may be successful, it is not well represented among those in the National Weight Control Registry. Only 8 percent of registry members adhered to a diet containing 90 grams or less of carbohydrate per day. Moderation in dietary fat intake may be the key. As noted, individuals in the National Weight Control Registry consume about 30 percent of daily energy from fat, which is considered moderate. In a recent 14-month study, Azadbakht and others reported significantly greater reductions in body weight, waist circumference, and cardiovascular risk factors in subjects consuming a moderate-fat (30 percent) versus a low-fat (20 percent) diet. The authors suggested better dietary adherence with the moderate-fat diet may be the reason for its successful effects. Shai and others also suggested that Mediterranean and low-carbohydrate diets may be effective alternatives to low-fat diets. High-Protein Weight-Loss Diets Some diets, such as the Zone diet, recommend that protein should account for 30 percent or more of energy, and are marketed as high-protein diets. Although this recommendation falls within the AMDR for protein (10–35 percent), it is generally regarded as high because it may be twice the typical protein intake of 12–15 percent. However, other diets such as Atkins and South Beach also may be regarded as somewhat high in protein. High-protein weight-loss diets have been recommended for several reasons. For example, in recent reviews of dietary protein intake and body-weight regulation, Paddon-Jones and others and Westerterp-Plantenga and Lejeune cited several possible benefits from increased protein intake. • Increased thermogenesis; increased body temperature suppresses appetite. • Decreased energy efficiency; more energy is used to process protein. • Maintenance of lean body mass; muscle is the main protein reservoir in the body. In a recent study, Leidy and others reported that the acute intake of protein is associated with lower levels of ghrelin after the meal which, like thermogenesis, could also decrease the appetite. They also reported that over time, chronic protein intake influences thermogenesis and protein utilization. Such acute and chronic effects of protein intake may help promote weight loss. Some recommend that weight-loss diets contain 20–30 percent of energy content from protein. In a recent study with normalweight individuals who were not on a weight-loss diet, Weigle and others found that increasing dietary protein content from 15 to 30 percent of energy intake, while keeping carbohydrate content constant, produced a sustained decrease in caloric intake. In another study involving high-protein diets (30 percent), Leidy and others reported improved perceptions of satiety and pleasure dur-

C H A P T E R 1 1 Weight Maintenance and Loss through Proper Nutrition and Exercise

ing dietary energy restriction, and the diet helped women preserve lean body mass. In a review of clinical trials, Hu concluded that short-term, high-protein diets induce weight loss and improve blood lipids, but also notes that long-term data are missing; the evidence suggests partially replacing refined carbohydrates with protein sources that are low in saturated fat. In this regard, Layman and others indicated that high-protein, low-carbohydrate diets have been found to have some positive health effects, such as reducing serum triglycerides and blood pressure, increasing HDLcholesterol, and improving glycemic control, factors that could reduce risk for heart disease and diabetes. St. Jeor and others, representing the Nutrition Committee of the American Heart Association, noted that high-protein diets may not be harmful for most healthy people for a short period of time, but like Hu notes there are no long-term scientific studies to support their overall efficacy and safety. Friedman indicated there is no clear kidney-related contraindication to high-protein diets in individuals with healthy kidney function, but individuals at risk for chronic kidney disease should be screened for serum creatinine and proteinuria before the initiation of such a diet. Another health concern with high-protein diets is increased calcium losses, but Johnston and others reported no adverse effects of such diets on calcium balance. Although diets containing 25–30 percent protein may be marketed as high-protein, such diets are actually within the AMDR of 10–35 percent of energy from protein. Nevertheless, individuals who have any health concerns should check with their health professionals before initiating such dietary changes. Balanced Weight-Loss Diets In the middle of Riley’s continuum of popular weight-loss diets are mainly those recommended by most professional health organizations, such as the American Heart Association and the American Dietetic and American Diabetes Associations’ Food Exchange System Diet, which is the basis of the diet plan advocated in this text. Highly recommended diets are based upon sound nutritional principles and also are designed to satisfy the individual’s personal food tastes. Research with dieters has shown that any weightreduction diet, to be safe, effective, and realistic, should adhere to the following principles: 1. It should be reduced in Calories and yet supply all nutrients essential to normal body functions. It is important to stress the importance of dietary Calories. Dich and others purposely overfed normal young men, about 1,200 additional Calories per day, with either a carbohydrate-rich or a fat-rich diet for 21 days. They found that the increase in body weight and fat mass was no different between the two diets. Excess dietary Calories lead to weight gain and this study indicates that it does not matter if they come from carbohydrate or fat. As far as energy is concerned, a Calorie from a banana is the same as one from a brownie. 2. It should contain a wide variety of foods that appeal to your taste and help prevent hunger sensations between meals. Low-glycemic-index diets with dietary fiber and moderate amounts of protein and fat may help to suppress the appetite. With respect to weight control, Kris-Etherton and others suggest that a moderate-fat diet can be as, or even more, effective

than a lower-fat diet, because of advantages with long-term adherence and potentially favorable effects on lipids and lipoproteins. However, they also note that because fat is energy dense, moderation in fat intake is essential for weight control. 3. It should be suited to your current lifestyle and personal preferences, being easily obtainable whether you eat most of your meals at home or you dine out frequently. 4. It should provide for a slow rate of weight loss, about 1–2 pounds per week. 5. It should be a lifelong diet, one that will satisfy the first three principles once you attain your desired weight. In any diet plan, foods should be selected that adhere to the principles of healthful eating. This information was summarized in chapter 2, and 20 guidelines you can use in the selection and preparation of foods to reduce caloric intake are presented later in this chapter. As proper knowledge is a key to behavioral modification, learning the caloric and nutrient content of a wide variety of foods may be a very important strategy in a weight-control program.

Is it a good idea to count Calories when attempting to lose body weight? There are both pros and cons to counting Calories. On the con side, counting Calories may not be practical for many who are too busy to plan a daily menu designed around a caloric limit. How many Calories are in the lunch or dinner you eat out daily? And how about serving sizes? Can you picture 3 ounces of roast beef or an ounce of cheese? Also, it may be difficult to calculate the exact amount of Calories consumed, as the caloric content in foods may vary somewhat. For example, certain slices of bread are larger than others and may have a correspondingly higher caloric content. Although these problems are not difficult to solve, it does take some effort. On the pro side, counting Calories may be very helpful during the early stages of a diet. Knowledge of the food exchange lists and use of Nutrition Facts on food labels will enable you to substitute one low-Calorie food for another in your daily menu. Additionally, research suggests that recording everything you eat when you start dieting, including the caloric content, can help you stick with your weight-loss program. As you become familiar with the caloric content of various foods, it becomes easier to select those that are low in Calories but high in nutrient value, and to avoid those foods just the opposite, high in Calories and low in nutrients. It will require a little effort in the beginning phases of a diet to learn the Calories in a given quantity of a certain food, but once learned and incorporated into your lifestyle this knowledge is a valuable asset to possess not only when trying to lose weight but also when maintaining a healthy weight over a lifetime. As you incorporate low-Calorie, high-nutrient foods into your diet, it will eventually become second nature to you, and you may eliminate the need to count Calories. The key to keeping track of Calories is to keep track of dietary fat and sugar and portion sizes. With knowledge of the Food Exchange System and the new food labels, you should be able to determine the grams of fat that you consume daily. Less than 30 percent of your dietary Calories should be derived from fat. On www.mhhe.com/williams9

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a diet of 1,800 Calories per day, less than 540 Calories should come from fat (1,800 × 0.30), which is the equivalent of 60 grams of fat because 1 gram of fat contains 9 Calories (540/9). Diets containing only 20 percent fat Calories may also be recommended. Less than 10 percent of your dietary Calories should come from sugar. On this 1,800-Calorie diet, that would be less than 180 Calories (45 grams) from sugar. Once you have attained your desired weight, a good set of scales would be most helpful. Keeping track of your weight on a day-to-day or weekly basis will enable you to decrease your caloric intake for several days once you notice your weight beginning to increase again. Most individuals in the National Weight Control Registry who have lost weight and kept it off weigh themselves daily once their weight goal is reached, noting it is easier to deal with a gain of a few pounds rather than 10 or 20. Short-term prevention is more effective than long-term treatment. The dietary habits you acquire during the Calorie-counting phase of your diet will help you during these short-term prevention periods.

What is the Food Exchange System? At this time it is important to expand our discussion of the Food Exchange System, which was introduced in chapter 2. The Food Exchange System was developed by a group of health organizations, including the American Diabetes Association and the American Dietetic Association, as a means of advising patients about healthy eating. In essence, six food groups were established, and foods were assigned to these groups on the basis of similar caloric content and nutritional value. For our purposes at this time, we will concentrate upon the caloric value, but you may also want to refresh your memory on the grams of fat per food exchange. The six food exchange lists may be found in appendix E. You should study these lists and get an idea of the types and amounts of foods in each that constitute one exchange. Memorizing the caloric value of each food exchange is instrumental in determining the number of Calories you consume daily and also in planning a healthful, low-Calorie diet. In a recent study, Benezra and others found that the intake of most nutrients can remain at recommended levels when the Food Exchange System is used to plan a weight-loss program. The caloric content and grams of fat of one serving from each of the six exchanges are listed below and expressed in figure 11.3. 1 vegetable exchange 1 fruit exchange 1 fat exchange 1 starch exchange 1 meat exchange Very lean Lean Medium fat High fat 1 milk exchange Skim Low fat Whole 458

= 25 Calories; 0 g fat = 60 Calories; 0 g fat = 45 Calories; 5 g fat = 80 Calories; 0–1 g fat = 35–100 Calories = 35 Calories; 0–1 g fat = 55 Calories; 3 g fat = 75 Calories; 5 g fat = 100 Calories; 8 g fat = 90–150 Calories = 90 Calories; 0–3 g fat = 120 Calories; 5 g fat = 150 Calories; 8 g fat

Milk

1 cup skim milk

=

90 calories

Meat

1 ounce very lean meat

=

35 calories

Fat

1 tablespoon oil or butter =

45 calories

Fruit

1 medium piece

=

60 calories

Vegetable

1/ 2

=

25 calories

Starch

1 slice bread

=

80 calories

cup

F I G U R E 1 1 . 3 Knowledge of the various food exchanges and their caloric values can be very helpful in planning a diet. With a little effort, you can learn to estimate the caloric value of most basic foods. See appendix E for other food examples and serving sizes.

Table 11.6 presents a breakdown of the carbohydrate, fat, protein, and Calorie content of each food exchange.

How can I determine the number of Calories I eat daily? You may use the guide presented earlier in this chapter to record your daily physical activity, including what you eat and drink. Carry a small notebook with you along with some reminder, such as a rubber band around your wrist, to record your activity and food intake in detail. To calculate your caloric intake, you can use information provided by food labels or from the Food Exchange System in appendix E. Food intake should be recorded over a 3–7 day period, as one single day may give a biased value. Experiments have shown that this method may provide relatively accurate accounts of caloric intake if the amounts of food ingested are measured accurately. The main problem for most people is determining what and how much has been eaten. An 8-ounce glass of skim milk may be easy to record, and the caloric value from the food label or from appendix E is rather precise. However, how many Calories are in a slice of pizza at your favorite Italian restaurant? How big was the piece? What is the caloric content of the cheese, green peppers, pepperoni, and mushrooms? When we deal

C H A P T E R 1 1 Weight Maintenance and Loss through Proper Nutrition and Exercise

TABLE 11.6

Carbohydrate, fat, protein, and Calories in the six food exchanges

Food exchange

Carbohydrate

Fat

Protein

5

0

2

25

1

15

0

0

60

1

Fat

0

5

0

45

1 teaspoon (5 grams)

Meat and meat substitutes Very lean Lean Medium fat High fat

0 0 0 0

0–1 3 5 8

7 7 7 7

35 55 75 100

Starch

15

0–1

3

80

Milk Skim and very low fat Low fat Whole

12 12 12

0–3 5 8

8 8 8

Vegetables Fruits

Calories

Average serving size* ⁄2 cup cooked; 1 cup raw ⁄2 cup fresh fruit or juice

1 ounce

1

⁄3–1⁄2 cup cereal or pasta; 1 slice of bread

1 cup (8 fluid ounces) 90–110 120 150

Carbohydrate, fat, and protein in grams. 1 g carbohydrate = 4 Calories 1 g fat = 9 Calories 1 g protein = 4 Calories *See appendix E for specific foods. Source: Exchange Lists for Meal Planning, American Diabetes Association and American Dietetic Association, Chicago, ADA, 1995.

with complex food combinations such as this, our estimates of caloric content are not as precise. However, some estimates are presented in appendix E in the section on combination foods. For example, one-quarter of a 10-inch cheese pizza with thin crust contains two starch, two medium-fat meat, and one fat exchange, or the equivalent of 355 Calories. Although you may wish to use a ruler, a small measuring scale, and a measuring cup at home to accurately record the amount of food you eat, they are not practical for many dining situations. Lisa Young, in her book The Portion Teller Plan: The No-Diet Reality Guide to Eating, Cheating and Losing Weight Permanently, states that learning how to eyeball portion sizes accurately is an important skill. Some common objects in everyday life may serve as representative portion sizes for various foods, and some examples are presented in figure 11.4. The following may serve as guidelines for you to record the type and amount of food you eat: 1. In your notebook, record the foods you have eaten as soon as possible, noting the kind of food and the amount. Keep in mind that many servings today are supersized so that one of these servings may actually contain the Calories of 2–3 regular servings. Learn to visualize proper portion sizes and the associated Calorie content in various foods. 2. Check the labels of the foods you eat. Most commercial products today have nutritional information listed, including the number of Calories per serving. Record these data when available.

3. Calories for most fluids are given in relationship to ounces. For fluids, remember that 1 cup or regular glass is about 8 ounces, but many glasses now hold 12–16 ounces. Most regular canned drinks contain 12 ounces, although smaller and larger sizes are available; 20-ounce bottles are becoming increasingly popular. 4. Calories for meat, poultry, fish, and other related products are usually given by ounces. To get an idea of how many ounces are in these products, you could purchase a set weight of meat, say 16 ounces, and cut it into four equal pieces. Each would weigh approximately 4 ounces, or about the visual size of a deck of playing cards. For cheese, one ounce is about the size of a ping pong ball. Get a mental picture of these sizes and use them as a guide to portion sizes. 5. For fruits and vegetables the caloric values are usually expressed relative to 1⁄2 cup or a small-sized piece. At home, measure 1⁄2 cup of vegetables or fruit and place it in a bowl or on a plate. Again, make a mental picture of this serving size and use it as a reference. Compare the sizes of different fruits and notice the difference between a small, medium, and large piece. A medium piece fruit is about the size of a tennis ball, while a medium potato is about the size of a computer mouse. 6. For starch products, the Calories are most often expressed per serving, such as an average-size slice of bread or a dinner roll. In these cases it is relatively easy to determine quantity, but one slice of bread may contain 50 to 150 Calories or more, www.mhhe.com/williams9

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or

=

2 tbsp measure

2 tbsp salad dressing, peanut butter, margarine, etc.

=

1/2

to 2/3 cup measure

Medium/small fruit

=

1 standard bagel

Bagel or English muffin

=

1/2

Baked potato; ground or chopped foods; 1/2 cup generally equals 2 ounces.

=

1 cup

to 3/4 cup

Large apple or orange; 1 cup of ready-to-eat breakfast cereal

F I G U R E 1 1 . 4 A golf ball, tennis ball, large yo-yo, computer mouse, baseball, and fist make convenient guides to judge MyPyramid serving sizes. Additional handy guides include:

thumb ⫽ 1 oz of cheese; 4 stacked dice ⫽ 1 oz cheese; thumb tip to first joint ⫽ 1 tsp; matchbox ⫽ 1 oz meat; bar of soap or deck of cards ⫽ 3 oz meat;

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palm of hand ⫽ 3 oz 1 ice cream scoop ⫽ 1/2 cup handful ⫽ 1 or 2 oz of a snack food; and ping-pong ball ⫽ 2 tbsp.

depending on its size and density. Depending on the type of cereal, pasta, grain, or starchy vegetable, the measure for one exchange is usually 1⁄3 or 1⁄2 cup, but some serving sizes are larger, such as puffed cereals. See appendix E. Use a measuring cup and the mental picture concept again to estimate quantities. A cup of cold cereal is about the size of a large handful, whereas 1⁄2 cup of hot cereal is about the size of a tennis ball. A 2-ounce bagel is the size of a yo-yo. 7. For substances such as sugar, jams, jellies, nondairy creamers, and related products, make a mental picture of a teaspoon and tablespoon. These are common means whereby Calories are given. A teaspoon of butter or margarine is about the size of the tip of your thumb. One level teaspoon of sugar is about 20 Calories; jams and jellies contain similar amounts. Caloric values of other products may be obtained from nutrition labels. 8. Some combination foods, such as a homemade casserole, are included in appendix E. However, for combination foods not listed, you will need to list the ingredients separately to calculate the caloric content. Labels on most food products list caloric content per serving. 9. Caloric values for many fast-food restaurant items may be found in appendix F. Most fast-food restaurants provide fact sheets detailing information on the nutrient content of their products, but you need to ask for it. If nutrition fact sheets are not available when dining out in restaurants, you may obtain the caloric value of food items via e-mail. [email protected] When dining at a restaurant, use your personal digital assistant (PDA) or cell phone to send an email specifying the name of the food you are eating and within minutes you will receive a response providing the number of Calories, grams of carbohydrate and fat, as well as minutes of exercise walking, running, or cycling to burn those Calories.

Working with the Food Exchange System helps you learn the portion size and caloric content of various foods. Through experience you should be able to readily identify, within a small error range, the quantities of food you eat. This is not only helpful for determining your caloric intake but may also serve as a motivational device to restrict portion sizes when you are on a weightloss diet. The following represents an example of how you might record one meal and calculate the caloric intake from appendix E or food labels. Breakfast Food Milk, skim Eggs Toast, whole wheat with butter with jelly Orange juice Coffee with sugar TOTAL

Quantity 1 glass, 8 ounces 2, poached 2 slices 2 pats 1 tablespoon 1 glass, 8 ounces 1 cup, 8 ounces 1 teaspoon

Calories 90 150 160 90 60 120 0 20 690

Reading food labels and consulting the Food Exchange System helps you learn the caloric and nutrient value of various foods, and is recommended as a learning tool. You can then use computer programs to assess your diet on a daily basis. The MyPyramid Website, discussed previously, provides you the opportunity to keep a detailed history of your caloric and nutrient intake, and you can use the Energy Balance option to plan a weight-control diet. Appropriate dietary analysis software is also provided with your purchase of this textbook. www.mhhe.com/williams Access the McGraw-Hill Website to obtain dietary software available with the purchase of this book.

What are some general guidelines I can use in the selection and preparation of foods to promote weight loss or maintain a healthy body weight? A Consumer Reports survey of more than 32,000 dieters found that more than 80 percent who successfully lost weight and kept it off did so without following a specific plan. Instead, they used sensible strategies such as cutting portion size and staying away from sweets and junk food. The following 20 guidelines for weight control and healthy eating are based on several reputable sources of information, including the Food Exchange System, the National Weight Control Registry, and the DASH and OmniHeart diets. In essence, the four key points are: • • • •

Eat fewer Calories from fat and sugar Eat healthier carbohydrates Eat healthier fats Eat healthier proteins 1. Eat more nutrient-dense foods and fewer energy-dense foods. You need to decrease the number of Calories you consume daily. The key principle is to select foods, in appropriate portion sizes, and with high-nutrient density from across the six food exchanges or the food groups in the MyPyramid. Avoid energy-dense foods and drinks, such as bagels, soft pretzels, energy bars, smoothies, special coffees, and cocktails, all of which may be loaded with Calories. If you do buy convenience meals, select those that are low in Calories and fat. Check the label for total fat and total Calories from fat and sugar. This you can easily do by reading the label. Check figure 11.5. 2. Eat foods that make you feel full. Barbara Rolls, a renowned diet expert at Penn State University, based her excellent book, The Volumetrics Eating Plan, on this principle as did Dean Ornish with his book, Eat More, Weigh Less. Recent research by Ledikwe and others, from Rolls’ laboratory, reported that reducing dietary energy density is associated with weight loss in overweight individuals. High-volume, low-Calorie foods, such as salads, soups, vegetables, and whole grains, are rich in dietary fiber and water, and help provide a sensation of fullness that curbs hunger.

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CAL

ORIE-

SMART VA

NIL LA FUD GE SWIRL IC

E CREA

M

FUDG

E SW IRL

A LL- NATU R AL VANILLA IC E C

Nutrition Facts

Nutrition Facts

Serving Size: 1/2 cup Servings Per Container: 16

Serving Size: 1/2 cup Servings Per Container: 16

Amount Per Serving

Amount Per Serving

Calories 80

Calories from Fat 27

Calories 140

Calories from Fat 54 % Daily Value*

% Daily Value*

Total Fat 3g Saturated Fat 2g Trans fat 0g Cholesterol 10mg Sodium 40mg Total Carbohydrates 14g Dietary Fiber 4g Sugars 4g Protein 3g Vitamin A 6% Calcium 8%

• •

5% 10% ** 3% 2% 5% 16%

Vitamin C 0% Iron 2%

** Intake of trans fat should be as low as possible.

FIGURE 11.5

Total Fat 6g Saturated Fat 4g Trans fat 0g Cholesterol 20mg Sodium 45mg Total Carbohydrates 18g Dietary Fiber 0g Sugars 15g Protein 3g Vitamin A 4% Calcium 10%

• •

9% 20% ** 7% 2% 6% 0%

Vitamin C 0% Iron 2%

** Intake of trans fat should be as low as possible.

Reading labels helps you choose foods with less fat, sugar and Calorie content.

3. Restrict portion sizes. Although the intake of high-volume, low-Calorie foods like vegetables will help curtail hunger and promote weight loss, one of the major problems contributing to the increasing obesity in the United States is the consumption of large volumes of high-Calorie foods. Most fast-food eateries and convenience stores have increased portion sizes dramatically to give customers their money’s worth. As examples, years ago a family bottle of cola soda was 32 ounces, and now single servings of cola drinks may total up to 64 ounces, with free refills; a McDonald’s meal of a single hamburger, small fries, and cola had totalled 600 Calories, but today a larger meal with the same basic foods may total 1,800 Calories; a small bagel that once contained 200 Calories has been supersized to 500–600 Calories or more. Even manufacturers of “healthy” foods for dieters advertise “heartier” portions that weigh 50 percent more than the original version and contain more Calories. On the other hand, some food manufacturers are now marketing 100-Calorie healthful snacks, such as almonds, and some restaurants, such as TGIFriday’s, are offering smaller portion sizes with reduced prices. Decreasing the volume of high-Calorie foods is one of the most important dietary means to reduced body fat. 4. Eat less fat. Although restricting dietary Calories is most important, and some research indicates the source of caloric intake is irrelevant to weight gain, according to Jequier dietary fat appears to play several roles in the development and maintenance of obesity. First, it is rich in Calories—more than double the amount of Calories per gram as compared to carbohydrate and protein. In a recent study, Rolls and Bell found that when 462

REAM

individuals were fed diets varying in caloric density (fat content) and could eat as much as they liked, they ate the same amount of food by weight, so the caloric intake varied directly with the caloric density of the food. Second, dietary fat is appetizing and does not appear to rapidly suppress the appetite, leading to a greater intake of Calories as suggested by Blundell and Green. Third, dietary fat has a lower TEF, or higher metabolic efficiency, than carbohydrate and protein. Melby and Hill indicated that dietary fat appears to be stored as fat more efficiently than either carbohydrate or protein, even if the caloric intake is similar; this is especially true in individuals who have lost weight and may be one of the most important reasons why they regain weight so readily. Fourth, dietary fat may also be stored preferentially in the abdominal region, which may increase health risks. In a recent major 7-year study of over 48,000 women, Howard and others reported that weight loss was greatest among women who decreased their percentage of energy intake from fat. To reduce the amount of fat in your diet, you may wish to count the total grams of fat you eat each day. As mentioned previously, a general recommendation is to keep your daily total fat intake to 30 percent or less of your total caloric intake. To calculate the total grams of fat you may eat per day, simply multiply your caloric intake by 30 percent and divide by 9 (the Calories per gram of fat). You may wish to get the fat content to a lower percentage, such as 20 percent. Table 11.7 presents the formula and some calculations for different caloric intake levels and percentages of dietary fat intake.

C H A P T E R 1 1 Weight Maintenance and Loss through Proper Nutrition and Exercise

TABLE 11.7

flexibility with diet planning. However, Miller and Groziak noted that although fat substitutes may help decrease dietary fat intake and percentage of caloric intake from fat, many individuals will compensate by increasing their consumption of other macronutrients, primarily carbohydrate. Research by Shide and Rolls supports this point, indicating individuals eat more food at a given meal if they know some of the meal consists of low-fat items. Additionally, fat-free does not mean Calorie-free, and Manore indicated that some fat-free foods may have similar amounts of Calories as the original. Again, check the food label. Cotton and others suggest you gradually blend fat substitutes into your diet; making many changes at one time may lead to overconsumption of other foods, and hence your overall caloric intake may remain the same, or even increase. Fat substitutes can be part of an overall healthful diet for weight loss, provided you do not compensate for the saved Calories by ingesting other Calorie-rich foods. Remember that you need some fat in your diet for essential fatty acids and fat-soluble vitamins, which you may be able to obtain in a diet containing 10 percent fat Calories. An example of grams of fat and Calories saved by using fat substitutes for a luncheon meal is presented in table 11.8. In this example, using fat substitutes reduced the energy density of the lunch by about 350 Calories. Several modified fats have been proposed to facilitate weight loss. Diglycerides are components of a new oil to replace the traditional triglycerides. Although the caloric content of the two oils is the same, diglycerides are theorized to increase fat oxidation and not be stored as body fat as readily as triglycerides. However, research with this new oil is limited and health professionals currently recommend that its potential minor effects on weight loss do not justify its price; they recommend olive or canola oils, while limiting intake of other fats and oils. Another modified fat, conjugated linoleic acid (CLA), is theorized to inhibit the ability of fat cells to accrue fat or to promote its removal from fat cells. A recent meta-analysis by Whigham and others concluded that CLA supplementation

Calculation of daily fat intake in grams

To use this table, determine the number of Calories per day in your diet and the percent of dietary Calories you want from fat, and then find the grams of fat you may consume daily. For example, if your diet contains 2,200 Calories and you desire to consume only 20 percent of your daily Calories as fat, then you could consume 49 grams of fat. The formula is: % fat x Daily Calories ÷ 9 Calories per fat gram = Daily fat grams [0.20 × 2,200 ÷ 9 = 49] 30% fat Calories (maximal grams)

20% fat Calories (maximal grams)

10% fat Calories (maximal grams)

1,000

33

22

11

1,200

40

26

13

1,500

50

33

16

1,800

60

40

20

2,000

66

44

22

2,200

73

49

24

2,500

83

55

28

Daily caloric intake

The recent development of fat substitutes may be helpful in reducing fat intake. Many fat-free products are currently available and may decrease total fat and caloric intake if used judiciously within a healthful diet. The American Dietetic Association, in their position statement on fat replacers authored by Mattes, indicated that they can be used effectively to reduce fat and Calorie intake. The American Heart Association also recently noted that use of fat substitutes may be associated with reduced fat and Calorie intake compared with nonuse of any fat-modified products, and also noted that when used appropriately, fat substitutes may provide some

TABLE 11.8 Using foods with fat substitutes may help reduce Calories and fat from meals. In this example, the fat-substitute lunch contains about 350 fewer Calories and 40 fewer grams of fat. Regular lunch

Calories/fat grams

Fat-substitute lunch

Calories/fat grams

Sandwich 2 slices whole wheat bread 2 oz bologna

140/2 180/16

Sandwich 2 slices whole wheat bread 2 oz fat-free bologna

140/2 44/0.35

1 oz cheese

85/6.4

1 oz fat-free cheese

43/0

2 tbsp mayonnaise

114/10

2 tbsp fat-free mayonnaise

26/1.0

Banana, medium

105/0.4

Banana

105/0.4

1 cup ice cream

265/14

1 cup fat/sugar-free ice cream

182/0

Totals

889/43.8

Totals

540/3.75

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may produce a modest loss of body fat in humans, about 0.1 pound per week. However, experts currently indicate the benefits of CLA are questionable and the Consumers Union indicates some risks have been identified, and thus do not advise taking CLA until additional research clarifies these issues. Other suggestions for reducing dietary fat are included in the following guidelines, but you may wish to review chapter 5 for additional information. Once individuals adapt to a low-fat diet, they may prefer it because high-fat meals are digested more slowly, possibly leading to indigestion and some gastrointestinal distress. 5. Eat fewer and smaller amounts of refined sugar. This may be accomplished by restricting the amount of sugar added directly to foods and limiting the consumption of highly processed foods that may add substantial amounts of sweeteners. Artificial sweeteners may be helpful. For example, Raben and others found that overweight individuals who consumed large amounts of sucrose in their daily diets, mostly as beverages, had increased energy intake, body weight, and fat mass after 10 weeks, but these effects were not seen in a similar group that consumed artificial sweeteners. Pi-Sunyer noted that substitution of artificial sweeteners, such as aspartame, for sugar has been shown to reduce caloric intake without leading to an increased consumption of other foods. Drewnowski also reported that some short-term studies and one long-term study have shown that artificial sweeteners could decrease caloric intake and increase weight loss, but more long-term research is recommended. Again, like fat substitutes, sugar substitutes may be an effective part of a healthful weight-loss diet, but individuals must be cautious not to compensate and eat more food later. 6. Reduce the intake of both fat and sugar. In many cases, simply reducing the fat and sugar content in the diet will save substantial numbers of Calories and may be all that is needed. Did you know that fat and sugar together account for nearly 50 percent of the Calories in the average American diet? That represents 5 out of every 10 Calories. Table 11.9 provides some examples of how to save Calories via simple substitutions for comparable foods containing fat or sugar. We often unwittingly consume high-fat, high-sugar items when we dine out. Did you know that some appetizers may contain several thousand Calories? For example, a fried whole onion with dipping sauce contains about 2,100 Calories. Even supposedly healthy fast foods, such as salads, can contain as much fat and Calories as the burgers on the menu, mainly because large amounts of fat are added with the dressing; one popular salad contains over 800 Calories, with over 70 percent fat Calories. Ask your waiter if a list of restaurant items with nutritional values, including Calories, is available either at the restaurant or on the Internet. Most national chains provide such information. 7. Eat more low-fat dairy products. As noted previously, increased protein intake may help suppress the appetite more so than equivalent amounts of carbohydrate or fat. In chapter 8 we discussed the hypothesis that a dairy-rich diet could promote weight loss but as noted, in general, research findings do not support this hypothesis. Nevertheless, milk exchange products are excellent sources of high-quality protein and other 464

TABLE 11.9

Simple food substitutions to save Calories To save this many Calories

Instead of

Select

1 croissant

1 whole wheat bagel

80

1 whole egg

2 egg whites

50

1 ounce cheddar cheese

1 ounce mozzarella (skim)

30

1 ounce regular bacon

1 ounce Canadian bacon

100

3 ounces tuna in oil

3 ounces tuna in water

60

Cream of mushroom soup

Black bean soup

90

1 cup regular ice cream

1 cup fat-free frozen dessert

150

1 ounce turkey bologna

1 ounce turkey breast

1 McDonald’s Big Mac

1 McDonald’s grilled chicken

120

1 cup whole milk

1 cup skim milk

60

French fried potatoes

Baked potato

1 ounce potato chips

1 ounce pretzels

90

1 tablespoon mayonnaise

1 tablespoon fat-free mayonnaise

90

1 can regular cola

1 can diet cola

50

100

150

essential vitamins and minerals. The key is to select the healthier, low-fat versions, which are healthier protein foods. Use skim milk, low-fat cottage cheese, low-fat yogurt, and nonfat dried milk instead of their high-fat counterparts like whole milk, sour cream, and powdered creamers. 8. Eat more low-fat meat and meat substitutes. The meat and meat substitute exchange products also are sources of high-quality protein and many other nutrients but also may contain excessive fat Calories. To eat healthier proteins, select very-lean and lean meat exchanges, including meat substitutes such as legumes. Per one ounce serving, very-lean meat and meat substitutes contain only 35 Calories and less than 1 gram of fat. Examples include the white meat of chicken and turkey, 99 percent fat-free ground turkey, tuna fresh or canned in water, shrimp, fat-free cheese, egg whites, and egg substitutes. See appendix E for other sources. If you enjoy beef and pork, use leaner cuts such as beef eye of round, flank steak, pork tenderloin, and 96 percent fat-free hamburger. Trim away excess fat; broil or bake your meats to let the fat drip away. If you eat in fast-food restaurants,

C H A P T E R 1 1 Weight Maintenance and Loss through Proper Nutrition and Exercise

9.

10.

11.

12.

13.

select foods that are low in fat, such as grilled chicken, lean meats, and salads. Avoid the high-fat foods, which normally contain 40–60 percent fat Calories. Also be aware that serving sizes have increased dramatically in recent years. That large hamburger deluxe may have triple or more the Calories of a regular hamburger. Select legumes as an excellent meat substitute. Eat more whole, unprocessed carbohydrates. The starch exchange contains healthy carbohydrates and is high in vitamins, minerals, and fiber. Eating a low-glycemic, high-fiber diet increases the gastric volume, which might help suppress appetite. Use whole-grain breads and cereals, brown rice, oatmeal, beans, bran products, and starchy vegetables for dietary fiber. Limit the use of processed grain products that add fat and sugar. Substitute products low in fat, such as standardsize whole wheat bagels, for those high in fat, like croissants. Eat more fruits. Foods in the fruit exchange are high in vitamins and fiber. Select fresh, whole fruits or those canned or frozen in their own juices. Avoid those in heavy sugar syrups. Limit the intake of dried fruits, which are high in Calories. Eat at least one citrus fruit daily. Limit intake of fruit juices, which are rich in Calories. Eat more veggies. The vegetable exchange foods are low in Calories yet high in vitamins, minerals, and fiber. Select dark-green leafy and yellow-orange vegetables daily. Low-Calorie items like carrots, radishes, and celery are highly nutritious snacks for munching. Many of these vegetables are listed as free exchanges in appendix E because they contain fewer than 20 Calories per serving. Fruits and vegetables may provide bulk to the diet and a sensation of fullness without excessive amounts of Calories. Consume fewer high-Calorie fat exchanges. Use smaller amounts of high-Calorie fat exchanges. Many salad dressings, butter, margarine, and cooking oils are pure fat. If necessary, substitute low-Calorie or fat-free dietary versions instead. Fat-free mayonnaise tastes good and has 90 fewer Calories than a serving of regular mayonnaise. Do not prepare foods in fats, such as with frying. Use nonstick cooking utensils or nonfat cooking sprays. Reduce liquid Calories. Beverages other than milk and juices should have no Calories. High-Calorie liquids, such as sodas and alcoholic beverages, may be especially harmful in weightloss programs because they not only add Calories to the diet but they also do not appear to suppress the appetite as well as similar amounts of Calories in solid foods. In a recent review of 30 high-quality studies, Malik and others found that the weight of epidemiologic and experimental evidence indicates that a greater consumption of sugar-sweetened beverages is associated with weight gain and obesity, and that sufficient evidence exists for public health strategies to discourage consumption of sugary drinks as part of a healthy lifestyle. Popkin suggests that about half of the daily Calories that contribute to weight gain are consumed as sugary beverages. Other beverages may also contain excess Calories. For example, the Consumers Union notes a 24-ounce Starbucks Vanilla Bean Frappuccino (without whipped cream) contains about as many Calories as a McDonald’s Big Mac. However, fluid intake should remain high, for it helps create a sensation of satiety during a meal. Concerned with the increase in obesity in the United States, Popkin assembled a

14.

15.

16.

17.

Beverage Guidance Panel to provide guidance on the relative health and nutritional benefits and risks of various beverage categories. Plain drinking water was ranked as the preferred beverage to fulfill daily water needs while calorically sweetened, nutrient-poor beverages were ranked as least preferred. The panel recommends that the consumption of beverages with no or few calories should take precedence over the consumption of beverages with more Calories. Limit your intake of alcohol. It is high in Calories and zero in nutrient value. One gram of alcohol is equal to 7 Calories, almost twice the value of protein and carbohydrate. For 100 Calories in a shot of gin you receive zero nutrient value, but for the same amount of Calories in approximately 2 ounces of chicken breast you get nearly one-third of your RDA in protein plus substantial amounts of iron, zinc, niacin, and other vitamins. Research indicates that consuming alcohol with a meal does not substitute for other foods, so the total caloric intake of the meal is increased. Additionally, excess alcohol Calories are stored as body fat. If you desire alcohol, select the light varieties of wine and beer. Substitution of a light beer for a regular beer will save about 50 Calories. You may wish to try the nonalcoholic wines and beers, which may contain even fewer Calories. Additional information is presented in chapter 13. Limit salt intake. Salt intake should be limited to that which occurs naturally in foods. Try to use dry herbs, spices, and other nonsalt seasonings as substitutes to flavor your food. Salt may increase the appetite or thirst for Calorie-containing beverages. Eat slowly. Slowing down the process of eating, by taking time to smell the aromas from your food and chewing slowly, will provide time to help curb your appetite. The Consumers Union notes that it takes about 20–25 minutes for your brain to receive signals from your stomach and intestines that you are satisfied. Eat a salad or soup as an appetizer, which may help curb your appetite for the main course. Nibble, don’t gorge. Instead of gorging on two or three large meals a day, eat five or six smaller ones. Although Bellisle and others reported no difference between gorging and nibbling on daily energy expenditure, they indicated that any effects of nibbling on the regulation of body weight are likely to be mediated through effects on food intake. Use low-Calorie, nutrient-dense foods for snacks. Research has shown that nibbling may help control sensations of hunger between meals by helping maintain normal blood glucose levels, Nibbling may help in other ways, possibly by minimizing the release of insulin, which assists in the storage of fat in the body. The following are examples of small snacks, less than 100 Calories each, that may help kill your appetite: • • • • •

an apple a hard-boiled egg a dozen almonds 3 Hershey’s kisses 3 cups of air-popped, fat-free popcorn

18. Eat breakfast. About 80 percent of individuals in the National Weight Control Registry eat breakfast. A hearty breakfast may help curb hunger throughout the morning hours. One study has shown that when more Calories were eaten in the morning, www.mhhe.com/williams9

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Foods selected

Total Calories

Meal

Calories per serving

Calories: ______________________________________ Number of servings

caloric intake for the entire day was less as compared to eating most daily Calories in the evening; researchers suggested the appetite may be suppressed easier in the morning than in the evening. In this regard, a high-protein breakfast may be important. Vander Wal and others found that eating eggs for breakfast can curb appetite at lunch and for the remainder of the day, reducing total daily intake by about 250 fewer Calories. Egg substitutes (egg whites) may be used as can other high-protein, high-fiber breakfasts, such as whole-grain cereals with skim milk or whole wheat toast with smoked salmon. 19. Learn to cook! Microwaves and electric grills make cooking easy. Microwave cooking needs no fat for preparation, while electric grilling helps remove fat from meats. Cook and serve small portions of food for meals. The temptation to overeat may be removed. 20. Learn low-Calorie foods. Learn what foods are low in Calories in each of the six food exchanges and incorporate those palatable to you in your diet. Learn to substitute low-Calorie foods for high-Calorie ones. The key to a lifelong weight-maintenance diet is your knowledge of sound nutritional principles and the application of this knowledge to the design of your personal diet. Knowledge, however, is not the total answer; your behavior should reflect your knowledge. You may know that whole milk contains about 60 more Calories per glass than skim milk, but if you cannot switch then the advantage of your knowledge is lost in this instance. Sometimes making changes in small steps helps, such as first switching from whole to low-fat milk, and then to skim milk. Appendix H contains many Small Steps that may help facilitate various healthful dietary transitions.

Breakfast Milk, skim Meat, very lean Fruit Vegetable Starch Fat Beverage

90 35 60 25 80 45 0

Lunch Milk, skim Meat, very lean Fruit Vegetable Salad Starch Fat Beverage

90 35 60 25 20 80 45 0

Dinner

How can I plan a nutritionally balanced, low-Calorie diet? The key to a sound diet for weight loss is nutrient density, or the selection of low-Calorie, high-nutrient foods. The twenty points addressed in the previous section represent important guidelines to implement such a diet. Table 11.10 presents a suggested meal pattern based upon the Food Exchange System. The foods should be selected from the food exchange lists found in appendix E. You may use the form shown in the next column as a guide. The total caloric values are close approximations for a three-meal pattern. If you decide to include snacks in your diet, such as a fruit or vegetable, then remove each snack from one of the main meals. The salads should contain vegetables with negligible Calories, such as lettuce and radishes. Note that under the exchange system, starchy vegetables such as potatoes are included in the starch group because their caloric content is similar. The beverages, other than milk and fruit juice, should contain no Calories. Although you may drink as many noncaloric beverages as you wish over the course of the day, drinking at least one at each meal will help provide a feeling of satiation and may help suppress the appetite somewhat. Although only seven levels of caloric intake are presented in table 11.10, you may adjust it according to your needs by simply adding or subtracting appropriate food exchanges. For example, if you wanted a 1,700-Calorie diet, you could subtract one starch exchange and one-half fat exchange (about 100 Calories) from the 1,800-Calorie diet. 466

Milk, skim Meat, very lean Fruit Vegetable Salad Starch Fat Beverage

90 35 60 25 20 80 45 0

After you have determined the number of Calories you need daily, select the appropriate diet plan from table 11.10. To help implement your diet plan and to keep day-to-day track of the food exchanges you eat, you should design a 3″ × 5″ card similar to the model below for the number of food exchanges in your daily diet. As you consume an exchange at each meal, simply cross it off on the card. Make a new card for each day. The model shown is for 1,500 Calories. The total exchanges are summed from table 11.10. Daily meal plan Milk exchange, skim Meat exchange, very lean Starch exchange Vegetable exchange Salads Fruit exchange Fat exchange Beverages

C H A P T E R 1 1 Weight Maintenance and Loss through Proper Nutrition and Exercise

1,500 Calories (2) 1 2 (7) 1 2 3 4 5 6 7 (6) 1 2 3 4 5 6 7 (3) 1 2 3 4 (2) 1 2 (4) 1 2 3 4 (2) 1 2 3 (3) 1 2 3

TABLE 11.10

Suggested daily meal pattern based on the Food Exchange System Approximate daily caloric intake 1,500 1,800 2,000

1,000

1,200

2,200

2,500

1 1 1 1 0 1

1 1 2 1 0 1

1 2 2 1 1 1

1 2 3 1 1 1

1 2 3 2 1 1

1 3 3 2 2 1

1 3 3 2 2 1

1 2 2 1 1 1 1 ⁄2 1

1 2 2 1 1 2 1 ⁄2 1

1 2 2 2 1 2 1 1

1 3 2 2 1 2 2 1

1 3 2 2 1 2 2 1

1 3 3 2 1 2 2 1

2 4 3 2 1 2 2 1

0 2 2 1 1 0 1 ⁄2 1

0 2 2 2 1 0 1 1

0 3 3 2 1 1 1 1

1 3 3 2 1 2 1 1

1 3 4 2 1 2 2 1

1 4 4 2 1 2 2 1

1 4 5 3 1 3 2 1

2 5 5 2 2 2 1 3

2 5 6 3 2 3 2 3

2 7 7 4 2 4 3 3

3 8 8 4 2 5 4 3

3 8 9 4 2 6 5 3

3 10 10 4 2 6 6 3

4 11 11 5 2 7 6 3

Breakfast Milk, skim Meat, very lean Starch Fruit Fat Beverage Lunch Milk, skim Meat, very lean Starch Vegetable Salad Fruit Fat Beverage Dinner Milk, skim Meat, very lean Starch Vegetable Salad Fruit Fat Beverage Totals Milk, skim Meat, very lean Starch Vegetable Salad Fruit Fat Beverage

Key points 1. Caloric values: Milk exchange, skim = 90 Meat exchange, very lean = 35 Fruit exchange = 60 Vegetable exchange = 25 Starch exchange = 80 Fat exchange = 45 Beverage = 0 Salad = 20 2. See appendix E for a listing of foods in each exchange. Note the following: a. Foods other than milk, such as yogurt, are included in the milk exchange. b. The meat list includes foods such as eggs, cheese, fish, and poultry; low-fat legumes, like beans and peas, may be considered as meat substitutes. c. Some starchy vegetables are included in the bread list. 3. Foods should not be fried or prepared in fat unless you count the added fat as a fat exchange. Broil or bake foods instead. 4. Low-Calorie vegetables like lettuce and radishes should be used in the salads. Use only small amounts of very-low-Calorie salad dressing. 5. Beverages should contain no Calories.

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Keep in mind that this is not a rigid diet plan. At a minimum you should have 2 skim milk exchanges, 5 very lean meat exchanges, 5 starch exchanges, 2–3 vegetable exchanges, and 2–3 fruit exchanges. Once you have guaranteed these minimum requirements, you may do some substitution between the various exchanges so long as you keep the total caloric content within range of your goals. For example, you may delete 2 starch exchanges (160 Calories) in the model and substitute 1 skim milk and 2 very lean meat exchanges (160 Calories). You may also shift a limited number of the exchanges from one meal to another. If you prefer a more substantial breakfast and a lighter lunch, simply shift some of the exchanges from lunch to breakfast. It may be a good idea to take a little time and construct a diet for yourself, using the following guidelines for your calculations. Use the form on page 466. Table 11.11 presents an example of a 1,500-Calorie diet based on the Food Exchange System. 1. Calculate the number of Calories you want per day. See pages 452–453 for guidelines. 2. Use table 11.10 to determine how many servings you need from each food exchange.

TABLE 11.11

3. Multiply the number of servings by the Calories per serving to get the total Calories. Add the total Calories column to get total daily intake. 4. Select appropriate foods from the exchange list in appendix E. One final point: If your diet contains less than 1,600 Calories, it would be wise to take a daily vitamin/mineral supplement with the RDA for all essential vitamins and key minerals. The purpose of planning your own diet plan is to familiarize yourself with the caloric and nutrient content of the majority of foods that constitute your diet. You can plan your diet manually, or with computer-based programs if preferred. For example, the MyPyramid program permits you to develop a personalized diet; an example of a 2,000-Calorie diet is presented in appendix I.

Are very-low-Calorie diets effective and desirable as a means to lose body weight? As noted in chapter 10, very-low-Calorie diets (VLCD) are defined technically as containing less than 800 Calories per day and are often referred to as modified fasts. In some medical

A 1,500-Calorie diet based on the Food Exchange System Number of servings

Calories per exchange

2 1 2 1 1

35 45 80 60 0

70 45 160 60 0

1 ounce very lean ham and 1 ounce low-fat cheese melted on 2 pieces whole-grain toasted bread 4 ounces orange juice 1 cup coffee with noncaloric sweetener

1 1 2 2 1 1 1 1

120 60 35 80 25 20 45 0

120 60 70 160 25 20 45 0

8 ounces plain, low-fat yogurt with cut-up fresh fruit (1/2 banana) 2 ounces turkey breast on whole-grain bun 1 carrot lettuce with low-Calorie dressing diet cola

Milk, skim Meat, very lean Starch Vegetable Salad Fat

1 3 3 3 1 1

90 35 80 25 20 45

90 105 240 75 20 45

Fruit Beverage

2 1

60 0

120 0

1/2 cup ice milk 3 ounces broiled fish 1 baked potato and 1 slice whole wheat bread 1 1/2 cups steamed broccoli and cauliflower cucumbers small amount of margarine for potato and low-Calorie dressing for salad 1 banana cut up on ice milk iced tea

Exchange

Total calories

Foods selected

Breakfast Meat, very lean Fat Starch Fruit Beverage Lunch Milk, low-fat Fruit Meat, very lean Starch Vegetable Salad Fat Beverage Dinner

TOTAL

468

1,530

C H A P T E R 1 1 Weight Maintenance and Loss through Proper Nutrition and Exercise

institutions, total fasting programs are used. Under proper medical supervision, such diets are generally regarded as safe and have been effective in inducing rapid weight losses in very obese patients. However, VLCD are not recommended for the individual who wants to lose 10–20 pounds or for the individual who is not under medical supervision, not only because of the possible adverse health consequences as noted in chapter 10, but also because VLCD may be counterproductive to the ultimate goal of long-term weight loss. They do not satisfy the criteria for a recommended weight-loss program for individuals who are not medically supervised and they often lead to weight cycling. It is recommended that any individual contemplating the use of VLCD should consult a physician and a dietitian.

Is it harmful to overeat occasionally? Most of us occasionally overindulge in food, particularly on holidays and other festive occasions or when we dine at all-you-caneat restaurants. Eating is a pleasurable activity, and an occasional pig-out is not harmful, as long as it does not become a habit. As noted in chapter 5, try to avoid high-fat meals if you are prone to cardiovascular disease because such meals may increase the risk of heart attacks. After a very large meal, you may step on the scale the next day and find that you have gained 5 pounds or more. Not to worry. Most of that weight is water, which may be bound to the increased carbohydrate (glycogen stores) in your body. Additionally, if the meal was high in sodium, your extracellular water stores will also increase. Going back to your regular diet and exercise program will reduce these water stores in a day or so, and your body weight will return to normal. It is important to recognize that occasional overeating may be a lapse in your diet and that you treat it as such. Renew your commitment to your weight-loss plan and prevent the occasional lapse from becoming a relapse.

Ke y C o n c e p t s 䉴 Rapid loss of body weight, which may occur during the early

stages of dieting, is due primarily to body-water changes. The rate at which weight loss occurs will slow down as your body weight decreases, for then body-fat stores are the prime source of weight loss and necessitate a greater caloric deficit. 䉴 Numerous weight-loss diet plans are available, including low-fat diets, low-carbohydrate diets, and high-protein diets. All may be effective and safe if the daily caloric energy intake is less than the daily caloric energy expenditure. The DASH and OmniHeart diets may be highly recommended for weight control. 䉴 Counting Calories and grams of fat may be a useful technique during the early stages of a diet, for the more knowledge you have about the caloric and nutrient content of foods, the better equipped you are to make wise selections. 䉴 The key principle of dieting is to select from among the six food exchanges low-Calorie, high-nutrient foods that appeal to your taste and are easily incorporated into your daily lifestyle.

䉴 Very-low-Calorie diets (VLCD) may be effective for weight loss

under strict medical supervision but are not recommended for the average individual trying to lose some excess fat.

C h e c k f o r Yo u r s e l f Using the Food Exchange System, plan a balanced, healthy diet of 1,600 Calories for an individual who needs to consume this much to lose excess body fat.

Exercise Programs What role does exercise play in weight reduction and weight maintenance? Humans are meticulously designed for physical activity, and yet our modern mechanical age has eliminated many of the opportunities that our ancient ancestors had to incorporate moderate physical activity as a natural part of daily living. The regulation of our food intake has not adapted to the highly mechanized conditions in today’s society. As discussed in chapter 10, physical inactivity may be one of the major contributing factors to the development and maintenance of obesity. For example, a sedentary lifestyle, principally TV watching, has been significantly associated with obesity in adolescents and adults. In a study of identical and fraternal twins, Samaras and others found that the physically active twin had significantly less fat than the physically inactive twin. After controlling for genetic and environmental factors, the influence of physical activity on body fat was greater than the other environmental factors, including dietary intake. Indeed, the late Dr. Jean Mayer, an international authority on weight control, reported that no single factor is more frequently responsible for obesity than lack of physical exercise. There are basically two ways you can become more physically active and increase your total daily energy expenditure. First, decrease the amount of time that you are physically inactive, particularly time watching television. Robinson noted that most studies support the suggestion that reducing television viewing may help to reduce the risk for obesity or help promote weight loss in obese children. The same thinking applies to adults as well. In general, you want to increase your level of nonexercise activity themogenesis (NEAT). Keep moving throughout the day; walk rather than ride, don’t sit when you can stand, and keep moving, or fidget, when you have to sit. In one study, researchers followed lean and mildly obese people for 10 days, and found that the obese subjects remained seated for about 2.5 hours longer per day than the lean individuals, suggesting this could result in more than 300 fewer Calories expended daily. Second, start a planned exercise program, which is the main focus of this section. As discussed in the following text, important considerations include the type and amount of exercise, but a considerable amount of knowledge substantiates the point that exercise can help reduce and control body weight and should be www.mhhe.com/williams9

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included in a weight-loss or maintenance program. Indeed the Consumers Union recently noted that to slim down permanently, you need to make a lifelong commitment to regular exercise, including not only aerobic exercise to burn Calories, but strength (resistance) training to build or at least preserve muscle. In addition to the physiological effects upon energy expenditure, Miller notes that exercise consistently shows beneficial effects in medical, psychological, and behavioral outcomes.

Aerobic Exercise Exercise burns Calories (figure 11.6). The primary function of aerobic exercise in a weight-control program is simply to increase the level of energy expenditure and help tip the caloric equation so that energy output is greater than energy input. As mentioned in chapter 3, the metabolic rate may be increased tremendously during aerobic exercise. For example, while the average person may expend only 60–70 Calories per hour during rest, this value may approach 1,000 Calories per hour during a sustained high-level activity such as rapid walking, running, swimming, or bicycling. Athletes involved in extreme endurance events, such as the Tour de France, and ultradistance runners, such as Yannis Kouros, have been reported to consume between 6,000 and 13,000 Calories per day. If you are overweight, the same amount of aerobic weightbearing exercise will cost you more Calories than your leaner counterpart. Because you have more weight to move, you will expend more energy and lose more body fat in the long run. For example, the energy cost of jogging 1 mile would be about 70 Calories for the 100-pound individual and about 140 Calories for someone twice that weight. Figure 11.7 depicts this concept graphically for one type of exercise—walking. 470

F I G U R E 1 1 . 6 Exercise can be an effective means of increasing energy expenditure and losing excess Calories. 7 6 Energy expenditure, Cal/min.

Resistance Exercise Training Resistance-training, or weighttraining, programs are detailed in the next chapter in relation to gaining body weight as muscle mass, but such programs may also be very helpful during weight-loss programs. One possibility, as suggested by the American College of Sports Medicine, is that increased strength through resistance training may lead to a more active lifestyle in sedentary overweight and obese individuals, thus leading to health benefits that may include weight loss and prevention of weight regain. Another possibility is maintenance of REE during weight loss. Poehlman and Melby noted that although resistance training may increase the metabolic rate during exercise, its effects on regulation of body weight appear to be mediated primarily by its effects on body composition rather than by the direct energy costs of the resistance exercise. Indeed, research by Bryner and his associates has revealed that resistance training may help preserve lean body mass and maintain normal REE during weight loss, even on a very-low-Calorie diet of 800 Calories. Recall that protein tissue, primarily muscle, may be lost along with body fat during a weight-reduction program. However, resistance training may stimulate muscular development and help prevent significant decreases in lean body mass. Such an effect may also help prevent decreases in the REE. Additionally, as is noted in the next chapter, the typical resistance-training workout does not burn many Calories, mainly because of frequent recovery periods; however, dynamic circuit-type resistance-training programs may also be used to burn additional Calories.

5

Gross body weight 200 lbs.

4 3 2 Gross body weight 100 lbs.

1 0 0

1

2 3 Speed, mph

4

5

F I G U R E 1 1 . 7 Effect of speed (mph) and gross body weight (lbs) on energy expenditure (Calories/minute) of walking. The heavier the individual, the greater the expenditure of Calories for any given speed of walking. The same would be true for running and other physical activities in which the body must be moved by foot. From Textbook of Work Physiology by P. O. Astrand and K. Rodahl. Copyright © 1977 McGrawHill Book Company. Used with the permission of McGraw-Hill Book Company.

One major misconception may deter many individuals from initiating an exercise program for weight control. They believe that exercise is a poor means to lose body weight because it

C H A P T E R 1 1 Weight Maintenance and Loss through Proper Nutrition and Exercise

expends so few Calories. For example, they have heard that you have to jog about 35 miles to lose a pound of body fat. Because the average-sized male uses approximately 100 Calories per mile of jogging, and because 1 pound of body fat contains about 3,500 Calories, there is some truth to that statement. However, you must look at the long-haul concept of weight control (figure 11.8). Jogging about 2 miles a day will expend about 6,000 Calories in a month, accounting for almost 2 pounds of body fat. Over 6 to 8 months or longer, the weight loss may be substantial provided the individual does not compensate by consuming more Calories. In addition to the direct efffect of increased energy output during exercise, exercise has been theorized to facilitate weight loss by other means. As noted in chapter 3, aerobic exercise may increase the REE during the period immediately following the exercise bout and may also increase the thermic effect of food (TEF) if you exercise after eating a meal. Unfortunately, the magnitude of this increased REE or TEF is relatively minor and not considered to be of any practical importance in a weight-loss program. Related to the TEF, it does not matter if you exercise before or after a light meal, although as noted in the following text, exercise before a meal may help curb the appetite. However, like resistance exercise, aerobic exercise may have a beneficial effect on the REE, but to a lesser degree. Although aerobic exercise will not totally prevent the decrease in the REE

normally seen with weight loss, particularly with large weight losses, some studies suggest that it may help minimize the decrease, thereby helping maintain energy expenditure near normal levels during rest. However, not all research supports this finding. The interested reader is referred to the review by Hill and others. Moreover, during aerobic exercise, the body mobilizes its fat cells to supply energy to the muscle cells. Hence, body-fat stores are reduced. In the long run, this change in body composition may actually favor a slight increase in the REE because muscle tissue is more active metabolically than fat tissue. Recall that in dieting alone, some lean muscle mass may be lost. In a study comparing the effects of either dieting or exercise on loss of body fat and lean tissue, Pritchard and others reported that 40 percent of the weight loss in dieters was lean tissue, while exercisers lost only 20 percent lean tissue, because most of their weight loss was fat. It should be noted that some research suggests aerobic exercise may decrease the REE in individuals who are already lean, suggesting that the body is attempting to preserve its energy reserves. This may be particularly true among elite endurance athletes, as noted by Sjodin and others. Although this does not appear to be of any concern to overweight individuals who desire to lose weight, it may pose a problem to the lean athlete attempting to shed a few additional pounds for competition.

35 miles

2 miles

F I G U R E 1 1 . 8 To lose body fat by exercising, you must look at the long-haul concept of weight control. The average-weight individual needs to jog about 35 miles to burn off 1 pound of body fat. This would be nearly impossible for most of us to do in 1 day. At 2 miles per day, however, it could be done in about 2 1⁄2 weeks—and at 5 miles per day, in only 1 week. Even though it takes time, an exercise program is a very effective approach to reducing excess body fat.

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In addition to the physiological effects upon energy expenditure, exercise may also confer significant psychological and medical benefits, even without any weight loss. As the fitness level and body composition improve, the individual may experience improvements in mood, energy levels, body image, and self-esteem. Exercise may also be the psychological catalyst that helps individuals to improve their nutritional habits and other health-related behaviors. Aerobic exercise may render other significant health benefits. For example, as documented in the Surgeon General’s Report on Physical Activity and Health, exercise, as a form of physical activity, is becoming increasingly important as a means to help prevent, and even treat, many chronic diseases, such as cardiovascular disease, diabetes, and osteoporosis. In their review of 20 studies, Kay and Fiatarone Singh indicated that the available evidence suggests a beneficial influence of physical activity on reduction in abdominal and visceral fat in overweight and obese subjects, which may help reduce symptoms associated with the metabolic syndrome. Many of the health benefits of exercise are related to weight loss and were discussed in chapters 1 and 10. For a detailed review, the interested reader is referred to the American College of Sports Medicine Roundtable on Physical Activity in the Prevention and Treatment of Obesity and its Comorbidities chaired by Claude Bouchard and Steven Blair. For individuals with normal body weight, exercise is highly recommended for its preventive role, not only to prevent weight gain in the first place, but also to prevent weight regain in those who have lost weight and are on a weight-maintenance program. It is generally recognized that prevention of obesity or excess body weight is more effective than treatment. Epstein and others noted that exercise is an important adjunctive treatment for childhood and adolescent obesity, but indicated it may be of even greater benefit in the prevention of obesity. Moreover, the National Research Council noted that the long-term well-being of our children may depend on increased physical activity. Most people do not become overweight overnight, but rather accumulate an extra 75–150 Calories per day, which over time will lead to excessive fat tissue. A daily exercise program could easily counteract the effect of these additional Calories and is a key component of a weight-maintenance program. Jakicic and Gallagher recently noted that although exercise may have a modest impact on initial short-term weight loss, it may have its greatest effect on long-term weight loss and prevention of weight regain. Catenacci and Wyatt also emphasize the essential role for physical activity in weightloss maintenance. For those who like to eat but not gain weight, exercise is the intelligent alternative.

Does exercise affect the appetite? Short-term effects On a short-term basis, exercise appears to depress the appetite. Martins and others found that an acute bout of exercise (cycling for 1 hour) temporarily decreased hunger sensations and produced a short-term negative energy balance. In their review, Elder and Roberts concluded that the loss of body fat associated with exercise may be mediated by the spontaneous reduction in hunger associated with the exercise task. 472

The intensity of the exercise may be an important consideration. Intense exercise may be used to curb the appetite on a shortterm basis at an appropriate time. Thompson and others found that low-intensity exercise did not suppress hunger, but high-intensity exercise (68 percent VO2 max) did. Research has related the appetite-suppressing effect of exercise to increased body temperature. The close anatomical relationship of the temperature and hunger centers in the hypothalamus may provide a rationale for the inhibition of the hunger center. Both exercise and the TEF will increase the core temperature of the body, so the body simply may be attempting to protect itself against an excessive rise in core temperature by suppressing the appetite to avoid the TEF. Exercise also will stimulate the secretion of several hormones in the body, notably epinephrine, which may also depress the appetite by affecting the hypothalamus or by increasing serum levels of both glucose and free fatty acids. If you exercise before a meal, your food intake may be reduced considerably. Try it and see if it works for you. If you have the facilities available, a good half-hour of intense exercise may be an effective substitute for a large lunch. You may lose Calories two ways, expending them through exercise and replacing the large lunch with a low-Calorie, nutritious snack. However, in a recent review King and others noted that although intense exercise may be an effective means of suppressing the appetite, the effects are brief. Thus, while intense exercise may help to curb your appetite at lunch, unless you are cautious you may increase your caloric intake above normal at dinner. Long-term Effects On a long-term basis, in general, increased energy expenditure through physical activity is counterbalanced by an increased food intake. The body simply compensates for the increased energy expenditure by consuming more energy. This is one of the major mechanisms whereby normal body weight is controlled in the average individual. However, King and others indicated that there may be substantial individual variability in responses to exercise as a means to weight control. They propose that some individuals will be predisposed to compensatory responses, such as an increased appetite, that will counterbalance the energy expended through exercise. On the other hand, some individuals may not increase food intake and thus will experience weight loss. Along these lines, Donnelly and Smith reported that women generally lose less weight than men in response to exercise, suggesting one reason may be that women may be more likely to exhibit a compensatory increase in energy intake in response to exercise. Therefore, given the interindividual variability in behavioral and metabolic compensatory responses, exercise prescriptions might be more effective if tailored to suit individuals. An important concern for the athletic individual is the fact that the appetite may not normally decrease with a decreased activity level, as recently reported by Stubbs. If you are physically active, but then must curtail your activity because of an injury or some other reason, your appetite may remain elevated above what you need to maintain body weight at your reduced energy levels. Body fat will increase. Hence, you must reduce your food intake to balance the caloric equation or suffer the consequences.

C H A P T E R 1 1 Weight Maintenance and Loss through Proper Nutrition and Exercise

Does exercise affect the set point? As you may recall from chapter 10, the set-point theory suggests each individual possesses an inborn mechanism that attempts to maintain a certain level of energy balance, or body weight, by modifying energy intake or energy expenditure. In simple terms, the settling-point theory, another theory, suggests the set point may be adjusted to a new level. James Hill and Renee Commerford indicated that physical activity has a significant impact on the settling point, or that level of body weight and body fatness at which a steady-state is reached. They suggested that physical activity will increase total energy expenditure and fat oxidation, which can lead to an overall energy imbalance if there is not complete compensation in terms of increased energy intake and fat intake, and possibly decreased spontaneous daily activities. In essence, Hill and Commerford indicated that increased physical activity can help individuals reach fat and energy balances at lower levels of body fatness than would have been achieved with lower levels of physical activity. Body weight and fat should decrease until a new steadystate is achieved. Nevertheless, there may be a limit to lowering the set point. FosterSchubert and others reported that exercise-induced weight loss over one year resulted in an increase in plasma ghrelin, which you may recall stimulates the appetite. Unless the hypothalamus becomes less sensitive to ghrelin, the appetite will be stimulated to help deter additional weight loss.

design your own program once you know a few basic principles about exercise and energy expenditure. However, a personal fitness trainer may be helpful in getting you on the right track during the early stages of an exercise program. Although resistance exercise may play an important role in weight control and is discussed in chapter 12, the best type of exercise program for losing body fat involves aerobic exercises, those that utilize the oxygen energy system (figure 11.9). This type of exercise program is also the one that conveys the most significant health benefits. The key points of an aerobic exercise program are as follows: Mode of Exercise The mode of exercise must involve large muscle groups. The muscles of the legs comprise a good portion of the total body mass, as do the muscles of the arms. Many people do not realize that the major muscles in the chest and back are attached to the upper arm and are actively involved in almost all

What types of exercise programs are most effective for losing body fat? As you are probably well aware, a number of different exercise programs designed to reduce body weight are available. Perusal of the daily newspaper reveals numerous advertisements for weight-reduction programs sponsored by various commercial fitness centers. Weight training with sophisticated equipment, Slimnastics exercises, aerobic dancing, and special exercise apparatus are a few of the approaches often advertised as the best means to lose body fat fast. The truth is that you do not need any special apparatus or any specially designed program. You can

FIGURE 11.9

Aerobic-mode exercises—such as running, bicycling, or swimming—must involve

large muscle groups.

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arm movements. Walking, jogging, hiking, stair climbing, running, in-line skating, and bicycling primarily involve the legs while swimming primarily stresses the arms. The use of hand-held weights in walking incorporates arm action with the legs. Crosscountry skiing, rowing, and rope jumping use both the arms and legs, as does a good aerobic dance routine. These are good largemuscle activities, although there are a host of others. Intensity of Exercise The second factor is the intensity level. The higher the exercise intensity, the more Calories you expend per unit of time, and so the less time you need to burn a given amount of Calories. However, it is important to note that individuals beginning an exercise program should not engage in highintensity training. Low-intensity exercise training is preferred for beginners, who may increase the exercise intensity as they increase their fitness level. Normal walking uses fewer Calories than easy jogging, which uses fewer Calories than fast running. Simply put, it costs you more energy to move your body weight at a faster pace. However, there is an optimal intensity level for each person depending on how long the exercise will last. You can run at a very high intensity for 50 yards, but you certainly could not maintain that same fast pace for 2 miles. Intensity and duration are interrelated, but for burning the most total Calories, duration becomes more important, and the intensity must be adapted for the amount of time you plan to exercise. To get an idea of exercises with high intensity, check appendix B for Calorie cost per minute relative to your body weight. It is a composite table of a wide variety of individual reports in the literature. When using this appendix, keep these points in mind. 1. The figures are approximate and include the resting metabolic rate. Thus, the total cost of the exercise includes not only the energy expended by the exercise itself, but also the amount you would have used anyway during the same period. Suppose you ran for 1 hour and the calculated energy cost was 800 Calories. During that same time at rest you may have expended 75 Calories, so the net cost of the exercise is 725 Calories. 2. The figures in the table are only for the time you are performing the activity. For example, in an hour of basketball, you may exercise strenuously only for 35–40 minutes, as you may take time-outs and may rest during foul shots. In general, record only the amount of time that you are actually moving during the activity. 3. The figures may give you some guidelines to total energy expenditure, but actual caloric costs might vary somewhat according to such factors as skill level, environmental factors (running against the wind or up hills), and so forth. 4. Not all body weights could be listed, but you can approximate by going to the closest weight listed. 5. There may be small differences between men and women, but not enough to make a marked difference in the total caloric value for most exercises. Appendix B or table 3.6 on page 105 may be useful to determine which types of activities may be of the appropriate intensity for your

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weight-control program. Listing those activities with higher caloric expenditure per minute may suggest several that you could blend into your lifestyle. Duration of Exercise Probably the most important factor in total energy expenditure is the duration of the exercise. In swimming, bicycling, running, or walking, distance is the key. For example, running a mile will cost the average-sized individual about 100 Calories. Five miles would approximate 500 Calories. An individual running 1 mile a day would take over 1 month to expend the caloric equivalent of 1 pound of fat, whereas running 5 miles a day would shorten the time span to about 1 week. Thus, if the purpose of the exercise program is to lose weight, the individual should stress the duration concept. In their review, Catenacci and Wyatt reported that subjects lost substantially more weight in studies that prescribed greater amounts of exercise. For example, Tate and others found that over the course of 18 months subjects who were encouraged to expend 2,500 Calories or more weekly lost significantly more weight than those who were encouraged to expend the standard 1,000 Calories weekly. At the end of 30 months, subjects who continued to expend 2,500 Calories or more weekly lost approximately 25 more pounds than those who exercised less. One of the key points about the duration concept is the notion of distance traveled rather than time. For example, tennis and running are both good exercises. However, the runner will expend considerably more Calories in an hour than the tennis player because the activity involved in running is continuous. The tennis player has a number of rest periods in which the energy expenditure is lower. Consequently, at the end of an hour’s activity, the runner may have expended two to three times as many Calories as the tennis player. A similar comparison can be made between runners and walkers. If you cannot find a big block of time, such as 40 minutes, to do your exercise, then try to incorporate more frequent short bouts of exercise throughout the day. Do more exercise snacks. Several studies by Jakicic and Murphy and their associates reported that exercising in multiple short bouts per day, such as four 10-minute bouts, was just as effective as a single 40-minute bout in producing weight loss and improving cardiovascular fitness over a 20-week period. If your day is filled with other activities, try to squeeze in some short exercise bouts such as brisk walking, possibly before breakfast, during morning and afternoon work breaks, and before or after lunch and dinner. Andersen has indicated this strategy may increase adherence to your exercise program, and it may also help your study or work productivity by providing a psychological pick-me-up during the day. A major reason many adults do not use exercise as a weightloss mechanism is that their level of physical fitness is so low they cannot sustain a moderate level of exercise intensity for very long. However, keep in mind that as you continue to train, your body will begin to adapt so that in time you will be able to exercise for longer and longer periods. Additionally, intensity and duration are interrelated, and if balanced, will result in equal weight losses. Melanson and others found that compared to a sedentary day, expending 400 Calories during exercise intensities of 40 and 70 percent of VO2 max

C H A P T E R 1 1 Weight Maintenance and Loss through Proper Nutrition and Exercise

increased 24-hour energy expenditure, but there was no difference attributed to exercise intensity. Grediagin and others also found no significant difference in body-fat losses when women engaged in either high-intensity or low-intensity exercise, provided the total caloric expenditure per exercise session was the same. In both cases it simply took the low-intensity exercise group longer to expend the same amount of Calories. As you improve your fitness level, Hunter recommends incorporating some higher-intensity exercise in your program, not only because it burns Calories more rapidly, but also because it will make your moderate-intensity workouts seem much easier. Additionally, as noted in chapter 1 and later in this chapter, additional health benefits may be associated with higher-intensity exercise. Frequency of Exercise Exercise frequency complements duration and intensity. Frequency of exercise refers to how often each week you participate. As would appear obvious, the more often you exercise, the greater the total weekly caloric expenditure. In general, three to four times per week would be satisfactory, provided duration and intensity were adequate, but six to seven times would just about double your caloric output. A daily exercise program is recommended if weight control is the primary goal. Enjoyment of Exercise An important factor is enjoyment of the exercise. For an activity to be effective in the long run, it should be one that you enjoy, yet one that will help expend Calories because it has a recommended intensity level, can be performed for a long time, or both. For example, you may not enjoy jogging or running, so other activities may be substituted. Fast walking with vigorous arm action, golf (pulling a cart), swimming, bicycling, tennis, handball, racquetball, aerobic dancing, and a variety of other activities may produce a greater feeling of enjoyment and still burn a considerable number of Calories. Even leisure activities and home chores done vigorously such as gardening, yard work, washing the car, and home repairs may be useful in burning Calories and developing fitness. Exercise need not be unpleasant. Enjoy your exercise. Try to make it a lifelong habit by viewing it as play. Next time you vacuum the house or mow the lawn, try to think about it as a good workout rather than work. Practicality of Exercise Practicality is another important factor. You may enjoy swimming, tennis, racquetball, and a variety of other sports, but lack of facilities, poor weather conditions, or high costs may limit your ability to participate. For the active person who travels, this may be a major concern. You probably have noticed by now that an underlying bias toward walking and running exists throughout this book. It is probably because, to me, they satisfy all the previously mentioned criteria necessary for maintaining proper body weight. Moreover, they are very practical activities. All you need is a good pair of shoes and proper clothes for the weather, so nothing short of an injury should deter you from your daily exercise routine. Walking, jogging, or running can be very practical substitutes on those days when you cannot participate in your regular physical activity. Peter Wood, an esteemed researcher at Stanford University, indicated brisk walking is perhaps the best single exercise in regard to energy expenditure, fea-

sibility, and acceptability to a large proportion of the population; for those who are physically unfit, overweight, or elderly, it is probably the best choice of exercise. Some guidelines to an effective walking program are presented later. Indoor exercise equipment is also very practical for a number of reasons. For example, it can be used while watching children, avoiding inclement weather, or doing two things at one time such as reading or watching television news. This is a highly recommended way to watch television. Numerous types of indoor exercise equipment are available, such as bicycling apparatus, cross-country skiing simulators, rowing machines, stair-steppers, and treadmills. All can provide an aerobic workout, but in a recent study Zeni and others reported that the treadmill is the optimal indoor exercise machine for enhancing energy expenditure at a set rating of perceived exertion. Resistance- or strength-training indoor equipment is also available. Consumer Reports magazine offers periodic analyses of various types of indoor exercise equipment. Versatility of Exercise Versatility is also an important factor. Learn and engage in a variety of physical activities, such as running, cycling, swimming, rowing on stationary machines, stair climbing, striding on elliptical trainers, aerobic dancing, and aerobic walking. By cross-training, such as running 3 days per week, cycling 2 days, and swimming 2 days, you are less likely to become bored with exercise or to sustain overuse injuries. Also, if you plan to exercise for an hour daily, one-half hour each of running and cycling, or some other combination of exercises, is also an effective way to cross-train. Moreover, if you become injured and cannot do your favorite type of exercise, you may be able to expend Calories and maintain fitness by using alternative exercises until you heal. For example, if weight-bearing activities such as jogging bother you, do nonweight-bearing activities such as cycling or swimming, or water-jogging wearing a buoyancy vest.

If I am inactive now, should I see a physician before I initiate an exercise program? Various medical groups, such as the American College of Sports Medicine and the American Heart Association, have developed guidelines to determine who should receive a medical exam prior to initiating an exercise program. A thorough review of these guidelines is not presented here because they are extensive and beyond the scope of this text. However, the following points represent a synthesis of these guidelines. 1. Before initiating any exercise program, you should be aware of any personal medical problems that possibly could be aggravated. If you have concern about any facet of your health, check with your physician before starting an exercise program. This is especially important in weight-reduction exercise programs where the main stress is placed on the heart and blood vessels, the cardiovascular system. 2. No matter what your age, if you have any of the coronary heart disease risk factors noted in table 11.12, you should have a medical examination. You may also wish to assess your cardiac risk profile at the American Heart Association’s Website.

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TABLE 11.12 Major and predisposing risk factors

associated with coronary heart disease 1. High blood pressure 2. Cigarette smoking 3. Dyslipidaemia (High LDL-cholesterol; Low HDL-cholesterol) 4. Impaired fasting blood glucose 5. Obesity 6. Family history of coronary heart disease 7. Sedentary lifestyle/physical inactivity Sources: Data from American College of Sports Medicine, ACSM’s Guidelines for Exercise Testing and Prescription, 7th ed., 2005. Note: Normal serum cholesterol or normal blood pressure may still be counted as a risk factor if medications are taken for its control.

3. If you are young (twenties or early thirties), healthy, and have no risk factors, it is probably safe to initiate an exercise program. 4. The older you are, the better the idea to get a medical examination. In fact, it is prudent for those over forty to have an examination. www.amhrt.org To determine your cardiac risk profile at the American Heart Association Website, check under Healthy Lifestyle for Health Tools, and then Risk Assessment.

What other precautions would be advisable before I start an exercise program? Your initial level of physical fitness is an important determinant of the intensity of exercise during the early stages of the program. If you are completely unconditioned, you should start at a lower intensity level—walk before you jog, for example. Keep in mind that it took time for you to gain weight and become unconditioned, so it will also take time to reverse the process. A gradual progression is the key point. Examples are presented later. Other general precautions involve safety factors, timing of meals, environmental hazards, and equipment. The individual should adhere to safety principles for the activity selected, particularly swimming, bicycling, and pedestrian safety. Strenuous exercise should not be undertaken within 2 or 3 hours of a heavy meal, but may be done earlier with a light meal or just liquids. As noted in chapter 9, a hot environment poses the most serious threat to the person in training. Be aware of signs of heat stress such as dizziness, nausea, and weakness. If these occur, stop exercising and find a means to help cool your body. Proper equipment should be selected for the chosen activity. For example, of critical importance to the jogger or walker is a well-designed pair of shoes. They may help prevent certain medical problems, such as tendinitis and shin splints, which may occur during the early stages of training.

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What is the general design of exercise programs for weight reduction? Both resistance- and aerobic-exercise training are recommended components of a weight-loss program. Resistance training is covered in the next chapter. The basic principles of exercise training were discussed in chapter 1. In essence, aerobic-exercise programs to reduce body fat or to help maintain an optimal weight are based on the same principles that underlie exercise programs to improve the efficiency of the cardiovascular system. The total exercise program is based on a balance of exercise intensity, duration, and frequency. However, each daily exercise bout is usually subdivided into three phases—warm-up, stimulus, and warm-down, in that order (figure 11.10). A proper warm-up and warm-down are important components of the aerobic-exercise prescription. Both may help prevent excessive strain on the heart and may also be helpful in the prevention of muscular soreness or injuries. The warm-up precedes the stimulus period and may be done in several ways. It may be general in nature, such as calisthenics, or specific to the type of exercise you plan to do, such as initially exercising at a lower level of intensity of the actual mode of exercise. Some gentle static stretching exercises are also helpful in the warm-up period. For most aerobic-type exercise, it is probably better to warm up the specific muscles to be used. For example, if you plan to use jogging as your mode of aerobic exercise, you should stretch your leg muscles gently at first and then jog at a slower than normal pace for several minutes. Breaking into a sweat is a good external sign that you have sufficiently elevated your body temperature; by using a specific type of warm-up, the temperature of your exercising muscles will also be increased. The warm-down phase follows the stimulus period and is designed primarily to help restore the cardiovascular system to normal. If one stops exercising abruptly, blood may possibly pool in the exercised body parts, thereby decreasing return of blood to the heart. With less blood to the heart, the heart rate will increase rapidly in attempts to maintain blood flow. Research also indicates abrupt cessation of exercise may increase certain blood hormone levels that may cause abnormal rhythm of the heart. These factors increase stress on the heart, which may induce a heart attack in individuals at risk. Decreased blood flow to the brain may also cause dizziness and may be a cause of exercise-associated collapse discussed in chapter 9. When the warm-down occurs gradually after strenuous exercise—by walking or jogging after a strenuous run, for example—the muscles help massage the blood through the veins back to the heart. These points emphasize the importance of a gradual warm-down. Complete your warm-down by stretching. Since the muscles are now warm from the exercise they are easier to stretch, which may help prevent muscle stiffness. The warm-up and warm-down are important components of the daily exercise bout, but most of the Calories are expended during the stimulus period.

C H A P T E R 1 1 Weight Maintenance and Loss through Proper Nutrition and Exercise

Warm-up Warm-up

Stimulus Stimulus

Warm-down Warm-down

Duration Duration

5–10 minutes 5–10 minutes

15–60 15–60minutes minutes

5–10 5–10minutes minutes

Intensity Intensity

Low Low

Medium-high Medium-high

Low Low

F I G U R E 1 1 . 1 0 The exercise prescription. The exercise prescription is divided into three phases: warm-up period, stimulus period, and warm-down period. The stimulus period is the key to burning Calories.

What is the stimulus period of exercise? The stimulus period is the most important phase of the daily exercise bout. By modifying the intensity and duration of the exercise, the individual achieves the level of stimulus necessary to elicit a conditioning effect. As illustrated in figure 11.11, several important physiological and psychological measures increase in proportion to the exercise intensity. The two major components of the stimulus period are intensity and duration of exercise. In any exercise session, these two components are usually inversely related. In other words, if intensity is high, duration is short, and if intensity is low, duration is long. Frequency (the number of exercise sessions per week) is also an important part of the exercise prescription. As discussed in detail in chapter 1, two recent joint reports from the American College of Sports Medicine and the American Heart Association, authored by Haskell and Nelson and their colleagues, provided recommendations on exercise for adults (age 18–65) and older adults (over age 65) as a means to help prevent chronic diseases. These recommendations will be used as the basis for developing an aerobic fitness

program here, although they may be modified somewhat under certain circumstances. Such modifications will be noted where appropriate, particularly as related to weight control. 1. Intensity of training: For aerobic exercise, the ACSM/AHA recommends both moderate- and vigorous-intensity exercise. Several techniques, such as heart rate measurement, to determine exercise intensity are discussed below. Intensity levels are based on the fitness level of the individual. 2. Duration of training: The ACSM/AHA recommends a minimum of 30 minutes for moderate-intensity exercise, or 20 minutes of vigorous-intensity exercise. Moreover, the daily exercise time may be subdivided into multiple bouts, such as doing three 10-minute brisk walks to total 30 minutes of moderate-intensity exercise over the course of a day. Please note that this is a minimum recommendation. Although this amount of exercise may promote cardiovascular fitness, more may be needed for weight loss. 3. Frequency of training: The ACSM/AHA recommends moderateintensity exercise on 5 days each week, or vigorous-intensity

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Response

High

Heart rate Oxygen consumption Caloric expenditure RPE

Low High

Low Exercise intensity in a steady state

F I G U R E 1 1 . 1 1 The relationship among various measures of energy expenditure. Heart rate, oxygen consumption, caloric expenditure, and RPE are, in general, directly related to the intensity of the exercise under steady-state conditions, i.e., when the oxygen supply is adequate for the energy cost of the exercise.

aerobic physical activity on 3 days each week. Individuals may combine these workouts during the week, such as doing moderate-intensity exercise 2 days and vigorous-intensity on another 2 days. Exercising every day may provide some additional benefits for weight control.

What is an appropriate level of exercise intensity? The intensity of exercise is a very important component of the stimulus period; in order to receive the optimal benefits from the exercise program, you must attain a certain threshold stimulus, the minimal stimulus intensity that will produce a training effect. The intensity of exercise can be expressed in a number of different ways, such as percentage of VO2 max and Calories/minute, but these techniques are not suitable for everyday exercise. However, other easily measured variables may provide you with a good estimate of your exercise intensity, including your heart rate, your perception of how strenuous the exercise is, and your ability to carry on a conversation. Heart Rate As noted in figure 11.10, the heart rate is linearly related to oxygen consumption, which is the major measure of energy expenditure. Because the heart rate is easily obtained, it is usually used to determine the threshold level of exercise intensity. To obtain the heart rate, press lightly with the index and middle fingers on the carotid artery, located just under the jawbone and beside the Adam’s apple. Do not use the thumb as it also has a pulse, and do not press hard on the carotid artery, for it may cause a reflex slowing of the beat in some persons. The radial artery pulse is obtained by placing your fingers on the inside of the wrist on the thumb side. These are the two most common locations for monitor478

ing pulse rate, but other locations (the temple, inside the upper arm, and directly over the heart) may be used (see figure 11.12). To obtain the heart rate per minute, simply count the pulse rate for 6 seconds and add a zero. Resting and recovery heart rates are easily obtainable, as they may be taken while you are motionless, but it is difficult to manually monitor the heart rate while exercising. Research has shown that the exercise heart rate correlates very highly with the heart rate during the early stages of recovery. Hence, to monitor exercise heart rate, secure the pulse immediately upon cessation of exercise and count the beats for 6 seconds. This provides a reliable measure of exercise heart rate, although it may be slightly lower due to the beginning of the recovery effect. If it is difficult for you to monitor your heart rate for 6 seconds, then use a 10-second period and multiply the count by six to obtain your heart rate per minute. You probably should use 30 seconds to determine your resting heart rate; multiply your results by two. It may also be better to measure your resting pulse early in the morning, just after rising. Additionally, for the calculations to follow, you should take your resting heart rate in the position in which you will exercise, for example lying down if you swim, seated if you cycle, or standing if you walk or run. If you become serious about heart rate monitoring as the basis for your exercise training, you may want to invest in a device that monitors your heart rate while you exercise. Such devices usually use a comfortable chest band that transmits your heart rate to a wrist band so you can easily see your heart rate response during any phase of exercise. One of the most prevalent techniques to determine the threshold stimulus for exercise is based upon the maximal heart rate reserve (HR max reserve), the difference between the resting heart rate and the maximum heart rate. You may determine your resting heart rate shortly after you arise in the morning. If you have not been physically active in some time, it may not be advisable for you to engage in strenuous physical activity in order to determine your actual maximal heart rate (HR max), but there are ways to predict it based upon your age. Although there are individual variations, the traditional formula (A) for the prediction of HR max in women and untrained men is 220 minus the person’s age. Gellish and others, using longitudinal data, recently indicated that the 220 – age formula is biased as it overestimates measured HRmax for men and women under the age of 40 years, and underestimated HR max of those older than 40. They suggested a more relevant formula (B), 207 minus 0.7 × age. Others suggest that for physically trained men, the formula (C) 205 minus onehalf the person’s age may be more appropriate, while for obese individuals, the formula (D) 200 minus one-half the person’s age may be best. Based upon the traditional formula A, a 40-year-old untrained individual would have a predicted HR max of 180, which is about the same value predicted by the formula B. Using the formula C, a trained 40-year-old male would have a predicted HR max of 185, while an obese individual would have a predicted HR max of 180. Keep in mind, however, that there is considerable individual variation relative to predicted HR max no matter which formula is used. For example, a 40-year-old man may predict a HR max of 180, yet it may be 200, 160, or much lower if he was a victim of coronary heart disease.

