Boosting Your Energy: How to jump-start your natural energy and fight fatigue 9781614011262, 1614011265

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Boosting Your Energy: How to jump-start your natural energy and fight fatigue
 9781614011262, 1614011265

Table of contents :
What is energy?
Physical energy
Mental energy
What determines your energy level?
Energy and food
The basics
Vitamins, minerals, and energy
Are there energy-boosting foods?
Fatty acids and energy
Don’t forget fluids!
The jolt of stimulants
Do the “energy boosters” work?
Energy and exercise
How activity boosts energy
How lack of activity drains energy
The exercise prescription
Energy and sleep
How sleep boosts your energy
Getting the right amount of sleep
Energy and stress
Managing the stress response
Special bonus section: A 6-step plan to jump-start your natural energy
Fatigue: Energy's enemy
Changing views of fatigue
How common is fatigue
Two types of fatigue
Common causes of fatigue
Depression or anxiety
Sleep difficulties
Caring for a family member
Various diseases that cause fatigue
Chronic fatigue syndrome
Multiple sclerosis
Other neurological conditions
Other medical conditions
When to see a doctor

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Boosting Your Energy

How to jump-start your natural energy and fight fatigue

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Harvard Health Publications Harvard Medical School 10 Shattuck Street, 2nd Floor Boston, MA 02115-6011

Harvard Health Publications | Harvard Medical School | 10 Shattuck Street, Second Floor | Boston, MA 02115


Medical Editor Anthony L. Komaroff, MD Simcox-Clifford-Higby Professor of Medicine, Harvard Medical School Senior Physician, Brigham & Women’s Hospital, Boston

Executive Editor Anne Underwood Writer Nancy Monson Copy Editor Robin Netherton Creative Director Judi Crouse Production/Design Manager Lori Wendin Illustrators Scott Leighton, Michael Linkinhoker Published by Harvard Medical School Gregory D. Curfman, MD, Editor in Chief Urmila R. Parlikar, Senior Content Editor

Contents What is energy?. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Physical energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2 Mental and emotional energy . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 What determines your energy level?. . . . . . . . . . . . . . . . . . . . . . . 3

Energy and food . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 The basics. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Vitamins, minerals, and energy . . . . . . . . . . . . . . . . . . . . . . . . . . 8 Are there energy-boosting foods?. . . . . . . . . . . . . . . . . . . . . . . . . 9 The jolt of stimulants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

Energy and exercise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 How activity boosts energy . . . . . . . . . . . . . . . . . . . . . . . . . . . . 15 How lack of activity drains energy . . . . . . . . . . . . . . . . . . . . . . . 16 The exercise prescription . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16

Energy and sleep. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18 How sleep boosts your energy. . . . . . . . . . . . . . . . . . . . . . . . . . 18 Getting the right amount of sleep . . . . . . . . . . . . . . . . . . . . . . . 18

In association with

Energy and stress . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 20

Belvoir Media Group, LLC, 535 Connecticut Avenue, Norwalk, CT 06854-1713. Robert Englander, Chairman and CEO; Timothy H. Cole, Executive Vice President, Editorial Director; Philip L. Penny, Chief Operating Officer; Greg King, Executive Vice President, Marketing Director; Ron Goldberg, Chief Financial Officer; Tom Canfield, Vice President, Circulation.

Managing the stress response . . . . . . . . . . . . . . . . . . . . . . . . . 21

Copyright © 2016 by Harvard University. Permission is required to reproduce, in any manner, in whole, or in part, the material contained herein. Submit reprint requests to:

Fatigue: Energy’s enemy. . . . . . . . . . . . . . . . . . . . . . . . . . . 30

Harvard Health Publications Permissions 10 Shattuck St., 2nd Floor, Boston, MA 02115 Fax: 617-432-1506

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SPECIAL SECTION A 6-step plan to jump-start your natural energy. . . . . . . . . 23 Changing views of fatigue. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 30 Two types of fatigue . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 31 When to see a doctor. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 33

Common causes of fatigue. . . . . . . . . . . . . . . . . . . . . . . . . 35 Shift work . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Overwork. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Menopause. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Medications. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Caring for a family member. . . . . . . . . . . . . . . . . . . . . . . . . . . .