C H A P T E R 1 1 Weight Maintenance and Loss through Proper Nutrition and Exercise

There is rather widespread general agreement that in order to obtain a training effect, the heart rate response should be increased above the resting level by about 50–85 percent of the HR max reserve. Recent research has revealed that lower levels, 40–45 percent, may also be effective, particularly in individuals with poor levels of physical fitness. Continuing with our example of the 40-year-old man, we can calculate the heart rate range needed to elicit a training effect. This is called the target heart rate range, or target HR. To complete the calculations, we need to know the age-predicted HR max and the resting heart rate (RHR); the latter should be determined under relaxed circumstances. If we assume a RHR of 70 and a HR max of 180, the following formula would give us the target range:

(b)

Target HR = X% (HR max – RHR) + RHR For the 50 percent threshold level, the target heart rate for our example would be calculated as follows: 0.5 (180 – 70) + 70 = 0.5(110) + 70 = 55 + 70 = 125 For the 85 percent level, the target heart rate would be 0.85(180 – 70) + 70 = 0.85(110) + 70 = 93 + 70 = 163 (c)

Thus, in order to achieve a training effect, (a) our 40-year-old man needs to train within a F I G U R E 1 1 . 1 2 Palpation of the heart rate. The pulse rate may be taken at a varitarget HR range of 125–163. ety of body locations (a), but the two most common locations are (b) the neck (carotid If you wish to bypass the calculations, artery) and (c) the wrist (radial artery). table 11.13 presents the target HR ranges for various age groups with RHR between 45 and 90 beats/minute. Simply find your age group and RHR in the headings and locate your target HR range. The table is based on a predicted HR Once you have been training for a month or so, you may max of 220 – age. If you prefer to use one of the other formulae to desire to determine your HR max in the specific activity you do. predict HR max, you may calculate your target HR range using the You may use the procedures described below, that is, running on formula presented. a track at different speeds until you reach your maximal level, In general, this table is a useful guide to the threshold heart rate modifying the test dependent upon your aerobic exercise. For and target HR range. However, there is considerable variability in example, research has revealed that HR max is lower in swimHR max among individuals, particularly in the older age groups. If ming, possibly as much as ten to fifteen beats per minute, so the your true HR max is below the predicted value (220 – age), the tartarget heart rate may be slightly lower if this mode of exercise is get HR range in the table would be higher than the recommended used. One recommendation indicates use of the formula 205 minus level. If your true HR max is higher than the predicted value, the age may be appropriate to predict maximal heart rate while target HR range in the table is lower than the recommended level. swimming. Although the target HR range might vary by a few beats, if your As you can see, the range for the target heart rate may span actual HR max is slightly higher or lower than the predicted value, about 30–50 beats. For example, a 36-year-old individual with a you will still receive a good training effect—assuming you are in resting heart rate of 72 beats per minute has a target heart rate the middle of the range. range of 127–167, or a span of 40 beats per minute. Exercising at www.mhhe.com/williams9

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TABLE 11.13

Target heart rate zones

RHR

Age 15–19

20–24

25–29

30–34

35–39

40–44

45–49

50–54

55–59

60–64

65–69

70–74

45–49

125–180

123–175

120–171

118–167

115–163

113–158

110–154

108–150

105–146

103–141

100–137

98–133

50–54

127–181

125–176

122–172

120–168

117–164

115–159

112–155

110–151

107–147

105–142

102–138

100–134

55–59

130–181

128–176

125–172

123–168

120–164

118–159

115–155

113–151

110–147

108–142

105–138

103–134

60–64

132–182

130–177

127–173

125–169

122–165

120–160

117–156

115–152

112–148

110–143

107–139

105–135

65–69

135–183

133–178

130–174

128–170

125–166

123–161

120–157

118–153

115–149

113–144

110–140

107–136

70–74

137–184

135–179

132–175

130–171

127–167

125–162

122–158

120–154

117–150

115–145

112–141

110–137

75–79

140–184

138–180

135–176

133–172

130–168

128–163

125–159

123–155

120–151

118–146

115–142

113–138

80–84

142–185

140–181

137–177

135–173

132–169

130–164

127–160

125–156

122–152

120–147

117–143

115–139

85–89

145–186

143–181

140–177

138–173

135–169

133–164

130–160

128–156

125–152

123–147

120–143

118–139

The target zone (50–85 percent threshold) is based upon the median figure for each age range and resting heart rate range.

the lower end of this range, about 127–147 beats per minute, may be considered moderate-intensity exercise, while exercising at about 148–167 beats may be considered vigorous-intensity exercise. However, for an untrained individual just starting a fitness program, a heart rate of 127–147 may appear to be vigorous at first, but as she continues to exercise and improves her physical fitness this same heart rate response may become less taxing and be perceived as moderate intensity. Moreover, as her fitness improves, her resting heart rate may decrease over time, possibly by 10 or more beats per minute, which will necessitate recalculation of the target heart rate range. Rating of Perceived Exertion (RPE) Although the target heart rate approach is a sound means for monitoring exercise intensity, you may also wish to use other methods. One popular method is the rating of perceived exertion (RPE), which is basically your perception of how hard you feel your body is working during exercise. Developed by Gunnar Borg, this scale was originally designed to reflect heart rate responses by adding a zero to the rating. You simply rate the perceived difficulty or strenuousness of the exercise task according to the column A scale in table 11.14. If you are running, how do your legs feel? Do they feel light and easy to move, or are they heavy, or possibly beginning to ache or burn? How is your breathing? Are you breathing easily and able to carry on a conversation, or are your sentences shortened to a few words? In general, how does your total body feel? Is the exercise too easy, or are you working too hard? Borg also developed an abbreviated RPE scale with 0–10 points, which is depicted in Column B in table 11.14B. The OMNI-RPE scale uses a 0–10 pictorial version of runners or cyclists displaying varying degrees of exertion, and Utter and others validated its use as comparable to the Borg RPE scale. 480

When you determine your exercise heart rate, it is a good idea to associate an appropriate RPE value with it, so that you individualize the RPE to your specific exercise program. For example, at an exercise heart rate of 150 you might make a mental note of the exercise difficulty and assign a value of 15, or hard, to that level of exercise intensity. Research has shown that the RPE can be an effective means to measure exercise intensity in healthy individuals, particularly at heart rates above 150 beats/minute. Talk Test Another possible way to monitor your exercise effort, recently validated by Persinger and others, is associated with breathing and is often referred to as the talk test. Adam Bean, an editor for Runner’s World, cited research indicating that when you can first hear yourself breathing during exercise, you are entering the lower range of your heart rate zone. When you have difficulty talking, you are near the upper range. David Swain, an expert on exercise intensity from Old Dominion University, provided some guidelines to determine moderate and vigorous levels of exercise intensity. If you are breathing harder but still able to carry on a conversation in complete sentences, you are probably exercising at a moderate intensity. However, if it is difficult for you to speak in complete sentences, you are probably exercising at a vigorous intensity. Another general rule of thumb is: If you cannot maintain a conversation while exercising, you are probably exercising too hard, unless you are training for sports competition.

How can I determine the exercise intensity needed to achieve my target HR range? To determine the exercise intensity necessary to reach your target HR range, all you need is a stopwatch. You may record your heart rate manually as explained previously, but use of a heart rate monitor

C H A P T E R 1 1 Weight Maintenance and Loss through Proper Nutrition and Exercise

The RPE scales

6 Sitting, relaxing

B 0 Extremely easy

7 Very, very light

1

8

2 Easy

9 Very light

3

10

4 Somewhat easy

11 Light

5

12

6 Somewhat hard

13 Somewhat hard

7

14

8 Hard

15 Hard

9

16

Heart rate (HR)

A

200 190 180 170 160 150 140 130 120 110 100 90 80 70 60

180 18 156 15

132 108

13

11 HR RPE

Trial Time

1 8:00

2 7:10

3 6:30

4 6:00

Minutes/ mile

16:00

14:20

13:00

12:00

20 19 18 17 16 15 14 13 12 11 10 9 8 7 6

Rating of perceived exertion (RPE)

TABLE 11.14

F I G U R E 1 1 . 1 3 Plot of heart rate and RPE following a halfmile walk in determination of the threshold heart rate.

10 Extremely hard

17 Very hard 18 19 Very, very hard 20 Maximal effort

would facilitate this task and probably increase the accuracy. Where distances are involved, such as with running, swimming, or cycling, an accurate measure is needed. An ideal situation for walking or running would be a quarter-mile (400 meters) high school or college track. A steady-state HR response may be obtained in 3 to 5 minutes of evenly paced activity. A sound method for walking, jogging, or running follows, but this system may be adapted easily to other activities such as swimming, cycling, calisthenics, and aerobic dance. Mark a one-half mile course. Two laps on a quarter-mile track would be ideal, but you can pace out a quarter-mile on the sidewalks near your home. Measure your resting HR. Walk until you have an even pace and then time yourself for the one-half mile. Immediately record your HR at the conclusion of the exercise. During your walk, mentally record the RPE. Did you reach the target HR? Was your RPE related to your HR? If the HR response was in the target range or the RPE was not too strenuous, you are at a level to begin your training program. If the HR response was not in the target range, rest until your HR returns close to normal and then take the test at a faster pace. Repeat this procedure until you have a plot of the HR, RPE, and time for the one-half mile. Keep a record of this as it will be useful in evaluating the effects of your conditioning program.

For example, suppose you recorded the following data on the one-half mile test on four trials (figure 11.13). Test 1 2 3 4

Time 8:00 7:10 6:30 6:00

RPE 11 13 15 18

HR 108 132 156 180

Minutes/Mile 16:00 14:20 13:00 12:00

As your speed increases, both RPE and HR naturally increase. If your predicted HR max is 200, and your resting HR is 70, the 50–85 percent target range approximates 135–180. Test 1 does not provide adequate stimulus intensity, Test 2 is just below the minimum target HR, Test 3 is in the middle of the range, while Test 4 is at your upper limit. Thus, your training intensity should be between 12 and 14 minutes per mile. The RPE may offer a means of judging the intensity of the exercise when you do not have a set distance and watch. To determine your speed for these tests, simply double the time for the half-mile and you have the time per mile. The last trial was 12 minutes per mile. The caloric expenditure could be obtained from appendix B.

How can I design my own exercise program? The exercise program that you design should not only be safe and effective, but it should be one to which you will adhere for a lifetime. Unfortunately, over 50 percent of the individuals who begin an exercise program to lose excess body weight drop out within a short time. Research with successful exercisers has revealed several clues that increase the likelihood of staying with an exercise program. 1. Do not exceed your abilities during the early stages of the program. Start slowly and progress gradually. If you are www.mhhe.com/williams9

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2.

3.

4.

5.

6.

overweight, it might be a good idea to start with low-impact activities, such as walking, cycling, or swimming. Even though walking is a low-impact activity, Browning and Kram note that walking at faster speeds in overweight individuals increased ground reaction forces, creating greater loads on the knee joints than normal weight adults. These knee-joint loads could be reduced by walking slower, at a speed about 2.5 miles per hour. This may be a good strategy to use in the early stages of a weight-loss program utilizing walking. Set both short-term and long-term goals. A short-term goal may be to walk a mile in 15 minutes, while a long-term goal may be the completion of a local 10-kilometer (6.2-mile) road race. Keep a record of your exercise. This will allow you to evaluate your progress toward your goals. Buy a pedometer. TudorLocke and Bassett indicate that the pedometer, a seemingly insignificant gadget, may be of practical importance in the war on obesity. It will help you document your daily physical activity in an objective way, evaluate your progress over time, and serve as a cue to remind you to be active that may motivate you to exercise more. You must have time available to exercise. Most of us are busy with work, school, family, and friends, so finding the time to exercise is often difficult. Block out time in your daily schedule just as you do for other activities. Exercising before breakfast, at lunch, or immediately after work are some of the strategies used by busy individuals. Doing two things at once, such as running on a treadmill while watching the evening news is another useful strategy. A place to exercise must be convenient. You are more likely to find an excuse not to exercise if you have to travel 5 miles in heavy traffic to a health club. Find a convenient location. Self-motivation is probably the most important determinant of adherence to an exercise program. Enjoying your exercise program, being capable at the exercise task, and knowing that it will help you attain your goals will improve your motivation and hopefully make daily exercise a lifetime habit.

Although diverse modes of aerobic exercise may be used to lose body weight and to help condition the cardiovascular system, the major focus here will be on walk-jog-run programs. This is because they satisfy many of the criteria that may encourage adherence to an exercise program. Former U.S. Surgeon General C. Everett Koop indicated that walking for exercise should be elevated to a national priority. Walking may be the ideal exercise program for many individuals. Compared to jogging and running there is less stress on the legs due to impact because one foot is always on the ground supporting the body weight. However, leisurely walking usually will not provide an adequate stimulus to achieve the target HR, so the walking pace must be brisk. Walking at a faster-than-normal pace is often called aerobic walking, and if done properly can expend Calories at about the same rate as jogging or running. Vigorous arm action 482

is needed, and the length of the stride as well as the step rate must be increased. Also, using hand weights will increase the energy expenditure by about 5–10 percent and also will help tone the arm muscles if used vigorously. Adding 3 pounds to each wrist will increase energy output about 1 Calorie per minute. Carrying the weights in the hands tends to increase the blood pressure more, so it may be helpful to use weights that strap around the wrist. Another alternative is to wear a weighted vest. Puthoff and others reported that using a weighted vest increases the metabolic cost of walking in a linear fashion. For example, wearing a vest that added 10, 15, and 20 percent of body weight increased energy expenditure, respectively, by 6.3, 9.4, and 11.5 percent while walking at 2 miles per hour; the percent increases were greater at faster walking speeds. The authors also noted the added weight could provide an additional benefit by stimulating bone development, but might be a detriment if it contributed to muscle injury or skeletal injury such as a stress fracture. Although hand weights and weighted vests may increase your energy expenditure at any given walking speed, you may expend similar amounts of Calories by simply walking faster or longer without added weight. A wide variety of methods may be used to initiate an aerobic exercise program of walking, jogging, or running. The key is to begin slowly, gradually increasing the exercise intensity as you become better conditioned. Once you determine the intensity of exercise necessary to achieve the target HR, it becomes a relatively simple matter to individualize the exercise program. The two tables presented on pages 483–484 include exercise programs for individuals who have been sedentary and have low levels of physical fitness. Use your target HR guidelines throughout the 12to 15-week program. In the early weeks you should attempt to exercise only at the 50–60 percent target HR range. However, if you find that the exercise intensity needed to achieve this level is too strenuous, reduce it to 40 percent of your calculated heart-rate reserve. As you become more fit, gradually increase your target HR to the 50–85 percent level. As recommended in the ACSM/AHA position stand, you may vary your exercise program by doing moderate-intensity exercise several days a week and vigorous-intensity exercise several other days. Table 11.15 presents a sample aerobic walking program. It is designed to progress you gradually through 12 weeks to a point where the exercise intensity and duration may make a significant contribution to weight loss over time. If you feel fit you may progress more rapidly than the table indicates, but stay within your target HR range and do not become unduly fatigued. Table 11.16 presents an exercise program with a rapid progression to jogging, using an interval-training approach. Interval training alternates periods of rest and exercise. Again, the target HR method should be used during this exercise program. As compared to walking, jogging or running may expend 2–3 times the amount of Calories per unit of time. Thus, it may be worthwhile to interject short bouts of more intense exercise into a workout, such as jogging one block out of every three or four when walking. Moreover, research has indicated that more intense exercise may confer additional health benefits. Swain and Franklin concluded that exercise performed at a vigorous intensity appears to convey greater cardioprotective benefits than exercise of moderate intensity, while Franco

C H A P T E R 1 1 Weight Maintenance and Loss through Proper Nutrition and Exercise

TABLE 11.15

Sample aerobic walking program Warm-up

Target zone exercising

Warm-down

Total time

Week 1*

Walk slowly 5 minutes

Walk briskly 5 minutes

Walk slowly 5 minutes

15 minutes

Week 2

Walk slowly 5 minutes

Walk briskly 7 minutes

Walk slowly 5 minutes

17 minutes

Week 3

Walk slowly 5 minutes

Walk briskly 9 minutes

Walk slowly 5 minutes

19 minutes

Week 4

Walk slowly 5 minutes

Walk briskly 11 minutes

Walk slowly 5 minutes

21 minutes

Week 5

Walk slowly 5 minutes

Walk briskly 13 minutes

Walk slowly 5 minutes

23 minutes

Week 6

Walk slowly 5 minutes

Walk briskly 15 minutes

Walk slowly 5 minutes

25 minutes

Week 7

Walk slowly 5 minutes

Walk briskly 18 minutes

Walk slowly 5 minutes

28 minutes

Week 8

Walk slowly 5 minutes

Walk briskly 20 minutes

Walk slowly 5 minutes

30 minutes

Week 9

Walk slowly 5 minutes

Walk briskly 23 minutes

Walk slowly 5 minutes

33 minutes

Week 10

Walk slowly 5 minutes

Walk briskly 26 minutes

Walk slowly 5 minutes

36 minutes

Week 11

Walk slowly 5 minutes

Walk briskly 28 minutes

Walk slowly 5 minutes

38 minutes

Week 12

Walk slowly 5 minutes

Walk briskly 30 minutes

Walk slowly 5 minutes

40 minutes

From week 13 on, check your pulse periodically to see if you are exercising within your target heart rate range. As you become more fit, walk faster to increase your heart rate toward the upper levels of your target range. Follow the principle of progression. Note: If you find a particular week’s pattern tiring, repeat it before going on to the next pattern. You do not have to complete the walking program in 12 weeks. Remember that your goal is to continue getting the benefits you are seeking—and to enjoy your activity. Listen to your body and progress less rapidly, if necessary. *Program should include at least three exercise sessions per week. Source: U.S. Department of Health and Human Services.

and others reported that although moderate levels of physical activity increased life expectancy, the gains were twice as large, about two additional years, with higher activity levels. Whatever mode of exercise you select, the target HR should be maintained for 20–30 minutes. This may be continuous or intermittent. If 30 minutes is the allotted time, the target HR should be achieved for 30 continuous minutes or three 10-minute intervals of exercise with several minutes of rest in between. The frequency of exercise should be daily or at least three to five times per week. The ACSM/AHA position stand recommends 5 days a week of moderate-intensity exercise or 3 days a week of vigorous-intensity exercise to develop and maintain cardiovascular health. During the early stages, however, it may be advisable to exercise daily in order to form sound habits. The exercise intensity at this time may not be too severe, such as walking, and hence daily exercise bouts may be undertaken without serious muscle soreness or related injury patterns. If you switch to jogging or running, decrease the frequency to three or four times per week to avoid overuse injuries. The frequency per week may be increased as you become better physically conditioned. To increase weekly energy expenditure and help prevent overuse injuries, engage in crosstraining exercises on days you do not jog or run. For weight-control purposes, duration and frequency of exercise are key elements. The longer and more often you exercise, the

greater will be the total amount of energy expended. Aerobic walking for 5 miles on a daily basis is the equivalent of approximately 1 pound of body fat per week. There are a number of other excellent conditioning programs available for the unconditioned individual. Probably the most popular is the aerobics program developed by Dr. Kenneth Cooper. Although dated, his programs may be found in The Aerobics Program for Total Well Being, a highly recommended paperback found in most bookstores. Also, books on initiating walking and other aerobic exercise programs are available at your library or local bookstores, and various Websites provide very helpful information. www.americaonthemove.org www.walking.org These Websites provide detailed information on beginning and maintaining a fitness walking program and associated health benefits, including weight loss. www.10000steps.org.au This Australian Website provides advice on how to walk 10,000 steps daily, with a link on how to convert other activities into steps. www.gmap-pedometer.com This program permits you to calculate distances of walking or jogging routes in your neighborhood or anywhere in the country.

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TABLE 11.16

Sample aerobic jogging program (interval training) Warm-up

Target zone exercising

Warm-down

Total time

Week 1*

Stretch and limber up 5 minutes

Walk (nonstop) 10 minutes

Walk slowly 3 minutes; stretch 2 minutes

20 minutes

Week 2

Stretch and limber up 5 minutes

Walk 5 minutes; jog 1 minute; walk 5 minutes; jog 1 minute

Walk slowly 3 minutes; stretch 2 minutes

22 minutes

Week 3

Stretch and limber up 5 minutes

Walk 5 minutes; jog 3 minutes; walk 5 minutes; jog 3 minutes

Walk slowly 3 minutes; stretch 2 minutes

26 minutes

Week 4

Stretch and limber up 5 minutes

Walk 5 minutes; jog 4 minutes; walk 5 minutes; jog 4 minutes

Walk slowly 3 minutes; stretch 2 minutes

28 minutes

Week 5

Stretch and limber up 5 minutes

Walk 4 minutes; jog 5 minutes; walk 4 minutes; jog 5 minutes

Walk slowly 3 minutes; stretch 2 minutes

28 minutes

Week 6

Stretch and limber up 5 minutes

Walk 4 minutes; jog 6 minutes; walk 4 minutes; jog 6 minutes

Walk slowly 3 minutes; stretch 2 minutes

30 minutes

Week 7

Stretch and limber up 5 minutes

Walk 4 minutes; jog 7 minutes; walk 4 minutes; jog 7 minutes

Walk slowly 3 minutes; stretch 2 minutes

32 minutes

Week 8

Stretch and limber up 5 minutes

Walk 4 minutes; jog 8 minutes; walk 4 minutes; jog 8 minutes

Walk slowly 3 minutes; stretch 2 minutes

34 minutes

Week 9

Stretch and limber up 5 minutes

Walk 4 minutes; jog 9 minutes; walk 4 minutes; jog 9 minutes

Walk slowly 3 minutes; stretch 2 minutes

36 minutes

Week 10

Stretch and limber up 5 minutes

Walk 4 minutes; jog 13 minutes

Walk slowly 3 minutes; stretch 2 minutes

27 minutes

Week 11

Stretch and limber up 5 minutes

Walk 4 minutes; jog 15 minutes

Walk slowly 3 minutes; stretch 2 minutes

29 minutes

Week 12

Stretch and limber up 5 minutes

Walk 4 minutes; jog 17 minutes

Walk slowly 3 minutes; stretch 2 minutes

31 minutes

Week 13

Stretch and limber up 5 minutes

Walk 2 minutes; jog slowly 2 minutes; jog 17 minutes

Walk slowly 3 minutes; stretch 2 minutes

31 minutes

Week 14

Stretch and limber up 5 minutes

Walk 1 minute; jog slowly 3 minutes; jog 17 minutes

Walk slowly 3 minutes; stretch 2 minutes

31 minutes

Week 15

Stretch and limber up 5 minutes

Jog slowly 3 minutes; jog 17 minutes

Walk slowly 3 minutes; stretch 2 minutes

30 minutes

From week 16 on, check your pulse periodically to see if you are exercising within your target zone. As you become more fit, try exercising within the upper range of your target zone. Note: If you find a particular week’s pattern tiring, repeat it before going on to the next pattern. You do not have to complete the jogging program in 15 weeks. Remember that your goal is to continue getting the benefits you are seeking—and to enjoy your activity. *Program should include at least three exercise sessions per week. Source: U.S. Department of Health and Human Services.

How much exercise is needed to lose weight? Although a properly planned exercise program may produce significant health benefits even without weight loss, most individuals use exercise to decrease body fat. Although weight loss depends 484

on both a balance of energy expenditure through exercise and energy intake through your diet, some guidelines on recommended amounts of exercise for weight loss are available from professional and governmental health organizations.

C H A P T E R 1 1 Weight Maintenance and Loss through Proper Nutrition and Exercise

Jakicic and Gallagher noted that the magnitude of exercise required to facilitate successful long-term weight loss may be greater than what is necessary to elicit significant improvements in health. For example, the ACSM/AHA minimum recommendation (30 minutes of moderate-intensity exercise, 5 days per week) for cardiovascular health benefits totals 2.5 hours per week, which would approximate 1,000–1,200 Calories energy expenditure. However, the ACSM/AHA notes that this is a minimum, and more exercise is better. This is particularly so for weight loss and maintenance. Increasing exercise duration and frequency is the key. In its position stand on weight control, the ACSM indicates that approximately 4.5 hours of moderate-intensity exercise that results in an energy expenditure of at least 2,000 calories per week, in combination with reduced caloric intake, will produce desirable weight-loss results. In their review, Rippe and others indicated that successful weight-loss programs incorporated exercise programs that increased energy expenditure by about 1,500–2,000 Calories per week, which would be in accord with the latter viewpoint of the ACSM. Wing and Phelan noted that successful weight losers in the National Weight Control Registry exercised about 1 hour or more per day. Walking is their number one exercise, but they also engage in resistance training, and other physical activities. Collectively, this amount of physical activity would approximate 1,500–2,000 Calories weekly. Finally, the Institute of Medicine of the National Academy of Sciences indicates that 30 minutes per day of regular activity is insufficient to maintain body weight within the recommended Body Mass Index range, and hence recommends 60 minutes of daily moderateintensity physical activity. Walking or jogging at 4–5 MPH is recommended, in addition to the activities required by a sedentary lifestyle. This amount of physical activity leads to an active lifestyle, corresponding to physical activity levels (PAL) greater than 1.6, and is appropriate for both children and adults. Such an activity level for 6–7 days a week would approximate 2,000 Calories or more of energy expenditure. Collectively, the optimal exercise energy-expenditure goal appears to be 1,500–2,000 Calories per week, or about 200–300 Calories per day. For walkers, this approximates 10,000 steps daily. The average person walks about 5,000 steps a day, and studies have shown that such individuals are overweight as compared to those who walk 10,000 or more steps daily. Gradually adding about 5,000 or 6,000 steps of brisk walking per day to a sedentary routine would approximate 200–300 additional Calories expended, or about 1,500–2,000 per week. Use of a good pedometer will help you keep track of daily steps, and will also serve as a motivation device to encourage you to walk. The average person takes about 2,000 steps per mile. Walking 100 steps per minute, about 3 miles per hour, may be a moderate-intensity pace. Walking about 130 steps per minute approximates 4 miles per hour, which is definitely a brisk pace and may be a recommended long-term goal. Walking even faster may approach the energy equivalency of jogging at the same pace. As related to the Physical Activity Level (PAL) presented earlier in this chapter, Tudor-Locke and others proposed similar guidelines relative to walking and level of daily physical activity:

Sedentary Low active Somewhat active Active Highly active

12,500 steps

From what parts of the body does the weight loss occur during an exercise weight-reduction program? As mentioned previously, weight loss may come from any one of three body sources—body water, lean tissue such as muscle, and body-fat stores. A diet program, especially one very low in Calories, will cause a rapid weight loss due to decreases in body water and lean tissue. Body-fat losses are moderate at first but may increase in later stages of the diet. On the other hand, weight lost through an exercise program alone is lost at a much slower rate. Body water levels remain relatively normal after replacement of water lost through exercise. The lean tissues, particularly muscle, might actually increase in amount from the stimulating effect of exercise on muscle development. Because a good proportion of the energy demand for exercise is met by the oxidation of fat, most of the body-weight reduction comes from the body-fat stores, particularly in the abdominal area (figure 11.14). As we learned previously, the caloric cost of 1 pound of fat is much higher than that of water or lean muscle tissue. Thus, loss of body fat through exercise takes time, highlighting the importance of the long-haul concept and long-term weight loss goals.

Should I do low-intensity exercises to burn more fat? A myth that is circulating contends that in order to burn fat, you must exercise at a lower percentage of your VO2 max. As noted in chapters 3, 4, and 5, it is true that the percentage of energy obtained from fat is greater at lower exercise intensities (e.g., 50 percent VO2 max) than at higher exercise intensities (e.g., 70 percent VO2 max). However, at the higher energy intensity you will derive a lower percentage of your energy output from fat, but the total energy expenditure will be greater and you will still burn about the same amount of fat Calories as you would exercising at the lower intensity providing you are exercising for the same amount of time. If you want to burn Calories to lose body fat, your objective should be to burn the greatest total Calories possible within the time frame you have to exercise. As an example, suppose a female had 30 minutes to exercise and exercised at 50 percent VO2 max, running 10-minute miles and deriving 50 percent of her energy from fat. She would cover 3 miles, expending 300 total Calories at an energy cost of about 100 Calories per mile, 150 (0.50 × 300) of which would be fat Calories. If she was able to run at 75 percent VO2 max, running 7.5-minute miles and deriving 33 percent of her energy from fat, she would cover 4.5 miles, expending 450 total Calories, of which 150 (0.33 × 450) would still be fat Calories. However, she has expended a total of www.mhhe.com/williams9

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Is spot reducing effective? Spot reducing uses isolated exercises in an attempt to deplete local fat deposits in specific body areas. These techniques do not appear to be effective. In one study the fat tissue was biopsied to determine whether sit-ups would reduce fat in the abdominal area. Subjects did a total of 5,000 sit-ups over a 27-day period, but this localized exercise did not preferentially reduce the adipose cell size in the abdominal area. In another study, magnetic resonance imaging (MRI) was used to quantify the subcutaneous fat tissue in the upper arm. Kostek and others reported no changes in men and women engaged in resistance training of one arm for 12 weeks. In their review, Smith and Zachwieja indicated that the current view suggests that the reduction of fat in body areas is most likely to occur where fat deposits are the most conspicuous (usually the abdominal area), regardless of the weight-loss format, including exercise. However, some areas of the body are somewhat resistant to change, particularly the gynoid-type fat distribution around the hips and thighs. Although both large-muscle activities and local isolated-muscle exercises may be beneficial in reducing fat stores, the former are recommended because the total caloric expenditure will be larger.

FFA

Abdominal adipose tissue FFA

Blood FFA

Muscle

CO2

H2O

Energy

Is it possible to exercise and still not lose body weight? F I G U R E 1 1 . 1 4 Exercise helps to release fat (free fatty acids) from the adipose tissues, particularly abdominal fat cells. The fat then travels by way of the bloodstream to the muscles where the free fatty acids are oxidized to provide the energy for exercise. Thus, exercise is an effective measure of reducing body fat.

450 versus 300 Calories at the higher exercise intensity, which will lead to a greater weight loss or permit her to consume an additional 150 Calories in her daily diet. But, if she has unlimited time, she may be able to exercise longer at the lower exercise intensity and eventually burn more total Calories including more fat Calories. Keep in mind, as noted in chapters 4 and 5, as you become highly trained in aerobic endurance exercise, you become a better fat burner and will be able to oxidize fat at higher exercise intensities. For example, Romijn and others have found that in endurance-trained men and women, the highest rate of fat oxidation was during exercise at 65 percent of maximal oxygen uptake. If you want to burn 500 Calories per day by running 5 miles, it does not matter how fast you run. For weight-control purposes, the total distance covered, which translates into total Calories expended, is the key point. As noted in chapter 3, you may estimate the energy it costs you to run 1 mile by simply multiplying your body weight in pounds by 0.73 Calories. 486

Many individuals are disappointed during the early stages of an exercise program because they do not lose weight very rapidly. Unless they understand what is happening in their bodies, the results on the scale may convince them that exercise is not an effective means of reducing weight, and they may quit exercising altogether. There are several reasons why an individual may not lose weight during the early stages of a weight-reduction program, and also why losing weight becomes more difficult after weight loss has occurred. When a sedentary individual begins a daily exercise program, the body reacts to the exercise stress and changes so it can more easily handle the demands of exercise (figure 11.15): 1. 2.

3. 4. 5.

The muscles may increase in size because of hypertrophy of the muscle cells. The increased protein will hold water. Certain structures within the muscle cell that process oxygen, along with numerous enzymes involved in oxygen use, will increase in quantity. Energy substances in the cell will increase, particularly glycogen, which binds water. The connective tissue will toughen and thicken. The total blood volume may increase. An increase of approximately 500 milliliters, or about a pound, has been recorded in 1 week.

C H A P T E R 1 1 Weight Maintenance and Loss through Proper Nutrition and Exercise

your energy input in food and your body weight has stabilized. In theory, you have reached your settling point. In addition, you may become more skilled, and hence more efficient, in your physical activity. Fewer Calories may then be expended for any given amount of time. However, this is usually true only of activities that involve a skill factor. It can be highly significant in swimming, but not as great in jogging. In summary, your body weight may not change during the early stages of an exercise program; it may then begin to drop during a second stage, and then plateau at the third stage. If you are aware of these possible stages, your adherence to an exercise program may be enhanced. Also, during the third stage, if you desire to lose more weight by exercise, the amount of exercise will need to be increased.

Aerobic exercise effects ↑ Muscle tissue ↑ Blood volume ↑ Muscle glycogen ↑ Body water ↓ Body fat

What about the five or six pounds a person may lose during an hour of exercise? 130

130

Start exercise program

One month later

F I G U R E 1 1 . 1 5 Body weight may not change much during the beginning phases of an aerobic exercise program. However, body composition may change. The exercise stimulates an increase in muscle tissue, blood volume, and muscle glycogen stores, which tend to increase weight. Body fat is reduced, but the increases in the other components can balance out the fat losses with no net loss of body weight. Eventually, body weight, particularly abdominal fat, begins to drop as the exercise program is continued.

At the same time, however, body-fat stores will begin to diminish somewhat as fat is used as a source of energy for exercise. Overall, there may be an increase in body water and lean body mass, particularly the muscle tissues, and a decrease in body fat. These changes may counterbalance each other, and the individual may not lose any weight. However, although little or no weight is lost during those early phases, the body composition changes are favorable. Body fat is being lost, particularly from the abdominal fat depots. Once these adaptive changes have occurred, which may take about a month, body weight should decrease in relationship to the number of Calories lost through exercise. Keep in mind that weight loss will be slow on an exercise program, but if you can build up to an exercise energy expenditure of about 300 Calories per day, then about 2.5 pounds per month will be exercised away provided you do not compensate by eating more. After several months you may begin to notice that your body weight has stabilized even though you continue to exercise and have not reached your weight goal. Part of the reason may be your lower body weight. If you look at appendix B, you can see that the less you weigh, the fewer Calories you burn for any given exercise. If you have been doing the same amount of exercise all along, you may now be at the body weight where your energy output is matched by

A rapid weight loss may occur during exercise. Some individuals have lost as much as 10–12 pounds in an hour or so. As you probably suspect, this weight loss may be attributed to body-water losses. This is particularly evident while exercising in warm or hot weather. The weight loss is temporary, and under normal food and water intake the body-water content will return to normal. Each pound of weight lost this way is 1 pint of fluid, or 16 ounces. A 2.2-pound weight loss would be the equivalent of 1 liter. In the heat of summer, you may occasionally see an individual training with heavy sweat clothes or a rubberized suit. The reason often given is to lose more body weight. The individual will lose more body weight, but again it will be body water which will be regained as soon as he or she drinks fluids. In this regard, the technique is worthless. Moreover, it may predispose the individual to an unusually high heat stress, causing severe medical problems. Remember, only sweat that actually evaporates will help reduce the heat stress on the body. Any water lost through dehydration should be replaced before the next exercise session, especially when exercising in warm environments. The importance of rehydration and problems associated with exercise in the heat were covered in chapter 9.

Ke y C o n c e p t s 䉴 Aerobic exercise can increase energy expenditure considerably,

but in order to lose body fat through exercise one should think in terms of months, not days. 䉴 Aerobic weight-reduction exercises need to involve large muscle masses, such as the legs in jogging or bicycling or the arms and legs in swimming. Brisk walking is a highly recommended exercise program. 䉴 The general design of the aerobic weight-reduction exercise programs involves three phases: warm-up, exercise stimulus, and warm-down. Continued

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䉴 An effective means of monitoring aerobic exercise intensity is the



䉴 䉴





exercise heart rate (HR). The exercise target HR varies depending upon age and level of conditioning. Ratings of perceived exertion (RPE) and the talk test may also be used to gauge exercise intensity. Walking is one of the recommended exercises for health and weight control. Here are a few historical quotes relative to the benefits of walking. Walking is our best medicine. Hippocrates Before supper take a little walk. After supper do the same. Erasmus I have two doctors, my left leg and my right leg. Sir George Trevelyan A slow, steady progression in exercise intensity is important in preventing excess stress and injuries. Duration and frequency of exercise are important considerations for weight loss. A weekly expenditure of 1,500–2,000 Calories from exercise appears to be a reasonable and effective means to induce and maintain weight loss. For several reasons weight loss may not occur in the early stages of an exercise program; however, the body composition changes are favorable, that is, a decrease in body fat and increase in fat-free mass. A resistance-exercise program may be very helpful to maintain or increase fat-free mass. The rapid weight loss observed after a single bout of exercise is due to water loss through sweating.

C h e c k f o r Yo u r s e l f Using several different types of physical activity that you enjoy, use appendix B and calculate how much time you would need to allocate to each in order to burn 500 Calories per day.

Comprehensive Weight-Control Programs Although numerous studies with well-planned diet or diet-andexercise programs have provided evidence of significant weight loss during the course of the research, many have also shown a high rate of relapse once the study ended. Accordingly, in a conference relative to methods for voluntary weight loss and control, the National Institutes of Health indicated that the most important feature of a successful weight-loss or weight-control program is maintenance of the stable or reduced body weight. The NIH noted that the fundamental principle of weight loss and control is a commitment to a change in lifestyle, a viewpoint shared by the American Dietetic Association in their most recent position statement on weight management. Behavioral modification incorporating properly designed diets and exercise programs, as detailed in this chapter, is the key to a comprehensive weight-control program to not only take off excess body fat, but to keep it off. 488

Which is more effective for weight control—dieting or exercise? Dieting alone or exercise alone may be an effective means to reduce body fat, but each technique has certain advantages and disadvantages. However, it appears that the advantages of one technique help counterbalance the disadvantages of the other. Dieting will contribute to a negative caloric balance and may help bring about a rapid weight reduction early in the program. Dieting alone may be an effective means to lose excess body fat. In a recent 6-month study, Redman and others found that dieting alone (25% reduction in caloric intake) induced similar total body fat and abdominal fat losses compared to subjects who created a similar energy deficit by both diet and aerobic exercise (12.5% reduction in caloric energy intake plus 12.5% increase in exercise energy expenditure). Both weight-loss programs induced similar changes in body composition. Several studies indicate that increasing the proportion of caloric intake from protein may also help maintain lean body mass on a weight-loss diet. Aerobic exercise alone may also be an effective means to lose excess body fat. Stiegler and Cunliffe note that exercise training is associated with an increase in energy expenditure, thus promoting changes in body weight and composition provided that dietary intake remains constant. Moreover, adding resistance exercise may provide additional benefits. Contrary to the results of the study by Redman and others, in their review Stiegler and Cunliffe stated that research to date suggests that the addition of exercise programs to dietary restriction can promote more favorable changes in body composition than diet on its own. For example, Hansen and others note that adding exercise to a diet program may prevent decreases in lean body mass, which could help maintain resting energy expenditure. Exercise may confer other benefits. Hansen and others also contend that exercise may improve dietary compliance. Once the body weight goal has been attained, expending 400–500 Calories daily through physical activity allows one to consume that many additional Calories. Instead of a 2,000-Calorie diet, one may consume 2,400 to 2,500 Calories. Hill notes that dieting alone to maintain weight is designed to fail in the long run. Although some can do it, they are few in number. Exercise enables one to eat more during the maintenance phase. Finally, although noting no differences in body composition compared to dieting alone, Redman and others support the role of aerobic exercise in a weight-loss program because it can also improve aerobic fitness, which has other important cardiovascular and metabolic implications. Some of the most meaningful data regarding long-term weight maintenance has been obtained by studying the habits of members of the National Weight Control Registry. The average member has lost about 70 pounds and has kept it off for over 6 years. Wing and Phelan recently reviewed some of their key behaviors, which included the following: • Eat a low-Calorie diet; low in fat and high in carbohydrate • Eat breakfast; reduce hunger later in the day • Watch only a limited amount of television

C H A P T E R 1 1 Weight Maintenance and Loss through Proper Nutrition and Exercise

• Do about 60 minutes or more of physical activity daily; walking is the favorite exercise, but also engage in aerobic classes, resistance training, cycling, and swimming. They expend 2,000 or more Calories weekly through physical activity. • Weigh themselves frequently; daily or several times a week; helps prevent a lapse from becoming a relapse Resistance training (covered in the next chapter) added to a weight-reduction program may also be very effective in helping to maintain lean body mass. Preferably, both aerobic and resistance exercise should be part of a comprehensive weight-control program. A recent study by Kraemer and others found that the combination of aerobic endurance training and resistance training, compared to dieting alone, exerted more favorable effects on body composition and health-related fitness measures. Sillanpää and others compared the effects of strength and endurance training, both separately and combined, on body composition of men from age 40 to 65. Over the course of 21 weeks they found that the combination of strength and endurance exercise optimized body composition compared to either exercise done separately. Dolezal and Potteiger indicated that combining aerobic and resistance exercise provides the beneficial effects of both types of exercise. Consider the following. A dietary reduction of 500 Calories per day, along with an exercise energy expenditure of 500 Calories per day, could lead to approximately 2 pounds of weight loss per week, about the maximal amount recommended unless under medical supervision. The removal of 500 Calories from the diet could be done immediately by simply reducing the amount of sugar and fat in the daily diet and using some of the behavioral modification techniques cited earlier. You should review those suggestions given earlier relative to the substitution of nutrient-dense foods for high-Caloric ones. Relative to exercise it may take a month or more before you may be able to use 500 Calories daily, but by following the progressive plans outlined earlier in this chapter you should be able to reach that level safely. In the meantime, increase your level of NEAT by climbing stairs and walking more to add to your daily caloric expenditure. Hence, a comprehensive weight-reduction program involving both a dietary and an exercise regimen, along with supportive behavioral modification techniques, is highly recommended by major health-related organizations such as the American Dietetic Association and the American College of Sports Medicine. The principles of developing such a program have been presented in the preceding three sections of this chapter.

If I want to lose weight through a national or local weight-loss program, what should I look for? The weight-loss industry is a multibillion dollar business. National programs, such as Weight Watchers and the Jenny Craig plan, may charge about $100 per week or more for their comprehensive programs. Unfortunately, there is little governmental control over many of these programs, and while the

national programs may be well designed, others may not provide appropriate programs for safe and effective long-term weight loss. What do authorities recommend you should receive for your money if you want to enroll in a commercial weight-loss program? The following points are adapted and summarized from the report of a task force to establish weight-loss guidelines for the state of Michigan, and from other health professional sources, such as Partnership for Healthy Weight Management. 1. The staff should be well trained in their specialty, preferably having appropriate educational backgrounds, such as a physician, nurse, dietician, or exercise physiologist. 2. You should receive a medical screening, verifying you have no medical or psychological condition that might be exacerbated by weight loss through dieting or exercise. 3. A reasonable weight goal should be established given your weight history. 4. The rate of weight loss, after the first 2 weeks, should not exceed 2 pounds per week. 5. You should receive an individualized treatment plan based on your weight-loss goal. You should also obtain an itemized list of costs. 6. The program should disclose in writing all health risks and benefits associated with the program, and you should have the opportunity to read them and sign an informed consent form. 7. The diet should be one that a. contains no less than 1,000–1,500 Calories per day b. is between 10–30 percent fat Calories c. has at least 100 grams of carbohydrate per day d. provides at least 100 percent of the RDA; supplements, if used, should not exceed 100 percent of the RDA e. if under medical supervision, contains at least 600 Calories and 50 grams of carbohydrate per day 8. The program should have a nutrition-education component that stresses permanent lifestyle changes in your eating habits. 9. Both aerobic and resistance exercise should be a component in the program. The focus should be on aerobic exercise, following the standards relative to mode, intensity, duration, and frequency discussed earlier in this chapter. It should be an exercise program you can live with for a lifetime. Guidelines for resistance exercise are presented in the next chapter. 10. Behavior-modification techniques should be individualized to help you incorporate sound dietary and exercise habits into your personal lifestyle. 11. There should be a weight-maintenance phase in the program once you have achieved your weight-loss goal. This should be a high priority to help you maintain your healthy body weight. Tsai and Wadden conducted a systematic review of major commercial weight-loss programs in the United States, and indicated that all programs can work to induce weight loss. The major problem is getting people to stick with the program. The greater the compliance, such as in programs like Weight Watchers, the greater the success. www.mhhe.com/williams9

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Guidelines similar to those just given should be used if you want to join a health or fitness club facility, particularly the qualifications of the staff and the availability of a variety of safe exercise equipment. Personal trainers should be certified by reputable professional organizations. The Consumers Union indicates that anyone can become a certified personal trainer as there are no national standards for certification. Some Websites offer certification for minimal effort and several hundred dollars. The Consumers Union indicates that the best certification is provided by:

As noted in the preceding chapter, use of improper weight-loss methods such as starvation, diuretics, laxatives, appetite-suppressing drugs, and dehydration may predispose young athletes to various health problems and impaired performance. Of particular concern are young female athletes in leanness sports who may develop long-term health problems associated with the female athlete triad, such as osteoporosis. The American Academy of Pediatrics has recommended healthy weight maintenance or loss practices for young athletes. Some of its key points for young athletes are:

• The American College of Sports Medicine • The American Council on Exercise • The National Strength and Conditioning Association

• To start early to permit a gradual weight loss over a realistic time period. • To eat enough to cover the energy costs of daily living, growth, building and repairing muscle tissue, and participating in sports. • To lose excess fat without reducing lean muscle mass or causing dehydration, both of which can impair performance. • To exceed no more than 1.5% of the total body weight, or 1 to 2 pounds per week. • To lose excess weight by both diet and extra exercise. • To obtain from the diet approximately 55–65% of energy from carbohydrate, 15–20% from protein, and 20–30% from fat. • To maintain the desired body weight, once attained, rather than cycling up and down. • To discuss any desired weight loss with a healthcare professional and the family.

Additionally, a Certified Specialist in Sports Dietetics (CSSD) would be a well-qualified contact for weight control, not only for the general population but also for athletes. A personal trainer may help you plan an effective exercise program, including both aerobic and resistance exercise, to help you lose excess body weight. You can check with local fitness-oriented organizations, such as the YMCA, for a list of personal trainers, their certification, and their fees. Although some individuals may need the structure of such programs, many successful individuals have lost excess body fat and kept it off with programs they designed by themselves. www.acefitness.org; www.acsm.org; www.nsca-lift.org The Consumers Union indicates that the best certification programs for personal trainers are presented by the American Council on Exercise, the American College of Sports Medicine, and the National Strength and Conditioning Association. You can use the Website to obtain a list of certified trainers in your vicinity. www.eatright.org The American Dietetic Association Website provides a list of local registered dietitians (RD) with specialty in sports nutrition and weight control.

Other sports-related organizations, such as the National Collegiate Athletic Association, and the National Federation of State High School Associations, have made regulations and recommendations specific to the sport of wrestling, including the following: • Dehydration techniques such as rubber suits, saunas, steam baths, hot rooms, laxatives, and diuretics should be prohibited. • Have the weigh-in immediately prior to performance to discourage rapid dehydration and weight-gain techniques. • Encourage methods to predict a minimum body-fat percentage or body weight.

What type of weight-reduction program is advisable for young athletes?

What is the importance of prevention in a weight-control program?

The American Academy of Pediatrics notes that weight control is perceived to be advantageous for youths involved in sports such as bodybuilding, cheerleading, dancing, distance running, crosscountry skiing, diving, figure skating, gymnastics, martial arts, rowing, swimming, weight-class football, and wrestling, which emphasize thinness, leanness, and/or competing at the lowest possible weight for aesthetic appeal or economy of movement. Such athletes may want to maintain or lose body weight, but weight lost should be fat, not muscle. In general, athletes who desire to lose weight to enhance performance must rely primarily on dietary modifications because they are already exercising intensely. Excessive weight loss, especially in young athletes, is a major concern in sports.

Health practices designed to prevent the development of chronic diseases currently are being promoted heavily by several major health organizations, and many have focused on the adverse health effects of obesity. For example, the Canadian Task Force on Preventive Health Care has recommended that obesity prevention be a high priority for health professionals. Changing your diet by reducing caloric intake, saturated fats, and cholesterol, and eating more nutritious foods (quality Calories), and concurrently initiating and continuing a good aerobic- and resistance-type exercise program are considered to be two steps toward positive health and the prevention of obesity. James Hill, founder of the obesity-prevention program America on the Move, indicated that walking an extra 2,000 steps a day and eat-

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C H A P T E R 1 1 Weight Maintenance and Loss through Proper Nutrition and Exercise

300 Calorie milkshake =

3 mile brisk walk at 3.5 mph (50 minutes)

or

35 minutes of recreational singles tennis

or

7 miles of leisurely bicycling at 10 mph (40 minutes)

F I G U R E 1 1 . 1 6 It is very easy to consume 300 additional Calories per day, which can lead to an increase of about 2.5 pounds of body fat per month. However, increased physical activity may help to expend these Calories (170-pound individual).

ing 100 fewer Calories will help prevent the average weight gain of 1–3 pounds per year. If you like to eat, additional exercise may help you burn these Calories and maintain your body weight (figure 11.16). Although most of this chapter has focused on treatment programs for the reduction of excess body fat, the same guidelines may be applied to a prevention program. Obesity in our society is a serious medical problem of epidemic proportions. Although treatment programs for the clinically obese may be successful on a short-term basis, unfortunately much of the weight loss is regained by the vast majority of those treated. As noted by Levin, the formation of neural circuits in the brain that help perpetuate maintenance of excess body weight are not easily abolished. We need to have strong prevention programs, particularly for children and adolescents, for this appears to be the time of life when chronic cases of obesity develop. Prevention of obesity on a large scale necessitates a multipronged effort involving various groups. Some examples are listed. • Government can set standards for food advertisements to children. • Food manufacturers could produce healthier products. One example is Fun Fruits, containing a variety of fruits and marketed specifically to kids. • Communities could plan more bike paths, playgrounds, and recreation centers. • Schools could schedule daily physical education classes and provide opportunities for students to participate in intramural

sports and physical activity clubs after school. Schools could also provide healthier products in vending machines. • Parents could provide healthy foods and limit sedentary behaviors such as TV and computer time. Various Websites to obtain helpful information relative to the prevention of obesity have been listed throughout this chapter, several of which have been recommended by the Consumers Union. It is incumbent upon those involved with the food habits and physical activity of our youth, notably parents and health and physical educators, to instruct and motivate them toward sound health habits. According to the American Medical Association, prevention is the treatment of choice in dealing with obesity. The bottom line is, we need to eat less and move more. www.win.niddk.nih.gov An excellent source of information is the Weight-Control Information Network (WIN).

Ke y C o n c e p t s 䉴 Although diet and exercise may each be effective in losing body

weight, a combination of the two would be even more beneficial. 䉴 Prevention of obesity is more effective than treatment, and

appropriate programs should be developed early for children and adolescents.

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A P P L I C AT I O N Albert is overweight by 25 pounds and is very serious about reducing his body weight from 200 pounds down to 175 and a healthier BMI of 22. He is currently sedentary, is consuming an average 3,600 Calories per day, and is still gaining weight. You may assume he needs 15 Calories per pound body weight to maintain his current weight. Using information presented in the text, develop a weight-loss program for Albert. Calculate an appropriate rate of weight loss per week. Based on your calculation, determine the daily caloric deficit needed to achieve his goal. The caloric deficit should incorporate reduced caloric energy intake and increased caloric energy expenditure through your recommended energy program. Once Albert is at his desired body weight and is involved in your exercise program, how many Calories may he consume daily to maintain that weight?

E X E R C I S E Albert’s Weight Status Weight

Calorie intake

Maintenance calories

Current status Goal status Albert’s Weight-Loss Plan 1. Desired weight loss per week: 2. Caloric energy intake reduction: 3. Caloric energy expenditure increase: 4. Total daily caloric deficit: 5. Maintenance Calories at goal weight:

Review Questions—Multiple Choice 1. If you were to design an aerobic training program for a 30-year-old individual and wanted that person to maintain an exercise intensity of 60–80 percent of the predicted HR max (traditional method) as the target heart rate range, what exercise heart rate range would you recommend? (a) 114–152 (b) 132–176 (c) 140–180 (d) 154–198 (e) 180–220 2. Which of the following statements relative to an exercise program for weight maintenance or loss is true? (a) The mode of exercise should involve large muscle groups that are activated in rhythmic, continuous type movement. (b) The higher the intensity of aerobic exercise that the individual can sustain, the better, because the greater the intensity, the greater the number of Calories burned per minute. (c) The greater the duration of activity, the better. 492

(d) The more frequent the exercise during the week, the better. (e) All statements are true. 3. Which of the following has the least amount of Calories as per the food exchange system developed by the American Dietetic Association and the American Diabetes Association? (a) three servings of skim milk (b) four servings of lean meat such as turkey (c) five servings of vegetables (d) four servings of fruit (e) one serving of whole milk 4. Aerobic-type exercise may be an effective part of a comprehensive weight control program for all of the following reasons except which one? (a) It increases the metabolic rate. (b) It mobilizes and utilizes free fatty acids from the adipose tissues. (c) It helps reduce body water stores. (d) It will increase the resting metabolic rate for 30 minutes or so after the exercise period.

C H A P T E R 1 1 Weight Maintenance and Loss through Proper Nutrition and Exercise

(e) It may help to curb the appetite in some individuals if done prior to mealtime. 5. Suppose a young sedentary woman wanted to lose 5 pounds of body fat in a period of 5 weeks’ time. She now weighs 150 pounds and her activity level is so low that she needs only 13 Calories per pound of body weight to maintain her weight. Calculate the number of Calories she may consume daily in order to lose the 5 pounds by diet only. (a) 800 (b) 1,250 (c) 1,450 (d) 1,750 (e) 1,950 6. In the exchange lists, high-fat foods are usually found in which two exchanges? (a) fruit and vegetables (b) starch/bread and lean meat (c) whole milk and starch/bread (d) fat and vegetable (e) medium fat meat and whole milk 7. Research with effective dieters has shown that in order to be successful, a diet should

(c) an increased use of carbohydrate stores and retention of body water (d) a decreased BMR and an increased loss of body-water stores (e) an increased BMR and decreased use of body-fat stores 9. Which of the following substitutes would not save Calories in a diet plan? (a) skim milk in place of whole milk (b) regular hard-stick margarine in place of butter (c) plain yogurt in place of sour cream on a baked potato (d) nonalcoholic beer in place of regular beer (e) air-popped popcorn in place of potato chips

10. An example of a behavior-modification program for a weight-loss program is (a) Feel guilty after you overeat. (b) Eat fast so there is no visible food to tempt you to eat more. (c) Keep a record of your eating habits so you can see what situations cause you to overeat. (d) Always clean your plate when you eat. (e) Always wait until you are hungry to go food shopping.

Answers to multiple choice questions: 1. a; 2. e; 3. c; 4. c; 5. c; 6. e; 7. c; 8. b; 9. b; 10. c.

follow all the following principles except which? (a) be low in Calories (b) supply all essential nutrients (c) contain bland foods to curb the intake of Calories (d) be able to be accommodated within one’s current lifestyle (e) be a lifelong diet 8. The rate of weight loss on an appropriate low-Calorie diet may be rapid at first, but then may slow down. This decreased rate of weight loss is most likely due to: (a) an increased BMR and increased use of body-protein stores (b) a decrease in body weight and increased use of body-fat stores

Review Questions—Essay 1. Melinda wants to lose 30 pounds by summer, which is 20 weeks away. She currently weighs 150 pounds and is maintaining her body weight with an energy intake of 14 Calories per pound body weight. Based on dietary changes only, calculate her daily energy needs during the first week of the diet if she wants to lose weight at a steady level over the 20-week period. 2. Explain the concept of behavior modification in a weight-loss program, and

describe some of the strategies one might employ to help change undesirable behaviors. 3. Discuss the positives and negatives of the high-carbohydrate, low-fat diet and the high-protein, high-fat, lowcarbohydrate diet. What appears to be the key factor underlying the potential success of each on a short-term basis? 4. Discuss the importance of mode, intensity, duration, and frequency of exercise in a weight-loss program, and provide an

example of an appropriate program incorporating each for a physically fit individual who wanted to lose one pound per week through exercise alone. 5. Both dieting and exercise may be helpful in a weight-loss program, but each may possess some drawbacks. Explain how the benefits of exercise may help counteract the possible drawbacks of dieting, and vice versa.

References Books Agatston, A. 2003. The South Beach Diet. Emmaus, PA: Rodale Press. American Diabetes Association and American Dietetic Association. 1995. Exchange Lists for Meal Planning. Chicago: American Dietetic Association and American Diabetes Association. Atkins, R. C. 1999. Dr. Atkins’ New Diet Revolution: Revised and Updated. New York: M. Evans. Brownell, K. 2004. The LEARN Program for Weight Management. Dallas, TX: American Health Publishing Company. Cooper, K. 1982. The Aerobics Program for Total Well-Being. New York: M. Evans. Dusek, D. 1989. Weight Management: The Fitness Way. Boston: Jones and Bartlett. Institute of Medicine. 1994. Weighing the Options: Criteria for Evaluating Weight Management

Programs. Washington, DC: National Academy Press. Katzen, M., and Willett, W. 2006. Eat, Drink, & Weigh Less. New York: Hyperion. Mayer, J. 1968. Overweight: Causes, Cost and Control. Englewood Cliffs, NJ: Prentice-Hall. Miller, W. 1998. Negotiated Peace. How to Win the War Over Weight. Boston: Allyn and Bacon. National Academy of Sciences. 2002. Dietary Reference Intakes for Energy, Carbohydrates, Fiber, Fat, Protein and Amino Acids (Macronutrients). Washington, DC: National Academy Press. Ornish, D. 2001. Eat More, Weigh Less: Dr. Dean Ornish’s Life Choice Program for Losing Weight Safely While Eating Abundantly. New York: HarperCollins Publishers. Pritikin, R. 2000. The Pritikin Principle. Alexandria, VA: Time-Life Books.

Roizen, M., and Oz, M. 2006. You on a diet—The Owner’s Manual to Waist Management. New York: Free Press. Rolls, B. 2005. The Volumetrics Eating Plan. New York: HarperCollins. Sears, B. 1995. The Zone. New York: Regan Books. Shils, M., et al. 2006. Modern Nutrition in Health and Disease. Philadelphia: Lippincott Williams & Wilkins. Taubes, G. 2007. Good Calories, Bad Calories: Challenging the Conventional Wisdom on Diet, Weight Control, and Disease. New York: Alfred A. Knopf. U.S. Department of Health and Human Services. Public Health Service. 1996. The Surgeon General’s Report on Physical Activity and Health. Washington, DC: U.S. Government Printing Office.

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Wansink, B. 2007. Mindless Eating: Why We Eat More Than We Think. New York: Bantam Books. Young, L. 2006. The Portion Teller Plan: The NoDiet Reality Guide to Eating, Cheating and Losing Weight Permanently. New York: Morgan Road Books.

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Westerterp-Plantenga, M., and Lejeune, M. 2005. Protein intake and body-weight regulation. Appetite 45:187–90. Whigham, L., et al. 2007. Efficacy of conjugated linoleic acid for reducing fat mass: A metaanalysis in humans. American Journal of Clinical Nutrition 85:1203–11. Williams, M. 2008. Nutrition for the school aged child athlete. In The Young Athlete, eds. H. Hebestreit and O. Bar-Or. Oxford: Blackwell Publishing. Wing, R., and Phelan, S. 2005. Long-term weight maintenance. American Journal of Clinical Nutrition 82:222S–25S. Winkler, J. 2005. The fundamental flaw in obesity research. Obesity Reviews 6:199–202. Wood, P. 1996. Clinical applications of diet and physical activity in weight loss. Nutrition Reviews 54:S131–S135. Wylie-Rosett, J., et al. 2004. Carbohydrates and increases in obesity: Does the type of carbohydrate make a difference? Obesity Research 12:124S–29S.

Specific Studies Adams, T., et al. 2007. Long-term mortality after gastric bypass surgery. New England Journal of Medicine 357:753–61. Arciero, P., et al. 2006. Increased dietary protein and combined high intensity aerobic and resistance exercise improves body fat distribution and cardiovascular risk factors. International Journal of Sport Nutrition and Exercise Metabolism 16:373–92. Azadbakht, L., et al. 2007. Better dietary adherence and weight maintenance achieved by a long-term moderate-fat diet. British Journal of Nutrition 97:399–404. Benezra, L., et al. 2001. Intakes of most nutrients remain at acceptable levels during a weight management program using the food exchange system. Journal of the American Dietetic Association 101:554–61. Browning, R., and Kram, R. 2007. Effects of obesity on the biomechanics of walking at different speeds. Medicine & Science in Sports & Exercise 39:1632–41. Bryner, R. W., et al. 1999. Effects of resistance vs aerobic training combined with an 800 calorie liquid diet on lean body mass and resting metabolic rate. Journal of the American College of Nutrition 18:115–21. Cotton, J., et al. 1996. Replacement of dietary fat with sucrose polyester: Effects on energy intake and appetite control in nonobese males. American Journal of Clinical Nutrition 63:891–96. Dansinger, M., et al. 2005. Comparison of the Atkins, Ornish, Watchers, and Zone diets for weight loss and heart disease risk reduction: A randomized trial. JAMA 293:43–53. Das, S., et al. 2007. Long-term effects of 2 energyrestricted diets differing in glycemic load on dietary adherence, body composition, and metabolism in CALERIE: A 1-y randomized controlled trial. American Journal of Clinical Nutrition 85:1023–30.

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Dich, J., et al. 2000. Effects of excessive isocaloric intake of either carbohydrate or fat on body composition, fat mass, de novo lipogenesis and energy expenditure in normal young men. Ugeskrift for Laeger 162:4794–99. Dolezal, B. A., and Potteiger, J. A. 1998. Concurrent resistance and endurance training influence basal metabolic rate in nondieting individuals. Journal of Applied Physiology 85:695–700. Ebbeling, C., et al. 2007. Effects of a low-glycemic load vs low-fat diet in obese young adults: A randomized trial. Journal of the American Medical Association 297:2092–102. Ello-Martin, J., et al. 2007. Dietary energy density in the treatment of obesity: A year-long trial comparing 2 weight-loss diets. American Journal of Clinical Nutrition 85:1465–77. Foster, G., et al. 2003. A randomized trial of a lowcarbohydrate diet for obesity. New England Journal of Medicine 348:2082–90. Foster-Schubert, K., et al. 2005. Human plasma ghrelin levels increase during a one-year exercise program. Journal of Clinical Endocrinology and Metabolism 90:820–25. Franco, O., et al. 2005. Effects of physical activity on life expectancy with cardiovascular diseases. Archives of Internal Medicine 165:2355–60. Gardner, C., et al. 2007. Comparison of the Atkins, Zone, Ornish, and LEARN diets for change in weight and related risk factors among overweight premenopausal women: The A TO Z Weight Loss Study: A randomized trial. Journal of the American Medical Association 297:969–77. Grediagin, M., et al. 1995. Exercise intensity does not effect body composition change in untrained, moderately overfat women. Journal of the American Dietetic Association 95:661–65. Hall, C., et al. 2004. Energy expenditure of walking and running: Comparison with prediction equations. Medicine & Science in Sports & Exercise 36:2128–34. Hansen, D., et al. 2007. The effects of exercise training on fat-mass loss in obese patients during energy intake restriction. Sports Medicine 37:31–46. Haus, G., et al. 1994. Key modifiable factors in weight maintenance: Fat intake, exercise, and weight cycling. Journal of the American Diebetic Association 94:409–13. Howard, B., et al. 2006. Low-fat dietary pattern and weight change over 7 years: The Women’s Health Initiative Dietary Modification Trial. Journal of the American Medical Association 295:39–49. Hultquist, C., et al. 2005. Comparison of walking recommendations in previously inactive women. Medicine & Science in Sports & Exercise 37:676–83. Jakicic, J., et al. 1995. Prescribing exercise in multiple short bouts versus one continuous bout: Effects on adherence, cardiorespiratory fitness, and weight loss in overweight women. International Journal of Obesity and Related Metabolic Disorders 19:893–901. Johnston, C., et al. 2004. High-protein, low-fat diets are effective for weight loss and favorably alter biomarkers in healthy adults. Journal of Nutrition 134:586–91.

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Johnston, C., et al. 2002. Postprandial thermogenesis is increased 100% on high-protein, low-fat diet versus a high-carbohydrate, low-fat diet in healthy, young women. Journal of the American College of Nutrition 21:55–61. Kostek, M., et al. 2007. Subcutaneous fat alterations resulting from an upper-body resistance training program. Medicine & Science in Sports & Exercise 39:1177–85. Kraemer, W. J., et al. 1999. Influence of exercise training on physiological and performance changes with weight loss in men. Medicine & Science in Sports & Exercise 31:1320–29. Layman, D., et al. 2005. Dietary protein and exercise have additive effects on body composition during weight loss in adult women. Journal of Nutrition 135:1903–10. Ledikwe, J., et al. 2007. Exercise effect on weight and body fat in men and women. Obesity 15:1496–512. Leidy, H., et al. 2007. Effects of acute and chronic protein intake on metabolism, appetite, and ghrelin during weight loss. Obesity 15:1215–25. Leidy, H., et al. 2007. Higher protein intake preserves lean mass and satiety with weight loss in pre-obese and obese women. Obesity 15:421–29. Linde, J., et al. 2005. Self-weighing in weight gain prevention and weight loss trials. Annals of Behavioral Medicine 7:1–14. Ludwig, D., et al. 2001. Relation between consumption of sugar-sweetened drinks and childhood obesity: A prospective, observational analysis. Lancet 357:505–8. Ma, Y., et al. 2007. A dietary quality comparison of popular weight-loss plans. Journal of the American Dietetic Association 107:1786–91. Martins, C., et al. 2007. Effects of exercise on gut peptides, energy intake and appetite. Journal of Endocrinology 193:251–58. Melanson, E., et al. 2002. Effect of exercise intensity on 24-h energy expenditure and nutrient oxidation. Journal of Applied Physiology 92:1045–52. Miller, W., et al. 1993. Cardiovascular risk reduction in a self-taught, self-administered weight loss program called the nondiet diet. Medicine & Science in Sports & Exercise 25:218–23. Moloney, F., et al. 2004. Conjugated linoleic acid supplementation, insulin sensitivity, and lipoprotein metabolism in patients with type 2 diabetes mellitus. American Journal of Clinical Nutrition 80:887–95. Murphy, M., et al. 2002. Accumulating brisk walking for fitness, cardiovascular risk, and psychological health. Medicine & Science in Sports & Exercise 34:1468–74. Newman, B., et al. 1990. Nongenetic influences of obesity on other cardiovascular disease risk factors: An analysis of identical twins. American Journal of Public Health 80:675–78. Persinger, R., et al. 2004. Consistency of the Talk Test for exercise prescription. Medicine & Science in Sports & Exercise 36:1632–36. Pritchard, J., et al. 1997. A worksite program for overweight middle-aged men achieves lesser weight loss with exercise than with dietary

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change. Journal of the American Dietetic Association 97:37–42. Puthoff, M., et al. 2006. The effect of weighted vest walking on metabolic responses and ground reaction forces. Medicine & Science in Sports & Exercise 38:746–52. Raben, A., et al. 2002. Sucrose compared with artificial sweeteners: Different effects on ad libitum food intake and body weight after 10 wk of supplementation in overweight subjects. American Journal of Clinical Nutrition 76:721–29. Redman, L., et al. 2007. Effect of calorie restriction with or without exercise on body composition and fat distribution. Journal of Clinical Endocrinology & Metabolism 92:865–72. Romijn, J., et al. 2000. Substrate metabolism during different exercise intensities in endurance-trained women. Journal of Applied Physiology 88:1707–14. Samaras, K., et al. Genetic and environmental influences on total-body and central abdominal fat: The effect of physical activity in female twins. Annals of Internal Medicine 130:873–82. Sedlock, D., et al. 1989. Effect of exercise intensity and duration on postexercise energy expenditure. Medicine & Science in Sports & Exercise 21:662–66. Shai, I., et al. 2008. Weight loss with a lowcarbohydrate, Mediterranean, or low-fat diet. New England Journal of Medicine 359:229–41. Shide, D., and Rolls, B. 1995. Information about the fat content of preloads influences energy intake in healthy women. Journal of the American Dietetic Association 95:993–98. Sillanpää, E., et al. 2008. Body composition and fitness during strength and/or endurance training in older men. Medicine & Science in Sports & Exercise 40:950–58. Sjodin, A., et al. 1996. The influence of physical activity on BMR. Medicine & Science in Sports & Exercise 28:85–91. Sjöström, L., et al. 2007. Effects of bariatric surgery on mortality in Swedish obese subjects. New England Journal of Medicine 357:741–52. Stubbs, R., et al. 2004. A decrease in physical activity affects appetite, energy, and nutrient balance in lean men feeding ad libitum. American Journal of Clinical Nutrition 79:62–69. Tate, D., et al. 2007. Long-term weight losses associated with prescription of higher physical activity goals. Are higher levels of physical activity protective against weight regain? American Journal of Clinical Nutrition 85:954–59. Thompson, D., et al. 2004. Relationship between accumulated walking and body composition in middle-aged women. Medicine & Science in Sports & Exercise 36:911–14. Thompson, D., et al. 1988. Acute effects of exercise intensity on appetite in young men. Medicine & Science in Sports & Exercise 20:222–27. Truby, H., et al. 2006. Randomized controlled trial of four commercial weight loss programmes in the UK: Initial findings from the BBC “diet trials.” British Medical Journal 332:1309–14.

Utter, A., et al. 2006. Validation of Omni Scale of Perceived exertion during prolonged cycling. Medicine & Science in Sport & Exercise 38:780–86. Vander Wal, J., et al. 2005. Short-term effect of eggs on satiety in overweight and obese subjects. Journal of the American College of Nutrition 4:510–15.

Weigle, D., et al. 2005. A high-protein diet induces sustained reductions in appetite, ad libitum caloric intake, and body weight despite compensatory changes in diurnal plasma leptin and ghrelin concentrations. American Journal of Clinical Nutrition 82:41–48.

Westman, E., et al. 2002. Effect of a 6-month adherence to a very low carbohydrate diet program. American Journal of Medicine 113:30–36. Zeni, A., et al. 1996. Energy expenditure with indoor exercise machines. Journal of the American Medical Association 275: 1424–27.

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T E R M S

circuit aerobics 519 circuit weight training 519 concentric method 516 eccentric method 516 isokinetic method 516 isometric method 516 isotonic method 516 muscle hypertrophy 515 periodization 508 repetition maximum (RM) 505 sarcopenia 519 strength-endurance continuum 505 Valsalva phenomenon 512

CHAPTER TWELVE L E A R N I N G

O B J E C T I V E S

After studying this chapter, you should be able to: 1. Describe the steps an individual might take in order to gain body weight, mainly as muscle mass. 2. Plan a diet for an individual who desires to gain muscle mass in concert with a resistance-training program, focusing on recommended caloric intake and foods compatible with the Prudent Healthy Diet. 3. Identify dietary supplements used by physically active individuals to stimulate muscle building and body-fat loss, and list those, if any, which may be effective. 4. List and explain the principles of resistance training. 5. Understand the basic differences among resistance-training programs for muscular hypertrophy, muscular strength and power, and muscular endurance. 6. Design a total-body resistance-training program for an individual who desires to gain body weight as muscle mass. 7. Identify the potential health benefits of resistance exercise and compare them to the health benefits associated with aerobic endurance exercise, noting similarities and differences.

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Introduction As noted in the previous chapter, there are basically three reasons why individuals attempt to lose excess body weight—to improve appearance, health, or athletic performance. Some individuals may also wish to gain weight for the same three reasons, and may use resistance training, also known as weight training or strength training, as a means to stimulate weight gain. For those who wish to improve appearance, resistance training will increase muscularity, a desired physical attribute among many males. Resistance training is becoming increasingly popular, particularly among women. Based on epidemiological studies, Galuska and others estimated that almost 9 percent of American adults age 17 and over engage in regular weight training, nearly 13 percent of males and 5 percent of females. Gaining weight, particularly muscle mass stimulated by resistance training, may also be associated with some health benefits. An increased muscularity that improves physical appearance and body image may help elevate selfesteem, contributing to positive psychological health. Additionally, resistance training, done alone even without weight gain, is recommended for several other health benefits, such as increased bone mineral density. The American Heart Association and the American College of Sports Medicine, in their recent reports on physical activity and health, recommend resistance exercise as an effective means to promote overall good health. Resistance training is particularly recommended for older adults to help prevent the muscle wasting, and associated health problems, seen with aging. A popular book, Quick Weight-Gain Program by Dr. David Reuben has been designed to provide sound medical advice for the 26 million Americans who need to gain weight for a variety of medical and cosmetic reasons.

Increased body weight, particularly increased muscle mass, may be associated with improvements in strength and power, two performance factors important for a wide variety of sports. Enhanced muscularity also may influence performance in judged aesthetic sports, such as diving and gymnastics. Most colleges and universities, as well as many high schools, have strength-training programs for their athletes, both males and females. At the elite level, sport-specific resistance-training programs are tailored to the individual athlete. No matter what the reason for gaining body weight, you should be concerned about where the extra pounds will be stored. The energy-balance equation works equally as well for gaining weight as it does for losing weight, but excess body fat in general will not improve physical appearance, health, or athletic performance. On the contrary, it may detract from all three. To put on body weight, you have to concentrate on means to increase the fat-free mass, particularly muscle tissue, with little or no increase in body-fat stores. Rasmussen and Phillips note that resistance exercise and nutritional provision are two independent and major stimuli of muscle protein synthesis and overall muscle growth, and numerous related approaches have been employed to increase muscle mass. Specialized exercise equipment or exercise techniques are advertised as the most effective methods available to build muscles. Protein supplements have been a favorite among weight lifters for years,

but today athletes can buy numerous dietary supplements that are advertised to produce an anabolic, or musclebuilding, effect. Some athletes and nonathletes even use drugs to gain weight for enhanced performance or appearance, a topic that is discussed in chapter 13. Although resistance training may confer significant health benefits, Pope indicated some very muscular individuals have a distorted body image, perceiving themselves as too thin or not sufficiently muscular, which he labeled as muscle dysmorphia or the Adonis Complex. Grieve noted that muscle dysmorphia is most prevalent in males, but shares similar characteristics, such as low self-esteem, body dissatisfaction, and perfectionism, observed in females with eating disorders. Muscle dysmorphia may lead to unhealthful practices, such as the use of drugs, to enhance muscularity. Interestingly, Pickett and others reported that muscle dysmorphia is not confined to competitive bodybuilders, but is also found in noncompetitive weight trainers and even physically active men who do not train with weights. Like weight-loss programs, weightgaining programs may be safe and effective or they can be potentially harmful to your health. Although gaining weight, particularly as muscle mass, is difficult for some individuals, the purpose of this chapter is to present basic information on the type of diet and exercise program that is most likely to be effective as a means to put on weight without compromising your health.

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Basic Considerations Why are some individuals underweight? Being significantly under a healthy body weight may be due to several factors. Heredity may be an important factor, as genetic factors may predispose some individuals to leanness. For example, a lean body frame or high basal metabolic rate may have been acquired through your parents. Medical problems such as heartburn, infections, or cancer could adversely affect food intake and digestion, so a physician should be consulted to rule out nutritional problems caused by organic disease, hormonal imbalance, or inadequate absorption of nutrients. Social pressures, such as the strong desire of a teenage girl to have a slender body, could lead to undernutrition; an extreme example is anorexia nervosa, discussed in chapter 10. Emotional problems also may affect food intake. In many cases, food intake is increased during periods of emotional crisis, but the appetite may also be depressed in some individuals for long periods. Economic hardships may reduce food purchasing power, so some individuals simply may sacrifice food intake for other life necessities. Being considerably underweight, such as a Body Mass Index below 18.5, may be considered a symptom of malnutrition or undernutrition. It is important to determine the cause before prescribing a treatment. Our concern here is the individual who does not have any of these medical, psychological, social, or economic problems but who simply cannot create a positive energy balance because of excess energy expenditure or insufficient energy (Calorie) intake. Caloric intake has to be increased, and the output has to be modified somewhat.

What steps should I take if I want to gain weight? The following guidelines may help you develop an effective program to maximize your gains in muscle mass and keep body-fat increases relatively low. 1. Have an acceptable purpose for the weight gain. The desire for an improved physical appearance and body image may be reason enough. For athletes, increased muscle mass may be important for a variety of sports, particularly if strength and power are improved. However, you do not want to gain weight at the expense of speed if speed is important to your sport. 2. Calculate your average energy needs daily as discussed in chapter 11. For a weight-gain program, you may wish to use several techniques to estimate your daily energy needs and select the highest value. 3. Keep a 3- to 7-day record of what you normally eat. See pages 458–461 for guidelines to determine your average daily caloric intake. If the obtained value is less than your energy needs calculated under item 2 in this list, this may be a reason why you are not gaining weight. 4. Check your living habits. Do you get enough rest and sleep? If not, you may be burning more energy than the estimate in item 500

5.

6.

7.

8.

2 of this list. Smoking increases your metabolic rate almost 10 percent and may account for approximately 200 Calories per day. Caffeine in coffee and soft drinks also increases the metabolic rate for several hours. Getting enough rest and sleep and eliminating smoking and caffeine will help decrease your energy output. Set a reasonable goal within a certain time period. Weight gain may be rapid at first but then tapers off as one nears his or her genetic potential. Peter Lemon, an expert in resistance training and protein metabolism, indicated that someone starting a resistance-training program may increase body mass by 20 percent in the first year. After that, gains are somewhat less, possibly only 1–3 percent per year. In general, about 0.5–1 pound per week is a sound approach for a novice, but weight gaining is difficult for some individuals and may occur at a slower rate. Specific goals may also include muscular hypertrophy in various parts of the body. Increase your caloric intake. A properly designed diet should include adequate Calories and protein and not violate the principles of healthful nutrition. Start a resistance-training exercise program. This type of exercise program will serve as a stimulus to build muscle tissue. Guidelines for developing a resistance-training program are presented later in this chapter. Use a good cloth or steel tape to take body measurements before and during your weight-gaining program. Be sure you measure at the same points about once a week. Those body parts measured should include the neck, upper and lower arm, chest, abdomen, hips, thigh, and calf. This is to ensure that body-weight gains are proportionately distributed. You should look for good gains in the chest and limbs; the abdominal and hip girth increase should be kept low because that is where fat is more likely to be stored. If available, skinfold calipers may be used to measure subcutaneous fat skinfolds at multiple sites over the body. Fat skinfold thicknesses should remain the same or decrease to ensure that the weight gain is muscle not fat.

In summary, adequate rest, increased caloric intake, and a proper resistance-training program may be very effective as a means to gain the right kind of body weight.

Ke y C o n c e p t s 䉴 There may be a variety of reasons why an individual is

underweight, and the cause should be determined before a treatment is recommended. 䉴 For those who want to gain weight, a weekly increase of 0.5–1.0 pound is a sound approach, but the desired weight gain should be muscle tissue and not body fat. In essence, adequate rest and sleep, increased caloric intake, and a proper resistance-training program should be effective in helping to increase lean body mass.

C H A P T E R 1 2 Weight Gaining through Proper Nutrition and Exercise

Nutritional Considerations In the last chapter we discussed nutritional considerations for losing body weight, particularly body fat. In general, the recommendation consists of a healthy diet but with reduced caloric intake. In this chapter we consider nutritional considerations for gaining body weight, particularly lean body mass as muscle. In this case the recommendation still is to eat a healthy diet, but with increased caloric intake. Gaining weight as muscle mass may be difficult for some. Resistance training, discussed later in this chapter, is important to help stimulate muscle growth so extra Calories are used to develop muscle, not fat. As noted, gaining about 0.5–1.0 pound per week is a reasonable goal, although some may be able to gain more.

How many Calories are needed to form one pound of muscle? Muscle tissue consists of about 70 percent water, 22 percent protein, and the remainder is fat, carbohydrate, and minerals. Because the vast majority of muscle tissue is water, which has no caloric value, the total caloric value is only about 700–800 Calories per pound. However, extra energy is needed to help synthesize the muscle tissue. It is not known exactly how many additional Calories are necessary to form 1 pound of muscle tissue in human beings, nor is it known in what form these Calories have to be consumed. The National Research Council notes that 5 Calories are needed to support the addition of 1 gram of tissue during growth, while Forbes cites a value of 8 Calories per gram in adults. Because 1 pound equals 454 grams, a range of 2,300–3,500 additional Calories appears to be a reasonable amount. With a recommended weight gain of 1 pound per week, about 400–500 Calories above your daily needs would provide an amount in the suggested range, 2,800–3,500 Calories per week. A study by Robert Bartels and his associates at Ohio State University revealed that an additional 500 Calories per day resulted in nearly a 1-pound increase in lean body weight per week during a resistance-training program. For our purposes, we shall consider 3,500 Calories as the weekly excess energy intake necessary to support an increase in 1 pound of muscle tissue.

How can I determine the amount of Calories I need daily to gain one pound per week? First, review the techniques presented in chapter 11 to determine the number of Calories needed simply to maintain your current body weight. Then add the Calories that you expend during exercise and the additional amount needed to synthesize the muscle tissue. Table 12.1 presents an example of a 154-pound 18-year-old male who desires to gain a pound per week. You may modify the figures according to your own needs. You can use the MyPyramid Website to plan a weight-gain diet as well as a weight-loss diet. Remember, a weight gain of 0.5–1.0 pound muscle mass per week is a reasonable goal during the early stages of resistance training. If you are maintaining your weight with your current dietary intake, adding 500 Calories per day may also be an acceptable approach.

TABLE 12.1 Caloric intake for a 154-pound 18-year-old

male to gain one pound per week

Energy expenditure

Daily Calories needed

Recommended caloric intake to maintain current weight 19 Calories/pound

2,468

Resistance training 200 Calories per session 4 sessions per week 800/7

115

Aerobic exercise 300 Calories per session 4 sessions per week 1,200/7

170

Muscle tissue synthesis 3,500 Calories per pound 3,500/7

500

Total daily caloric intake

3,253

Increased caloric intake is the key dietary principle, along with adequate protein intake, to gain mass during resistance training, as noted in a Gatorade Sports Science Institute review of weight-gain strategies in athletes by leading experts in the area, Gail Butterfield, Susan Kleiner, Peter Lemon, and Michael Stone.

Is protein supplementation necessary during a weight-gaining program? Gilbert Forbes indicates we need adequate amounts of protein to support increases in lean body mass. One pound of muscle is equal to 454 grams, but only about 22 percent of this tissue, or about 100 grams, is protein. If we divide 100 grams by 7 days, we would need approximately 14 grams of protein per day above our normal protein requirements to gain one pound of muscle per week if we are in protein balance. However, the average American diet already contains extra protein beyond the RDA, so this need probably is satisfied. Incidentally, 14 grams of protein could be obtained in such small amounts of food as 2 glasses of milk, 2 ounces of cheese, 2 scrambled eggs, or 2 ounces of meat, fish, or poultry (see figure 12.1). Although the daily RDA for protein is about 1 gram per kilogram body weight, some authorities in sports nutrition have recommended up to 1.6–1.7 grams per kilogram for the athlete who is training to increase muscle mass. As noted in chapter 6, a slight increase in the protein content of the typical American daily diet would meet even this recommendation. A brief review of the mathematics in table 6.6 and the related discussion on pages 224–227 will help substantiate this statement. These recommendations are also consistent with those proposed by Phillips, who indicated that strength-trained athletes should consume protein consistent with general population guidelines, or about 12–15 percent of energy from protein. www.mhhe.com/williams9

501

=

+

+

1 pound of muscle tissue/week = Additional 400 Calories/day + Additional 14 grams protein/day

F I G U R E 1 2 . 1 To add a pound of muscle tissue per week, you need to consume approximately 400 additional Calories and 14 grams of additional protein per day. A weight-training program is an essential part of a muscle-building program. One glass of skim milk, three slices of whole wheat bread, and two hard-boiled egg whites provide the necessary Calories and about 23 grams of protein.

Supplementation by expensive protein powders or amino acids is not necessary. Review table 6.8 on page 229. The average American diet provides sufficient high-quality protein to meet the needs of a weight-gaining program, even more so if a high-Calorie diet is used as recommended in the following text. It is important to note that dietary protein in excess of needs will be converted to fat unless resistance training is used to stimulate muscle growth. High-quality protein may be important. In his review of nutrition for female strength athletes, Jeff Volek, a prominent strength researcher, indicated that athletes should focus on high-quality protein, which includes common foods such as milk and eggs. Campbell also noted that diets rich in high-quality protein may help older people engaged in resistance training retain or increase muscle mass. In a recent study, Wilkinson and others reported that protein from different sources may differ in their ability to support muscle protein synthesis. They found that skim milk-based protein promoted muscle protein synthesis to a greater extent than did soy-based protein. As noted in chapter 6, animal protein contains a better balance of essential amino acids than plant proteins. However, as discussed in chapter 6, consuming carbohydrate with protein and the timing of food intake may be an important consideration. Muscle protein synthesis is accelerated in the recovery period following resistance exercise, and in his review Houston indicated that consuming the additional dietary protein during recovery, along with carbohydrates, will create a hormonal response to further increase protein synthesis. However, in a recent review Kevin Tipton and Robert Wolfe, two experts on protein metabolism, have concluded that it has yet to be determined if these transient hormonal responses result in an appreciable increase in muscle mass over a prolonged training period. They suggested the possibility that these transient increases in anabolism add nothing to the normal anabolic responses that would result from meals ingested in the 24 hours following an appropriate resistance exercise workout. Subsequent to their review, Cribb and Hayes reported that consuming a protein/carbohydrate supplement, which also contained creatine, immediately before and after a resistance training workout, as contrasted to consuming the same supplement in the morning and evening, resulted in greater increases in lean body mass and strength testing, suggesting timing is important. Nevertheless, although additional research is needed to support a more positive recommendation, consuming a proteincarbohydrate mixture before and after resistance training may be prudent, as it may do some good and is unlikely to do any harm. Volek indicated that to date one of the most promising strategies to augment gains in muscle size appears to be consumption of pro502

tein/ carbohydrate Calories before and after resistance exercise. Recent studies by Andersen and Bo/ rsheim support this viewpoint. A tasty post-workout carbohydrate protein drink, with a ratio of 3–4 grams of carbohydrate for each gram of protein, has been recommended by Ivy and Portman. Both the carbohydrate and the protein will stimulate insulin secretion, which will help move both glucose and amino acids into the muscle to facilitate recovery and support muscle protein synthesis. One simple, convenient choice is chocolate milk; an 8-ounce glass contains about 32 grams of carbohydrate and 8 grams of protein, a 4:1 ratio (see figure 12.2). In some sports, such as bodybuilding, athletes not only want to gain muscle, but they want the musculature to be pronounced during aesthetic judging. In order to highlight muscle definition, subcutaneous fat must be reduced. Thus, such athletes may need to balance energy intake to sustain muscle growth and yet promote fat loss. In other words, they need to lose fat and maintain muscle mass at the same time, which may necessitate a weight-loss diet. In his review, Stuart Phillips from McMaster University in Canada, indicated that a number of well-controlled studies have shown that protein diets have been shown to be effective in promoting weight reduction, particularly fat loss. Such diets may contain greater amounts of protein than found in the typical diet, as much as 30–35 percent of energy, which is still within the Acceptable Macronutrient Distribution Range. Phillips notes that such diets may be relevant to athletes who want to lose fat and preserve lean body mass. A recent study by Pikosky and others supports this viewpoint. They reported that doubling the daily protein intake (0.9 g/kg to 1.8 g/kg) maintained mean nitrogen balance, or lean body mass, when losing weight by increased energy expenditure through exercise. Subjects consuming the lower amounts of protein experienced a decrease in nitrogen balance.

Are dietary supplements necessary during a weight-gaining program? Robert Keith, a sport nutrition professor at Auburn University, and his colleagues reported that the nutrient intakes of individuals, such as bodybuilders, attempting to gain muscle mass were well above recommended levels, indicating there probably would not be any advantage for these subjects to take nutrient supplements. However, dietary supplements appear to be very popular among athletes and others attempting to increase muscle mass and strength, if we can use advertisements as evidence to support this contention. For example, in a survey of only five magazines targeted to bodybuilding athletes, Grunewald and Bailey reported over

C H A P T E R 1 2 Weight Gaining through Proper Nutrition and Exercise

F I G U R E 1 2 . 2 Chocolate milk may be an excellent source of nutrients before or after a resistance-training workout. One glass provides about 32 grams of carbohydrate and 8 grams of protein, a 4:1 ratio. Chocolate milk also provides important minerals and vitamins as well.

800 performance claims were made for 624 commercially available supplements. This survey was conducted nearly 25 years ago, but such marketing practices continue unabated. Numerous products are marketed not only to increase muscle mass, strength, and power, but also to help prevent injuries during training. Bloomer notes that marketing of nutritional supplements for the purposes of attenuating muscle injury are rampant within the popular fitness media and athletic world, largely without scientific support. Although there may be some truth underlying the alleged performance-enhancing mechanisms of these supplements, the effectiveness of most has not been evaluated by scientific research. In a review of nutritional supplements for strength-trained athletes, Williams indicated that there is little or no scientific evidence supporting positive effects on muscle growth, body-fat reduction, or strength enhancement in strength-trained athletes for the following: arginine, lysine, and ornithine (amino acids); inosine; choline; yohimbine; glandular products; vitamin B12; carnitine; chromium; boron; magnesium; medium-chain triglycerides; omega-3 fatty

acids; gamma oryzanol; and Smilax. In general, these viewpoints were supported by Clarkson and Rawson, Coleman and others, and Kreider in their reviews. In his review of research with dietary supplements marketed to prevent muscle injuries, Bloomer concludes that because so few studies have been conducted in this area, it is difficult to recommend with confidence the use of selected nutrients for the sole purpose of minimizing signs and symptoms of resistance exercise-induced muscle injury, in particular with regard to resistance-trained individuals. Most of these nutrients and dietary supplements, and others such as vanadium and HMB, have been discussed in previous chapters and have been found to be ineffective or inadequately researched. As noted in chapter 6, creatine monohydrate supplementation does appear to increase body weight, and numerous studies have reported gains in strength, particularly in high-intensity resistance exercises with short-term recovery. Although early increases in body weight may be primarily water, an increased resistancetraining capacity may lead to muscle gains over time. Numerous studies support this finding. You may wish to review the discussion of creatine supplementation on pages 240–245. As shall be noted in the next section, resistance training is a very important consideration to help prevent or reduce loss of muscle mass in the elderly. In their recent review, Candow and Chilibeck reported that although resistance training has a positive effect on muscle mass in the elderly, nutrition is also important and creatine supplementation during resistance training may help increase muscle tissue synthesis. Several other dietary supplements marketed to athletes are patterned after anabolic/androgenic steroids. Some herbal products are marketed for their supposed anabolic potential. In general, as noted in chapter 13, research indicates such supplements do not increase muscle mass and may cause adverse health effects. In a symposium sponsored by the Gatorade Sports Science Institute, five experts on muscle-building supplements provided this advice: • Train hard • Follow a sound diet with adequate energy, protein, and carbohydrate • Don’t rely on dietary supplements If you do use supplements, be sure to consult with an expert, such as a sports-oriented dietitan or physician, not the clerk at a health food store. As indicated in chapter 1, many of these products are costly and some can have adverse effects on one’s health. Caveat emptor.

What is an example of a balanced diet that will help me gain weight? As with losing weight, the Food Exchange System may serve as the basis for a sound weight-gaining diet. Foods must be selected for high nutrient value as well as additional Calories to support the weight gain. The following suggestions may be helpful for those trying to gain weight as muscle. In general, the focus is on healthy dietary sources of carbohydrates, protein, and fats. Milk exchange—Drink 1% or 2% milk instead of skim milk, which will add 15–30 Calories per glass. Chocolate milk www.mhhe.com/williams9

503

provides both carbohydrate and high-quality protein. Prepare milk shakes with dry milk powder and supplement with fruit. Add low-fat cheeses to sandwiches or snacks. Eat yogurt supplemented with fruit. The milk exchange is high in protein. Meat and meat substitute exchange—Increase your intake of lean meats, poultry, and fish. Legumes such as beans and dried peas are high in protein, carbohydrate, and Calories and low in fat. Use nuts, seeds, and limited amounts of peanut butter for snacks. The meat exchange is also high in protein. Starch exchange—Increase your consumption of whole-grain products. Pasta and rice are nutritious side dishes that provide adequate Calories. Starchy vegetables like potatoes are also nutritious sources of Calories. Breads and muffins can possibly be supplemented with fruits and nuts. Whole-grain breakfast cereals can provide substantial Calories and even make a tasty dessert or snack with added fruit. The starch exchange is high in complex carbohydrates but also contains about 15 percent of its Calories as protein. Fruit exchange—Add fruit to other food exchanges. Drink more fruit juices, which are high in both Calories and nutrients. Dried fruits such as apricots, pineapple, dates, and raisins are high in Calories and make excellent snacks. Vegetable exchange—Use fresh vegetables like broccoli and cauliflower as snacks with melted low-fat cheese or a nutritious dip. Fat exchange—Try to minimize the intake of saturated fats, using monounsaturated and polyunsaturated fats instead, particularly olive and canola oils. Nuts and seeds are good sources of monounsaturated fats. Salad dressings and soft margarine added to vegetables can increase their caloric content. Beverages—Milk and juices are nutritious and high in Calories. Those who drink alcohol should obtain only limited amounts of Calories in this way. Some liquid supplements are available commercially and may contain 300–400 Calories with substantial amounts of protein. However, check the label for fat and sugar content. Snacks—Eat three balanced meals per day supplemented with two or three snacks. Dried fruits, nuts, and seeds are excellent snacks. Some of the high-Calorie, high-protein, high-nutrient liquid meals and sports bars on the market also make good snacks. Table 12.2 presents an example of a high-Calorie diet plan based upon the Food Exchange System. It consists of three main meals and three snacks and totals about 4,000 Calories with 160 grams of protein, which is 16 percent of the Calories. It is also high in carbohydrate, which may increase insulin release, facilitating amino acid transport into the muscle to help promote protein synthesis. Carbohydrate also spares the use of protein as an energy source. Alternative foods may be substituted from the food exchange list presented in appendix E. This suggested diet provides the necessary nutrients, Calories, and protein essential for increased development of muscle mass and yet fewer than 30 percent of the Calories are derived from fat. The total number of Calories can be adjusted to meet individual needs. You may plan your weight-gain diet on the MyPyramid Website. 504

TABLE 12.2 A high-Calorie diet based on

the Food Exchange System Exchange

Calories

Breakfast Milk Meat Starch Fruit Other

8 ounces 2% milk 1 poached egg 2 ounces lean ham 2 slices whole wheat toast 8 ounces orange juice 1 tablespoon jelly

120 80 110 160 120 50

8 ounces apricot nectar 2 slices whole wheat bread 1 tablespoon peanut butter

160 160 100

8 ounces 2% milk 4 ounces lean sandwich meat 2 slices whole wheat bread 2 granola cookies 1 banana 1 order French fries

120 220 160 100 120 300

1/4 cup raisins

120

8 ounces 2% milk 5 ounces salmon 2 slices whole wheat bread 1 piece apple pie 1 cup peas 1 sweet potato, candied

120 275 160 350 160 300

1/2 cup dried peaches 8 ounces 2% milk with banana

210 240

Mid-morning snack Fruit Starch Meat Lunch Milk Meat Starch Fruit Vegetable, starchy Afternoon snack Fruit Dinner Milk Meat Starch Fruit Vegetable, starchy

Evening snack Fruit Milk

Total

4,015

Meal plans may be adjusted to the energy needs of individual athletes. For example, Lambert and others note that competitive bodybuilders should consume a diet that contains about 55–60 percent carbohydrate, 25–30 percent protein, and 15–20 percent fat for both the off-season and pre-contest phases. However, during the off-season the diet should be slightly hyperenergetic (approximately 15 percent increase in energy intake) and during the precontest phase the diet should be hypoenergetic (approximately 15 percent decrease in energy intake). As noted previously, for 6–12 weeks prior to competition, bodybuilders attempt to retain

C H A P T E R 1 2 Weight Gaining through Proper Nutrition and Exercise

muscle mass and reduce body fat to low levels, so they need to be in negative energy balance to facilitate oxidation of body fat. Lambert and others recommend the diet contain 30 percent protein at this time to help prevent loss of muscle mass and possibly also provide a thermic effect to help burn fat. For more detailed meal plans, the interested reader is referred to Nutrient Timing by John Ivy and Robert Portman.

Would such a high-Calorie diet be ill advised for some individuals? As noted in chapter 5, one of the general recommendations for an improved diet is to reduce the consumption of fats, particularly saturated fats. Unfortunately, many high-Calorie diets are also high in fats. If there is a history of heart disease in the family or if an individual is known to have high blood lipid levels, then highfat diets may be contraindicated. Individuals with kidney problems also may have difficulty processing high-protein diets because of the increased need to excrete urea. Any person initiating such a weight-gaining program as advised here should be aware of his or her medical history. Selection of food for a weight-gaining diet, if done wisely, can satisfy the criteria for healthful nutrition. Foods high in complex carbohydrates with moderate amounts of protein and a moderate fat content are able to provide substantial amounts of Calories and nutrients and yet minimize health risks that have been associated with the typical American and Canadian diet. To gain weight wisely, you need to continue to eat healthful foods, but just more of them.

Ke y C o n c e p t s 䉴 The individual attempting to gain body weight should obtain

necessary protein for muscle synthesis through a well-balanced diet, rather than by consuming expensive protein supplements. 䉴 Although creatine supplementation may help increase muscle mass during resistance training, most dietary supplements marketed to strength-trained individuals are not effective or have not been evaluated by scientific research. 䉴 The Food Exchange System can serve as the basis for increasing caloric intake to gain body weight if the aspirant eats greater quantities of nutritious foods from each of the six lists, in three balanced meals plus several high-Calorie, high-nutrient snacks.

C h e c k f o r Yo u r s e l f Using the information presented in the text, calculate the additional number of Calories you would need in your daily diet to accumulate a weight gain of 0.5 pound per week. What foods could you add to your daily diet to provide these Calories?

Exercise Considerations In the last chapter we discussed the design of an aerobic exercise program for the loss of excess body fat but also mentioned that a resistance-training program could be helpful, for it might help pre-

vent the loss of lean body mass and maintain normal restingenergy expenditure. In this chapter the focus is upon resistance training, sometimes called weight training or strength training, as a means to increase lean body mass and body weight. Before we discuss the principles underlying the design of a proper resistancetraining program, let us introduce some basic terminology. Repetition simply means the number of times you do a specific exercise. Intensity is determined by the weight, or resistance, that is lifted. A term used to describe the interrelationship between repetitions and intensity in weight training is repetition maximum (RM). If you perform an exercise such as a bench press and lift 150 pounds once, but you cannot do a second repetition, you have done one repetition maximum, or 1RM. Individual workouts are generally based on a percentage of the RM, such as 80 percent of 1RM. For example, if your 1RM for the bench press is 150 pounds, 80 percent would be 120 pounds (0.8 × 150). If you bench press 120 pounds for five repetitions but cannot do a sixth, you have done five repetition maximum, or 5RM. A set is any particular number of repetitions, such as five or ten. The total volume of work you do in a single workout is the product of sets, repetitions, and resistance. For example, if you bench press three sets of five repetitions with a resistance of 100 pounds, your total volume of work is 1,500 pounds (3 × 5 × 100). The recovery period may represent the rest intervals between sets in a single workout or the rest interval between workouts during the week.

What are the primary purposes of resistance training? As is probably obvious to you, there is an inverse relationship between the amount of weight you can lift and the number of repetitions you can do. If your 1RM in the bench press is 150 pounds, you can do more repetitions with 100 pounds than you can with 140. The strengthendurance continuum is a training concept that focuses upon the interrelationship between resistance and repetitions. As depicted in figure 12.3, to train for muscular strength you must combine high resistance with a low number of repetitions. Conversely, to train for muscular endurance, you must combine a low resistance with a high number of repetitions. Resistance training programs may be designed to train all three of the human energy systems. The ATP-PCr energy system predominates in strength and power activities, the lactic acid energy system is primarily involved in anaerobic endurance, and the oxygen system is involved in aerobic endurance activities. Thus, resistancetraining programs may be developed for various purposes. The American College of Sports Medicine (ACSM) and the American Heart Association (AHA), both separately and collectively, have provided recommendations for participation in resistance training programs. Most of these recommendations focus on resistance training as a component of an overall exercise program to improve muscular strength and endurance in healthy young and older adults. The ACSM also developed a set of recommendations dealing with progression, or the gradual increase in overload www.mhhe.com/williams9

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Strength Power

Endurance

High

Resistance

Low

Low

Repetitions

High

10 P

ds

Poun 50

ounds

F I G U R E 1 2 . 3 The strength-endurance continuum.To gain strength, you need to train on the strength end of the continuum; to gain endurance, you need to train on the endurance end of the continuum.

placed on the body during training, and is more appropriate for the individual training to maximize muscular size and strength for bodybuilding or sport competition. The interested reader is referred to the ACSM and AHA recommendations authored by the American College of Sports Medicine, Haskell, Nelson, and Williams and their colleagues. These recommendations highlight the following purposes of resistance training, along with the recommended type of program. Training for Muscular Hypertrophy Higher volume, multipleset programs are recommended for maximizing muscle hypertrophy. Emphasize a range of 6–12 RM per set. Training for Strength and Power Multiple sets with fewer repetitions are recommended to maximize strength and power. Emphasize a range of 4–6 RM per set. Also, incorporate multiple sets of light loads (30–60 percent of 1 RM) at a fast contraction velocity. Training for Local Muscular Endurance Multiple sets with more repetitions and light to moderate loads, such as 15 or more repetitions at 40–60 percent of 1 RM, are recommended. Use a short recovery period between sets. Training for Health-Related Benefits Single sets are sufficient, approximating 8–12 RM. Include a variety of exercises that stress the major muscle groups of the body. 506

What are the basic principles of resistance training? Given the different purposes for which individuals may do resistance training, the design of the individual training program will vary accordingly. Athletes training to maximize muscle mass, strength, and power for their sport will engage in a more rigorous training program compared to someone doing resistance training for health benefits. Although the design of the resistance-training program may vary, the underlying principles are the same. The following discussion will highlight recommendations to gain muscle mass. As noted in chapter 1, the following principles are not restricted to resistance training but apply to all forms of exercise training. For example, intensity of exercise is simply another way of phrasing the overload principle. Overload The principle of overload is the most important principle in all resistance-training programs. The use of weights places a greater than normal stress on the muscle cell. This overload stress stimulates the muscle to grow—to become stronger—in effect to overcome the increased resistance imposed by the weights (see figure 12.4). To overload the muscle you must increase the volume of work it must do. There are basically two ways to do this. One is to increase the amount of resistance or weight that you use; the other way is to increase the number of repetitions and sets you do. For beginners, a single set of 8 to 10 exercises will help increase muscle mass and strength gains. Wolfe and others conducted a metaanalysis of available studies, and reported that single-set programs for an initial short training period in untrained individuals result in similar strength gains as multiple-set programs. If you know your 1 RM, you should be able to do 8 to 12 RM if you use 60 to 80 percent of your 1 RM value. For example, if your bench press 1 RM is 150 pounds, you should be able to do at least 8 RM with 70 percent of that value, or 105 pounds (0.70 × 150). Progression As the muscle continues to get stronger during your training program, you must increase the amount of resistance, the overload, to continue to get the proper stimulus for sustained muscle growth. This is known as the principle of progressive resistance exercise (PRE), another basic principle of resistance training. In their meta-analysis, Wolfe and others noted that as progression occurs and higher gains are desired, multiple-set programs are more effective. Following a learning period, a recommended program for beginners is three to five sets using loads corresponding to 8–12 RM. The first step is to determine the maximum amount of weight that you can lift for eight repetitions. If you can do more than eight repetitions, the weight is too light and you need to add more poundage. As you get stronger during the succeeding weeks, you will be able to lift the original weight more easily. When you can perform twelve repetitions, add more weight to force you back down to eight repetitions; this is the progressive resistance principle. Over several months’ time, the weight will probably need to be increased several times as you continue to get stronger. Such a transition is illustrated in figure 12.5. The ACSM recommends that as you become an intermediate or advanced lifter, you should emphasize loads of 1–6 RM and progress when you can do about 1–2 more

C H A P T E R 1 2 Weight Gaining through Proper Nutrition and Exercise

Week:

1

4

7

10

13

16

50

50

60

60

70

70

Repetitions:

5

10

5

10

5

10

Sets:

4

4

4

4

4

4

Weight:

F I G U R E 1 2 . 5 The principle of progressive resistance exercise (PRE) states that as you get stronger, you need to progressively increase the resistance in order to continue to gain strength and muscle. In this example, the individual increases the resistance when she can complete ten repetitions with a given weight, but then doing only five repetitions with the increased weight. F I G U R E 1 2 . 4 Lifting heavy weights illustrates the principle of overload in action with weight training. If improvement in strength is to continue, weights must be increased.

repetitions than the upper limit of the range. For example, if you are using the 6 RM protocol, you might add resistance when you can do 8 repetitions. Specificity The principle of specificity is a broad training principle with many implications for resistance training, including specificity for various sports movements, strength gains, endurance gains, and body-weight gains. For example, a swimmer who wants to gain strength and endurance for a stroke should attempt to find a resistance-weight training program that exercises the specific muscles in a way as close as possible to the form used in that stroke. If you want to gain muscle mass in a certain part of the body, those muscles must be exercised. Strength coaches can help athletes develop resistance-training programs for specific sports. Exercise Sequence Your exercise routine should be based upon the principle of exercise sequence. This means that if you have ten exercises in your routine, they should be arranged in logical order so that fatigue does not limit your lifting ability. For

example, the first exercise in a sequence of ten might stress the biceps muscle, the second the abdominals, the third the quadriceps, and so forth. After you perform one full set of each of the ten exercises, you then do a complete second set, followed by the third set. This approach may be best for beginners and is the sequence for the eight exercises presented in this chapter. Another popular option is to do three sets of the same exercise with a rest between sets; then do three sets of the second exercise, and so on. This approach may be a little more fatiguing because you are using the same muscle group in three successive sets, but it appears to be very effective. The time spent in recovery will also lengthen the total time for the workout. The ACSM also provides some guidelines on exercise sequence, recommending the following: • Do multiple joint exercises before single joint exercises. • Do large muscle group exercises before small muscle group exercises. • Do higher intensity before lower intensity exercises. Recuperation Resistance training, if done properly to achieve the greatest gains, imposes a rather severe stress on the muscles, requiring a period of recovery both during the workout and between workouts. Research has shown that high-intensity www.mhhe.com/williams9

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resistance exercise can lead to rapid depletion of ATP and PCr, the high energy phosphates stored in the muscles; however, most of these high energy compounds may be restored in about 2 to 3 minutes of recovery. This is the principle of recuperation. Thus, several minutes should intervene between sets if you are using the same exercise. Taking adequate rest between sets may help maintain the quality of the workout. Ratamess and others studied the effect of varying rest intervals between five sets of the bench press. A rest interval of only 30–60 seconds resulted in a significant decrease in lifting volume in each subsequent set, whereas resting for 5 minutes impaired lifting capacity only in the fifth set. Resting for 2–3 minutes helped maintain lifting volume during the first 2–3 sets, but not in the latter sets. Additionally, for beginners, resistance training should generally be done about 3 days per week, with a rest or recuperation day in between. This day of rest allows sufficient time for your muscle to repair itself and to synthesize new protein as it continues to grow, for research has shown that muscle protein synthesis occurs for up to 24 hours after a single bout of heavy resistance exercise. The ACSM indicates that advanced lifters could train 4–5 days per week. For health benefits, the ACSM and AHA recommended resistance exercise at least twice a week on nonconsecutive days. Periodization Periodization is a technique applied to resistance training, as well as other forms of exercise training, that modifies the amount of exercise stress placed on the individual over the course of time. Periodization of training is primarily applicable to athletes. In general, periodization is based on Hans Selye’s theory on adaptation to stress. The body will adapt to exercise stress in ways beneficial to performance enhancement, but as noted in chapter 3, excessive exercise may predispose athletes to overreaching and overtraining, which may contribute to impaired performance. Periodization establishes the amount and intensity of training in various time cycles. A microcycle is about a week whereas a macrocycle may be a year or more. A mesocycle is any intermediate time frame, and may involve phases in preparation for competition and peaking for championship-type events. A detailed discussion of periodization is beyond the scope of this book. An excellent summarization has been provided by Kraemer and Ratamess. Periodization programs are available in most resistance-training texts and are the major focus in the text Periodization Training for Sports by Bompa and Carrera. With the exception of periodization, these general principles should serve as guidelines during the beginning phase of your resistance-training program and should be used to guide your progress during the first 3 months of the basic resistance-training program described next. If you become serious about resistance training, additional reading is advised. Personal trainers may also be helpful.

What is an example of a resistance-training program that may help me to gain body weight as lean muscle mass? If your goal is to gain significant amounts of muscle mass, you may wish to exercise on the strength end of the strength-endurance continuum, using six to ten different exercises that stress the major 508

muscle groups of the body. About three to five sets of each exercise are done. For those with limited time, one set may also provide significant increases in strength and muscle mass, as recently documented by Starkey and others. You should work up to 10–12 repetitions. You may modify this range, either using 6–10 or 8–12 as the repetition base. We will use the 8–12 model below and in the illustrations. The PRE concept is used, starting with resistance you can handle for eight repetitions and progressively increasing the repetitions to twelve. After you reach twelve repetitions, increase the resistance until you must come back to eight repetitions. Numerous resistance-training exercises are available to stress the major muscle groups in the body. The following exercises provide a sound basic resistance-training program for the adolescent and adult beginner. 1. Learn the proper technique for each exercise with a light weight, possibly only the bar itself, for 2 weeks. Do eight to twelve repetitions of each exercise to develop form. Do not strain during this initial learning phase. Concentrate on lowering the weight slowly. 2. For each exercise, determine the maximum weight that you can lift for eight repetitions after the 2-week learning phase. 3. A weekly record form, similar to the one presented in table 12.3, should be used to keep track of your progress. 4. Do one set of the eight exercises shown in figures 12.6 to 12.13. The sequence of exercises should be a. Bench press: chest muscles b. Lat machine pulldown or bent-arm pullover: back muscles c. Half squat: thigh muscles d. Standing lateral raise: shoulder muscles e. Heel raise: calf muscles f. Standing curl: front upper arm muscles g. Seated overhead press: back upper arm muscles h. Curl-up: abdominal muscles 5. Because the exercise sequence is designed to stress different muscle groups in order, not much recuperation is necessary between exercises—possibly only 30 seconds or so. 6. Do three to five complete sets. You may wish to rest 2 to 3 minutes between sets. 7. Exercise 3 days per week; in each succeeding day try to do as many repetitions as possible for each exercise in each set. When you can do twelve repetitions each after a month or so, add more weight so you can do only eight repetitions. 8. Repeat step 7 as you progressively increase your strength. Because barbells and dumbbells appear to be the most common means of doing resistance training, this is the method utilized. However, other apparatus such as the Nautilus, Hammer, and others can also be used effectively to gain weight and strength. Most of the exercises described here using barbells or dumbbells have similar counterparts on other apparatus. Note that muscles seldom operate alone, and that most resistance-training exercises stress more than one muscle group. Thus, keep in mind that although an exercise may be listed specifically for the chest muscles, it may also stress the arm and shoulder muscles. The exercises described in this section generally stress more than one body area, although their main effect is on the area noted.

C H A P T E R 1 2 Weight Gaining through Proper Nutrition and Exercise

TABLE 12.3

Weekly resistance-training record, basic eight exercises

Chest

Back

Thigh

Shoulder

Calf

Front arm

Back arm

Abdominal area

(Bench Press)

(Lat Pulldown)

(Half Squat)

(Lateral Raise)

(Heel Raise)

(Curls)

(Seated Press)

(Curl-ups)

Wt

Wt Reps

Wt Reps

Wt Reps

Wt Reps

Wt Reps

Wt Reps

Wt Reps

Reps

Date _________ Set 1 Set 2 Set 3 Set 4 Set 5 Date _________ Set 1 Set 2 Set 3 Set 4 Set 5 Date _________ Set 1 Set 2 Set 3 Set 4 Set 5 Date _________ Set 1 Set 2 Set 3 Set 4 Set 5

It is important to note that your muscle contracts during both the up and down phase of weight lifting. As noted later, some training methods are based on this concept. When you lower a weight, your active muscle is actually contracting to help decrease the force of gravity. Lowering a weight slowly increases the time

your muscle must contract. Raising the weight takes more force as you are working against the force of gravity. These eight exercises stress most of the major muscle groups in the body and thus provide an adequate stimulus for gaining body weight and strength through an increase in muscle mass. Literally www.mhhe.com/williams9

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Pectoralis major

(a) Starting position

(b) Ending position

Chest Exercise

Bench press

Chest muscles

Pectoralis major

Other muscles

Deltoid, triceps

Sets

3–5

Repetitions

8–12, PRE concept

Safety

Have spotter stand behind bar to assist as fatigue sets in.

Equipment

Bench with support for weight, or two spotters to hand weight to you.

Description

Lie supine on bench. Use wide grip for chest development. Secure bar and lower slowly to chest. Press bar straight up to full extension. Do not arch back.

F I G U R E 1 2 . 6 The bench press. The bench press primarily develops the pectoralis major muscle group in the chest; it also develops the deltoids in the shoulder and the triceps at the back of the arm. Note: For safety reasons, a spotter shoulpd be present to assist in case of difficulty. The spotter is not depicted for purposes of illustration clarity.

hundreds of different resistance-training exercises and techniques to train are available; if you become interested in diversifying your program, consult a book specific to resistance training. Several may be found in the reference list at the end of this chapter. For example, nearly thirty different types of programs are presented in the classic text by Steven Fleck and William Kraemer, Designing Resistance Training Programs. Some professional organizations, such as the National Strength and Conditioning Association, also provide excellent resistance training exercises. www.nsca-lift.org For detailed illustrations of a wide variety of resistance-training exercises, either in video or slide format, click on For the Public and then Free Training Videos. The muscles involved in each exercise and safety tips are also provided.

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Are there any safety concerns associated with resistance training? As noted later, there are several health problems that may contradict participation in a strenuous resistance training program. However, resistance training is generally regarded as a relatively safe sport, particularly if appropriate safety precautions are taken. The following guidelines should be incorporated into all resistancetraining programs. 1. Learn to breathe properly. During the most strenuous part of the exercise you are likely to hold your breath. This is a natural response; it helps to stabilize your chest cavity to provide a more stable base for your muscles to function. Usually the breath hold is short and no problems occur. However, if

C H A P T E R 1 2 Weight Gaining through Proper Nutrition and Exercise

Latissimus dorsi

(a) Starting position Latissimus dorsi

(a) Starting position

(b) Ending position

Back (b) Ending position

Exercise

Lat machine pulldown

Back muscles

Latissimus dorsi

Back

Other muscles

Biceps, pectoralis major

Alternate exercise

Bent-arm pullover

Sets

3–5

Back muscles

Latissimus dorsi

Repetitions

8–12, PRE concept

Other muscles

Pectoralis major

Safety

A very safe exercise

Sets

3–5

Equipment

Lat machine

Repetitions

8–12, PRE concept

Description

From seated or kneeling position, take a wide grip at arm’s length on the bar overhead. Pull bar down until it reaches your chest. Return slowly to starting position.

Safety

Do not arch back. Start with light weights when learning the technique.

Equipment

Bench

Description

Lie supine on bench, entire back in contact with the bench, feet on the bench, knees bent. Hold weight on chest with elbows bent. Swing weight over head, just brushing hair, and lower as far as possible without taking back off the bench. Keeping elbows in, return the weight to the chest.

Note: If a lat machine is not available, the bent-arm pullover may be substituted.

F I G U R E 1 2 . 7 A The lat machine pulldown. The lat machine pulldown trains the latissimus dorsi in the back and side of the upper body, and it also develops the biceps on the front of the upper arm and the pectoralis major in the chest.

F I G U R E 1 2 . 7 B The bent-arm pullover. The bent-arm pullover trains the latissimus dorsi and develops the pectoralis major. Note: For safety reasons, a spotter should be present to assist in case of difficulty. The spotter is not depicted for purposes of illustration clarity.

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Quadriceps

Hamstrings

(a) Starting position

(b) Ending position

Thigh Exercise

Half-squat or parallel squat

Thigh muscles

Quadriceps (front), hamstrings (back)

Other muscles

Gluteus maximus

Sets

3–5

Repetitions

8–12, PRE concept

Safety

Have two spotters to assist if using free weights. Keep back straight. Drop weight behind you if you lose balance. Do not squat more than halfway down.

Equipment

Squat rack if available. Pad the bar with towels if necessary.

Description

In standing position, take bar from squat rack or spotters and rest on the shoulders behind the head. Squat until thighs are parallel to ground or until buttocks touch a chair at this parallel position. Do not squat beyond halfway. Keep back as straight as possible. Return to standing position, but do not lock your knees. This will maximize stress on your thighs.

F I G U R E 1 2 . 8 The half-squat or parallel squat. The half-squat develops the quadriceps muscle group on the front of the thigh and the hamstrings on the back of the thigh. Note: For safety reasons, spotters should be present to assist in case of difficulty. The spotters are not depicted for purposes of illustration clarity.

prolonged, it may increase the chances of suffering some of the problems noted previously, such as a hernia. Also associated with prolonged breath holding is a response known as the Valsalva phenomenon (Valsalva maneuver), which may lead to a possible blackout. Here is what happens. As you reach a sticking point in your lift and strain to overcome it, you normally hold your breath; this causes your glottis to close over your windpipe and the pressure in your chest and abdominal area to rise rapidly. The 512

pressure creates resistance to blood flow, reducing the return of blood to the heart, and eventually leading to decreased blood flow to the brain and a possible blackout. Additionally, the Valsalva maneuver exaggerates the increase in blood pressure during resistance exercises, and although a brief Valsalva maneuver is unavoidable when doing near maximal exercises, its effect may be minimized by proper breathing. A recommended breathing pattern that will help minimize these adverse effects is to breathe out while lifting the weight

C H A P T E R 1 2 Weight Gaining through Proper Nutrition and Exercise

Deltoid muscles

(a) Starting position

(b) Ending position

Shoulders Exercise

Standing lateral raise

Shoulder muscles

Deltoid

Other muscles

Trapezius

Sets

3–5

Repetitions

8–12, PRE concept

Safety

Do not arch back.

Equipment

Dumbbells

Description

Stand with dumbbells in hands at sides. With palms down, raise straight arms sideways to shoulder level. Bend elbows slightly. Return slowly to starting position.

F I G U R E 1 2 . 9 Standing lateral raise. The standing lateral raise primarily develops the deltoid muscles in the shoulder; the trapezius in the upper back and neck area is also trained.

and breathe in while lowering it. You should breathe through both your mouth and nose while exercising. Practice proper breathing when you learn new resistance-training exercises. 2. Use spotters. When using free weights, use spotters when doing exercises that may be potentially dangerous, such as the bench press. If you are doing a bench press alone and reach a sticking point in your lift, the Valsalva phenomenon may lead to serious consequences if you lose control of the weight directly above your head. The use of machines such as Nautilus helps eliminate the need for spotters. 3. Use safety equipment. If using free weights, place lock collars on the bar ends so the plates do not fall off and cause injury to the feet. Again, the use of machines eliminates this safety haz-

ard. However, do not attempt to change weight plates on machines while they are being used. Your fingers may get caught between the weights. 4. Warm up. Warm up with proper stretching exercises. Gently stretch the muscles to be used during exercise. Slow, static methods are recommended for cold muscles. Incidentally, Kokkonen and others found that if, for some reason, you are unable to participate in traditional resistance training, you may be able to increase strength by stretching. They found that 10 weeks of static stretching, 40 minutes for 3 days per week, of all the major muscle groups in the lower extremity improved knee flexion and extension strength, and may facilitate the transition back to regular training. www.mhhe.com/williams9

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Biceps

Gastrocnemius and soleus

(a) Starting position (a) Starting position

(b) Ending position

(b) Ending position

Front of arm Calf

Exercise

Standing curl

Exercise

Heel raise

Arm muscle

Biceps

Calf muscles

Gastrocnemius, soleus

Other muscles

Several elbow flexors

Other muscles

Deep calf muscles

Sets

3–5

Sets

3–5

Repetitions

8–12, PRE concept

Repetitions

8–12, PRE concept

Safety

Safety

Have two spotters if you use free weights.

Do not arch back. Place back against wall to control arching motion.

Equipment

Squat rack if available. Pad the bar with a towel if necessary.

Equipment

Curl bar if available

Description

Stand with weight held in front of body, palms forward. Place back against wall. Bend the elbows and bring the weight to the chest. Lower it slowly.

Description

Place bar on back of shoulders as in squat exercise. Raise up on your toes as high as possible and then return to standing position. Place the toes on a board so heels can drop down lower than normal. Point toes in, out, and straight ahead during different sets to work the muscles from different angles.

F I G U R E 1 2 . 1 0 Heel raise. The heel raise develops the two major calf muscles—the gastrocnemius and the soleus. Note: For safety reasons spotters should be present to assist in case of difficulty. The spotters are not depicted for purposes of illustration clarity.

5. Use proper technique. Use light weights to learn the proper technique of a given exercise so that you do not strain yourself if you do the exercise incorrectly. Learn to lift smoothly. Do not use jerking motions. When the proper technique is mastered, the weights may be increased. Using proper technique ensures that the desired muscle group is being exercised. 514

F I G U R E 1 2 . 1 1 The standing curl. The standing curl strengthens the biceps muscle in the front of the upper arm as well as several other muscles in the region that bend the elbow.

6. Protect your lower back. Avoid exercises that may cause or aggravate low back problems. Try to prevent an excessive forward motion or stress in the lower back region. Figure 12.14 illustrates some positions that should be avoided. 7. Lower weights slowly. If you lower them rapidly, your muscles have to contract rapidly to slow the weights down as you reach the starting position. This necessitates the development of a large amount of force that may tear some connective tissue and cause muscle soreness.

C H A P T E R 1 2 Weight Gaining through Proper Nutrition and Exercise

Rectus abdominis

Triceps (a) Starting position

(a) Starting position

(b) Ending position (b) Ending position

Back of arm Exercise

Seated overhead press (triceps extension)

Abdominal area

Arm muscle

Triceps

Exercise

Curl-up

Other muscles

Trapezius, deltoids

Abdominal muscles

Rectus abdominis

Sets

3–5

Other muscles

Oblique abdominis muscles

Repetitions

8–12, PRE concept

Sets

3–5

Safety

Do not arch back excessively. Have spotter available as fatigue sets in.

Repetitions

8–12, PRE concept

Safety

Equipment

Bench or chair

Develop sufficient abdominal strength before using weights with this exercise. Do not arch back when exercising.

Description

Sit on bench with weight held behind the head near the neck. Hands should be close together, elbows bent. Keep elbows in. Straighten elbows and press weight over head to arm’s length. Lower weight slowly to starting position.

Equipment

Free-weight plates; incline sit-up bench if available.

Description

Lie on back, knees bent with heels close to buttocks. Hands should hold weights on chest. Curl up about a third to half way. Return to starting position slowly.

F I G U R E 1 2 . 1 2 The seated overhead press. The seated overhead press primarily develops the triceps muscle on the back of the upper arm; the exercise also trains the trapezius in the upper back and neck and the deltoids in the shoulder. Note: For safety reasons spotters should be present to assist in case of difficulty. The spotters are not depicted for purposes of illustration clarity.

How does the body gain weight with a resistance-training program? Muscle hypertrophy simply means increased muscle size. Figure 12.15 depicts the microstructure of muscle tissue. Resistancetraining exercises place a heavy overload on the muscle cell, in some

Note:This exercise may be done without weights but with an increased number of repetitions.

F I G U R E 1 2 . 1 3 The curl-up. The curl-up trains the rectus abdominis and the oblique abdominis muscles.

way stimulating the DNA within the multiple nuclei found in muscle cells. Carson indicated that the first stage of muscle hypertrophy, at the onset of overload, is associated with increased RNA activity and protein synthesis. Various hormones, such as testosterone and insulin, play important roles in stimulating muscle growth. www.mhhe.com/williams9

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(a)

(b)

(c)

F I G U R E 1 2 . 1 4 Avoid exercises or body positions that place excessive stress on the low-back region. Poor form in exercises like (a) the bench press and (b) the curl exaggerates the lumbar curve. Be sure to keep the lower back as flat as possible. Exercises similar to (c) the bentover row place tremendous forces on the lower back because the weight or resistance is so far in front of the body.

Over time the muscle cell tends to adapt to such stress by increasing its size. It may do so in several possible ways. First, the individual muscle cells and myofibrils may simply increase their size by incorporating more protein. Second, the myofibrils in each cell may multiply, which will increase the size of each muscle fiber. Third, the amount of connective tissue around each muscle fiber and around each bundle of muscle may increase and thicken, leading to an overall increase in the size of the total muscle. Fourth, the cell may increase its content of enzymes and energy storage, particularly ATP and glycogen. The increased muscle glycogen, along with increased muscle protein, binds additional water which contributes to an increased body weight. Finally, the muscle fibers themselves may increase in number (hyperplasia), but current evidence suggests this is much less likely to occur compared with the other four means to induce muscle hypertrophy. In their recent review, Folland and Williams noted that the primary factor contributing to increased overall muscle size is the increase in the size and number of the myofibrils. In addition to the effects on the muscle cell, although not all studies are in agreement, research data indicate that resistancetraining exercises may increase bone mineral content, possibly owing to increased muscle tension effects on the bone, which might provide a slight increase in total body weight. Resistance training may be an effective means to increase muscle size and mass. Such increases help improve muscular strength and endurance and may be important components in weight-control programs. Traditionally, in research studies females did not normally experience the same amount of hypertrophy that males did, although they did experience proportional

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gains in muscular strength and endurance. However, more recent research revealed a significant increase in muscle cell size when women engaged in an intense, concentrated resistancetraining program. Moreover, O’Hagan and others found that when exposed to the same short-term resistance-training program, muscle size increased similarly in women and men.

Is any one type of resistance-training program or equipment more effective than others for gaining body weight? There are a variety of methods for resistance training. Isometric methods involve a muscle contraction against an immovable object, such as trying to pull a telephone pole out of the ground. However, if you succeed in moving the object, then you are doing an isotonic exercise. Isotonic methods are of two types. The concentric method means the muscle is shortening, as the biceps does in the up phase of a pull-up. The eccentric method means the muscle is lengthening even though it is trying to shorten. In the down phase of the pull-up the biceps is now contracting eccentrically as it slows your rate of descent. Gravity is attempting to pull you down, but your biceps is resisting it. Finally, the isokinetic method uses machines or other devices to regulate the speed at which you can shorten your muscles. For example, you may try to move your arm as fast as possible, but you will be able to move only as fast as the setting on the isokinetic machine. Isokinetic exercise is also known as accommodating-resistance exercise because the resistance automatically adjusts to the force exerted, thus controlling the speed of movement.

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Bone

Tendon

(a) Skeletal muscle

Epimysium Perimysium

Connective tissue

Nucleus

(c) Skeletal muscle fiber (cell) Sarcolemma

Sarcomere

concluded that there is insufficient evidence for the superiority of any mode and/or type of muscle action over other modes and types of training. Moreover, in a recent study comparing the effects of concentric and eccentric muscle training in women, Nickols-Richardson and others reported no significant differences between the methods for improvements in muscular strength, fatfree body mass, or bone mineral content and density. All methods may be effective in increasing body weight provided the basic principles of resistance training, particularly the principle of overload, are followed. The ACSM recommends that your exercise program should include both concentric and eccentric exercise, which are incorporated in most machines and free weights. If you use machines, be sure to exercise all major muscle area. Free weights are relatively inexpensive and can be used for a wide variety of exercises. They also may be constructed at home, using pipe or solid broomstick handles for the bar and differentsized tin cans filled with cement for the weights. There may be some specific training programs that are better suited for specific purposes, such as specific sport performance enhancement or injury rehabilitation. These topics are beyond the scope of this text, so the interested reader is referred to more detailed resources, such as the texts by Fleck and Kraemer and Bompa and (e) Actin and myosin Carrera. (d) Myofibril myofilaments

If exercise burns Calories, won’t I lose weight on a resistance-training program?

Although exercise does cost Calories, the amount ex(b) Bundle pended during resistance (a group of training is relatively small muscle fibers) compared to more active aerFIGURE 12.15 Muscle structure. The whole muscle is composed of separate bundles of individual muscle obic exercise. Resistance fibers. Each fiber is composed of numerous myofibrils, each of which contains thin protein filaments arranged so training can be a high-intenthat they can slide by each other to cause muscle shortening or lengthening. Several layers of connective tissue sity exercise, but the time surround the muscle fibers, bundles, and whole muscles, which eventually band together to form the tendon. spent actually lifting during Several different resistance-training apparatuses are available, such a typical workout is usually short, therefore limiting the number as Atlantis, Nautilus, Hammer, Cybex, Hydra-Gym, Soloflex, and of Calories used. For example, in an hour workout, only about 15 minutes may be involved in actual exercise, the remaining other similar machines. Depending upon the model, they are designed to utilize one or more of the training methods cited previously. time being recovery between each exercise. Based upon metaA number of research studies have been conducted to deterbolic data collected in research studies, the average-sized male uses about 200 Calories in a typical workout, while the averagemine which of these methods or machines is best, particularly in relation to strength and power gains. Research suggests that at the sized female uses about 150 (see figure 12.16). Resistance training present time it is probably safe to say that the various training appears to have a small effect on post-exercise energy expenditure. In a recent study, Ormsbee and others reported that energy expendimethods are comparable in their ability to produce gains in muscle size and strength. For example, in a comprehensive review comture, mostly from fat, was increased following a 40–45 minute intense resistance training workout. The increased caloric expenparing the effects of dynamic exercise (including free weights and diture was only about 10 Calories over a 45–minute recovery weight machines), accommodating resistance (isokinetic and semiisokinetic devices), and isometric resistance, Wernbom and others period, not a very significant amount. However, Melanson and

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1 hour = 600–800 Calories

1 hour = 150–200 Calories

F I G U R E 1 2 . 1 6 All models of exercise increase caloric expenditure. However, an hour of regular weight training expends only about one-third to one-fourth as many Calories as vigorous aerobic activity. Combining aerobic exercises with weight training (circuit aerobics) helps burn more Calories than weight training alone; it also provides cardiovascular health benefits while increasing muscular strength and endurance.

others indicated that circuit resistance training, as discussed later, may lead to a total daily energy expenditure comparable to aerobic cycling exercise.

Are there any contraindications to resistance training? There are several health conditions that may be aggravated by resistance training, primarily by the increased pressures that occur within the body when you strain to lift heavy weights and hold your breath at the same time. Because the blood pressure can increase rapidly and excessively during weight lifting, to 300 mmHg or higher, individuals with resting blood pressures over 90 mmHg diastolic and 140 mmHg systolic should refrain from heavy lifting, for they may be exposed to an increased risk of blood vessel rupture and a possible stroke. Lifting with the arms and straining exercises also increase the stress on the heart and thus should be avoided by individuals who have heart problems, such as arrhythmias. Individuals with a hernia (a weakness in the musculature of the abdominal wall) also should refrain from strenuous weight lifting because the increased pressure may cause a rupture. Low back problems also may be aggravated by improper weight lifting techniques. Some individuals may suffer peripheral nerve injuries, such as carpal tunnel syndrome, involving weakness and numbness in the hand due to compressed nerves from improper lifting tech-

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niques. Individuals with these types of health problems should seek medical advice and be cleared by a physician before initiating or continuing with a resistance-training program. There has been some concern about the advisability of prepubescent youth lifting weights. However, in its recently updated policy statement on strength training by children and adolescents, the American Academy of Pediatrics endorsed the concept of resistance training for youngsters and indicated that appropriate strength-training programs have no apparent adverse effect on health, such as damage to growth plates in the bones. The Academy indicated that proper resistance techniques and safety precautions should be followed so that strength-training programs for preadolescents and adolescents are safe and effective. In this regard, Faigenbaum and others suggested that higher repetitions with moderate loads should be used in the adaptation period. In a meta-analysis of twenty-eight studies, Payne and others found that well-designed resistance-training programs appear to enhance muscular endurance and strength in children and youth, including prepubescent children, while Guy and Micheli concluded that young athletes participating in resistance training do not appear to be at any greater risk of injury than young athletes who have not undergone such training. However, the Academy noted that preadolescents and adolescents should avoid power lifting, bodybuilding, and maximal lifts until they reach physical and skeletal maturity. In his review, Faigenbaum indicated that resistance training may also confer some health benefits to youth, such as increased bone density, but Benson and others found that studies are too limited to determine whether youth derive other metabolic health benefits, such as improved serum lipid and glucose profiles. Moreover, the Academy suggested caution should be used with young athletes with preexisting hypertension or other cardiovascular problems as strength training may aggravate such conditions. Resistance training may be a very effective means of increasing strength in the elderly as well; research has shown that even those in their nineties may experience significant strength gains with appropriately designed resistance-training programs. Campbell also noted that resistance training helps older people retain or increase fat-free and muscle mass. However, although resistance training helps stimulate muscle hypertrophy and weight gain in the aged, the increase is less than that observed in younger individuals.

Are there any health benefits associated with resistance training? Although resistance training has been recommended mainly as a means of gaining muscle mass, body weight, and strength, in the past its use normally was not associated with any health benefits. However, increasing research efforts focusing on the health implications of resistance training have suggested several favorable effects. Some of the health benefits are associated with increases in lean body mass and strength, but Kraemer and others revealed that resistance training affects a number of systems in the body, not only the neuromuscular system, but also the connective tissue, cardiovascular, and endocrine systems. In this regard, Deschenes and Kraemer

C H A P T E R 1 2 Weight Gaining through Proper Nutrition and Exercise

indicated that resistance training may confer some additional physiological benefits conducive to good health to individuals of all ages. Recent reviews, including those by the ACSM and AHA, Schardt, Williams, and Yaspelkis, have reported multiple health benefits associated with resistance training, benefits which, along with those cited in other reports, include the following: 1. Increased lean body mass to help maintain resting energy expenditure and prevent obesity (The prevention of sarcopenia [loss of muscle mass] as one ages is a major health benefit.) 2. Increased strength to prevent falls and injury as one ages 3. Decreased pain in chronic low-back-pain patients to improve mobility 4. Increased bone mineral density to help prevent osteoporosis, particularly in females 5. Improved glucose metabolism and insulin sensitivity to help prevent diabetes or improve glucose control in diabetics 6. Improved serum lipid profiles, such as increased HDLcholesterol and decreased LDL-cholesterol, to help prevent atherosclerosis and coronary heart disease 7. Improved ability to complete activities of daily living and enhance the quality of life in older individuals 8. Improved mood, body image, self-concept, and psychological health in children, adolescents, and adults These findings are contrary to the belief that resistance training does not confer any health benefits comparable to aerobic exercise. It is also notable that many cardiac rehabilitation programs now incorporate resistance-training exercises. Indeed, the American Heart Association, the American College of Sports Medicine, and the Surgeon General’s report on physical activity and health all have recognized the importance of resistance training as an important component of health. Although 2–3 sets of resistance exercise may be recommended to optimize weight gain as muscle mass, Feigenbaum and Pollock indicated that health benefits may occur using a single set of 8–10 different exercises with 8–15 repetitions of each. Nevertheless, it still appears to be prudent health behavior to incorporate some aerobic exercise into your lifestyle, even when trying to gain body weight. Although the ACSM and AHA have incorporated resistance training in their recommended exercise program for healthy adults, it is designed to complement aerobic exercise, not to substitute for it. The American Academy of Pediatrics also noted that if long-term health benefits for children and adolescents are the goal, then strength training should be combined with an aerobic training program. Aerobic exercise programs do consume more Calories, so you would have to balance the expenditure with increased food intake if you want to gain weight. However, the energy expenditure does not need to be excessive to provide a beneficial training effect. For example, running 2 to 3 miles about 4 days per week would provide you with an adequate aerobic-exercise training effect for your heart, but it would cost you only about 200–300 Calories a day. This 200- to 300-Calorie expenditure could be replaced easily by consuming two glasses of orange juice or similar small amounts of food.

Can I combine aerobic and resistance-training exercises into one program? Although the principles underlying the development of an aerobic-training program and a resistance-training program are similar, the purposes of the two programs are rather different. An aerobic exercise program is designed to improve the efficiency of the cardiovascular system; the basic purpose of a resistance-training program is to increase muscle size, strength, and body weight. One form of resistance training that has been used to provide some moderate benefits to the cardiovascular system is circuit weight training, a method in which the individual moves rapidly from one exercise to the next. Generally, this type of program uses lighter weights with greater numbers of repetitions, thus increasing the aerobic component of training. Research reported energy expenditure of approximately 10 Calories per minute for males and 7 Calories per minute for females. Circuit weight training can improve strength, but Harber and others indicated strength gains are attributed more to neural adaptations because the relatively low resistance loads do not induce appreciable muscle hypertrophy. A newer version of this method is circuit aerobics. Circuit aerobics may be done in a variety of ways, but basically it involves an integration of aerobic and resistance-training exercises. It is actually a form of interval aerobic training, but instead of resting or doing a lower level of aerobic activity during the recovery interval, you do resistance-training exercises. Circuit aerobics may offer multiple health and performance benefits such as improved cardiovascular fitness, increased caloric expenditure for loss of body fat, improved muscular strength and endurance, and increased muscle tone in body areas not normally stressed by aerobic exercise alone. Curves, the largest fitness franchise in the world, has developed a 30-minute exercise program specifically for women using this concept. However, if the main purpose of your resistance-training program is to gain body weight as muscle mass, then you need to train near the strength end of the strength-endurance continuum. For athletes who need to maximize gains in lean body mass, strength, and especially power, some sports scientists suggest that aerobic training should be markedly reduced if not eliminated. For example, Malisoux and others, reviewing studies involving single muscle fibers to help understand the effects of different forms of exercise training, reported that muscle fiber peak power is increased after resistance training, but over time is decreased with endurance-training. Elliott and others indicate that cardiovascular endurance training programs are detrimental for the performance of power athletes, suggesting contributing factors such as inappropriate neuromuscular adaptations, a catabolic hormonal profile, or ineffective motor learning environment. They note that there are unequivocal drawbacks to distance training in the power athlete. http://growingstronger.nutrition.tufts.edu This Tufts University Website presents an evidence-based exercise program designed to increase muscle strength, maintain bone health, and improve balance, coordination, and mobility.

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䉴 Resistance training is generally regarded as a safe form of exer-

cise, but it may be contraindicated in some individuals, for example, those with high blood pressure and hernias. 䉴 Although resistance-training programs may confer some significant health benefits, it is also highly recommended that one add an aerobic exercise program to help condition the cardiovascular system.

䉴 A basic principle underlying all resistance-training programs is



䉴 䉴 䉴

the overload principle, which simply means the muscle should be stressed beyond normal daily levels. Progressive resistance is also a basic principle of resistance training, for as you get stronger through the use of the overload principle, you must progressively increase the resistance. To increase muscle mass and body weight, you should exercise near the strength end of the strength-endurance continuum. Your resistance-training program should exercise all major muscles groups in the body. A variety of methods and apparatuses are available for resistance training, but research suggests that they are equally effective as a means of gaining strength and muscle mass if the basic principles of resistance training are followed.

Skinfold Measurements/ Body Composition Girth Measurements

If you have time and are interested, start a resistance-training program, using the principles in the text. Record your 1 RM for an exercise (such as the bench press) initially and every two weeks for several months. Use a tape measure to determine body girth changes in the upper arm, chest, waist, and upper thigh. If you have access to skinfold calipers or other measures of body composition, keep similar records. Use a model comparable to those presented, (adjusting the numbers in the vertical column to represent weight lifted for 1 RM, millimeters for skinfold measurement, and centimeters or inches for girth measurement), graph the results, and compare to the text discussion.

Do this after 2–3 weeks of resistance training. Using free weights or an appropriate weight-training machine, such as Nautilus, determine your one repetition maximum (1RM) for a given exercise, such as the bench press. Start out with a light weight that you know you can easily lift one time, and then gradually add on amounts until you reach your limit.You should need only 3–4 attempts. Record the weight of the last successful attempt.

E X E R C I S E Maximum Repetition (1 RM)

A P P L I C AT I O N

C h e c k f o r Yo u r s e l f

10 9 8 7 6 5 4 3 2 1 Initial Training

2 Weeks

4 Weeks

6 Weeks

8 Weeks

10 Weeks 12 Weeks

Initial Training

2 Weeks

4 Weeks

6 Weeks

8 Weeks

10 Weeks 12 Weeks

Initial Training

2 Weeks

4 Weeks

6 Weeks

8 Weeks

10 Weeks 12 Weeks

10 9 8 7 6 5 4 3 2 1

10 9 8 7 6 5 4 3 2 1 I Upper arm

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G Chest

C H A P T E R 1 2 Weight Gaining through Proper Nutrition and Exercise

L Waist

+ Upper thigh

Review Questions—Multiple Choice (b) Myofibrils in each cell may multiply. (c) Connective tissue in muscle may increase and thicken. (d) Muscle cells will increase water content by binding to increased glycogen. (e) Muscle fibers themselves increase rapidly in number. 6. For the purpose of gaining weight, which type of resistance-training equipment is best according to research findings, provided equal amounts of resistance work are done on each? (a) isokinetic concentric machines (b) isometric devices (c) isotonic eccentric free weights (d) isotonic concentric free weights (e) no equipment is better than any other 7. Which dietary supplement has the most research supporting its potential to help increase muscle mass and weight gain during a resistance-training program? (a) HMB (b) chromium (c) creatine (d) ginseng (e) carnitine 8. Research suggests that proper resistance training may confer some significant health benefits. Which of the following is least likely? (a) increased strength to prevent falls and injury as one ages (b) increased bone mineral density to help prevent osteoporosis (c) increased testosterone levels to help reduce serum HDL-cholesterol

(d) improved muscle mass and insulin sensitivity to help prevent type 2 diabetes (e) improved body image and psychological health 9. Which of the following would be the least likely dietary recommendation for someone trying to gain weight in lean mass? (a) Wait at least 4 hours after exercise before eating some protein and carbohydrate. (b) Increase the intake of high-Calorie, high nutrient foods. (c) Keep the intake of saturated fats to a minimum. (d) Eat three balanced meals a day supplemented with snacks. (e) Supplement the diet with high-Calorie, high nutrient liquids. 10. To gain one pound of muscle weight per week on a weight-training program, an individual might need an additional 14 grams of protein per day above the RDA, in addition to increased Calories. Which of the following would not supply that amount of protein daily? (a) 2 glasses of skim milk (b) 1 glass of orange juice and 2 eggs (c) 1 slice of toast, 1 egg, and 1 ounce of ham (d) 1 glass of orange juice, 2 slices of toast, and 1 banana (e) 2 ounces of cheese

Answers to multiple choice questions: 1. e; 2. d; 3. d; 4. a; 5. e; 6. e; 7. c; 8. c; 9. a; 10. d.

1. Which of the following would be least recommended for someone who wants to gain weight healthfully? (a) stop smoking (b) set a goal of about 0.5 pound per week (c) get enough rest and sleep (d) start a resistance training program (e) drink more caffeinated beverages 2. Which of the following is not one of the basic principles of resistance training? (a) overload (b) specificity (c) progressive resistance (d) aerobic (e) sequence 3. The bench press exercise is designed to have the greatest effect on which group of muscles? (a) calf (b) thigh (c) back (d) chest (e) abdominal 4. The standing lateral raise is designed to have the greatest effect on which group of muscles? (a) shoulder (b) thigh (c) calf (d) chest (e) abdominal 5. Resistance training will stimulate muscle hypertrophy by a variety of mechanisms. Which of the following is considered to be least likely according to your text discussion? (a) Individual muscle cells and myofibrils increase in size.

Review Questions—Essay 1. Explain the strength-endurance continuum as a training concept. 2. List the five basic principles of resistance training and provide an example of each.

3. Discuss the physiological means whereby resistance training leads to increases in muscle growth. 4. Describe at least five of the potential health benefits associated with resistance training.

5. Discuss the importance of protein in a weight-gaining diet and provide some recommendations for amounts of protein and types of protein-rich foods in the diet.

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References Books Bompa, T., and Carrera, M. 2005. Periodization Training for Sports. Champaign, IL: Human Kinetics. Fleck, S., and Kraemer, W. 2004. Designing Resistance Training Programs. Champaign, IL: Human Kinetics. Ivy, J., and Portman, R. 2004. Nutrient Timing: The Future of Sports Nutrition. North Bergen, NJ: Basic Health Publications. National Academy of Sciences. 2002. Dietary Reference Intakes for Energy, Carbohydrate, Fiber, Fat, Protein and Amino Acids. Washington, DC: National Academy Press. Pope, H., et al. 2000. The Adonis Complex. New York: Free Press. Reuben, D. 1996. Dr. David Reuben’s Quick WeightGain Program. New York: Crown Publishers. U.S. Department of Health and Human Services. 2000. Healthy People 2010. Washington, DC: U.S. Government Printing Office.

Reviews American Academy of Pediatrics Council on Sports Medicine and Fitness. 2008. Strength training by children and adolescents. Pediatrics 121:835–40. American College of Sports Medicine. 2002. Position stand: Progression models in resistance training for healthy adults. Medicine & Science in Sports & Exercise 34:364–80. American College of Sports Medicine. 2000. Position stand. Exercise and type 2 diabetes. Medicine & Science in Sports & Exercise 32:1345–60. Benson, A., et al. 2008. Effects of resistance training on metabolic fitness in children and adolescents: A systematic review. Obesity Reviews 9:43–66. Bloomer R.J. 2007. The role of nutritional supplements in the prevention and treatment of resistance exercise-induced skeletal muscle injury. Sports Medicine 37:519–32. Campbell, W. 2008. Synergistic use of higherprotein diets or nutritional supplements with resistance training to counter sarcopenia. Nutrition Reviews 65:416–22. Candow, D., and Chilibeck, P. 2007. Effect of creatine supplementation during resistance training on muscle accretion in the elderly. Journal of Nutrition, Health & Aging 11:185–88. Carson, J. 1997. The regulation of gene expression in hypertrophying skeletal muscle. Exercise and Sport Sciences Reviews 25:301–20. Clarkson, P. M., and Rawson, E. S. 1999. Nutritional supplements to increase muscle mass. Critical Reviews in Food Science and Nutrition 39:317–28. Coleman, E., et al. 2002. Herbal supplements and sport performance. Sports Science Exchange Roundtable 13 (4):1–4. Consumers Union. 2000. A 12-step program for safe exercise. Consumer Reports on Health 12 (4):8–9.

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Deschenes, M., and Kraemer, W. 2002. Performance and physiologic adaptations to resistance training. American Journal of Physical and Medical Rehabilitation 81:S3–S16. Elliott, M., et al. 2007. Power athletes and distance training: Physiological and biomechanical rationale for change. Sports Medicine 37:47–57. Faigenbaum, A. 2003. Youth resistance training. President’s Council on Physical Fitness and Sports Research Digest 4 (3):1–8. Folland, J., and Williams, A. 2007. The adaptations to strength training: Morphological and neurological contributions to increased strength. Sports Medicine 37:145–68. Foran, B. 1985. Advantages and disadvantages of isokinetics, variable resistance, and free weights. National Strength and Conditioning Association Journal 7:24–25. Forbes, G. 1999. Body composition: Influence of nutrition, disease, growth and aging. In Modern Nutrition in Health and Disease, eds. M. Shils et al. Baltimore: Williams & Wilkins. Gatorade Sports Science Institute. 1995. Methods of weight gain in athletes. Sports Science Exchange Roundtable 6 (3): 1–4. Grieve, F. 2007. A conceptual model of factors contributing to the development of muscle dysmorphia. Eating Disorders 15:63–80. Guy, J., and Micheli, L. 2001. Strength training for children and adolescents. Journal of the American Academy of Orthopedic Surgery 9:29–36. Haskell, W., et al. 2007. Physical activity and public health: Updated recommendation for adults from the American College of Sports Medicine and the American Heart Association. Medicine & Science in Sports & Exercise 39:1423–34. Houston, M. E. 1999. Gaining weight: The scientific basis of increasing skeletal muscle mass. Canadian Journal of Applied Physiology 24:305–16. Kraemer, W., et al. 2003. Strength training basics. Physician and Sportsmedicine 31 (8):39–45. Kraemer, W., et al. 1998. Resistance training and elite athletes: Adaptations and program considerations. Journal of Orthopaedic and Sports Physical Therapy 28:110–19. Kraemer, W., et al. 1996. Strength and power training: Physiological mechanisms of adaptation. Exercise and Sport Sciences Reviews 24:363–97. Kreider, R. B. 1999. Dietary supplements and the promotion of muscle growth with resistance exercise. Sports Medicine 27:97–110. Lambert, C., et al. 2004. Macronutrient considerations for the sport of bodybuilding. Sports Medicine 34:317–27. Lemon, P. 1996. Is increased dietary protein necessary or beneficial for individuals with a physically active lifestyle? Nutrition Reviews 54:S169–S175. Lodhia, K., et al. 2005. Peripheral nerve injuries in weight training. Physician and Sportsmedicine 33 (7):24–37.

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Malisoux, L., et al. 2007. What do single-fiber studies tell us about exercise training? Medicine & Science in Sports & Exercise 39:1051–60. National Strength and Conditioning Association. 1987. Breathing during weight training. National Strength and Conditioning Association Journal 9:17–24. Nelson, M., et al. 2007. Physical activity and public health in older adults: Recommendation from the American College of Sports Medicine and the American Heart Association. Medicine & Science in Sports & Exercise 39:1435–45. Payne, V., et al. 1997. Resistance training in children and youth: A meta-analysis. Research Quarterly for Exercise and Sport 68:80–88. Phillips, S. 2006. Dietary protein for athletes: From requirements to metabolic advantage. Applied Physiology, Nutrition and Metabolism 31:647–54. Phillips, S. 2004. Protein requirements and supplementation in strength sports. Nutrition 20:689–95. Rasmussen, B., and Phillips, S. 2003. Contractile and nutritional regulation of human muscle growth. Exercise and Sport Sciences Reviews 31:127–31. Schardt, D. 2007. Saving muscle: How to stay strong and healthy as you age. Nutrition Action Health Letter 34 (3):1, 3–8. Tipton, K., and Wolfe, R. 2001. Exercise, protein metabolism, and muscle growth. International Journal of Sport Nutrition and Exercise Metabolism 11:109–32. Tsika, R. 2006. The muscular system: The control of muscle mass. In ACSM’s Advanced Exercise Physiology, ed. C. M. Tipton. Philadelphia: Lippincott Williams & Wilkins. Volek, J. 2004. Strength nutrition. Current Sports Medicine Reports 2:189–93. Volek, J., et al. 2006. Nutritional aspects of women strength athletes. British Journal of Sports Medicine 40:742-48. Wernbom, M., et al. 2007. The influence of frequency, intensity, volume and mode of strength training on whole muscle cross-sectional area in humans. Sports Medicine 37:225–64. Williams, M. 1993. Nutritional supplements for strength trained athletes. Sports Science Exchange 6 (47): 1–6. Williams, M. A., et al. 2007. Resistance exercise in individuals with and without cardiovascular disease: 2007 update: A scientific statement from the American Heart Association Council on Clinical Cardiology and Council on Nutrition, Physical Activity, and Metabolism. Circulation 116:572–84. Wolfe, B., et al. 2004. Quantitative analysis of single- versus multiple-set programs in resistance training. Journal of Strength and Conditioning Research 18:35–47. Yaspelkis, B. 2006. Resistance training improves insulin signaling and action in skeletal muscle. Exercise and Sport Sciences Reviews 34:42–46.

Specific Studies Andersen, L., et al. 2005. The effect of resistance training combined with timed ingestion of protein on muscle fiber size and muscle strength. Metabolism 54:151–56. Bartels, R., et al. 1989. Effect of chronically increased consumption of energy and carbohydrate on anabolic adaptations to strenuous weight training. In Report of the Ross Symposium on the Theory and Practice of Athletic Nutrition: Bridging the Gap, eds. J. Storlie and A. Grandjean. Columbus, OH: Ross Laboratories. Bo/ rsheim, E., et al. 2004. Effect of an amino acid, protein, and carbohydrate mixture on net muscle protein balance after resistance exercise. International Journal of Sport Nutrition and Exercise Metabolism 14:255–71. Cribb, P., and Hayes, A. 2006. Effect of supplement timing and resistance training on skeletal muscle hypertrophy. Medicine & Science in Sports & Exercise 38:1918–25. Depcik, E., and Williams, L. 2004. Weight training and body satisfaction of body-image-disturbed women. Journal of Applied Sport Psychology 16:287–99. Faigenbaum, A. D., et al. 1999. The effects of different resistance training protocols on muscular strength and endurance development in children. Pediatrics 104:e5. Feigenbaum, M. S., and Pollock, M. L. 1999. Prescription of resistance exercise training for health and disease. Medicine & Science in Sports & Exercise 31:38–45. Galuska, D., et al. 2002. The epidemiology of U.S. adults who regularly engage in resistance training.

Research Quarterly for Exercise and Sport 73:330–34. Grunewald, K., and Bailey, R. 1993. Commercially marketed supplements for bodybuilding athletes. Sports Medicine 15:90–103. Harber, M., et al. 2004. Skeletal muscle and hormonal adaptations to circuit weight training in untrained men. Scandinavian Journal of Medicine and Science in Sports 14:176–85. Keith, R., et al. 1996. Nutritional status and lipid profiles of trained steroid-using bodybuilders. International Journal of Sport Nutrition 6:247–54. Kokkonen, J., et al. 2007. Chronic static stretching improves exercise performance. Medicine & Science in Sports & Exercise 39:1825–31. Kraemer, W., and Ratamess, N. 2005. Progression and resistance training. President’s Council on Physical Fitness and Sports Research Digest 6 (3):1–8. MacDougall, J., et al. 1992. Factors affecting blood pressure during heavy weight lifting and static contractions. Journal of Applied Physiology 73:1590–97. McLafferty, C., et al. 2004. Resistance training is associated with improved mood in healthy older adults. Perceptual and Motor Skills 98:947–57. Melanson, E., et al. 2002. Resistance and aerobic exercise have similar effects on 24-h nutrient oxidation. Medicine & Science in Sports & Exercise 34:1783–1800. Nickols-Richardson, S., et al. 2007. Concentric and eccentric isokinetic resistance training similarly increases muscular strength, fat-free soft tissue mass, and specific bone mineral measurements in young women. Osteoporosis International 18:789–96.

O’Hagan, F., et al. 1995. Response to resistance training in young women and men. International Journal of Sports Medicine 16:314–21. Ormsbee, M., et al. 2007. Fat metabolism and acute resistance exercise in trained men. Journal of Applied Physiology 102:1767–72. Pickett, T., et al. 2005. Men, muscles, and body image: Comparisons of competitive bodybuilders, weight trainers, and athletically active controls. British Journal of Sports Medicine 39:217–22. Pikosky, M., et al. 2008. Increased protein maintains nitrogen balance during exercise-induced energy deficit. Medicine & Science in Sports & Exercise 49:505–12. Ratamess, N., et al. 2007. The effect of rest interval length on metabolic responses to the bench press exercise. European Journal of Applied Physiology 100:1–17. Starkey, D., et al. 1996. Effect of resistance training volume on strength and muscle thickness. Medicine & Science in Sports & Exercise 28:1311–20. Staron, R., et al. 1989. Effects of heavy resistance weight training on muscle fiber size and composition in females. Medicine & Science in Sports & Exercise 21:S71. Whipple, T., et al. 2004. Acute effects of moderate intensity resistance exercise on bone cell activity. International Journal of Sports Medicine 25:496–501. Wilkinson, S., et al. 2007. Consumption of fluid skim milk promotes greater muscle protein accretion after resistance exercise than does consumption of an isonitrogenous and isoenergetic soy-protein beverage. American Journal of Clinical Nutrition 85:1031–40.

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T E R M S

alcoholism 532 anabolic/androgenic steroids (AAS) 548 androstenedione 551 blood alcohol concentration (BAC) 527 caffeine 533 cirrhosis 529 ciwujia 553 dehydroepiandrosterone (DHEA) 550 ephedra 542 ephedrine 542 ergolytic 528 ethanol 526 fetal alcohol effects (FAE) 531 fetal alcohol syndrome (FAS) 531

Food Drugs and Related Supplements

CHAPTER THIRTEEN ginseng 552 ma huang 542 proof 526 sodium bicarbonate 544

L E A R N I N G

O B J E C T I V E S

After studying this chapter, you should be able to: 1. Explain the metabolic, physiological, and psychological effects of alcohol in the body, and evaluate its efficacy as an ergogenic acid. 2. Explain the possible beneficial and detrimental effects of alcohol consumption on health. 3. List and explain the several theories whereby caffeine supplementation is proposed to be an effective ergogenic aid, and summarize its effect on exercise performance. 4. Explain the possible beneficial and detrimental health-related effects of caffeine in the body, and cite current recommendations for coffee consumption. 5. Understand the potential health problems associated with dietary supplements containing stimulants such as ephedra. 6. Describe the theory underlying the use of sodium bicarbonate as an ergogenic aid, and understand the current research findings regarding its efficacy to enhance exercise performance. 7. Identify drugs and related dietary supplements used by physically active individuals to stimulate muscle building and summarize the effects on exercise performance and potential health risks associated with their use. 8. Explain the theory as to how ginseng may enhance sport performance, and highlight the research findings regarding its ergogenic efficacy. 9. List those drugs or dietary supplements discussed in this chapter whose use is prohibited in sports. 10. Describe the four different recommendation levels for dietary supplements regarding their efficacy, safety, and permissibility as ergogenic aids for athletes, and cite examples of each.

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Introduction As noted in chapter 1, winning in sports is dependent not only on genetic endowment with physiological, psychological, and biomechanical attributes inherent to success in any given sport, but also on optimal training of those attributes. However, over the years athletes have attempted to go beyond training to gain a competitive edge on their opponents, and have used a wide variety of ergogenic aids in the process. The most historic and popular international sporting event is the Olympic Games. The first Olympics were held in Greece, starting in 776 BC and continuing for over 1,000 years, being cancelled in 393 AD because they were regarded as a pagan ritual. Similar to today, athletes who were successful in these ancient Olympics achieved fame and fortune. Most elite athletes had personal trainers, called paidotribes, to plan their exercise program and their diet to prepare them for competition. In a sense, paidotribes were the first sport scientists and sport nutritionists. Several famous Greek scientists, including Galen and Pythagoras, were paidotribes who advocated specific, but different, diets for their athletes; Galen promoted beans as a staple of the athlete’s diet, whereas Pythagoras prohibited them. During these early Olympic Games various plants served as sources of ergogenic drugs. For example, certain mushrooms contained hallucinogens while Strychnos nux vamica was the source of strychnine; in small doses both could serve as a stimulant. Athletes in the ancient Olympics were reported to consume such plants for their potential ergogenic effect. The modern Olympic Games were resurrected in 1896 and continue today with competition among thousands of athletes in dozens of sports. As in the

ancient Olympics, athletes in the modern Olympics have been reported to use drugs in attempts to obtain that competitive edge. As several of these drugs are found in some common foods or beverages that we may consume, they have been referred to as food drugs. Additionally, some plant extracts may be marketed as dietary supplements designed to imitate ergogenic drugs. Others, particularly herbals, may be used for their pharmaceutical effects by practitioners of alternative medicine. In this chapter, we will evaluate the effects of several food drugs and related dietary supplements on exercise performance and health. Two very common food drugs, alcohol and caffeine, have been studied for their ergogenic effects for over 100 years, and have been used by athletes as a means to enhance performance since the early 1900s. Each has also been studied extensively for possible health effects, both positive and negative. The dietary supplement ma huang contains ephedra, or ephedrine, a stimulant theorized to enhance exercise performance, particularly when combined with caffeine. Ephedrine has also been studied for its potential health effects. Sodium bicarbonate, or baking soda, is used in many food products, and has been studied for 80 years as a means to enhance performance; it also has been

marketed as part of a dietary supplement for athletes. Several anabolic hormones, and related steroid drugs, are used to increase muscle mass and have been popular with strength/power athletes for over 50 years. Because the use of such drugs has been controlled and illegal for sport competition for many years, companies have marketed prohormones, or precursors to these hormones, as dietary supplements to avoid drug regulations. However, these prohormones have also recently been classified as controlled drugs and their use is illegal in sports. Use of these anabolic agents may also pose serious health risks. Finally, several herbals, most notably ginseng, are used in alternative medicine for various purposes, one being enhancement of physical performance. Some of the dietary supplements discussed in this chapter have been banned by the World Anti-Doping Agency (WADA) for use in sports competition, while others are being monitored by WADA. Specific details will be provided where warranted. www.wada-ama.org The World AntiDoping Agency (WADA) provides the complete list of drugs and doping techniques whose use is prohibited or monitored in sports competition. Click on Prohibited List. The list is updated annually.

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Alcohol: Ergogenic Effects and Health Implications The alcohol produced for human consumption is ethyl alcohol, or ethanol. Ethanol may be classified as a psychoactive drug, a toxin, or a nutrient. The use of alcohol as a means to enhance exercise or sport performance has a long history. Ancient Greek athletes drank wine or brandy prior to competition, thinking that these alcoholic beverages enhanced performance. In more modern times, Olympic marathon runners in the Paris (1900) and London (1908) games drank brandy or cognac to enhance performance, while in the Paris Olympics in 1924 wine was served at fluid replacement stations in the marathon. In 1939, Boje noted that in cases of extreme athletic exertion or in events of brief maximal effort, alcohol has been given to athletes to serve as a stimulant by releasing inhibitions and lessening the sense of fatigue. Today, WADA prohibits use of alcohol in about a half-dozen sports. The use of alcohol as a social, psychoactive drug also has a long history, and its effects on human health have been studied extensively. In general, most research has focused on the numerous adverse health effects of excessive alcohol consumption. However, within the last quarter century some research has revealed some possible health benefits associated with light or moderate drinking. Nevertheless, abstinence may be the best strategy for some individuals.

What is the alcohol and nutrient content of typical alcoholic beverages? Alcohol is a transparent, colorless liquid derived from the fermentation of sugars in fruits, vegetables, and grains. Although classified legally as a drug, alcohol is a component of many common beverages served throughout the world. In the United States, alcohol is consumed mainly as a natural ingredient of beer, wine, and

liquors. Although the alcohol content may vary in different types, in general, beer is about 4–5 percent alcohol, wine is about 12–14 percent alcohol, and typical bar liquor (whiskey, rum, gin, vodka) is about 40–45 percent alcohol (figure 13.1). Other alcoholic beverages are also available, such as wine coolers and energy drinks, normally containing about 5–7 percent alcohol; some alcoholic malt energy drinks contain 10 percent alcohol, about twice the content of regular beer. The term proof is a measure of the alcohol content in a beverage and is double the percentage; an 86-proof bottle of whiskey is 43 percent alcohol, while a 150-proof bottle of Caribbean rum is 75 percent alcohol. One drink of alcohol is the equivalent of one-half ounce of pure ethyl alcohol or the equivalent of about 13–14 grams of alcohol. The following amounts of beer, wine, and liquor contain approximately equal amounts of alcohol and are classified as one drink: 12 ounces (one bottle) of beer 4 ounces (one wine glass) of wine 1.25 ounces (one jigger or shot glass) of liquor However, some beers may contain more than10 percent alcohol, some wines are fortified to 18–24 percent, and some liquors are 50–75 percent. Such beverages would provide significantly more alcohol per standard drink. Technically, alcohol may be classified as a nutrient because it provides energy, one of the major functions of food. Alcohol contains about 7 Calories per gram, almost twice the value of an equal amount of carbohydrate or protein. Beer and wine also contain some carbohydrate, a source of additional Calories. In general, a bottle of regular beer has about 150 Calories, while a 4-ounce glass of wine or a shot glass of liquor contains about 100 Calories. Table 13.1 provides an approximate analysis of the caloric content of common alcoholic beverages and nonalcoholic beer. In general, the alcohol Calories found in beer, wine, and liquor are empty Calories. Although wine and beer contain trace amounts of protein, vitamins, minerals, and phytochemicals, liquor is void of any nutrient value.

What is the metabolic fate of alcohol in the body?

1 glass of wine

1 can or bottle of beer

4 oz. of table wine

12 oz. of beer

12% alcohol by volume

4% alcohol by volume

4 ⋅ 0.12 = 0.48 oz. of ethyl alcohol per serving

12 ⋅ 0.04 = 0.48 oz. of ethyl alcohol per serving

FIGURE 13.1 526

1 shot glass with distilled spirits 1.25 oz. of whiskey or other hard liquor 40% alcohol by volume or 80 proof 1.25 ⋅ 0.40 = 0.50 oz. of ethyl alcohol per serving

Alcohol equivalencies in typical beverages.

C H A P T E R 1 3 Food Drugs and Related Supplements

About 20 percent of the alcohol ingested may be absorbed by the stomach; the remainder passes on to the intestine for absorption. The absorption is rapid, particularly if the digestive tract is empty. The alcohol enters the blood and is distributed to the various tissues, being diluted by the water content of the body. A small portion of the alcohol, about 3–10 percent, is excreted from the body through the breath, urine, or sweat, but the majority is metabolized by the liver, the organ that metabolizes other drugs. As the blood circulates, the liver of an average adult male will metabolize about one-third ounce (8–10 grams) of alcohol per hour, or somewhat less than the amount of alcohol in one drink. Although alcohol is derived from the fermentation of carbohydrates, it is metabolized in the body like fat. The liver helps convert the metabolic by-products

TABLE 13.1

Caloric content of typical alcoholic beverages Carbohydrate

Beverage

Amount

Alcohol

Total

Grams

Calories

Grams

Calories

Calories

Beer, regular

12 ounces

13

52

13

91

150

Beer, light

12 ounces

7

28

11

77

109

Beer, nonalcoholic

12 ounces

12

48

1

7

55

Beer, alcohol-free

12 ounces

12

48

0

0

48

Wine, table

4 ounces

4

16

12

84

100

Liquor, 80 proof

1.25 ounces

0

0

14

98

100

The small discrepancies in the calculation of total Calories for beer and liquor may be attributed to a small protein content in beer and trace amounts of carbohydrate in liquor.

Blood to liver

Ethanol

Alcohol dehydrogenase

Liver

H+

H+

Acetaldehyde

Fatty acids

Pyruvate

Acetate

Triglycerides

Lactate

Fatty liver

Blood from liver

F I G U R E 1 3 . 2 Simplified metabolic pathways of ethanol (alcohol) in the liver. Hydrogen ions are removed from ethanol as it is converted to acetaldehyde, which may be released into the blood for transport to other tissues.The excess hydrogen ions may combine with fatty acids to form triglycerides or with pyruvate to form lactate. Excessive accumulation of triglycerides may lead to the development of a fatty liver and eventually to cirrhosis.

of alcohol into fatty acids, which may be stored in the liver or transported into the blood. Several other compounds, such as lactate, acetate, and acetaldehyde, may also be released into the blood. These products may eventually be utilized for energy and converted into carbon dioxide and water. A schematic of alcohol metabolism is presented in figure 13.2. As noted, the liver of a 150-pound male can metabolize only about one-third ounce of alcohol, or less than one drink, per hour.

The rate is lower in smaller individuals and higher in larger individuals. Thus, consumption of alcohol at a rate greater than one drink per hour will result in an accumulation of alcohol in the blood; this is measured as the blood alcohol concentration (BAC) in grams per 100 milliliters of blood. The ingested alcohol is diluted throughout the total body water, both inside and outside body cells, including the blood. For the average male, one drink will result in a BAC of about 0.025, or 0.025 gram (25 milligrams) per 100 milliliters of blood; four drinks in an hour would lead to a BAC of a little less than 0.10 because a small amount will be metabolized by the liver. However, BAC concentrations resulting from the same amount of drinks may vary widely among individuals due to gender and differences in body weight and body fat. Moreover, the effects of a given BAC may vary widely among individuals due to differences in such factors as genetics and tolerance developed from chronic alcohol intake.

Is alcohol an effective ergogenic aid? For over a century, athletes have consumed alcohol just prior to or during competition in attempts to improve performance. Alcohol has been alleged to alter energy metabolism, improve physiological processes, or modify psychological factors so as to benefit the athlete. Let us look at the available research to evaluate the truth of these allegations. Use as an energy source Although alcohol contains a relatively large number of Calories and its metabolic pathways in the body are short, the available evidence suggests that it is not utilized to any significant extent during exercise. First, the major sources of energy for exercise are carbohydrates and fats, which are in ample supply in most individuals. Alcohol may help form fats, but there is no evidence that it can substitute for other fat sources in the body. Even if it could, this would be of no benefit because the body has more than enough fat to supply energy during prolonged exercise. Second, the by-products of alcohol metabolism that are released by the liver into the blood may enter the www.mhhe.com/williams9

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skeletal muscles but appear to be of little importance to exercising muscle. Third, even if the energy from alcohol could be used, it would represent an uneconomical source. The amount of oxygen needed to release the Calories from alcohol is greater than for an equivalent amount of carbohydrate and fat. And lastly, the rate at which the liver metabolizes alcohol limits its use as an energy source during exercise, particularly in an individual working at a high level of intensity. In summary, these four factors suggest alcohol is not a key energy source during exercise, and even if it were, it would not offer any advantages over natural supplies of carbohydrate and fat. Recent research with carbon labeling revealed alcohol did not significantly modify endogenous carbohydrate and fat utilization during exercise. Effect on exercise metabolism and performance Numerous studies have evaluated the potential ergogenic effect of alcohol intake, both in small and large amounts, just prior to various exercise protocols. In general, the resultant effects depend on the alcohol dose and the type of exercise performance. Research supports the finding that alcohol in small amounts (one to two drinks) neither improves nor deteriorates physiological processes associated with maximal aerobic exercise. For example, Coiro and others recently found that consuming small or moderate doses of alcohol before a 15-minute exercise test to exhaustion had no effect on heart rate, blood pressure, ventilation, oxygen consumption, or respiratory exchange ratio. Other studies indicate alcohol does not affect other indicators of maximal aerobic performance such as exercise tests to exhaustion. For example, one study reported an apparent trend toward a deterioration in performance with increased alcohol intake, but there was no adverse effect on 5-mile (8 km) treadmill run time. Moreover, tests of anaerobic performance, such as strength and local muscular endurance, also are not affected. However, a few studies have reported some potential adverse effects of consuming alcohol before or during submaximal exercise. Most of the studies alluded to above were conducted on males. A recent study reported some adverse acute effects of moderate alcohol consumption on cardiovascular and metabolic responses in females. In a submaximal cycling exercise task for 30 minutes, ingestion of alcohol increased the heart rate, oxygen consumption, blood pressure, and blood lactate, which the investigators indicated were negative effects. Earlier studies have also shown similar effects in males, including decreased pumping capacity of the heart with high BACs. Moreover, some recent research reported a significant decrease in aerobic endurance when alcohol was ingested before and during a treadmill run at about 80–85 percent VO2 max, which may have been associated with an impaired glucose metabolism. Impaired performance has also been reported in both an 800-meter and 1,500-meter run following alcohol consumption, and the detrimental effect was greater with increasing BACs from 0.01 to 0.10. Several metabolic effects of alcohol intake could impair endurance performance. In their recent review, El Sayed and others indicated studies suggest that alcohol consumption decreases the use of glucose and amino acids by skeletal muscles, adversely affects energy supply, and impairs the metabolic 528

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process during exercise. Alcohol reduces gluconeogenesis by the liver and glucose uptake by the legs during the latter stages of exercise. In prolonged exercise, such as marathons, these effects could lead to an earlier onset of hypoglycemia or muscle glycogen depletion and a subsequent decrease in performance. Alcohol intake during training could be counterproductive. Some studies have reported reduced absorption of vitamin B1 associated with moderate intakes of alcohol. Theoretically, this could impair physical performance of an endurance nature because vitamin B1 is involved in the aerobic metabolism of carbohydrate. In its recent position statement on fluid replacement, the ACSM indicated that alcohol consumption can increase urine output and delay full rehydration. Alcohol ingestion may also increase urine production by decreasing release of the anti-diuretic hormone. This effect could possibly impair temperature regulation during exercise under warm/hot environmental conditions. Starting a prolonged endurance event under warm/hot conditions in a dehydrated state could certainly impair performance. As a rehydration fluid after dehydration, drinks containing 4 percent alcohol or more, such as beer, tend to delay the recovery process as measured by restoration of blood and plasma volume. Additional research is merited to document any adverse effects of alcohol on cardiovascular or metabolic processes during exercise, but at this time it appears that alcohol intake before or during aerobic and anaerobic endurance exercise is not ergogenic and may be ergolytic, or impairing exercise performance. Effect on psychological processes Alcohol also has been used as an ergogenic aid primarily for its psychological effects. It is a narcotic, a depressant, that affects the brain. As a depressant of brain functions, alcohol would not be advocated as a means to improve sport performance. However, although classified as a depressant, some of alcohol’s effects are euphoric. Alcohol is thought to bind with receptors in the brain that may cause the release of dopamine, a neurotransmitter associated with the pleasure center of the brain. Normal inhibitory control centers in the brain may be suppressed. Some have contended that increased feelings of self-confidence, reduced anxiety levels, and a perceived decrease in sensitivity to pain may offset any depressant effects and possibly benefit performance. Moreover, alcohol in small doses may exert a paradoxical stimulation effect. Parts of the brain that normally inhibit behavior may be depressed by alcohol, leading to a transitory sensation of excitement. Although these effects may occur, research does not support the use of alcohol in sports involving psychological processes such as perceptual-motor abilities. Perceptual-motor activities involve the perception of a stimulus, integration of this stimulus by the brain, and an appropriate motor response (movement). The evidence overwhelmingly supports the conclusion that alcohol adversely affects psychomotor performance skills, such as reaction time, balance, hand/eye coordination, and visual perception. These are important in events with rapidly changing stimuli, such as tennis. Nevertheless, by reducing anxiety and related hand muscle tremor, alcohol could enhance performance in certain forms of

athletic competition, such as riflery, pistol shooting, dart throwing, and archery. Although research generally is not supportive of an improved performance, one study with archers revealed a tendency toward reduced tremor with low blood alcohol levels, resulting in a smoother release. However, no actual performance data were revealed. Throwing accuracy improved in darts at a BAC of 0.02, but was impaired at a BAC of 0.05. This area of study merits additional research. Social drinking and sports Only a limited number of studies have been conducted relative to the effect of social drinking upon physical performance, but there is rather general agreement that light social drinking will not impair performance on the following day. Tests of reaction time, strength, power, and cardiovascular performance were not adversely affected following the consumption of one drink the night before. On the other hand, heavy drinking may impair performance on the following day owing to hangover effects, involuntary eye movement, or dehydration. Permissibility The use of alcohol in competition by Olympic athletes had been banned previously by the IOC, but because wine and beer are commonly consumed as a part of many traditional European meals it was removed from the banned list prior to the 1972 Olympics. However, individual sports federations within the IOC still may consider alcohol use in competition as grounds for disqualification. At the present time, only several sports federations, such as archery and the pentathlon, which involve shooting competition, ban the use of alcohol. In his review, Williams noted that although alcohol consumption is not prohibited for use by athletes out of competition, there are no data supporting an ergogenic effect, and some data to suggest an ergolytic effect. This viewpoint was supported by Burke and Maughan in their review. Athletes who drink socially should do so in moderation, and possibly abstain 24 hours prior to a prolonged endurance contest.