35 36 36 37 37

Diseases that cause fatigue. . . . . . . . . . . . . . . . . . . . . . . . 39 Depression or anxiety. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39 Sleep disorders. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 40 Chronic fatigue syndrome. . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42 Fibromyalgia. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 43 Multiple sclerosis. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45 Traumatic brain injury. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 46 Other medical conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48

ISBN 978-1-61401-126-2

Resources. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 51

The goal of materials provided by Harvard Health Publications is to interpret medical information for the general reader. This report is not intended as a substitute for personal medical advice, which should be obtained directly from a physician.

Glossary. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53 Cover Image: © Monkey Business Images | Thinkstock

Dear Reader, In many ways, energy is the elixir of life. With it, you feel ready to take on the world. Without it, you may have trouble just getting through the day. Energy is both physical and mental in scope—and lack of energy is a common complaint: in Gallup-Healthways surveys that asked one million Americans about their well-being, 14% said they did not have the energy they needed to get things done. Likewise, 10% of Americans surveyed for the National Sleep Foundation’s Sleep in America poll said they experienced so much daytime sleepiness that they were likely to nod off at inopportune times—such as during a meeting or while driving. Often a lack of energy or a feeling of fatigue is to be expected: for example, if you are recovering from the flu or failing to get enough sleep. Maybe you’re simply trying to do too much, and the resulting stress is wearing you down. Your exhaustion may be due to some of the physical changes that accompany aging, such as normal reductions in the amount of deep sleep or, for menopausal women, frequent hot flashes that disrupt sleep. While no one can turn back the clock, there are steps you can take to slow or even reverse some aspects of agerelated fatigue. In fact, we’ve created a whole Special Section in this report on ways to jumpstart your natural energy. In some cases, though, fatigue is not part of a normal process, but rather a sign of a chronic illness. For example, lack of energy is one of the main symptoms of depression, chronic fatigue syndrome, fibromyalgia and other pain syndromes, heart failure, multiple sclerosis, anemia, hypothyroidism, and diabetes, all of which require medical attention. Fatigue often subsides when these conditions are treated. Currently, fatigue cannot be measured scientifically. But advances in understanding the neurochemical processes involved with brain function are providing insights that could, one day, pave the way for new tests to measure fatigue and new medications to treat it. In the meantime, it’s important to know that while a lack of mental or physical energy can have many different causes, there are a number of lifestyle changes you can make that will help you regain the energy you need in order to fuel your life. Sincerely,

Anthony L. Komaroff, M.D. Medical Editor

Harvard Health Publications | Harvard Medical School | 10 Shattuck Street, Second Floor | Boston, MA 02115

What is energy?


he word “energy” can mean many things. On the most basic level, it is the power generated in our cells that enables our hearts to beat, our brains to think, and our muscles to move. All of us are producing energy constantly. You couldn’t function if you didn’t. You wouldn’t be able to breathe, get up out of your chair, or read this report. But that’s not what most people mean when they talk about energy. In an absolute sense, their bodies are producing energy, but they don’t have energy—that is, they don’t have enough physical and mental energy to do everything they want with ease. You might need energy in order to take on a physical challenge and keep it up for an extended period—working through a long day, for instance, or running a marathon, biking uphill, sightseeing on vacation, or doing yard work. Or you might just want to get through the day without feeling you’ve been flattened by a steamroller. Whatever your goal, you’ll be happy to know that there are a lot of lifestyle adjustments you can make that will help you pick up your game. We’ll discuss them in this report and also tackle some of the common causes of fatigue. But first it’s helpful to understand just what energy is and how it’s produced.

Physical energy

Though we tend to think of energy as a single phenomenon—you either have it or you don’t—there are both physical and mental components to energy. Physical energy has to do with the literal production of energy in cells. Like all machinery, muscles and brain cells must have fuel. This fuel comes from the oxygen you breathe and the food you eat. When it comes to food, certain nutrients provide raw power, and others help keep the machinery well oiled. You need an optimum mix of nutrients to keep the system functioning at its best (see “Energy and food,” page 8). The catch is that nutri2

Boosting Your Energy 

ents and oxygen cannot be turned directly into usable energy for the trillions of cells in your body. Each cell has one primary source of energy: a molecule called adenosine triphosphate, or ATP (see Figure 1, below). Your body stores only a small amount of ATP, but it makes more as quickly as it’s needed. When demand

Figure 1: How food and oxygen become energy 1. You breathe oxygen into your lungs.  The food you eat is broken down into separate nutrients in your stomach and intestine.

4. Mitochondria convert oxygen and nutrients to ATP, providing energy to cells.


2. Oxygen and nutrients travel through the bloodstream to your muscles.  

Muscle cell Red blood cells 3. Oxygen and nutrients are transported from the bloodstream into muscle cells.