What effect can drinking alcohol have upon my health? Consumption of alcoholic beverages is a popular pastime worldwide. People drink mainly for social reasons, but when and how much they drink may have a significant impact on their health and the health of others. As Klatsky noted, the basic disparity underlying all alcoholhealth relations is between the effects of lighter and heavier drinking. Although many of the effects of alcohol may negatively affect health status, some effects may be positive. Both the negative and the positive effects are detailed in the National Institute on Alcohol Abuse and Alcoholism (NIAAA) state-of-thescience report on the effects of moderate drinking. Although both men and women may incur health problems from drinking alcohol, Epstein and others recently noted that due to differences in metabolism of alcohol, women of all ages compared to men are at higher risk for negative physical, medical, and psychological consequences associated with at-risk and higher levels of alcohol consumption. For several reasons, women may

reach higher BAC levels than men for any given amount of alcohol intake. For one, women have lower levels of total body water, and thus the alcohol is less diluted. For another, some alcohol is metabolized in the stomach by one form of alcohol dehydrogenase, but the amount metabolized appears to be less in women than men. A higher BAC, either acutely or periodically over time, is associated with greater risk to health. Negative Effects Alcohol affects all cells in the body, and many of these effects may have significant health implications. Room and others noted that alcohol is causally related to more than 60 different medical conditions, and is a major challenge to public health. Alcohol and its metabolite, acetaldehyde, can have direct toxic effects on cells, possibly damaging DNA. Alcohol may adversely affect functions of major body organs, particularly the liver and brain, and other metabolic functions important to good health. Drinking alcoholic beverages, particularly in large amounts, is associated with over 75,000 deaths per year. Many of the adverse health effects of alcohol consumption are associated with heavy, or binge, drinking. Binge drinking in men is defined as consuming five or more drinks in one occasion, while the corresponding amount for women is four or more drinks. Liver disease The liver is the only organ in the body that metabolizes alcohol, and alcohol may affect liver function in several ways. It may interfere with the metabolism of other drugs, increasing the effect of some and lessening the effects of others. Even with a balanced diet high in protein, consuming six drinks a day for less than a month has been shown to cause significant accumulation of fat in the liver. If continued for five years or more, the liver cells degenerate. Eventually the damaged liver cells are replaced by non-functioning scar tissue, a condition known as cirrhosis. As liver function deteriorates, fat, carbohydrate, and protein metabolism are not regulated properly; this has possible pathological consequences for other body organs such as the kidney, pancreas, and heart. Nutrients, such as specific lipids from soybeans, are being studied as a means to help prevent this liver degeneration. Klatsky and others reported that epidemiological research suggests that drinking coffee, up to four cups daily, decreased the risk of developing alcoholic cirrhosis, suggesting some protective ingredient in coffee. Some scientists theorize that wine, because it contains antioxidants, may help prevent oxidative stress and subsequent liver damage, and may thus be the alcoholic beverage with less damaging effects. However, liver damage is one of the most consistent adverse effects of excess alcohol intake, and Reuben recently noted that safe and effective therapies for alcoholic cirrhosis have yet to be discovered. Psychological problems Many of the adverse health effects of alcohol consumption are associated with disturbed mental functions. Although alcohol is a depressant, as mentioned previously a small amount often provides pleasurable effects. For the most part, however, alcohol acts as a depressant, and its effects on the brain are dose-dependent. The effects occur in a hierarchical fashion related to the development of the brain. In general, alcohol first www.mhhe.com/williams9

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affects the higher brain centers. With increasing dosages, lower levels of brain function become depressed with subsequent disturbance of normal functions. This hierarchy of brain functions, from higher levels to lower levels, and some of the functions affected by alcohol may be generalized as follows: Thinking and reasoning—Judgment Perceptual-motor responses—Reaction time Fine motor coordination—Muscles of speech Gross motor coordination—Walking Visual processes—Double vision Alertness—Sleep, coma Respiratory control—Respiratory failure, death An overview of the effects of increasing BAC on mental and physical functions is presented in table 13.2. As noted in table 13.2, a BAC of 0.06–0.09 may impair judgment, fine motor ability, and coordination—three factors that are extremely important in the safe operation of an automobile and other modes of transportation. In the United States, a BAC of 0.08 is the level normally associated with driving under the influence TABLE 13.2 Typical effects of increasing

blood alcohol content Number of drinks* consumed in 2 hours

Blood** alcohol content

2–3

.02–.04

Reduced tension, relaxed feeling, relief from daily stress

4–5

.06–.09

Legally drunk (0.08) in most states, impaired judgment, a high feeling, impaired fine motor ability and coordination

6–8

.11–.16

Legally drunk in all states, slurred speech, impaired gross motor coordination, staggering gait

9–12

.18–.25

Loss of control of voluntary activity, erratic behavior, impaired vision

13–18

.27–.39

Stuporous, total loss of coordination

19 and above

>.40

Coma, depression of respiratory centers, death

Typical effects

*One drink = 12 ounces regular beer 4 ounces wine 1.25 ounces liquor **BAC based on body weight of 160 pounds (72.6 Kg).The BAC will increase proportionally for individuals weighing less (such as a 120-pound female) and will decrease proportionally for individuals weighing more (such as a 200-pound football player). For example, four to five drinks in 2 hours could lead to a BAC of 0.08–0.12 in a 120-pound individual.

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(DUI). At the least, being arrested for drunk driving may have serious social and personal consequences. At the worst, in the United States alone alcohol-related traffic crashes result in almost 18,000 deaths per year, about 40 percent of all fatal crashes. As the saying goes, “Don’t drink and drive!” In recent years alcoholic energy drinks have become increasingly popular among the young. Some believe that the caffeine and other possible stimulants in these drinks may counteract the depressant effects of alcohol. Cloud indicates research has shown that individuals who consume alcoholic energy drinks perceive their motor coordination to be better—but it is not. Alcohol usage also is correlated highly with aggressive tendencies. Laboratory studies have indicated aggressive behavior is directly related to the quantity of alcohol consumed. In a recent meta-analysis investigating the role of alcohol in fatal nontraffic injuries, Smith and others concluded that alcohol was an important factor in homicides and unintentional injury deaths. Alcohol abuse is also associated with sexual abuse. Alcohol usage may also lead to depression and suicide. Galaif and others recently noted that alcohol use remains extremely widespread among today's youth and is related to both depression and suicidality, the occurrence of suicidal thoughts or suicidal behaviors. They note that suicide is currently the third leading cause of death for teenagers and young adults between the ages of 15 and 24 years. Monti and others reported that heavy drinking during the teenage years may cause permanent brain damage, which may be a related factor. Most of these adverse psychological effects are associated with excessive alcohol intake, particularly as practiced in binge drinking. College students are known to engage in hazardous drinking, and not only in the United States and Canada. Karam and others recently noted that the prevalence of hazardous drinking among college students in Australia, Europe, and South America appears similar to that in North America. Recent surveys indicate that almost half of college students binge, and one of the most significant factors underlying alcohol-related behavior problems is the amount of alcohol consumed; the greater the amount of alcohol consumed, the more serious the problem. According to the NIAAA, nationally there are more than 1,400 alcohol-related deaths each year among college students, most due to automobile accidents, but several attributed to heavy binge drinking with resultant respiratory failure. Many physically active individuals, including competitive athletes, consume alcohol on a regular basis. In their periodic study of NCAA athletes, Green and others recently noted that alcohol was the most widely used drug, with over 80 percent of athletes using alcohol within the past year. In their review, El Sayed and others reported that alcohol continues to be the most frequently consumed drug among athletes and habitual exercisers and alcoholrelated problems appear to be more common in these individuals, which O’Brien and Lyons indicated may be due to their risktaking mentality. Martens and others have developed an Athlete Drinking Scale to explore the reasons athletes drink alcohol. Cardiovascular disease Heavy drinking may increase the risk of heart disease and stroke. Klatsky noted that heavier drinking

may increase some of the possible risks to heart and vascular health, including the following: • • • •

Alcoholic cardiomyopathy, or impaired heart function Increased blood pressure Increased risk of hemorrhagic (bleeding) stroke Increased risk of certain heart rate arrhythmias

As we shall see, drinking alcohol in moderation may help to prevent cardiovascular disease, but Cargiulo concludes heavy drinking is associated with increased risk of coronary heart disease and stroke. Individuals susceptible to cardiovascular disease may be prone to a heart attack with heavy drinking. For example, the holiday heart syndrome, an arrhythmia commonly resulting in a rapid heartbeat, may occur with binge drinking around vacations and holidays. Although not normally dangerous, it may be in individuals with underlying heart problems. Cancer Laboratory research has shown that in vitro (that is, in a test tube) alcohol and acetaldehyde cause changes in DNA (the genetic material in body cells) comparable to changes elicited by carcinogens. This DNA damage may occur at an alcohol concentration equivalent to one to two drinks. In those who drink, this finding could be related to the increased risk of certain forms of cancer, including pharyngeal and esophageal cancer, whose tissues have direct contact with ingested alcohol, and also breast and colon cancer. One of the most debated issues is the risk of breast cancer. Possible mechanisms have been identified; in addition to potential DNA damage, alcohol ingestion may also increase estrogen levels, a factor that increases breast cancer risk. Research associating increased incidence of breast cancer with alcohol consumption is epidemiological in nature. The NIAAA indicated that the effect of alcohol intake on the risk for breast cancer remains controversial. In summary, the NIAAA noted that the overall evidence from epidemiologic data seems to indicate that alcohol may be associated with an increase in the risk of breast cancer in the population overall, but the relative effect of moderate consumption is small at the individual level. Recent reviews and studies support these general findings. Zhang and others, in the Women’s Health Study, found that higher alcohol consumption, greater than 30 grams daily, or about two drinks, was associated with a modest increase in breast cancer risk, a relative risk (RR) of 1.32. Gonzalez and Riboli, in a review of studies by the European Prospective Investigation into Cancer and Nutrition, also reported high alcohol intake increases the risk of breast cancer. Michels and others evaluated the role of over 15 dietary variables of interest in the context of breast cancer, and found alcohol intake was one of the few whose association with breast cancer was consistent, strong, and statistically significant. The NIAAA reported that the increase in risk is most clearly evident for women with a family history of breast cancer and those using estrogen replacement therapy, and recommends that women, in conjunction with their healthcare provider, should weigh their potential increased risk for breast cancer against their potential reduced risk for cardiovascular disease in determining whether alcohol consumption should be reduced.

Fetal alcohol spectrum disorders Women who drink should abstain during pregnancy because even moderate consumption of alcohol, or even a single drinking binge, may affect DNA in the embryo and fetus. In a recent review of 66 studies, Burd and others reported that alcohol intake during pregnancy may have numerous adverse effects on the placenta, including placental dysfunction and decreased placental size. Given these effects, alcohol may cause health problems in the newborn, which Green identifies as Fetal Alcohol Spectrum Disorder (FASD). FASD is the term used to describe birth anomalies associated with drinking alcohol while pregnant, and refers to several conditions involving alcohol-related neurodevelopment disorders, birth defects, and other abnormalities in normal development. Fetal alcohol syndrome (FAS) is the most severe of the FASDs. The Centers for Disease Control and Prevention National Center on Birth Defects and Developmental Disabilities indicates that FAS is one of the leading known causes of mental retardation and birth defects. The incidence rate of FAS is very high in the United States, and FAS is currently the major cause of mental retardation in the Western world. The child may experience retardation in growth and mental development as well as facial birth defects (figure 13.3). Fetal alcohol effects (FAE) may be observed in children when full-blown FAS is not present. Children with FAE are easily distracted and have poor attention spans, but do not have the facial features of FAS. Both FAS and FAE are associated with learning disorders in children. The Institute of Medicine has used more specific terms for FAE, including alcohol-related neurodevelopmental disorder and alcohol-related birth defects. No “safe” amount of alcohol during pregnancy has been determined. Thus, the U.S. Surgeon General indicated that the safest approach is abstinence. Obesity Alcohol is a significant source of Calories, about 7 per gram, somewhat comparable to the caloric content of fat. Recent research has indicated that if small amounts of alcohol (5 percent of daily caloric intake) are interchanged for an equivalent caloric intake from carbohydrates, there is no effect on daily energy expenditure. In other words, alcohol Calories themselves will not

Small head circumference Short palpebral fissures

Low nasal bridge

Minor ear anomalies

Eye folds

Indistinct philtrum Micrognathia

Short nose Flat midface Thin upper lip

F I G U R E 1 3 . 3 Common facial characteristics of children with fetal alcohol syndrome (FAS).

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increase body fat as long as total daily caloric intake matches daily caloric expenditure. In general, the NIAAA indicates that the relationship between moderate alcohol consumption and obesity remains inconclusive. In a recent study, Beulens and others reported that moderate alcohol consumption (40 grams daily for four weeks) was not associated with increased adiposity or increased weight circumference. However, Yeomans noted that alcohol may increase energy intake in several ways. Alcohol stimulates the appetite, increasing food intake, and alcohol contains energy. Angelo Tremblay, an esteemed scientist in weight control, and his colleagues recently found that alcohol has no inhibitory effect on food intake and its energy content, and when consumed in conjunction with a high-fat diet promotes overfeeding, a primary determinant of obesity. Additionally, Jequier notes that alcohol ingestion reduces fat oxidation and favors a positive fat balance. These points may underlie the conclusion of the recent study by Wannamethee and others, mainly that higher alcohol consumption is positively associated with both overall and abdominal adiposity, irrespective of the type of drink or whether the alcohol is drunk with meals or not. As noted in chapter 11, reducing alcoholic intake may be an important component of an effective weight control program. Alcohol dependence Alcohol abuse, or excessive intake of alcohol, is the major drug problem in the United States, posing a problem for one in seven males and one in sixteen females, or about one out of every ten drinkers. Over time, alcohol abuse may lead to alcohol dependency, a disorder more commonly known as alcoholism. In a recent review, Cargiulo details many of the adverse health consequences of alcohol dependency, most of which have been discussed previously. The etiology of alcoholism is unknown but probably is related to a variety of physiological, psychological, and sociological factors. Many genes are likely to be involved in increasing an individual’s risk for alcoholism, and Gordis indicates that heavy, long-term use of alcohol modifies brain cells in such a way that certain individuals continue to drink despite growing difficulties. The National Council on Alcoholism suggests that there is no pat definition for alcoholism; it may be evidenced by a variety of behaviors. A deficiency of vitamin B may contribute to many of the neuropsychiatric problems seen in alcoholism. The number of behaviors exhibited by the drinker may be related to various stages in the progression toward alcoholism. Appendix C, a questionnaire developed by the National Council on Alcoholism, provides for an assessment of these behaviors. Positive Effects On the positive side, most recent epidemiological research and reviews have shown that light to moderate consumption of alcohol is associated with lessened mortality. For example, in a recent meta-analysis of the relationship of alcohol consumption to all-cause mortality, Holman and others noted that light drinking (less than 2 drinks per day in males; less than 1 drink per day in females) was associated with a lower relative risk for all-cause mortality compared to abstainers, but that the relative risk returned to normal with moderate alcohol intake and increased to 1.37 for heavy drinkers, those taking six or more 532

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drinks daily. Research suggests that light to moderate alcohol intake reduces risk of coronary heart disease and stroke, a major factor in reducing risk for all-cause mortality. The mechanism is not known, but several have been proposed based on epidemiological and experimental studies. One theory suggests small amounts of alcohol induce a relaxation effect, which may reduce emotional stress, a risk factor associated with CHD. Another theory suggests alcohol decreases platelet aggregability (clotting ability) by increasing the activity of a clot-dissolving enzyme in the blood. Still another theory, proposed by Antinoro and others, indicates that moderate amounts of alcohol may improve blood flow to the brain, which they theorize may help prevent or delay certain brain diseases, such as Alzheimer’s and Parkinson’s, and might help prevent certain forms of stroke. Other mechanisms may be working as well, such as an enhanced insulin sensitivity, which may help in the prevention of the metabolic syndrome and diabetes, both risk factors for CHD. The most prevalent theory involves the effect of alcohol to raise levels of HDL-cholesterol, the form of cholesterol that protects against the development of CHD (see discussion on pages 191–194). A significant number of studies have supported this effect, although the mechanisms have not been determined. Some studies have shown an increase in one form of cholesterol, HDL2, which is believed to be protective. Other studies note an increase in HDL3, which may also elicit a protective effect. Gaziano and others noted alcohol may reduce the risk of heart disease by raising the levels of both HDL2 and HDL3. However, Hines and others noted individuals with a specific genetic predisposition may benefit more from alcohol intake, as they may produce a form of alcohol dehydrogenase that metabolizes alcohol more slowly, leading to greater increases in HDL-cholesterol. Some investigators have theorized that the consumption of certain types of alcoholic beverages, most notably red wine, is responsible for the reported health benefits. Pigments in red wine contain polyphenols and other phytochemicals that may help prevent coronary heart disease by favorable actions on various processes. For example, de Lorimier indicates that phenolic compounds in wine can also increase HDL, have antioxidant activity, decrease platelet aggregation, and promote vasodilation—all potentially beneficial. Others suggest wine components may reduce inflammation in arteries. Chopra and others noted also that alcohol-free red wine may provide some similar health benefits. However, Denke indicates that there is no evidence to support endorsement of one type of alcoholic beverage over another, noting that beer has its own nutritional value. Compared to wine, beer contains more protein and B vitamins, is rich in flavonoids, and has an equivalent antioxidant content, but of different specific antioxidants derived from barley and hops. In a recent study, Mukamal and others found that men who consumed alcohol 3–4 days per week experienced a reduced risk of myocardial infarction, but the type of beverage consumed did not substantially alter this effect. Although these factors may be important, Naimi and others contend that individuals who drink moderately may practice other lifestyle behaviors that reduce the risk for CHD. For example,

Smothers and Bertolucci reported that people who moderate their alcohol intake also engage in more leisure-time activity, which may play an explanatory role in the alcohol-heart disease relationship. As noted in chapter 1, exercise itself may reduce the risk of CHD. However, Mukamal and others, reporting data from over 50,000 males in the Health Professionals Follow-up Study over the course of 16 years, found that moderate alcohol intake, up to two drinks daily, is associated with lower risk for experiencing a heart attack even in men already at low risk for heart disease on the basis of Body Mass Index, physical activity, smoking, and diet. Nevertheless, data from the National Runners’ Health Study, as reported by Williams, reveals that men’s blood pressure increases in association with the amount of alcohol intake, regardless of running level. Thus, it should be reemphasized that although there appear to be some positive health effects associated with light to moderate alcohol intake, or at least no detrimental effects, heavier drinking is another matter. Others have challenged the health benefits of alcohol from another perspective. Fillmore and others proposed that there may be a systematic error in prospective epidemiological mortality studies that have reported moderate regular use of alcohol to be protective against coronary heart disease. They suggest that people classified as abstainers may include those who have decreased or stopped drinking because of illness and thus their illness, and not the lack of alcohol intake, contributed to their increased rate of mortality. Some have classified such individuals as sick quitters. However, Rimm and Moats note that there is substantial evidence to refute this sick quitter hypothesis. For example, the study by Mukamal and others cited previously was from Rimm’s laboratory, a large prospective study showing heart benefits from moderate alcohol intake even when only healthy subjects were studied, men who exercised, ate a good diet, were not obese, and did not smoke. Rimm and Moats also noted that moderate alcohol consumption reduces cardiovascular disease and mortality in individuals with hypertension, diabetes, and existing heart disease. Because of the potential for abuse, addiction, and all types of injuries, abstinence from alcohol or prudent consumption is generally recommended by health authorities. “Low risk” drinking is an emerging term to represent light to moderate alcohol intake. As noted previously, abstinence is the best policy for pregnant women or if you plan to operate a motor vehicle. Health professionals, however, generally support the view that low risk drinking, along with a balanced diet, should not pose any health problem to the average healthy individual. The definition of moderation has varied, but the NIAAA recently indicated that except for individuals at particular risk, consumption of 2 drinks a day for men and 1 for women is unlikely to increase health risks. As risks for some conditions and diseases do increase at higher levels of consumption, men should be cautioned to not exceed 4 drinks on any day and women to not exceed 3 on any day. Nevertheless, although there are actually some possible health benefits associated with alcohol consumption in moderation, health authorities caution that these potential benefits are not sufficient cause to start drinking if you currently abstain. The NIAAA stipulates that moderate alcohol use should not be construed as healthy alcohol use, because numerous individual differences,

such as age, genetics, and metabolic rate, may affect the response to alcohol. You should consult with your physician if you are considering drinking for its possible health benefits.

Ke y C o n c e p t s 䉴 One drink of alcohol contains approximately 13–14 grams of

alcohol, or about one-half ounce. One drink is typically the equivalent of 12 ounces of beer, 4 ounces of wine, and 1.25 ounces of 40-proof whiskey. However, the alcohol content in some beverages may be substantially greater. 䉴 Alcohol is not an effective ergogenic aid, in fact it may actually impair athletic performance, that is, it is ergolytic. 䉴 Consumption of alcohol in moderation appears to cause no major health problems for the normal, healthy adult, and may actually confer some health benefits. However, alcohol may be contraindicated for some, such as women during pregnancy. Heavy drinking is associated with numerous health problems.

C h e c k f o r Yo u r s e l f Visit a local beer/wine store that carries a wide variety of products, including microbrews and fortified wines. Check the labels for percentage alcohol content, listing those from lowest to highest. Calculate how much alcohol would be in a standard drink from each.

www.niaaa.nih.gov This Website provides detailed information on a wide variety of alcohol-related topics. For example, if you want to decrease the amount of alcohol you drink, click on Publications and then on Pamphlet in the For the Public section to access the pamphlet, How to Cut Down on Your Drinking.

Caffeine: Ergogenic Effects and Health Implications Various stimulants have been used in attempts to enhance health and sports performance, including caffeine.

What is caffeine and in what food products is it found? Caffeine is an odorless, bitter, white alkaloid that appears naturally in many plants, and is found in many of the foods and beverages that we consume every day, such as coffee, tea, colas, caffeinated waters, juices, energy drinks, sports drinks and sports bars, and chocolate; it is the most popular social drug in the United States (figure 13.4). Gupta indicates that up to 90 percent of Americans consume caffeine daily. It is also found in various dietary supplements, such as kola nuts and guarana, and even some over-the-counter stimulant supplements targeted to athletes; most recently, caffeine has been marketed as performance www.mhhe.com/williams9

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TABLE 13.3 Caffeine content in selected products

F I G U R E 1 3 . 4 Caffeine is the most popular social drug in the United States. About 90 percent of all adults consume caffeine in one form or another, mainly as coffee.

candy, such as Jolt Caffeine-Energy Gum and Buzz Bites, a chocolate chew candy, and has been added to foods such as ice cream and oatmeal, as well as several brands of beer. Yet caffeine is legally classified as a drug and has some powerful physiological effects on the human body. A normal therapeutic dose of caffeine may range from 100–300 milligrams. Some approximate amounts in the beverages we consume are 80–135 mg in a cup of perked coffee, 40–60 mg in a cup of tea, and 35–45 mg in a can of cola. The caffeine content of various products is presented in table 13.3.

What effects does caffeine have on the body that may benefit exercise performance? Caffeine functions as a stimulant of the nervous system. Its primary mode of action is to block the neurotransmitter adenosine, and thus influence a wide variety of metabolic processes throughout the body. Caffeine stimulates heart function, blood circulation, and release of epinephrine (adrenaline) from the adrenal gland. Epinephrine, also a stimulant, augments these effects and also, in conjunction with caffeine, stimulates a wide variety of tissues. Together they potentiate muscle contraction, raise the rate of muscle and liver glycogen breakdown, increase release of FFA from adipose tissue, and increase use of muscle triglycerides. One of the most observed effects at rest is an increase in blood levels of FFA. These varied physiological responses are mediated by the action 534

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Product

Serving size

Caffeine (milligrams)

Coffee, brewed

8 ounce cup

80–135

Coffee, instant

8 ounce cup

65–100

Coffee, decaffeinated

8 ounce cup

3–4

Coffee, Starbucks

16 ounce cup

330

Tea, black or green

8 ounce cup

30–50

Hot cocoa

8 ounce cup

15

Sodas, cola

12 ounce can

35–45

Sodas, high caffeine

12 ounce can

55–70

POWERade Advance

16 ounce bottle

95

Energy drinks

8 ounce can

80–120

Performance candy

1 Buzz Bite

100

Stimulants

1 Vivarin tablet

200

Dietary supplements

5 grams guarana

250

Note: Check labels of over-the-counter stimulants and dietary supplements for caffeine content.

of caffeine, or epinephrine, to enhance appropriate intracellular functions in specific cells, including functions such as increased calcium release to excite muscle contraction or elevated enzymic activity to release FFA from adipose tissue cells. Caffeine also enhances neural excitability in the brain and related psychological processes, increasing alertness and a feeling of well-being. Ferré indicates that caffeine may help prevent adenosine from inhibiting the stimulant effects of dopamine. Caffeine is degraded rapidly in the liver to dimethylxanthines, metabolites which may also affect metabolism favorably. Overall, caffeine may influence central and peripheral metabolic processes, as well as psychological processes, to help delay the onset of fatigue and has been theorized to enhance performance in many types of exercise, including endurance, strength, speed, and power.

Does caffeine enhance exercise performance? Caffeine has been studied for its possible ergogenic effects for nearly 100 years. Early research focused on improvements in strength, power, and psychomotor parameters such as reaction time. However, since research by Costill’s laboratory in the late 1970s suggested caffeine could increase endurance, many researchers have investigated the effects of caffeine on fat metabolism as a means to enhance performance of endurance athletes, such as marathoners, primarily because of caffeine’s alleged potential to

spare the use of muscle glycogen. In recent years, increased research attention has also refocused on the ergogenic potential of caffeine in tasks of higher exercise intensity and shorter duration. Literally hundreds of studies have been conducted to test the ergogenic effectiveness of caffeine. Considerable differences exist in the experimental designs of caffeine studies in such aspects as caffeine delivery system (caffeine in coffee or capsule form), caffeine dosage (3–15 mg per kg body weight), the type of exercise task (power, strength, reaction time, short-term endurance, prolonged endurance), the intensity of the exercise (submaximal exercise, maximal exercise), the training status of the subject (trained, untrained), the preexercise diet (high-carbohydrate, mixed), the subjects’ caffeine status (user, abstainer), and individual variability (reactor, nonreactor). These differences complicate interpretation of the results. Additionally, some investigators have combined caffeine with other related stimulants, such as ephedrine and theophylline. Caffeine appears to be a popular ergogenic aid among athletes. For example, in several reports Desbrow and Leveritt noted that almost 90 percent of athletes competing in the World Championship Ironman Triathlon competition used caffeine supplements, ranging from coffee before and caffeinated gels and energy drinks during the race, and 75 percent believed that caffeine was ergogenic to their performance. They also noted that blood testing after the race indicated caffeine levels were associated with enhancement of endurance performance. Overall, research indicates that caffeine supplementation may be an effective ergogenic for a variety of exercise tests and may improve performance by different mechanisms. Several reviews and a meta-analysis regarding the effect of caffeine on physical performance have been published recently, and the interested reader is referred to the articles by Armstrong, Graham, Doherty and Smith, and Kalmar and Cafarelli. Based on these reviews and an independent analysis of key studies, the following points represent a general summary of the available research. Effect on Mental Alertness Caffeine can increase alertness, which may improve simple reaction time. Doses of 200 milligrams have been effective, particularly when subjects are mentally fatigued. In several studies, Hogervorst and others have found that caffeine, as part of a carbohydrate-electrolyte solution or performance bar, improved cognitive function in trained athletes following an endurance cycling task. Rao and others reported that energy drinks containing caffeine and glucose can enhance behavioral performance during demanding tasks requiring visual selective attention. Larger doses, above 400 milligrams, may increase nervousness and anxiousness in some individuals, and thus may adversely affect performance in events characterized by fine motor skills and control of hand steadiness, such as pistol shooting. Also, although caffeine may enhance visual attention, Hespel and others noted that in sports involving rapid visual stimuli, such as soccer, care must be taken not to overdose because visual information processing might be impaired. Effect on Muscle Contraction In her review, Jayne Kalmar from York University in Canada indicated that caffeine may influ-

ence muscle performance by stimulating the nervous system at various points along the motor pathway to the muscle. Caffeine also may increase the release of calcium from the sarcoplasmic reticulum in the muscle, possibly increasing the force of muscle contraction and delaying the onset of fatigue. Allen and others noted that impaired calcium release from the sarcoplasmic reticulum has been identified as a contributor to fatigue in isolated skeletal muscle fibers. Tarnopolsky and Cupido evaluated this direct effect of caffeine on muscle contraction in both habitual and nonhabitual caffeine users, stimulating the muscle electrically at different intensities to induce a 2-minute tetanic contraction. They found that caffeine potentiated the force of muscle contraction during the last minute of stimulation and suggested that the data support the hypothesis that some of the ergogenic effect of caffeine in endurance exercise performance occurs directly at the skeletal muscle level. Some studies support such a direct effect. Kalmar and Cafarelli reported significant improvement in a maximal isometric endurance task just over 1 minute in duration. Forbes and others found that consuming an energy drink, in an amount providing 2 milligrams caffeine per kilogram body weight, increased upper body muscular endurance in the bench press; similar effects were reported by Woolf and others with a higher dose of caffeine. In his review, Graham noted that although there are fewer studies with resistance exercise, the available literature would suggest that caffeine could increase endurance in repeated contractions. Effect on High-Intensity Anaerobic/Aerobic Exercise The vast majority of earlier studies revealed that caffeine did not improve performance in events characterized by high-intensity anaerobic/aerobic exercise tasks lasting less than 30 minutes, and this is the general conclusion of the review by Williams, which focuses on high-intensity exercise performance. More recent studies are inconsistent. Several support Williams’ conclusion. For example, in a well-controlled crossover study, Paton and others investigated the effect of caffeine (6 mg/kg) on repeated 20-meter sprints in well-trained male team-sport athletes and observed no significant effect on mean sprint performance and fatigue over ten sprints. Forbes and others reported no effect of caffeine on repeated 30-second Wingate cycling tests, while Beck and others also reported that a caffeine-containing supplement did not enhance performance in several tests of anaerobic capacity. In a well-designed study, Crowe and others studied the effect of caffeine on high-intensity cycling (two 60-second maximal cycling bouts) and suggested that caffeine could actually be detrimental to anaerobic performance. In the trial with caffeine, potentially negative effects included significantly higher blood lactate and significantly slower time to peak power in the second exercise bout. This is one of the very few exercise studies to suggest a possible ergolytic effect of caffeine. However, other well-designed, double-blind, placebo, crossover studies have shown caffeine-induced improvement in several high-intensity exercise tasks. For example, Schneiker and others, using a cycle ergometer test designed to mimic team-sport play, found that caffeine can significantly enhance performance of prolonged, intermittent-sprint ability in competitive, male, team-sport www.mhhe.com/williams9

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athletes; Bruce and others reported increased mean power and improved 2,000-meter rowing time in eight competitive rowers; Collomp and others reported faster 100-meter swim times in highly trained swimmers; Wiles and others noted significantly faster run times for 1,500 meters, particularly increased speed in the latter part of the race, in trained middle-distance runners; Jackman and others reported increased time to exhaustion when exercising at 100 percent VO2 max, a time approaching 5 minutes; Glaister and others found that caffeine may benefit performance in both single and multiple sprint sports. Stuart and others reported significant improvements in repetitive bouts of speed and power typical of high-intensity team sports such as rugby; Del Coso and others found increased power in short-term maximal cycling bouts performed during a prolonged cycling task. Effect on FFA Mobilization and Use One of the first theories promoting caffeine as an effective ergogenic aid for aerobic endurance exercise suggested an increase in mobilization and use of FFA during exercise, and a potential sparing of muscle glycogen. It is well established that caffeine may raise serum FFA levels at rest just before exercise, but there appears to be some controversy regarding serum FFA levels during exercise when trials with and without caffeine are compared. A number of studies that involved subjects who consumed caffeine beverages regularly and who also used a small dose of caffeine (5 mg/kg) have reported no significant differences between caffeine and placebo trials. The most likely reason is that exercise itself, as a stressor, stimulates epinephrine release and raises FFA levels comparable to the small dose. However, other studies that have involved subjects who were not regular caffeine users or who abstained from caffeine use for 4–7 days and which also employed large doses of caffeine (15 mg/kg) have noted significantly higher levels of FFA during exercise compared to placebo trials. Bucci reported fifteen studies in which caffeine increased FFA over the effect of exercise alone. Whether or not there are changes in plasma FFA may be irrelevant, for as Tarnopolsky notes, plasma concentrations do not provide us with appropriate information regarding the flux of the FFA, that is, the rate at which it appears in the blood from the adipose tissue and the rate of entry into the muscle cell. Even though caffeine may elevate FFA during exercise, whether the use of fat as an energy source is increased during exercise is debatable. Several reviewers have noted an inconsistency in the results when the respiratory quotient (RQ) was used to assess fuel utilization; the RQ may serve as a general guide to the percentage use of carbohydrate and fat during submaximal, mildto moderate-intensity exercise. Several studies provide strong evidence that caffeine may not increase fat utilization during exercise. Graham and others monitored fatty acid metabolism directly at the leg level during exercise and found that caffeine (6 mg/kg), although stimulating the sympathetic nervous system, did not alter the fat metabolism in the monitored leg. In a related study, Mora-Rodriguez and Coyle infused epinephrine intravenously in low, moderate, and high amounts to evaluate the effect on fat utilization during low-intensity exercise. Although elevations in plasma epinephrine progressively increased whole body lipolysis, fatty acid oxidation 536

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decreased. Based on the most recent research, Graham noted that it appears unlikely that increased fat oxidation is the prime ergogenic mechanism underlying caffeine use as an ergogenic aid for aerobic endurance exercise. Effect on Muscle Glycogen Sparing Previously, several welldesigned studies had supported the concept that caffeine would increase fat utilization and spare muscle glycogen, which could contribute to enhanced endurance performance. About 25 years ago, Essig noted that caffeine elicited an increased utilization of muscle triglycerides during exercise and spared the use of muscle glycogen. In studies that have taken muscle biopsies, caffeine has been shown to exert a glycogen-sparing effect. Well-designed studies headed by Lawrence Spriet and Terry Graham from Guelph University in Canada show clearly that caffeine will spare the use of muscle glycogen during the first 15 minutes of exercise, supporting the research findings of Essig years ago. In the study by Spriet and others, no crossover design was used, for all subjects received the placebo first and then 1 week later, the caffeine. Muscle biopsies were taken at the point of exhaustion in the placebo trial. During the caffeine trial, the subjects were stopped for a muscle biopsy at the exact same time they reached exhaustion in the placebo trial; they were still performing but were stopped for the biopsy and then continued cycling. The muscle glycogen was higher in the caffeine trial compared to the placebo trial, strong evidence of a glycogen-sparing effect that allowed the athletes to continue to cycle. However, more contemporary studies suggest caffeine does not spare muscle glycogen during exercise. As noted previously, Graham and others found no effect of caffeine on fat metabolism during exercise while monitoring fuel use at the leg level, and they also reported no effect on carbohydrate metabolism. In another study from Graham’s research group, Greer and others reported that neither caffeine (6 mg/kg) nor the related stimulant theophylline (4.5 mg/kg) affected muscle glycogen utilization during cycling exercise at 80 percent VO2 max until exhaustion. Laurent and others used nuclear magnetic resonance spectroscopy to evaluate muscle glycogen levels before and after exercise (cycling 2 hours at 65 percent VO2 max), and found that caffeine (6 mg/kg) did not spare use of muscle glycogen in glycogen-loaded subjects. Thus, based on current research findings from his own and other research groups, Graham indicated that caffeine does not appear to induce a glycogen-sparing effect during exercise. Effect on Aerobic Endurance Performance In its recent position statement on fluid replacement during exercise, the American College of Sports Medicine noted that caffeine intake may help sustain performance. Numerous studies have reported significant improvements in endurance performance following caffeine ingestion. For example, in a recent study Kirk Cureton and his associates at the University of Georgia reported that caffeine increased total work production in highly trained cyclists by 15–23 percent in a 15–minute performance ride performed after 135 minutes cycling intermittently at 60 to 75 percent VO2 max. Hogervorst and others reported that consuming performance bars containing caffeine (100 mg) before and during a 2.5-hour cycling task improved performance in a subsequent ride to exhaustion at

75 percent VO2 max. Greer and others also reported that both caffeine (6 mg/kg) and theophylline (4.5 mg/kg) enhanced performance during cycling exercise at 80 percent VO2 max until exhaustion. In their classic study, Graham and Spriet used elite distance runners as subjects and found that caffeine improved mean run time to exhaustion at 85 percent of VO2 max from 49.2 minutes following the placebo to 71.0 minutes after caffeine (9 mg/kg body weight), a 44 percent improvement. Performance on a comparable cycling test to exhaustion revealed similar results. In a well-designed, ecologically valid field study, Bridge and Jones reported that caffeine significantly improved 8-kilometer (~5 miles) race time by 23 seconds compared to the placebo trial. Norager and others even found that caffeine can improve endurance performance in healthy men and women 70 years of age and older. In most studies, the caffeine was taken 1 hour prior to performance, but French and others found that caffeine was effective even if taken immediately before the performance task. In their recent meta-analysis, Doherty and Smith confirmed the ergogenic effects of caffeine in a variety of exercise tasks, particularly so in tests of aerobic endurance (see figure 13.5). Jeukendrup and Martin, in their review on how to improve cycling performance, quantified the ergogenic effects of caffeine, suggesting that low doses could improve 40-kilometer cycling performance by 55–84 seconds. No wonder caffeine is popular with professional cyclists. Effect on Ratings of Perceived Exertion (RPE) In many studies showing improved performance, the psychological effect

F I G U R E 1 3 . 5 Caffeine may enhance performance in a wide variety of exercise endeavors, particularly events involving aerobic endurance.

of caffeine was hypothesized as the cause. A number of studies have shown that caffeine may exert a stimulating effect on psychological processes, such as alertness and mood, which may diminish the perception of effort during exercise and thereby improve performance. For example, Cole and others had subjects perform cycling tasks at three different RPE levels. At each level, the subjects produced more work in 10 minutes following caffeine ingestion as compared to the placebo. Although the subjects perceived the work tasks to be identical by the RPE scale, they actually generated more work with caffeine. In a recent meta-analysis of 21 studies, Doherty and Smith concluded that in comparison to placebo, caffeine reduced the RPE during exercise by 5.6 percent while improving exercise performance by 11.2 percent; the authors indicated that the effect of caffeine on the RPE could account for approximately 29 percent of the improvement in performance. The effect of caffeine to reduce the psychological effort of exercise appears to be an important factor underling its ergogenic effect. However, Ahrens and others reported that caffeine had little effect on RPE during aerobic step dancing or treadmill walking, and indicated it would not be prudent for an exercise instructor to recommend caffeine to reduce the RPE in such workouts. Effect of Dietary Carbohydrates Previous research has shown that carbohydrate loading and having a high-carbohydrate breakfast prior to competition may negate the metabolic effects of caffeine. High-carbohydrate levels stimulate insulin release, which appears to block the effect of caffeine in raising FFA levels. However, given the conflicting data as to whether or not plasma FFA accurately reflect the FFA flux, this observation may not be too meaningful. Moreover, the subjects in the study by Graham and Spriet did load with carbohydrates for several days prior to the exercise task, both in the placebo and caffeine trials, and it did not appear to affect the ergogenic effect of caffeine adversely. Carbohydrate and caffeine intake may have other implications for exercise performance. Yeo and others reported that consuming caffeine with carbohydrate during prolonged aerobic exercise will significantly increase the oxidation of exogenous carbohydrate; exogenous carbohydrate oxidation was 0.72 gram per minute with glucose/caffeine intake, but only 0.57 gram per minute with glucose alone. The investigators suggested caffeine may facilitate intestinal absorption of glucose. The increased oxidation of exogenous carbohydrate could be beneficial to an endurance athlete. However, the authors also noted a trend to increased oxidation of endogenous carbohydrate, which might not be favorable for some prolonged endurance events if there was a more rapid depletion of muscle glycogen. Conversely, Hulston and Jeukendrup found that ingestion of both caffeine (5.3 mg/kg) and carbohydrate during aerobic endurance exercise did not influence exogenous carbohydrate oxidation. Moreover, they reported that the co-ingestion of caffeine with carbohydrate during endurance exercise significantly enhanced time trial performance when compared to carbohydrate alone or placebo. Research has also shown that caffeine ingestion does not impede the resynthesis of muscle glycogen during the carbohydrateloading protocol. www.mhhe.com/williams9

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Effect of Caffeine Status One possible factor determining whether caffeine is an effective ergogenic aid is the caffeine status of the subjects. In many of the studies that report an ergogenic effect, subjects abstained from caffeine use for 2–4 days prior to the experiment; they became caffeine-free for several days to possibly heighten the caffeine effect when taken. This abstention period was based on some research reporting no effects of caffeine on epinephrine or FFA levels if subjects abstained for less than 1 day. Other research documented a decreased sensitivity to caffeine following 6 weeks of increased caffeine ingestion; that is, the epinephrine level was decreased during exercise following this period of increased caffeine intake. However, in their review, Graham and Spriet suggest that caffeine withdrawal may have little effect on actual performance, and that subjects may consume caffeine products up to the day of the event. Effect of Delivery System Another factor influencing caffeine’s effectiveness may be how it is consumed. Graham and others compared the effects of consuming the same dose of caffeine in coffee or as a capsule in water. In a well-designed, double-blind, repeated-measures study with 5 trials (3 caffeine and 2 placebo), they found that although the plasma epinephrine increased with the coffee, the increase was significantly greater with the caffeine capsule. Additionally, the caffeine capsule was the only treatment to improve exercise performance, a treadmill run to exhaustion at 85 percent VO2 max. They suggested some component or components in coffee may moderate the effect of caffeine. However, other studies have reported significant ergogenic effects when coffee was used to deliver caffeine. Moreover, McLellan and Bell recently reported that consuming coffee 30 minutes prior to taking capsulated caffeine did not negate its beneficial ergogenic effect on cycling endurance performance. Drinking coffee would not seem to impair the potential ergogenic effect of caffeine tablets. Effect of Exercise in the Heat Caffeine has been classified as a diuretic and also stimulates metabolism. Theoretically, increased water losses and an elevated metabolism before competition could impair exercise performance under warm, humid environmental conditions, possibly because of retarded sweat losses and excessive increases in body temperature. However, research has shown no changes in sweat loss, plasma volume, or body temperature following caffeine ingestion. For example, Roti and others reported no effect of 3 or 6 mg of caffeine on thermoregulation during 90 minutes of walking under hot conditions (37.7ºC; 100ºF). Moreover, Cohen and others reported that caffeine ingestion did not impair performance in a 13.1-mile (21.1 km) half-marathon run outdoors under hot, humid conditions. Although running performance was not impaired by caffeine, neither was it improved. Millard-Stafford and others also noted that consuming a caffeinated sports drink during prolonged exercise in the warm, humid conditions maintains hydration and cardiovascular and thermoregulatory functions as well as a noncaffeinated sports drink. Lawrence Armstrong, from the University of Connecticut, is an international scholar on caffeine and thermoregulation during exercise. In their most recent review, Armstrong and others concluded that, in contrast to popular beliefs, caffeine consumption does not result in hypohydration, water-electrolyte imbalances, hyperther538

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mia, or impaired exercise-heat tolerance. The ACSM also concludes that caffeine consumption will not markedly alter daily urine output or hydration status. Athletes will not incur detrimental fluid-electrolyte imbalances if they consume caffeinated beverages in moderation and eat a typical diet. Additionally, Armstrong and others recently reported that consuming caffeine, either 3 or 6 milligrams per kilogram body weight for five days, did not cause hypohydration, and questioned the widely accepted notion that caffeine consumption acts chronically as a diuretic. The Placebo Effect As mentioned in chapter 1, subjects in a study may experience a placebo effect if they think they received an effective ergogenic, such as caffeine. In a unique study, Beedie and others told subjects they would receive either a placebo, moderate, or high dose of caffeine before performing a 10-kilometer cycle time trial. Actually, in all trials the subjects received only a placebo; no caffeine was provided. Afterwards the subjects were asked which treatment they received, and when they thought they had received caffeine, their performance was better, and even more so when they thought they received the high dose. Although this study provides evidence of a clear placebo effect, Foad and others have shown there may also be clear pharmacological effects of caffeine on exercise performance. In a meticulous study with male competitive cyclists, six separate tests were used to establish a baseline for 40-kilometer cycling time-trial performance. The cyclists then performed eight more trials, two each under four experimental conditions (AA, BA, AB, BB) involving the interaction of receiving (A) or not receiving (B) caffeine and being informed they had (A) or had not (B) received caffeine. They found that caffeine exerted a pharmacological ergogenic effect, but also noted a possible beneficial psychological placebo effect as the subjects performed somewhat better when informed they were given caffeine but were not. There was also a possible negative placebo (nocebo) effect when subjects were correctly informed that they received no caffeine. Their data support the ergogenic efficacy of caffeine but suggest that both positive and negative expectations may impact performance. Effect of Dosage: Permissibility Caffeine use has been widespread in sports for over a century, and its legality has varied. The International Olympic Committee (IOC) banned the use of caffeine as a drug prior to the 1972 Olympics. However, because caffeine is a natural ingredient in some beverages that athletes consume, the IOC removed it from the doping list from 1972 to 1982. The use of large amounts of caffeine was again banned for the 1984 Olympic games, probably because research had suggested that caffeine could artificially improve performance. Olympic athletes were permitted to consume small amounts of caffeine, but the use of large doses was grounds for disqualification. Until 2004, the maximal dose that could be used without exceeding the legal limit for doping approximated 8–10 mg/kg body weight. For a 70-kg athlete this would be 560–700 milligrams of caffeine, or about 4–6 cups of coffee or 3 Vivarin tablets. In their study Bruce and others found that many subjects consuming 9 mg caffeine/kg body weight exceeded the legal limit for doping in effect at that time. However, effective January 1, 2004, the World Anti-Doping Agency (WADA), in conjunction with the medical commission of the Inter-

national Olympic Committee, removed caffeine from the list of stimulants prohibited for use by athletes. Although research suggests that caffeine is an effective ergogenic aid for various types of athletic endeavors, WADA felt that the doping list should be adjusted to reflect changing times. The removal of caffeine from the prohibited list may be a reflection of the increased prevalence of caffeinated beverages, such as specialty coffees, fortified colas, energy drinks, and even sport drinks. These drinks, which may be larger and contain more caffeine, may be consumed in quantity by athletes. As noted earlier, caffeine is also found in a wide variety of other food products. Currently, athletes need not worry about drinking caffeinated beverages and then being tested positive for use of caffeine as a performance-enhancing substance. However, WADA has placed caffeine in its monitoring list, meaning that caffeine levels in athletes are tested and if caffeine abuse increases, it may be returned to the prohibited list. Individuality In general, studies have not reported a decrease in performance following caffeine ingestion. However, it should be noted that individuals vary in their responses to any drug. In their recent caffeine study, Jenkins and others noted that although there was a significant ergogenic effect overall, the effects varied considerably among individual cyclists. In several of the studies the investigators reported that some subjects had adverse reactions to the caffeine and thus had an impaired performance. Caffeine appears to be an effective ergogenic aid in doses that are both safe and legal. However, some athletes believe taking caffeine may be considered unethical because it is an artificial means of enhancing performance. Given its safety and legality, the decision to use caffeine as a performance-enhancer rests with the ethical standards of the individual athlete. Although combining ephedrine with caffeine (as discussed in the next section) may increase the ergogenic effect of caffeine alone, ephedrine use may be illegal—so its use to increase sports performance is unethical. Self-Experimentation If you are considering using caffeine as a potential ergogenic aid, it is wise to experiment with its use in training prior to use in competition. You might start by taking 200–400 milligrams of caffeine about an hour prior to some of your workouts. For example, if you are a distance runner, do your long runs periodically with and without the coffee or other caffeine source, and judge for yourself if it works for you. To make it a more valid case study, have someone randomly give you, blinded, a placebo (vitamin capsule) or caffeine capsule before the runs, but without informing you which until you have done each several times. Try this procedure also after abstaining from caffeine for 4–5 days. Keep a record of your feelings and times after the runs so you can compare differences.

Does drinking coffee, tea, or other caffeinated beverages provide any health benefits or pose any significant health risks? This is one of the most hotly debated questions over the past half century, as about 90 percent of American adults use caffeine in one form or another, mainly coffee. After water, coffee is the world’s most widely consumed

beverage. In the early 1970s and 1980s a number of epidemiological studies linked coffee or caffeine consumption with the development of a variety of health problems, including heart disease and associated risk factors such as high serum cholesterol and high blood pressure; pancreatic cancer; fibrocystic breast disease; osteoporosis; and pregnancy-related problems such as infertility, miscarriages, low birth weight, and birth defects. Conversely, other epidemiological studies have shown no relationship between coffee or caffeine consumption and these health problems. Investigators have looked at a variety of factors, including different sources of caffeine such as coffee versus tea, regular versus decaffeinated coffee, and even the method of preparing coffee, such as filtered versus boiled. Investigators suggest that some of the potential health benefits of coffee and tea may be attributed to substances other than caffeine found in these beverages. Many of the earlier reported adverse findings associated with caffeine consumption were derived from rather small epidemiological studies or from animal research using rather high doses of caffeine. However, more contemporary, larger epidemiological studies have been conducted, and several recent reviews have evaluated these reports and summarized the effect of caffeine on a variety of health problems. The following represent the key points presented in the reviews by Browne, Campos and Baylin, Cornelius and El-Sohemy, Higdon and Frei, Schardt, Tufts University, van Dam and Hu, James, Signorello and McLaughlin, and the Consumers Union, as well as other independent sources. Cardiovascular Disease and Associated Risk Factors Caffeine is a stimulant that may affect heart function. In some individuals it may cause a slight arrhythmia, or irregular heart beat. However, recent research by Frost and Vestergaard reported that low to moderate consumption of caffeine, as coffee, does not cause the most common type of serious arrhythmia known as atrial fibrillation. Caffeine may also acutely increase blood pressure in individuals who are caffeine sensitive and also in individuals who are under stress. Not all studies have shown that increased caffeine use is associated with high blood pressure. For example, Schardt cited one study that followed over 150,000 women for 10 years and found those who drank regular or decaffeinated coffee had no higher risk of hypertension than non-coffee drinkers. However, in a recent critical review of dietary caffeine and blood pressure, James concluded that findings from experimental and epidemiologic studies converge to show that blood pressure remains reactive to the pressor effects of caffeine in the diet; overall, the impact of dietary caffeine on population blood pressure levels is likely to be modest, probably increasing blood pressure by about 4 and 2 mmHg for systolic and diastolic blood pressure, respectively. Todd and others reported that caffeine (6 mg/kg) consumed one hour prior to resistance training elevated systolic blood pressure by 8–10 mmHg. They recommended that to prevent elevated blood pressure, individuals at risk should monitor caffeine intake before undertaking resistance exercise. Several recent reviews have investigated the relationship between coffee consumption and serum lipid levels, noting an inconsistency in the results of most studies. Some studies have shown that both caffeinated and decaffeinated coffee may raise www.mhhe.com/williams9

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serum cholesterol, but others have reported no effects. In some cases where the cholesterol levels rose, the authors noted the increases were of little clinical significance. Increased serum cholesterol levels have been associated with the method of preparation, particularly boiling coffee as practiced in Scandinavia and other parts of the world. Several cholesterol-raising substances (cafestol and kahweol) have been found in the oil droplets formed in the boiling process. These substances are removed when coffee is filtered, the major means of coffee preparation used in the United States and Canada. Vlachopoulos and others found that chronic coffee consumption, with daily amounts providing more than 450 milligrams of caffeine, exerted a detrimental effect on stiffness of the aortic artery, which may increase the risk of cardiovascular disease. As noted, caffeine may interfere with the metabolism of adenosine, a substance that relaxes arteries. In a related study, Namdar and others reported that caffeine (a dose corresponding to 2 cups of coffee) consumed before exercising may reduce blood flow to your heart during the workout. They suggested that caffeine may also block the relaxing effect of adenosine on the coronary arteries. Homocysteine may be a risk factor for CHD, and Verhoef and others recently found that coffee may increase homocysteine levels in the blood. The increase is partly attributed to its caffeine content, but other factors may contribute as well. Caffeine raised homocysteine levels 5 percent, while coffee containing caffeine raised it 11 percent. The effect of such an increase on the risk of CHD has not been determined. Green tea contains caffeine, and has been studied for its potential effects to prevent diabetes, as well as cardiovascular disease and cancer. However, most investigators believe the health benefits of green tea may be associated with another of its constituents, epigallocatechin gallate (EGCG). EGCG is an antioxidant that has been found in animal studies to help reduce some of the risk factors associated with these diseases. In their reviews of the health benefits of green tea, Wolfram and Cabrera indicate research with humans is still limited and at the current time insufficient to provide recommendation for consumption in Western diets. Although caffeine may affect some of the risk factors associated with heart disease, recent reviews suggest the risk of developing coronary heart disease or having a heart attack is rather low. Relative to coffee, Cornelis and El-Sohemy indicated that coffee is a complex mixture of compounds that may have either beneficial or harmful effects on the cardiovascular system, and noted studies examining the association between coffee consumption and coronary heart disease have been inconclusive. This inconclusiveness may be attributed to the nature of the studies reviewed. In a recent meta-analysis, Sofi and others included 13 case-control studies and 10 cohort studies. Case-control studies are retrospective in nature and are not as powerful as cohort studies, which are prospective studies following individuals over the course of years. In their analysis of the case-control studies, Sofi and others found a significant relationship between coffee consumption and coronary heart disease, an odds ratio (OR) of 1.83 when drinking more than 4 cups of coffee daily and an OR of 1.33 when drinking 3–4 cups daily. There was no significant effect when drinking 2 cups of coffee or less daily. In their analysis of the more powerful 540

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cohort studies, no significant association was found between daily coffee consumption in any amount and coronary heart disease. Based on contemporary research, most health professional groups, such as the American Heart Association, recommend that moderate coffee consumption, about 1–2 cups daily, is safe and not associated with heart disease. However, the effects of consuming greater amounts of coffee are not as well known. James indicated that the effect of caffeine to increase blood pressure could account for premature deaths in the region of 14 percent for coronary heart disease and 20 percent for stroke, and indicates that strategies for encouraging reduced dietary levels of caffeine deserve serious consideration. Individuals who are hypertensive, or who are under stress, or who may have other risk factors for heart disease, should consult their physician regarding the use of caffeine. Type 2 Diabetes Tufts University recently noted that since 2002 more than 20 studies have suggested that coffee somehow helps ward off type 2 diabetes. For example, Pereira and others, who followed postmenopausal women over the course of 11 years, reported that coffee intake, especially decaffeinated, was inversely associated with a reduced risk of type 2 diabetes. Women who drank the most coffee, more than 6 cups daily, reduced their risk by 22 percent. In their review of 9 cohort studies, van Dam and Hu concluded that the data supports the hypothesis that habitual coffee consumption is associated with a substantially lower risk of type 2 diabetes. However, they note that longer-term intervention studies of coffee consumption and glucose metabolism are warranted to examine the mechanisms underlying the relationship between coffee consumption and type 2 diabetes. Tufts University notes that coffee contains various healthful nutrients, such as chromium, magnesium, and boron. Van Dam also noted the finding that higher consumption of decaffeinated coffee was associated with a lower risk of type 2 diabetes. This suggests other components in coffee besides caffeine, such as chlorogenic acid and lignans, may be involved. For example, chlorogenic acid can delay glucose absorption. Cancer The American Cancer Society, after reviewing the available scientific evidence, indicated there is no known association between the consumption of coffee, tea, or other caffeinated beverages and the development of any type of cancer. In support of this viewpoint, Michels and others presented data from two large epidemiological studies involving men and women, and reported that the consumption of caffeinated coffee, tea with caffeine, or caffeine was not associated with incidence of colon or rectal cancer. Also, Schardt recently noted that a review of 66 studies of coffee and pancreatic cancer and 25 studies with kidney cancer concluded coffee was unlikely to pose a substantial risk. Neuroprotective Effects Caffeine is known to improve alertness and reaction time in individuals, which are indicators of its stimulating effect on the brain. Caffeine intake may also be associated with less cognitive decline with aging. van Gelder and others recently studied the relationship between coffee consumption and cognitive decline over 10 years in elderly men, and found that an

inverse and J-shaped association may exist between the number of cups of coffee consumed and cognitive decline, with the least cognitive decline for men consuming three cups of coffee per day. In their recent study, Ritchie and others concluded that the psychostimulant properties of caffeine appear to reduce cognitive decline in women, especially at higher ages. In his review, Schardt cites a meta-analysis of 13 studies indicating that drinkers of regular coffee, but not decaffeinated, had a 30 percent lower risk of Parkinson’s disease than nondrinkers. Consuming about 1 or 2 cups of coffee daily, about 100 to 200 milligrams of caffeine, appears to be enough. One theory is that caffeine may help prevent the decline in dopamine-secreting neurons during aging. Parkinson’s disease is theorized to be caused by a deficiency of dopamine. Osteoporosis Factors underlying the development of osteoporosis are discussed in detail in chapter 8. Essentially, calcium loss may lead to osteoporosis. For now, we may note that caffeine tends to accelerate the loss of calcium from bones and lead to its excretion in the urine. However, the amount is very small, approximating only 5 milligrams of calcium loss for every cup of coffee. Using 2 tablespoons of milk in the coffee would replace the amount of lost calcium. In a recent report, the National Institutes of Health indicated caffeine use does not cause significant losses of calcium. However, drinking milk or eating calcium-rich foods is highly recommended if you drink caffeinated beverages. Pregnancy-Related Health Problems Animal research has suggested that very high doses of caffeine, administered directly into the stomach via tubes, could impair fertility or interfere with fetal development, causing detrimental pregnancy consequences such as miscarriage, low birth weight, or birth defects. However, other animal research, administering caffeine in fluids as normally consumed by humans, did not produce such effects. In a meta-analysis of 32 human studies, Fernandes and others concluded that there is a small, but statistically significant, increase in the risks for spontaneous abortion and low birthweight babies in pregnant women consuming more than 150 milligrams of caffeine per day. However, the authors noted that they could not control for other possible confounders, such as smoking and alcohol use. In a subsequent review, Signorello and McLaughlin indicated that most of the studies were biased, and concluded that evidence for a causal link between caffeine intake and spontaneous abortion remains inconclusive. However, Weng and others, in a prospective study of over 1,000 pregnant women, reported that caffeine intake, particularly more than 200 milligrams daily, increased the risk of miscarriage. Women who consumed no caffeine were at the lowest risk for miscarriage. Conversely, Savitz and others studied over 2,400 women over the course of their pregnancy, and found little indication of possible harmful effects of caffeine on miscarriage risk within the range of coffee and caffeine consumption reported. However, Savitz noted the subjects in their study were relatively light coffee drinkers, with the heaviest drinkers consuming about two cups daily. Large doses of caffeine administered to animals have caused birth defects. However, in a systematic review of studies evaluating the relationship between caffeine consumption and birth

defects, Browne indicated that there is no evidence to support a teratogenic effect of caffeine in humans. On the other hand, Schardt postulates that the data are not strong enough to say there is absolutely no increase in risk. The Food and Drug Administration and the American Dietetic Association recommend that pregnant women consider abstaining from caffeine use, or if they do drink caffeine beverages to do so in moderation. In its recent report, the Consumers Union recommended they drink no more than two cups of coffee a day to avoid the possible risk of miscarriage. Drinking caffeine beverages when breast feeding may make the child jittery as caffeine gets into breast milk. Weight Control Caffeine use may stimulate metabolism, increasing the resting metabolic rate about 10 percent for several hours, an effect which theoretically could facilitate weight loss. Greenway notes that caffeine has a long history of safe, nonprescription use as a weight-loss supplement, and that the benefits of treating obesity appear to outweigh the small associated risk. In a recent metabolic ward study, Rudelle and others reported that a beverage containing caffeine, green tea catechins, and calcium increased 24-hour energy expenditure by 4.6 percent, but the contribution of the individual ingredients cannot be distinguished. Although the increase in energy expenditure was modest, they indicated such modifications are sufficient to prevent weight gain and concluded such a beverage may provide benefits for weight control. Lopez-Garcia and others studied the effect of caffeine intake over the course of 12 years and its effect on body weight in men and women. They found that increased caffeine consumption was associated with decreased weight gain, but the differences were very small, being less than one pound difference. Regular consumption of coffee or caffeine would appear to make a very minor contribution to weight control as contrasted to proper diet and exercise. Excessive amounts may cause adverse effects in some individuals, especially when combined with ephedrine as discussed in the following text. Proper weight-control procedures are discussed in chapters 10 and 11. Sleeplessness Caffeine use, particularly before retiring for the night, may delay the onset of sleep because of its stimulant effects. This may be helpful in some situations. For example, decreased drowsiness and increased alertness may contribute to safer automobile operation under certain conditions. Philip and others found that drinking coffee with about 200 milligrams of caffeine helped improve the quality of nighttime driving. Horne and Reyner reported coffee intake is one of the few techniques useful to prevent vehicle accidents related to sleepiness. Gastric Distress Some individuals experience stomach irritation due to increased secretion of gastric acids following ingestion of caffeinated beverages. In such cases, individuals should consult their physician or avoid caffeine. Caffeine Naivete Abstainers or those who consume little caffeine may experience nervousness, irritability, headaches, or insomnia with moderate doses, although long-term consumption www.mhhe.com/williams9

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of coffee leads to development of tolerance and reduction of these “coffee nerves” symptoms. Youngstedt and others recently reported that moderate aerobic exercise may reduce the anxiety sometimes associated with caffeine intake. Caffeine Dependence In a recent cover story for National Geographic, coffee was labeled as the world’s most popular psychoactive drug—buzzing our brains, fraying our nerves, and robbing our sleep. Yet we simply refuse to survive without it. Although not classified as an addictive drug, some individuals may develop caffeine dependence, often referred to as caffeinism; caffeine dependence is listed in the Diagnostic and Statistical Manual of Mental Disorders published by the American Psychiatric Association. Juliano and Griffiths noted that caffeine-dependent individuals may experience various symptoms upon caffeine withdrawal, including headaches and nervousness, fatigue or drowsiness, depression, irritability, and difficulty concentrating. However, caffeine dependence is not considered a serious form of drug abuse. Mortality In their recent study of health professionals spanning about 20 years, Lopez-Garcia and others reported that regular coffee consumption was not associated with increased mortality rate in either men or women. However, Kerrigan and Lindsey indicated that in large doses, caffeine can be profoundly toxic, resulting in arrhythmia, tachycardia, vomiting, convulsions, coma, and death. Although rare, death may result from caffeine abuse, usually from overdoses of caffeine-containing diet or stimulant pills. Fatal caffeine overdoses in adults are typically in excess of 5g. Individuals who take several different over-the-counter dietary supplements may be taking substantial amounts of caffeine along with other drugs. Such combinations, in excess, may be fatal. Summary In general, most professional health organizations note that caffeine is regarded to be a safe drug. If you are healthy and are not on medications, several cups of coffee or caffeinated beverages should pose no health problems. Where moderation is recommended, the dosage is the equivalent of about 200 to 300 milligrams of caffeine per day, or about 2 cups of coffee. And we are talking 6-ounce cups of coffee or so, not the supersize 20-ounce cups or higher from local convenience stores. Women who are pregnant may want to consider abstention, similar to the recommendations for alcohol intake during pregnancy.

Ke y C o n c e p t s 䉴 Caffeine is a stimulant drug and can affect a variety of metabolic

and psychological processes in the body that may impact exercise performance and health. 䉴 Research suggests that caffeine may improve performance in a variety of athletic endeavors, particularly prolonged aerobic endurance exercise. An effective dose is approximately 5 milligrams per kilogram body weight. 䉴 In general, caffeine is regarded to be a safe drug, but physicians may recommend abstinence or use in moderation for some individuals.Various health professionals define moderation as the daily caffeine equivalent of 1–2 cups of coffee.

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C h e c k f o r Yo u r s e l f Procure an automatic blood pressure monitor, or have a colleague record your blood pressure. While resting, record your blood pressure several times over a course of 15–20 minutes. Drink a cup of coffee or two, and then record your blood pressure again, about every 15 minutes over the course of an hour, again while resting. Plot the results. Does caffeine affect your blood pressure?

Ephedra (ephedrine): Ergogenic Effects and Health Implications What is ephedra (ephedrine)? Ephedra sinica, a plant most commonly referred to as ephedra, contains a variety of naturally occurring alkaloids, including ephedrine and pseudoephedrine. The Chinese version of ephedra is known as ma huang (see figure 13.6). Ephedrine is considered the most active alkaloid, and its synthetic version is ephedrine hydrochloride. Pure ephedrine is regulated as a drug, and the FDA allows only very small amounts in over-the-counter drugs such as cold medications. Like caffeine, ephedrine is a stimulant and because it is derived from the plant ma huang, in the United States it had been classified as a dietary supplement. Ephedra or ephedrine-containing dietary supplements were marketed to promote weight loss, increase energy, and enhance sports performance, with such names as Xtream Lean and Ripped Force. These products were popular with some athletes. For example, Bents and Marsh found that almost half of the ice hockey players in one collegiate conference reported having used ephedra at least once in attempts to improve athletic performance. In 2004, the FDA prohibited the sale of ephedra or ephedrinecontaining dietary supplements, mainly because such products may pose some serious health threats, as noted later. Although such products have been banned, some ephedra-containing supplements are still marketed on the Internet. Ephedra-free products are also marketed to physically active individuals, but they contain other stimulants, such as caffeine and synephrine (discussed later).

Does ephedrine enhance exercise performance? In general, although a powerful stimulant, ephedrine by itself has not been shown to consistently enhance exercise performance. In their review, Rawson and Clarkson concluded that although there are few studies of the efficacy of ephedrine in improving exercise performance, these studies are consistent in their findings of no ergogenic effects. Shekelle and others, in a metaanalysis, supported this viewpoint, as did Magkos and Kavouras in their review, indicating that ephedrine and related alkaloids have not been shown, as yet, to result in any significant perfor-

(3.2-kilometer run wearing combat gear weighing about 11 kilograms), and a 10-kilometer run wearing similar gear. In their recent review, Magkos and Kavouras indicated that caffeineephedrine combinations have been reported in several instances to confer a greater ergogenic benefit than either drug by itself. Research appears to support an ergogenic effect of caffeine/ ephedrine supplementation in a number of studies, several involving exercise tasks of a military nature that may be applicable to enhancement of sports performance. Permissibility in sports Use of ephedrine, ephedra, and ma huang in competition is prohibited by WADA and the IOC. However, pseudoephedrine, like caffeine, has been removed from the WADA doping list and is now in the monitoring program. As ephedra is banned in competition only, athletes may use it in training. Magkos and Kavouras suggested that caffeine-ephedra mixtures may become one of the most popular ergogenic aids that athletes use in training.

Do dietary supplements containing ephedra pose any health risks? Seeds of Ephedra sinica, or ma huang.The seeds may be processed into tablets for sale as a dietary supplement. FIGURE 13.6

mance improvements. However, subsequent research has supported an ergogenic effect of ephedrine. Jacobs and others reported that the acute ingestion of caffeine and ephedrine, as well as ephedrine alone, increases local muscular endurance during the first set of traditional resistance-training exercise; however, the performance enhancement was attributed primarily to the effects of ephedrine as there was no additive effect of caffeine. Herbal pseudoephedrine may be found in some dietary supplements, but is most commonly found in over-the-counter cold medications. Little research has been conducted with pseudoephedrine and exercise performance. However, Hodges and others, in a recent well-controlled, double-blind, placebo, crossover study with seven male athletes, reported that pseudoephedrine (2.5 mg/kg body weight) taken 90 minutes prior to a 1,500-meter run improved performance by 2.1 percent, or about 6 seconds. There were no changes in measured blood parameters, so they assumed it was a central effect. Ephedrine with caffeine Graham indicated that the combination of ephedrine with caffeine has been suggested to be more potent than caffeine alone. Several recent studies by Bell and associates, working with Ira Jacobs at the Defence and Civil Institute of Environmental Medicine in Canada, have shown that caffeine/ ephedrine combinations may enhance exercise performance in various exercise performance tasks, many of a military nature. Using pharmaceutical-grade caffeine and ephedrine doses approximating 4–5 mg/kg and 0.8–1.0 kg, respectively, they reported significant improvements in exercise tasks such as a 30-second Wingate test of anaerobic capacity, a maximal cycle ergometer performance about 12.5 minutes in duration, the Canadian Forces Warrior Test

Of all dietary supplements, the Consumers Union noted that the herbal supplement ephedra may be the most hazardous. Bent and others noted that ephedra use is associated with a greatly increased risk for adverse reactions compared with other herbs; they indicated that ephedra products accounted for 64 percent of all adverse reactions to herbs in the United States even though these products represented less than 1 percent of herbal product sales. Use of ephedra has been associated with numerous health problems. Maglione and others reported adverse psychiatric effects of ephedra use, including psychosis, severe depression, mania or agitation, hallucinations, sleep disturbance, and suicidal ideation. Haller and others implicated ephedra with seizures. Naik and Freudenberger indicated ephedra was associated with heart arrhythmias, myocardial infarction, cardiac arrest, and even sudden death. Haller and others reported that although ephedra alone may be dangerous, ephedra combined with caffeine exaggerates the potential adverse risks. The Ephedra Education Council notes that 100 milligrams of ephedrine per day is safe, and may be useful for individuals on a weight-loss program mainly by increasing the resting metabolic rate. However, this dose may cause problems in individuals with existing disease, such as high blood pressure or heart disease, who are attempting to lose weight. Moreover, some individuals may exceed the recommended dosage. Indeed, Haller and Benowitz noted that ephedrine misuse may be associated with significant health risks. In recent years, the deaths of several prominent collegiate and professional athletes made headlines when it was discovered they were using ephedra-containing supplements during training under warm environmental conditions. Ephedrine may increase the risk of heat stroke. The risk-taking behavior associated with sports participants is well known, so athletes taking more than the recommended dose is one of the major problems. Additionally, the purity and amount of ephedra in a product are not well controlled. Given these possibilities, and given its physiological effects, ephedrine could be involved in such tragedies. www.mhhe.com/williams9

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䉴 Use of ephedra or ephedra-containing supplements has been

associated with serious health problems, including psychiatric disorders, increased cardiovascular risk factors, and heat stroke in athletes that could be fatal.

C h e c k f o r Yo u r s e l f Visit a local health food store that primarily sells dietary supplements, including sports supplements. Ask the clerk to show you products containing ephedra or ephedrine for weight loss and enhanced sport performance, and also ask if there are any health risks related to their use. Record the response for class discussion.

F I G U R E 1 3 . 7 Ephedra-free dietary supplements are marketed for weight loss; many contain synephrine, a compound similar to ephedrine (see text for discussion).

Synephrine Ephedra-free dietary supplements have recently been marketed for weight loss (see figure 13.7). These products may contain synephrine, along with other stimulants such as caffeine. Synephrine is an extract from the Seville orange, or bitter, or sour orange. Neo-synephrine is also known as phenylephrine. Synephrine is a dietary supplement in the United States, but classified as a drug in Europe. Synephrine is structurally similar to ephedrine, and has been marketed as a safe alternative to ephedra. There is little evidence to support weight loss with synephrine. Bent and others reported that synephrine was of no statistically significant benefit for weight loss. Greenway and others, in two studies, also found that phenylephrine is not efficacious for weight loss. The Consumers Union also indicates there is little evidence synephrine is safe, and experts suspect it could cause the same kinds of problems that ephedra does, particularly when it is combined with caffeine. For example, Bui and others found that supplementation with a synephrine dietary supplement (900 milligrams standardized to 6 percent synephrine) increased both systolic and diastolic blood pressure for 5 hours after taken. Such supplements may increase risks for individuals with hypertension. Bouchard and others reported a case study indicating that synephrine may be associated with ischemic stroke. For individuals interested in weight loss, safer approaches are available, as detailed in chapter 11.

Sodium Bicarbonate: Ergogenic Effects, Safety, and Legality What is sodium bicarbonate? Sodium bicarbonate is an alkaline salt found naturally in the human body. It is the major component of the alkaline reserve in the blood, whose major function is to help control excess acidity by buffering acids. Thus, sodium bicarbonate is also known as a buffer salt. Its action is comparable to that of medications you may take to control an upset stomach caused by gastric acidity. Sodium bicarbonate may be purchased in a supermarket as baking soda (see figure 13.8), and it also has been marketed to athletes as part of a sports supplement.

Does sodium bicarbonate, or soda loading, enhance physical performance? During high-intensity anaerobic exercise, sodium bicarbonate helps buffer the lactic acid that is produced when the lactic acid

Ke y C o n c e p t s 䉴 Ephedra, or ma huang, although classified as a dietary supplement,

contains a potent stimulant drug, ephedrine. 䉴 In general, research suggests that ephedra or ephedrine supple-

mentation does not enhance exercise or sport performance. However, supplementation with caffeine/ephedrine compounds has been shown to enhance performance in various exercise tasks.

FIGURE 13.8

bicarbonate. 544

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Baking soda is a commercial version of sodium

energy system is utilized. You may recall from chapter 3 that the accumulation of excess hydrogen ions from lactic acid in the muscle cell may interfere with the optimal functioning of various enzymes and thus lead to fatigue. The natural supply of sodium bicarbonate that you have in your blood can help delay the onset of fatigue during anaerobic exercise. It may facilitate the removal of the hydrogen ions associated with lactic acid from the muscle cell, thereby mitigating the adverse effects of the increased acidity (see figure 13.9). However, fatigue is inevitable if the rate of lactic acid production exceeds the capacity of your sodium bicarbonate supply to buffer it. Theoretically, an increase in the alkaline reserve could delay the onset of fatigue. Alkaline salt supplementation has been studied for its ergogenic potential on all three human energy systems, but mainly the lactic acid energy system. Most studies have used a doubleblind placebo design in which all subjects took all treatments. In the popular literature, sodium bicarbonate supplementation has been referred to as soda loading, from baking soda, or buffer boosting, for increasing the natural blood buffer content. Lactic Acid Energy System Over a half-century ago, German scientists reported that the ingestion of sodium bicarbonate and other alkaline salts could help improve anaerobic work capacity. Since then, many studies have failed to support this finding, but now a substantial number of well-controlled experiments by highly respected investigators in sport nutrition research have provided supportive data. The usual experimental protocol has been to have subjects, about 1–3 hours before the exercise task, ingest a dosage of 0.15–0.30 grams of sodium bicarbonate per kilogram body weight. Recent research by McNaughton has indicated 0.30 grams per kilogram body weight appears to be the optimum dose, with higher dosages providing no additional benefits. This amount totals less than 1 ounce for the average adult. Some studies have used sodium citrate in similar dosages, because it has been shown to increase the alkaline reserve. The exercise task selected was normally one that stressed the lactic acid energy system, or about 1–3 minutes of maximal exercise. Often these exercise tasks were classified as supramaximal, because they used workloads greater than 100 per-

Muscle cell ATP Glycogen

Blood vessel

Lactic acid

(H+)

Sodium bicarbonate

F I G U R E 1 3 . 9 Alkaline salts, such as sodium bicarbonate, are theorized to reduce the acidity in the muscle cell by facilitating the efflux of hydrogen ions from the cell interior, promoting a more homeostatic environment for continued muscle contraction.

cent VO2 max. Repeated bouts of intense exercise interspersed with short rest periods have also been used, such as five 100-yard swims with a 2-minute rest between each. A recent study by Raymer and others, using magnetic resonance spectroscopy, provided support for the main theory underlying the ergogenic efficacy of sodium bicarbonate supplementation. They reported that sodium bicarbonate ingestion delayed the onset of intracellular acidification during incremental exercise, which would help maintain a more homeostatic cellular environment to delay the onset of fatigue. Based on the available scientific evidence, sodium bicarbonate supplementation does appear to enhance performance in exercise tasks dependent upon the lactic acid energy system (see figure 13.10). A consistent finding is an increased serum pH following sodium bicarbonate supplementation, the desired effect to induce buffering of lactic acid. Regarding other factors that have been investigated, approximately half of the well-controlled laboratory studies suggest that ingestion of sodium bicarbonate will reduce acidosis in the muscle cell, decrease the psychological sensation of fatigue at a standardized level of exercise, and increase performance in high-intensity anaerobic exercise tasks to exhaustion. Most studies provided the alkaline salt supplement an hour or more prior to exercise testing, but McNaughton and others have recently shown that chronic bicarbonate ingestion for a period of 5 days also provided ergogenic benefits on 60-second highintensity exercise performance. Douroudos and others also reported significant improvements in anaerobic Wingate test performance following 5 days of sodium bicarbonate supplementation. Sodium bicarbonate supplementation may also be beneficial during more prolonged exercise training. Edge and others trained recreationally active women three times weekly over the course of 8 weeks. Each day the women completed twelve 2-minute high-intensity cycle intervals after consuming either a sodium bicarbonate supplement or placebo. Although both groups increased their muscle buffer capacity through training, the sodium bicarbonate group experienced greater improvements in lactate threshold and time to fatigue at 100 percent VO2 max. Various field studies have reported significant improvements in events that primarily use the lactic acid energy system, such as 400 or 800 meters in highly trained track athletes, 100-meter swims in experienced swimmers, and 5-kilometer bicycle races in trained cyclists. In support of these field studies showing improved performance following sodium bicarbonate supplementation, a recent laboratory study by Van Montfoort and others, comparing different sodium mixtures, reported that sodium bicarbonate improved run time to exhaustion in a test designed to evaluate the lactic acid energy system; the run to exhaustion approximated 77–82 seconds. Artioli and others reported a potential benefit of sodium bicarbonate supplementation in another sport that may depend on anaerobic energy production. They reported that a standard bicarbonate-loading protocol (0.3 grams/kg 2 hours before testing) significantly improved performance in the latter phases of both a specific judo test and a Wingate test for anaerobic capacity of the upper arms. www.mhhe.com/williams9

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sodium bicarbonate enhanced performance, and in studies that measured exercise time to exhaustion, there was a mean improvement of 27 percent. The majority of the studies conducted subsequent to these reviews have indicated sodium bicarbonate or sodium citrate supplementation was an effective ergogenic aid.

F I G U R E 1 3 . 1 0 Sodium bicarbonate may enhance sports performance in a variety of events dependent primarily upon the lactic acid energy system (anaerobic glycolysis), such as the 400-meter sprint in track.

However, as with most research with nutritional ergogenic aids, not all studies find positive effects. For example, Kozak-Collins and her associates recently reported that sodium bicarbonate supplementation taken at moderate altitude did not improve the performance of competitive female cyclists on repeated 1-minute interval cycle tasks at 95 percent VO2 max, nor did van Someren and others find any benefits on repeated 45-second high-intensity cycling bouts. Using well-trained wrestlers as subjects, Aschenbach and others reported no ergogenic effect of sodium bicarbonate during high-intensity arm ergometry involving eight 15-second maximal effort intervals with 20 seconds recovery. Portington and others also reported no effects of sodium bicarbonate supplementation on 5 maximal sets of leg press repetitions, but indicated the exercise intensity may have been lower compared to studies that have shown ergogenic effects. It should also be noted that although performance was not improved in these studies, neither was it impaired. Several reviews by Matson and Tran, Requena, and most recently McNaughton and others, have all concluded that sodium bicarbonate is an effective ergogenic aid in events that may depend primarily on the lactic acid energy system. Matson and Tran provided the most convincing analysis, using the meta-analytic technique to statistically compare the effects reported in twentynine of the best studies. In general, they noted that the ingestion of 546

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ATP-PCr Energy System Based on the available scientific data, alkaline salt supplementation does not appear to be an effective ergogenic aid for exercise tasks dependent primarily upon the ATP-PCr energy system, since most studies have reported no beneficial effects on performance in exercise bouts lasting less than 30 seconds or in resistive exercise tasks stressing strength, power, or short-term local muscle endurance. For example, McNaughton and Cedaro reported no ergogenic effect on maximal cycle ergometer performance in either 10-second or 30-second trials. This lack of an ergogenic effect is most likely because such exercise tasks do not maximally stress the normal alkaline reserve. However, Price and others reported that ingestion of sodium bicarbonate improved performance in multiple, intermittent 14-second maximal sprints (one sprint every 3 minutes) during a 30-minute cycle ergometer trial. Moreover, Bishop and Claudius reported that sodium bicarbonate ingestion can improve intermittent-sprint performance. The test protocol involved two 36-minute halves with prints interspersed with lesser intensity exercise tasks, and the investigators suggested sodium bicarbonate may be a useful supplement for team-sport athletes. Performance in these multiple sprints may have been somewhat dependent on the lactic acid energy system. Oxygen Energy System Although sodium bicarbonate has been studied mainly for its buffering effects, the sodium content could theoretically expand blood volume and benefit aerobic endurance performance, as suggested in chapter 9. The effect of alkaline salt supplementation on performance in events that depend increasingly on the oxygen energy system, such as events approximating 4 minutes or more in duration, are equivocal. Several studies have shown ergogenic effects. McNaughton and Cedaro reported an increased cycle ergometer work output in a 4-minute trial, as did Linossier and others in an exhausting exercise task at 120 percent of VO2 peak lasting 4–5 minutes. Bird and others found that sodium bicarbonate supplementation improved 1,500-meter run performance while Shave and others found that sodium citrate, as compared to a sodium chloride placebo, improved performance in a 3,000-meter run by almost 11 seconds. Using well-trained male college runners as subjects, Oopik and others found that sodium citrate supplementation improved performance in a simulated 5-kilometer treadmill run by 30 seconds. Although primarily aerobic in nature, such exercise tasks may still depend somewhat on the lactic acid energy system. However, several studies have shown ergogenic effects of alkaline salt supplementation on exercise tasks that depend primarily on oxidative metabolism. Potteiger and others reported that sodium citrate supplementation significantly improved performance by 1.7 minutes in 30-kilometer cycling performance, and McNaughton and others reported that sodium bicarbonate supplementation, compared to

the placebo trial, produced a 13 percent improvement in maximal cycle ergometer work over 60 minutes. Conversely, other studies report no ergogenic effect of alkaline salt supplementation. Potteiger and others reported no beneficial effect of sodium bicarbonate supplementation to male runners on performance in a run to exhaustion at 110 percent of the lactate threshold following 30 minutes of running at the lactate threshold. Stephens and others reported that although sodium bicarbonate supplementation induced a small muscle alkalosis, there was no effect on exercise performance. The exercise task consisted of cycling at 77 percent VO2 max for 30 minutes, and then completing a set workload as fast as possible, which took about another 30 minutes. In a well-designed crossover study involving endurance-trained cyclists using their own bikes, Schabort and others also found no effect of varying doses of sodium citrate (0.2, 0.4, and 0.6 g/kg) on cycling endurance. The laboratory cycling protocol was designed to compare with an actual 40-kilometer road race, with 10 sets of sprints within the 40-kilometer distance. Although the sodium citrate produced dose-dependent changes in blood alkalinity, there was no significant effect on total 40-kilometer time nor on the various sprint performance times. Other studies have shown no ergogenic effects on 1,500-meter run performance. Additional research is needed to clarify this equivocality. Stephens and others indicated that sodium bicarbonate ingestion has been shown to increase both muscle glycogenolysis and glycolysis during brief submaximal exercise, which could be detrimental to performance during more prolonged, exhaustive exercise. However, no studies have evaluated this potential ergolytic effect.

Is sodium bicarbonate supplementation safe and legal? The dosage of sodium bicarbonate used in most of these studies, about 300 milligrams per kilogram body weight, appears to be effective yet medically safe. Relative to possible disadvantages, several investigators have noted that some subjects developed gastrointestinal distress, including nausea and diarrhea. Shave and others noted a high potential for gastrointestinal distress in their study that used 0.5 grams of sodium citrate per kilogram body weight, and suggested that this may limit the use of this strategy by athletes in competition. Excessive doses could lead to alkalosis, with symptoms of apathy, irritability, and possible muscle spasms. Given the potential gastrointestinal distress often associated with an acute high dose of sodium bicarbonate, research by McNaughton and Thompson suggests that a chronic loading protocol, or taking the same total amount of sodium bicarbonate spread over a 6-day period, may be just as effective. Use of sodium bicarbonate currently is not prohibited by WADA. As noted, sodium bicarbonate (baking soda) use by athletes has been dubbed soda loading, possibly to liken it to carbohydrate loading. As you may recall, the purpose of carbohydrate loading is to increase the storage of muscle and liver glycogen as a means to prevent fatigue in prolonged endurance events. Soda loading is viewed by some in a similar context, an attempt to

increase the supply of a natural body ingredient helpful as a means to delay fatigue. However, because sodium bicarbonate may be regarded as a drug, it remains to be seen whether this technique will be deemed illegal. Tim Noakes, in the recent edition of his classic text Lore of Running, indicated that the use of sodium bicarbonate may be prohibited by the International Olympic Committee in the near future. Currently there is no test to detect its use, except for urinary pH, which can also be affected by some antacids, and at present sodium bicarbonate is considered to be legal for use in sports.

Ke y C o n c e p t s 䉴 Sodium bicarbonate supplementation appears to be an effective

ergogenic aid in exercise tasks that depend primarily upon the lactic acid energy system (anaerobic glycolysis), such as a 400-meter dash in track. 䉴 Ingestion of sodium bicarbonate is generally regarded as safe, but may cause acute gastrointestinal distress and diarrhea. Supplementation over a longer time frame may be effective and less likely to cause intestinal problems.

Anabolic Hormones and Dietary Supplements: Ergogenic Effects and Health Implications Several hormones in the body may exert significant anabolic effects on body composition by stimulating protein synthesis, particularly human growth hormone (HGH), insulin, insulin-like growth factors (IGF-1), and testosterone. As noted in previous chapters, several nutrient supplements, such as specific amino acids, have been utilized in attempts to increase the secretion of these hormones for anabolic purposes. Two of these hormones, HGH and testosterone, as well as drugs patterned after testosterone, have been used directly to increase muscle mass. Additionally, several prohormones that may be converted into testosterone have been marketed as dietary supplements and some herbal supplements are marketed for their potential to stimulate testosterone production. It should be noted that WADA prohibits the use of the anabolic hormones discussed in this section, including human growth hormone, anabolic/androgenic steroids, and anabolic prohormone dietary supplements.

Is human growth hormone (HGH) an effective, safe, and legal ergogenic aid? HGH is a natural hormone secreted by the anterior pituitary gland in the brain; HGH is an anabolic hormone that stimulates bone growth and the development of muscle tissue through its effects on protein, carbohydrate, and fat metabolism. A detailed discussion of the role of HGH is beyond the scope of this text. It is important to note, however, that extensive research into its effects began only when genetically engineered versions (recombinant www.mhhe.com/williams9

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HGH, or rHGH) of the natural body hormone became available in the early 1990s. rHGH injections are therapeutic for individuals with impaired HGH pituitary production or secretion. Available data suggest that in elderly men, who normally have reduced levels of HGH, injections of the hormone modify body composition, decreasing body fat and increasing lean body mass. In their review, Liu and others evaluated 31 studies with HGH supplementation, two weeks or more, to healthy but overweight elderly individuals, and found that it is associated with small changes in body composition with losses of body fat and increases in lean body mass. However, in a recent prospective 10-year study, Götherström and others also reported a reduction in total body fat with HGH supplementation early in the study, but the effect was transient, which they suggested could be due to the normal aging of the individuals. In general, the available research does not support an anabolic or ergogenic effect of rHGH supplementation in younger individuals. For example,Yarasheski and others studied the effect of rHGH versus a placebo on adult males who weight-trained for 12 weeks. They reported significant increases in lean body mass in the group receiving rHGH, but there were no significant increases in skeletal muscle protein synthesis and size, as measured by magnetic resonance imaging, or in muscular strength, over the effects produced by weight training alone in the placebo group. They suggested that rHGH may influence the development of other tissues. More recently, Taaffe and others reported no significant increase in muscle fiber size, as determined by muscle biopsy, following 10 weeks of resistance training and rHGH injections. Several other wellcontrolled studies reported similar findings with rHGH supplementation to experienced resistance-trained athletes. In her review, Anne Loucks concluded that supraphysiological doses of rHGH have only increased total body water, lean body mass, and whole-body protein synthesis in general without specifically increasing skeletal muscle protein synthesis or skeletal muscle mass, strength, or power in untrained young men or experienced young weight lifters. Healy and others recently reported that HGH injections exerted an anabolic effect during rest and exercise and increased whole body protein in endurance-trained athletes, but whether the increase was muscle mass was not determined. Nevertheless, these investigators indicated that short-term administration of HGH may have short-term benefits for physical performance. Limited research is available relative to the effects of rHGH on endurance exercise performance, but Hansen and others noted that although rHGH increases lipolysis and the availability of fatty acids at rest, there is no increased fat oxidation during exercise as measured by indirect calorimetry. This finding suggests no potential metabolic advantages of rHGH supplementation during aerobic endurance exercise. The interested reader is referred to the recent review by Dean, who noted that there is no evidence of increased muscle strength with HGH use in trained athletes. The reader is referred also to recent reviews by Kraemer and others, Frisch, Zachwieja and Yarasheski, and Saugy and others. In a recent baseball scandal in the United States, some professional athletes admitted using rHGH to train harder and recover 548

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more rapidly, and anecdotal reports suggest that it may work for these intended purposes. However, at present, there are no good scientific data to support an ergogenic effect of rHGH on muscle size, strength, or power beyond the effect generated by a proper weight-training program. The potential adverse health effects of rHGH are substantial, including insulin resistance, high blood pressure, and increased risk of congestive heart failure. Liu and others indicated that because rHGH therapy is associated with increased rates of adverse events, it cannot be recommended as an antiaging therapy. Tentori and Graziani suggest growth hormone or its mediator, IGF-1, have been associated with colon, breast, and prostate cancers. Most researchers caution that other long-term health risks of HGH administration, either as rHGH or produced by amino acid supplementation, are unknown. This is particularly distressing as one report indicated approximately 5 percent of high school students have used HGH. Use of rHGH is prohibited by WADA. Although Saugy and others noted that detection of HGH is difficult due to its rapid half-life, WADA did have an effective test for detecting use of rHGH in the 2008 Beijing Olympics. Some dietary supplements are marketed as HGH products, such as HGH SurgeTM, but they contain only nutrients, such as amino acids and chromium, that are theorized to be ergogenic. However, as noted in previous chapters, such nutrients have not been shown to have anabolic effects and some may be contaminated with illegal drugs that may lead to a positive doping test.

Are testosterone and anabolic/androgenic steroids (AAS) effective, safe, and legal ergogenic aids? Testosterone, the male steroid sex hormone produced by the testes, was one of the first anabolic agents used in attempts to enhance physical performance, possibly as early as the 1936 Berlin Olympic Games. As documented in the study by Bhasin and the review by Evans, testosterone is a very effective ergogenic aid, increasing lean muscle mass, decreasing body fat, and increasing strength even without resistance training; these anabolic effects were augmented in subjects who also trained. Rogerson and others recently reported that testosterone injection once per week to resistance-trained individuals increased muscular strength and 10-second cycle sprint performance in 3–6 weeks. Testosterone must be injected because ingested testosterone will be catabolized by digestive enzymes. Although injected testosterone use is still prevalent among various athletic groups, oral drug forms of testosterone have been developed, as noted here. Anabolic/androgenic steroids (AAS) represent a class of synthetic drugs designed to mimic the effects of testosterone. The chemical structure of testosterone may be modified in attempts to maximize the anabolic muscle-building effects and minimize the androgenic male secondary sex characteristics; both oral and injectable AAS have been developed. In the United States, AAS are classified as Schedule III drugs under the Controlled Substances Act, and may be used medically for several conditions, such as treatment of anemia, osteoporosis,

and gonadal dysfunction. Earlier research suggested that AAS may be useful in older males by helping to prevent sarcopenia (loss of muscle) with the aging process, but Liu and others indicate AAS supplementation is not recommended because of potential health problems, as noted in the following text. AAS are the drugs of choice for many strength athletes and bodybuilders to improve performance and appearance. AAS have been used by professional athletes for years, as documented in the revealing book, Wild Times, Rampant ’Roids, Smash Hits, and How Baseball Got Big written by a former professional baseball player. At the time of this writing, Congress and the FBI are investigating anabolic steroid use among prominent baseball players. Bahrke and others noted that recent surveys indicate the use of AAS is also prevalent among adolescent athletes, particularly boys in strength-related sports. Their use is even common among young male nonathletes, and increasing numbers of teen-age girls, according to Yesalis and others, who desire to increase muscle mass for an enhanced self-image. Faigenbaum and others recently reported AAS use in middle-school students, ages 9–13, with the belief that they improved sports performance and physical appearance. In general, surveys have indicated that approximately 4–6 percent of boys and 1–2 percent of girls have used AAS. Although resistance training does not cause drug use, DuRant and others recently noted that adolescent AAS users in the United States, both athletes and nonathletes, are more likely to engage in strength training. AAS use is also associated with use of other recreational drugs. Thus, young adolescent athletes and nonathletes engaged in strength training should be educated about the health risks associated with AAS use. The effects of AAS on body composition and strength have been studied rather extensively, and although there may be some flaws in the experimental designs used, most reviewers agree that AAS use may increase muscle mass and strength and decrease total body fat, a judgment supported by recent reviews of laboratory studies that included meta-analysis as part of the evaluative criteria. Schroeder and others found that AAS supplementation was also effective with healthy older men, significantly increasing muscle mass and strength after only 6 weeks. The increased muscle mass may be attributed to hypertrophy and the formation of new muscle fibers, in which key roles are played by the androgen receptors, as depicted in figure 13.11. Baume and others note that although AAS are used mainly by strength athletes, endurance athletes have also used AAS because they are theorized to facilitate a better recovery and thus permit a higher training load. However, they found that compared to a placebo, two different anabolic steroids administered 12 times during a month of hard endurance training had no effect on standardized treadmill running performance test or blood markers for recovery from exercise. Research with AAS and endurance performance is limited, but that which is available does not support an ergogenic effect. AAS use has been associated with a number of medical problems, as documented in recent reviews by Hartgens and Kuipers, Talih and others, and Yesalis and Bahrke. Some are relatively minor such as acne and loss of hair. AAS may also adversely

Steroid

Amino acids DNA RNA Muscle cell receptor

Contractile muscle protein

Ribosome

F I G U R E 1 3 . 1 1 Anabolic steroids picked up by androgen in the cell nucleus initiate the process of protein formation in cells such as muscle fibers, leading to muscle hypertrophy.

affect psychological processes, leading to increased aggression, hostility, depression, and possible suicide attempts, and an increased tendency to commit violent crimes, including homicide. Continued use may predispose adults to coronary heart disease by inducing structural changes in the heart-muscle, decreasing HDL-cholesterol, and increasing blood pressure as documented in both epidemiological and experimental studies, and recently reviewed by Nnakwe. Prolonged steroid use may possibly lead to impaired development of tendons, decreasing their strength and contributing to a potential for rupture. Prolonged use has resulted in severe liver diseases, including cancer. Anabolic steroids may cause premature cessation of bone growth in children and adolescents and may result in the appearance of several male secondary sex characteristics in females, some of which may be irreversible, such as deepening of the voice. Table 13.4 highlights many of the health problems associated with abuse of AAS. However, many of the adverse health effects of AAS use appear to be reversible. For example, Hartgens and others found that bodybuilders who cycled off AAS steroids for 3 months had similar lipoprotein profiles and liver enzymes as their non-drug-using counterparts. Moreover, earlier reviews noted that although the short-term health effects of AAS have been increasingly studied and reviewed, and while AAS use has been associated with adverse and even fatal effects, the incidence of serious effects thus far reported has been extremely low. However, subsequent to these reviews, Urhausen and others reported that several years after discontinuation of anabolic steroid abuse, strength athletes (bodybuilders and powerlifters) who used AAS showed a slight concentric left ventricular hypertrophy in comparison with AAS-free strength athletes; left ventricular hypertrophy increases the risk of heart attack. Because of the potential health risks, one of the risk-reduction objectives in Healthy People 2010 is the reduction of AAS use among high school students. Moreover, the U.S. Congress has passed legislation to classify AAS as controlled substances, thus limiting their production and distribution by pharmaceutical companies. Penalties may be severe. According to Melnik and others, some AAS users obtain illegal prescriptions from physicians. However, many obtain these drugs illegally on the black market where quality is not controlled, and chemical analysis www.mhhe.com/williams9

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TABLE 13.4 Possible health risks associated with use

of anabolic/androgenic steroids (AAS) Cosmetic-related effects Facial and body acne Female-like breast enlargement in males (gynecomastia) Premature baldness Masculinization in females Facial and body hair growth in females Premature closure of growth centers in adolescents, leading to stunted growth Deepening of the voice in females Psychological effects Increased aggressiveness and possible violent behavior Reproductive effects Reduction of testicular size Reduction of sperm production Decreased libido Impotence in males Enlargement of the prostate gland Enlargement of the clitoris Cardiovascular risk factors and diseases Atherosclerotic serum lipid profile Decreased HDL-cholesterol Increased LDL-cholesterol High blood pressure Impaired glucose tolerance Increased size of left ventricle Stroke Heart disease Liver function Jaundice Peliosis hepatis (blood-filled cysts) Liver tumors Athletic injuries Tendon rupture

has revealed some potentially hazardous constituents in these “homemade” drugs. AAS users are known to use other illicit drugs as well, each carrying independent health risks. As is obvious, the use of testosterone or AAS for the purpose of gaining body weight and strength is not recommended. WADA prohibits the use of AAS in training and competition. The American College of Sports Medicine has developed a position statement on the use of anabolic steroids in sports. Although an extensive discussion of AAS is beyond the scope of this text, the ACSM report provides a detailed review for the interested reader, as does the most recent review by Yesalis and Bahrke. 550

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Are anabolic prohormone dietary supplements effective, safe, and legal ergogenic aids? Several dietary supplements marketed to athletes as potent anabolic agents are of special interest, particularly dehydroepiandrosterone (DHEA), androstenedione, and related compounds. These supplements are classified as prohormones because they are precursors for testosterone and are thus theorized to increase muscle mass and decrease body fat. They may be derived from certain plants, such as wild yams. Although these prohormones have been marketed as dietary supplements, in 2005 the FDA classified them as controlled drugs, similar to anabolic steroids. Dehydroepiandrosterone (DHEA) and its sulfated metabolite (DHEAS) are produced in the body by the adrenal and gonadal glands, and may be converted into androstenedione with subsequent conversion to testosterone in peripheral tissues, including fat and muscle tissue. Body levels of DHEA are high in young adulthood and gradually decrease to low levels with aging. Although Abbasi and others reported a low, but significant, inverse relationship between natural DHEA levels and body fat in men aged 60–80 years, there are no data supporting beneficial effects of DHEA supplementation. Using well-controlled experimental designs, recent studies by Wallace and Brown and their associates revealed no significant effects of DHEA supplementation (50–100 milligrams/day for 8–12 weeks) on serum testosterone levels, lean body mass, or muscular strength in either healthy middle-aged or young men involved in resistance training. In a more prolonged 2-year study, Nair and others reported no effect on body composition, physical performance, insulin sensitivity, or quality of life in elderly men and women who received DHEA supplementation. DHEA has also been marketed as an anti-aging agent to help prevent the development of chronic diseases, but in a recent review, Sirrs and Bebb indicated no good scientific data support this speculation. They caution against use of DHEA supplements as high serum DHEA levels have been associated with several health risks, including several forms of cancer. Nevertheless, a recent study by Villareal and others provided some preliminary data supporting positive effects of DHEA supplementation on bone mineral density, body fat, and lean body mass in elderly subjects with very low levels of natural DHEA. Genazzani and others also reported some potential health benefits for such individuals. Both research groups indicated that more defined and specific research is needed before DHEA supplementation may be recommended as a standard treatment. These data with elderly subjects with very low DHEA levels do not support DHEA supplementation to young or middle-aged individuals. For example, Conrad Earnest, an expert in anabolic dietary supplements, reported that DHEA supplementation at relatively low doses (50–150 milligrams) does not enhance serum testosterone in young men. Moreover, Acacio and others found that six months supplementation with DHEA to young men aged 18–42 elevated levels of a metabolite that raised concerns about the potential negative impact of DHEA supplementation on the prostate gland. The Consumers Union recently advised that indi-

viduals avoid DHEA supplementation as there is not enough evidence concerning its effectiveness or safety. Androstenedione and related compounds, such as androstenediol and norandrostenediol, are potent anabolic agents, one step removed from the formation of testosterone. Androstenedione received considerable notoriety during the 1998 baseball season when Mark McGwire, who established a home run record at that time, acknowledged using the dietary supplement. Subsequently, androstenedione-related products flooded the marketplace for resistance-trained individuals, even though no reputable research was available supporting beneficial effects. Based on previous research with testosterone, Leder and others suggest large doses of androstenedione may be ergogenic, particularly with individuals who take multiple doses daily. However, several subsequent studies have evaluated the ergogenic effects of androstenedione supplementation, and most have shown no beneficial effects. In a short-term study, Rasmussen and others found no effect of oral androstenedione supplementation (100 milligrams/ day for 5 days) on serum testosterone or muscle protein anabolism in young men. In a more prolonged study, Wallace and others reported no significant effects of androstenedione supplementation (100 milligrams/day for 12 weeks) on serum testosterone levels, lean body mass, or muscular strength in resistance-trained middle-aged men. Using three individual 100-milligram and rostenedione doses daily (total 300 milligrams/day), King and others reported no significant effects on serum testosterone, body fat, lean body mass, muscle fiber diameter, or muscular strength in young men during 8 weeks of resistance training. Other studies, using somewhat higher doses, reported positive findings. Leder and others, although finding no significant effects of a 100-milligram dose, reported significant increases in serum testosterone in adult men following a 300-milligram dose, but no exercise performance was measured. Earnest and others also reported significant, but small, increases in total testosterone with a 200-milligram dose of androstenedione, but not androstenediol, supplementation. In a study with young women, Brown and others reported that androstenedione intake (100 or 300 milligrams) significantly increased serum testosterone concentrations. Recent reviews do not support an ergogenic effect of androstenedione and its congeners. Earnest noted that even though increases in testosterone following androstenedione ingestion have been found to be statistically significant, they have not been accompanied by favorable changes in protein synthesis or metabolism, muscle mass or lean body mass, or strength. Brown and others also concluded that the use of prohormone nutritional supplements does not produce either anabolic or ergogenic effects in men. These findings have also been supported in reviews by Ziegenfuss and Maughan. Use of androstenedione and its congeners may be associated with increased health risks. Earnest indicated that androstenedione supplementation has been associated with impaired lipid metabolism, such as decreased HDL-cholesterol and increased LDL-cholesterol, which might increase risk for cardiovascular disease. Several studies have reported significant increases in estrogen hormones (estradiol or estrone), which could exert feminizing effects in males, such as gynecomastia (breast enlarge-

ment). Other adverse effects on gonadal hormones may be associated with testicular shrinkage and infertility. Leder also notes women and children who use such supplements may be at risk. Unfortunately, given the recency of such supplements, no longterm safety data are available. For athletes who may be tested for doping, the use of DHEA or androstenedione and related prohormones has been banned by WADA and the International Olympic Committee; their use has also been banned by other sports organizations, including the National Collegiate Athletic Association and the National Football League. Although anabolic metabolic prohormones are currently banned for sale in the United States, a number of substitutes for these products are being marketed on the Internet. For example, Testosterone FactorsTM is a blend of vitamins, amino acids, and herbal ingredients, none of which is banned. However, Maughan notes that some apparently legitimate dietary supplements on sale contain ingredients that are not declared on the label but that are prohibited by the doping regulations of the WADA and the International Olympic Committee. For example, Geyer and others secured 634 nutritional supplements from 13 countries, and 14.8 percent contained anabolic androgenic steroids not declared on the label. The administration of some of the supplements resulted in positive doping tests.

Ke y C o n c e p t s 䉴 The use of anabolic drugs or hormones to increase body weight

may be effective but may also lead to a variety of health problems. WADA prohibits the use of anabolic hormones in sports training or competition. 䉴 Research has shown that prohormone dietary supplements marketed as anabolic agents, such as androstenedione, do not effectively increase muscle mass or strength. Moreover, such prohormones have been classified as controlled anabolic steroids and their use is illegal and banned by WADA.

C h e c k f o r Yo u r s e l f Go to the Internet search engine www.google.com, type in anabolic steroids, and check the advertisements and information related to laws and use of such products. Share the information with your classmates. Now that androstenediol products are illegal, check advertisements for various replacements, such as androstenetrione.

Ginseng, Herbals, and Exercise and Sports Performance Herbs contain various nutrients and phytonutrients, such as vitamins, minerals, and antioxidants, that may be part of a healthful diet. Additionally, herbal products have been used for centuries for their purported health benefits; St. John’s wort has been used to treat depression, kava kava to reduce stress and anxiety, Echinacea www.mhhe.com/williams9

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to reduce symptoms of the common cold, and numerous herbals to promote weight loss. In some countries, many herbals are regulated as drugs, but in the United States most are regulated as dietary supplements. A detailed discussion of the health effects of herbals is beyond the scope of this text. In general, however, well controlled research with most herbal supplements and health outcomes is limited. Some may be effective and others not. For example, Shah and others, in a meta-analysis, found that Echinacea decreased the odds of developing the common cold by 58 percent and the duration of a cold by 1.4 days and concluded that the published evidence supports Echinacea’s benefit in decreasing the incidence and duration of the common cold. On the other hand, the Consumers Union indicated there is no good clinical evidence for various supplements, including herbals such as Hoodia, promoted for weight loss. Chitturi and Farrell noted that some herbal remedies marketed for weight reduction have been causally associated with significant liver injury. Moreover, the Consumers Union also notes that herbal supplements can interact dangerously with medications. For example, Echinacea may interact with various drugs, including those for allergies, anxiety, asthma, diabetes, and high serum cholesterol. Individuals using herbal products for health purposes should consult with their physicians. Also recall that ephedra, an herbal supplement, may be dangerous in and by itself. Herbals have also been marketed as ergogenic aids for athletes. Unfortunately, with the exception of ginseng and related products, limited research has evaluated their ability to enhance exercise or sport performance.

Do ginseng or ciwujia enhance exercise or sport performance? Ginseng and ciwujia are comparable herbs, and both have been studied for their potential effects on exercise or sport performance. Ginseng Extracts derived from the plant family Araliaceae contain numerous chemicals that may influence human physiology, the most important being the glycosides, or ginsenosides. Collectively, these extracts are referred to as ginseng, and their physiologic effects vary depending on the plant species, the part of the plant used, and the place of origin. The most common forms of ginseng include Chinese or Korean (Panax ginseng), American (Panax quinquefolium), Japanese (Panax japonicum), and Russian/ Siberian (Eleutherococcus senticosus). Eleutherococcus senticosus is a totally different plant from Araliaceae, but it is recognized by some as a legitimate form of ginseng and its ginsenosides are also referred to as eleutherosides. The type and amount of ginsenosides present vary greatly among the different forms of ginseng. Using such labels as Ginseng Energy, ginseng has been marketed in various forms as a means of enhancing health and physical performance (see figure 13.12). Although the underlying mechanisms are unknown, ginseng is believed to influence neural and hormonal activity in the body and has also been theorized to enhance the immune system. The most prevalent theory suggests ginseng may stimulate the hypothalamus, the part of the brain that controls the pituitary gland, an endocrine gland often referred to as the master 552

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F I G U R E 1 3 . 1 2 Various ginseng products are available as dietary supplements, some being marketed directly to athletes.

gland. The pituitary gland releases hormones that influence other endocrine glands in the body, such as the adrenal gland. The adrenal gland releases cortisol, a hormone involved in the response to stress. The Russians conducted much of the early research with ginseng, and used the term “adaptogens” to characterize its ability to increase resistance to the catabolic effects of stress. Because excessive stress is believed to influence the development of a number of chronic diseases, particularly coronary heart disease, ginseng has been used for its alleged therapeutic properties. The Russians believed that ginseng helped develop resistance not only to mental stress but also to the physical stress of intense exercise training. Other theories suggest ginseng supplementation may influence physical performance in other ways as well, such as increased cardiac function, blood flow, and oxygen transport during exercise; increased oxygen utilization and decreased lactic acid levels during exercise; enhanced muscle glycogen synthesis after exercise; and a positive effect on nitrogen or protein balance. In essence, given these theorized antistress effects, restorative effects, and metabolic effects, ginseng supplementation is theorized to enhance sport performance by allowing athletes to train more intensely and by influencing physiological processes associated with an antifatiguing effect that increase stamina during competition. It should be noted that although numerous theories have been advanced in attempts to explain the alleged ergogenic effects of ginseng supplementation, an underlying mechanism has yet to be determined. Although numerous studies investigated the ergogenic possibilities of ginseng supplementation, few were well-controlled. Research design flaws included no control or placebo group, no double-blind protocol, no randomization of order of treatment, and no statistical analysis. Highlighting these methodological problems in an extensive 1994 review of the ergogenic effect of ginseng supplementation, Michael Bahrke and William Morgan

concluded that there is a lack of controlled research demonstrating the ability of ginseng to improve or prolong performance. Subsequent to the review by Bahrke and Morgan, several wellcontrolled studies evaluated the ergogenic effects of both standardized ginseng extracts and commercial products and reported no significant effects. For example, Dowling and others reported no effect of Eleutherococcus senticosus on metabolic (oxygen uptake and lactic acid accumulation), physiologic (heart rate and ventilation), or psychologic (ratings of perceived exertion) responses to submaximal and maximal running. Using a similar research protocol but with cycling, Engels and Wirth reported no ergogenic effect of Panax ginseng. Other well-controlled studies by Engels and his associates have found no ergogenic effect of Panax ginseng on high-intensity, interval anaerobic exercise protocols. However, Ziemba and others reported that although Panax ginseng did not influence exercise capacity in soccer players, it did improve multiple-choice reaction time before and during a cycling exercise task. Such an effect may be of benefit to athletes who must react quickly in sports. This finding merits additional research. Overall, in an update of their 1994 review, which includes an additional 35 reports, Bahrke and Morgan note that although more well-controlled research is needed, they again concluded that there is an absence of compelling research evidence regarding the efficacy of ginseng use to improve physical performance in humans. In an analysis of herbal supplements and exercise performance, Williams and Branch cited several other recent major reviews supporting the conclusions of Bahrke and Morgan. Goulet and Dionne reviewed studies evaluating the effect of Eleutherococcus senticosus on exercise performance, and concluded that it offers no advantage during exercise endurance tests ranging in duration from 6 to 120 minutes. Most recently, Palisin and Stacy concluded that ginsengs cannot be recommended to improve athletic performance. Most commercial ginseng preparations appear to have relatively low acute or chronic toxicity when taken in dosages recommended by the manufacturer. Coon and Ernst noted that the most commonly experienced adverse effects of Panax ginseng are headache and sleep and gastrointestinal disorders. These effects may be attributed to the postulated stimulant effect of ginseng, or possibly to additional substances in the commercial preparation, such as the stimulant ephedrine. In general, however, they found that Panax ginseng, when taken alone and not combined with other substances, is rarely associated with adverse effects. For athletes involved in sports that may use drug testing, the use of ginseng products containing ephedrine could lead to disqualification. Some research suggests long-term ginseng supplementation may prevent some adverse effects of stress on the immune system. Although not studied extensively in athletes, a healthier immune system could help prevent illness or some of the symptoms of the overtraining syndrome during high-intensity training. However, Engels and others recently reported Panax ginseng had no significant effect on immune functions during recovery from intense anaerobic exercise. Given the available scientific evidence, ginseng supplements cannot be recommended. The consumer should also be aware that

commercial ginseng products may suffer from quality control. An assay of fifty commercial ginseng preparations indicated that over 10 percent of the products contained no detectable ginsenosides, and the amount in the remaining products varied from 1.9–9.0 percent. Many commercial products contain alcohol. Individuals who desire to experiment with long-term ginseng supplementation should consult with their physicians, because ginseng use may exacerbate various health problems, such as high blood pressure. Ciwujia Ciwujia, a Chinese herb, is similar to ginseng. Cheuvront and others indicate that ciwujia is extracted from Araliaceae, the same plant family as Panax ginseng. Along with Plowman and others, they also note that it may be derived from the leaves of Eleutherococcus senticosus. Ciwujia was first marketed as the commercial sports supplement, Endurox™. Currently it is marketed as Endurox Excel, whose advertisements suggest that it can increase fat oxidation (possibly sparing muscle glycogen), reduce lactate accumulation, raise the anaerobic threshold, lower the heart rate while maintaining the same level of workout intensity, and speed workout recovery. However, most of the claims for ciwujia are based on clinical trials with poor experimental designs. Plowman and others noted that none of the studies followed a randomized crossover or double-blind protocol, nor was the use of a placebo mentioned. None have been published in peer-reviewed journals. Studies by Plowman, Cheuvront, and their associates, using double-blind, placebo-controlled, crossover experimental designs and published in peer-reviewed journals, reported that supplementation with Endurox™ (800 mg for 7–10 days) had no significant effect on heart rate, oxygen consumption, respiratory exchange ratio (a measure of fat oxidation), lactic acid accumulation, or ratings of perceived exertion during either cycle ergometer or stairclimbing exercise. The investigators indicated their studies did not verify the claims made for Endurox™. Based on the available evidence, products containing ciwujia do not appear to enhance exercise performance, and thus are not recommended for use by endurance athletes.

What herbals are effective ergogenic aids? As noted earlier, caffeine may be derived from various herbals, such as guarana and the kola nut, whereas ephedra is a constituent of ma huang. Other than these and ginseng, athletes have experimented with a variety of other herbals, including cayenne for energy and gamma-oryzanol to increase muscle mass. Kundrat, in a report on herbs and athletes, indicated that doubleblind, placebo-controlled human research on herb use by athletes is limited or nonexistent. One reason may be that, at least in the United States, herbs are regulated as dietary supplements and are not required to be standardized, so there is little consistency among different brands. Moreover, herbal sport supplements may often contain several herbals and other substances in a commercial product, so it is difficult to isolate the potential ergogenic effect of a single ingredient. Studies conducted with such commercial herbal-based sports supplements, such as the recent study by Earnest and others, generally report no significant ergogenic effects. www.mhhe.com/williams9

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Nevertheless, several reviews of herbal supplementation and exercise performance are available. In their review, Williams and Branch noted that much of what we know about the efficacy of herbal supplements as ergogenics is based on anecdotal data and poorly controlled studies. However, based on their analysis, they concluded that none of the following herbals have sufficient research support as a means of enhancing exercise or sport performance: bee pollen, capsicum, gamma-oryzanol, ginkgo biloba, kava kava, St. John’s wort, Tribulus terrestris, and yohimbine. Recent studies support this viewpoint. For example, Neychev and Mitev found no effect of Tribulus terrestris supplementation for 4 weeks on testosterone or androstenedione production in young men, its theorized mechanism of action. Moreover, Rogerson and others reported no effects of Tribulus terrestris supplementation (450 mg/day for 5 weeks) on lean muscle mass and strength in Australian elite male rugby league players. Ostojic studied the effect of yohimbine in professional soccer players, who consumed 20 milligrams per day for 21 days. There was no significant effect on body mass, muscle mass, or performance indicators (bench and leg press, vertical jump, dribble and power test results, shuttle run) in these elite athletes. Subsequent to these reviews, several other herbals have been studied for their purported ergogenic potential. The herb Cordyceps sinensis is a health tonic from China; although it is rare, a synthetic version is now available; one version is CordyMax Cs-4. Cordyceps sinensis is theorized to have favorable effects on the heart and circulation to improve oxidative capacity and endurance performance. However, Parcell and others reported that 5 weeks of CordyMax Cs-4 supplementation had no effect on aerobic capacity of endurance-trained male cyclists. Rhodiola rosea, like ginseng, is categorized as an adaptogen, and has been theorized to enhance endurance performance through a stimulating effect. Walker and others also noted the herb is purported to enhance physical performance by improving adenosine triphosphate (ATP) turnover. In a preliminary study, De Bock and others found that an acute dose (200 milligrams) of Rhodiola rosea improved time to exhaustion by 3 percent on a cycle ergometer, but there was no significant effect following 4 weeks of supplementation with 200 milligrams daily. Colson and others reported that Rhodiola rosea, in a product that also contained Cordyceps sinensis, had no effect on muscle tissue oxygen saturation or on cycling time to exhaustion. In their study, De Bock and others reported no effect on maximal strength or various measures of reaction time or movement time. Walker and others, using nuclear magnetic resonance spectroscopy, reported no significant effects of Rhodiola rosea supplementation on ATP turnover during a wrist flexion test to exhaustion, nor were ratings of perceived exertion (RPE) or time to exhaustion different between the placebo and experimental sessions. In their review, Walker and Robergs note that studies with Rhodiola rosea have produced mixed results when attempting to demonstrate an ergogenic effect during exercise in humans. Additional research is recommended. Cytoseira canariensis has been marketed as a new sports supplement designed to increase muscle mass and decrease body fat

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by inhibiting myostatin. Myostatin is a protein known as a growth and differentiation factor, and its role is to inhibit (not promote) the growth of muscles. Theoretically, by inhibiting the effects of myostatin, muscle growth may be increased. However, Darryn Willoughby, an exercise scientist at Baylor University, reported that 1,200 milligrams/day of Cystoseira canariensis supplementation during 12 weeks of resistance training had no effect on serum myostatin levels, nor did it have any effect on muscle mass, muscle strength, or body fat. As noted in chapter 8, increasing erythropoietin (EPO) levels by living at altitude may confer a beneficial effect on oxygen transport during exercise by increasing production of red blood cells. In a recent study, Whitehead and others found that subjects receiving 8,000 mg of Echinacea daily for 28 days significantly increased their serum erythropoietin levels. However, there was no change in red blood cells or hemoglobin concentrations. This is an interesting finding, and more research is recommended to evaluate the ergogenicity of Echinacea supplementation. Kundrat indicated that athletes should be concerned about the safety of herbals, as there may be some side effects or herb-drug interactions. For athletes using herbals for weight loss, Pittler concluded that the potential health risks recommended against such use due to an increased risk relative to benefit. Athletes contemplating using herbals should consult with their healthcare professional.

Ke y C o n c e p t s 䉴 Results from well-controlled research indicate that ginseng and

related adaptogens, such as ciwujia, are not effective ergogenic aids. 䉴 There is limited, well-controlled research regarding the effect of herbals on exercise or sport performance, and that which is available suggests herbal sports supplements are not effective ergogenic aids.

Sports Supplements: Efficacy, Safety, and Permissibility What sports supplements are considered to be effective, safe, and permissible? Throughout this text we have discussed the role of a wide variety of dietary supplements relative to their efficacy, safety, and permissibility as ergogenic aids, namely their potential to enhance sport or exercise performance. Metabolites of carbohydrate and fat, special forms of protein, numerous amino acids, vitamins, and minerals, as well as food drugs and herbal supplements have all been studied for their ergogenic potential. In their position stand on nutrition and athletic performance, the American College of Sports Medicine, the American Dietetic Association, and the Dietitians of Canada classified sports supplements into four cate-

gories; the Australian Institute of Sport developed similar guidelines. The four categories are described in the following text and, based on the currently available research presented in this text, include a list of those sports supplements that best fit that category. Listing in a specific category is based primarily on the ability of the supplement to enhance performance or promote training as a means to performance enhancement when added to a healthful diet that already provides adequate Calories and essential nutrients. The ergogenic effect of the supplement may also be limited to a specific type of athletic endeavor, such as sodium bicarbonate and high-intensity anaerobic exercise dependent primarily on anaerobic glycolysis. Individual needs also may dictate the inclusion of a specific dietary supplement for any given athlete. For example, females in weight-control sports may benefit from iron supplements to help prevent iron deficiency and anemia, and from calcium supplements to help maintain bone mass. • Sports supplements that are effective, safe, and permissible. The efficacy of these supplements is supported by quality research, they are considered safe to use, and they are not prohibited for use by sport-governing organizations. Although research indicates they are effective ergogenics, responses of individual athletes may vary. Caffeine Carbohydrate (Sports bars/gels) Creatine Sodium bicarbonate Water • Sports supplements that may be effective, are safe, and are permissible. Preliminary research may suggest some ergogenic effects, but the data are too limited to make a positive recommendation. Additional research is needed to confirm or refute preliminary findings. These supplements are safe and permissible. Aspartate salts Beta-arginine Colostrum Glycerol Phosphate salts Protein/essential amino acids Pseudoephedrine Whey protein • Sports supplements that are not effective. Research indicates these supplements do not enhance exercise performance. However, athletes in weight-control sports consuming a reducedCalorie diet may help prevent vitamin and mineral deficiencies by consuming a multivitamin/mineral supplement. Antioxidant vitamins Arginine B vitamin complex BCAA Bee pollen Boron Calcium Carnitine (L-carnitine) Choline Chondroitin

Chromium Ciwujia Conjugated linoleic acid CoQ10 Cordyceps sinensis Fat loading Gamma oryzanol Ginseng Glucosamine Glutamine Glycine HMB Hydroxycitrate Inosine Iron Magnesium Medium-chain triglycerides Niacin Octacosanol Omega-3 fatty acids Ornithine Pyruvate Rhodiola rosea Ribose Selenium Tribulus terrestris Tryptophan Vanadium Vitamin A Vitamin C Vitamin D Vitamin E Wheat germ oil Yohimbine Zinc • Sports supplements that should not be used because they are not safe nor are they permissible. WADA prohibits use of these supplements and they may also cause various health problems. Note also that some dietary supplements, such as herbal testosterone precursors like Tribulus terrestris, may be contaminated with anabolic agents that may result in a positive doping test. Androstenediol Androstenedione DHEA Ephedra/ephedrine Keep in mind that numerous supplements are marketed to athletes, including claims to promote testosterone production, maximize muscle mass, strength, and power, and enhance training and performance in competition. With few exceptions, research does not support the efficacy of most commercial sports supplements. Moreover, some supplements may be contaminated with substances that could lead to a positive doping test. In most cases athletes may meet their nutritional needs through consumption of a well-planned, healthful diet.

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A P P L I C AT I O N If you or one of your colleagues is physically trained or an athlete, you might want to conduct a small case study with caffeine. Either of you should be physically trained to run a mile, swim 500 meters, or some comparable exercise task of 5–10 minutes of high-intensity exercise. Other exercise tasks of shorter duration may be selected. The activity is best done indoors to control environmental conditions. One of you can serve as the investigator and the other as the subject. A third colleague will administer the treatment on a double-blind

E X E R C I S E basis. Randomly, over a 5-week period, the subject will participate in five trials, each involving maximal performance for the selected activity. Thirty minutes before the test, the subject should consume either two caffeine tablets, each containing 200 milligrams of caffeine (Vivarin or comparable over-the-counter tablet) or a comparable placebo (two multivitamin tablets) with some water. The subject’s eyes should be closed while taking the tablets. Here is the weekly protocol.

Week 1—Learning protocol; no placebo or caffeine Week 2—Placebo or caffeine Week 3—Caffeine or placebo (opposite of week 2) Week 4—Placebo or caffeine Week 5—Caffeine or placebo (opposite of week 4) Record the performance times for each, average the two placebo and two caffeine trials, and compare the results for improvement, if any.

Caffeine Trial Week 1 (no placebo or caffeine)

Week 2 (placebo or caffeine)

Week 3 (opposite of week 2)

Week 4 (placebo or caffeine)

Week 5 (opposite of week 4)

Performance Time

Review Questions—Multiple Choice 1. Of the drugs and supplements discussed in this chapter, which have the most research supporting their ability to enhance exercise or sports performance? (a) caffeine and androstenedione (b) ginseng and ephedrine (c) alcohol and DHEA (d) androstenedione and ephedrine (e) sodium bicarbonate and caffeine 2. About how many milligrams of caffeine are in a 6 ounce cup of perked coffee? (a) 25–30 (b) 100–125 (c) 300–400 (d) 500–600 (e) 1,000 3. Which of the following is not a physiological effect of caffeine? (a) decreases the metabolic rate (b) stimulates the central nervous system (c) increases the secretion of epinephrine (d) increases heart rate and force of contraction (e) increases force of skeletal muscle contractility 556

4. For an average-size male adult (150 pounds), the consumption of four (4) drinks within a very short period of time would elevate the blood alcohol concentration (BAC) to about what level? (a) 0.01 (b) 0.02 (c) 0.05 (d) 0.10 (e) 0.15 5. As a potential ergogenic aid, sodium bicarbonate would be most likely suited to which type of athlete? (a) marathon runner (26.2 miles) (b) 100-meter sprinter (track) (c) 400-meter sprinter (track) (d) pole vaulter (field) (e) discus thrower (field) 6. Increasing research suggests that moderate alcohol consumption, or “low risk” drinking, may reduce the risk of CHD and all-cause mortality. All of the following, except which, are hypothesized to contribute to this reduced risk? (a) a relaxation effect and reduced anxiety

C H A P T E R 1 3 Food Drugs and Related Supplements

(b) decreased platelet aggregability (decreased possibility of blood clots) (c) increased blood flow to the brain (d) reduced caloric intake, induced weight loss, and prevented metabolic syndrome (e) an increase in HDL-cholesterol 7. Research generally supports the theory that caffeine may enhance performance in longdistance endurance events. Which of the following is the least likely hypothesis? (a) It may exert a psychological stimulating effect. (b) It stimulates the release of epinephrine from the adrenal gland. (c) It decreases the use of both free fatty acids and muscle glycogen. (d) It may decrease the perception of effort during exercise. (e) It may exert a direct effect on the muscles to increase muscle contractile force. 8. Anabolic/androgenic steroids (AAS) are drugs popular with individuals with muscle dysmorphia, or those who desire to

viduals are precursors, or prohormones, for testosterone? (a) creatine and conjugated linoleic acid (b) gamma oryzanol and ginseng (c) Cordyceps sinensis and Cytoseira canariensis (d) HMB and tribulus terrestris (e) androstenedione and DHEA 10. Which of the following ergogenic aids are currently permitted for use by athletes in all sports competitions according to the

doping list created by the World AntiDoping Agency (WADA)? (a) caffeine and ephedrine (b) sodium bicarbonate and caffeine (c) caffeine and alcohol (d) androstenedione and DHEA (e) ginseng and ephedrine

Answers to multiple-choice questions: 1. e; 2. b; 3. a; 4. d; 5. c; 6. d; 7. c; 8. c; 9. e; 10. b.

increase muscle mass even though already very muscular. AAS are designed to mimic mainly the anabolic effects of which natural hormone in the body? (a) insulin (b) human growth hormone (HGH) (c) testosterone (d) androsterone (e) estrogen 9. Which of the following dietary supplements marketed to strength-trained indi-

Review Questions—Essay 1. Discuss both the potential beneficial and adverse health effects of consuming various amounts of alcohol. 2. Discuss the efficacy, safety, and legality of caffeine supplementation as an ergogenic aid for aerobic endurance athletes. 3. Discuss the efficacy, safety, and legality of sodium bicarbonate supplementation as an

ergogenic aid. In which types of sports would it appear to be most effective? 4. Compare and contrast the effects of testosterone, versus its congeners DHEA and androstenedione, as ergogenic aids for the development of muscle mass and strength. Discuss possible health risks associated with use of each.

5. What is ginseng, why is it purported to be an ergogenic aid, and does research support its efficacy as an ergogenic?

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C H A P T E R 1 3 Food Drugs and Related Supplements

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APPENDIX

A

Units of Measurement: English System— Metric System Equivalents The Metric System and Equivalents

Level Measures and Weights

To measure ingredients, a standardized system known as the System Internationale (SI) has been established that is interpreted on an international basis. The SI is based on the metric system. However, in the United States we also employ another set of measure and weight, the English system. In the field of dietetics, both systems are employed. The following tables give the quantities of the measures besides stating equivalents. With this information it is possible to calculate in either system of measure and weight.

1 teaspoon

=

3 teaspoons

=

2 tablespoons

=

4 tablespoons

=

Household Measures (Approximations)

8 tablespoons

=

16 tablespoons

=

2 cups

=

4 cups

=

4 quarts

=

For easy computing purposes, the cubic centimeter (cc) is considered equivalent to 1 gram: 1 cc = 1 gram = 1 milliliter (ml) For easy computing purposes, 1 ounce equals 30 grams or 30 cubic centimeters. 1 quart 1 pint 1 cup 1/2 cup 1 glass (8 ounces) 1/2 glass (4 ounces) 1 orange juice glass 1 tablespoon 1 teaspoon

564

= = = = = = = = =

960 grams 480 grams 240 grams 120 grams 240 grams 120 grams 100–120 grams 15 grams 5 grams

5 cc or 5 ml 5 grams 1 tablespoon 15 cc 15 grams 30 cc 30 grams 1 ounce (fluid) 1/4 cup 60 cc 60 grams 1/2 cup 120 cc 120 grams 1 cup 240 grams 240 ml (fluid) 8 ounces (fluid) 1/2 pound 1 pint 480 grams 480 ml (fluid) 16 ounces (fluid) 1 pound 2 pints 1 quart 960 cc 960 ml (fluid) 2 pounds 1 gallon

Units of Weight 1 ounce 1 pound 1 gram 1 kilogram

Ounce 1.0 16.0 0.035 35.3

= = = =

Pound 0.06 1.0 .002 2.2

Gram 28.4 454 1.0 1,000

Pint 0.062 1.0 2.0 0.002 2.112

Quart 0.031 0.5 1.0 0.001 1.056

Kilogram 0.028 0.454 0.001 1.0

Units of Volume 1 ounce 1 pint 1 quart 1 milliliter 1 liter

Ounce 1.0 16.0 32.0 0.034 33.8

= = = = =

Milliliter 29.57 473 946 1.0 1,000

Liter 0.029 0.473 0.946 0.001 1.0

Units of Length 1 millimeter 1 centimeter 1 inch 1 foot 1 yard 1 meter

= = = = = =

Millimeter 1.0 10.0 25.4 304.8 914.4 1,000

Centimeter 0.1 1.0 2.54 30.48 91.44 100

Inch 0.0394 0.394 1.0 12.0 36.0 39.37

1 kilometer 1 mile

= =

1,000 meters 1,760 yards

= 0.6216 mile = 1.61 kilometers

Foot 0.0033 0.033 0.083 1.0 3.0 3.28

Yard 0.0011 0.011 0.028 0.333 1.0 1.094

Meter 0.001 0.01 0.025 0.305 0.914 1.0

Units of mechanical, thermal, and chemical energy (approximate equivalents) Foot-pounds

Kilogram-meters

Kilojoules

Watts*

Kilocalories

Oxygen**

1 foot-pound

1

0.138

0.00136

0.0226

0.00032

0.000064

1 kilogram-meter

7.23

1

0.0098

0.163

0.0023

0.00046

0.239

0.047

1 kilojoule 1 watt* 1 kilocalorie 1 liter oxygen**

737 44.27

102 6.12

3,088

427

15,585

2,154

1

16.66

0.06

1

0.0143

0.0028

4.18

0.00024

1

0.198

5.047

1

21.1

351.9

Note: Read all tables across, such as 1 watt equals 44.27 foot-pounds per minute; 1 foot-pound equals 0.0226 watt. *Watts are units of power expressed per minute. **Equivalents are based upon 1 liter of oxygen metabolizing carbohydrate. Energy equivalents would be slightly less on a mixed diet of carbohydrate, fat, and protein. For example, 1 liter of oxygen would equal only 4.82 kilocalories on such a mixed diet.

www.mhhe.com/williams9

565

APPENDIX

B

Approximate Caloric Expenditure per Minute for Various Physical Activities Body weight Kilograms Pounds

45 100

48 105

50 110

52 115

55 120

57 125

59 130

61 135

64 140

66 145

68 150

70 155

1.0 1.2

1.0 1.3

1.1 1.4

1.1 1.5

1.2 1.5

1.3 1.6

1.3 1.7

1.4 1.7

1.4 1.8

1.5 1.8

1.5 1.9

1.5 2.0

2.7

2.9

3.0

3.1

3.3

3.4

3.5

3.7

3.8

3.9

4.1

4.2

3.1

3.3

3.5

3.6

3.8

4.0

4.1

4.3

4.5

4.6

4.8

4.9

3.6 2.7 5.9

3.8 2.9 6.1

4.0 3.0 6.4

4.2 3.1 6.7

4.4 3.3 7.0

4.6 3.4 7.3

4.7 3.5 7.6

4.9 3.7 7.9

5.1 3.8 8.2

5.3 3.9 8.5

5.4 4.1 8.8

5.6 4.2 9.1

3.1 3.9

3.3 4.1

3.4 4.3

3.6 4.5

3.8 4.7

4.0 4.9

4.1 5.1

4.3 5.3

4.4 5.5

4.5 5.7

4.7 5.9

4.8 6.0

3.0 4.9 6.5

3.1 5.2 6.8

3.3 5.5 7.2

3.5 5.7 7.5

3.6 6.0 7.8

3.8 6.2 8.2

3.9 6.5 8.5

4.1 6.7 8.8

4.2 7.0 9.2

4.4 7.2 9.5

4.5 7.5 9.9

4.7 7.7 10.2

1.9 4.2 7.3 10.7 2.7

2.0 4.4 7.6 11.2 2.8

2.1 4.6 8.0 11.7 3.0

2.2 4.8 8.4 12.3 3.1

2.3 5.1 8.7 12.8 3.3

2.4 5.3 9.1 13.3 3.4

2.5 5.5 9.5 13.9 3.5

2.6 5.7 9.8 14.4 3.7

2.7 5.9 10.0 14.9 3.8

2.8 6.1 10.5 15.5 3.9

2.9 6.4 10.9 16.0 4.1

3.0 6.6 11.3 16.5 4.2

3.4 9.7

3.6 10.1

3.8 10.6

4.0 11.1

4.1 11.6

4.3 12.1

4.5 12.6

4.7 13.1

4.8 13.6

5.0 14.1

5.2 14.6

5.4 15.1

1.9 4.4 5.7

2.0 4.6 6.0

2.1 4.9 6.3

2.2 5.1 6.6

2.3 5.3 6.9

2.4 5.5 7.2

2.5 5.8 7.5

2.6 6.0 7.8

2.7 6.2 8.1

2.8 6.4 8.4

2.9 6.7 8.7

3.0 6.9 9.0

Sedentary activities Lying quietly Sitting and writing, card playing, etc. Standing with light work, cleaning, etc. Physical activities

566

Archery Badminton Recreational singles Social doubles Competitive Baseball Player Pitcher Basketball Half court Recreational Vigorous competition Bicycling, level (mph) (min/mile) 5 12:00 10 6:00 15 4:00 20 3:00 Bowling Calisthenics Light type Timed vigorous Canoeing (mph) (min/mile) 2.5 24 4.0 15 5.0 12

When using this appendix, keep these points in mind. A. The figures are approximate and include the resting energy expenditure (REE). Thus, the total cost of the exercise includes not only the energy expended by the exercise itself, but also the amount you would have used anyway during the same period. Suppose you ran for 1 hour and the calculated energy cost was 800 Calories. During that same time at rest, your REE may have been 75 Calories, so the net cost of the exercise is 725 Calories. B. The figures in the table are only for the time you are performing the activity. For example, in an hour of basketball, you may exercise strenuously for only 35 to 40 minutes, as you may take time-outs and may rest during foul shots. In general, record only the amount of time that you are actually exercising during the activity. C. The energy cost, expressed in Calories per minute, will vary for different physical activities in a given indi-

vidual depending on several factors. For example, the caloric cost of bicycling will vary depending on the type of bicycle, going uphill and downhill, and wind resistance. Walking with hand weights or ankle weights will increase energy output. Energy cost for swimming at a certain pace will depend on swimming efficiency, so the less efficient swimmer will expend more Calories. Thus, the values expressed here are approximations and may be increased or decreased depending upon various factors that influence energy cost for a specific physical activity. D. Not all body weights could be listed, but you may approximate by using the closest weight listed. E. There may be small differences between males and females, but not enough to make a significant difference in the total caloric value for most exercises.

Body weight 73 160

75 165

77 170

80 175

82 180

84 185

86 190

89 195

91 200

93 205

95 210

98 215

100 220

1.6 2.0

1.6 2.1

1.7 2.2

1.7 2.2

1.8 2.3

1.8 2.4

1.9 2.4

1.9 2.5

2.0 2.5

2.0 2.6

2.1 2.7

2.1 2.7

2.2 2.8

4.4

4.5

4.6

4.8

4.9

5.0

5.2

5.3

5.4

5.6

5.7

5.9

6.0

5.1

5.3

5.4

5.6

5.7

5.9

6.0

6.2

6.4

6.5

6.7

6.9

7.0

5.8 4.4 9.4

6.0 4.5 9.7

6.2 4.6 10.0

6.4 4.8 10.3

6.6 4.9 10.6

6.7 5.0 10.9

6.9 5.2 11.2

7.1 5.3 11.5

7.3 5.4 11.8

7.4 5.6 12.1

7.6 5.7 12.4

7.8 5.9 12.7

8.0 6.0 13.0

5.0 6.3

5.2 6.5

5.3 6.7

5.5 6.9

5.6 7.1

5.8 7.3

5.9 7.4

6.1 7.7

6.3 7.9

6.4 8.0

6.6 8.2

6.8 8.5

6.9 8.6

4.8 8.0 10.5

5.0 8.2 10.9

5.1 8.5 11.2

5.3 8.7 11.5

5.4 9.0 11.9

5.6 9.2 12.2

5.7 9.5 12.5

5.9 9.7 12.9

6.0 10.0 13.2

6.2 10.2 13.5

6.4 10.5 13.8

6.5 10.7 14.2

6.7 11.0 14.5

3.1 6.8 11.6 17.1 4.4

3.2 7.0 12.0 17.6 4.5

3.3 7.2 12.4 18.1 4.6

3.4 7.4 12.7 18.7 4.8

3.5 7.6 13.1 19.2 4.9

3.6 7.9 13.4 19.7 5.0

3.7 8.1 13.8 20.3 5.2

3.8 8.3 14.2 20.8 5.3

3.9 8.5 14.5 21.3 5.5

4.0 8.7 14.9 21.9 5.6

4.1 8.9 15.3 22.4 5.7

4.2 9.1 15.6 22.9 5.9

4.3 9.4 16.0 23.5 6.0

5.5 15.6

5.7 16.1

5.9 16.6

6.1 17.1

6.3 17.6

6.4 18.1

6.6 18.6

6.8 19.1

7.0 19.6

7.1 20.0

7.3 20.5

7.5 21.0

7.7 21.5

3.1 7.1 9.3

3.2 7.4 9.5

3.3 7.6 9.8

3.4 7.8 10.1

3.5 8.0 10.4

3.6 8.2 10.7

3.7 8.5 11.0

3.8 8.7 11.3

3.9 8.9 11.6

4.0 9.1 11.9

4.1 9.4 12.2

4.2 9.6 12.5

4.3 9.8 12.8

567

Body weight Kilograms Pounds Dancing Moderately (waltz) Active (square, disco) Aerobic (vigorously) Fencing Moderately Vigorously Football Moderate Touch, vigorous Golf Twosome (carry clubs) Foursome (carry clubs) Power-cart Handball Moderate Competitive Hiking, pack (3 mph) Hockey, field Hockey, ice Horseback riding Walk Sitting to trot Posting to trot Gallop Horseshoes Jogging (see Running) Judo Karate Mountain climbing Paddle ball Pool (billiards) Racquetball Roller skating (9 mph) Running (steady state) (mph) (min/mile) 5.0 12:00 5.5 10:55 6.0 10:00 7.0 8:35 8.0 7:30 9.0 6:40 10.0 6:00 11.0 5:28 12.0 5:00 Sailing, small boat Skating, ice (9 mph) Skating, in-line (13 mph) Skiing, cross-country (mph) (min/mile) 2.5 24:00 4.0 15:00 5.0 12:00

568

45 100

48 105

50 110

52 115

55 120

57 125

59 130

61 135

64 140

66 145

68 150

70 155

3.1 4.5 6.0

3.3 4.7 6.3

3.5 5.0 6.7

3.6 5.2 7.0

3.8 5.4 7.3

4.0 5.6 7.6

4.1 5.9 7.9

4.3 6.1 8.2

4.5 6.3 8.5

4.6 6.6 8.8

4.8 6.8 9.1

4.9 7.0 9.4

3.3 6.6

3.5 7.0

3.6 7.3

3.8 7.7

4.0 8.0

4.1 8.3

4.3 8.7

4.5 9.0

4.6 9.4

4.8 9.7

5.0 10.0

5.2 10.4

3.3 5.5

3.5 5.8

3.6 6.1

3.8 6.4

4.0 6.6

4.1 6.9

4.3 7.2

4.5 7.5

4.6 7.8

4.8 8.0

5.0 8.3

5.2 8.6

3.6 2.7 1.9

3.8 2.9 2.0

4.0 3.0 2.1

4.2 3.1 2.2

4.4 3.3 2.3

4.6 3.4 2.4

4.7 3.5 2.5

4.9 3.7 2.6

5.1 3.8 2.7

5.3 3.9 2.8

5.4 4.1 2.9

5.6 4.2 3.0

6.5 7.7 4.5 5.0 6.6

6.8 8.0 4.7 6.3 7.0

7.2 8.4 5.0 6.7 7.3

7.5 8.8 5.2 7.0 7.7

7.8 9.2 5.4 7.3 8.0

8.2 9.6 5.6 7.6 8.3

8.5 10.0 5.9 7.9 8.7

8.8 10.4 6.1 8.2 9.0

9.2 10.8 6.3 8.5 9.4

9.5 11.1 6.6 8.8 9.7

9.9 11.5 6.8 9.1 10.0

10.2 11.9 7.0 9.4 10.4

1.9 2.7 4.2 5.7 2.5

2.0 2.9 4.4 6.0 2.6

2.1 3.0 4.6 6.3 2.8

2.2 3.1 4.8 6.6 2.9

2.3 3.3 5.1 6.9 3.0

2.4 3.4 5.3 7.2 3.1

2.5 3.5 5.5 7.5 3.3

2.6 3.7 5.7 7.8 3.4

2.7 3.8 5.9 8.1 3.5

2.8 3.9 6.1 8.4 3.7

2.9 4.1 6.4 8.7 3.8

3.0 4.2 6.6 9.0 3.9

8.5 8.5 6.5 5.7 1.5 6.5 4.2

8.9 8.9 6.8 6.0 1.6 6.8 4.4

9.3 9.3 7.2 6.3 1.6 7.1 4.6

9.8 9.8 7.5 6.6 1.7 7.5 4.8

10.2 10.2 7.8 6.9 1.8 7.8 5.1

10.6 10.6 8.2 7.2 1.9 8.1 5.3

11.0 11.0 8.5 7.5 1.9 8.4 5.5

11.5 11.5 8.8 7.8 2.0 8.8 5.7

11.9 11.9 9.2 8.1 2.1 9.1 5.9

12.3 12.3 9.5 8.4 2.2 9.4 6.1

12.8 12.8 9.8 8.7 2.2 9.8 6.4

13.2 13.2 10.2 9.0 2.3 10.1 6.6

6.0 6.7 7.2 8.5 9.7 10.8 12.1 13.3 14.5 2.7 4.2 9.5

6.3 7.0 7.6 8.9 10.2 11.3 12.7 14.0 15.2 2.9 4.4 10.0

6.6 7.3 8.0 9.3 10.7 11.9 13.3 14.6 16.0 3.0 4.6 10.5

7.0 7.7 8.4 9.8 11.2 12.4 13.9 15.3 16.7 3.1 4.8 10.9

7.3 8.0 8.7 10.2 11.6 12.9 14.5 16.0 17.4 3.3 5.1 11.5

7.6 8.4 9.1 10.6 12.1 13.5 15.1 16.7 18.2 3.4 5.2 12.0

7.9 8.7 9.5 11.0 12.6 14.0 15.7 17.3 18.9 3.5 5.5 12.4

8.2 9.0 9.8 11.5 13.1 14.6 16.4 18.0 19.7 3.7 5.7 12.8

8.5 9.4 10.2 11.9 13.6 15.1 17.0 18.7 20.4 3.8 5.9 13.4

8.8 9.7 10.6 12.3 14.1 15.7 17.6 19.4 21.1 3.9 6.1 13.9

9.1 10.0 10.9 12.8 14.6 16.2 18.2 20.0 21.9 4.1 6.4 14.3

9.4 10.4 11.3 13.2 15.1 16.8 18.8 20.7 22.6 4.2 6.6 14.7

5.0 6.5 7.7

5.2 6.8 8.0

5.5 7.2 8.4

5.7 7.5 8.8

6.0 7.8 9.2

6.2 8.2 9.6

6.5 8.5 10.0

6.7 8.8 10.4

7.0 9.2 10.8

7.2 9.5 11.1

7.5 9.9 11.5

7.8 10.2 11.9

A P P E N D I X B Approximate Caloric Expenditure per Minute for Various Physical Activities

Body weight 73 160

75 165

77 170

80 175

82 180

84 185

86 190

89 195

91 200

93 205

95 210

98 215

100 220

5.1 7.3 9.7

5.3 7.5 10.0

5.4 7.7 10.3

5.6 7.9 10.6

5.7 8.2 10.9

5.9 8.4 11.2

6.0 8.6 11.5

6.2 8.9 11.8

6.4 9.1 12.1

6.5 9.3 12.4

6.7 9.5 12.7

6.9 9.8 13.0

7.0 10.0 13.3

5.3 10.7

5.5 11.0

5.7 11.4

5.8 11.7

6.0 12.1

6.2 12.4

6.3 12.7

6.5 13.1

6.7 13.4

6.8 13.8

7.0 14.1

7.1 14.4

7.3 14.8

5.3 8.9

5.5 9.2

5.7 9.4

5.8 9.7

6.0 10.0

6.2 10.3

6.3 10.6

6.5 10.8

6.7 11.1

6.8 11.4

7.0 11.7

7.1 12.0

7.3 12.2

5.8 4.4 3.1

6.0 4.5 3.2

6.2 4.6 3.3

6.4 4.8 3.4

6.6 4.9 3.5

6.7 5.0 3.6

6.9 5.2 3.7

7.1 5.3 3.8

7.3 5.4 3.9

7.4 5.6 4.0

7.6 5.7 4.1

7.8 5.9 4.2

8.0 6.0 4.3

10.5 12.3 7.3 9.7 10.7

10.9 12.7 7.5 10.0 11.0

11.2 13.1 7.7 10.3 11.4

11.5 13.5 7.9 10.6 11.7

11.9 13.9 8.2 10.9 12.1

12.2 14.3 8.4 11.2 12.4

12.5 14.7 8.6 11.5 12.7

12.9 15.0 8.9 11.8 13.1

13.2 15.4 9.1 12.1 13.4

13.5 15.8 9.3 12.4 13.8

13.8 16.2 9.5 12.7 14.1

14.2 16.6 9.8 13.0 14.4

14.5 17.0 10.0 13.3 14.8

3.1 4.4 6.8 9.3 4.0

3.2 4.5 7.0 9.5 4.2

3.3 4.6 7.2 9.8 4.3

3.4 4.8 7.4 10.1 4.4

3.5 4.9 7.6 10.4 4.5

3.6 5.0 7.9 10.7 4.7

3.7 5.2 8.1 11.0 4.8

3.8 5.3 8.3 11.3 4.9

3.9 5.4 8.5 11.6 5.2

4.0 5.6 8.7 11.9 5.2

4.1 5.7 8.9 12.2 5.3

4.2 5.9 9.1 12.5 5.4

4.3 6.0 9.4 12.8 5.6

13.6 13.6 10.5 9.3 2.4 10.4 6.8

14.1 14.1 10.8 9.5 2.5 10.7 7.0

14.5 14.5 11.2 9.8 2.6 11.1 7.2

14.9 14.9 11.5 10.1 2.6 11.4 7.4

15.4 15.4 11.8 10.4 2.7 11.7 7.6

15.8 15.8 12.1 10.7 2.8 12.0 7.9

16.2 16.2 12.5 11.0 2.9 12.4 8.1

16.6 16.6 12.8 11.2 2.9 12.7 8.3

17.1 17.1 13.1 11.6 3.0 13.0 8.5

17.5 17.5 13.5 11.9 3.1 13.4 8.7

17.9 17.9 13.8 12.2 3.2 13.7 8.9

18.4 18.4 14.1 12.5 3.2 14.0 9.1

18.8 18.8 14.5 12.8 3.3 14.4 9.4

9.7 10.7 11.7 13.6 15.6 17.3 19.4 21.4 23.3 4.4 6.8 15.3

10.0 11.1 12.0 14.1 16.1 17.9 20.0 22.1 24.1 4.5 7.0 15.7

10.3 11.4 12.4 14.5 16.6 18.4 20.7 22.7 24.8 4.6 7.2 16.2

10.6 11.7 12.8 14.9 17.1 19.0 21.3 23.4 25.6 4.8 7.4 16.8

10.9 12.1 13.1 15.4 17.6 19.5 21.9 24.1 26.3 4.9 7.6 17.2

11.2 12.4 13.5 15.8 18.1 20.1 22.5 24.8 27.0 5.0 7.9 17.6

11.6 12.8 13.8 16.2 18.5 20.6 23.1 25.4 27.8 5.2 8.1 18.1

11.9 13.1 14.3 16.6 19.0 21.2 23.7 26.1 28.5 5.3 8.3 18.7

12.2 13.4 14.6 17.1 19.5 21.7 24.2 26.8 29.2 5.4 8.5 19.1

12.5 13.8 15.0 17.5 20.0 22.2 24.8 27.5 30.0 5.6 8.7 19.5

12.8 14.1 15.4 17.9 20.5 22.8 25.4 28.1 30.7 5.7 8.9 20.0

13.1 14.5 15.7 18.4 21.0 23.3 26.0 28.8 31.5 5.9 9.1 20.6

13.4 14.8 16.1 18.8 21.5 23.9 26.7 29.5 32.2 6.0 9.4 21.0

8.0 10.5 12.3

8.3 10.9 12.7

8.5 11.2 13.1

8.8 11.5 13.5

9.0 11.9 13.9

9.3 12.2 14.3

9.5 12.5 14.7

9.8 12.9 15.0

10.0 13.2 15.4

10.3 13.5 15.8

10.6 13.8 16.2

10.8 14.2 16.6

11.1 14.5 17.0

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Body weight Kilograms Pounds Skiing, downhill Soccer Squash Normal Competition Swimming (yards/min) Backstroke 25 30 35 40 Breaststroke 20 30 40 Front crawl 20 25 35 45 50 Table tennis Tennis Singles, recreational Doubles, recreational Competition Volleyball Moderate, recreational Vigorous, competition Walking (mph) (min/mile) 1.0 60:00 2.0 30:00 2.3 26:00 3.0 20:00 3.2 18:45 3.5 17:10 4.0 15:00 4.5 13:20 5.0 12:00 5.4 11:10 5.8 10:20 Water skiing Weight training Wrestling

570

45 100

48 105

50 110

52 115

55 120

57 125

59 130

61 135

64 140

66 145

68 150

70 155

6.5 5.9

6.8 6.2

7.2 6.6

7.5 6.9

7.8 7.2

8.2 7.5

8.5 7.8

8.8 8.1

9.2 8.4

9.5 8.7

9.9 9.0

10.2 9.3

6.7 7.7

7.0 8.0

7.3 8.4

7.7 8.8

8.0 9.2

8.4 9.6

8.7 10.0

9.1 10.4

9.5 10.8

9.8 11.1

10.1 11.5

10.5 11.9

2.5 3.5 4.5 5.5

2.6 3.7 4.7 5.8

2.8 3.9 5.0 6.1

2.9 4.1 5.2 6.4

3.0 4.2 5.4 6.6

3.1 4.4 5.6 6.9

3.3 4.6 5.9 7.2

3.4 4.8 6.1 7.5

3.5 4.9 6.3 7.8

3.7 5.1 6.6 8.0

3.8 5.3 6.8 8.3

3.9 5.5 7.0 8.6

3.1 4.7 6.3

3.3 5.0 6.7

3.5 5.2 7.0

3.6 5.4 7.3

3.8 5.7 7.6

4.0 5.9 8.0

4.1 6.2 8.3

4.3 6.4 8.6

4.5 6.7 8.9

4.6 6.9 9.3

4.8 7.1 9.6

4.9 7.4 9.9

3.1 4.0 4.8 5.7 7.0 3.4

3.3 4.2 5.1 6.0 7.4 3.6

3.5 4.4 5.4 6.3 7.7 3.8

3.6 4.6 5.6 6.6 8.1 4.0

3.8 4.8 5.9 6.9 8.5 4.1

4.0 5.0 6.1 7.2 8.8 4.3

4.1 5.2 6.4 7.5 9.2 4.5

4.3 5.4 6.6 7.8 9.5 4.7

4.5 5.6 6.8 8.1 9.9 4.8

4.6 5.8 7.0 8.4 10.3 5.0

4.8 6.0 7.3 8.7 10.6 5.2

4.9 6.2 7.5 9.0 11.0 5.4

5.0 3.4 6.4

5.2 3.6 6.7

5.5 3.8 7.1

5.7 4.0 7.4

6.0 4.1 7.7

6.2 4.3 8.1

6.5 4.5 8.4

6.7 4.7 8.7

7.0 4.8 9.1

7.2 5.0 9.4

7.5 5.2 9.8

7.8 5.4 10.1

2.9 6.5

3.0 6.8

3.2 7.1

3.3 7.5

3.5 7.8

3.6 8.1

3.8 8.4

3.9 8.8

4.1 9.1

4.2 9.4

4.4 9.8

4.5 10.1

1.5 2.1 2.3 2.7 3.1 3.3 4.2 4.7 5.4 6.2 7.7 5.0 5.2 8.5

1.6 2.2 2.4 2.9 3.3 3.5 4.4 5.0 5.7 6.6 8.0 5.2 5.4 8.9

1.7 2.3 2.5 3.0 3.4 3.7 4.6 5.2 6.0 6.9 8.4 5.5 5.7 9.3

1.8 2.4 2.7 3.1 3.6 3.9 4.8 5.4 6.3 7.2 8.8 5.7 6.0 9.8

1.8 2.5 2.8 3.3 3.8 4.0 5.1 5.7 6.5 7.5 9.2 6.0 6.2 10.2

1.9 2.6 2.9 3.4 4.0 4.2 5.3 5.9 6.8 7.9 9.6 6.2 6.5 10.6

2.0 2.8 3.0 3.5 4.1 4.4 5.5 6.2 7.1 8.2 10.0 6.5 6.8 11.0

2.1 2.9 3.1 3.7 4.3 4.6 5.7 6.4 7.4 8.5 10.4 6.7 7.0 11.5

2.2 3.0 3.2 3.8 4.4 4.7 5.9 6.7 7.7 8.8 10.8 7.0 7.3 11.9

2.2 3.1 3.4 3.9 4.5 4.9 6.1 6.9 7.9 9.2 11.1 7.2 7.6 12.3

2.3 3.2 3.5 4.1 4.7 5.1 6.4 7.1 8.2 9.5 11.5 7.5 7.8 12.8

2.4 3.3 3.6 4.2 4.8 5.3 6.6 7.4 8.4 9.8 11.9 7.8 8.1 13.2

A P P E N D I X B Approximate Caloric Expenditure per Minute for Various Physical Activities

Body weight 73 160

75 165

77 170

80 175

82 180

84 185

86 190

89 195

91 200

93 205

95 210

98 215

100 220

10.5 9.6

10.9 9.9

11.2 10.2

11.5 10.5

11.9 10.8

12.2 11.1

12.5 11.4

12.9 11.7

13.2 12.0

13.5 12.3

13.8 12.6

14.2 12.9

14.5 13.2

10.8 12.3

11.2 12.7

11.5 13.1

11.8 13.5

12.2 13.9

12.5 14.3

12.9 14.7

13.2 15.0

13.5 15.4

13.9 15.8

14.2 16.2

14.6 16.6

14.9 17.0

4.0 5.6 7.3 8.9

4.2 5.8 7.5 9.2

4.3 6.0 7.7 9.4

4.4 6.2 7.9 9.7

4.5 6.4 8.2 10.0

4.7 6.5 8.4 10.3

4.8 6.7 8.6 10.6

4.9 6.9 8.9 10.8

5.1 7.1 9.1 11.1

5.2 7.2 9.3 11.4

5.3 7.4 9.5 11.7

5.4 7.6 9.8 12.0

5.6 7.8 10.0 12.2

5.1 7.6 10.2

5.3 7.9 10.5

5.4 8.1 10.9

5.6 8.3 11.2

5.7 8.6 11.5

5.9 8.8 11.9

6.0 9.1 12.2

6.2 9.3 12.5

6.4 9.5 12.8

6.5 9.8 13.1

6.7 10.0 13.5

6.9 10.3 13.8

7.0 10.5 14.1

5.1 6.4 7.8 9.3 11.3 5.5

5.3 6.6 8.0 9.5 11.7 5.7

5.4 6.8 8.3 9.8 12.0 5.9

5.6 7.0 8.5 10.1 12.4 6.1

5.7 7.2 8.8 10.4 12.8 6.3

5.9 7.4 9.0 10.7 13.1 6.4

6.0 7.6 9.2 11.0 13.5 6.6

6.2 7.8 9.4 11.3 13.8 6.8

6.4 8.0 9.7 11.6 14.2 7.0

6.5 8.2 9.9 11.9 14.5 7.1

6.7 8.4 10.2 12.2 14.9 7.3

6.9 8.6 10.4 12.5 15.2 7.5

7.0 8.8 10.7 12.8 15.6 7.7

8.0 5.5 10.4

8.3 5.7 10.8

8.5 5.9 11.1

8.8 6.1 11.4

9.0 6.3 11.8

9.3 6.4 12.1

9.5 6.6 12.4

9.8 6.8 12.8

10.0 7.0 13.1

10.3 7.1 13.4

10.6 7.3 13.7

10.8 7.5 14.1

11.1 7.7 14.4

4.7 10.4

4.8 10.7

5.0 11.1

5.1 11.4

5.3 11.7

5.4 12.0

5.6 12.4

5.7 12.7

5.9 13.0

6.0 13.4

6.1 13.7

6.3 14.0

6.4 14.4

2.4 3.4 3.7 4.4 5.0 5.4 6.8 7.6 8.7 10.1 12.3 8.0 8.3 13.6

2.5 3.5 3.8 4.5 5.2 5.6 7.0 7.9 9.0 10.4 12.7 8.3 8.6 14.1

2.6 3.6 4.0 4.6 5.3 5.8 7.2 8.1 9.2 10.8 13.1 8.5 8.9 14.5

2.7 3.7 4.1 4.8 5.5 6.0 7.4 8.3 9.5 11.1 13.5 8.8 9.1 14.9

2.8 3.9 4.2 4.9 5.6 6.2 7.6 8.6 9.8 11.4 13.9 9.0 9.4 15.4

2.9 4.0 4.3 5.0 5.8 6.3 7.9 8.8 10.1 11.8 14.3 9.3 9.7 15.8

2.9 4.1 4.4 5.2 5.9 6.5 8.1 9.1 10.4 12.1 14.7 9.5 9.9 16.2

3.0 4.2 4.5 5.3 6.1 6.7 8.3 9.3 10.6 12.4 15.0 9.8 10.2 16.6

3.1 4.3 4.7 5.4 6.3 6.9 8.5 9.5 10.9 12.7 15.4 10.0 10.5 17.1

3.2 4.4 4.8 5.6 6.4 7.0 8.7 9.8 11.2 13.0 15.8 10.3 10.7 17.5

3.2 4.5 4.9 5.7 6.6 7.2 8.9 10.0 11.5 13.4 16.2 10.6 11.0 17.9

3.3 4.6 5.0 5.9 6.8 7.4 9.1 10.3 11.8 13.7 16.6 10.8 11.2 18.4

3.4 4.7 5.1 6.0 6.9 7.6 9.4 10.5 12.0 14.0 17.0 11.1 11.5 18.8

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APPENDIX

C

Self-Test on Drinking Habits and Alcoholism

Problem drinking often has its seeds in the teen years. Significant health consequences of this practice typically arise in adulthood. The following questionnaire was developed by the National Council on Alcoholism. With this assessment, you can determine whether you or someone you know might need help.

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Yes

No

1. Do you occasionally drink heavily after disappointment, after a quarrel, or when someone gives you a hard time?

_____

_____

2. When you have trouble or feel under pressure, do you drink more heavily then usual?

_____

_____

3. Have your ever noticed that you’re able to handle liquor better than you did when you first started drinking?

_____

_____

4. Do you ever wake up the morning after you’ve been drinking and discover that you can’t remember part of the evening before, even though your friends tell you that you didn’t pass out?

_____

_____

5. When drinking with other people, do you try to have a few extra drinks when others won’t know it?

_____

_____

6. Are there certain occasions when you feel uncomfortable if alcohol isn’t available?

_____

_____

7. Have you recently noticed that when you begin drinking, you’re in more of a hurry to get the first drink than you used to be?

_____

_____

8. Do you sometimes feel a little guilty about your drinking?

_____

_____

9. Are you secretly irritated when your family or friends discuss your drinking?

_____

_____

10. Have you recently noticed an increase in the frequency of memory blackout?

_____

_____

11. Do you often find that you wish to continue drinking after your friends say they’ve had enough?

_____

_____

12. Do you usually have a reason for the occasions when you drink heavily?

_____

_____

13. When you’re sober, do you often regret things you have done or said while drinking

_____

_____

14. Have you tried switching brands or following different plans to control your drinking?

_____

_____

15. Have you often failed to keep promises you’ve made to yourself about controlling or stopping your drinking?

_____

_____

Yes

No

16. Have your ever tried to control your drinking by changing jobs or moving to a new location?

_____

_____

17. Do you try to avoid family or close friends while you’re drinking?

_____

_____

18. Are you having an increasing number of financial and work problems?

_____

_____

19. Do more people seem to be treating you unfairly without good reason?

_____

_____

20. Do you eat very little or irregularly when you’re drinking?

_____

_____

21. Do you sometimes have the shakes in the morning and find that it helps to have a little drink?

_____

_____

22. Have you recently noticed that you can drink more than you once did?

_____

_____

23. Do you sometimes stay drunk for several days at a time?

_____

_____

24. Do you sometimes feel very depressed and wonder whether life is worth living?

_____

_____

25. Sometimes after periods of drinking do you see or hear things that aren’t there?

_____

_____

26. Do you get terribly frightened after you have been drinking heavily?

_____

_____

Interpretation These are all symptoms that may indicate alcoholism. “Yes” answers to several of the questions indicate the following stages of alcoholism: Questions 1–8:

Potential drinking problem

Questions 9–21:

Drinking problem likely

Questions 22–26:

Definite drinking problem

It is vital that people assess themselves honestly. If you or someone you know demonstrates some or a number of these symptoms, it is important to seek help. If there is even a question in your mind, go talk to a professional about it. Reprinted courtesy of the National Council on Alcoholism and Drug Dependence.

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APPENDIX

D

Determination of Healthy Body Weight

There are a number of different techniques utilized to determine a healthy body weight. The following three methods offer you an estimate of an appropriate body weight. Method A is based on the Body Mass Index (BMI). Method B is based upon body-fat percentage. Method C, the waist circumference, does not determine a desirable body weight but provides an assessment of desirable body-fat distribution.

Method A The BMI uses the metric system, so you need to determine your weight in kilograms and your height in meters. The formula is Body weight in kilograms (Height in meters)2

Kilograms body weight = Desired BMI × (Height in meters)2

Dividing your body weight in pounds by 2.2 will give you your weight in kilograms. Multiplying your height in inches by 0.0254 will give you your height in meters.

Here’s a brief example for a woman who weighs 187 pounds and is 5′9″ tall; her BMI calculates to be 27.7, so her weight poses a health risk. If she wants to achieve a BMI of 23, she will need to reduce her weight to 155 pounds.

Your weight in kilograms =

Kilograms body weight = 23 × (1.753)2 = 70.6

(Your weight in pounds) = _____ 2.2

70.6 kg × 2.2 = 155 pounds To calculate your desired body weight:

Your height in meters =

Kilograms body weight =

(Your height in inches) × 0.0254 = _____

(Your desired BMI) × (Your height in meters)2

BMI =

Body weight in kilograms = _____ (Height in meters)2

Or you may use your weight in pounds and height in inches with the following formula: BMI =

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A BMI range of 18.5 to 25 is considered to be normal, but a suggested desirable range for females is 21.3 to 22.1 and for males is 21.9 to 22.4. Individuals with BMI values between 25.0–29.9 are classified as overweight, those from 30.0–39.9 are classified as obese, while those 40 and above are classified as extremely obese. The higher the BMI, the greater the health risks faced by the individual, particularly diabetes, high blood pressure, and heart disease. If you want to lower your body weight to a more desirable BMI, such as 22, use the following formula to determine what that weight should be; the weight is expressed in kilograms, so multiplying it by 2.2 will give you the desired weight in pounds.

Body weight in pounds × 705 (Height in inches)2

Kilograms body weight = _____ × _____ _____ kg × 2.2 = _____ pounds Keep in mind that the BMI does not discriminate between muscle mass and body fat, so a high BMI may reflect an increased muscle mass and body fat may actually be relatively low. Conversely, an individual with a low BMI may

TABLE D.1

Generalized equations for predicting body fat

Measure the appropriate skinfolds for women (triceps, thigh, and suprailium sites) or men (chest, abdomen, and thigh sites) as illustrated in figures D.1–D.4.You may use either the appropriate formula or the appropriate table in appendix D to obtain the predicted body-fat percentage. Women*

Men**

BD = 1.0994921 – 0.0009929 (X1) + 0.0000023 (X1)2 – 0.0001392 (X2)

BD = 1.10938 – 0.0008267 (X1) + 0.0000016 (X1)2 – 0.0002574 (X2)

BD = Body density

BD = Body density

X1 = Sum of triceps, thigh, and suprailium skinfolds

X1 = Sum of chest, abdomen, and thigh skinfolds

X2 = Age

X2 = Age To calculate percent body fat, plug into Siri’s equation. ⎛ 4.95 ⎞ − 4.5⎟ × 100 ⎜ ⎝ BD ⎠

*From Jackson, A., Pollock, M., and Ward, A. 1980. Generalized equations for predicting body density of women. Medicine & Science in Sports & Exercise 12:175–182. **Jackson, A., and Pollock, M. 1978. Generalized equations for predicting body density of men. British Journal of Nutrition 40:497–504.

Axillary line

Chest skinfold

Nipple

45°

Suprailiac skinfold at 45° angle

Iliac crest

Hip bone

Abdominal skinfold Umbilicus

Thigh bone

F I G U R E D . 1 The chest and abdomen skinfold. Chest— A diagonal fold is taken between the axilla and the nipple. Use a midway point. Abdomen—A vertical fold is taken about 2.5 centimeters (1 inch) to the side of the umbilicus.

F I G U R E D . 2 The suprailiac skinfold. A diagonal fold is taken at about a 45-degree angle just above the crest of the ilium.

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Point of hip bone (anterior iliac spine) Right scapula Left scapula Inferior angle of scapula Thigh skinfold

Subscapular skinfold at 45° angle to spine

Thigh

45° Triceps skinfold Kneecap (patella)

F I G U R E D . 3 The thigh skinfold. A vertical fold is taken on the front of the thigh midway between the anterior iliac spine and the patella.

have a higher level of body fat if muscle mass is small. The BMI also does not account for regional fat distribution.

F I G U R E D . 4 The triceps and subscapular skinfolds. In the triceps skinfold, a vertical fold is taken over the triceps muscle one-half the distance from the acromion process to the olecranon process at the elbow. The subscapular skinfold is taken just below the lower angle of the scapula, at about a 45-degree angle to the spinal column.

need to reach a body weight of 187.5 to achieve this first goal.

Method B For this method, you will need to know your body-fat percentage as determined by the procedure described in table D.1 or another appropriate technique. You will also need to determine the body-fat percentage you desire to have. You may use table 10.2 on page 411 as a guideline. You will need to do the following calculations for the formula:

Desired body weight =

150 150 = = 187.5 1.00 – 0.20 0.8

Your current body weight _____ Your current percent body fat _____ Your pounds of body fat _____ Your LBW _____

1. Determine your current lean body weight (LBW). Multiply your current body weight in pounds by your current percent body fat expressed as a decimal (20 percent would be 0.20) to obtain your pounds of body fat. Subtract your pounds of body fat from your current weight to give you your lean body weight (LBW). 2. Determine your desired body-fat percentage and express it as a decimal. Desired body weight =

LBW 1.00 – Desired % body fat

As an example, suppose we have a 200-pound male who is currently at 25 percent body fat but desires to get down to 20 percent as his first goal. Multiplying his current weight by his current percent body fat yields 50 pounds of body fat (200 × 0.25 = 50); subtracting this from his current weight yields a LBW of 150 (200 – 50). If we plug his desired percent of 20 into the formula, he will 576

A P P E N D I X D Determination of Healthy Body Weight

Your desired percent body fat _____ Desired body weight

LBW = _____ = _____ 1.00 – ?

Method C The waist circumference is a measure of regional fat distribution. Using a flexible (preferably metal) tape, measure the narrowest section of the bare waist as seen from the front while standing. Wear tight clothing. Do not compress skin and fat with pressure from the tape. The waist measurement may be used as a simple screening technique for abdominal obesity. Females with a waist of 35 inches or over, and men with a waist of 40 inches or over may be at increased risk. Waist girth _____ In the following table, use both your BMI and waist measurement to evaluate your risk of associated disease.

Risk of associated disease according to BMI and waist size Waist less than or equal to 40 in. (men) or 35 in. (women)

BMI 18.5 or less 18.5 – 24.9 25.0 – 29.9 30.0 – 34.9 35.0 – 39.9 40 or greater

Underweight Normal Overweight Obese Obese Extremely obese

Waist greater than 40 in. (men) or 35 in. (women)

— — Increased High Very high Extremely high

N/A N/A High Very high Very high Extremely high

Note: Recent research suggests waist sizes greater than 37 inches in men and 31.5 inches in women may increase health risks when accompanied by other conditions, such as high blood pressure. Source: www.consumer.gov/weightloss.bmi.htm

Percent fat estimate for men: sum of chest, abdomen, and thigh skinfolds Sum of skinfolds (mm) 8–10 11–13 14–16 17–19 20–22 23–25 26–28 29–31 32–34 35–37 38–40 41–43 44–46 47–49 50–52 53–55 56–58 59–61 62–64 65–67 68–70 71–73 74–76 77–79 80–82 83–85 86–88 89–91 92–94 95–97 98–100 101–103 104–106 107–109 110–112 113–115 116–118 119–121 122–124 125–127

Under 22

23–27

28–32

33–37

1.3 2.2 3.2 4.2 5.1 6.1 7.0 8.0 8.9 9.8 10.7 11.6 12.5 13.4 14.3 15.1 16.0 16.9 17.6 18.5 19.3 20.1 20.9 21.7 22.4 23.2 24.0 24.7 25.4 26.1 26.9 27.5 28.2 28.9 29.6 30.2 30.9 31.5 32.1 32.7

1.8 2.8 3.8 4.7 5.7 6.6 7.6 8.5 9.4 10.4 11.3 12.2 13.1 13.9 14.8 15.7 16.5 17.4 18.2 19.0 19.9 20.7 21.5 22.2 23.0 23.8 24.5 25.3 26.0 26.7 27.4 28.1 28.8 29.5 30.2 30.8 31.5 32.1 32.7 33.3

2.3 3.3 4.3 5.3 6.2 7.2 8.1 9.1 10.0 10.9 11.8 12.7 13.6 14.5 15.4 16.2 17.1 17.9 18.8 19.6 20.4 21.2 22.0 22.8 23.6 24.4 25.1 25.9 26.6 27.3 28.0 28.7 29.4 30.1 30.8 31.4 32.1 32.7 33.3 33.9

2.9 3.9 4.8 5.8 6.8 7.7 8.7 9.6 10.5 11.5 12.4 13.3 14.2 15.1 15.9 16.8 17.7 18.5 19.4 20.2 21.0 21.8 22.6 23.4 24.2 25.0 25.7 26.5 27.2 27.9 28.6 29.3 30.0 30.7 31.4 32.0 32.7 33.3 33.9 34.5

Age to last year 38–42 43–47 3.4 4.4 5.4 6.3 7.3 8.3 9.2 10.2 11.1 12.0 12.9 13.8 14.7 15.6 16.5 17.4 18.2 19.1 19.9 20.8 21.6 22.4 23.2 24.0 24.8 25.5 26.3 27.1 27.8 28.5 29.2 29.9 30.6 31.3 32.0 32.6 33.3 33.9 34.5 35.1

3.9 4.9 5.9 6.9 7.9 8.8 9.8 10.7 11.6 12.6 13.5 14.4 15.3 16.2 17.1 17.9 18.8 19.7 20.5 21.3 22.2 23.0 23.8 24.6 25.4 26.1 26.9 27.6 28.4 29.1 29.8 30.5 31.2 31.9 32.6 33.2 33.9 34.5 35.1 35.8

48–52

53–57

Over 57

4.5 5.5 6.4 7.4 8.4 9.4 10.3 11.3 12.2 13.1 14.1 15.0 15.9 16.8 17.6 18.5 19.4 20.2 21.1 21.9 22.7 23.6 24.4 25.2 25.9 26.7 27.5 28.2 29.0 29.7 30.4 31.1 31.8 32.5 33.2 33.8 34.5 35.1 35.8 36.4

5.0 6.0 7.0 8.0 8.9 9.9 10.9 11.8 12.8 13.7 14.6 15.5 16.4 17.3 18.2 19.1 20.0 20.8 21.7 22.5 23.3 24.1 25.0 25.8 26.5 27.3 28.1 28.8 29.6 30.3 31.0 31.7 32.4 33.1 33.8 34.5 35.1 35.7 36.4 37.0

5.5 6.5 7.5 8.5 9.5 10.5 11.4 12.4 13.3 14.3 15.2 16.1 17.0 17.9 18.8 19.7 20.5 21.4 22.2 23.1 23.9 24.7 25.5 26.3 27.1 27.9 28.7 29.4 30.2 30.9 31.6 32.3 33.0 33.7 34.4 35.1 35.7 36.4 37.0 37.6

From A. S. Jackson and M. L. Pollock, “Practical Assessment of Body Composition,” May 1985, in Physician and Sportsmedicine. Reprinted with permission of McGraw-Hill, Inc.