The food you eat is digested and absorbed into the bloodstream, which delivers it to cells throughout the body. Oxygen from your lungs also travels to your cells, where tiny structures called mitochondria use it to convert the food nutrients into a chemical called adenosine triphosphate (ATP). ATP provides energy for everything from walking to thinking. w w w.h ealt h .ha r va r d.e du

increases—such as when you are exercising—your body must churn out more. To do this, it taps into glucose stored in muscles and the liver, as well as fats stored around the body. Your body’s ability to create ATP is crucial because it determines your capacity for physical exertion. And the reverse is also true: your physical conditioning influences how well you can generate ATP. Insufficient sleep also may reduce your capacity to make ATP. So you can see that diet, exercise, and sleep all play key roles in generating energy.

Mental and emotional energy

Energy is not just about muscles: it’s also about your mind and emotions. When you’re mentally energetic, you’re curious, you’re alert, you’re “on.” You readily absorb information by reading, listening, and watching. But mental energy is more complicated than physical energy. On one level, it’s about energy production in cells—specifically, brain cells. Like physical energy, it can be enhanced with optimum nutrition, exercise, sleep, and stress management. But physical and mental energy do not necessarily rise and fall in tandem. Sometimes, one rises as the other falls. That’s because the thing that we call “energy” is not simply a reflection of how much ATP your brain cells can generate. It also reflects your emotional state and how interested you are in something. You may have noticed that when you’re really absorbed in an activity—in a heightened state known as “flow”—you feel more energetic than when you are only half-interested in it. Passion and motivation can be powerful forces in creating mental energy. If you are mentally psyched to do something, typically you will feel physically energetic enough to do it. By contrast, if you’re bored, you’re likely to feel a lack of energy. This does not result from inadequate energy in brain cells, although we don’t know how to explain it.

What determines your energy level?

Some people, through a confluence of biology and personality, are born with vast amounts of energy. The ww w. h ealt h . h ar v ar d . e du

classic high-energy type is someone like former President Bill Clinton or craft maven Martha Stewart, both of whom have said that they need little sleep and are always ready for a social event or a new project (see “Do extroverts have more energy?” on page 7). But most people are not so lucky. A multitude of factors can affect your energy level, including the amount and type of stress you’re under, your sleep habits, your exercise routine, and your diet. Later chapters of this report will address all of these—and the Special Section will offer suggestions on improving them. The final chapter will discuss diseases that can sap your energy. In addition to lifestyle choices and illnesses, there are also basic biological factors that affect your energy. These include your genes, age, hormones, and circadian rhythms. Remember: just because the person sitting next to you at work (or sitting across the table from you at breakfast) has more mental or physical energy than you do, that doesn’t necessarily mean that there’s something wrong with you. It could simply mean that you are at the lower end of the normal energy spectrum (or that you’re not a “morning person” and your alertness rises later in the day).

Your genes There are probably many genes that play into your energy level. Scientists are only beginning to tease apart what they might be. But here’s one example: Whether you’re a night owl or an early riser, you need a certain number of hours of sleep in order to feel fully rested. However, this number can vary widely from one person to the next. Some people feel perky after just seven hours of sleep, while others are groggy if they log less than nine hours. The discovery of a genetic mutation in two people who need far less sleep than average may help explain at least some of this variation, although it’s not clear how many people carry this particular mutation. The mutation—in a gene called DEC2, which is known to affect circadian rhythms—was found in a mother and daughter who were naturally short sleepers, requiring just six hours a night instead of the average of eight. Most Americans only get about six hours of sleep a night and don’t feel that’s enough. As Boosting Your Energy


a result, they rely on alarms, caffeine, and power naps to awaken and stay awake during the day. By contrast, these two women awoke naturally after six hours and didn’t appear to suffer any negative effects from the short sleep cycle. To verify the power of this gene, scientists created genetically engineered mice with the same mutation. The mice not only slept less and stayed awake longer, they also needed less sleep to recover after the experimenters kept them from sleeping.

Your circadian rhythms If you’re like many people, you sometimes feel sleepy or drowsy for no apparent reason. Perhaps you feel like taking a nap in the middle of the day, or you have trouble concentrating when you watch a movie at night. If you haven’t used up your physical energy, why do you feel sleepy? No one feels alert and energetic all day. Instead, most people have times of day when they are at their best and other times when their energy slumps and alertness fades. Understanding your body’s natural daily biological rhythms (also called circadian rhythms) will help you match your activities with the times of day when you’re feeling most alert or energetic.