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Percent fat estimate for women: sum of triceps, suprailium, and thigh skinfolds Sum of skinfolds (mm) 23–25 26–28 29–31 32–34 35–37 38–40 41–43 44–46 47–49 50–52 53–55 56–58 59–61 62–64 65–67 68–70 71–73 74–76 77–79 80–82 83–85 86–88 89–91 92–94 95–97 98–100 101–103 104–106 107–109 110–112 113–115 116–118 119–121 122–124 125–127 128–130

Under 22

23–27

28–32

33–37

9.7 11.0 12.3 13.6 14.8 16.0 17.2 18.3 19.5 20.6 21.7 22.7 23.7 24.7 25.7 26.6 27.5 28.4 29.3 30.1 30.9 31.7 32.5 33.2 33.9 34.6 35.3 35.8 36.4 37.0 37.5 38.0 38.5 39.0 39.4 39.8

9.9 11.2 12.5 13.8 15.0 16.3 17.4 18.6 19.7 20.8 21.9 23.0 24.0 25.0 25.9 26.9 27.8 28.7 29.5 30.4 31.2 32.0 32.7 33.4 34.1 34.8 35.4 36.1 36.7 37.2 37.8 38.3 38.7 39.2 39.6 40.0

10.2 11.5 12.8 14.0 15.3 16.5 17.7 18.8 20.0 21.1 22.1 23.2 24.2 25.2 26.2 27.1 28.0 28.9 29.8 30.6 31.4 32.2 33.0 33.7 34.4 35.1 35.7 36.3 36.9 37.5 38.0 38.5 39.0 39.4 39.9 40.3

10.4 11.7 13.0 14.3 15.5 16.7 17.9 19.1 20.2 21.3 22.4 23.4 24.5 25.5 26.4 27.4 28.3 29.2 30.0 30.9 31.7 32.5 33.2 33.9 34.6 35.3 35.9 36.6 37.1 37.7 38.2 38.8 39.2 39.7 40.1 40.5

Age to last year 38–42 43–47 10.7 12.0 13.3 14.5 15.8 17.0 18.2 19.3 20.5 21.6 22.6 23.7 24.7 25.7 26.7 27.6 28.5 29.4 30.3 31.1 31.9 32.7 33.5 34.2 34.9 35.5 36.2 36.8 37.4 38.0 38.5 39.0 39.5 39.9 40.4 40.8

10.9 12.3 13.5 14.8 16.0 17.2 18.4 19.6 20.7 21.8 22.9 23.9 25.0 26.0 26.9 27.9 28.8 29.7 30.5 31.4 32.2 32.9 33.7 34.4 35.1 35.8 36.4 37.1 37.6 38.2 38.7 39.3 39.7 40.2 40.6 41.0

48–52

53–57

Over 57

11.2 12.5 13.8 15.0 16.3 17.5 18.7 19.8 21.0 22.1 23.1 24.2 25.2 26.2 27.2 28.1 29.0 29.9 30.8 31.6 32.4 33.2 33.9 34.7 35.4 36.0 36.7 37.3 37.9 38.5 39.0 39.5 40.0 40.4 40.9 41.3

11.4 12.7 14.0 15.3 16.5 17.7 18.9 20.1 21.2 22.3 23.4 24.4 25.5 26.4 27.4 28.4 29.3 30.2 31.0 31.9 32.7 33.4 34.2 34.9 35.6 36.3 36.9 37.5 38.1 38.7 39.2 39.7 40.2 40.7 41.1 41.5

11.7 13.0 14.3 15.5 16.8 18.0 19.2 20.3 21.5 22.6 23.6 24.7 25.7 26.7 27.7 28.6 29.5 30.4 31.3 32.1 32.9 33.7 34.4 35.2 35.9 36.5 37.2 37.8 38.4 38.9 39.5 40.0 40.5 40.9 41.4 41.8

From A. S. Jackson and M. L. Pollock, “Practical Assessment of Body Composition,” May 1985, in Physician and Sportsmedicine. Reprinted with permission of McGraw-Hill, Inc.

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A P P E N D I X D Determination of Healthy Body Weight

APPENDIX

E

Exchange Lists for Meal Planning*

What Are Exchange Lists?

Exchange Lists

Exchange lists are foods listed together because they are alike. Each serving of a food has about the same amount of carbohydrate, protein, fat, and Calories as the other foods on that list. That is why any food on a list can be “exchanged” or traded for any other food on the same list. For example, you can trade the slice of bread you might eat for breakfast for one-half cup of cooked cereal. Each of these foods equals one starch choice.

Foods are listed with their serving sizes, which are usually measured after cooking. When you begin, you should measure the size of each serving. This may help you learn to “eyeball” correct serving sizes. The following chart shows the amount of nutrients in one serving from each list. The exchange lists provide you with a lot of food choices (foods from the basic food groups, foods with added sugars,

Carbohydrate (grams)

Protein (grams)

Fat (grams)

15 15

3 —

1 or less —

80 60

12 12 12 15 5

8 8 8 varies 2

0–3 5 8 varies —

90 120 150 varies 25

Very lean Lean Medium-fat High-fat

— — — —

7 7 7 7

0–1 3 5 8

35 55 75 100

Fat group





5

45

Groups/Lists

Calories

Carbohydrate group Starch Fruit Milk Skim Low-fat Whole Other carbohydrates Vegetables Meat and meat substitutes group

*The Exchange Lists are the basis of a meal planning system designed by a committee of the American Diabetes Association and the American Dietetic Association. While designed primarily for people with diabetes and others who must follow special diets, the Exchange Lists are based on principles of good nutrition that apply to everyone. © 1995 American Diabetes Association, Inc., American Dietetic Association.

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free foods, combination foods, and fast foods). This gives you variety in your meals. Several foods, such as dried beans and peas, bacon, and peanut butter, are on two lists. This gives you flexibility in putting your meals together. Whenever you choose new foods or vary your meal plan, monitor your blood glucose to see how these different foods affect your blood glucose level. Most foods in the Carbohydrate group have about the same amount of carbohydrate per serving. You can exchange starch, fruit, or milk choices in your meal plan. Vegetables are in this group but contain only about 5 grams of carbohydrate.

A Word about Food Labels Exchange information is based on foods found in grocery stores. However, food companies often change the ingredients in their products. That is why you need to check the Nutrition Facts panel of the food label. The Nutrition Facts tell you the number of Calories and grams of carbohydrate, protein, and fat in one serving. Compare these numbers with the exchange information in this appendix to see how many exchanges you will be eating. In this way, food labels can help you add foods to your meal plans. Ask your dietitian to help you use food label information to plan your meals, or read pages 60–65 for more tips on how to use food labels.

Getting Started! See your dietitian regularly when you are first learning how to use your meal plan and the exchange lists. Your meal plan can be adjusted to fit changes in your lifestyle, such as work, school, vacation, or travel. Regular nutrition counseling can help you make positive changes in your eating habits. Careful eating habits will help you feel better and be healthier, too. Best wishes and good eating with Exchange Lists for Meal Planning.

Starch List Cereals, grains, pasta, breads, crackers, snacks, starchy vegetables, and cooked dried beans, peas, and lentils are starches. In general, one starch is: • 1/2 cup of cereal, grain, pasta, or starchy vegetable • 1 ounce of a bread product, such as 1 slice of bread • 3/4 to 1 ounce of most snack foods. (Some snack foods may also have added fat.)

Nutrition tips 1. Most starch choices are good sources of B vitamins. 2. Foods made from whole grains are good sources of fiber. 3. Dried beans and peas are a good source of protein and fiber. 580

A P P E N D I X E Exchange Lists for Meal Planning

Selection tips 1. Choose starches made with little fat as often as you can. 2. Starchy vegetables prepared with fat count as one starch and one fat. 3. Bagels or muffins can be 2, 3, or 4 ounces in size, and can, therefore, count as 2, 3, or 4 starch choices. Check the size you eat. 4. Dried beans, peas, and lentils are also found on the Meat and Meat Substitutes list. 5. Regular potato chips and tortilla chips are found on the Other Carbohydrates list. 6. Most of the serving sizes are measured after cooking. 7. Always check Nutrition Facts on the food label. One starch exchange equals 15 grams carbohydrate, 3 grams protein, 0–1 grams fat, and 80 Calories.

Bread Bagel . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 (1 oz) Bread, reduced-calorie . . . . . . . . . . . . . 2 slices (1 1/2 oz) Bread, white, whole wheat, pumpernickel, rye . . . . . . . . . . . . . . . . . . 1 slice (1 oz) Bread sticks, crisp, 4 in. long × 1/2 in. . . . . . . . 2 (2/3 oz) English muffin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 Hot dog or hamburger bun . . . . . . . . . . . . . . . . 1/2 (1 oz) Pita, 6 in. across. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 Raisin bread, unfrosted . . . . . . . . . . . . . . . . 1 slice (1 oz) Roll, plain, small . . . . . . . . . . . . . . . . . . . . . . . . . 1 (1 oz) Tortilla, corn, 6 in. across . . . . . . . . . . . . . . . . . . . . . . . . 1 Tortilla, flour, 7–8 in. across. . . . . . . . . . . . . . . . . . . . . . 1 Waffle, 4 1/2 in. square, reduced-fat. . . . . . . . . . . . . . . . 1

Cereals and grains Bran cereals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Bulgur. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Cereals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Cereals, unsweetened, ready-to-eat . . . . . . . . . . . 3/4 cup Cornmeal (dry) . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Tbsp Couscous . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/3 cup Flour (dry) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Tbsp Granola, low-fat . . . . . . . . . . . . . . . . . . . . . . . . . . 1/4 cup Grape-Nuts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/4 cup Grits . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Kasha . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Millet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/4 cup Muesli. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/4 cup Oats. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Pasta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Puffed cereal . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1/2 cups Rice milk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Rice, white or brown . . . . . . . . . . . . . . . . . . . . . . 1/3 cup

Shredded Wheat . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Sugar-frosted cereal . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Wheat germ . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Tbsp

Starchy vegetables Baked beans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/3 cup Corn . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Corn on cob, medium. . . . . . . . . . . . . . . . . . . . . . 1 (5 oz) Mixed vegetables with corn, peas, or pasta . . . . . . . 1 cup Peas, green . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Plantain. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Potato, baked or boiled . . . . . . . . . . . . . . . . 1 small (3 oz) Potato, mashed . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Squash, winter (acorn, butternut). . . . . . . . . . . . . . . 1 cup Yam, sweet potato, plain. . . . . . . . . . . . . . . . . . . . 1/2 cup

Crackers and snacks Animal crackers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Graham crackers, 2 1/2 in. square . . . . . . . . . . . . . . . . . 3 Matzoh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3/4 oz Melba toast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 slices Oyster crackers. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24 Popcorn (popped, no fat added or low-fat microwave) . . . . . . . . . . . . . . . . . . . . 3 cups Pretzels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3/4 oz Rice cakes, 4 in. across. . . . . . . . . . . . . . . . . . . . . . . . . . 2 Saltine-type crackers . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 Snack chips, fat-free (tortilla, potato) . . . . 15–20 (3/4 oz) Whole wheat crackers, no fat added . . . . . . . 2–5 (3/4 oz)

Dried beans, peas, and lentils (Count as 1 starch exchange, plus 1 very lean meat exchange.) Beans and peas (garbanzo, pinto, kidney, white, split, black-eyed) . . . . . . . . . . . . 1/2 cup Lentils. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Lima beans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2/3 cup Miso . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Tbsp = 400 mg or more of sodium per serving.

Starchy foods prepared with fat (Count as 1 starch exchange, plus 1 fat exchange.) Biscuit, 2 1/2 in. across. . . . . . . . . . . . . . . . . . . . . . . . . . 1 Chow mein noodles . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Corn bread, 2 in. cube . . . . . . . . . . . . . . . . . . . . . 1 (2 oz) Crackers, round butter type . . . . . . . . . . . . . . . . . . . . . . 6 Croutons . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 cup French-fried potatoes . . . . . . . . . . . . . . . . . . 16–25 (3 oz) Granola . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/4 cup Muffin, small . . . . . . . . . . . . . . . . . . . . . . . . . 1 (1 1/2 oz) Pancake, 4 in. across. . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Popcorn, microwave . . . . . . . . . . . . . . . . . . . . . . . 3 cups

Sandwich crackers, cheese or peanut butter filling . . . . 3 Stuffing, bread (prepared). . . . . . . . . . . . . . . . . . . 1/3 cup Taco shell, 6 in. across . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Waffle, 4 1/2 in. square. . . . . . . . . . . . . . . . . . . . . . . . . . 1 Whole wheat crackers, fat added . . . . . . . . . . . 4–6 (1 oz) Some food you buy uncooked will weigh less after you cook it. Starches often swell in cooking so a small amount of uncooked starch will become a much larger amount of cooked food. The following table shows some of the changes. Food (starch group)

Uncooked

Cooked

Oatmeal Cream of Wheat Grits Rice Spaghetti Noodles Macaroni Dried beans Dried peas Lentils

3 Tbsp 2 Tbsp 3 Tbsp 2 Tbsp 1/4 cup 1/3 cup 1/4 cup 1/4 cup 1/4 cup 3 Tbsp

1/2 cup 1/2 cup 1/2 cup 1/3 cup 1/2 cup 1/2 cup 1/2 cup 1/2 cup 1/2 cup 1/2 cup

Common measurements 3 tsp = 1 Tbsp 4 Tbsp = 1/4 cup 5 1/3 Tbsp = 1/3 cup

4 ounces = 1/2 cup 8 ounces = 1 cup 1 cup = 1/2 pint

Fruit List Fresh, frozen, canned, and dried fruits and fruit juices are on this list. In general, one fruit exchange is: • 1 small to medium fresh fruit • 1/2 cup of canned or fresh fruit or fruit juice • 1/4 cup of dried fruit

Nutrition tips 1. Fresh, frozen, and dried fruits have about 2 grams of fiber per choice. Fruit juices contain very little fiber. 2. Citrus fruits, berries, and melons are good sources of vitamin C.

Selection tips 1. Count 1/2 cup cranberries or rhubarb sweetened with sugar substitutes as free foods. 2. Read the Nutrition Facts on the food label. If one serving has more than 15 grams of carbohydrate, you will need to adjust the size of the serving you eat or drink. 3. Portion sizes for canned fruits are for the fruit and a small amount of juice. 4. Whole fruit is more filling than fruit juice and may be a better choice. www.mhhe.com/williams9

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5. Food labels for fruits may contain the words “no sugar added” or “unsweetened.” This means that no sucrose (table sugar) has been added. 6. Generally, fruit canned in extra light syrup has the same amount of carbohydrate per serving as the “no sugar added” or the juice pack. All canned fruits on the fruit list are based on one of these three types of pack. One fruit exchange equals 15 grams carbohydrate and 60 Calories.

Fruit juice Apple juice/cider . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Cranberry juice cocktail . . . . . . . . . . . . . . . . . . . . 1/3 cup Cranberry juice cocktail, reduced-calorie . . . . . . . . 1 cup Fruit juice blends, 100% juice . . . . . . . . . . . . . . . 1/3 cup Grape juice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/3 cup Grapefruit juice. . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Orange juice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Pineapple juice . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Prune juice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/3 cup

The weight includes skin, core, seeds, and rind.

Milk List Fruit Apple, unpeeled, small. . . . . . . . . . . . . . . . . . . . . 1 (4 oz) Applesauce, unsweetened. . . . . . . . . . . . . . . . . . . 1/2 cup Apples, dried . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 rings Apricots, canned . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Apricots, dried. . . . . . . . . . . . . . . . . . . . . . . . . . . 8 halves Apricots, fresh . . . . . . . . . . . . . . . . . . . 4 whole (5 1/2 oz) Banana, small . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 (4 oz) Blackberries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3/4 cup Blueberries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3/4 cup Cantaloupe, small . . . . . 1/3 melon (11 oz) or 1 cup cubes Cherries, sweet, fresh . . . . . . . . . . . . . . . . . . . . . 12 (3 oz) Cherries, sweet, canned . . . . . . . . . . . . . . . . . . . . 1/2 cup Dates. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Figs, dried. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 1/2 Figs, fresh. . . . . . . . . . 1 1/2 large or 2 medium (3 1/2 oz) Fruit cocktail. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Grapefruit, large . . . . . . . . . . . . . . . . . . . . . . . 1/2 (11 oz) Grapefruit sections, canned . . . . . . . . . . . . . . . . . 3/4 cup Grapes, small . . . . . . . . . . . . . . . . . . . . . . . . . . . 17 (3 oz) Honeydew melon . . . . . . . . 1 slice (10 oz) or 1 cup cubes Kiwi . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 (3 1/2 oz) Mandarin oranges, canned . . . . . . . . . . . . . . . . . . 3/4 cup Mango, small . . . . . . . . . . . 1/2 fruit (5 1/2 oz) or 1/2 cup Nectarine, small . . . . . . . . . . . . . . . . . . . . . . . . . . 1 (5 oz) Orange, small . . . . . . . . . . . . . . . . . . . . . . . . . 1 (6 1/2 oz) Papaya . . . . . . . . . . . . . . . . 1/2 fruit (8 oz) or 1 cup cubes Peach, medium, fresh . . . . . . . . . . . . . . . . . . . . . . 1 (6 oz) Peaches, canned . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Pear, large, fresh . . . . . . . . . . . . . . . . . . . . . . . . 1/2 (4 oz) Pears, canned . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Pineapple, canned . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Pineapple, fresh . . . . . . . . . . . . . . . . . . . . . . . . . . 3/4 cup Plums, canned. . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup Plums, small. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 (5 oz) Prunes, dried. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Raisins . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Tbsp Raspberries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 cup Strawberries . . . . . . . . . . . . . . . . 1 1/4 cup whole berries Tangerines, small . . . . . . . . . . . . . . . . . . . . . . . . . 2 (8 oz) Watermelon . . . . . . 1 slice (13 1/2 oz) or 1 1/4 cup cubes

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Different types of milk and milk products are on this list. Cheeses are on the Meat list and cream and other dairy fats are on the Fat list. Based on the amount of fat they contain, milks are divided into skim/very low-fat milk, low-fat milk, and whole milk. One choice of these includes: Carbohydrate (grams)

Protein (grams)

Fat (grams)

Calories

12 12 12

8 8 8

0–3 5 8

90 120 150

Skim/very low-fat Low-fat Whole

Nutrition tips 1. Milk and yogurt are good sources of calcium and protein. Check the food label. 2. The higher the fat content of milk and yogurt, the greater the amount of saturated fat and cholesterol. Choose lower-fat varieties. 3. For those who are lactose intolerant, look for lactosereduced or lactose-free varieties of milk.

Selection tips 1. One cup equals 8 fluid ounces or 1/2 pint. 2. Look for chocolate milk, frozen yogurt, and ice cream on the Other Carbohydrates list. 3. Nondairy creamers are on the Free Foods list. 4. Look for rice milk on the Starch list. 5. Look for soy milk on the Medium-fat Meat list. One milk exchange equals 12 grams carbohydrate and 8 grams protein.

Skim and very low-fat milk (0–3 grams fat per serving) Skim milk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 cup 1/2% milk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 cup 1% milk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 cup

Nonfat or low-fat buttermilk . . . . . . . . . . . . . . . . . . 1 cup Evaporated skim milk. . . . . . . . . . . . . . . . . . . . . . 1/2 cup Nonfat dry milk . . . . . . . . . . . . . . . . . . . . . . . 1/3 cup dry Plain nonfat yogurt . . . . . . . . . . . . . . . . . . . . . . . . 3/4 cup Nonfat or low-fat fruit-flavored yogurt sweetened with aspartame or with a nonnutritive sweetener. . . 1 cup

Nutrition tips 1. These foods can be substituted in your meal plan, even though they contain added sugars or fat. However, they do not contain as many important vitamins and minerals as the choices on the Starch, Fruit, or Milk list. 2. When planning to include these foods in your meal, be sure to include foods from all the lists to eat a balanced meal.

Low-fat (5 grams fat per serving) 2% milk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 cup Plain low-fat yogurt . . . . . . . . . . . . . . . . . . . . . . . 3/4 cup Sweet acidophilus milk . . . . . . . . . . . . . . . . . . . . . . 1 cup

Whole milk (8 grams fat per serving) Whole milk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 cup Evaporated whole milk. . . . . . . . . . . . . . . . . . . . . 1/2 cup Goat’s milk . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 cup Kefir. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 cup

Other Carbohydrates List

Selection tips 1. Because many of these foods are concentrated sources of carbohydrate and fat, the portion sizes are often very small. 2. Always check Nutrition Facts on the food label. It will be your most accurate source of information. 3. Many fat-free or reduced-fat products made with fat replacers contain carbohydrate. When eaten in large amounts, they may need to be counted. Talk with your dietitian to determine how to count these in your meal plan. 4. Look for fat-free salad dressings in smaller amounts on the Free Foods list.

You can substitute food choices from this list for a starch, fruit, or milk choice on your meal plan. Some choices will also count as one or more fat choices.

Food

One exchange equals 15 grams carbohydrate, or 1 starch, or 1 fruit, or 1 milk.

Serving size

Exchanges per serving

Angel food cake, unfrosted . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/12th cake . . . . . . . . . . . . . . . . . . 2 carbohydrates Brownie, small, unfrosted . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 in. square . . . . . . . . . . . . . . . . . . 1 carbohydrate, 1 fat Cake, frosted . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 in. square . . . . . . . . . . . . . . . . . . 2 carbohydrates, 1 fat Cake, unfrosted . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 in. square . . . . . . . . . . . . . . . . . . 1 carbohydrate, 1 fat Cookie, fat-free . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 small . . . . . . . . . . . . . . . . . . . . . 1 carbohydrate Cookie or sandwich cookie with creme filling . . . . . . . . . . . . 2 small . . . . . . . . . . . . . . . . . . . . . 1 carbohydrate, 1 fat Cranberry sauce, jellied . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/4 cup . . . . . . . . . . . . . . . . . . . . . 2 carbohydrates Cupcake, frosted . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 small . . . . . . . . . . . . . . . . . . . . . 2 carbohydrates, 1 fat Doughnut, glazed. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 3/4 in. across (2 oz) . . . . . . . . . . 2 carbohydrates, 2 fats Doughnut, plain cake. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 medium (1 1/2 oz) . . . . . . . . . . . 1 1/2 carbohydrates, 2 fats Fruit juice bars, frozen, 100% juice. . . . . . . . . . . . . . . . . . . . . 1 bar (3 oz) . . . . . . . . . . . . . . . . . . 1 carbohydrate Fruit snacks, chewy (pureed fruit concentrate) . . . . . . . . . . . . 1 roll (3/4 oz) . . . . . . . . . . . . . . . . 1 carbohydrate Fruit spreads, 100% fruit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Tbsp. . . . . . . . . . . . . . . . . . . . . . 1 carbohydrate Gelatin, regular . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup . . . . . . . . . . . . . . . . . . . . . 1 carbohydrate Gingersnaps . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 . . . . . . . . . . . . . . . . . . . . . . . . . . 1 carbohydrate Granola bar . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 bar . . . . . . . . . . . . . . . . . . . . . . . 1 carbohydrate, 1 fat Granola bar, fat-free. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 bar . . . . . . . . . . . . . . . . . . . . . . . 2 carbohydrates Hummus . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/3 cup . . . . . . . . . . . . . . . . . . . . . 1 carbohydrate, 1 fat Ice cream . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup . . . . . . . . . . . . . . . . . . . . . 1 carbohydrate, 2 fats Ice cream, light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup . . . . . . . . . . . . . . . . . . . . . 1 carbohydrate, 1 fat Ice cream, fat-free, no sugar added . . . . . . . . . . . . . . . . . . . . . 1/2 cup . . . . . . . . . . . . . . . . . . . . . 1 carbohydrate Jam or jelly, regular . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Tbsp. . . . . . . . . . . . . . . . . . . . . . 1 carbohydrate Milk, chocolate, whole . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 cup . . . . . . . . . . . . . . . . . . . . . . . 2 carbohydrates, 1 fat Pie, fruit, 2 crusts. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/6 pie. . . . . . . . . . . . . . . . . . . . . . 3 carbohydrates, 2 fats Pie, pumpkin or custard . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/8 pie. . . . . . . . . . . . . . . . . . . . . . 1 carbohydrate, 2 fats Potato chips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12–18 (1 oz) . . . . . . . . . . . . . . . . . 1 carbohydrate, 2 fats

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Food

Serving size

Exchanges per serving

Pudding, regular (made with low-fat milk) . . . . . . . . . . . . . . . 1/2 cup . . . . . . . . . . . . . . . . . . . . . 2 carbohydrates Pudding, sugar-free (made with low-fat milk). . . . . . . . . . . . . 1/2 cup . . . . . . . . . . . . . . . . . . . . . 1 carbohydrate Salad dressing, fat free . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/4 cup . . . . . . . . . . . . . . . . . . . . . 1 carbohydrate Sherbet, sorbet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/2 cup . . . . . . . . . . . . . . . . . . . . . 2 carbohydrates Spaghetti or pasta sauce, canned . . . . . . . . . . . . . . . . . . . . . 1/2 cup . . . . . . . . . . . . . . . . . . . . . 1 carbohydrate, 1 fat Sweet roll or Danish . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 (2 1/2 oz) . . . . . . . . . . . . . . . . . . 2 1/2 carbohydrates, 2 fats Syrup, light . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Tbsp. . . . . . . . . . . . . . . . . . . . . . 1 carbohydrate Syrup, regular . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Tbsp. . . . . . . . . . . . . . . . . . . . . . 1 carbohydrate Syrup, regular . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/4 cup . . . . . . . . . . . . . . . . . . . . . 4 carbohydrates Tortilla chips . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6–12 (1 oz) . . . . . . . . . . . . . . . . . . 1 carbohydrate, 2 fats Vanilla wafers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5 . . . . . . . . . . . . . . . . . . . . . . . . . . 1 carbohydrate, 1 fat Yogurt, frozen, fat-free, no sugar added . . . . . . . . . . . . . . . . . 1/2 cup . . . . . . . . . . . . . . . . . . . . . 1 carbohydrate Yogurt, frozen, low-fat, fat-free. . . . . . . . . . . . . . . . . . . . . . . . 1/3 cup . . . . . . . . . . . . . . . . . . . . . 1 carbohydrate, 0–1 fat Yogurt, low-fat with fruit. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 cup . . . . . . . . . . . . . . . . . . . . . . . 3 carbohydrates, 0–1 fat = 400 mg or more sodium per exchange.

Vegetable List Vegetables that contain small amounts of carbohydrates and Calories are on this list. Vegetables contain important nutrients. Try to eat at least 2 or 3 vegetable choices each day. In general, one vegetable exchange is: • 1/2 cup of cooked vegetables or vegetable juice • 1 cup of raw vegetables If you eat 1 to 2 vegetable choices at a meal or snack, you do not have to count the Calories or carbohydrates because they contain small amounts of these nutrients.

Nutrition tips 1. Fresh and frozen vegetables have less added salt than canned vegetables. Drain and rinse canned vegetables if you want to remove some salt. 2. Choose more dark green and dark yellow vegetables, such as spinach, broccoli, romaine, carrots, chilies, and peppers. 3. Broccoli, brussels sprouts, cauliflower, greens, peppers, spinach, and tomatoes are good sources of vitamin C. 4. Vegetables contain 1 to 4 grams of fiber per serving.

Selection tips 1. A 1-cup portion of broccoli is a portion about the size of a light bulb. 2. Tomato sauce is different from spaghetti sauce, which is on the Other Carbohydrates list. 3. Canned vegetables and juices are available without added salt. 4. If you eat more than 4 cups of raw vegetables or 2 cups of cooked vegetables at one meal, count them as 1 carbohydrate choice.

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5. Starchy vegetables such as corn, peas, winter squash, and potatoes that contain larger amounts of Calories and carbohydrates are on the Starch list. One vegetable exchange equals 5 grams carbohydrate, 2 grams protein, 0 grams fat, and 25 Calories. Artichoke Artichoke hearts Asparagus Beans (green, wax, Italian) Bean sprouts Beets Broccoli Brussels sprouts Cabbage Carrots Cauliflower Celery Cucumber Eggplant Green onions or scallions Greens (collard, kale, mustard, turnip) Kohlrabi Leeks Mixed vegetables (without corn, peas, or pasta) Mushrooms Okra Onions Pea pods Peppers (all varieties) Radishes Salad greens (endive, escarole, lettuce, romaine, spinach) Sauerkraut

Spinach Summer squash Tomato Tomatoes, canned Tomato sauce Tomato/vegetable juice Turnips Water chestnuts Watercress Zucchini

• 2 ounces meat = 2 meat choices, such as 1 small chicken leg or thigh 1/2 cup cottage cheese or tuna • 3 ounces meat = 3 meat choices and is about the size of a deck of cards, such as 1 medium pork chop 1 small hamburger 1/2 of a whole chicken breast 1 unbreaded fish fillet

= 400 mg or more sodium per exchange.

Meat and Meat Substitutes List Meat and meat substitutes that contain both protein and fat are on this list. In general, one meat exchange is: • 1 oz meat, fish, poultry, or cheese • 1/2 cup dried beans Based on the amount of fat they contain, meats are divided into very lean, lean, medium-fat, and high-fat lists. This is done so you can see which ones contain the least amount of fat. One ounce (one exchange) of each of these includes: Carbohydrate (grams) Very lean Lean Medium-fat High-fat

0 0 0 0

Protein (grams)

Fat (grams)

Calories

7 7 7 7

0–1 3 5 8

35 55 75 100

Nutrition tips 1. Choose very lean and lean meat choices whenever possible. Items from the high-fat group are high in saturated fat, cholesterol, and Calories and can raise blood cholesterol levels. 2. Meats do not have any fiber. 3. Dried beans, peas, and lentils are good sources of fiber. 4. Some processed meats, seafood, and soy products may contain carbohydrate when consumed in large amounts. Check the Nutrition Facts on the label to see if the amount is close to 15 grams. If so, count it as a carbohydrate choice as well as a meat choice.

Selection tips 1. Weigh meat after cooking and removing bones and fat. Four ounces of raw meat is equal to 3 ounces of cooked meat. Some examples of meat portions are: • 1 ounce cheese = 1 meat choice and is about the size of a 1-inch cube

2. Limit your choices from the high-fat group to three times per week or less. 3. Most grocery stores stock Select and Choice grades of meat. Select grades of meat are the leanest meats. 4. Choice grades contain a moderate amount of fat, and Prime cuts of meat have the highest amount of fat. Restaurants usually serve Prime cuts of meat. 5. “Hamburger” may contain added seasoning and fat, but ground beef does not. 6. Read labels to find products that are low in fat and cholesterol (5 grams or less of fat per serving). 7. Dried beans, peas, and lentils are also found on the Starch list. 8. Peanut butter, in smaller amounts, is also found on the Fats list. 9. Bacon, in smaller amounts, is also found on the Fats list.

Meal planning tips 1. Bake, roast, broil, grill, poach, steam, or boil these foods rather than frying. 2. Place meat on a rack so the fat will drain off during cooking. 3. Use a nonstick spray and a nonstick pan to brown or fry foods. 4. Trim off visible fat before or after cooking. 5. If you add flour, bread crumbs, coating mixes, fat, or marinades when cooking, ask your dietitian how to count it in your meal plan.

Very lean meat and substitutes list (One exchange equals 0 grams carbohydrate, 7 grams protein, 0–1 grams fat, and 35 Calories.) One very lean meat exchange is equal to any one of the following items. Poultry: Chicken or turkey (white meat, no skin), Cornish hen (no skin). . . . . . . . . . . . . . . . . . . . . . . . . 1 oz Fish: Fresh or frozen cod, flounder, haddock, halibut, trout; tuna fresh or canned in water . . . . . . . . . . . . . . 1 oz Shellfish: Clams, crab, lobster, scallops, shrimp, imitation shellfish . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 oz Game: Duck or pheasant (no skin), venison, buffalo, ostrich . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 oz

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Cheese with 1 gram or less fat per ounce: Nonfat or low-fat cottage cheese . . . . . . . . . . . 1/4 cup Fat-free cheese. . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 oz Other: Processed sandwich meat with 1 gram or less fat per ounce, such as deli thin, shave meats, chipped beef , turkey ham . . . . . . . . . . . . . . . . . . . 1 oz Egg whites . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Egg substitutes, plain . . . . . . . . . . . . . . . . . . . . . 1/4 cup Hot dogs with 1 gram or less fat per ounce . . . . . 1 oz Kidney (high in cholesterol) . . . . . . . . . . . . . . . . . . 1 oz Sausage with 1 gram or less fat per ounce . . . . . . . . 1 oz Count as one very lean meat and one starch exchange. Dried beans, peas, lentils (cooked) . . . . . . . . . . . . 1/2 cup = 400 mg or more sodium per exchange.

Lean meat and substitutes list (One exchange equals 0 grams carbohydrate, 7 grams protein, 3 grams fat, and 55 Calories.) One lean meat exchange is equal to any one of the following items. Beef: USDA Select or Choice grades of lean beef trimmed of fat, such as round, sirloin, and flank steak; tenderloin; roast (rib, chuck, rump); steak (T-bone, Porterhouse, cubed), ground round . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 oz Pork: Lean pork, such as fresh ham; canned, cured, or boiled ham; Canadian bacon ; tenderloin, center loin chop . . . . . . . . . . . . . . . . . . 1 oz Lamb: Roast, chop, leg . . . . . . . . . . . . . . . . . . . . . . . 1 oz Veal: Lean chop, roast . . . . . . . . . . . . . . . . . . . . . . . . 1 oz Poultry: Chicken, turkey (dark meat, no skin), chicken white meat (with skin), domestic duck or goose (well-drained of fat, no skin) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 oz Fish: Herring (uncreamed or smoked) . . . . . . . . . . . . . . 1 oz Oysters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 medium Salmon (fresh or canned), catfish . . . . . . . . . . . . . 1 oz Sardines (canned) . . . . . . . . . . . . . . . . . . . . . 2 medium Tuna (canned in oil, drained) . . . . . . . . . . . . . . . . . 1 oz Game: Goose (no skin), rabbit . . . . . . . . . . . . . . . . . 1 oz Cheese: 4.5%-fat cottage cheese . . . . . . . . . . . . . . . . . . 1/4 cup Grated Parmesan . . . . . . . . . . . . . . . . . . . . . . . . 2 Tbsp Cheeses with 3 grams or less fat per ounce . . . . . . 1 oz Other: Hot dogs with 3 grams or less fat per ounce . . 1 1/2 oz Processed sandwich meat with 3 grams or less fat per ounce, such as turkey pastrami or kielbasa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 oz Liver, heart (high in cholesterol) . . . . . . . . . . . . . . 1 oz

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A P P E N D I X E Exchange Lists for Meal Planning

Medium-fat meat and substitutes list (One exchange equals 0 grams carbohydrate, 7 grams protein, 5 grams fat, and 75 Calories.) One medium-fat meat exchange is equal to any one of the following items. Beef: Most beef products fall into this category (ground beef, meatloaf, corned beef, short ribs, prime grades of meat trimmed of fat, such as prime rib). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 oz Pork: Top loin, chop, Boston butt, cutlet . . . . . . . . . 1 oz Lamb: Rib roast, ground. . . . . . . . . . . . . . . . . . . . . . 1 oz Veal: Cutlet (ground or cubed, unbreaded) . . . . . . . . 1 oz Poultry: Chicken dark meat (with skin), ground turkey or ground chicken, fried chicken (with skin) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 oz Fish: Any fried fish product . . . . . . . . . . . . . . . . . . . 1 oz Cheese: With 5 grams or less fat per ounce Feta . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 oz Mozzarella . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 oz Ricotta . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/4 cup (2 oz) Other: Egg (high in cholesterol, limit to 3 per week) . . . . . . . 1 Sausage with 5 grams or less fat per ounce . . . . . . . 1 oz Soy milk. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 cup Tempeh . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/4 cup Tofu. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 oz or 1/2 cup

High-fat meat and substitutes list (One exchange equals 0 grams carbohydrate, 7 grams protein, 8 grams fat, and 100 Calories.) Remember these items are high in saturated fat, cholesterol, and Calories and may raise blood cholesterol levels if eaten on a regular basis. One high-fat meat exchange is equal to any one of the following items. Pork: Spareribs, ground pork, pork sausage . . . . . . . 1 oz Cheese: All regular cheeses, such as American , cheddar, Monterey Jack, Swiss . . . . . . . . . . . . . . . 1 oz Other: Processed sandwich meats with 8 grams or less fat per ounce, such as bologna, pimento loaf, salami . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 oz Sausage, such as bratwurst, Italian, knockwurst, Polish, smoked . . . . . . . . . . . . . . . . . 1 oz Hot dog (turkey or chicken) . . . . . . . . . . . . 1 (10/lb) Bacon . . . . . . . . . . . . . . . . . . . . . 3 slices (20 slices/lb) Count as one high-fat meat plus one fat exchange. Hot dog (beef, pork, or combination)

. . . . . . . 1 (10/lb)

Peanut butter (contains unsaturated fat) . . . . . . . . 2 Tbsp = 400 mg or more sodium per exchange.

Fat List Fats are divided into three groups, based on the main type of fat they contain: monounsaturated, polyunsaturated, and saturated. Small amounts of monounsaturated and polyunsaturated fats in the foods we eat are linked with good health benefits. Saturated fats are linked with heart disease and cancer. In general, one fat exchange is: • 1 teaspoon of regular margarine or vegetable oil • 1 tablespoon of regular salad dressing

Olives: ripe (black) . . . . . . . . . . . . . . . . . . . . . . . . 8 large green, stuffed . . . . . . . . . . . . . . . . . . . . . . . . . 10 large Peanut butter, smooth or crunchy . . . . . . . . . . . . . . . 2 tsp Sesame seeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Tbsp Tahini paste. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 tsp

Polyunsaturated fats list (One fat exchange equals 5 grams fat and 45 Calories.) Margarine: stick, tub, or squeeze . . . . . . . . . . . . . . . 1 tsp lower-fat (30% to 50% vegetable oil) . . . . . . . . . 1 Tbsp Mayonnaise: regular . . . . . . . . . . . . . . . . . . . . . . . . . 1 tsp reduced-fat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Tbsp Miracle Whip Salad Dressing®: regular . . . . . . . . . . 2 tsp reduced-fat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Tbsp Nuts, walnuts, English. . . . . . . . . . . . . . . . . . . . . 4 halves Oil (corn, safflower, soybean). . . . . . . . . . . . . . . . . . 1 tsp Salad dressing: regular . . . . . . . . . . . . . . . . . . . 1 Tbsp reduced-fat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Tbsp Seeds: pumpkin, sunflower . . . . . . . . . . . . . . . . . . 1 Tbsp

Nutrition tips 1. All fats are high in Calories. Limit serving sizes for good nutrition and health. 2. Nuts and seeds contain small amounts of fiber, protein, and magnesium. 3. If blood pressure is a concern, choose fats in the unsalted form to help lower sodium intake, such as unsalted peanuts.

= 400 mg or more sodium per exchange.

Selection tips 1. Check the Nutrition Facts on food labels for serving sizes. One fat exchange is based on a serving size containing 5 grams of fat. 2. When selecting regular margarine, choose those with liquid vegetable oil as the first ingredient. Soft margarines are not as saturated as stick margarines. Soft margarines are healthier choices. Avoid those listing hydrogenated or partially hydrogenated fat as the first ingredient. 3. When selecting low-fat margarines, look for liquid vegetable oil as the second ingredient. Water is usually the first ingredient. 4. When used in smaller amounts, bacon and peanut butter are counted as fat choices. When used in larger amounts, they are counted as high-fat meat choices. 5. Fat-free salad dressings are on the Other Carbohydrates list and the Free Foods list. 6. See the Free Foods list for nondairy coffee creamers, whipped topping, and fat-free products, such as margarines, salad dressings, mayonnaise, sour cream, cream cheese, and nonstick cooking spray.

Monounsaturated fats list (One fat exchange equals 5 grams fat and 45 Calories.) Avocado, medium . . . . . . . . . . . . . . . . . . . . . . . 1/8 (1 oz) Nuts almonds, cashews . . . . . . . . . . . . . . . . . . . . . . . . . 6 nuts mixed (50% peanuts) . . . . . . . . . . . . . . . . . . . . . . 6 nuts peanuts . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10 nuts pecans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4 halves Oil (canola, olive, peanut). . . . . . . . . . . . . . . . . . . . . 1 tsp

Saturated fats list* (One fat exchange equals 5 grams of fat and 45 Calories.) Bacon, cooked . . . . . . . . . . . . . . . . . 1 slice (20 slices/lb) Bacon, grease . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 tsp Butter: stick. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 tsp reduced-fat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Tbsp whipped . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 tsp Chitterlings, boiled. . . . . . . . . . . . . . . . . . 2 Tbsp (1/2 oz) Coconut, sweetened, shredded . . . . . . . . . . . . . . . 2 Tbsp Cream, half and half . . . . . . . . . . . . . . . . . . . . . . . 2 Tbsp Cream cheese: regular . . . . . . . . . . . . . . . 1 Tbsp (1/2 oz) reduced-fat . . . . . . . . . . . . . . . . . . . . . . . . 2 Tbsp (1 oz) Fatback or salt pork, see below† Shortening or lard . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 tsp Sour cream: regular . . . . . . . . . . . . . . . . . . . . . . . . 2 Tbsp reduced-fat. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 Tbsp *Saturated fats can raise blood cholesterol levels. Use a piece 1 in. × 1 in. × 1/4 in. if you plan to eat the fatback cooked with vegetables. Use a piece 2 in. × 1 in. × 1/2 in. when eating only the vegetables with the fatback removed.



Free Foods List A free food is any food or drink that contains less than 20 Calories or less than 5 grams of carbohydrate per serving. Foods with a serving size listed should be limited to three servings per day. Be sure to spread them out throughout the day. If you eat all three servings at one time, it could affect your blood glucose level. Foods listed without a serving size can be eaten as often as you like.

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Fat-free or reduced-fat foods Cream cheese, fat-free . . . . . . . . . . . . . . . . . . . . . . 1 Tbsp Creamers, nondairy, liquid . . . . . . . . . . . . . . . . . . 1 Tbsp Creamers, nondairy, powdered . . . . . . . . . . . . . . . . . 2 tsp Margarine, fat-free. . . . . . . . . . . . . . . . . . . . . . . . . 4 Tbsp Margarine, reduced-fat . . . . . . . . . . . . . . . . . . . . . . . 1 tsp Mayonnaise, fat-free . . . . . . . . . . . . . . . . . . . . . . . 1 Tbsp Mayonnaise, reduced-fat . . . . . . . . . . . . . . . . . . . . . 1 tsp Miracle Whip®, nonfat. . . . . . . . . . . . . . . . . . . . . . 1 Tbsp Miracle Whip®, reduced-fat . . . . . . . . . . . . . . . . . . . 1 tsp Nonstick cooking spray Salad dressing, fat-free . . . . . . . . . . . . . . . . . . . . . 1 Tbsp Salad dressing, fat-free, Italian . . . . . . . . . . . . . . . 2 Tbsp Salsa . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1/4 cup Sour cream, fat-free, reduced-fat. . . . . . . . . . . . . . 1 Tbsp Whipped topping, regular or light . . . . . . . . . . . . . 2 Tbsp

Sugar-free or low-sugar foods Candy, hard, sugar-free . . . . . . . . . . . . . . . . . . . . 1 candy Gelatin dessert, sugar-free Gelatin, unflavored Gum, sugar-free Jam or jelly, low-sugar or light . . . . . . . . . . . . . . . . . 2 tsp Sugar substitutes† Syrup, sugar-free . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Tbsp †

Sugar substitutes, alternatives, or replacements that are approved by the Food and Drug Administration (FDA) are safe to use. Common brand names include: ®

Equal (aspartame) Splenda® (sucralose) Sprinkle Sweet® (saccharin) Sugar Twin® (saccharin) Sweet ‘n Low® (saccharin) Sweet One® (acesulfame K) Sweet-10® (saccharin)

Drinks Bouillon, broth, consommé Bouillon or broth, low-sodium Carbonated or mineral water Club soda Cocoa powder, unsweetened . . . . . . . . . . . . . . . . . 1 Tbsp Coffee Diet soft drinks, sugar-free Drink mixes, sugar-free Tea Tonic water, sugar-free

Condiments Catsup . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Tbsp Horseradish Lemon juice Lime juice Mustard Pickles, dill . . . . . . . . . . . . . . . . . . . . . . . . . 1 1/2 large Soy sauce, regular or light Taco sauce . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Tbsp Vinegar

Seasonings Be careful with seasonings that contain sodium or are salts, such as garlic or celery salt, and lemon pepper. Flavoring extracts Garlic Herbs, fresh or dried Pimento Spices Tabasco® or hot pepper sauce Wine, used in cooking Worcestershire sauce = 400 mg or more of sodium per choice.

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A P P E N D I X E Exchange Lists for Meal Planning

Combination Foods List Many of the foods we eat are mixed together in various combinations. These combination foods do not fit into any one exchange list. Often it is hard to tell what is in a casse-

Food entrees

role dish or prepared food item. This is a list of exchanges for some typical combination foods. This list will help you fit these foods into your meal plan. Ask your dietitian for information about any other combination foods you would like to eat.

Serving size

Exchanges per serving

Chow mein (without noodles or rice) . . . . . . . . . . . . . . . . . 2 cups (16 oz) . . . . . . . 1 carbohydrate, 2 lean meats Pizza, cheese, thin crust . . . . . . . . . . . . . . . . . . . . . . . . . 1/4 of 10 in. (5 oz) . . . . 2 carbohydrates, 2 medium-fat meats, 1 fat Pizza, meat topping, thin crust . . . . . . . . . . . . . . . . . . . . 1/4 of 10 in. (5 oz) . . . . 2 carbohydrates, 2 medium-fat meats, 2 fats Pot pie . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 (7 oz). . . . . . . . . . . . . 2 carbohydrates, 1 medium-fat meat, 4 fats Tuna noodle casserole, lasagna, spaghetti with meatballs, chili with beans, macaroni and cheese . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 cup (8 oz) . . . . . . . . . 2 carbohydrates, 2 medium-fat meats

Frozen entrees

Serving size

Exchanges per serving

Entree with less than 300 calories . . . . . . . . . . . . . . . . . . 1 (8 oz). . . . . . . . . . . . . 2 carbohydrates, 3 lean meats Salisbury steak with gravy, mashed potato . . . . . . . . . . . 1 (11 oz). . . . . . . . . . . . 2 carbohydrates, 3 medium-fat meats, 3–4 fats Turkey with gravy, mashed potato, dressing . . . . . . . . . . 1 (11 oz). . . . . . . . . . . . 2 carbohydrates, 2 medium-fat meats, 2 fats

Soups

Serving size

Exchanges per serving

Bean . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 cup . . . . . . . . . . . . . . 1 carbohydrate, 1 very lean meat Cream (made with water) . . . . . . . . . . . . . . . . . . . . . . . . 1 cup (8 oz) . . . . . . . . . 1 carbohydrate, 1 fat Split pea (made with water) . . . . . . . . . . . . . . . . . . . . . . 1/2 cup (4 oz). . . . . . . . 1 carbohydrate Tomato (made with water) . . . . . . . . . . . . . . . . . . . . . . . 1 cup (8 oz) . . . . . . . . . 1 carbohydrate Vegetable beef, chicken noodle, or other broth-type . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 cup (8 oz) . . . . . . . . . 1 carbohydrate = 400 mg or more sodium per exchange.

Fast Foods* Food entrees

Serving size

Exchanges per serving

Burritos with beef . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 . . . . . . . . . . . . . . . . . . 4 carbohydrates, 2 medium-fat meats, 2 fats Chicken breast and wing, breaded and fried . . . . . . . . . . 1 each. . . . . . . . . . . . . . 1 carbohydrate, 4 medium-fat meats, 2 fats Chicken nuggets . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 6 . . . . . . . . . . . . . . . . . . 1 carbohydrate, 2 medium-fat meats, 1 fat Fish sandwich/tartar sauce . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . 3 carbohydrates, 1 medium-fat meat, 3 fats French fries, thin. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20–25 . . . . . . . . . . . . . . 2 carbohydrates, 2 fats Hamburger, large . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . 2 carbohydrates, 3 medium-fat meats, 1 fat Hamburger, regular. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . 2 carbohydrates, 2 medium-fat meats Hot dog with a bun . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . 1 carbohydrate, 1 high-fat meat, 1 fat Individual pan pizza . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 . . . . . . . . . . . . . . . . . . 5 carbohydrates, 3 medium-fat meats, 3 fats Soft-serve cone . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 medium. . . . . . . . . . . 2 carbohydrates, 1 fat Submarine sandwich . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 sub (6 in.) . . . . . . . . . 3 carbohydrates, 1 vegetable, 2 medium-fat meats, 1 fat Taco, hard shell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 (6 oz). . . . . . . . . . . . . 2 carbohydrates, 2 medium-fat meats, 2 fats Taco, soft shell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 (3 oz). . . . . . . . . . . . . 1 carbohydrate, 1 medium-fat meat, 1 fat = 400 mg or more of sodium per serving. *Ask at your fast-food restaurant for nutrition information about your favorite fast foods.

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APPENDIX

F

Calories, Percent Fat, Cholesterol, Sodium, and Dietary Fiber in Selected Fast-Food Restaurant Products* Product

Calories

% Fat Calories

Cholesterol (mg)

Sodium (mg)

Dietary Fiber (g)

320 445 500 415 708 276

36 41 44 35 37 26

44 50 55 9 84 72

950 1,270 1,220 914 1,676 451

1 2 3 2 4 4

510 670 75 650 540 470 420

39 52 0 55 33 62 35

80 95 0 15 80 180 10

880 1,020 740 930 320 1,060 1,100

3 3 2 6 0 1 7

440 470 1410 170 550 290

55 40 68 53 51 48

35 5 230 10 80 5

1,710 1,640 2,770 140 1,560 350

0 5 2 2 2 1

50 220 140 140 440 280

30 4 32 14 57 11

5 0 0 65 105 60

570 730 560 520 970 780

2 7 1 0 0 3

Arby’s (www.arbys.com) Regular roast beef Beef’n Cheddar Chicken breast fillet, grilled Roast chicken club Market Fresh roast turkey/swiss Martha’s Vineyard salad Burger King (www.burgerking.com) WHOPPER® Sandwich (w/o mayo) WHOPPER® Sandwich (mayo) Side garden salad with fat-free ranch Onion rings (king size) with zesty dippy sauce Vanilla milk shake Croissan’wich with sausage/egg/cheese BK veggie burger Hardee’s (www.hardees.com) Country Ham biscuit French fries, large Monster thickburger Cole slaw, small Charbroiled chicken club sandwich Apple turnover KFC (www.KFC.com) Green beans BBQ baked beans Mashed potatoes with gravy Breast (original recipe) without skin or dressing Side breast (extra crispy) Honey BBQ sandwich

*You may access the Website for any fast-food restaurant to obtain a detailed report on the nutrient content of all of their products.

590

Product

Calories

% Fat Calories

Cholesterol (mg)

Sodium (mg)

Dietary Fiber (g)

530 360 120 60

47 66 33 33

60 120 90 0

1,400 1,280 240 200

3 0 0 1

250 540 420 250 570 530 300 210 190

32 48 21 52 40 15 37 33 90

25 75 70 35 0 20 260 5 20

520 1,040 1,190 670 330 610 820 60 500

2 3 3 0 7 3 2 2 0

200 250 170 640 260

40 40 24 40 17

25 15 15 65 0

570 530 520 1,530 260

1 2 4 3 1

320 280 530 230 370

16 14 53 11 12

35 20 45 0 50

1,290 1,000 1,010 500 1,200

5 5 5 5 5

330 200 170 440 520

18 40 21 52 48

0 25 25 35 75

1,200 630 730 800 1,420

9 3 3 7 3

430 320 270 320 70 120 330

42 20 0 11 51 97 25

75 70 0 10 10 20 55

870 950 25 50 170 200 1,170

2 2 7 7 2 0 8

950 790 800 850 860

42 15 38 49 25

140 75 65 125 130

2,310 2,270 1,880 2,260 2,400

8 20 16 7 24

Long John Silver’s (www.longjohnsilvers.com) Ultimate fish sandwich Battered shrimp (8 pieces) Baked cod (1 piece) Hush puppies, one pup McDonald’s (www.mcdonalds.com) Hamburger Big Mac Premium grilled chicken classic sandwich Chicken McNuggets (6 pieces) French fries (large) Hotcakes with syrup Egg McMuffin Fruit and walnut salad Salad dressing, creamy Caesar (2 oz) Pizza Hut (www.pizzahut.com) Thin ’N Crispy cheese, 1 medium slice Pan, cheese,Veggie Lover’s medium slice Fit N’ Delicious diced chicken, red onion, green pepper Personal pan pizza, pepperoni (whole pizza) Cherry dessert pizza, 1 slice Subway (www.subway.com) Subway Club (6 inches) Turkey breast (6 inches) Tuna deli (6 inches) Veggie Delite (6 inches) Sweet onion Chicken Teriyaki (6 inches) Taco Bell (www.tacobell.com) Bean burrito, Fresco style Soft taco, beef, regular Chicken Ranchero, taco, Fresco style Nachos Supreme, regular Chicken Quesadilla, regular Wendy’s (www.wendys.com) Classic single w/everything Ultimate Chicken grilled sandwich Plain potato, baked Potato with sour cream and chives Caesar side salad Caesar dressing Chili (large) Baja Fresh (www.bajafresh.com) Burrito Ultimo, steak Burrito Mexicano, chicken Grilled veggie burrito Baja burrito, steak Chicken with corn tortillas

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APPENDIX

G

Energy Pathways of Carbohydrate, Fat, and Protein Addition of phosphorus to glucose by ATP activates the 6-carbon glucose molecule. The later metabolism of fructose 6–phosphate to fructose 1-6 bisphosphate uses another ATP.

Glucose ATP 1 ADP

H

O

CH2

Fructose 6–phosphate 3

ADP

C

H

OH

HO 2

H

Fructose 1,6–bisphosphate

P

O

CH2

Glyceraldehyde 3–phosphate

(2) NADH + H+

The conversion of each pyruvate to lactate allows a cell to recycle NADH + H+ back to NAD. This then allows glycolysis to continue, as NAD is needed. This latter pathway occurs primarily in only a few types of cells, such as red blood cells, and under anaerobic conditions such as very high-intensity exercise. Most NADH + H+ is recycled back to NAD in the mitochondria (using the electron transport chain).

(2) ADP

C

O

C

OH

CH2

H

8

H

9 H2O (2) Phosphoenolpyruvate (2) ADP

OH C CH3

10

O

C

OH

P

P

Metabolism of each 1,3– bisphosphoglycerate to 3– phosphoglycerate results in the synthesis of ATP.

C

OH

C

OH P

O

H

C

OH

C

O

P

CH2OH Metabolism of each phosphoenolpyruvate to pyruvate results in the synthesis of another ATP.

C

OH

C

O

P

CH2

11

(2) Pyruvate

OH H

C

O

(2) NADH + H+

C

P The 6-carbon molecule, fructose 1,6–bisphosphate, is split into two 3-carbon molecules: one is glyceraldehyde 3–phosphate, and the other is eventually converted into that product as well.

P

CH2 O

(2) 2–Phosphoglycerate

O

O

O

O (2) 3–Phosphoglycerate

(2) Lactate

OH

CH2 O

(2) ATP

(2) NAD

P CH2

O

7

(2) ATP

592

H H

6

(2) 1,3–Bisphosphoglycerate

O O

OH H

5

Pi

OH

OH

H HO

H

CH2OH

(2) NAD

P

OH

OH H

4

Dihydroxyacetone phosphate

H OH H

H O P O CH OH 2

H HO

O O H

CH2

Glucose 6–phosphate

ATP

CH2

CH2OH O H H OH H HO OH H

O C

OH

C

O

CH3

Pyruvate can undergo further metabolism to enter the citric acid cycle, which occurs in the mitochondria.

Citric Acid Cycle

F I G U R E G . 1 Detailed depiction of the individual chemical reactions that comprise glycolysis—glucose to pyruvate. Glycolysis takes place in the cytosol of the cell. The enzymes in the cytosol that participate at the following steps are (1) hexokinase, (2) phosphohexose isomerase, (3) phosphofructokinase, (4) aldolase, (5) phosphotriose isomerase, (6) glyceraldehyde-3-phosphate dehydrogenase, (7) phosphoglycerate kinase, (8) phosphoglycerate mutase, (9) enolase, and (10) pyruvate kinase. Sometimes (11) lactate dehydrogenase is used to recycle NADH + H+ back to NAD (anaerobic glycolysis). P represents a phosphate group.

3 Pyruvate

Transition Reaction

NAD NADH

Pyruvate is first metabolized in a transition reaction to acetyl-CoA. It is acetyl-CoA that actually enters the citric acid cycle. In the process, NADH H is produced and CO2 is lost. Acetyl CoA may also be generated from fatty acids and amino acids to serve as a source of energy.

CO2 CoA H

2 Acetyl-CoA

NADH

2 The citric acid cycle begins when an acetyl group carried by CoA combines with a C4 oxaloacetate molecule to form citrate.

H

CO2

3

NAD 6 Citrate

5 Alpha-ketogluterate

1

Twice over, substrates are oxidized, NAD is reduced to NADH H and CO2 is released.

CoA 2

NAD

Acetyl-CoA

Citric acid cycle

4 Oxaloacetate

8

NADH

4

4 4 GTP

Succinate NAD

7 FAD

Once again an intermediate in the cycle is oxidized, and NAD is reduced to NADH H .

H

CO2

Fumarate Oxaloacetate is re-formed during the final step of the cycle.

NADH

5

H

6 ATP

ATP eventually is made as energy is released from the breakdown of an intermediate in the cycle.

FADH2 Again an intermediate in the cycle is oxidized, but this time FAD is reduced to FADH2.

F I G U R E G . 2 The transition reaction and the citric acid cycle. The net result of one turn of this cycle of reactions (squares, steps 1–8) is the oxidation of an acetyl group to two molecules of CO2 and the formation of three molecules of NADH + H+ and one molecule of FADH2. One GTP molecule also results, which eventually forms ATP. The citric acid cycle turns twice per glucose molecule. Note that oxygen does not participate in any of the steps in the citric acid cycle. It instead participates in the electron transport chain, where the vast majority of the ATP is formed (see figure G.3). The numbers in the circles represent the number of carbon atoms.

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Electron Transport System NADH dehydrogenase complex H

Cytochrome b,c1 complex

H

3

2

1

Cytochrome c oxidase complex

e H

CoQ

e

e

e

FADH2

FAD

2H

4 NADH H

Outer Membrane

H NAD

H

H

Mitochondrial Matrix

1 — 2

2H

5 ATP

O2 H2O

ADP

Pi

H

H H

H H ATP

ATP channel protein

H

H

Intermembrane Space

ATP synthase complex

F I G U R E G . 3 Organization of the electron transport chain. As electrons move from one molecular complex to the other, hydrogen ions (H+) are pumped from the mitochondrial matrix into the intermembrane space (steps 1–4). (Note that each mitochondrion has an inner and outer membrane. Hydrogen ions flow down a concentration gradient from the intermembrane space into the mitochondrial matrix; ATP is then synthesized by the enzyme ATP synthase (step 5). ATP leaves the mitochondrial matrix by way of a channel protein.

594

Adipose Cells

Absorbed fat travels as chylomicron

Hormone sensitive lipase

Chylomicron remnant to liver

Fat leaves liver and travels as VLDL VLDL

1

Triglycerides

Intestine

2 Chylomicron

Liver

Blood Plasma Glycerol (to liver)

Free fatty acids

Also called IDL*

VLDL remnant c

Albumin

Muscle cell receptor

Muscle Cell

Fat to body tissues via lipoprotein lipase

Fat to body cells after breakdown by lipoprotein lipase LDL taken up by receptor pathways (in body cells)

Free fatty acids 4

Fatty acyl CoA synthetase Fatty acyl CoA HDL arises from the liver and intestine and buds off other lipoproteins. HDL transfers cholesterol from body cells mostly to other lipoproteins for disposal

Carnitine Mitochondria

3

HDL c

HDL

LDL c LDL taken up by scavenger pathways (in blood vessels), especially oxidized LDL

c

Fatty acyl CoA Beta-oxidation Acetyl CoA

F I G U R E G . 4 A Energy pathways for fatty acids. Triglycerides in the adipose tissue may be catabolized by hormone-sensitive lipase, with the fatty acids being released to the plasma and binding with albumin; the glycerol component is transported to the liver for metabolism. A receptor at the muscle cell transports the fatty acid into the muscle cell where it is converted into fatty acyl CoA by an enzyme (fatty acyl CoA synthetase). The fatty acyl CoA is then transported into the mitochondria with carnitine (in an enzyme complex) as a carrier. The fatty acyl CoA, which is a combination of acetyl CoA units, then undergoes beta-oxidation, a process that splits off the acetyl CoA units for entrance into the Krebs cycle.

Lipoprotein interactions. (1) Chylomicrons carry absorbed fat to body cells. (2) VLDL carries fat taken up from the bloodstream by the liver, as well as any fat made by the liver, to body cells. (3) LDL arises from VLDL and carries mostly cholesterol to cells. (4) HDL arises from body cells, mostly in the liver and intestine as well as from particles that bud off the other lipoproteins. HDL carries cholesterol from cells to other lipoproteins and to the liver for excretion.

FIGURE G.4B

*Intermediate Density Lipoprotein.

cysteine alanine glycine serine

isoleucine leucine tryptophan

Pyruvate asparagine aspartate

tyrosine phenylalanine aspartate

Acetyl CoA

phenylalanine leucine lycine tyrosine

Acetoacetyl CoA

Oxaloacetate

Fumarate

Krebs cycle

Succinyl CoA

isoleucine methionine threonine valine

α-Ketoglutarate

glutamate glutamine histidine proline arginine

F I G U R E G . 5 Metabolic fates of various amino acids.Various amino acids, after deamination, may enter into energy pathways at different sites. 595

APPENDIX

H

Small Steps: 120 Small Steps to a Healthier Diet and Increased Physical Activity 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34. 35. 596

Walk to work. Use fat-free milk over whole milk. Do sit-ups in front of the TV. Walk during lunch hour. Drink water before a meal. Eat leaner red meat & poultry. Eat half your dessert. Walk instead of driving whenever you can. Take family walk after dinner. Skate to work instead of driving. Avoid food portions larger than your fist. Mow lawn with push mower. Increase the fiber in your diet. Walk to your place of worship instead of driving. Walk kids to school. Get a dog and walk it. Join an exercise group. Drink diet soda. Replace Sunday drive with Sunday walk. Do yard work. Eat off smaller plates. Get off a stop early & walk. Don’t eat late at night. Skip seconds. Work around the house. Skip buffets. Grill, steam, or bake instead of frying. Bicycle to the store instead of driving. Take dog to the park. Ask your doctor about taking a multivitamin. Go for a half-hour walk instead of watching TV. Use vegetable oils over solid fats. More carrots, less cake. Fetch the newspaper yourself. Sit up straight at work.

36. 37. 38. 39. 40. 41. 42. 43. 44. 45. 46. 47. 48. 49. 50. 51. 52. 53. 54. 55. 56. 57. 58. 59. 60. 61. 62. 63.

Wash the car by hand. Don’t skip meals. Eat more celery sticks. Run when running errands. Pace the sidelines at kids’ athletic games. Take wheels off luggage. Choose an activity that fits into your daily life. Try your burger with just lettuce, tomato, and onion. Ask a friend to exercise with you. Make time in your day for physical activity. Exercise with a video if the weather is bad. Bike to the barbershop or beauty salon instead of driving. Keep to a regular eating schedule. If you find it difficult to be active after work, try it before work. Take a walk or do desk exercises instead of a cigarette or coffee break. Perform gardening or home repair activities. Avoid laborsaving devices. Take small trips on foot to get your body moving. Play with your kids 30 minutes a day. Dance to music. Keep a pair of comfortable walking or running shoes in your car and office. Make a Saturday morning walk a group habit. Walk briskly in the mall. Choose activities you enjoy and you’ll be more likely to stick with them. Stretch before bed to give you more energy when you wake. Take the long way to the water cooler. Explore new physical activities. Vary your activities, for interest and to broaden the range of benefits.

64. 65. 66. 67. 68. 69. 70. 71. 72. 73. 74. 75. 76. 77. 78. 79. 80. 81. 82. 83. 84. 85. 86. 87. 88. 89. 90. 91. 92. 93. 94. 95. 96. 97. 98. 99.

Reward and acknowledge your efforts. Choose fruit for dessert. Consume alcoholic beverages in moderation, if at all. Take stairs instead of the escalator. Conduct an inventory of your meal/snack and physical activity patterns. Share an entrée with a friend. Grill fruit or vegetables. Eat before grocery shopping. Choose a checkout line without a candy display. Make a grocery list before you shop. Buy 100% fruit juices over soda and sugary drinks. Stay active in winter. Play with your kids. Flavor foods with herbs, spices, and other low-fat seasonings. Remove skin from poultry before cooking to lower fat content. Eat before you get too hungry. Don’t skip breakfast. Stop eating when you are full. Snack on fruits and vegetables. Top your favorite cereal with apples or bananas. Try brown rice or whole wheat pasta. Include several servings of whole-grain food daily. When eating out, choose a small or medium portion. If main dishes are too big, choose an appetizer or a side dish instead. Ask for salad dressing “on the side.” Don’t take seconds. Park farther from destination and walk. Try a green salad instead of fries. Bake or broil fish. Walk instead of sitting around. Eat sweet foods in small amounts. Take your dog on longer walks. Drink lots of water. Cut back on added fats or oils in cooking or spreads. Walk the beach instead of sunbathing. Walk to a co-worker’s desk instead of e-mailing or calling them. Carry your groceries instead of pushing a cart.

100. Use a snow shovel instead of a snow blower. 101. Cut high-Calorie foods like cheese and chocolate into smaller pieces and eat only a few pieces. 102. Use nonfat or low-fat sour cream, mayo, sauces, dressings, and other condiments. 103. Replace sugar-sweetened beverages with water and add a twist of lemon or lime. 104. Replace high-saturated fat/high Calorie seasonings with herbs grown in a small herb garden in your kitchen window. 105. Refrigerate prepared soups before you eat them. As the soup cools, the fat will rise to the top. Skim it off the surface for reduced-fat content. 106. When eating out, ask your server to put half your entrée in a to-go bag. 107. Substitute vegetables for other ingredients in your sandwich. 108. Every time you eat a meal, sit down, chew slowly, and pay attention to flavors and textures. 109. Try a new fruit or vegetable. (Ever had jicama, plantain, bok choy, starfruit, or papaya?) 110. Make up a batch of brownies with applesauce instead of oil or shortening. 111. Instead of eating out, bring a healthy, low-Calorie lunch to work. 112. Ask your sweetie to bring you fruit or flowers instead of chocolate. 113. Speak up for the salad bar when your co-workers are picking a restaurant for lunch, and remember Calories count, so pay attention to how much and what you eat. 114. When walking, go up the hills instead of around them. 115. Walk briskly through the mall and shop ’til you drop . . . pounds. 116. Clean your closet and donate clothes that are too big. 117. Take your body measurements to gauge progress. 118. Buy a set of hand weights and play a round of Simon Says with your kids. You do it with the weights; they do it without. 119. Swim with your kids. 120. Wear a SmallSteps bracelet to remind you to live a healthier lifestyle every day.

Source: www.SmallStep.Gov

www.mhhe.com/williams9

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APPENDIX

I

Sample Menu for a 2,000-Calorie Food Pattern

Sample Menus for a 2,000 calorie food pattern Averaged over a week, this seven day menu provides all of the recommended amounts of nutrients and food from each food group. (Italicized foods are part of the dish or food that precedes it.) Food Group

Daily Average

GRAINS

Total Grains (oz eq) 6.0 Whole Grains 3.4 Refined Grains 2.6

VEGETABLES*

Total Veg* (cups) 2.6

FRUITS

Fruits (cups) 2.1

MILK

Milk (cups) 3.1

MEAT & BEANS

Meat/ Beans (oz eq) 5.6

OILS

Oils (tsp/grams) 7.2 tsp/32.4 g

*Vegetable subgroups (weekly totals) Dark-Green Veg (cups) 3.3 Orange Veg (cups) 2.3 Beans/Peas (cups) 3.0 Starchy Veg (cups) 3.4 Other Veg (cups) 6.6

598

Nutrient

Daily Average

Calories Protein, g Protein, % kcal Carbohydrate, g Carbohydrate, % kcal Total fat, g Total fat, % kcal Saturated fat, g Saturated fat, % kcal Monounsaturated fat, g Polyunsaturated fat, g Linoleic Acid, g Alpha-linolenic Acid, g Cholesterol, mg Total dietary fiber, g Potassium, mg Sodium, mg* Calcium, mg Magnesium, mg Copper, mg Iron, mg Phosphorus, mg Zinc, mg Thiamin, mg Riboflavin, mg Niacin Equivalents, mg Vitamin B6, mg Vitamin B12, mcg Vitamin C, mg Vitamin E, mg (AT) Vitamin A, mcg (RAE) Dietary Folate Equivalents, mcg

1994 98 20 264 53 67 30 16 7.0 23 23 21 1.1 207 31 4715 1948 1389 432 1.9 21 1830 14 1.9 2.5 24 2.9 18.4 190 18.9 1430 558

* Starred items are foods that are labelled as no-salt-added, low-sodium, or low-salt versions of the foods.They can also be prepared from scratch with little or no added salt. All other foods are regular commercial products which contain variable levels of sodium. Average sodium level of the 7-day menu assumes no-salt-added in cooking or at the table.

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1 cup cantaloupe

SNACKS

Stuffed broiled salmon 5 ounce salmon filet 1 ounce bread stuffing mix 1 tbsp chopped onions 1 tbsp diced celery 2 tsp canola oil 1/2 cup saffron (white) rice 1 ounce slivered almonds 1/2 cup steamed broccoli 1 tsp soft margarine 1 cup fat-free milk

DINNER

Roast beef sandwich 1 whole grain sandwich bun 3 ounces lean roast beef 2 slices tomato 1/4 cup shredded romaine lettuce 1/8 cup sauteed mushrooms (in 1 tsp oil) 1 1/2 ounce part-skim mozzarella cheese 1 tsp yellow mustard 3/4 cup baked potato wedges* 1 tbsp ketchup 1 unsweetened beverage

LUNCH

Cold cereal 1 cup bran flakes 1 cup fat-free milk 1 small banana 1 slice whole wheat toast 1 tsp soft margarine 1 cup prune juice

Hot cereal 1/2 cup cooked oatmeal 2 tbsp raisins 1 tsp soft margarine 1/2 cup fat-free milk 1 cup orange juice

Breakfast burrito 1 flour tortilla (7" diameter) 1 scrambled egg (in 1 tsp soft margarine) 1/3 cup black beans* 2 tbsp salsa 1 cup orange juice 1 cup fat-free milk

Roasted chicken breast 3 ounces boneless skinless chicken breast* 1 large baked sweet potato 1/2 cup peas and onions 1 tsp soft magarine 1 ounce whole wheat dinner roll 1 tsp soft margarine 1 cup leafy greens salad 3 tsp sunflower oil and vinegar dressing SNACKS 1/4 cup dried apricots 1 cup low-fat fruited yogurt

SNACKS 1/2 ounce dry-roasted almonds* 1/4 cup pineapple 2 tbsp raisins

DINNER

Tuna fish sandwich 2 slices rye bread 3 ounces tuna (packed in water, drained) 2 tsp mayonnaise 1 tbsp diced celery 1/4 cup shredded romaine lettuce 2 slices tomato 1 medium pear 1 cup fat-free milk

Spinach lasagna 1 cup lasagna noodles, cooked (2 oz dry) 2/3 cup cooked spinach 1/2 cup ricotta cheese 1/2 cup tomato sauce tomato bits* 1 ounce part-skim mozzarella cheese 1 ounce whole wheat dinner roll 1 cup fat-free milk

DINNER

Taco salad 2 ounces tortilla chips 2 ounces ground turkey, sauteed in 2 tsp sunflower oil 1/2 cup black beans* 1/2 cup iceberg lettuce 2 slices tomato 1 ounce low-fat cheddar cheese 2 tbsp salsa 1/2 cup avocado 1 tsp lime juice 1 unsweetened beverage

LUNCH

BREAKFAST

BREAKFAST

BREAKFAST

LUNCH

Day 3

Day 2

Day 1

1 cup low-fat fruited yogurt

SNACKS

Rigatoni with meat sauce 1 cup rigatoni pasta (2 ounces dry) 1/2 cup tomato sauce tomato bits* 2 ounces extra lean cooked ground beef (sauteed in 2 tsp vegetable oil) 3 tbsp grated Parmesan cheese Spinach salad 1 cup baby spinach leaves 1/2 cup tangerine slices 1/2 ounce chopped walnuts 3 tsp sunflower oil and vinegar dressing 1 cup fat-free milk

DINNER

White bean-vegetable soup 1 1/4 cup chunky vegetable soup 1/2 cup white beans* 2 ounce breadstick 8 baby carrots 1 cup fat-free milk

LUNCH

1 whole wheat English muffin 2 tsp soft margarine 1 tbsp jam or preserves 1 medium grapefruit 1 hard-cooked egg 1 unsweetened beverage

BREAKFAST

Day 4

600 SNACKS 5 whole wheat crackers* 1/8 cup hummus 1/2 cup fruit cocktail (in water or juice)

SNACKS

1 cup low-fat fruited yogurt

DINNER

Grilled top loin steak 5 ounces grilled top loin steak 3/4 cup mashed potatoes 2 tsp soft margarine 1/2 cup steamed carrots 1 tbsp honey 2 ounces whole wheat dinner roll 1 tsp soft margarine 1 cup fat-free milk

DINNER

Vegetarian chili on baked potato 1 cup kidney beans* 1/2 cup tomato sauce w/ tomato tidbits* 3 tbsp chopped onions 1 ounce low-fat cheddar cheese 1 tsp vegetable oil 1 medium baked potato 1/2 cup cantaloupe 3/4 cup lemonade

Hawaiian pizza 2 slices cheese pizza 1 ounce canadian bacon 1/4 cup pineapple 2 tbsp mushrooms 2 tbsp chopped onions Green salad 1 cup leafy greens 3 tsp sunflower oil and vinegar dressing 1 cup fat-free milk

Smoked turkey sandwich 2 ounces whole wheat pita bread 1/4 cup romaine lettuce 2 slices tomato 3 ounces sliced smoked turkey breast* 1 tbsp mayo-type salad dressing 1 tsp yellow mustard 1/2 cup apple slices 1 cup tomato juice*

LUNCH

French toast 2 slices whole wheat French toast 2 tsp soft margarine 2 tbsp maple syrup 1/2 medium grapefruit 1 cup fat-free milk

Cold cereal 1 cup puffed wheat cereal 1 tbsp raisins 1 cup fat-free milk 1 small banana 1 slice whole wheat toast 1 tsp soft margarine 1 tsp jelly LUNCH

BREAKFAST

BREAKFAST

BREAKFAST

1 ounce sunflower seeds* 1 large banana 1 cup low-fat fruited yogurt

SNACKS

Vegetable stir-fry 4 ounces tofu (firm) 1/4 cup green and red bell peppers 1/2 cup bok choy 2 tbsp vegetable oil 1 cup brown rice 1 cup lemon-flavored iced tea

DINNER

Manhattan clam chowder 3 ounces canned clams (drained) 3/4 cup mixed vegetables 1 cup canned tomatoes* 10 whole wheat crackers* 1 medium orange 1 cup fat-free milk

LUNCH

Pancakes 3 buckwheat pancakes 2 tsp soft margarine 3 tbsp maple syrup 1/2 cup strawberries 3/4 cup honeydew melon 1/2 cup fat-free milk

D ay 7

Day 6

Day 5

Source: www.MyPyramid.gov

* Starred items are foods that are labeled as no-salt-added, lowsodium, or low-salt versions of the foods.They can also be prepared from scratch with little or no added salt. All other foods are regular commercial products which contain variable levels of sodium. Average sodium level of the 7-day menu assumes no-salt-added in cooking or at the table

APPENDIX

J

MyPyramid for Kids F I G U R E J . 1 The USDA has created a version of MyPyramid for children ages 6 to 11. The accompanying Website (http://mypyramid.gov/kids/index.html) also features kid-friendly resources— such as an interactive MyPyramid Blast Off Game and a meal tracking worksheet—designed to encourage children to make healthier eating and activity choices. This site also contains information and resources that adults can use in educating children about proper nutrition.

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Glossary Acceptable Daily Intake (ADI) The amount of a food additive an individual can consume without an adverse effect. Acceptable Macronutrient Distribution Range (AMDR) A range of dietary intakes for carbohydrate, fat, and protein that is associated with reduced risk of chronic disease while providing adequate nutrients. acclimatization The ability of the body to undergo physiological adaptations so that the stress of a given environment, such as high environmental temperature, is less severe. acetaldehyde An intermediate breakdown product of alcohol. acetic acid A naturally occurring saturated fatty acid; a precursor for the Krebs cycle when converted into acetyl CoA. acetyl CoA The major fuel for the oxidative processes in the body, being derived from the breakdown of glucose and fatty acids. acid-base balance A relative balance of acid and base products in the body so that an optimal pH is maintained in the tissues, particularly the blood. acidosis A disturbance of the normal acidbase balance in which excess acids accumulate in the body. Lactic acid production during exercise may lead to acidosis. acrylamide A cancer-causing agent that may be produced by prolonged, hightemperature cooking. active transport A process requiring energy to transport substances across cell membranes. activity-stat Center in the brain theorized to regulate daily physical activity. acute exercise bout A single bout of exercise that will produce various physiological reactions dependent upon the nature of the exercise; a single workout. added sugars Refined sugars added to foods during commercial food processing. additives Substances added to food to improve flavor, color, texture, stability, or for similar purposes. adenosine triphosphate See ATP. Adequate Intake (AI) Recommended dietary intake comparable to the RDA, but based on less scientific evidence. 602

adipokines Substances released from adipose (fat) cells that function as hormones in other parts of the body. Adonis complex A disturbed body image in which muscular individuals consider themselves too thin or not sufficiently muscular; also known as muscle dysmorphia. adrenaline A hormone secreted by the adrenal medulla; it is a stimulant and prepares the body for “fight or flight.” aerobic Relating to energy processes that occur in the presence of oxygen. aerobic glycolysis Oxidative processes in the cell that liberate energy in the metabolism of the carbohydrate glycogen. aerobic lipolysis Oxidative processes in the cell that liberate energy in the metabolism of fats. aerobic walking Rapid walking designed to elevate the heart rate so that a training effect will occur; more strenuous than ordinary leisure walking. Air Displacement Plethysmography A procedure to measure body composition via displacement of air in a special chamber; comparable to water displacement in underwater weighing techniques to evaluate body composition. alanine A nonessential amino acid. alcohol A colorless liquid with depressant effects; ethyl alcohol or ethanol is the alcohol designed for human consumption. alcohol dehydrogenase An enzyme in the liver that initiates the breakdown of alcohol to acetaldehyde. alcoholism A rather undefined term used to describe individuals who abuse the effect of alcohol; an addiction or habituation that may result in physical and/or psychological withdrawal effects. aldosterone The main electrolyte-regulating hormone secreted by the adrenal cortex; primarily controls sodium and potassium balance. allithiamine A derivative of thiamine. alpha-ketoacid Specific acids associated with different amino acids and released upon deamination or transamination; for example,

the breakdown of glutamate yields alpha-ketoglutarate. alpha-linolenic acid An omega-3 fatty acid considered to be an essential nutrient. alpha-tocopherol The most biologically active alcohol in vitamin E. alpha-tocopherol equivalent The amount of other forms of tocopherol to equal the vitamin E activity of one milligram of alpha-tocopherol. AMDR See Acceptable Macronutrient Distribution Range. amenorrhea Absence or cessation of menstruation. amino acids The chief structural material of protein, consisting of an amino group (NH2) and an acid group (COOH) plus other components. amino group The nitrogen-containing component of amino acids (NH2). aminostatic theory A theory suggesting that hunger is controlled by the presence or absence of amino acids in the blood acting upon a receptor in the hypothalamus. ammonia A metabolic by-product of the oxidation of glutamine; it may be transformed into urea for excretion from the body. amylopectin A branched-chain starch. amylose A straight-chain starch that is more resistant to digestion compared to amylopectin. anabolic/androgenic steroids (AAS) Drugs designed to mimic the actions of testosterone to build muscle tissue (anabolism) while minimizing the androgenic effects (masculinization). anabolism Constructive metabolism, the process whereby simple body compounds are formed into more complex ones. anaerobic Relating to energy processes that occur in the absence of oxygen. anaerobic glycolysis Metabolic processes in the cell that liberate energy in the metabolism of the carbohydrate glycogen without the involvement of oxidation. anaerobic threshold The intensity of exercise at which the individual begins to increase the proportion of energy derived from

anaerobic means, principally the lactic acid system. Also see steady-state threshold and onset of blood lactic acid (OBLA). android-type obesity Male-type obesity in which the body fat accumulates in the abdominal area and is a more significant risk factor for chronic disease than is gynoid-type obesity. androstenedione An androgen produced in the body that is converted to testosterone; marketed as a dietary supplement. anemia In general, subnormal levels of circulating RBCs and hemoglobin; there are many different types of anemia. angina The pain experienced under the breastbone or in other areas of the upper body when the heart is deprived of oxygen. anion A negatively charged ion, or electrolyte. anorexia athletica A form of anorexia nervosa observed in athletes involved in sports in which low percentages of body fat may enhance performance, such as gymnastics and ballet. anorexia nervosa A serious nervous condition, particularly among teenage girls and young women, marked by a loss of appetite and leading to various degrees of emaciation. anthropometry Use of body girths and diameters to evaluate body composition. antibodies Protein substances developed in the body in reaction to the presence of a foreign substance, called an antigen; natural antibodies are also present in the blood. They are protective in nature. antidiuretic hormone (ADH) Hormone secreted by the pituitary gland; its major action is to conserve body water by decreasing urine formation; also known as vasopressin. antinutrients Substances in foods that can adversely affect nutrient status. antioxidant A compound that may protect other compounds from the effects of oxygen. The antioxidant itself interferes with oxidative processes. antipromoters Compounds that block the actions of promoters, agents associated with the development of certain diseases, such as cancer. apolipoprotein A class of special proteins associated with the formation of lipoproteins. A variety of apolipoproteins have been identified and are involved in the specific functions of the different lipoproteins. appetite A pleasant desire for food for the purpose of enjoyment that is developed through previous experience; believed to be

controlled in humans by an appetite center, or appestat, in the hypothalamus. arginine An essential amino acid. arteriosclerosis Hardening of the arteries; also see atherosclerosis. ascorbic acid Vitamin C. aspartame An artificial sweetener made from amino acids. aspartates Salts of aspartic acid, an amino acid. atherosclerosis A specific form of arteriosclerosis characterized by the formation of plaque on the inner layers of the arterial wall. athletic amenorrhea The cessation of menstruation in athletes, believed to be caused by factors associated with participation in strenuous physical activity. ATP Adenosine triphosphate, a high-energy phosphate compound found in the body; one of the major forms of energy available for immediate use in the body. ATPase The enzyme involved in the splitting of ATP and the release of energy. ATP-PCr system The energy system for fast, powerful muscle contractions; uses ATP as the immediate energy source, the spent ATP being quickly regenerated by breakdown of the PCr. ATP and PCr are high-energy phosphates in the muscle cell. baking soda A commercial form of sodium bicarbonate. basal energy expenditure (BEE) The basal metabolic rate (BMR) total energy expenditure over 24 hours. basal metabolic rate (BMR) The measurement of energy expenditure in the body under resting, postabsorptive conditions, indicative of the energy needed to maintain life under these basal conditions. Basic Four Food Groups Grouping of foods into four categories that can be used as a means to educate individuals on how to obtain essential nutrients. The four groups are meat, milk, bread-cereal, and fruit-vegetable. bee pollen A nutritional product containing minute amounts of protein and some vitamins that has been advertised to be possibly ergogenic for some athletes. behavior modification Relative to weightcontrol methods, behavioral patterns, or the way one acts, may be modified to help achieve weight loss. beriberi A deficiency disease attributed to lack of thiamin (vitamin B1) in the diet. beta-alanine A nonessential amino acid, also labeled as β-alanine that is a part of the

peptides carnosine and anserine; beta-alanine is purported to have ergogenic potential. beta-carotene A precursor for vitamin A found in plants. beta glucan Gummy form of water-soluble fiber useful in reducing serum cholesterol; oats are a good source. beta-oxidation Process in the cells whereby 2-carbon units of acetic acid are removed from long-chain fatty acids for conversion to acetyl CoA and oxidation via the Krebs cycle. bile A fluid secreted by the liver into the intestine that aids in the breakdown process of fats. bile salts Active salts found in bile; cholesterol is part of their structure. binge eating disorder (BED) Individuals with BED demonstrate some of the same behaviors as those with bulimia nervosa, such as eating more quickly and until uncomfortably full, but do not purge. binge-purge syndrome An eating behavior characterized by excessive hunger leading to gorging, followed by guilt and purging by vomiting. Also see bulimia nervosa. bioavailability In relation to nutrients in food, the amount that may be absorbed into the body. bioelectrical impedance analysis (BIA) A method to calculate percentage of body fat by measuring electrical resistance due to the water content of the body. bioengineered foods Foods modified by genetic engineering to produce desirable traits. biotin A component of the B complex. bisphosphonates Drugs used to inhibit bone resorption, but not mineralization, to help prevent bone loss and increase bone mineral density; Fosamax is one brand. blood alcohol content (BAC) The concentration of alcohol in the blood, usually expressed as milligram percent. blood alcohol level See blood alcohol content. blood glucose Blood sugar; the means by which carbohydrate is carried in the blood; normal range is 70–120 mg/ml. blood pressure The pressure of the blood in the blood vessels; usually used to refer to arterial blood pressure. Also see systolic blood pressure and diastolic blood pressure. BMI See Body Mass Index. body image The image or impression the individual has of his or her body. A poor body image may lead to personality problems. www.mhhe.com/williams9

603

Body Mass Index (BMI) An index calculated by a ratio of height to weight, used as a measure of obesity. body plethysmography A body composition technique using a special chamber to measure air displacement; similar to water displacement theory associated with underwater weighing. branched-chain amino acids (BCAA) Three essential amino acids (leucine, isoleucine, and valine) that help form muscle tissue. bread exchange One bread exchange in the Food Exchange System contains 15 grams of carbohydrate, 3 grams of protein, and 80 Calories. brown fat A special form of adipose tissue that is designed to produce heat; small amounts are found in humans in the area of vital organs such as the heart and lungs. buffer boosting Term associated with use of sodium bicarbonate as an ergogenic aid to increase the acid-buffering capacity of the blood. bulimia nervosa An eating disorder involving a loss of control over the impulse to binge; the binge-purge syndrome. bulk-up method A method of weight training designed to increase muscle mass; uses high resistance and moderate volume with many different muscle groups. caffeine A stimulant drug found in many food products such as coffee, tea, and cola drinks; stimulates the central nervous system. calciferol A synthetic vitamin D. calcitriol The hormone form of vitamin D. calcium A silver-white metallic element essential to human nutrition. caloric concept of weight control The concept that Calories are the basis of weight control. Excess Calories will add body weight while caloric deficiencies will contribute to weight loss. caloric deficit A negative caloric balance whereby more Calories are expended than consumed; a weight loss will occur. Calorie A Calorie is a measure of heat energy. A small Calorie represents the amount of heat needed to raise one gram of water one degree Celsius. A large Calorie (kilocalorie, KC, or C) is 1,000 small Calories. calorimeter A device used to measure the caloric value of a given food, or heat production of animals or humans. calorimetry The science of measuring heat production. carbohydrates A group of compounds containing carbon, hydrogen, and oxygen. 604

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Glucose, glycogen, sugar, starches, fiber, cellulose, and the various saccharides are all carbohydrates. carbohydrate-electrolyte solutions (CES) Fluids containing water, various forms of carbohydrate such as glucose and fructose, and various electrolytes such as sodium, chloride, and potassium, in a solution designed to maintain optimal hydration and energy during exercise. See also sports drinks. carbohydrate loading A dietary method used by endurance-type athletes to help increase the carbohydrate (glycogen) levels in their muscles and liver. carcinogenicity The potential of a substance to cause cancer. carnitine A chemical that facilitates the transfer of fatty acids into the mitochondria for subsequent oxidation. carnosine A peptide found in muscle tissue theorized to possess ergogenic potential via its buffering effect on lactic acid during high intensity exercise; carnosine contains the nonessential amino acid beta-alanine. catabolism Destructive metabolism whereby complex chemical compounds in the body are degraded to simpler ones. catalase An enzyme that helps neutralize free radicals. cation A positively charged ion or electrolyte. cellulite A name given to the lumpy fat that often appears in the thigh and hip region of women. Cellulite is simply normal fat in small compartments formed by connective tissue, but may contain other compounds that bind water. cellulose The fibrous carbohydrate that provides the structural backbone for plants; plant fiber. Celsius A thermometer scale that has a freezing point of 0° and a boiling point of 100°; also known as the centigrade scale. central fatigue Fatigue caused by suboptimal functioning of neurotransmitters, most likely in the brain. cerebrospinal fluid (CSF) The fluid found in the brain and spinal cord. chloride A compound of chlorine present in a salt form carrying a negative charge; Cl–, an anion. cholecalciferol The product of irradiation of 7-dehydrocholesterol found in the skin. Also see vitamin D3. cholesterol A fat-like pearly substance, an alcohol, found in all animal fat and oils; a main constituent of some body tissues and body compounds.

choline A substance associated with the B complex that is widely distributed in both plant and animal tissues; involved in carbohydrate, fat, and protein metabolism. chondroitin Formed in the body from amino acids and involved in cartilage formation; marked as a dietary supplement. chromium A whitish metal essential to human nutrition; it is involved in carbohydrate metabolism via its role with insulin. chronic fatigue syndrome Prolonged fatigue (over 6 months) of unknown cause characterized by mental depression and physical fatigue; may be observed in endurance athletes. chronic training effect The structural and metabolic adaptations that occur in the body in response to exercise training over time; the adaptations are specific to the type of exercise, such as aerobic endurance training or resistance training. chylomicron A particle of emulsified fat found in the blood following the digestion and assimilation of fat. circuit aerobics A combination of aerobic and weight-training exercises designed to elicit the specific benefits of each type of exercise. circuit training A method of training in which exercises are arranged in a circuit or sequence. May be designed with weight training to help convey an aerobic training effect. cirrhosis A degenerative disease of the liver, one cause being excessive consumption of alcohol. cis fatty acids The chemical structure of unsaturated fatty acids in which the hydrogen ions are on the same side of the double bond. citrulline An amino acid that may be converted in the body to arginine and hypothesized to possess ergogenic potential; citrulline is not needed to form any body tissues. Ciwujia A chinese herb theorized to be ergogenic. clinical obesity Obesity determined by a clinical procedure. Clostridium A bacteria commonly involved in food poisoning. cobalamin The cobalt-containing complex common to all members of the vitamin B12 group; often used to designate cyanocobalamin. cobalt A gray, hard metal that is a component of vitamin B12. coenzyme An activator of an enzyme; many vitamins are coenzymes.

coenzyme Q10 See CoQ10. colon The large intestine. compensated heat stress A condition in which heat loss balances heat production, a set body temperature is maintained, and the individual can continue to exercise in warm environmental conditions. complementary proteins Combining plant foods such as rice and beans so that essential amino acids deficient in one of the foods are provided by the other in order to obtain a balanced intake of essential amino acids. complete protein A protein that contains all nine essential amino acids in the proper proportions. Animal protein is complete protein. complex carbohydrates A term used to describe foods high in starch, such as bread, cereals, fruits, and vegetables as contrasted to simple carbohydrates such as table sugar. concentric method A method of weight training in which the muscle shortens. conduction In relation to body temperature, the transfer of heat from one substance to another by direct contact. conjugated linoleic acid (CLA) Isomers of linoleic acid, an essential fatty acid. CLA is found in the meat and milk of ruminants, and is theorized to have health and exercise performance benefits, such as promotion of weight loss. convection In relation to body temperature, the transfer of heat by way of currents in either air or water. copper A reddish metallic element essential to human nutrition; it functions with iron in the formation of hemoglobin and the cytochromes. CoQ10 A coenzyme involved in the electron transport system in the mitochondria. core temperature The temperature of the deep tissues of the body, usually measured orally or rectally; also see shell temperature. Cori cycle Cycle involving muscle breakdown of glucose to lactate, lactate transport via blood to the liver for reconversion to glucose, and glucose returning to the muscle. coronary artery disease (CAD) Atherosclerosis in the coronary arteries. coronary heart disease (CHD) A degenerative disease of the heart caused primarily by arteriosclerosis or atherosclerosis of the coronary vessels of the heart. coronary occlusion Closure of coronary arteries that may precipitate a heart attack; occlusion may be partial or complete closure.

coronary risk factors Behaviors (smoking) or body properties (cholesterol levels) that may predispose an individual to coronary heart disease. coronary thrombosis Occlusion (closure) of coronary arteries, usually by a blood clot. cortisol A hormone secreted by the adrenal cortex with gluconeogenic potential, helping to convert amino acids to glucose. creatine A nitrogen-containing compound found in the muscles, usually complexed with phosphate to form phosphocreatine. crossover concept The concept that as exercise intensity increases, at some point carbohydrate rather than fat becomes the predominant fuel for muscle contraction. cruciferous vegetables Vegetables in the cabbage family, such as broccoli, cauliflower, kale, and all cabbages. cyanocobalamin Vitamin B12. cysteine A breakdown product of cystine. It is also a sulfur-containing amino acid. cystine A sulfur-containing amino acid. cytochromes Any one of a class of pigment compounds that play an important role in cellular oxidative processes. cytokine Cytokines are small proteins or peptides produced in cells, such as adipokines by adipose tissue cells that possess hormonelike functions on other cells in the body; the immune system secretes a number of different cytokines. Daily Reference Values (DRVs) The DRVs are recommended daily intakes for the macronutrients (carbohydrate, fat, and protein) as well as cholesterol, sodium, and potassium. On a food label, the DRV is based on a 2,000 Calorie diet. Daily Value (DV) A term used in food labeling; the DV is based on a daily energy intake of 2,000 Calories, and for the food labeled presents the percentage of the RDI and the DRV recommended for healthy Americans. See RDI and DRV. deamination Removal of an amine group, or nitrogen, from an amino acid. dehydration A reduction of the body water to below the normal level of hydration; water output exceeds water intake. dehydroepiandrosterone (DHEA) A natural steroid hormone produced endogenously by the adrenal gland. May be marketed as a nutritional sports ergogenic as derived from herbal precursors. delayed onset of muscle soreness (DOMS) DOMS represents the soreness in muscles experienced a day or two after strenuous eccentric exercise, such as running downhill.

Prolonged, excessive eccentric exercise may lead to small muscle tears, and the pain is believed to occur during the repair process when swelling activates pain receptors. depressant Drugs or agents that will depress or lower the level of bodily functions, particularly central nervous system functioning. DHAP Dihydroxyacetone and pyruvate, the combination of two by-products of glycolysis. DHEA See dehydroepiandrosterone. Diabesity Term coined to highlight the relationship between the development of diabetes following the onset of obesity. diabetes mellitus A disorder of carbohydrate metabolism due to disturbances in production or utilization of insulin; results in high blood glucose levels and loss of sugar in the urine. diarrhea Frequent passage of a watery fecal discharge due to a gastrointestinal disturbance. diastolic blood pressure The blood pressure in the arteries when the heart is at rest between beats. dietary fiber Nondigestible carbohydrates and lignin that are intrinsic and intact in plants. Dietary Folate Equivalents (DFE) Used in estimating folate requirements, adjusting for the greater degree of absorption of folic acid (free form) compared with folate naturally found in foods. One microgram food folate equals 0.5 to 0.6 folic acid added to foods or as a supplement. dietary-induced thermogenesis (DIT) The increase in the basal metabolic rate following the ingestion of a meal. Heat production is increased. Dietary Reference Intakes (DRI) Standards for recommended dietary intakes, consisting of various values. See also AI, EAR, RDA, AMDR, and UL. dietary supplement A food product, added to the total diet, that contains either vitamins, minerals, herbs, botanicals, amino acids, metabolites, constituents, extracts, or combinations of these ingredients. Dietary Supplement Health and Education Act (DSHEA) Act passed by the United States Congress defining a dietary supplement (see dietary supplement); legislation to control advertising and marketing. 2,3-diphosphoglyceride A by-product of carbohydrate metabolism in the red blood cell; helps the hemoglobin unload oxygen to the tissues. disaccharides Any one of a class of sugars that yield two monosaccharides on hydrolysis; sucrose is the most common. www.mhhe.com/williams9

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disordered eating Atypical eating behaviors such as restrictive dieting, using diet pills or laxatives, bingeing, and purging. In general, disordered eating behaviors occur less frequently or are less severe than those required to meet the full criteria for the diagnosis of an eating disorder. dispensable amino acids See nonessential animo acids. diuretics A class of agents that stimulate the formation of urine; used as a means to reduce body fluids. diverticulosis Weak spots in the wall of the large intestine that may bulge out like a weak spot in a tire inner tube. May become infected leading to diverticulitis. DNA Deoxyribonucleic acid; a complex protein found in chromosomes that is the carrier of genetic information and the basis of heredity. docasahexanoic acid (DHA) Docasahexanoic acid, an omega-3 fatty acid found in fatty fish. doping Official term used by WADA and the International Olympic Committee to depict the use of drugs in sports in attempts to enhance performance. doubly-labeled water technique A technique using labeled water to study energy metabolism. dual energy X-ray absorptiometry (DEXA, DXA) A computerized X-ray technique at two energy levels to image body fat, lean tissues, and bone mineral content. dumping syndrome Movement of fluid from the blood to the intestines by osmosis. May occur when a concentrated sugar solution is consumed in large quantities, causing symptoms such as weakness and gastrointestinal distress. duration concept One of the major concepts of aerobic exercise; duration refers to the amount of time spent exercising during each session. EAH See exercise-associated hyponatremia. eating disorder A psychological disorder centering on the avoidance, excessive consumption, or purging of food, such as anorexia nervosa and bulimia nervosa. eccentric method A weight-training method in which the muscle undergoes a lengthening contraction. eicosanoids Derivatives of fatty acid oxidation in the body, including prostaglandins, thromboxanes, and leukotrienes. eicosapentaenoic acid (EPA) An omega-3 fatty acid found in fatty fish. 606

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electrolyte A substance that, when in a solution, conducts an electric current. electrolyte solution A solution that contains ions and can conduct electricity; often the ions of salts such as sodium and chloride are called electrolytes; also see ions. electron transfer system A highly structured array of chemical compounds in the cell that transport electrons and harness energy for later use. element Relative to chemistry, a substance that cannot be subdivided into substances different from itself; many elements are essential to human life. endocrine system The body system consisting of glands that secrete hormones, which have a wide variety of effects throughout the body. energy The ability to do work; energy exists in various forms, notably mechanical, heat, and chemical in the human body. English system A measurement system based upon the foot, pound, quart, and other nonmetric units; also see metric system. enzyme A complex protein in the body that serves as a catalyst, facilitating reactions between various substances without being changed itself. Ephedra Term used for the plant Ephedra sinica, a source of ephedrine. ephedrine A stimulant with somewhat weaker effects than amphetamine; found in some commercial dietary supplements; also known as ephedra. epidemiological research A study of certain populations to determine the relationship of various risk factors to epidemic diseases or health problems. epinephrine A hormone secreted by the adrenal medulla that stimulates numerous body processes to enhance energy production, particularly during intense exercise. epithelial cells The layer of cells that covers the outside and inside surfaces of the body, including the skin and the lining of the gastrointestinal system. ergogenic aids Work-enhancing agents that are used in attempts to increase athletic or physical performance capacity. ergogenic effect The physiological or psychological effect that an ergogenic substance is designed to produce. ergolytic effect An agent or substance that may lead to decreases in work productivity or physical performance. See also ergogenic effect. ergometer A device, such as a cycle ergometer, to measure work output in watts or other measures of work.

Escherichia A bacteria commonly involved in food poisoning. essential amino acids Those amino acids that must be obtained in the diet and cannot be synthesized in the body. Also known as indispensable amino acids. essential fat Fat in the body that is an essential part of the tissues, such as cell membrane structure, nerve coverings, and the brain; also see storage fat. essential fatty acid Those unsaturated fatty acids that may not be synthesized in the body and must be obtained in the diet, e.g., linoleic fatty acid. essential nutrients Those nutrients found to be essential to human life and optimal functioning. ester Compound formed from the combination of an organic acid and an alcohol. Estimated Average Requirement (EAR) Nutrient intake value estimated to meet the requirements of half the healthy individuals in a group. Estimated Energy Requirement (EER) The daily dietary intake predicted to maintain energy balance for an individual of a defined age, gender, height, weight, and level of physical activity consistent with good health. Estimated Minimal Requirement (EMR) Part of the RDA pertaining to the minimal daily requirement for sodium, chloride, and potassium. Estimated Safe and Adequate Daily Dietary Intakes (ESADDI) Part of the previous RDA. Daily allowances for selected nutrients that are based upon available scientific evidence to be safe and adequate to meet human needs. ethanol Alcohol; ethyl alcohol. ethyl alcohol Alcohol; ethanol. evaporation The conversion of a liquid to a vapor, which consumes energy; evaporation of sweat cools the body by using body heat as the energy source. exercise A form of structured physical activity generally designed to enhance physical fitness; exercise usually refers to strenuous physical activity. exercise-associated hyponatremia (EAH) Term associated with the decline in serum sodium levels during prolonged exercise with excessive fluid intake and/or sodium losses; also see water intoxication. exercise frequency In an aerobic exercise program, the number of times per week that an individual exercises. exercise intensity The tempo, speed, or resistance of an exercise. Intensity can be

increased by working faster, doing more work in a given amount of time. exercise metabolic rate (EMR) An increased metabolic rate due to the need for increased energy production; during exercise, the resting energy expenditure (REE) may be increased more than twenty-fold. exercisenomics General term regarding the effects of exercise on genetic expression and resultant metabolic adaptations. exercise sequence See principle of exercise sequence. exercise stimulus The means whereby one elicits a physiological response; running, for example, can be the stimulus to increase the heart rate and other physiological functions. exertional heat stroke Heat stroke that is precipitated by exercise in a warm or hot environment. experimental research Study that manipulates an independent variable (cause) to observe the outcome on a dependent variable (effect). extracellular water Body water that is located outside the cells; often subdivided into the intravascular water and the intercellular, or interstitial, water. facilitated diffusion Process whereby glucose combines with a special protein carrier molecule at the membrane surface, facilitating glucose transport into the cell; insulin promotes facilitated diffusion in some cells. faddism Relative to nutrition, the use of dietary fads based upon theoretical principles that may or may not be valid; usually used in a negative sense, as in quackery. fasting Starvation; abstinence from eating that may be partial or complete. fast-twitch fibers Muscle fibers characterized by high contractile speed. fat exchange A fat exchange in the Food Exchange System contains 5 grams of fat and 45 Calories. fat-free mass The remaining mass of the human body following the extraction of all fat. fatigue A generalized or specific feeling of tiredness that may have a multitude of causes; may be mental or physical. fat loading A term to describe practices used to maximize the use of fats as an energy source during exercise, particularly a lowcarbohydrate, high-fat diet. fat patterning The deposition of fat in specific areas of the human body, such as the stomach, thighs, or hips. Genetics plays an important role in fat patterning. fats Triglycerides; a combination, or ester, of three fatty acids and glycerol.

fat substitutes Various substances used as substitutes for fats in food products; two popular brands are Simplesse and Olestra. fatty acids Any one of a number of aliphatic acids containing only carbon, oxygen, and hydrogen; they may be saturated or unsaturated. female athlete triad The triad of disordered eating, amenorrhea, and osteoporosis sometimes seen in female athletes involved in sports where excess body weight may be detrimental to performance. female-type obesity See gynoid-type obesity. ferritin The form in which iron is stored in the tissues. fetal alcohol effects (FAE) Symptoms noted in children born to women who consumed alcohol during pregnancy; not as severe as fetal alcohol syndrome. Fetal Alcohol Spectrum Disorders (FASD) FASD is the term used to describe birth anomalies associated with drinking alcohol while pregnant, and refers to several conditions involving alcohol-related neurodevelopment disorders, birth defects, and other abnormalities in normal development. See also fetal alcohol syndrome and fetal alcohol effects. fetal alcohol syndrome (FAS) The cluster of physical and mental symptoms seen in the child of a mother who consumes excessive alcohol during pregnancy. fiber In general, the indigestible carbohydrate in plants that forms the structural network; also see cellulose. First Law of Thermodynamics The law that energy cannot be created or destroyed; energy can be converted from one form to another. flatulence Gas or air in the gastrointestinal tract, particularly the intestines. fluoride A salt of hydrofluoric acid; a compound of fluorine that may be helpful in the prevention of tooth decay. folacin Collective term for various forms of folic acid. folate Salt of folic acid; form found in foods. folic acid A water-soluble vitamin that appears to be essential in preventing certain types of anemia. food additives See additives. food allergy An adverse immune response to an otherwise harmless food. Also see food hypersensitivity. food cultism Treating a particular food as if it possesses special properties, such as prevention or treatment of disease or

improvement of athletic performance, usually without scientific justification. Food and Drug Administration (FDA) Federal agency tasked with the responsibilities to monitor safety of foods and drugs sold in the United States. Food Exchange System The system developed by the American Dietetic Association and other health groups that categorizes foods by content of carbohydrate, fat, protein, and Calories. Used as a basis for diet planning. food hypersensitivity Some individuals may develop clinical symptoms, such as migraine headaches, gastrointestinal distress, or hives and itching when certain foods are eaten. food intolerance A general term for any adverse reaction to a food or food component not involving the immune system; an example is lactose intolerance. food poisoning Foodborne illness caused by bacteria such as Salmonella, Escherichia, Staphylococcus, and Clostridium. foot-pound A unit of work whereby the weight of 1 pound is moved through a distance of 1 foot. Fosamax A commercial bisphosphonate product. free fatty acids (FFA) Acids formed by the hydrolysis of triglycerides. free radicals An atom or compound in which there is an unpaired electron. Thought to cause cellular damage. fructose A monosaccharide known as levulose or fruit sugar; found in all sweet fruits. fruitarian A type of vegetarian who subsides solely on fruits, fruit products, and nuts. fruit exchange One fruit exchange in the Food Exchange System contains 15 grams of carbohydrate and 60 Calories. fTRP:BCAA ratio The ratio of free tryptophan to branched-chain amino acids; a high ratio is theorized to elicit fatigue in prolonged endurance events. functional fiber Isolated, nondigestible carbohydrates that have beneficial effects in humans. functional foods Food products containing nutrients designed to provide health benefits beyond basic nutrition. galactose A monosaccharide formed when lactose is hydrolyzed into glucose and galactose. gastric emptying The rate at which substances, particularly fluids, empty from the www.mhhe.com/williams9

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stomach; high gastric emptying rates are advisable for sports drinks. generally recognized as safe (GRAS) A classification for food additives indicating that they most likely are not harmful for human consumption. genomics The study of the entire genome of an individual or organism; human genomics attempts to determine DNA sequence and gene mapping. Human genomic research may lead to genetic modifications to enhance health of individuals; genomics may also be involved in gene doping, or sport performance enhancement with gene manipulation. ghrelin Hormone released by an empty stomach to stimulate the appetite. ginseng A general term for a variety of natural chemical plant extracts derived from the family Araliaceae; extract contains ginsenosides and other chemicals that may influence human physiology. glucagon A hormone secreted by the pancreas; basically it exerts actions just the opposite of insulin, i.e., it responds to hypoglycemia and helps to increase blood sugar levels. glucarate A compound found in cruciferous vegetables that is thought to block the actions of cancer-causing agents. glucogenic amino acids Amino acids that may undergo deamination and be converted into glucose through the process of gluconeogenesis. gluconeogenesis The formation of carbohydrates from molecules that are not themselves carbohydrate, such as amino acids and the glycerol from fat. glucosamine Formed in the body from amino acids and involved in cartilage formation; marketed as a dietary supplement. glucose A monosaccharide; a thick, sweet, syrupy liquid. glucose-alanine cycle The cycle in which alanine is released from the muscle and is converted to glucose in the liver. glucose-electrolyte solutions Solutions designed to replace sweat losses; contain varying proportions of water, glucose, sodium, potassium, chloride, and other electrolytes. glucose polymer A combination of several glucose molecules into a more complex carbohydrate. glucostatic theory The theory that hunger and satiety are controlled by the glucose level in the blood; the receptors that respond to the blood glucose level are in the hypothalamus. GLUT-4 Receptors in cell membranes that transport glucose from the blood to the cell interior. 608

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glutathione peroxidase An enzyme that helps neutralize free radicals. gluten intolerance A sensitivity to gluten; the immune system recognizes gluten as a foreign substance, but does not induce an allergic response. glycemic index (GI) The GI represents a ranking system relative to the effect that consumption of 50 grams of a particular carbohydrate food has upon the blood glucose response over the course of 2 hours. The normal baseline measure is 50 grams of glucose, and the resultant blood glucose response is scored as 100. glycemic load (GL) The GL represents a ranking system relative to the effect that eating a carbohydrate food has on the blood glucose level, but also includes the portion size. The formula is: (GI) × (grams of non-fiber carbohydrate in one serving) GL = 100 Glycerate A commercial product containing glycerol; marketed to athletes. glycerin See glycerol. glycerol Glycerin, a clear syrupy liquid; an alcohol that combines with fatty acids to form triglycerides. glycogen A polysaccharide that is the chief storage form of carbohydrate in animals; it is stored primarily in the liver and muscles. glycogen-sparing effect The theory that certain dietary techniques, such as the use of caffeine, may facilitate the oxidation of fatty acids for energy and thus spare the utilization of glycogen. glycolysis The degradation of sugars into smaller compounds; the main quantitative anaerobic energy process in the muscle tissue. gout The deposit of uric acid by-products in and about the joints contributing to inflammation and pain; usually occurs in the knee or foot. gram calorie A small calorie; see Calorie. green tea Green tea is a Chinese beverage that contains caffeine and other constituents, such as epigallocatechin gallate (EGCG), which are theorized to possess numerous health benefits. gums A form of water-soluble dietary fiber found in plants. gynoid-type obesity Female-type obesity; body fat is deposited primarily about the hips and thighs. Also see android-type obesity. HDL High-density lipoprotein; a proteinlipid complex in the blood that facilitates the transport of triglycerides, cholesterol, and phospholipids. Also see HDL-cholesterol.

HDL-cholesterol High-density lipoprotein cholesterol; one mechanism whereby cholesterol is transported in the blood. High HDL levels are somewhat protective against CHD. health-related fitness Those components of physical fitness whose improvement have health benefits, such as cardiovascular fitness, body composition, flexibility, and muscular strength and endurance. Healthy Eating Index (HEI) USDA computerized dietary analysis to assess personal diets to provide an overall rating as related to health. heat-balance equation Heat balance is dependent upon the interrelationships of metabolic heat production and loss or gain of heat by radiation, convection, conduction, and evaporation. heat cramps Painful muscular cramps or tetany following prolonged exercise in the heat without water or salt replacement. heat exhaustion Weakness or dizziness from overexertion in a hot environment. heat index The apparent temperature determined by combining air temperature and relative humidity. heat stroke Elevated body temperature of 105.8°F or greater caused by exposure to excessive heat gains or production and diminished heat loss. heat syncope Fainting caused by excessive heat exposure. hematuria Blood or red blood cells in the urine. heme iron The iron in the diet associated with hemoglobin in animal meats. hemicellulose A form of dietary fiber found in plants. Differs from cellulose in that it may be hydrolyzed by dilute acids outside of the body. Not hydrolyzed in the body. hemochromatosis Presence of excessive iron in the body resulting in an enlarged liver and bronze pigmentation of the skin. hemoglobin The protein-iron pigment in the red blood cells that transports oxygen. hemolysis A rupturing of red blood cells with a release of hemoglobin into the plasma. hepatitis An inflammatory condition of the liver. heterocyclic amines (HCA) Carcinogens formed in foods that have been charred by excess grilling or broiling. hidden fat In foods, the fat that is not readily apparent, such as the high fat content of cheese. high blood pressure See hypertension.

high-density lipoprotein See HDL. high-fructose corn syrup A common highCalorie sweetener used as a food additive; derived from the partial hydrolysis of corn starch. histidine An essential amino acid. HMB Beta-hydroxy-beta-methylbutyrate, a metabolic by-product of the amino acid leucine, alleged to retard the breakdown of muscle protein during strenuous exercise. homeostasis A term used to describe a condition of normalcy in the internal body environment. homocysteine A metabolic by-product of amino acid metabolism; elevated blood levels are associated with increased risk of vascular diseases. hormone A chemical substance produced by specific body cells, secreted into the blood and then acting on specific target tissues. hormone sensitive lipase (HSL) An enzyme that catalyzes triglycerides into free fatty acids and glycerol. HR max The normal maximal heart rate of an individual during exercise. HR reserve The mathematical difference, or reserve, between the resting HR and maximal HR. A percentage of this reserve may be added to the resting HR to determine exercise intensity. human growth hormone (HGH) A hormone released by the pituitary gland that regulates growth; also involved in fatty acid metabolism; rHGH is a genetically engineered form. hunger A basic physiological desire to eat that is normally caused by a lack of food; may be accompanied by stomach contractions. hunger center A collection of nerve cells in the hypothalamus that is involved in the control of feeding reflexes. hydrodensitometry Another term for the underwater weighing technique. hydrogenated fats Fats to which hydrogen has been added, usually causing them to be saturated. hydrolysis A mechanism for splitting substances into smaller compounds by the addition of water; enzyme action. hypercholesteremia Elevated blood cholesterol levels. hyperglycemia Elevated blood glucose levels. hyperhydration The practice of increasing the body-water stores by fluid consumption prior to an athletic event; a state of increased water content in the body.

hyperkalemia An increased concentration of potassium in the blood. hyperlipidemia Elevated blood lipid levels. hyperplasia The formation of new body cells. hypertension A condition with various causes whereby the blood pressure is higher than normal. hyperthermia Unusually high body temperature; fever. hypertonic Relative to osmotic pressure, a solution that has a greater concentration of solute or salts, hence higher osmotic pressure, in comparison to another solution. hypertriglyceridemia Elevated blood levels of triglycerides. hypertrophy Excessive growth of a cell or organ; in pathology, an abnormal growth. hypervitaminosis A pathological condition due to an excessive vitamin intake, particularly the fat-soluble vitamins A and D. hypoglycemia A low blood sugar level. hypohydration A state of decreased water content in the body caused by dehydration. hypokalemia A decreased concentration of potassium in the blood. hyponatremia A decreased concentration of sodium in the blood. hypothalamus A part of the brain involved in the control of involuntary activity in the body; contains many centers for neural control such as temperature, hunger, appetite, and thirst. hypothermia Unusually low body temperature. hypotonic Having an osmotic pressure lower than that of the solution to which it is compared. IGF-1 See insulin-like growth factor. incomplete protein Protein food that does not possess the proper amount of essential amino acids; characteristic of plant foods in general. Index of Nutritional Quality (INQ) A mathematical means of determining the quality of any given food relative to its content of a specific nutrient. indicator nutrients These eight nutrients, if provided in adequate supply through a varied diet, should provide adequate amounts of the other essential nutrients. The eight are protein, vitamin A, thiamin, riboflavin, niacin, vitamin C, calcium, and iron. indispensable amino acids See essential amino acids. indoles Phytochemicals believed to help prevent various diseases. infrared interactance Use of infrared technology to estimate body composition.

initial fitness level The physical fitness level of an individual prior to the onset of a physical conditioning program. in-line skating An exercise-skating technique with specially designed shoes for use on sidewalks and similar surfaces. inosine A nucleoside of the purine family that serves as a base for the formation of a variety of compounds in the body; theorized to be ergogenic. inositol A member of the B complex, although its role in human nutrition has not been established; not classified as a vitamin. INQ See Index of Nutritional Quality. insensible perspiration Perspiration on the skin not detectable by ordinary senses. insoluble dietary fiber Dietary fiber that is not soluble in water, such as cellulose. Also see soluble dietary fiber. insulin A hormone secreted by the pancreas involved in carbohydrate metabolism. Insulin-like growth factor (IGF-1) A growth factor found in the blood which resembles insulin; produced in response to growth hormone release. insulin response Blood insulin levels rise following the ingestion of sugar and the resultant hyperglycemia; the insulin causes the sugar to be taken up by the muscles and fat cells, possibly creating a reactive hypoglycemia. intercellular water Body water found between the cells; also known as interstitial water. intermittent high-intensity exercise Short-term bouts of high-intensity exercise interspersed with short periods of recovery. International Unit (IU) A method of expressing the quantity of some substance, such as vitamins, which is an internationally developed and accepted standard. International Unit System (SI) Le Systeme International d’Unite, or the International System of Units; a system of measurement based upon the metric system. interstitial water See intercellular water. interval training A method of physical training in which periods of activity are interspersed with periods of rest. intestinal absorption The rate at which substances, particularly fluids and nutrients, are absorbed into the body; a fast rate of intestinal absorption is a desirable characteristic of sports drinks. intracellular water Body water that is found within the cells. www.mhhe.com/williams9

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intravascular water Body water found in the vascular system, or blood vessels. involuntary dehydration Unintentional loss of body fluids during exercise under warm or hot environmental conditions. IOC International Olympic Committee. iodine A nonmetallic element that is necessary for the proper development and functioning of the thyroid gland. ions Particles with an electrical charge; anions are negative and cations are positive. iron A metallic element essential for the development of several chemical compounds in the body, notably hemoglobin. iron-deficiency anemia Anemia caused by an inadequate intake or absorption of iron, resulting in impaired hemoglobin formation. iron deficiency without anemia A condition in which the hemoglobin levels are normal but several indices of iron status in the body are below normal levels. irradiation Process whereby foods are subjected to ionizing radiation to kill bacteria. ischemia Lack of blood supply. isoflavones Phytochemicals believed to help prevent various diseases. isokinetic Literally meaning “same speed”; in weight training an isokinetic machine is used to control the speed of muscle contraction. isoleucine An essential amino acid. isometric Literally meaning “same length”; in weight training the resistance is set so that the muscle will not shorten. isotonic Literally meaning “equal tension or pressure”; in weight training the resistance is set so there is supposed to be equal tension in the muscle through a range of motion, but this is rarely achieved owing to movement of body parts. Isotonic also means equal osmotic pressures between two solutions. jogging A term used to designate slow running; although the distinction between running and jogging is relative to the individual involved, a common value used for jogging is a 9-minute mile or slower. joule A measure of work in the metric system; a newton of force applied through a distance of one meter. ketogenesis The formation of ketones in the body from other substances, such as fats and proteins. ketogenic amino acids Amino acids that may be deaminated, converted into ketones, and eventually into fat.

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ketones An organic compound containing a carbonyl group; ketone acids in the body, such as acetone, are the end products of fat metabolism. ketosis The accumulation of excess ketones in the blood; since ketones are acids, acidosis occurs. key-nutrient concept The concept that if certain key nutrients are adequately supplied by the diet, the other essential nutrients will also be present in adequate amounts. Also see indicator nutrients. kidney stones Compounds in the pelvis of the kidney formed from various salts such as carbonates, oxalates, and phosphates. kilocalorie (KC) A large Calorie; see Calorie. kilogram A unit of mass in the metric system; in ordinary terms, 1 kilogram is the equivalent of 2.2 pounds. kilogram-meter (KGM) A measure of work in the metric system whereby 1 kilogram of weight is moved through a distance of 1 meter; however, the joule is the recommended unit to express work. kilojoule One thousand joules; one kilojoule (kJ) is approximately 0.25 kilocalorie. Krebs cycle The main oxidative reaction sequence in the body that generates ATP; also known as the citric acid or tricarboxylic acid cycle. lactic acid The anaerobic end product of glycolysis; it has been implicated as a causative factor in the etiology of fatigue. lactic acid system The energy system that produces ATP anaerobically by the breakdown of glycogen to lactic acid; used primarily in events of maximal effort for one to two minutes. lactose A white crystalline disaccharide that yields glucose and galactose upon hydrolysis; also known as milk sugar. lactose intolerance Gastrointestinal disturbances due to an intolerance to lactose in milk; caused by deficiency of lactase, an enzyme that digests lactose. lactovegetarian A vegetarian who includes milk products in the diet as a form of highquality protein. LDL Low-density lipoprotein; a proteinlipid complex in the blood that facilitates the transport of triglycerides, cholesterol, and phospholipids. Also see LDL-cholesterol. LDL-cholesterol Low-density lipoprotein cholesterol; a mechanism whereby cholesterol is transported in the blood. High blood levels are associated with increased incidence of CHD.

lean body mass The body weight minus the body fat, composed primarily of muscle, bone, and other nonfat tissue. lecithin A fatty substance of a class known as phospholipids; said to have the therapeutic properties of phosphorous. legume The fruit or pod of vegetables including soybeans, kidney beans, lima beans, garden peas, black-eyed peas, and lentils; high in protein. leptin Regulatory hormone produced by fat cells; when released into the circulation, it influences the hypothalamus to control appetite. leucine An essential amino acid. leukotrienes Eicosanoids that possess hormone-like activity in numerous cells in the body. levulose Fructose. lignin A noncarbohydrate form of dietary fiber. limiting amino acid An amino acid deficient in a specific plant food, making it an incomplete protein; methionine is a limiting amino acid in legumes while lysine is deficient in grain products. linoleic acid An essential fatty acid. lipase An enzyme that catabolizes fats into fatty acids and glycerol. lipids A class of fats or fat-like substances characterized by their insolubility in water and solubility in fat solvents; triglycerides, fatty acids, phospholipids, and cholesterol are important lipids in the body. lipoic acid A coenzyme that functions in oxidative decarboxylation, or removal of carbon dioxide from a compound. lipoprotein A combination of lipid and protein possessing the general properties of proteins. Practically all the lipids of the plasma are present in this form. lipoprotein (a) Serum lipid factor very similar to the LDL, being in the upper LDL density range and containing apolipoprotein (a); high levels are associated with increased risk for CHD. lipoprotein lipase An enzyme involved in the metabolism of lipoproteins. lipostatic theory The theory that hunger and satiety are controlled by the lipid level in the blood. liquid meals Food in a liquid form designed to provide a balanced intake of essential nutrients. liquid-protein diets Protein in a liquid form; a common form consists of protein predigested into simple amino acids.

liver glycogen The major storage form of carbohydrate in the liver. long-chain fatty acids (LCFA) Fatty acids containing chains with 12 or more carbons. long-haul concept Relative to weight control, the idea that weight loss via exercise should be gradual, and one should not expect to lose large amounts of weight in a short time. L-tryptophan One form of tryptophan. L is for levo (left), or the direction in which polarized light is rotated when various organic compounds are analyzed. lycopene A carotenoid that serves as an antioxidant. lysine An essential amino acid. macrominerals Those minerals essential to human nutrition with an RDA in excess of 100 mg/day: calcium, magnesium, phosphorous, sodium, potassium, chloride. macronutrients Dietary nutrients needed by the body in daily amounts greater than a few grams, such as carbohydrate, fat, protein, and water. magnesium A white metallic mineral element essential in human nutrition. magnetic resonance imaging (MRI) Magnetic-field and radio-frequency waves used to image body tissues; useful for imaging visceral fat. ma huang A Chinese plant extract theorized to be ergogenic; contains ephedrine, a stimulant. major minerals See macrominerals. male-type obesity See android-type obesity. malnutrition Poor nutrition that may be due to inadequate amounts of essential nutrients. Too many Calories leading to obesity is also a form of malnutrition. Also see subclinical malnutrition. maltodextrin A glucose polymer that exerts lesser osmotic effects compared with glucose; used in a variety of sports drinks as the source of carbohydrate. maltose A white crystalline disaccharide that yields two molecules of glucose upon hydrolysis. manganese A metallic element essential in human nutrition. maximal heart rate See HR max. maximal heart rate reserve The difference between the maximal HR and resting HR. A percentage of this reserve, usually 60–90 percent, is added to the resting HR to get the target HR for aerobics training programs. maximal oxygen uptake See VO2 max. meat exchange One very lean meat exchange in the Food Exchange System

contains 0–1 gram of fat, 7 grams of protein, and 35 Calories; a lean meat exchange contains 3 grams of fat, 7 grams of protein, and 55 Calories; a medium-fat meat exchange has an additional 2 grams of fat and totals 75 Calories; a high-fat exchange has 5 additional grams of fat and totals 100 Calories. Mediterranean diet A diet associated with reduced risk of cardiovascular disease attributed to olive oil, the primary source of dietary fat. However, other elements of the Mediterranean diet, such as seafood and vegetables, may also be associated with reduced CHD risk. Mediterranean Food Guide Pyramid A food group approach to healthful nutrition that includes basic food groups, but also lists olive oil and wine as components of the diet. medium-chain fatty acids (MCFA) Fatty acids containing chains with 6–12 carbons. medium-chain triglycerides (MCTs) Triglycerides containing fatty acids with carbon chain lengths of 6–12 carbons. megadose An excessive amount of a substance in comparison to a normal dose of RDA; usually used to refer to vitamins. menadione Vitamin K3. menoquinone The animal form of vitamin K. MET A measurement unit of energy expenditure; one MET equals approximately 3.5 ml O2/kg body weight/minute. meta-analysis A statistical technique to summarize the findings of numerous studies in an attempt to provide a quantitatively based conclusion. metabolic aftereffects of exercise The theory that the aftereffects of exercise will cause the metabolic rate to be elevated for a time, thus expending Calories and contributing to weight loss. metabolic rate The energy expended to maintain all physical and chemical changes occurring in the body. metabolic syndrome The syndrome of symptoms often seen with android-type obesity, particularly hyperinsulinemia, hypertriglyceridemia, and hypertension. metabolic water The water that is a byproduct of the oxidation of carbohydrate, fat, and protein in the body. metabolism The sum total of all physical and chemical processes occurring in the body. metalloenzyme An enzyme that needs a mineral component, such as zinc, in order to function effectively. methionine An essential amino acid.

methylmercury An industrial waste product dumped in the seas that may accumulate in large fish; may lead to subsequent nerve damage in children or pregnant females who eat contaminated fish. metric system A method of measurement based upon units of ten. microgram One millionth of a gram (µg). micronutrients Dietary nutrients needed by the body in daily amounts less than a few grams, such as vitamins and minerals. milk exchange One skim milk exchange in the Food Exchange System contains 12 grams of carbohydrate, 8 grams of protein, a trace of fat, and 90 Calories. A low-fat exchange contains 120 Calories whereas whole milk has 150 Calories. milligram One thousandth of a gram. millimole One thousandth of a mole. mineral An inorganic element occurring in nature. mitochondria Structures within the cells that serve as the location for the aerobic production of ATP. mole One mole is the gram molecular weight of a compound, which is the quantity of a substance that equals its molecular weight. molybdenum A hard, heavy, silvery-white metallic element. monosaccharides Simple sugars (glucose, fructose, and galactose) that cannot be broken down by hydrolysis. monounsaturated fatty acids (MUFA) Fatty acids that have a single double bond. morbid obesity Severe obesity in which the incidence of life-threatening diseases is increased significantly. MPF factor Muscle protein factor; an unknown property of meat, fish, and poultry that facilitates the absorption of nonheme iron found in plant foods. muscle dysmorphia See Adonis complex. muscle glycogen The form in which carbohydrate is stored in the muscle. muscle hypertrophy An increase in the size of the muscle. myocardial infarction Death of heart tissue following cessation of blood flow; may be caused by coronary occlusion. myoglobin An iron-containing compound, similar to hemoglobin, found in the muscle tissues; it binds oxygen in the muscle cells. MyPyramid The graphic and program representing the healthful food guidelines presented by the United States Department of Agriculture.

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narcotic Any agent that produces insensibility to pain. National Weight Control Registry A registry of individuals who have lost at least 30 pounds and have kept if off for a year. Nautilus A brand of exercise equipment designed for strength-training programs; uses a principle to help provide optimal resistance throughout the full range of motion. NCAA National Collegiate Athletic Association. negative caloric balance A condition whereby the caloric output exceeds the caloric intake, thus contributing to a weight loss. negative nitrogen balance A condition in which dietary protein is insufficient to meet the nitrogen needs of the body. More nitrogen is excreted than is retained in the body. net protein utilization (NPU) A technique used to assess protein quality. neural tube defects (NTD) Birth defects involving incomplete formation of the neural tube in the spinal column of newborn children; may lead to paralysis; may be prevented by adequate folate intake. neuropeptide Y (NPY) Neuropeptide produced in the hypothalamus; a potent appetite stimulant. neutron activation analysis A sophisticated, noninvasive method of analyzing body structure and function. newton A unit of force that will accelerate 1 kilogram of mass 1 meter per second. niacin Nicotinamide; nicotinic acid; part of the B complex and an important part of several coenzymes involved in aerobic energy processes in the cells. niacin equivalent A unit of measure of niacin activity in a food related to both the amount of niacin present and that obtainable from tryptophan; about 60 mg tryptophan can be converted to 1 mg niacin. nickel A silvery-white metallic element. nicotinamide An amide of nicotinic acid; niacin. nicotinic acid Niacin. nitrogen A colorless, tasteless, odorless gas comprising about 80 percent of the atmospheric gas; an essential component of protein that is formed in plants during their developmental process. nitrogen balance A dietary state in which the input and output of nitrogen is balanced so that the body neither gains nor loses protein tissue. nonessential amino acids Amino acids that may be formed in the body and thus need not be obtained in the diet; also known as 612

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dispensable amino acids. See essential amino acids. nonessential nutrient A nutrient that may be formed in the body from excess amounts of other nutrients. nonexercise activity thermogenesis (NEAT) Thermogenesis, or heat production by the body, that accompanies physical activity other than volitional exercise. nonheme iron Iron that is found in plant foods; see heme iron. nonprotein nitrogen Nitrogen in the body and foods that is associated with nonprotein compounds. normohydration The state of normal hydration, or normal body-water levels, as compared with hypohydration and hyperhydration. nutraceutical A nutrient that may function as a pharmaceutical when taken in certain quantities. nutrient Substances found in food that provide energy, promote growth and repair of tissues, and regulate metabolism. nutrient density A concept related to the degree of concentration of nutrients in a given food; also see the related concept INQ. nutrigenomics General term regarding the effects of nutrition on genetic expression and resultant metabolic adaptions. nutrition The study of foods and nutrients and their effect on health, growth, and development of the individual. nutritional labeling A listing of selected key nutrients and Calories on the label of commercially prepared food products. obesity An excessive accumulation of body fat; usually reserved for those individuals who are 20–30 percent or more above the average weight for their size. octacosanol A solid white alcohol found in wheat germ oil. odds ratio (OR) A probability estimate; OR of 1.0 is normal. Olestra A commercially produced substitute for dietary fat. oligomenorrhea Intermittent periods of amenorrhea. omega-3 fatty acids Polyunsaturated fatty acids that have a double bond between the third and fourth carbon from the terminal, or omega, carbon. EPA and DHA found in fish oils are theorized to prevent coronary heart disease. OmniHeart diet The Optimal MacroNutrient Intake diet, consisting of healthy carbohydrates, healthy fats, and healthy proteins designed to reduce risks of

cardiovascular disease, particularly high blood pressure. onset of blood lactic acid (OBLA) The intensity level of exercise at which the blood lactate begins to accumulate rapidly. oral contraceptives Birth control pills used to prevent conception. oral rehydration therapy (ORT) Fluids balanced in nutrients that help restore normal hydration levels in the body and prevent excessive dehydration. organic foods Foods that are stated to be grown without the use of man-made chemicals such as pesticides and artificial fertilizers. orlistat A prescription drug for weight loss that blocks the digestion of dietary fat. osmolality Osmotic concentration determined by the ionic concentration of the dissolved substance per unit of solvent. osmoreceptors Receptors in the body that react to changes in the osmotic pressure of the blood. osmotic pressure A pressure that produces a diffusion between solutions that have different concentrations. osteomalacia A disease characterized by softening of the bones, leading to brittleness and increased deformity; caused by a deficiency of vitamin D. osteoporosis Increased porosity or softening of the bone. overload principle See principle of overload. overtraining syndrome Symptoms associated with excessive training, such as tiredness, sleeplessness, and elevated heart rate. overweight Body weight greater than that which is considered normal; also see obesity. ovolactovegetarian A vegetarian who also consumes eggs and milk products as a source of high-quality animal protein. ovovegetarian A vegetarian who includes eggs in the diet to help obtain adequate amounts of protein. oxalates Salts of oxalic acid, which are found in green leafy vegetables such as spinach and beet greens. oxidized LDL An oxidized form of lowdensity lipoprotein that has increased atherogenic potential. oxygen consumption The total amount of oxygen utilized in the body for the production of energy; it is directly related to the metabolic rate. oxygen system The energy system that produces ATP via the oxidation of various foodstuffs, primarily fats and carbohydrates.

paidotribe Individuals who served as personal trainers in ancient Greece to advise athletes on proper diet and exercise training programs. pangamic acid A term often associated with “vitamin B15,” the essentiality of which has not been established; often contains calcium gluconate and dimethylglycine. pantothenic acid A vitamin of the B complex. para-aminobenzoic acid (PABA) Although not a vitamin, often grouped with the B complex. partially hydrogenated fats Polyunsaturated fats that are not fully saturated with hydrogen through a hydrogenation process; also see trans fatty acids. peak bone mass The concept of maximizing the amount of bone mineral content during the formative years of childhood and young adulthood. pectin A form of soluble dietary fiber found in some fruits. pellagra A deficiency disease caused by inadequate amounts of niacin in the diet. pentose A simple sugar containing five carbons instead of six as in glucose. peptides Small compounds formed by the union of two or more amino acids; known also as dipeptides, tripeptides, and so on, depending upon the number of amino acids combined. perceptual-motor activities Physical activities characterized by the perception of a given stimulus and culminating in an appropriate motor, or movement, response. periodization A technique applied to resistance training, as well as other forms of exercise training, that modifies the amount of exercise stress placed on the individual over the course of time. Various cycles, such as the microcycle, mesocycle, and macrocycle, are designed to allow the body to adapt to exercise stress in ways beneficial to performance enhancement. peripheral vascular disease Atherosclerosis or blockage of the peripheral arteries. pernicious anemia A severe progressive form of anemia that may be fatal if not treated with vitamin B12. Usually caused by inability to absorb B12, not a dietary deficiency of B12. pescovegetarian A vegetarian who eats fish, but not poultry. pesticides Poisons used to destroy pests of various types, including plants and animals. pH The abbreviation used to express the level of acidity of a solution; a low pH represents high acidity.

phenylalanine An essential amino acid. phenylketonuria (PKU) Congenital lack of an enzyme to metabolize phenylalanine, an essential amino acid. May lead to mental retardation if not detected early in life. phosphagens Compounds such as ATP and phosphocreatine that serve as a source of high energy in the body cells. phosphates Salts of phosphoric acid, purported to possess ergogenic qualities. phosphatidylserine Phosphatidylserine, like phosphatidylcholine, is a naturally occurring phospholipid found in cell membranes; as a dietary supplement, it is theorized to possess ergogenic potential. phosphocreatine (PCr) A high-energy phosphate compound found in the body cells; part of the ATP-PCr energy system. phospholipids Lipids containing phosphorus that in hydrolysis yield fatty acids, glycerol, and a nitrogenous compound. Lecithin is an example. phosphorus A nonmetallic element essential to human nutrition. phosphorus:calcium ratio The ratio of calcium to phosphorus intake in the diet; the normal ratio is 1:1. photon absorptiometry An analytical, noninvasive technique designed to assess bone density. phylloquinone Vitamin K; essential in the blood clotting process. physical activity Any activity that involves human movement; in relation to health and physical fitness, physical activity is often classified as structured and unstructured. Physical Activity Level (PAL) Increase in energy expenditure through physical activity based on energy expended through daily walking mileage or equivalent activities; National Academy of Sciences lists four PAL categories: sedentary, low active, active, and very active. Physical Activity Pyramid A guide to weekly physical activity, including aerobic endurance, muscular strength and endurance, and flexibility. Physical Activity Quotient (PA) Coefficient used to calculate estimated energy requirement (EER) based on categories of physical activity levels (PAL). physical conditioning Methods used to increase the efficiency or capacity of a given body system so as to improve physical or athletic performance. physical fitness A set of abilities individuals possess to perform specific types of physical activity. Also see health-related fitness and sports-related fitness.

phytates Salts of phytic acids; produced in the body during the digestion of certain grain products; can combine with some minerals such as iron and possibly decrease their absorption. phytochemicals Chemical substances, other than nutrients, found in plants that are theorized to possess medicinal properties to help prevent various diseases. phytoestrogens Phytochemicals that may compete with natural endogenous estrogens; believed to help prevent certain forms of cancer associated with excess estrogen activity in the body. picolinate A natural derivative of tryptophan; commercially it is bound to chromium as a means of enhancing chromium absorption. plaque The material that forms in the inner layer of the artery and contributes to atherosclerosis. It contains cholesterol, lipids, and other debris. platelet aggregability Function of platelets to promote clumping together of red blood cells. polypeptides A combination of a number of simple amino acids; also see peptides. polysaccharide A carbohydrate that upon hydrolysis will yield more than ten monosaccharides. polyunsaturated fatty acids Fats that contain two or more double bonds and thus are open to hydrogenation. positive caloric balance A condition whereby caloric intake exceeds caloric output; the resultant effect is a weight gain. Positive Health Lifestyle A lifestyle characterized by health behaviors designed to promote health and longevity by helping to prevent many of the chronic diseases afflicting modern society. postabsorptive state The period after a meal has been absorbed from the gastrointestinal tract; in BMR tests it is usually a period of approximately 12 hours. potassium A metallic element essential in human nutrition; it is the principal cation present in the intracellular fluids. power Work divided by time; the ability to produce work in a given period of time. power-endurance continuum In relation to strength training, the concept that power or strength is developed by high resistance and few repetitions, whereas endurance is developed by low resistance and many repetitions. PRE Progressive resistive exercise. pre-event nutrition Dietary intake prior to athletic competition; may refer to a 2- to 3-day www.mhhe.com/williams9

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period prior to an event or the immediate preevent meal. premenstrual syndrome (PMS) A condition associated with a wide variety of symptoms during the time prior to menses. principle of exercise sequence Relative to a weight-training workout, the lifting sequence is designed so that different muscle groups are utilized sequentially so as to be fresh for each exercise. principle of overload The major concept of physical training whereby one imposes a stress greater than that normally imposed upon a particular body system. principle of progressive resistance exercise (PRE) A training technique, primarily with weights, whereby resistance is increased as the individual develops increased strength levels. principle of recuperation A principle of physical conditioning whereby adequate rest periods are taken for recuperation to occur so that exercise may be continued. principle of specificity of training The principle that physical training should be designed to mimic the specific athletic event in which one competes. Specific human energy systems and neuromuscular skills should be stressed. Pritikin program A dietary program developed by Nathan Pritikin, which severely restricts the intake of certain foods like fats and cholesterol and greatly increases the consumption of complex carbohydrates. profile of mood states (POMS) An inventory to evaluate mood states such as anger, vigor, etc. proline A nonessential amino acid. promoters Substances or agents necessary to support or promote the development of a disease once it is initiated. proof Relative to alcohol content, proof is twice the percentage of alcohol in a solution; 80-proof whiskey is 40 percent alcohol. prostaglandins Eicosanoids that possess hormone-like activity in numerous cells in the body. proteases Enzymes that catalyze proteins. protein Any one of a group of complex organic compounds containing nitrogen; formed from various combinations of amino acids. protein-Calorie insufficiency A major health problem in certain parts of the world where the population suffers from inadequate intake of protein and total Calories. protein complementarity The practice among vegetarians of eating foods together from two or more different food groups,

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usually legumes, nuts, or beans with grain products, in order to ensure a balanced intake of essential amino acids. Protein Digestibility Corrected Amino Acid Score (PDCAAS) A scientific measure used to assess the quality of protein in foods with values from 1.0 to 0.0, with 1.0 being the highest quality. protein hydrolysate A high-protein dietary supplement containing a solution of amino acids and peptides prepared from protein by hydrolysis. protein-sparing effect An adequate intake of energy Calories, as from carbohydrate, will decrease somewhat the rate of protein catabolism in the body and hence spare protein. This is the basis of the protein-sparing modified fast, or diet. proteinuria The presence of proteins in the urine. provitamin A Carotene, a substance in the diet from which the body may form vitamin A. Prudent Healthy Diet A diet plan based upon healthful eating principles that is designed to help prevent or treat common chronic diseases in the United States, Canada, and Mexico, particularly cardiovascular disease and cancer. psyllium A plant product that contains both water-soluble and insoluble dietary fiber. purines The end products of nucleoprotein metabolism, which may be formed in the body; they are nonprotein nitrogen compounds that are eventually degraded to uric acid. pyridoxal A component of the vitamin B group. pyridoxamine A part of the vitamin B group; an analog of pyridoxine. pyridoxine A component of the vitamin B complex, vitamin B6. pyruvate The end product of glycolysis. Under aerobic conditions it may be converted into acetyl CoA, whereas under anaerobic conditions it is converted into lactic acid. PYY Peptide YY (PYY), a gut hormone fragment produced by the intestines; affects neurons in the hypothalamus to reduce appetite and food intake. quackery Misrepresentation of the facts to deceive the consumer. quality Calories Calories in foods that are accompanied by substantial amounts of nutrients. Skim milk contains quality Calories as it provides considerable amounts of protein, calcium, and other nutrients, while cola drinks provide similar Calories but no nutrients.

quercetin A dietary flavonol, part of polyphenolic compounds that functions as an antioxidant and may also be an anti-inflammatory agent. radiation Electromagnetic waves given off by an object; the body radiates heat to a cool environment. radura International symbol of radiation; used on labels for irradiated foods. rating of perceived exertion (RPE) A subjective rating, on a numerical scale, used to express the perceived difficulty of a given work task. reactive hypoglycemia A decrease in blood glucose caused by an excessive insulin response to hyperglycemia associated with a substantial intake of high-glycemic-index foods. Recommended Dietary Allowances (RDA) The levels of intake of essential nutrients considered to be adequate to meet the known nutritional needs of practically all healthy persons. recommended dietary goals Dietary goals for U.S. citizens that have been established by a U.S. Senate subcommittee on nutrition; goals stress dietary reduction of fat, cholesterol, salt, and sugar, and increase of complex carbohydrates. recuperation principle See principle of recuperation. Reference Daily Intakes (RDIs) The RDI is used in food labeling as the recommended daily intake for protein and selected vitamins and minerals. It replaces the old U.S. RDA (United States Recommended Daily Allowance). regional fat distribution Deposition of fat in different regions of the body. See also android- and gynoid-type obesity. relative humidity The percentage of moisture in the air compared to the amount of moisture needed to cause saturation, which is taken as 100. relative risk (RR) A probability estimate; RR of 1.0 is normal. relative-weight method A method of determining obesity by comparing the weight of an individual to standardized height and weight tables. repetition maximum (RM) In weight training, the amount of weight that can be lifted for a specific number of repetitions. repetitions In relation to weight training or interval training, the number of times that an exercise is done. resistin An adipokine secreted by adipose tissue that is thought to increase insulin resistance and may be the link between obesity and development of type 2 diabetes.

resting energy expenditure (REE) The energy required to drive all physiological processes while in a state of rest. resting metabolic rate (RMR) Also see BMR and REE. retinol Vitamin A. retinol equivalent (RE) A measure of vitamin A activity in food as measured by preformed vitamin A or carotene, provitamin A; 1 RE equals 5 IU. rHGH See human growth hormone. riboflavin Vitamin B2, a member of the B complex. ribose A five-carbon sugar found in several body compounds, such as riboflavin. risk factor Associated factors that increase the risk for a given disease; for example, cigarette smoking and lung cancer. RNA Ribonucleic acid; nuclear material involved in the formation of proteins in cells. running Although the distinction between running and jogging is relative to the individual involved, a common value used for running is 7 mph or faster. saccharide A series of carbohydrates ranging from simple sugars (monosaccharides) to complex carbohydrates (polysaccharides). saccharine An artificial sweetener made from coal tar. Salmonella A bacteria commonly involved in food poisoning. sarcopenia Loss of muscle mass associated with the aging process. satiety center A group of nerve cells in the hypothalamus that responds to certain stimuli in the blood and provides a sensation of satiety. saturated fatty acids Fats that have all chemical bonds filled. SCAN Sports and Cardiovascular Nutritionists, a practice group of the American Dietetic Association focusing on applications of nutrition to sport and wellness. scurvy A deficiency caused by a lack of vitamin C in the diet; symptoms include weakness, bleeding gums, and anemia. SDA Specific dynamic action; often used to represent the increased energy cost observed during the metabolism of protein in the body. Also see dietary-induced thermogenesis and TEF. Seasonal affective disorder (SAD) Symptoms associated with various seasons of the year, e.g., depression in winter months.

secondary amenorrhea Cessation of menstruation after the onset of puberty; primary amenorrhea is the lack of menstruation prior to menarche. Sedentary Death Syndrome (SeDS) Term associated with a sedentary lifestyle and related health problems that predispose to premature death. selenium A nonmetallic element resembling sulfur; an essential nutrient. semivegetarian An individual who refrains from eating red meat but includes white meat such as fish and chicken in a diet stressing vegetarian concepts. serotonin A neurotransmitter in the brain; may induce a sense of relaxation and drowsiness, possibly associated with fatigue; may also depress the appetite. serum lipid level The concentration of lipids in the blood serum. set-point theory The weight-control theory that postulates that each individual has an established normal body weight. Any deviation from this set point will lead to changes in body metabolism to return the individual to the normal weight. sets In weight training, a certain number of repetitions constitutes a set; for example, a lifter may do three sets of six repetitions per set. settling-point theory Theory that the body weight set point may be increased or decreased through interactions of genetics and the environment; an environment rich in highfat foods may lead to a higher set point so that the body settles in at a higher weight and fat content. shell temperature The temperature of the skin; also see core temperature. short-chain fatty acids (SCFA) Fatty acids with chains containing less than six carbons. sibutramine A prescription drug for weight loss that suppresses the appetite by affecting brain neurotransmitters. silicon A nonmetallic element. simple carbohydrates Usually used to refer to table sugar, or sucrose, a disaccharide; may refer also to other disaccharides and the monosaccharides. Simplesse A commercially produced fat substitute derived from protein. skinfold technique A technique used to compute an individual’s percentage of body fat; various skinfolds are measured and a regression formula is used to compute the body fat. sling psychrometer A device that incorporates both a dry-bulb and wet-bulb thermometer, thus providing a heat-stress

index incorporating both temperature and relative humidity. slow-twitch fibers Red muscle fibers that have a slow contraction speed; designed for aerobic-type activity. Smilax A commercial plant extract theorized to produce anabolic effects. soda loading Term associated with use of baking soda (sodium bicarbonate) as an ergogenic aid. sodium A soft metallic element; combines with chloride to form salt; the major extracellular cation in the human body. sodium bicarbonate NaHCO3; a sodium salt of carbonic acid that serves as a buffer of acids in the blood, often referred to as the alkaline reserve. sodium citrate A white powder used as a blood buffer; see also sodium bicarbonate. sodium loading Consumption of excess amounts of sodium; endurance athletes may use sodium loading in attempts to increase plasma volume, improve blood flow, and enhance aerobic endurance. soluble dietary fiber Dietary fibers in plants such as gums and pectins that are soluble in water. specific dynamic action See SDA. specific heat The amount of energy or heat needed to raise the temperature of a unit of mass, such as 1 kilogram of body tissue, 1 degree Celsius. specificity of training See principle of specificity of training. sport nutrition The application of nutritional principles to sport with the intent of maximizing performance. sports anemia A temporary condition of low hemoglobin levels often observed in athletes during the early stages of training. sports bars Commercial food products targeted to athletes and physically active individuals containing various concentrations of carbohydrate, fat, and protein; some products contain other nutrients, such as antioxidants. sports drinks Popular term for various glucose-electrolyte fluid replacement drinks. sports gels Commercial food products targeted to athletes; consist primarily of carbohydrate in a gel form. sports-related fitness Components of physical fitness that, when improved, have implications for enhanced sport performance, such as agility and power. sports supplements Dietary supplements marketed to athletes and physically active individuals.

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spot reducing The theory that exercising a specific body part, such as the thighs, will facilitate the loss of body fat from that spot. standard error of measurement or estimate A measure of variability about the mean. Sixty-eight percent of the population is within one standard error above and below the mean, while about 95 percent is within two standard errors. standardized exercise An exercise task that conforms to a specific standardized protocol. Staphylococcus A bacteria commonly involved in food poisoning. steady state A level of metabolism, usually during exercise, when the oxygen consumption satisfies the energy expenditure and the individual is performing in an aerobic state. steady-state threshold The intensity level of exercise above which the production of energy appears to shift rapidly to anaerobic mechanisms, such as when a rapid rise in blood lactic acid exists. The oxygen system will still supply a major portion of the energy, but the lactic acid system begins to contribute an increasing share. sterols Substances similar to fats because of their solubility characteristics; the most commonly known sterol is cholesterol. stimulus period In exercise programs, the time period over which the stimulus is applied, such as a HR of 150 for 15 minutes. storage fat Fat that accumulates and is stored in the adipose tissue; also see essential fat. strength-endurance continuum In relation to strength training, the concept that power or strength is developed by high resistance and few repetitions and that endurance is developed by low resistance and many repetitions. structured physical activity A planned program of physical activities usually designed to enhance physical fitness; structured physical activity is often referred to as exercise. subclinical malnutrition A nutrientdeficiency state in which no clinical signs of the nutrient deficiency are observable, but other nonspecific symptoms such as fatigue may be present. subcutaneous fat The body fat found immediately under the skin; evaluated by skinfold calipers. sucrose Table sugar, a disaccharide; yields glucose and fructose upon hydrolysis. sulfur A pale yellow nonmetallic element essential in human nutrition; component of the sulfur-containing amino acids.

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sumo wrestling A form of wrestling in Japan. superoxide dismutase An enzyme in body cells that helps neutralize free radicals. Syndrome X See metabolic syndrome. synephrine A dietary supplement marketed for fat loss; synephrine is derived from a fruit plant known as bitter orange. Used as an alterative to Ephedra, or ephedrine. systolic blood pressure The blood pressure in the arteries when the heart is contracting and pumping blood. target heart rate range In an aerobic exercise program, the heart-rate level that will provide the stimulus for a beneficial training effect. taurine A vitamin-like compound synthesized from amino acids, mainly methionine and cysteine. testosterone The male sex hormone responsible for male secondary sex characteristics at puberty; it has anabolic and androgenic effects. thermic effect of exercise (TEE) Increased muscular contraction produces additional heat. thermic effect of food (TEF) The increased body heat production associated with the digestion, assimilation, and metabolism of energy nutrients in a meal just consumed. thermogenesis The production of heat; metabolic processes in the body generate heat constantly. thiamin Vitamin B1. threonine An essential amino acid. threshold stimulus The minimal level of exercise intensity needed to stimulate gains in physical fitness. thromboxanes Eicosanoids that possess hormone-like activity in numerous cells in the body. thyroxine A hormone secreted by the thyroid gland that is involved in the control of the metabolic rate. tin A white metallic element. tocopherol Generic name for an alcohol that has the activity of vitamin E. Tolerable Upper Intake Levels (UL) The highest level of daily nutrient intake likely to pose no adverse health risks. tonicity Tension or pressure as related to fluids; fluids with high osmolality exhibit hypertonicity while fluids with low osmolality exhibit hypotonicity. total body electrical impedance A sophisticated method of measuring the resistance provided by water in the body as a means to predict body composition. total body fat The sum total of the body’s storage fat and essential fat stores.

total daily energy expenditure (TDEE) The total amount of energy expended during the day, including REE, TEF, and TEE. total fiber Sum of dietary fiber and functional fiber. trabecular bone The spongy bone structure found inside the bone, as contrasted with the more compact bone on the outside. trace minerals Those minerals essential to human nutrition that have an RDA less than 100 mg. trans fatty acids Unsaturated fatty acids in which the hydrogen ions are on opposite sides of the double bond. triglycerides One of the many fats formed by the union of glycerol and fatty acids. triose A simple sugar having three carbon atoms. tryptophan An essential amino acid. Type I muscle fiber The slow-twitch red fiber that provides energy primarily by the oxygen system. Type IIa muscle fiber The fast-twitch red fiber that provides energy by both the oxygen system and the lactic acid system. Type IIb muscle fiber The fast-twitch white fiber that provides energy primarily by the lactic acid system. tyrosine A nonessential amino acid. ubiquinone See CoQ10. uncompensated heat stress A condition when heat loss is insufficient to offset heat production during exercise in the heat, the body temperature continues to rise and exhaustion eventually occurs. uncoupling protein (UPC) A protein believed to stimulate thermogenesis in fat tissues; uncouples thermogenesis with the production of ATP, so no ATP is generated in this process. underwater weighing A technique for measuring the percentage of body fat in humans. United States Recommended Daily Allowances See U.S. RDA. Universal Gym A brand name for exercise equipment, particularly weights for strength development. unsaturated fatty acids Fatty acids that contain double or triple bonds and hence can add hydrogen atoms. unstructured physical activity Many of the normal, daily physical activities that are generally not planned as exercise, such as walking to work, climbing stairs, gardening, domestic activities, and games and other childhood pursuits.

urea The chief nitrogenous constituent of urine and the final product of the decomposition of proteins in the body. uric acid A crystalline end product of purine metabolism; commonly involved in gout and the formation of kidney stones. USDA United States Department of Agriculture. USOC

United States Olympic Committee.

U.S. RDA The United States Recommended Daily Allowances; the RDA figures used on labels, representing the percentage of the RDA for a given nutrient contained in a serving of the food. The U.S. RDA are now known as the Reference Daily Intake (RDI). valine

An essential amino acid.

Valsalva phenomenon A condition in which a forceful exhalation is attempted against a closed epiglottis and no air escapes; such a straining may cause the person to faint. vanadium

A light gray metallic element.

vanadyl sulfate A salt form of vanadium; marketed for its anabolic potential. vascular water The body water contained in the blood vessels; a part of the extracellular water. vasodilation An increase in the size of the blood vessels, usually referring to the arterial system. vasopressin (ADH).

See antidiuretic hormone

vegan Vegetarian who eats no animal products. vegetable exchange One vegetable exchange in the Food Exchange System contains 5 grams of carbohydrate, 2 grams of protein, and 25 Calories. vegetarian One whose food is of vegetable or plant origin; also see lactovegetarian, ovovegetarian, ovolactovegetarian, pescovegetarian, semivegetarian, and vegan. very-low-Calorie diet (VLCD) A diet containing less than 800 Calories per day. very low-density lipoprotein

See VLDL.

visceral fat The deep fat found in the abdominal area; needs special measuring techniques, such as MRI. vitamin, natural Often referred to as a vitamin derived from natural sources; i.e.,

food in nature; contrast with vitamin, synthetic. vitamin, synthetic An artificial vitamin commercially produced from the separate components of the vitamin. vitamin A Retinol, an unsaturated aliphatic alcohol; fat soluble. vitamin B1 vitamin.

Thiamin; the antineuritic

vitamin B2

Riboflavin.

vitamin B6 Pyridoxine and related compounds. vitamin B12

Cyanocobalamin.

vitamin B15 Not a vitamin but marketed as one; usual composition is calcium gluconate and dimethylglycine (DMG). vitamin C Ascorbic acid; the antiscorbutic vitamin. vitamin D Any one of related sterols that have antirachitic properties; fat soluble. vitamin D3 The prohormone form of vitamin D, also known as cholecalciferol, formed in the skin by irradiation from the sun. Released into the blood and eventually converted by the kidney to the hormone form of vitamin D. vitamin deficiency Subnormal bodyvitamin levels due to inadequate intake or absorption; specific disorders are linked with deficiencies of specific vitamins. vitamin E Various forms of tocotrienols and tocopherols; fat soluble. vitamin K The antihemorrhagic, or clotting vitamin; fat soluble. vitamins A general term for a number of substances deemed essential for the normal metabolic functioning of the body. VLDL Very low-density lipoproteins; a protein-lipid complex in the blood that transports triglycerides, cholesterol, and phospholipids; has a very low density. Also see HDL-cholesterol and LDL-cholesterol. voluntary dehydration Intentional loss of body fluids in attempts to reduce body mass for sports competition; techniques include exercise, sauna, and diuretics. VO2 max Maximal oxygen uptake; measured during exercise, the maximal amount of oxygen consumed reflects the body’s ability to utilize oxygen as an energy

source; equals the cardiac output times the arteriovenous oxygen difference. WADA World Anti-Doping Agency. waist circumference The circumference of the waist at its most narrow point as seen from the front; used as a measure of regional adeposity. warm-down A phase after an exercise session during which the individual gradually tapers the level of activity—for example, by jogging slowly after a fast run. warm-up Low-level exercises used to increase the muscle temperature and/or stretch the muscles prior to a strenuous exercise bout. water A tasteless, colorless, odorless fluid essential to life; composed of two parts hydrogen and one part oxygen (H2O). water intoxication Consumption of excessive amounts of water leading to dilution of body electrolytes. See also hyponatremia. watt A unit of power in the SI; one watt equals about 6 kilogram-meters per minute. WBGT Index Wet-bulb globe thermometer index; a heat-stress index based upon four factors measured by the wet-bulb globe thermometer. weight cycling Repetitive loss and regain of body weight; often called yo-yo dieting. wet-bulb globe thermometer A device that takes into account the various factors determining heat stress: air temperature, air movement, radiation heat, and humidity. wheat germ oil Oil extracted from the embryo of wheat, high in linoleic fatty acid, vitamin E, and octacosanol. work Effort expended to accomplish something; in terms of physics, force times distance. xerophthalmia Dryness of the conjunctiva and cornea of the eye, which may lead to blindness if untreated; caused by a deficiency of vitamin A. xylitol A sugar alcohol that may be obtained from fruits. yohimbine A plant extract theorized to stimulate testosterone production and elicit anabolic effects. zinc A blue-white crystalline metallic element essential to human nutrition. zone diet A high-protein diet plan; the 40-30-30 plan consisting of 40 percent Calories from carbohydrate, and 30 percent each from protein and fat.

www.mhhe.com/williams9

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Photo Credits Chapter 1 Page 2, p. 3: © Fruits & Vegetables, OS1/PhotoDisc/Getty RF; 1.4: R-F Website/Getty RF; p. 9: © Supporting Cast: Teens, OS39/PhotoDisc/Getty RF; 1.8: © Corbis RF; p. 17: © Fruits & Vegetables, OS1/PhotoDisc/Getty RF; p. 18 (left): © Sporting Goods, OS25/PhotoDisc/Getty RF; p. 18(right): © Fruits & Vegetables, OS1/PhotoDisc/Getty RF; 1.11: © Mauro Femariello/Photo Researchers, Inc. Chapter 2 Page 38: © Fruits & Vegetables, OS1/PhotoDisc/Getty RF; p. 41: © Supporting Cast: Teens, OS39/PhotoDisc/Getty RF; 2.2(all): © Greg Kidd and Joanne Scott; p. 42(top), p. 42 (bottom): © Fruits & Vegetables, OS1/PhotoDisc/Getty RF; 2.5: © DV023/Digital Vision/Getty RF; p. 47(top): © Supporting Cast: Teens, OS39/PhotoDisc/Getty RF; p. 47(bottom): © Fruits & Vegetables, OS1/PhotoDisc/Getty RF; 2.7a: © The McGraw-Hill Companies, Inc./Sabina Dowell, photographer; 2.7b: © Greg Kidd and Joanne Scott; 2.8: © Brian Leatart/FoodPix/Jupiterimages; 2.9: © The McGraw-Hill Companies, Inc./Sabina Dowell, photographer; p. 59, 60: © Supporting Cast: Teens, OS39/PhotoDisc/Getty RF; 2.11: © The McGraw-Hill Companies, Inc./Sabina Dowell, photographer; 2.12: © Vol. 67 PhotoDisc/Getty RF; p. 75(top): © Supporting Cast: Teens, OS39/PhotoDisc/Getty RF; p. 75(bottom): © Market Fresh, OS49/PhotoDisc/Getty RF; p. 79(all): © Fruits & Vegetables, OS1/PhotoDisc/Getty RF. Chapter 3 Figure 3.3: © Samual Ashfield/SPL/Photo Researchers, Inc.; 3.4: © Delicious Delights/Corbis RF; 3.6: © People in Sports/Corbis RF; p. 96, p. 97(top), p. 97(bottom): © Supporting Cast: Teens, OS39/PhotoDisc/Getty RF; 3.14: © Yoav Levy/Phototake; p. 102(bottom): © Supporting Cast: Teens, OS39/PhotoDisc/Getty RF; 3.16: © Vol. 10 PhotoDisc/Getty RF; p. 98(right): © Sporting Goods, OS25/PhotoDisc/Getty RF; p. 105: © Supporting Cast: Teens, OS39/PhotoDisc/Getty RF. Chapter 4 Page 126: © Fruits & Vegetables, OS1/PhotoDisc/Getty RF; p. 130: © Market Fresh, OS49/PhotoDisc/Getty RF; p. 134: © Recreational Sports, Vol. 82/PhotoDisc/Getty RF; p. 144: © Sporting Goods, OS25/PhotoDisc/Getty RF; p. 147: © Market Fresh, OS49/PhotoDisc/Getty RF; p. 148: © Sporting Goods, OS25/PhotoDisc/Getty RF; p. 151: © Familiar Objects, OS57/PhotoDisc/Getty RF; p. 154: © Contemporary Cuisine, Vol. 30/PhotoDisc/Getty RF; p. 157: © Food and Dining, Vol. 12/PhotoDisc/Getty RF. Chapter 5 Figure 5.4: © The McGraw-Hill Companies, Inc./John Thoeming, photographer; p. 181, 187, 189: © Sporting Goods, OS25/PhotoDisc/Getty RF; p. 190: © Supporting Cast: Teens, OS39/PhotoDisc/Getty RF; 5.17: © Vol. 12 PhotoDisc/Getty RF.

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Chapter 6 Figure 6.3: © The McGraw-Hill Companies, Inc./John Thoeming, photographer; p. 224: © Contemporary Health, Vol. 83/PhotoDisc/Getty RF. Chapter 7 Page 268: © Health and Well Being, Vol. 67/PhotoDisc/Getty RF; p. 276: © Fruits & Vegetables, OS1/PhotoDisc/Getty RF; p. 279: © Fruits & Vegetables, OS1/PhotoDisc/Getty RF; p. 281: © Market Fresh, OS49/PhotoDisc/Getty RF; p. 283: © Child’s Play, OS47/PhotoDisc/Getty RF; p. 288: © Sporting Goods, OS25/PhotoDisc/Getty RF; p. 298: © Sporting Goods, OS25/PhotoDisc/Getty RF. Chapter 8 Figure 8.1: © Vol. 111 PhotoDisc/Getty RF; p. 318: © Sports & Fitness, Vol. 103/Corbis RF; p. 323: © American Food Basics, Vol. 4/Corbis RF; p. 334: © Food Essentials, Vol. 20/PhotoDisc/Getty RF; p. 341: © Sports & Fitness, Vol. 103/Corbis RF. Chapter 9 Page 353: © Food Essentials, Vol. 20/PhotoDisc/Getty RF; © People in Sports/Corbis RF; p. 361, p. 370: © Fruits & Vegetables, OS1/PhotoDisc/Getty RF; p. 384: © Health and Well Being, Vol. 67/PhotoDisc/Getty RF; 9.12: © Tony Duffy/Getty. Chapter 10 Figure 10.2: Rick O'Quinn/University of Georgia; 10.3: Photo courtesy of Life Measurement Instruments; p. 410: © Sports & Fitness, Vol. 103/Corbis RF; Courtesy DEXA; p. 423: © Sporting Goods, OS25/PhotoDisc/Getty RF; p. 424: © Sports & Fitness, Vol. 103/Corbis RF; p. 428: © Sports & Fitness, Vol. 103/Corbis RF. Chapter 11 Page 453: © Sports & Fitness, Vol. 103/Corbis RF; 11.5: (golf ball): © Vol. 127/Corbis RF; (tennis ball): © Sporting Goods, OS25/PhotoDisc/Getty RF; (yo-yo): R-F website/Corbis RF; (mouse): © Vol. 127/Corbis RF; (baseball): © Sporting Goods, OS25/PhotoDisc/Getty RF; (fist): © OS02/PhotoDisc/Getty RF; 11.6: © Digital Vision/Getty RF; p. 472: © Sports & Fitness, Vol. 103/Corbis RF; 11.11: © Stockbyte/Punchstock; p. 481: © Sports & Fitness, Vol. 103/Corbis RF. Chapter 12 Figure 12.2: © Food Collections/Getty Images; p. 505: © Sports & Fitness, Vol. 103/Corbis RF; 12.4: © Vol. 51/PhotoDisc/Getty RF. Chapter 13 Page 529: © Contemporary Cuisine, Vol. 30/PhotoDisc/Getty RF; 13.4: © Vol. 66/PhotoDisc/Getty RF; 13.5: © The McGraw-Hill Companies, Inc./Lars A. Niki, photographer; p. 539: © Contemporary Cuisine, Vol. 30/PhotoDisc/Getty RF; 13.6: © Vol. 59/PhotoDisc/Getty RF; 13.7: © The McGraw-Hill Companies, Inc./Jill Braaten, photographer; 13.8: © The McGraw-Hill Companies, Inc./Jill Braaten, photographer; 13.10: © Sports & Fitness CD/Corbis RF; 13.12: © The McGraw-Hill Companies, Inc./Jill Braaten, photographer.