To a large extent, your level of alertness—or its opposite, sleepiness—is dictated by a cluster of cells deep within the brain. These cells—collectively known as the suprachiasmatic nucleus—are in the hypothalamus, the brain center that regulates alertness, appetite, body temperature, and other biological states. The suprachiasmatic nucleus acts as an internal “clock” that controls your circadian rhythms, including the rise and fall of hormones and other chemicals that influence whether you feel sleepy or wide awake. Like the other clocks in your life, your internal clock operates on a 24-hour schedule. According to this schedule, people typically feel most energetic in the morning until early afternoon, when their energy flags after lunch (see Figure 2, below). Many people get a second wind later in the afternoon or early evening, but their energy level dips again after the sun goes down, and it doesn’t rebound until the next morning. In short, the biological clock helps explain why people wake up in the morning and go to sleep at night—and why their energy levels fluctuate during the day. Most of us are “morning larks”: our energy levels rise and fall with the sun. Not everyone follows the

Figure 2: When are you at your best?

post-lunch dip



post-lunch dip

8 am 10 am 12 pm 2 pm 4 pm 6 pm 8 pm 10 pm

8 am 10 am 12 pm 2 pm 4 pm 6 pm 8 pm 10 pm

Time of day

Time of day

Scientists have measured several types of performance, including short-term memory and mental alertness, throughout the day. These skills usually peak in late morning. Lowest performance levels are usually in the late evening. The best-known daily decline in performance is in the early afternoon and is known as the “post-lunch dip.”


Boosting Your Energy 

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Ways to avoid jet lag There are two strategies to avoid feeling groggy when you fly. On a brief trip just one or two time zones away, you may be able to wake up, eat, and sleep on home time. Schedule appointments for times when you would be alert at home. On longer trips, to help you adjust to the new time zone, try the following:

Day 2

Day 1

9:30 p.m.

Day 3

9:00 p.m.

Day 4

Usual bedtime 10:00 p.m.

8:30 p.m.

Gradually switch before the trip. For several days before you leave, move mealtimes and bedtime incrementally closer to the schedule of your destination (see illustration). Even a partial switch may help. During the trip, drink plenty of fluids, but not caffeine or alcohol. Caffeine and alcohol promote dehydration, which worsens the physical symptoms of jet lag. They can also disturb sleep. Switch your bedtime as rapidly as possible upon arrival. Don’t turn in until it’s bedtime in the new time zone. Use the sun to help you readjust. If you need to wake up earlier in the new setting (you’ve flown west to east), get out in the early morning sun. If you need to wake up later (you’ve flown east to west), expose yourself to late afternoon sunlight.

Here’s one way to help reset your internal clock when you travel through time zones. If you’ll be traveling through several time zones, as when flying coast to coast, you can gradually adjust your sleep time. For example, three days before you plan to travel from the West Coast to the East Coast, go to bed half an hour earlier than usual, and get up half an hour earlier the next morning. The next night, go to bed an hour earlier than usual and get up an hour earlier. The day before you travel, make it 90 minutes. By the fourth day—the day of your trip— you’ll find it easier to adjust to your new time zone.

usual pattern, however. Some people are “night owls” who get a second wind in the evening and have trouble getting going early in the morning. Although it’s largely self-regulating, your internal clock responds to daylight as an important clue to external time. Nerve fibers connect the hypothalamus to the retina in the eye. In experiments, when people live for several days in a windowless laboratory and are exposed to light at intervals that are at odds with the outside world, their internal clocks reset themselves to match the new pattern of light and darkness. The influence of light on sleep/wake patterns probably explains why as many as 90% of blind people have problems sleeping. When the body has to adjust its internal clock because of daylight savings time, shift work, or travel to a different time zone (see “Ways to avoid jet lag,” ww w. h ealt h . h ar v ar d . e du

above), it disrupts more than just your sleep (and energy level). The internal clock is also in charge of regulating metabolism and cell division, which is why shift work has been associated with metabolic diseases such as diabetes.