Index A Absorption of nutrients, 122–123 of carbohydrates, 123 of dietary fat, 175–176 of proteins, 217–218 Accelerometer, 87–88 Acceptable Macronutrient Distribution Range (AMDR), 39 Acclimatization, 389–390 Acesulfame-K, 154, 155 Active category, 107, 446 Active transport, 122–123 Activity-stat, 414 Added sugar, 120 Additives. See Food additives Adenosine triphosphate (ATP) ATP-PCr system, 92–93 defined, 91 lactic acid system, 93 oxygen system, 93–94 stored in body, 91, 92 supplements, 323 Adequate Intake (AI), 39 Adipokines, 178, 420, 422 Adonis Complex, 499 Advertising, nutritional quackery and, 22–23 Aerobic capacity, 94, 95 Aerobic dance, energy expenditure for, 104 Aerobic endurance exercise caffeine and, 536–537 high-protein diets and improved performance, 230–232 protein metabolism and training, 222 sodium bicarbonate, 546–547 Aerobic exercise amount needed for health benefits, 7–8 benefits of, other than weight loss, 472 caffeine and, 535–536 Circuit aerobics, 519 low muscle glycogen, 134 protein as energy source during, 220 recommendation guidelines, 8–9 resting energy expenditure (REE), 471 warm-down, 476 warm-up, 476 for weight loss, 470–472 Aerobic glycolysis, 93, 94, 95 Aerobic lipolysis, 94, 95 Aerobic power, 94, 95 Aerobic system, 93 Aerobic walking, 482 Age fat as energy source during exercise and, 182 physical performance and nutritional recommendations, 80 tolerating exercise in heat, 388 Air displacement plethysmography, 408 Alanine, 213 Alcohol, 526–533 blood alcohol concentration, 527 brief historical perspective on, 526 Calories in one gram, 90 defined, 526 ergogenic effects energy source, 527–528 exercise metabolism, 528 psychological processes, 528–529

health effects alcohol dependence, 532 binge drinking, 530 cancer, 531 cardiovascular disease, 530–531 fetal alcohol spectrum disorders, 531 liver disease, 529 obesity, 531–532 positive effects, 532–533 psychological problems, 529–530 healthful dietary guidelines for, 51 limiting, for weight loss, 465 metabolism of, 526–527 nutrient content of typical alcoholic beverage, 526, 527 obesity and, 417 permissibility of in competition, 528–529 proof, 526 Alcoholism, 532 Aldosterone, 359, 360 Alimentary canal, 122 Allium sulfides, 57 Alpha-ketoacid, 217 Alpha-linoleic acid cholesterol-lowering recommendations, 198–201 dietary recommendations for, 174 Alpha-tocopherol, 271–273 Alzheimer’s disease, antioxidant supplements to prevent, 296 Amenorrhea athletic, 320 exercise induced, 202, 205 female athlete triad, 319–320, 430–431 secondary, 320 Amino acids, 212. See also specific amino acids consumption of individual, 252–253 ergogenic aspects of, 232–249 essential, 213, 216 glucogenic, 217 nonessential, 213 Aminostatic theory, 412 Ammonia, 217 Amylase, 123 Anabolic/androgenic steroids (AAS), 21 effectiveness, legality, safety of, 548–550 Anabolic hormones, 547–551 Anabolism, 96 Anaerobic capacity, 93, 95 Anaerobic exercise caffeine and, 535–536 low muscle glycogen, 134–135 sodium bicarbonate and, 545 Anaerobic glycolysis, 93, 133 Anaerobic power, 93, 95 Anderson, Richard, 335 Android-type obesity, 421–423 Androstenedione effectiveness, legality, safety of, 551 as ergogenic aid, 21 increase in use of, 22 Anemia iron-deficiency, 328, 330–331 sports anemia, 224, 329 Angina, 192

Animal proteins, 213–214 Anorexia athletica, 430 Anorexia nervosa, 428–429 Anthocyanins, 57 Anthropometry, 409 Antidiuretic hormone (ADH), 355 Antioxidants foods rich in, and preventing chronic diseases, 293–294 function of vitamins, 263 role in metabolism, 57 supplements to prevent fatigue and muscle damage, 286–288 vitamin E as, 272 vitamins supplements to prevent disease, 294–297 cancer, 295–296 cardiovascular disease and stroke, 294–295 eye health, 296 general health, 296–297 mental health, 296 Antipromoters, 12 Apolipoproteins, 175 Appestat, 412 Appetite exercise affect on, 472 ghrelin and, 413–414 hypothalamus and control of, 412 leptin and, 414 stimuli that influence, 412 Arginine, 232–234 Armstrong, Larry, 286 Arteriosclerosis, 192 Artificial sweeteners safety of, 154–155 types of, 154, 155 weight loss and, 464 Ascorbic acid, 266–267 Aspartame, 119, 154, 155 Aspartates, 238 Atherosclerosis defined, 192 different forms of cholesterol and development of, 192–194 exercise to reduce risk of, 202, 205 process of, 192, 193 reducing serum lipid levels to reverse, 194–195 Athletic amenorrhea, 320 Athletic performance. See Sports performance Atkins diet, 455, 456 ATP. See Adenosine triphosphate (ATP) ATP-PCr system creatine and, 241–242 energy source during exercise, 108–110 fatigue and, 110, 111 sodium bicarbonate, 546

B Bacteria food poisoning and, 72 organic food, 70 Bahrke, Michael, 552–553 Balance in healthful diet, 36 in MyPyramid, 41

Balanced diet, 40–47 concept of, 40 food categories for, 41 Food Exchange System, 43 key-nutrient concept, 43–45 MyPyramid, 41–43 nutrient density, 45 selecting foods for, 40–41 Balance exercises, 9 Bartels, Robert, 501 Basal energy expenditure (BEE), 96, 413 Basal metabolic rate (BMR), 96 Bean, Adam, 480 Bee pollen, 289 Behavior modification for weight loss, 448–452 applying to weight-control program, 449–452 defined, 449 importance of, 449 physical and social environmental factors, 449–450 short-term and long-term goals, 449, 450 suggested behavior changes, 450–451 Bernardot, Dan, 290 Beta-alanine, 247–248 Beta-carotene, 57 overview of, 265–268 vegetarian diet and, 57 Beta-oxidation, 179 Beverages, healthful dietary guidelines for, 51 Binge eating disorder, 429 Bioavailability, 264 Bioelectrical impedance analysis, 409 Biotechnology, food safety and, 68–69 Biotin, 281–282 deficiency, 281–282 DRI, 281 food sources, 281 major functions, 281 overview, 266–267 prudent recommendations, 282 supplementation, 282 Block, Gladys, 293 Blood alcohol concentration, 527 Blood doping, 19 Blood glucose body making, 128 fatigue and, 112 glycemic index and, 124–125 hormones that regulate, 132–133 hyperglycemia, 125 hypoglycemia, 125, 131–133 maintenance of levels and carbohydrate ingestion, 139 uses of, 125, 127 Blood pressure. See also High blood pressure caffeine and, 539 as heart disease risk factor, 15 measuring, 391 BMI. See Body Mass Index (BMI) Bod Pod, 408 Bodybuilders, carbohydrate loading, 148 Body composition, 403–434 BMI and, 404

619

as component of health-related fitness, 4 components of, 404–406 body water, 406 bone mineral, 406 fat-free mass, 405–406 total body fat, 405 excessive weight and sports performance, 432–433 excessive weight loss and health, 425–433 ideal body weight, 404 measuring, 406–409 air displacement plethysmography, 408 anthropometry, 409 bioelectrical impedance analysis, 409 dual energy X-ray absorptiometry, 409 infrared interactance, 409 multicomponent models, 409 overview of, 406–407 skinfold technique, 408–409 underwater weighing, 407–408 optimal body fat percentage, 410–411 Body Mass Index for, 410 waist circumference, 411 problems with body-fat percentages for sports, 409–410 regulation of, 411–419 body’s normal mechanisms of, 411–414 causes of obesity, 415–418 fat deposited in body, 414 set-point theory, 414 settling-point theory, 418 resting energy expenditure and, 97–98 Body fat percentage determining optimal body fat, 410–411 using to calculate how much weight to lose, 448 Body image, 403 Body mass creatine and, 243 lean body mass, 406 Body Mass Index (BMI) defined, 404 determining optimal body fat, 410 formula for, 404 health risks and levels of, 410, 411 limitations of, 404 using to calculate how much weight to lose, 447–448 Body temperature. See Temperature, body Body water stored in body, 353–355 extracellular, 354 intercellular, 354 intracellular, 354 intravascular, 354 weight loss exercise and, 485, 486–487 in first week and, 453–454 Body weight. See Weight Bonci, Christine, 430 Bonci, Leslie, 373, 430 Bones. See also Osteoporosis calcium intake and, 317 calcium supplements and, 317–318 as component of body composition, 406 exercise and, 318–319 female athlete triad, 319–320 high-protein diets and, 252 vitamin D and, 270–271 Booth, Frank, 5 Borg, Gunnar, 480 Boron, 338–339 deficiency, 338 DRI, 338 food sources, 338

620

Index

major functions, 338 prudent recommendations, 339 supplementation, 338–339 Bottled water, 353 Bouchard, Claude, 3, 8 Branched-chain amino acids (BCAA), 234–237 body composition and, 236–237 carbohydrates and, 236 central fatigue hypothesis, 234–235 mental performance and, 235 perceived exertion and, 235 physical performance and, 235–236 Bray, George, 412, 449 Bread, cereal, rice, and pasta food category, 41 Breakfast eating, for weight loss, 465–466 skipping, 76 during training and, 75–76 Breast cancer alcohol use and, 531 obesity and, 421 Brooks, George, 134 Brouns, Fred, 152 Brownell, Kelly, 416, 450–451 Brown fat, weight regulation and, 413 Bulimia nervosa, 429 Burke, Louise, 144, 147, 374, 377 Butterfield, Gail, 224, 501

C Cade, Robert, 322 Caffeine creatine and, 243 defined, 533 with ephedrine, 543 exercise performance enhancement, 533–539 aerobic endurance performance, 536–537 benefit for exercise performance, 534 carbohydrate loading and, 537 delivery system and, 538 as ergogenic aid, 19 exercise in heat and, 538 fat oxidation and, 536 high-intensity anaerobic/aerobic exercise and, 535–536 individual response to, 539 mental alertness and, 535 muscle contractions, 535 muscle glycogen sparing, 536 permissibility of, 538–539 placebo effect, 538 rating of perceived exertion, 537 resting energy expenditure, 97 food sources of, 533–534 health benefits/risks of, 539–542 caffeine dependence, 542 caffeine naivete, 541–542 cancer, 540 cardiovascular disease, 539–540 death, 542 gastric distress, 541 neuroprotective effects, 540–541 osteoporosis, 541 pregnancy-related health problems, 541 sleeplessness, 541 type 2 diabetes, 540 weight control, 541 Calcium, 312–321 bone health, 317 calcium balance in body, 313–314 cancer and, 315–316 deficiency, 313–315 DRI, 312 exercise and, 318–319 female athlete triad, 319–320

food sources, 45, 55, 312–313 healthful dietary guidelines for, 52 high blood pressure, 316–317 hormone replacement therapy, 319 as key-nutrient, 45 lactose intolerance and, 158 major functions, 313 osteoporosis in sports, 319–320 overview of, 311, 313 prudent recommendations, 320–321 supplements, 317–318 vegetarian diet and, 55 weight loss, 317 Calories in alcohol, 526, 527 best activities to increase energy expenditures, 103–105 calculating percentage of fat Calories, 170–171 caloric concept of weight control, 443–444 in carbohydrates, fat, protein and alcohol, 89–90 converting to kilojoules, 89 defined, 89 determining energy cost of exercise, 103 equivalent energy values, 89 Estimated Energy Requirement (EER), 106–108 obesity causes high-fat, high-Calorie foods, 415–416 liquid Calories, 416 low-fat, large-portion size, highCalorie foods, 416 in pound of fat, 443 reading food labels and, 62, 63 for vegetarian diet, 55 vegetarian diet as low Calorie diet, 57 weight gain to form pound of muscle, 501 for one pound/week, 501 weight loss aerobic exercise and, 470–471 counting Calories for, 456–458 decrease in need for after weight loss, 454 determining Calories for, 452–453 determining calories in foods, 458–461 Food Exchange System, 458, 459 number of days for weight loss for calorie deficit, 453 planning nutritionally balance, low-Calorie diet, 467–468 simple food substitutions to save, 464 very-low-Calorie diets, 468–469 weight maintenance, 444–447 Calorie counting technique, 447 Estimated Energy Requirement (EER) MyPyramid technique, 446–447 Estimated Energy Requirement (EER) technique, 444–446 factors involved in, 444 simplified technique, 447 Calorimetry, 88–89 Cancer alcohol use and, 531 antioxidant supplements to prevent, 295–296 artificial sweeteners and, 154–155 caffeine and, 540 calcium and, 315–316 food additives and, 73 guidelines for preventing, 14 high-protein diets and, 250–251 nutrition and, 12, 13 obesity and, 420–421 refined sugar, 154 vitamin D, 270, 271

Capsaicin, 57 Carbohydrate-electrolyte solution, 370 exercising during heat and replacing carbohydrates, 373–375 Carbohydrate loading, 145–150 caffeine and, 537 defined, 145 detrimental effects of, 150 methods for, 146–148 muscle glycogen concentrations, 148 sports performance and, 148–150 types of athletes to benefit from, 145–146 water retention, 148, 150 Carbohydrates, 118–159. See also Carbohydrate loading artificial sweeteners, 154–155 ATP formation from, 91 blood glucose, 124–125 branched-chain amino acids and, 236 Calories in one gram, 89–90, 118 complex, 119, 155–156 converting to fat, 178, 444 daily need for, 121–122 defined, 118 digestion and absorption of, 123–124 energy source during rest, 98, 128 energy source for exercise, 109–110 activities that rely on carbohydrates, 130 carbohydrate intake right before/during, 135–143 carbohydrate replenishment after exercise, 143–144 for endurance events, 130 endurance training effect on carbohydrate metabolism, 131 high-carbohydrate diet for daily exercise training, 144–145 hypoglycemia related to fatigue, 131–133 lactic acid production related to fatigue, 133–134 low endogenous carbohydrate levels and central fatigue hypothesis, 135 low muscle glycogen related to fatigue, 134–135 reason best source for exercise, 130–131 ergogenic aspects of lactate salts, 151–152 pyruvate, 151 ribose, 152 as essential nutrient, 37 fatigue and, 112 fiber, 119, 156–157 food intolerance and, 157–158 foods high in, 119–121 formation into protein, 218 glycemic index, 124–125 good and bad carbs, 153 grams of carbohydrates in select food, 140 healthful dietary guidelines for, 51 ingestion of, right before/during exercise exercise intensity and duration, 136–137 fatigue-delaying mechanisms of, 138–139 initial endogenous stores and, 136 timing of intake, 137–141 types of carbohydrate, 141–143 major functions of, 12, 128–129 metabolism of, 122–129 protein/carbohydrate mixture, 142–143, 231–232, 502, 503 reading food labels and, 62 refined sugars and starches effect on health, 153–154 replacement of during exercise in heat, 373–375

role in, protein metabolism during exercise, 221, 226–227, 231–232 simple, 118–119 stored in body, 91, 92, 125–128 types of, 118–119 weight loss low-carbohydrate, high fat weight-loss diets, 456 low-fat, high-carbohydrate weight-loss diets, 455 unprocessed for weight loss, 465 Cardiovascular disease alcohol consumption, 530–531 antioxidant supplements to prevent, 294–295 caffeine and, 539–540 high-protein diets and, 250–251 obesity and, 420 Cardiovascular strain, exercise in heat and, 366 Carmichael, Chris, 75 Carnitine dietary sources of, 188 as ergogenic aid, 188–189 Carnosine, 247–248 Carotenoids, role in metabolism, 57 Catabolism, 96 Cataracts, antioxidant supplements to prevent, 296 Catechin, 57 Celiac disease, 158 Cellulite, 405 Cellulose gel, 171 Central fatigue, 110, 111, 135, 234–235 Children excessive weight loss, 428 obesity/overweight diet, 419 health risks and, 423 importance of preventing, 418 incidence of, 403, 419 number of fat cells and, 414 physical inactivity, 419 television watching, 419 pesticide exposure, 69 physical performance and nutritional recommendations, 80 resistance training and, 518 resting energy expenditure and, 97 tolerating exercise in heat, 388 vegetarian diet and, 55 weight-loss programs for young athletes, 490 Chloride deficiency, 360 DRI, 359 food sources, 360 major functions, 360 overview of, 311, 360 Cholecalciferol, 266–267, 268–271 Cholesterol. See also HDL-cholesterol; LDL-cholesterol; Total cholesterol caffeine and, 539–540 defined, 172 dietary recommendations for, 174, 201 diet to reduce, 195–204 different forms of, and development of atherosclerosis, 192–194 drug therapy to reduce, 195 exercise training to reduce, 202, 205 foods that contain, 173 function in body, 178 guidelines for fasting blood levels of, 192–193 national guidelines for, 195 ratios of, 194 reading food labels and, 63 reducing, to reverse atherosclerosis, 194–195 risk factor for coronary heart disease, 192 vegetarian diet and, 56 Choline, 264, 266–267 deficiency, 282

defined, 282 DRI, 282 food sources, 282 major functions, 282 overview, 266–267 prudent recommendations, 282 supplementation, 282 Chondroitin, 238–240 Chromium, 334–337 deficiency, 335 DRI, 334 food sources, 334 major functions, 335 overview of, 311, 326 prudent recommendations, 336–337 supplementation, 335–336 Chromium picolinate, 335–336 Chronic diseases antioxidant supplements to prevent, 294–297 deaths from, 2 dietary guidelines for reducing, 48–53 exercise and nutrition, 2, 14 foods rich in vitamins, and preventing, 293–294 gene expression and exercise, 6 genetic influences, 2 physical inactivity and, 5 promoters and antipromoters, 12 refined sugar and, 153–154 Chronic fatigue syndrome, 110 Chronic training effect, 75 Chylomicron, 175, 177 Circuit aerobics, 519 Circuit weight training, 519 Cirrhosis, 529 Cis fatty acids, 169 dietary recommendations for, 174 Citrulline, 232–233 Ciwujia, 553 Clark, Nancy, 76 Clarkson, Priscilla, 286, 328 Cobalamin, 266–267, 278–281 Cobalt, 340 Coenzyme defined, 263 function of vitamins, 263 Coenzyme Q10, 289–290 Coleman, Ellen, 142 Colon cancer, fiber and, 157 Colostrum, 228 endurance training, 232 resistance training, 230 Commerford, Renee, 473 Compensated heat stress, 365 Complementary proteins, 55–56 Complete proteins, 55, 214 Complex carbohydrates benefits of fiber, 156–157 cholesterol-lowering recommendations, 201–202 defined, 119 health benefits of, 155–156 Concentric method of resistance training, 517 Conjugated linoleic acid, 174, 201 exercise performance and, 190 Cooper, Kenneth, 93, 483 Copper, 332–333 deficiency, 333 DRI, 332 food sources, 332 major functions, 332–333 overview of, 311, 326 prudent recommendations, 333 supplementation, 333 CoQ10, 289–290 Corbin, Chuck, 9 Core temperature, 361 Cori cycle, 128 Corn syrup, 119 Coronary heart disease, 191 alcohol consumption, 530–531

antioxidant supplements to prevent, 294–295 caffeine and, 539–540 cholesterol-reducing diet, 195–204 deaths from, 191 defined, 191 development of, 191–192 different forms of cholesterol and development of, 192–194 exercise to reduce risk of, 202, 205 high-protein diets and, 250–251 metabolic syndrome, 422 obesity and, 420 physical inactivity, 5 reducing serum lipid levels to reverse, 194–195 risk factors for, 192 Coronary occlusion, 192 Coronary thrombosis, 192 Cortisol, 132 abdominal fat, 421 stress and obesity, 417 Costill, David, 377 Coyle, Edward, 144, 377 Creatine, 212, 240–245 body mass and, 243 caffeine and, 243 effect on exercise performance, 241–243 medical applications of, 245 as nonessential nutrients, 38 resistance training and timing of, 502, 503 safety of, 244–245 supplement strategies, 240–241, 323 Crossover concept, 110 Cureton, Kirk, 536 Cycling, energy expenditure for, 104 Cytokines defined, 6 gene expression and exercise, 6–7 inflammation and, 7 Cytomax, 151

D Daily Value (DV), 39, 60–62 considerations when reading, 62 defined, 60 minimum/maximum allowances based on, 61, 62 DASH (Dietary Approaches to Stop Hypertension), 13–14, 195, 393–394 Davis, Mark, 137, 235 Deamination, 217 Deficiency conditions/diseases biotin, 281–282 boron, 338 calcium, 313–315 chloride, 360 choline, 282 chromium, 335 copper, 333 folate, 279–280 iron, 327–330 magnesium, 323–324 minerals, 310–312 niacin, 276–277 pantothenic acid, 281 phosphorus, 322 potassium, 360–361 of protein, 249–250 riboflavin, 276 selenium, 337 sodium, 358–359 stages of vitamin deficiency, 264–265 thiamin, 274 vitamin A, 268 vitamin B6, 277–278 vitamin B12, 279 vitamin B-complex, 283 vitamin C, 284

vitamin D, 270 vitamin E, 272 vitamin K, 273 zinc, 333–334 Dehydration creatine and, 244 defined, 355 excessive weight loss, 425 exercise performance and, 366–368 exercising in heat and maintaining water balance hyperhydration, 371 rehydration, 372 skin wetting, 370–371 heat exhaustion and, 386 heat stroke and, 386 involuntary, 367–368 physiological effects of, 367, 368 rate of, 368 voluntary, 367 Dehydroepiandrosterone (DHEA), effectiveness, legality, safety of, 550–551 Delayed onset of muscle soreness (DOMS), 222 Dental caries, refined sugar and, 153 Dextrose, 118 DHA (docasahexaenoic acid), cholesterollowering recommendations, 198–201 Diabesity, 420 Diabetes caffeine and, 540 as heart disease risk factor, 15 insulin resistance and cytokines, 6 metabolic syndrome, 422 obesity and, 420 physical activity and prevention, 6 refined sugar and, 153–154 vitamin D, 271 Diastolic pressure, 391 Dietary fiber. See Fiber Dietary folate equivalents (DFE), 279 Dietary guidelines basis for healthful, 47–48 Food Exchange System, 43 MyPyramid, 41–43 Prudent Healthy Diet, 48–53 for reducing chronic disease, 48–53 for vegetarians, 54 for weight gain, 501–505 balanced diet for, 503–505 Calories to form pound of muscle, 501 Calories to gain one pound/week, 501 dietary supplements for, 502–503 protein supplementation for, 501–502 for weight loss, 452–469 balanced weight-loss diets, 457 counting Calories for, 456–458 determining calories in foods, 458–461 determining Calories to lose weight, 452–453 fiber and, 455 Food Exchange System, 458 general guidelines for selection/preparation of food, 461–466 glycemic index and, 455 high-protein weight-loss diets, 456–457 increased difficulty to lose after several weeks, 454 low-carbohydrate, high fat weight-loss diets, 456 low-fat, high-carbohydrate weight-loss diets, 455 major characteristics of sound diet, 454–457 occasional overeating, 469 overview of popular diets, 455

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planning nutritionally balanced, low-Calorie diet, 467–468 portion sizes, 459, 462 predicting body-weight loss through diet alone, 453 very-low-Calorie diets, 468–469 in weight-control programs, 488–489 weight loss in first week, 453–454 Dietary Guidelines for Americans, 48, 153 Dietary-induced thermogenesis (DIT), 96 Dietary Reference Intakes (DRI), 12, 39 Dietary supplements, 66–68. See also Sports supplements; Vitamin supplements benefits from, 66–67 claims on label, 67 defined, 66 FDA regulations on, 66, 67 harmful effects from, 67–68 healthful dietary guidelines for, 52–53 safeguard recommendations for, 68 for weight-gaining programs, 502–503 weight-loss, 425–426 Dietary Supplements Health and Education Act (DSHEA), 22 Diffusion, 122–123 Digestion, 122 of carbohydrates, 123–124 of dietary fat, 175–176 of proteins, 217–218 Direct calorimetry, 88 Disaccharide, 118–119, 123 Disordered eating, 428 female athlete triad, 319–320 Dispensable amino acids, 213 Disuse principle, 5 Diuretics, to enhance performance, 380–381 Doping blood, 19 defined, 21 Doubly labeled water (DLW) technique, 89 Dual energy X-ray absorptiometry, 409 Dumping syndrome, 123 Duration concept, 474–475 Durnin, J.V., 22

E E. coli, 72 Earnest, Conrad, 550 Eating disorders, 428–432 anorexia athletica, 430 anorexia nervosa, 428–429 binge eating disorder, 429 bulimia nervosa, 429 defined, 428 disordered eating, 428 female athletes and, 80 female athlete triad, 319–320, 430–432 prevention, 431 purging disorder, 428 Eccentric exercise protein metabolism during recovery, 222 resistance training, 517 EER. See Estimated Energy Requirement (EER) Eggs, as good source of protein, 214 Eichner, Randy, 386 Eicosanoids, 178, 187, 188, 199 Elderly protein undernutrition, 249 risk for vitamin deficiency, 262 Electrolytes, 358–361 chloride, 359–360 daily replacement, 369, 375

622

Index

defined, 310, 358 excessive sweating and electrolyte deficiency, 369 potassium, 360–361 replacement of, during exercise in heat, 375 sodium, 358–359 sweating and, 369, 375 Electron transfer system, 93–94 Endurance athletes/exercise caffeine and, 536–537 carbohydrate loading, 145, 149 carbohydrates intake for, 130 dehydration, 367–368 dietary recommendations for protein, 223–224, 225 effect on carbohydrate metabolism, 131 exercise in heat glycerol supplements, 382–383 pre-cooling techniques, 381 sodium loading, 381–382 fat loading, 183–185 fat utilization during exercise, 182 high-protein diets and improved performance, 230–232 iron deficiency, 328–329 medium-chain triglycerides, 185–186 protein as energy source during, 220 protein metabolism and training, 222 sports anemia, 224 Energy. See also Human energy systems commonly used measure of, 89 defined, 86 forms of, 86 function of vitamins, 264 measuring expenditures of, 87–90 Energy drinks, 121 Energy expenditure, measurement of, 88–89 Engels, Hermann, 20 English system, 87 Enzymes, 263 EPA (eicosapentaenoic acid), cholesterollowering recommendations, 198–201 Ephedra (ephedrine), 21, 73, 426, 542–544 with caffeine, 543 defined, 542 health risks of, 543–544 permissibility of, 543 sports performance and, 542–543 synephrine, 544 Epidemiological research, 25 Epinephrine fat as energy source during exercise and, 180 released during exercise, 132 Equal, 154–155 Ergogenic aids, 19–21 alcohol, 527–529 anabolic hormones, 547–551 caffeine, 533–542 carbohydrates lactate salts, 151–152 pyruvate, 151 ribose, 152 categories of, 19 defined, 19 dietary fat carnitine supplements, 188–189 conjugated linoleic acid, 190 fasting, 185 fat loading, 183–185 hydroxycitrate, 189–190 medium-chain triglycerides, 185–186 Omega-3 fatty acids, 187–188 phospholipid dietary supplements, 186–187 effectiveness of, 20 ephedra, 542–544 herbs, 553–554 legality of, 21

popularity of, 20 protein, 228–249 arginine, 232–234 aspartates, 238 beta-alanine, 247–248 branched-chain amino acids (BCAA), 234–237 carnosine, 247–248 chondroitin, 238–240 citrulline, 232–233 colostrum, 228, 230 creatine, 240–245 endurance athletes and improved performance, 230–232 glucosamine, 238–240 glutamine, 237–238 glycine, 238 HMB (beta-hydroxy-betamethylbutyrate), 245–247 human growth hormone, 232–234 inosine, 248 lysine, 232–234 muscle mass increase and resistance training, 229–230 natural food vs. supplements, 228–229 ornithine, 232–234 taurine, 248 tryptophan, 234 tyrosine, 248 whey protein, 228, 230 recommendations on use of, 78 safety of, 20–21 sodium bicarbonate, 544–547 vitamin supplements antioxidant vitamins to prevent fatigue and muscle damage, 286–288 bee pollen, 289 bottom line for, 290 CoQ10, 289–290 multivitamin-mineral supplement for athletes, 288–289 quercetin, 290 reasons for athletes to take, 286 water glycerol supplements, 382–383 oxygen water, 381 pre-cooling, 381 sodium loading, 381–382 Ergometer, 87 Esophagus, 122 Essential amino acids, 213, 216 Essential fat, 405 Essential nutrients defined, 37 list of, 37 macronutrients, 37 micronutrients, 37 Ester, 168 Estimated Average Requirement (EAR), 39 Estimated Energy Requirement (EER), 39, 444–446 activity categories for, 445–446 calculating, 106–108 defined, 444 estimating with formula, 445–446 MyPyramid technique for estimating, 446–447 Ethanol, 526 Euhydration, 355 Evans, Gary, 335 Exercise. See also Exercise training programs; Physical activity Americans’ level of, 7 amount needed for health benefits, 7–8 bone health and, 318–319 calcium and, 318–319 carbohydrates as energy source for, 129–145 defined, 5 designing own, 481–483

determining energy cost of, 103 dietary fat as energy source during, 180–182 duration concept, 474–475 energy sources during, 109–110 energy system used during, 108–109 enjoyment of, 475 fatigue during, 108–113 frequency, 475 gene expression and, 6 glucose tolerance and, 158 guidelines for increasing, 8–10 health benefits of, 6–8 insulin sensitivity and, 158 intensity, 474 heart rate, 478–480 rating of perceived exertion, 480 talk test, 480 target HR range, 480–481 threshold stimulus, 478 metabolic rate determination, 101–103 metabolism during, 98–108 moderate-intensity, 8 practicality of, 475 to prevent hypertension, 395–396 problems with excessive amounts of, 10–11 protein as energy source during, 220–227 resting energy expenditure and, 105–106 role in health promotion, 5–7 stimulus period of, 477–478 thermic effect of food and, 106 versatility of, 475 vigorous, 8 warm-down, 476 warm-up, 476 in weight-control programs, 488–489 for weight loss, 469–487 Exercise-associated collapse, 385, 476 Exercise-associated hyponatremia, 375–376 Exercise in Medicine, 6 Exercise metabolic rate (EMR), 99 Exercise sequence principle, 507 Exercise snacks, 395, 474 Exercise training programs basic principles of, 5 breakfast and, 75–76 chronic training effect, 75 endurance training effect on carbohydrate metabolism, 131 fat metabolism during exercise and, 182 food during, 75–76 high-carbohydrate diet for daily program, 144–145 individuality, 5 overload, 5 overuse, 5 progression, 5 protein metabolism and, 222–223 recuperation, 5 to reduce cholesterol levels, 202, 205 reversibility, 5 specificity, 5 for sports performance, 15–16 Exertional heat stroke, 386 Experimental research, 25–27 Extracellular water, 354 Eye health, antioxidant supplements to prevent diseases of, 296

F Facilitated diffusion, 122 Fast food fat content of, 49–50 obesity and, 415–416 portion size, 462

Fasting fat metabolism and, 185 ketones and, 179 Fat, body. See also Obesity/overweight android-type obesity, 421–423 caffeine and oxidation of, 536 Calories in pound of, 443 converting to protein and carbohydrates to, 178, 444 deposition of, in body, 414 as energy source, 179 essential fat, 405 excessive, and sports performance, 432–433 gynoid-type obesity, 421–423 leptin and weight maintenance, 414 low-intensity exercise to burn more, 485–486 metabolic regulation, 178 optimal for athletes, 432–433 body fat percentage, 410–411 Body Mass Index for, 410 problems with body-fat percentages for sports, 409–410 spot reducing, 486 storage fat, 405 structure function of, 178 subcutaneous fat, 405 total body fat in body composition, 405 total energy stored in, 179 visceral fat, 405 Fat, dietary, 168–205 ATP formation from, 91 body’s need for, 173 calculating percentage of fat Calories, 170–171 Calories in one gram, 89–90 cholesterol coronary heart disease, 191–205 defined, 172 dietary recommendations for, 174 foods that contain, 172–173 cholesterol-lowering recommendations, 197–199 in common foods, 172 converting protein and carbohydrates to, 178 dietary recommendations for, 173–174 digestion and absorption of, 175–176 as energy source during exercise, 110 energy source during rest, 98, 128 ergogenic aspects carnitine supplements, 188–189 conjugated linoleic acid, 190 fasting, 185 fat loading, 183–185 hydroxycitrate, 189–190 medium-chain triglycerides, 185–186 Omega-3 fatty acids, 187–188 phospholipid dietary supplements, 186–187 as essential nutrient, 37 exercise and fat as energy source during, 180–182 fast foods and, 49–50 fat substitutes, 171–172, 201 foods high in, 169–170 formation into protein, 218 healthful dietary guidelines for, 49–50 hidden fat, 169 lipoproteins, 175–178 major function of, 12 metabolism of, 175–179 obesity causes high-fat, high-Calorie foods, 415–416 low-fat, large-portion size, highCalorie foods, 416 phospholipids, 173 reading food labels and, 62, 63 recommended intake of, 168 saturated, 169

stored in body, 91, 92 triglycerides, 168–169 unsaturated, 169 vegetarian diet and, 56 weight loss calculating daily fat intake, 463 general guidelines for selection/preparation of food, 462–464 low-carbohydrate, high fat weight-loss diets, 456 low-fat, high-carbohydrate weight-loss diets, 455 Fat-free mass, 405–406 Fatigue, 110–113 acute, 110 antioxidant supplements to prevent, 286–288 causes of, 110–112 central fatigue, 110, 111, 135 central neural fatigue and exercise in heat, 366 chronic, 110 defined, 110 delay onset of, 112 fatigue-delaying mechanisms of carbohydrate ingestion, 138–139 hypoglycemia related to, 131–133 lactic acid production related to, 133–134 low endogenous carbohydrate levels and central fatigue hypothesis, 135 low muscle glycogen related to, 134–135 nutrition related to, 112 overreaching, 110 overtraining, 110 peripheral, 111 Fat loading acute, 183 chronic, 183–184 defined, 183 ergogenic effect, 184–185 Fat-soluble vitamins guidelines for choosing supplements, 299 Vitamin A, 265, 268 Vitamin D, 268–271 Vitamin E, 271–273 Vitamin K, 273–274 Fat substitutes, 171–172, 201, 463 Fatty acids characteristics of, 169 cis, 169 defined, 168 saturated, 169 trans, 169 types of, 169 unsaturated, 169 Febbraio, Mark, 366 Feedback system for weight control, 413–414 Female athletes anorexia athletica, 430 female athlete triad, 319–320, 430–432 iron deficiency, 328 nutritional recommendations, 80 Female athlete triad, 319–320, 430–432 amenorrhea, 430–431 disordered eating, 430 osteoporosis, 431 prevention, 431 treatment, 432 warning signs, 431 Ferritins, 327 Fetal alcohol effects (FAE), 531 Fetal alcohol syndrome (FAS), 531 Fiber benefits of, 56–57 cholesterol-lowering recommendations, 201–202 colon cancer and, 157

dietary, 119 dietary recommendations for, 121, 156 functional, 119 glycemic index and, 125 health benefits of, 156–157 reading food labels and, 62, 63 total, 119 vegetarian diet and, 56–57 water-insoluble, 119, 156 water-soluble, 119 weight-loss diets and, 455 Fish cholesterol-lowering dietary recommendations, 199–201 as good source of protein, 214 Fish oil supplements, 199–201 Fitness, 4. See also Health-related fitness; Sports-related fitness Fitts, Robert, 110 Flavonoid, 57 Fleck, Steven, 510 Flexibility as component of health-related fitness, 4 exercise recommendation guidelines, 9 Fluid replacement. See Heat, exercise in; Water Fluoride healthful dietary guidelines for, 52 major functions, 340–341 overview of, 311, 340 Fluorosis, 340 Fogelholm, Michael, 286 Folate (folic acid), 279–281 deficiency, 279–280 DRI, 279 food sources, 279 major functions, 279 overview, 266–267 prevention of birth defects, 39 prudent recommendations, 280–281 supplementation, 280 vegetarian diet and, 57 Food additives allergic response, 74 defined, 73 healthful dietary guidelines for, 52 purposes of, 73 safety of, 73 Food allergies defined, 74 food labels and, 62 incidence of, 74 major food allergens, 74 mechanism of, 74 Food and Drug Administration (FDA) approved health claims, 62, 64, 65 regulations on dietary supplement labels, 66, 67 Food categories, 41 Food drugs alcohol, 526–533 caffeine, 533–542 Food Exchange System, 43 list of various foods, 458, 459 overview of, 458 Food Guide Pyramid, 47 Food guides Food Exchange System, 43 MyPyramid, 41–43 Prudent Healthy Diet, 48–53 for vegetarians, 54 Food intolerance, 73 gluten intolerance, 158 lactose intolerance, 157–158 Food labels, 60–65 considerations when reading, 62 Daily Value (DV), 60–62 definitions of terms used on, 63 functional foods, 64 health claims allowed on, 62, 64, 65 information provided by, 60 legislation on, 60

Nutrition Facts, 60, 61 organic food, 70 Food poisoning, 72–73 common sources of, 72 defined, 72 irradiation, 72 preventing, 72–73 symptoms of, 72 Food processing commercial, 71 at home, 71–72 Food safety, 68–74 biotechnology and, 68–69 commercial food processing and, 71 food additives, 73 food poisoning, 72–73 genetically modified (GM) foods, 68–69 healthful dietary guidelines for, 52 home food processing and, 71–72 organic foods, 70–71 pesticides, 69–70 Forbes, Gilbert, 501 Fortification, functional foods, 64 Free radicals, 263 Fructose, 118 dumping syndrome, 123 glycemic index of, 124 health effect of, 153–154 ingesting right before exercise, 141–142 intolerance, 74 in sports drinks, 141 Fruits, 41 color of, and phytochemicals, 58 eat more, for weight loss, 465 healthful dietary guidelines for, 50 pesticide content of, 70 rising cost of, 36 Functional fiber, 119 Functional foods defined, 64 fortification and, 64

G Gaesser, Glenn, 424 Galactose, 118 Gallbladder, 122 Gastric emptying, exercising in heat and, 372–373 Gastrointestinal distress caffeine and, 541 creatine and, 244 dehydration and, 368 sports drinks, 373, 374 Gender alcohol and health risks, 529 Calorie needs and, 444 fat as energy source during exercise and, 181–182 physical performance and nutritional recommendations, 80 resting energy expenditure and, 97 tolerating exercise in heat, 388 Generally recognized as safe (GRAS), 73 Genetically modified (GM) foods, 68–69 Genetics athletic performance and, 15 chronic diseases and, 2 gene expression and exercise, 2, 6 obesity and, 415 resting energy expenditure and, 97 sports performance and, 3 Genistein, 57 Gerberding, Julie, 421 Ghrelin, 413–414 exercise-induced weight-loss and, 473 high-protein weight-loss diets, 456 sleep and, 417 Ginseng, 21, 552–553 Girth measurements, 409

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Glucagon, 132 Glucogenic amino acids, 217 Gluconeogenesis, 128, 129, 217, 221 Glucosamine, 238–240 Glucose, 118 blood glucose, 124–125 lactic acid system, 93 in sports drinks, 141 Glucose-alanine cycle, 128, 220–221 Glucose polymers, 119 Glucose tolerance, 158 Glucostatic theory, 412 Glutamine, 237–238 Gluten intolerance, 158 Glycemic index defined, 124 factors affecting, 124–125 fiber and, 156–157 for specific foods, 126 weight-loss diets and, 455 Glycemic load calculating, 125 defined, 125 for specific foods, 126 Glycerol, 128, 168–169 defined, 169 as ergogenic aid, 186 Glycerol supplements, exercising in heat and, 382–383 Glycine, 238 Glycogen loading, 145 Glycolysis, 93 Glycoproteins, 129 Goiters, 341 Good source on food label, 63 Gout, high-protein diet and, 252 Graham, Terry, 536 Greenleaf, John, 367 Guar gum, 171 Gum arabic, 171 Gynoid-type obesity, 421–423

H Hagberg, James, 3 Hargreaves, Mark, 77 Hawley, John, 75, 190 HDL-cholesterol alcohol consumption and, 532 characteristics of, 177, 178 development of atherosclerosis, 194 guidelines for fasting blood levels of, 192–193 Health claims on dietary supplement label, 67 on food labels, 62, 64 , 65 Health-related fitness amount of physical activity for, 7–10 components of, 4 defined, 4 measures of, 4 nutrition and, 11–15 principles of exercise training, 5 role of exercise in, 5–6 Healthy People 2010, 3, 153, 168 physical activity objectives of, 6 Heart disease. See also Coronary heart disease refined sugar and, 153–154 risk factors, 15 whole-grain intake and, 155 Heart rate exercise and maximal heart rate reserve, 478–479 target heart rate range, 479–480 obtaining, 478, 479 Heat, exercise in, 365–380 acclimatization, 389–390 caffeine and, 538 carbohydrate metabolism during, 130, 150

624

Index

carbohydrate replacement during, 373–375 electrolyte replacement, 375 ergogenic aspects of water, 380–383 glycerol supplements, 382–383 oxygen water, 381 pre-cooling, 381 sodium loading, 381–382 excessive sweating and electrolyte deficiency, 369 factors associated with heat injury, 388–389 gastric emptying and intestinal absorption, 372–373 guidelines for, 384 health hazards heat cramps, 385–386 heat exhaustion, 386 heat stroke, 386 heat syncope, 385 hyperthermia, 363–364 hyponatremia, 375–376 maintaining water balance during hyperhydration, 371 rehydration, 372 skin wetting, 370–371 performance cardiovascular strain, 366 central neural fatigue, 366 compensated heat stress, 365 dehydration, 366–368 hypohydration, 367 muscle metabolism, 366 uncompensated heat stress, 365 preventing heat injury, 389 prudent guidelines for fluid replacement, 377–380 rate of dehydration, 368 salt tablets or potassium supplements, 376–377 sports drinks and, 370 sweat composition, 369 sweat rate, 368–369 Heat, specific, 365 Heat-balance equation, 362 Heat cramps, 385–386, 387 Heat exhaustion, 386, 387 Heat illness, 11, 384–390 acclimatization, 389–390 factors associated with heat injury, 388–389 guidelines for exercise in heat, 384 health hazards heat cramps, 385–386 heat exhaustion, 386 heat stroke, 386 heat syncope, 385 high-protein diet and, 252 preventing, 389 symptoms and treatment of, 386–387 Heat index chart for, 364 as indicator of heat stress, 364 Heat stress, indicators of heat index, 364 WBGT Index, 363–364 Heat stroke, 386, 387 Heat syncope, 385, 387 Hematuria, 328–329 Heme iron, 325 Hemochromatosis, 331 Hemoglobin function of, 12 long distance runners and, 75 Herbicides, 69 Herbs, ergogenic effects, 551–554 Heredity. See Genetics Hespel, Peter, 243, 245 Heterocyclic amines (HCA), 52 Hidden fat, 169 High blood pressure, 390–396 calcium, 316–317 classification of, 392 dangers of, 391–392

defined, 391 dietary modifications for, 392–395 exercise to prevent/treat, 395–396 incidence of, 391 magnesium and, 324 physical inactivity, 5 risk factor for coronary heart disease, 192 as silent disease, 391 symptoms of, 391 treatment for, 392 High-glycemic foods chronic diseases and, 153–154 defined, 124 examples of, 126 ingesting right before exercise, 142 High-intensity exercise carbohydrate intake for, 136–137 carbohydrates intake for, 130 Hill, James, 473, 490 Hiller, Doug, 376 Hippocampus, set-point theory, 414 Hippocrates, 12, 36 HMB (beta-hydroxy-betamethylbutyrate), 245–247 Homeostasis, 355 Homocysteine, 279 caffeine and, 539–540 Hormone replacement therapy, calcium and, 319 Hormones appetite and, 412 function of vitamins, 264 metabolism and, 413 that regulate blood glucose, 132–133 Human energy systems, 86–113 ATP-PCr system, 92–93 best activities to increase energy expenditures, 103–105 commonly used measure of, 89 energy cost of exercise, 103 energy expenditure measurement, 88–89 energy sources during exercise, 109–110 energy stored in body, 90–91, 92 Estimated Energy Requirement (EER), 106–108 during exercise, 98–109 fatigue during exercise, 108–113 lactic acid system, 93 metabolism defined, 96 nutrients necessary for, 95 oxygen system, 93–94 during rest, 96–98 work measurement, 87–88 Human Genome Project, 2 Human growth hormone (HGH), 232–234 effectiveness, legality, safety of, 547–548 Hunger center, 412 Hydrodensitometry, 407–408 Hydroxycitrate, 189–190 Hyperplasia, 414 Hyperglycemia, 125 Hyperhydration defined, 355 to maintain water balance during exercise, 371 Hyperkalemia, 361 Hypertension, 390–396 caffeine and, 539 classification of, 392 dangers of, 391–392 defined, 391 dietary modifications for, 392–395 exercise to prevent/treat, 395–396 incidence of, 391 physical inactivity, 5 as silent disease, 391 symptoms of, 391 treatment for, 392

Hyperthermia conditions predispose athlete to, 363–364 defined, 363 Hypertrophy, 414 Hypervitaminosis, 265 Hypnosis, as ergogenic aid, 19 Hypoglycemia, 125 during exercise, 132, 133 fatigue and, 131–133 Hypohydration defined, 355 exercise performance and, 367 Hypokalemia, 361 Hyponatremia defined, 375 risk factors, 375 signs of, 375 sports drinks and, 376 symptoms and treatment of, 387 Hypothalamus appetite control, 412–413 in body temperature regulation, 362–363 set-point theory, 414 Hypothermia, 363

I Immune system excessive exercise, 10 glutamine and, 237–238 Incomplete proteins, 55, 214 Indirect calorimetry, 88 Indispensable amino acids, 213 Individuality principle, 5 Indoles, 57 Inflammation exercise and reducing, 7 plaque and, 192 Infrared interactance, 409 Inosine, 212, 248 Insensible perspiration, 353 Insulin, function of, 125, 127 Insulin resistance cytokines and exercise, 6 high- and low-glycemic foods and, 153–154 refined sugar and, 153–154 Insulin sensitivity, exercise and, 158 Intelligent Device for Energy Expenditure and Activity (IDEEA), 88 Intensity, exercise, 474 heart rate and, 478–480 low-intensity exercise to burn more, 485–486 rating of perceived exertion, 480 for resistance training, 505 talk test, 480 target HR range, 480–481 threshold stimulus, 478 Intercellular water, 354 International Society of Sports Nutrition, 16 International Unit System, 87 Interval training, 482–483 Intervention studies, 25–26 Intestines, large, 122 Intestines, small, 122 Intracellular water, 354 Intramyocellular triacylglycerol, 175 Intravascular water, 354 Iodine major functions, 341 overview of, 311, 340 vegetarian diet and, 55 Ions, 309–310 Iron, 325–332 deficiency, 327–330 with anemia, 328, 330–331 in athletes, 328–330 incidence of, 327 sports anemia, 329

stages of, 327–328 without anemia, 328, 329–330 DRI, 325 excessive levels of, 331–332 food sources, 45, 55, 325–327 gastrointestinal loss of, 222 healthful dietary guidelines for, 52 iron saturated, 331 as key-nutrient, 45 live high, train low, 331 long distance runners and, 75 major functions, 327 in muscle-cell energy process, 95 overview of, 311, 326 prudent recommendations, 332 sports anemia, 224 supplementation, 330–332 vegetarian diet and, 55 vitamin C and absorption of, 55 Iron-deficiency anemia, 328, 330–331 Iron deficiency without anemia, 328, 329–330 Irradiation, 72 Ischemia, 192 Isoflavones, 57 Isokinetic resistance training, 516–517 Isoleucine, 234 Isometric resistance training, 516–517 Isothlocyanates, 57 Isotonic resistance training, 516–517 Ivy, John, 143

J Jacobs, Ira, 543 Jenkins, David, 202 Jenny Craig, 455 Jeukendrup, Asker, 108, 374 Joints, high-protein diets and, 252 Joule, 87

K Kalmar, Jayne, 535 Kearney, Jay, 16 Keith, Robert, 502 Kenney, Larry, 388 Keshan disease, 337 Ketogenic amino acids, 217 Ketones, 179, 181 Ketosis, 179 Key-nutrient concept, 43–45 Kidneys creatine and, 244 high-protein diets and, 251–252 Kidney stones calcium supplements and, 318 high-protein diet and, 252 megadoses of vitamin C, 285 vitamin D, 271 Kilojoules converting Calories to, 89 defined, 89 Kleiner, Susan, 501 Koop, C. Everett, 482 Kouros, Yannis, 130 Kraemer, William, 189, 510 Krebs cycle, 93–94, 128 Kreider, Richard, 246, 322 Kris-Etherton, Penny, 191

L Lactate, 128, 134 Lactate salts, 151–152 Lactate shuttle, 134 Lactic acid, 128, 131 fatigue and, 113 production of and fatigue, 133–134 sodium bicarbonate and, 545–546

Lactic acid energy system, 93 creatine and, 242 energy source during exercise and, 108–110 Lactose, 118 Lactose intolerance, 74, 157–158 calcium intake and, 158 Lactovegetarians, 54 Lane, Helen, 333 LDL-cholesterol characteristics of, 177, 178 development of atherosclerosis, 194 guidelines for fasting blood levels of, 192–193 Lean body mass, 406 Lecithin, 173, 282 as ergogenic aid, 186 Legumes, as good source of protein, 214 Lemon, Peter, 224, 225, 500, 501 Leptin, 178 defined, 414 set-point theory, 414 sleep and, 417 Leucine, 220–221, 234 Levulose, 118 Life expectancy obesity and, 421 physical activity and, 6 Lightsey, David, 23 Limiting amino acid, 214 Limonene, 57 Lindeman, Alice, 374 Linoleic acid, 174 Lipoproteins characteristics of, 177, 178 defined, 175 parts of, 176 types of, 177–178 Lipostatic theory, 412 Liquid meals, 77–78 Liver, 122 alcohol metabolism, 526–527 creatine and, 244 dietary fat metabolism and, 175–176 high-protein diets and, 251–252 liver disease and alcohol use, 529 Liver glycogen, 125, 127–128, 131 Long-haul concept of weight control, 471 Loucks, Anne, 320, 430 Low active category, 107, 445 Low-Calorie diets resting energy expenditure, 97 vegetarian diet as, 57 very-low-Calorie diets, 427 Low-fat diets low-fat, high-carbohydrate weightloss diets, 455 vegetarian diet and, 56 Low-glycemic foods defined, 124 examples of, 126 ingesting right before exercise, 142 Lukaski, Henry, 324 Lutein, 57, 58 Lycopene, 57 Lysine, 232–234

M Macrominerals calcium, 312–321 defined, 312 magnesium, 232–325 phosphorus, 321–323 Macronutrients, 37 Macular degeneration, antioxidant supplements to prevent, 296 Magnesium, 232–325 deficiency, 323–324 DRI, 323 food sources, 323 major functions, 323 overview of, 311, 313

prudent recommendations, 325 supplementation, 324–325 Ma huang, 542 Malnutrition defined, 18 mineral deficiency, 311 protein deficiency, 249–250 sports performance and, 18 vitamin deficiency, 264–265 Maltose, 118 Manganese, 311, 340 Manore, Melinda, 18, 121, 144, 290, 430 Maresh, Carl, 286 Maughan, Ron, 21, 75, 365, 377 Maximal heart rate reserve, 478–479 Maximal oxygen uptake, 100 McGwire, Mark, 22, 551 Meats, 41 cancer and, 250 eat low-fat for weight loss, 464–465 as good source of protein, 214, 215 grilling, 52 hamburger and cholesterol-lowering recommendations, 197 healthful dietary guidelines for, 51–52 Mechanical aids, 19 Medical foods, 64 Mediterranean diet, 456 cholesterol-lowering recommendations, 198 Medium-chain triglycerides, 175 endurance performance and, 185–186 Menadione, 273–274 Mental alertness, caffeine and, 535, 540–541 Mental health, antioxidant supplements to prevent diseases of, 296 Meta-analysis, 27 Metabolic aftereffects of exercise, 105 Metabolic rate determining, during exercise, 101–103 exercise metabolic rate (EMR), 99 heart rate and, 102–103 muscular exercise effect on, 99–100 Metabolic syndrome, 422 Metabolic water, 353 Metabolism alcohol, 526–527, 528 anabolism, 96 blood glucose, 125 caffeine and, 98 of carbohydrates, 122–129 catabolism, 96 defined, 96 of dietary fat, 175–179 effect of eating meal, 96 during exercise, 98–108 mineral’s role in, 309–310 muscle’s influence on, 98–108 of proteins, 217–219 resting, 96–98 total daily energy expenditure (TDEE), 96 units for expression of, 101 weight maintenance and, 412–413 Metalloenzymes, 309 Metric system, 87 Micronutrients, 37 Milk, 41 eat low-fat dairy products for weight loss, 464 as good calcium source, 312 as good source of protein, 214, 215 reading food labels and, 63 Millard-Stafford, Mindy, 374 Millimole, 125, 127 Minerals, 309–343. See also Mineral supplements; specific minerals athletes’ need for mineral supplements, 343 deficiencies of, 310–312 defined, 309

essential minerals, 310, 311 as essential nutrient, 37 exercise and increased need for, 341 food sources for, 341–342 functions of energy and, 310 growth and development, 309 metabolic regulation, 309–310 macrominerals calcium, 312–321 defined, 312 magnesium, 232–325 phosphorus, 321–323 megadoses, 342–343 in muscle-cell energy process, 95 overview of essential, 311 trace boron, 338–339 chromium, 334–337 copper, 332–333 defined, 325 fluoride, 340–341 iodine, 341 iron, 325–332 other, 340 selenium, 337–338 vanadium, 339 zinc, 333–334 for vegetarian diet, 55 Mineral supplements boron, 338–339 calcium, 317–318 chromium, 335–336 copper, 333 guidelines for choosing supplements, 297–299 iron, 330–332 magnesium, 324–325 multivitamin-mineral supplements effectiveness of, 288–289 need for taking, 343 phosphorus, 322–323 selenium, 337–338 vanadium, 339 zinc, 334 Mitochondria, 93 Moderate-intensity exercise, 8, 9 Moderation in healthful diet, 36 in MyPyramid, 41 Modified fast, 427 Molybdenum, 311, 340 Monosaccharides, 118–119, 123 Monounsaturated fats cholesterol-lowering recommendations, 198 dietary recommendations for, 174 Monounsaturated fatty acids, 169 Montain, Scott, 377 Morbid obesity, 410 Morgan, William, 552–553 Multivitamin-mineral supplements, effectiveness of, 288–289 Muscle glycogen, 125, 127–128, 130–131 caffeine and sparing, 536 carbohydrate loading and, 148 carbohydrate replenishment after exercise, 143–144 fatigue and low levels of, 134–135 sparing of, and carbohydrate ingestion, 139 Muscle hypertrophy, 515–516 Muscles antioxidant supplements to prevent muscle damage, 286–288 caffeine and, 535, 536 creatine and muscle mass, 243 endurance/strength as component of health-related fitness, 4 endurance training and carbohydrate metabolism, 131 energy produced during exercise, 98–99

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exercise in heat and metabolism of, 366 muscle mass increase from highprotein diets and resistance training, 229–230 muscular exercise and metabolism, 99–100 proteins and building, 212 resistance training for building, 505–519 resting energy expenditure and, 97 types of muscle fibers, 99 weight gain balanced diet for, 503–505 Calories to form pound of, 501 dietary supplements for, 502–503 protein supplementation for, 501–502 Myocardial infarct, 192 MyPyramid criticism of, 47 overview of, 41–43

N National Cholesterol Education Program, 195 NEAT. See Nonexercise activity thermogenesis (NEAT) Neotame, 154, 155 Neuropeptides, 412 Newsholme, Eric, 234 Niacin, 276–277 deficiency, 276–277 DRI, 276 food sources, 45, 276 as key-nutrient, 45 major functions, 276 in muscle-cell energy process, 95 overview, 266–267 prudent recommendations, 277 supplementation, 277 Niacin equivalents (NE), 276 Nicotine, obesity and, 417 Nieman, David, 290 Nitrogen balance, 214 Noakes, Tim, 288, 367, 377, 547 Nonessential amino acids, 213 Nonessential nutrients, 38 Nonexercise activity thermogenesis (NEAT) defined, 106, 413 increasing, 469 physical inactivity and obesity, 416–417 Normohydration, 355 Nutraceuticals, 57 NutraSweet, 154–155 Nutrient density defined, 45 rising cost of food high in, 36 vegetarian diet and, 56 Nutrients absorption of, 122–123 antipromoters, 12 defined, 11 developing recommended dietary intakes of, 38–40 essential, 37 key-nutrient concept, 43–45 major functions of, 11–12 nonessential, 38 promoters, 12 role in sports performance, 18 Nutrition. See also Sports nutrition American diet, 12–13 chronic diseases and, 12 defined, 11 guidelines for healthy eating, 13–14 Prudent Healthy Diet, 14 role in health promotion, 12 Nutritional aids, 19 Nutritional consultants, 24–25 Nutritional labeling, 60

626

Index

Nutritional quackery, 21–25 advertising and, 22–23 combating, 23–25 defined, 21 prevalence with athletes, 22–23 recognizing, 23 Nutrition Facts, 60, 61 Nutrition Labeling and Education Act, 60

O Oatrim, 171 Obesity/overweight alcohol and, 531–532 android-type obesity, 421–423 causes of, 415–418 alcohol and nicotine, 417 emotional stress, 417 environmental factors, 415 genetic factors, 415 high-fat, high-Calorie foods, 415–416 interaction of genetics and environment, 417–418 liquid Calories, 416 low-fat, large-portion size, highCalorie foods, 416 personal relationships, 417 physical inactivity and NEAT, 416–417 sleep, 417 children diet and, 419 health risks and, 423 importance of preventing, 418 incidence of, 403, 419 number of fat cells and, 414 physical inactivity, 419 television watching, 419 defined, 410 gynoid-type obesity, 421–423 health effects cancer, 420–421 cardiovascular disease, 420 location of fat on body and, 421–423 maternal health, 421 metabolic syndrome, 422 mortality, morbidity and quality of life, 421 physical fitness reducing adverse, 424 weight loss to improve health, 423 as heart disease risk factor, 15 incidence of, 403 increase in, 403 morbid obesity, 410 negative judgments of, 403 number of fat cells and, 414 prevention of, 490–491 refined sugar, 153–154 thermic effect of food and, 96 tolerating exercise in heat and, 388 as world epidemic, 403 Observational research, 25 Older athletes physical performance and nutritional recommendations, 80 tolerating exercise in heat, 388 Olestra, 73, 171–172, 201 Olive oil, 198 Olympics alcohol and, 525, 529 caffeine and, 538–539 Omega-3 fatty acids, 169 cholesterol-lowering recommendations, 198–201 dietary recommendations for, 174 as ergogenic aid, 187–188 Omega-6 fatty acids, 169 cholesterol-lowering recommendations, 198–201 dietary recommendations for, 174

OmniHeart diet, 13–14, 195, 198 consumption of healthier carbohydrates, 155 healthy protein rich foods, 250–251 Onset of blood lactic acid, 100 Oral rehydration therapy solutions, 352 Organic foods, 70–71 bacteria, 70 labeling, 70 nutritional value and, 70–71 pesticides and, 70 Organic junk food, 70 Ornish, 455 Ornish, Dean, 452, 455, 461 Ornithine, 232–234 Osmolality, 355 Osmosis, 122–123 Osmotic pressure, 355 Osteomalacia, 270 Osteoporosis, 11 caffeine and, 541 defined, 315 estrogen and, 315 female athlete triad, 319–320, 431 hormone replacement therapy and, 319 lifestyle factors and, 315 physical inactivity, 5 risk factors for, 315, 316 in sports, 319–320 Overload principle, 5, 506 Overnutrition, 18 Overreaching, 110 Overtraining syndrome, 110, 222, 237 Overuse principle, 5 Ovolactovegetarian, 54 Ovovegetarians, 54 Oxalates, 55 Oxidative system, 93 Oxygen system, 93–94, 128 creatine and, 242–243 energy source during exercise, 108–110 as energy source during rest, 98 Oxygen water, 381

P Pancreas, 122 Pancreatic cancer, refined sugar and soda, 154 Pandolf, Kent, 367 Pangrazi, Robert, 9 Pantothenic acid, 281 deficiency, 281 DRI, 281 food sources, 281 major functions, 281 overview, 266–267 prudent recommendations, 281 supplementation, 281 Partially hydrogenated fats, 169 PCr. See Phosphocreatine (PCr) Peak bone mass, 315 Pear-shape obesity, 421–423 Pedometer, 87 Performance. See Sports performance Performance water, 381 Periodization, 508 Peripheral fatigue, 111 Personal trainers, 490 Pescovegetarians, 54 Pesticides food safety and, 69 fruits/vegetables with low/high content of, 70 organic foods and, 70 reducing exposure to, 69–70 Pharmacological aids, 19 Phenolic acids, 57 Phillips, Stuart, 502 Phosphagen system, 92 Phosphatidylserine, 186–187

Phosphocreatine (PCr) ATP-PCr system, 92–93 defined, 91 fatigue and, 113 stored in body, 91, 92 Phospholipids defined, 173 as ergogenic aids, 186–187 foods that contain, 173 Phosphorus, 321–323 deficiency, 322 DRI, 321 food sources, 321 major functions, 321 overview of, 311, 313 supplementation, 322–323 Physical activity. See also Exercise Americans’ level of, 7 amount needed for health benefits, 7–8 defined, 4–5 diabetes prevention and, 6 in estimating Calories to maintain weight, 445–446 guidelines for increasing, 8–10 life expectancy and, 6 obesity and health, 424 structured, 5 unstructured, 5 Physical activity level (PAL) categories, 106, 107 Physical Activity Pyramid, 9–10 Physical activity quotient, 444, 445–446 Physical fitness, 4 Physical inactivity as cause of obesity, 416–417 childhood obesity, 419 chronic disease and, 5 cost of, 5 nonexercise activity thermogenesis (NEAT) and, 416–417 Physical performance. See Sports performance Physiological aids, 19 Phytates, 55 Phytochemicals colors of fruits and vegetables, 58 defined, 57 in fruits and vegetables, 51 list of, and food sources, 57 as nonessential nutrients, 38 role in metabolism, 57 vegetarian diet and, 57–58 Phytoestrogens, 57 Plant proteins, 213–214 Plaque cholesterol and formation of, 192–194 defined, 192 Plato, 5 PMS (premenstrual syndrome), calcium supplements, 318 Polypeptide, 213 Polyphenols, 57 Polysaccharides, 119, 123 Polyunsaturated fats, dietary recommendations for, 174 Polyunsaturated fatty acids, 169 cholesterol-lowering recommendations, 198–201 Portion size, 459, 462 Potassium deficiency, 360–361 DRI, 360 excess, 361 food sources, 360, 361 major functions, 360 overview of, 311, 360 supplements and exercising in heat, 376–377 Power, 87 Precompetition meal example meals, 77 guidelines for, 76–77 liquid meal, 78 Pre-cooling, to enhance performance, 381

Pregnancy alcohol and, 531 caffeine and, 541 obesity and, 421 Pritikin, Nathan, 455 Pritikin program, 155 Progression principle, 5, 506–507 Prohormones, effectiveness, legality, safety of, 550–551 Promoters, 12 Proportionality, in MyPyramid, 41 Prostaglandin, 187 Protein, 212–253 aerobic endurance exercise and, 220 animal vs. plant protein, 213–214 ATP formation from, 91 Calories in one gram, 90 characteristics of, 212–213 complementary, 55–56 complete, 55, 214 converting to fat, 178, 444 deficiency of, 249–250 defined, 212 dietary recommendations for athletes, 224–227 endurance training, 223, 224, 225 in general, 214–217 strength training, 223–224, 225 digestion and absorption of, 217–218 ergogenic aspects of, 228–249 arginine, 232–234 aspartates, 238 beta-alanine, 247–248 branched-chain amino acids (BCAA), 234–237 carnosine, 247–248 chondroitin, 238–240 citrulline, 232–233 colostrum, 228, 230 creatine, 240–245 endurance athletes and improved performance, 230–232 glucosamine, 238–240 glutamine, 237–238 glycine, 238 HMB (beta-hydroxy-betamethylbutyrate), 245–247 human growth hormone, 232–234 inosine, 248 lysine, 232–234 muscle mass increase and resistance training, 229–230 natural food vs. supplements, 228–229 ornithine, 232–234 taurine, 248 tryptophan, 234 tyrosine, 248 whey protein, 228, 230 as essential nutrient, 37 exercise and carbohydrate and protein intake after, 226–227 as energy source during, 220–221 leucine and glucose-alanine cycle, 220–221 metabolism during recovery after, 222 need for more protein with strenuous training, 223–224 nutrient timing and performance, 227 protein intake after, 226 protein intake before, 226 protein loss, 221–222 training effect on metabolism, 222–223 food sources, 45, 214, 215 formed from carbohydrates and fats, 218 functions of, 219 healthful dietary guidelines for, 51–52 high-protein diets, 250–252 incomplete, 55, 214

as key-nutrient, 45 major function of, 12 metabolism of, 217–219 resistance training and, 220 as source for blood glucose, 128 soy, 251 stored in body, 92 vegetarian diet and, 55–56 for weight gain of one pound/week, 501–502 weight loss, high-protein weight-loss diets, 456–457 Protein/carbohydrate mixture after exercise, 143 chocolate milk as, 502, 503 before exercise, 142–143 improving endurance performance, 231–232 resistance training and timing of, 502 Protein hydrolysate, 226 Protein-sparing effect, 219 Proteinuria, 221 Prudent Healthy Diet, 48–53 alcoholic beverages, 51 balance food with activity, 48–49 basic premise of, 36 calcium and iron, 52 cholesterol-lowering recommendations, 196–202 defined, 14 enjoy food with balance, 53 food additives, 52 food safety, 52 food supplements, 52–53 fruits and vegetables, 50 guidelines for, 14 moderate total fat, 49–50 protein, 51–52 salt and sodium, 51 sugar intake, 51 variety, 49 Psychological aids, 19 Purging disorder, 428 Purines, 248 Pyruvate, 128 ergogenic effect of, 152

Q Quackery. See Nutritional quackery Quercetin, 57, 290

R Randomized clinical trials (RCTs), 25–26 Rating of perceived exertion, 480 caffeine and, 537 Reactive hypoglycemia, 125 Reaven, Gerald, 422 Recommended Dietary Allowance (RDA), 12 defined, 39 development of, 38–39 Recovery period defined, 505 protein metabolism during, 222 Recovery principle, 5 Recuperation principle, 5, 507–508 Refined sugar cholesterol-lowering recommendations and, 201–202 chronic diseases and, 153–154 tips for decreasing, 154 weight loss and eating less, 464 Regional fat distribution, 409 Rehrer, Nancy, 368, 376 Rehydration, to maintain water balance during exercise, 371 Rennie, Michael, 224 Repetition, 505 Repetition maximum, 505

Research contradictory advice and, 27 epidemiological, 25 experimental, 25–27 Resistance training basic terminology for, 505 benefits of, 499, 518–519 children and elderly, 518 circuit weight training, 519 contraindications, 518 Creatine and, 502, 503 energy expenditure for, 105 example program for, 508–510 exercises for bench press, 510 bent-arm pullover, 511 curl-up, 515 half-squat, 512 heel raise, 514 lat machine pulldown, 511 seated overhead press, 515 standing curl, 514 standing lateral raise, 513 methods of, and effectiveness, 516–517 muscle hypertrophy, 515–516 principles of, 506–508 exercise sequence, 507 overload, 506 periodization, 508 progression, 506–507 recuperation, 507–508 specificity, 507 protein recommendations and dietary recommendations for protein, 223–224, 225 high-protein diets and increased muscle mass, 229–230 protein as energy source during, 220 protein/carbohydrate mixture, 502 protein metabolism and training, 222 protein metabolism during recovery, 222 purposes of, 505–506 recommendation guidelines, 9 resting energy expenditure (REE) and, 470 safety concerns breathing technique, 510–513 spotter, 513 Valsalva phenomenon, 512 safety concerns for, 510–514 strength-endurance continuum, 505–506 weight gain by, 515–517 weight loss and, 470, 517–518 Resting energy expenditure (REE), 413 aerobic exercise, 471 body composition affect on, 97–98 caffeine and, 97 Calories to maintain weight and, 444 defined, 96 energy sources for, 98 environmental factors influencing, 98 estimating, 97 exercise effect on, 105–106 genetic factors in, 97 resistance exercise training and, 470 smoking and, 97 very low-Calorie diets and, 97 Resting metabolic rate (RMR), 96 Resveratrol, 57 Retinol, 265–268 Retinol activity equivalents (RAE), 265 Retinol equivalents (RE), 265 Reversibility principle, 5 Riboflavin (vitamin B2), 276 deficiency, 276 DRI, 276 food sources, 45, 276 as key-nutrient, 45 major functions, 276

in muscle-cell energy process, 95 overview, 266–267 prudent recommendations, 276 supplementation, 276 Ribose, 152 Rickets, 270 Rippe, James, 3 Risk factors defined, 3 heart disease, 15 Roberts, William, 386 Rolls, Barbara, 455, 461 Rosenbloom, Christine, 18 RRR-alpha-tocopherol, 271 RRR-gamma-tocopherol, 271 Running, energy expenditure for, 104

S Saccharide, 118 Saccharin, 73, 154, 155 Salatrim, 171 Salt healthful dietary guidelines for, 51 limiting for weight loss, 465 reducing to control high blood pressure, 392–393 Salt tablets, 376–377 Salty sweating, 385 Saponins, 57 Sarcopenia, 519 Satiety center, 412 Saturated fat cholesterol-lowering recommendations, 197, 198 common foods high in, 169–170 healthful dietary guidelines for, 49–50 Saturated fatty acids defined, 169 dietary recommendations for, 173–174 Sawka, Michael, 367, 377 Scurvy, 284 Sears, Barry, 187–188, 452 Secondary amenorrhea, 320 Sedentary category, 106, 107, 445 Sedentary Death Syndrome (SeDS), 5 Selenium, 337–338 deficiency, 337 DRI, 337 food sources, 337 major functions, 337 overview of, 311, 326 prudent recommendations, 338 supplementation, 337–338 vegetarian diet and, 57 Selye, Hans, 508 Semivegetarians, 54 Serving size, 62 Set, 505 Set-point theory defined, 414 exercise effect on, 473 leptin, 414 Settling-point theory, 418 Shell temperature, 361 Shephard, Roy, 110 Short, Sarah, 17, 286 Simple carbohydrates, 118–119 Simplesse, 171 Singh, Anita, 288 Skinfold technique, 408–409 Skinner, James, 3 Skin wetting, to maintain water balance during exercise, 370–371 Slavin, Joanne, 157 Sleep, obesity and, 417 Smoking as heart disease risk factor, 15 resting energy expenditure, 97 risk factor for coronary heart disease, 192

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Snyder, Ann, 135 Soda loading, 547 Sodium deficiency, 358–359 DRI, 358 excess, 358–359 food sources, 358, 359 healthful dietary guidelines for, 51 hyponatremia, 375–376 major functions, 358 nutrition facts label terms for, 360 overview of, 311, 360 reading food labels and, 63 reducing to control high blood pressure, 392–393 salt tablets and exercising in heat, 376–377 Sodium bicarbonate, 544–547 ATP-PCr system, 546 defined, 544 lactic acid energy system, 545–546 oxygen energy system, 546–547 physical performance and, 544–547 safety of, 547 Sodium loading, 547 exercising in heat and, 381–382 Soft drinks as cause for obesity, 416 pancreatic cancer, 154 South Beach Diet, 455, 456 Soy protein, 51, 251 Specific heat, 365 Specificity principle, 5, 507 Sports and Cardiovascular Nutritionists (SCAN), 16 Sports anemia, 224, 329 Sports bars, 78, 121 Sports drinks, 78, 120 carbohydrate-electrolyte solution, 370 carbohydrate replacement of during exercise in heat, 373–375 comparison of content of various, 371 endurance performance and, 230 during exercise, 140 gastrointestinal distress, 373, 374 hyponatremia, 376 tooth decay, 153 Sports gels, 78, 120–121 Sports nutrition defined, 16 dietary habits of athletes, 17–18 ergogenic aids, 19–21 nutrition’s effect on athletic performance, 18–19 objectives of, 16 as profession, 16–17 Sports performance age and nutritional recommendations, 80 carbohydrate ingestion right before/during, 135–143 carbohydrate loading and, 148–150 commercial sports foods, 77–78 creatine and, 241–243 excessive weight loss and, 433–434 excess weight and, 432–433 food after competition, 77 food during competition, 77 food during training, 75–76 food prior to competition, 76–77 food while traveling for competition, 78–80 gender and nutritional recommendations, 80 genetic enhancement and, 3 genetics and, 3, 15 malnutrition and, 18 nutrient’s role in, 18 vegetarian diet, 59 Sports performance (See Athletic performance) Sports-related fitness defined, 15 nutrition and, 16–19

628

Index

Sports supplements defined, 20 effectiveness, safety and permissibility of, 554–555 effectiveness and safety of, 20–21 popularity of, 20 recommendations on use of, 78 unlisted ingredients, 20, 21 Spot reducing, 486 Spriet, Lawrence, 536 Starvation physical performance and, 433 protein as energy source during, 219 Steady-state threshold, 100 Steps to a Healthier You, 41, 42 Sterols, 201–202 Stewart, Ian, 322 Stimulus period of exercise, 477–478 Stomach, 122 fullness and appetite, 412 Stone, Michael, 501 Storage fat, 405 Strength-endurance continuum, 505–506 Stroke antioxidant supplements to prevent, 294–295 physical inactivity, 5 Structured physical activity, 5 Subclinical malnutrition, 264 Subcutaneous fat, 405 Sucralose, 119, 154, 155 Sucrose, 118 Sugar added sugar, 120 artificial sweeteners, 154–155 healthful dietary guidelines for, 51 less refined sugar for weight loss, 464 reading food labels and, 62, 63 refined effect on health, 153–154 cancer, 154 cholesterol-lowering recommendations and, 201–202 dental caries, 153 insulin resistance, heart disease and obesity, 153–154 pancreatic cancer, 154 tips for decreasing, 154 simple carbohydrates as, 118–119 Sugar substitutes, 119 Sulfites, 74 Sulforaphane, 57 Sundgot-Borgen, Jorunn, 430 Sunlight, vitamin D and, 269–270 Superhydration, 371 Supplements. See Dietary supplements; Sports supplements; Vitamin supplements Swain, David, 480 Sweat rate, 369 Sweat/sweating composition of sweat, 369 to dissipate body heat, 365 electrolytes and, 369, 375 excessive and electrolyte deficiency, 369 insensible perspiration, 353 loss of protein, 221 salty sweating, 385 sweat rate determination, 368–369 Swimming, energy expenditure for, 104 Synephrine, 544 Systolic pressure, 391

T Talk test, 480 Target heart rate range determining, 479–480 exercise intensity to achieve, 480–481 Taurine, 248

TEF. See Thermic effect of food (TEF) Television watching children and obesity, 419 increasing physical activity by decreasing, 469 Telford, Richard, 288 Temperature, body appetite and, 412 body’s regulation of, 362–363 core, 361 exercise’s effect on, 364–365 heat-balance equation, 362 heat dissipation during exercise, 365 hyperthermia, 363–364 hypothermia, 363 major factors influencing, 362 measuring, 361–362 normal body temperature, 361 shell, 361 Terpenes, 57 Testosterone, effectiveness, legality, safety of, 548–550 Thermic effect of food (TEF) aerobic exercise and, 471 Calories to maintain weight, 444 defined, 96 exercise effect on, 106 obesity and, 96 Thiamin (vitamin B1), 274–276 deficiency, 274 DRI, 274 food sources, 45, 274 as key-nutrient, 45 major functions, 274 in muscle-cell energy process, 95 overview, 266–267 prudent recommendations, 276 supplementation, 274–276 Thirst, to evaluate hydration status, 352, 356 Threshold stimulus, 478 Tipton, Kevin, 227, 502 Tocopherol, 266–267 Tolerable Upper Intake Level (UL), 39 Tonicity, 355 Tooth decay, refined sugar and, 153 Total cholesterol development of atherosclerosis, 194 guidelines for fasting blood levels of, 192–193 Total daily energy expenditure (TDEE), 96 Trabecular bone, 315 Trace minerals boron, 338–339 chromium, 334–337 copper, 332–333 defined, 325 fluoride, 340–341 iodine, 341 iron, 325–332 other, 340 selenium, 337–338 vanadium, 339 zinc, 333–334 Training basic principles of, 5 breakfast and, 75–76 chronic training effect, 75 endurance training effect on carbohydrate metabolism, 131 fat metabolism during exercise and, 182 food during, 75–76 high-carbohydrate diet for daily program, 144–145 protein metabolism and, 222–223 to reduce cholesterol levels, 202, 205 for sports performance, 15–16 Trans fatty acids cholesterol-lowering recommendations, 197–198 common foods high in, 169–170 defined, 169

dietary recommendations for, 173–174 healthful dietary guidelines for, 49–50 as stealth fat, 197–198 Triacylglycerol, 168 Triglycerides defined, 168–169 development of atherosclerosis, 194 guidelines for fasting blood levels of, 192–193 structure of, 168 Trisaccharides, 119 Tryptophan, 234 Tyrosine, 248

U Uncompensated heat stress, 365 Undernutrition, 18 Underwater weighing, 407–408 United States Olympic Training Center (USOTC), 16 Unstructured physical activity, 5 Urea, 217 Urine to evaluate hydration status, 356 loss of protein, 221

V Valine, 234 Valsalva phenomenon, 512 Valtin, Heinz, 352 Vanadium, 339 Variety in healthful diet, 36 healthful dietary guidelines for, 49 in MyPyramid, 41 Vegan, 53–54 Vegetables, 41 color of, and phytochemicals, 58 eat more, for weight loss, 465 healthful dietary guidelines for, 50 pesticide content of, 70 rising cost of, 36 Vegetarian diet, 53–59 athletic performance and, 59 becoming vegetarian, 58–59 benefits of, 56 calcium, 55 Calories, 55 daily food guidelines for, 54 fiber and, 56–57 iodine, 55 iron, 55 low Calorie, 57 low in fat and cholesterol, 56 minerals, 55 nutrient density, 56 nutritional concerns of, 55–56 phytochemicals in, 57–58 protein, 55–56 types of vegetarians, 53–54 vitamin B12, 55 vitamin D, 55 vitamin deficiencies, 55 vitamins in, 57–58 zinc, 55 Very active category, 107, 446 Very-low-Calorie diets health problems and, 427 recommendations for, 468–469 Vigorous exercise, 8 Villus, 122–123 Visceral fat, 405 Vitamins, 262–285. See also Vitamin supplements; specific vitamins deficiency, stages of, 264–265 defined, 262 essential, 266–267 as essential nutrient, 37 fat-soluble

Vitamin A, 265, 268 Vitamin D, 268–271 Vitamin E, 271–273 Vitamin K, 273–274 foods rich in, and preventing chronic diseases, 293–294 functions of antioxidant, 263 coenzyme, 263 energy, 264 hormone, 264 hypervitaminosis, 265 in muscle-cell energy process, 95 obtaining through diet not supplements, 291 overview of, 266–267 vegetarian diet and, 55, 57–58 water-soluble biotin, 281–282 choline, 282 major sites of activity, 275 niacin, 276–277 pantothenic acid, 281 riboflavin, 276 thiamine, 274–276 vitamin B6, 277–278 vitamin B12, 278–281 vitamin B-complex, 283 vitamin C, 283–285 Vitamin A, 265, 268 deficiency, 268 DRI, 265 food sources, 45, 265 hormonal function of, 263 as key-nutrient, 45 major functions, 265 overview of, 266–267 prudent recommendations, 268 supplementation, 268 Vitamin B1, 266–267, 274–276 Vitamin B2, 266–267, 276 Vitamin B6, 277–278 deficiency, 277–278 DRI, 277 food sources, 277 major functions, 277 overview, 266–267 prudent recommendations, 278 supplementation, 278 Vitamin B12, 278–281 deficiency, 279 DRI, 278 food sources, 278 major functions, 279 overview, 266–267 prudent recommendations, 279 supplementation, 279 vegetarian diet and, 55 Vitamin B-complex, 283 deficiency, 283 prudent recommendations, 283 supplementation, 283 Vitamin C, 283–285 absorption of iron and, 55 antioxidant role of, 286–288, 293, 294–297 deficiency, 284 disease prevention and, 294–297 DRI, 284 food sources, 45, 57, 284 as key-nutrient, 45 major functions, 284 overview, 266–267 prudent recommendations, 285 scurvy and, 38 supplementation, 284–285 vegetarian diet and, 57 Vitamin D, 268–271 deficiency, 270 DRI, 268–269 food sources, 269–270 hormonal function of, 263, 270 major functions, 270 overview of, 266–267

prudent recommendations, 271 sunlight and, 269–270 supplementation, 270–271 vegetarian diet and, 55 Vitamin D2, 268 Vitamin D3, 268 Vitamin E, 271–273 antioxidant role of, 286–288, 293, 294–297 deficiency, 272 disease prevention and, 294–297 DRI, 272 food sources of, 57, 272 major functions, 272 overview of, 266–267 prudent recommendations, 273 supplementation, 272–273 vegetarian diet and, 57 Vitamin K, 273–274 deficiency, 273 DRI, 273 food sources, 273 hormonal function of, 263 major functions, 273 overview of, 266–267 prudent recommendations, 274 supplementation, 273 Vitamin supplements, 286–299 biotin, 282 choline, 282 ergogenic aspects of antioxidant vitamins to prevent fatigue and muscle damage, 286–288 bee pollen, 289 bottom line for, 290 CoQ10, 289–290 multivitamin-mineral supplement for athletes, 288–289 quercetin, 290 reasons for athletes to take, 286 folate, 280 health aspects of determining adequate amount of, 297 disease prevention from, 294–297 guidelines for choosing, 297–299 megadoses, 292 obtaining vitamins through diet, 291 reasons vitamins recommended, 291–292 niacin, 277 pantothenic acid, 281 riboflavin, 276 thiamin, 274–276 vitamin A, 268 vitamin B6, 278 vitamin B12, 279 vitamin B-complex, 283 vitamin C, 284–285 vitamin D, 270–271 vitamin E, 272–273 vitamin K, 273 VLDL, 177, 178 Volek, Jeff, 244, 502 Volpe, Stella, 286 Volumetrics, 455, 461 VO2 max, 100 endurance training programs and, 131 Voy, Robert, 23

W Wagenmakers, Anton, 226 Waist circumference, 409 determining optimal body fat and, 410–411 Walberg-Rankin, Janet, 448 Walking aerobic, 482–483 energy expenditure for, 103–104 steps per day, 485 Wansink, Brian, 452

Warm-down phase of exercise, 476 Warm-up, 476 Water, 352–357. See also Body composition; Dehydration; Heat, exercise in after competition, 77 bottled, 353 carbohydrate loading and retention of, 148, 150 during competition, 77 as component of body composition, 406 daily need for, 352–353 ergogenic aspects of glycerol supplements, 382–383 oxygen water, 381 pre-cooling, 381 sodium loading, 381–382 as essential nutrient, 37 evaluating hydration status thirst, 352, 356 urine, 356 weight, 356, 368 exercising in heat and maintaining balance hyperhydration, 371 rehydration, 372 skin wetting, 370–371 feedback mechanism for regulation of, 355–356, 357 functions in body, 356 health benefits of drinking more, 356–357 hyponatremia, 375–376 intake/ouput overview, 352–353, 354 metabolic, 353 in muscle-cell energy process, 95 other substances in, 353 solid foods as source of, 353 stored in body, 353–355 extracellular, 354 intercellular, 354 intracellular, 354 intravascular, 354 thirst as guide for water balance, 352 water loss, 353 Water intoxication, 375–376 Water-soluble vitamins biotin, 281–282 choline, 282 guidelines for choosing supplements, 299 major sites of activity, 275 niacin, 276–277 pantothenic acid, 281 riboflavin, 276 thiamine, 274–276 vitamin B6, 277–278 vitamin B12, 278–281 vitamin B-complex, 283 vitamin C, 283–285 Watt, 87 WBGT Index, 363–364 Websites in MyPyramid, 42–43 for sound nutritional information, 24, 25 for starting exercise program, 10 Weight cholesterol-lowering recommendations, 196 determining amount of weight to lose, 447–448 to evaluate hydration status, 356, 369 excess weight and performance, 432–433 healthy body weight, 404 ideal body weight, 404 reducing to control high blood pressure, 392 regulation of, 411–419 body’s normal mechanisms of, 411–414 causes of obesity, 415–418 fat deposited in body, 414

importance of childhood obesity prevention, 419 settling-point theory, 418 Weight control/maintenance body’s normal mechanisms of energy expenditures, 412–413 energy intake, 412 feedback control, 413–414 set-point theory, 414 settling-point theory, 418 caffeine and, 541 dieting’s role in, 488–489 elements in good program for, 489–490 exercise’s role in, 469–472, 488–489 importance of prevention, 490–491 long-haul concept, 471 young athletes, 490 Weight cycling, 427 Weight gain basic considerations reasons for underweight, 500 steps for weight gain, 500 nutritional considerations, 501–505 balanced diet for, 503–505 Calories to form pound of muscle, 501 Calories to gain one pound/week, 501 dietary supplements for, 502–503 protein supplementation for, 501–502 resistance training benefits of, 518–519 contraindications, 518 effectiveness of programs, 516–517 example program for, 508–510 muscle hypertrophy and, 515–516 principles of, 506–508 purposes of, 505–506 safety concerns, 510–514 Weight lifting. See Resistance training Weight loss, 442–487 basic weight control, 443–448 amount of weight to lose, 447–448 caloric concept of weight control, 443–444 Calories in pound of fat, 443 Calories needed to maintain weight, 444–447 safe weight loss per week, 447 behavior modification, 448–452 applying to weight-control program, 449–452 defined, 449 importance of, 449 physical and social environmental factors, 449–450 short-term and long-term goals, 449, 450 suggested behavior changes, 450–451 calcium and, 317 dietary modifications, 452–469 balanced weight-loss diets, 457 counting Calories for, 456–458 determining calories in foods, 458–461 determining Calories to lose weight, 452–453 fiber and, 455 Food Exchange System, 458 general guidelines for selection/preparation of food, 461–466 glycemic index and, 455 high-protein weight-loss diets, 456–457 increased difficulty to lose after several weeks, 454 low-carbohydrate, high-fat weight-loss diets, 456

www.mhhe.com/williams9

629

low-fat, high-carbohydrate weight-loss diets, 455 major characteristics of sound diet, 454–457 occasional overeating, 469 overview of popular diets, 455 planning nutritionally balanced, low-Calorie diet, 467–468 portion sizes, 459, 462 predicting body-weight loss through diet alone, 453 very-low-Calorie diets, 468–469 weight loss in first week, 453–454 elements in good program for, 489–490 excessive eating disorders, 428–432 health problems, 425–428 impairment of physical performance, 433–434 exercise programs, 469–487 amount of exercise to lose weight, 484–485 appetite and, 472 appropriate level of intensity, 478–480

630

Index

designing own exercise program, 481–484 determining intensity to achieve target HR range, 480–481 exercise and not lose weight, 486–487 exercise most effective for losing body fat, 473–475 general design for weight reduction, 476 low-intensity exercise to burn more fat, 485–486 medical exam prior to starting, 475–476 part of body weight loss occurs in, 485 precautions before starting, 476 rapid weight loss during exercise, 487 role in weight loss/maintenance, 469–472 set point, 473 spot reducing, 486 stimulus period of exercise, 477–478

resistance training and, 470, 517–518 synephrine, 544 types of programs clinical program, 442, 443 do-it-yourself programs, 442–443 nonclinical programs, 442, 443 for young athletes, 490 Weight-loss dietary supplements, 425–426 Weight-loss drugs, 426–427 Weight Watchers, 455, 489 Whey protein, 228 resistance training, 230 Willett, Walter, 198 Williams, Clyde, 16, 142, 149, 183 Williams, Paul, 425 Wolfe, Robert, 226, 227, 502 Women alcohol and health risks, 529 calcium intake recommendations, 320–321 female athlete triad, 319–320 iron deficiency, 328 nutritional recommendations, 80 osteoporosis and, 315

resting energy expenditure and, 97 tolerating exercise in heat, 388 Wood, Peter, 475 Work defined, 86 measurement of, 87–88

X Xerophthalmia, 268

Z Zeaxanthin, 58 Zinc, 333–334 deficiency, 333–334 DRI, 333 food sources, 55, 333 major functions, 333 overview of, 311, 326 prudent recommendations, 334 supplementation, 334 vegetarian diet and, 55 Zone diet, 187–188, 230, 455, 456

1st 6 months 2nd 6 months

Lactating

46 55 58 63 65

45 66 72 79 77

13 20 28

6 9

(kg)

101 120 128 138 143

99 145 160 174 170

29 44 62

13 20

(lb)

157 163 164 163 160

157 176 177 176 173

90 112 132

60 71

(cm)

Height

62 64 65 64 63

62 69 70 70 68

35 44 52

24 28

(in)

1,310 1,370 1,350 1,380 1,280

1,440 1,760 1,780 1,800 1,530

740 950 1,130

320 500

REEa (kcal/day)

1.67 1.60 1.60 1.55 1.50

1.70 1.67 1.67 1.60 1.50

Multiples of REE

47 40 38 36 30

55 45 40 37 30

102 90 70

108 98

Per kg

Average energy allowance (kcal)b

+ 500 + 500

+0 + 300 + 300

2,200 2,200 2,200 2,200 1,900

2,500 3,000 2,900 2,900 2,300

1,300 1,800 2,000

650 850

Per dayc

b

REE is resting energy expenditure; see chapter 3 for explanation. Calculation is based on Food and Agriculture Organization equations, then rounded. In the range of light to moderate activity, the coefficient of variation is ± 20 percent. Thus, for an individual with an average energy allowance of 2,500 Calories per day, the typical range might be 2,000–3,000, which is plus or minus 500 Calories (0.20 × 2,500). See chapter 3 for an expanded discussion of energy requirement based upon physical activity levels. c Figure is rounded.

a

1st trimester 2nd trimester 3rd trimester

11–14 15–18 19–24 25–50 51+

Females

Pregnant

11–14 15–18 19–24 25–50 51+

1–3 4–6 7–10

Children

Males

0.0–0.5 0.5–1.0

Age (years) or condition

Infants

Category

Weight

Median Heights and Weights and Recommended Energy Intake

2,800 3,000

2,800 3,000

Pregnancy ⱕ18 y 19–50 y

Lactation ⱕ18 y 19–50 y 1,800 2,000

1,800 2,000

1,200 1,800 2,000 2,000

400 650

NDf ND

50 50

50 50

50 50 50 50

50 50

25 25

800 1,000

800 1,000

600 800 1,000 1,000

200 300

ND ND

ND ND

ND ND

ND ND ND ND

ND ND

ND ND

Vitamin C Vitamin D Vitamin E (mg/d) (␮g/d) (mg/d)c,d Vitamin K

ND ND

ND ND

ND ND ND ND

ND ND

ND ND

Thiamin

ND ND

ND ND

ND ND ND ND

ND ND

ND ND

Riboflavin

30 35

30 35

20 30 35 35

10 15

ND ND

Niacin (mg/d)d

80 100

80 100

60 80 100 100

30 40

ND ND

800 1,000

800 1,000

600 800 1,000 1,000

300 400

ND ND

Vitamin B6 Folate (mg/d) (␮g/d)d

ND ND

ND ND

ND ND ND ND

ND ND

ND ND

Vitamin B12

ND ND

ND ND

ND ND ND ND

ND ND

ND ND

Pantothenic Acid

ND ND

ND ND

ND ND ND ND

ND ND

ND ND

Biotin

3.0 3.5

3.0 3.5

2.0 3.0 3.5 3.5

1.0 1.0

ND ND

Choline (g/d)

ND ND

ND ND

ND ND ND ND

ND ND

ND ND

Carotenoidse

Copyright 2001 by the National Academy of Sciences. All rights reserved.

SOURCES: Dietary Reference Intakes for Calcium, Phosphorus, Magnesium, Vitamin D, and Fluoride (1997); Dietary Reference Intakes for Thiamin, Riboflavin, Niacin, Vitamin B6, Folate, Vitamin B12, Pantothenic Acid, Biotin, and Choline (1998); Dietary Reference Intakes for Vitamin C, Vitamin E, Selenium, and Carotenoids (2000); and Dietary Reference Intakes for Vitamin A, Vitamin K, Arsenic, Boron, Chromium, Copper, Iodine, Iron, Manganese, Molybdenum, Nickel, Silicon, Vanadium, and Zinc (2001). These reports may be accessed via www.nap.edu.

UL ⫽ The maximum level of daily nutrient intake that is likely to pose no risk of adverse effects. Unless otherwise specified, the UL represents total intake from food, water, and supplements. Due to lack of suitable data, ULs could not be established for vitamin K, thiamin, riboflavin, vitamin B12, pantothenic acid, biotin, or carotenoids. In the absence of ULs, extra caution may be warranted in consuming levels above recommended intakes. b As preformed vitamin A only. c As ␣-tocopherol; applies to any form of supplemental a-tocopherol. d The ULs for vitamin E, niacin, and folate apply to synthetic forms obtained from supplements, fortified foods, or a combination of the two. e ␤-Carotene supplements are advised only to serve as a provitamin A source for individuals at risk of vitamin A deficiency. f ND ⫽ Not determinable due to lack of data of adverse effects in this age group and concern with regard to lack of ability to handle excess amounts. Source of intake should be from food only to prevent high levels of intake.

a

1,700 2,800 3,000 3,000

600 900

Children 1–3 y 4–8 y

Males, Females 9–13 y 14–18 y 19–70 y ⬎70 y

600 600

Vitamin A (␮g/d)b

Infants 0–6 mo 7–12 mo

Life stage group

Food and Nutrition Board, Institute of Medicine, National Academies

Dietary Reference Intakes (DRIs): Tolerable Upper Intake Levels (ULa) , Vitamins