Seasons and light Many people in the northern hemisphere find that they feel energized during spring and summer months when sunlight is abundant, and sluggish and depressed in winter. They may even suffer from seasonal affective disorder, or SAD, during the colder months. SAD typically comes on during the fall or winter and subsides in the spring. SAD affects about 1% to 2% of the population, particularly women and young people. Symptoms may include lethargy, loss of Boosting Your Energy


Levels of the sleep-inducing hormone melatonin begin climbing after dark and ebb after dawn, helping to regulate your sleep/wake cycle. But melatonin levels decline with age and virtually disappear by old age, leading to more insomnia and less restorative sleep.

interest in once-pleasurable activities, interpersonal problems, irritability, inability to concentrate, and a change in sleeping patterns and appetite. Experts don’t understand the causes of SAD, but three leading theories have emerged, placing the blame on an outof-sync body clock or on improper levels of either the neurotransmitter serotonin or the hormone melatonin (see “Hormones and brain chemicals,” below).

Hormones and brain chemicals One way that light influences your alertness is through melatonin, a hormone that induces drowsiness. Melatonin is produced in a predictable daily rhythm by the pineal gland, located in the middle of the brain, between the two hemispheres. Cells in the suprachiasmatic nucleus receive signals from the eyes about the amount of light in the environment and send signals to the pineal gland that influence the gland’s production of melatonin. Levels of melatonin begin climbing after dark, which encourages the body to sleep, and they ebb after dawn, which encourages the body to awaken. Scientists think that the daily light-sensitive cycles of melatonin help keep the sleep/wake cycle on track. Melatonin is widely available in supplement form as a sleep aid and is often recommended for people with insomnia or jet lag, as well as for shift workers. However, some melatonin supplements contain animal brain and nerve tissue, which carries a risk of 6

Boosting Your Energy 

Your body weight There are well-established connections between obesity and fatigue: in one Swiss sample of 220 obese people, 59% reported fatigue. The heavier you are, the less active you tend to be, and the more tired you feel. You use much of your energy in moving your body to accomplish normal activities of daily living and metabolic processes, leaving little left over for other pursuits. Links have also been noted between obesity and sleep disturbances—including daytime sleepiness and sleep apnea (episodes of not breathing during sleep)— and between sedentary behavior and obesity. The more time you spend sitting (at work, using the computer, driving cars, watching television at home, etc.), the less energetic you feel. In this vicious circle, sedentary behavior begets more sedentary behavior. By contrast, physical activity begets more physical activity.

Your age It’s a nearly universal lament of people over age 35: you don’t have as much energy as you did when you were w w w.h ealt h .ha r va r d.e du

© Ridofranz | Thinkstock

contamination with such infectious diseases as mad cow disease and Creutzfeldt-Jakob disease. Melatonin supplements made synthetically in a lab do not carry the same risk. But because these supplements are not government-regulated, and labels are not required to reveal this information, you can’t be sure of the source of the melatonin you are taking. In addition to melatonin, other chemicals in the body influence our state of alertness. Several neurotransmitters (chemical messengers) play a role in arousal. Norepinephrine, epinephrine (often called adrenaline), and dopamine stimulate wakefulness. Adenosine and gamma-aminobutyric acid (GABA) are believed to promote sleep. Individuals differ in their natural levels of neurotransmitters and in their sensitivity to these chemicals. The female menstrual cycle and fluctuations in the levels of the sex hormones estrogen and progesterone can also alter energy levels. Many reproductive-age women suffer from premenstrual syndrome (PMS), which causes them to feel tired, irritable, and sad before their periods.

Do extroverts have more energy? Extroverts like Richard Branson of the Virgin Group or Howard Schultz of Starbucks often seem to have more energy than introverts, and emerging evidence supports the idea that personality traits may influence energy levels. For example, a Dutch study of 765 people who worked at least 20 hours a week found that subjects who had low scores for extroversion and high scores for autonomy experienced more fatigue than other subjects. It’s not clear, however, how strong a role extroversion plays in boosting energy. Research shows that introverts who talk more and act assertive have just as much energy as extroverts do. Thus, it may be that just acting like an extrovert can affect your energy level.

younger. One of the most common complaints is that you can’t stay up as late and still function normally the next day. In part, that reflects lifestyle changes; you may be putting in too many hours at work, or you may be caring for children, older relatives, or both. But aging also brings physical changes that can contribute to a lack of energy. Although increased fatigue is not inevitable with increased age, certain age-related factors can promote fatigue by influencing your sleep cycles directly. For one thing, your circadian cycle advances, making you want to fall asleep earlier at night and wake up earlier in the morning. Insomnia also becomes more common as people get older. In part, that may be because melatonin levels decline with age and virtually disappear by old age. Since melatonin helps you feel sleepy at night, its decline can make it harder to fall asleep. In women, the onset of menopause can bring hot flashes, which can interrupt sleep and even lead to chronic insomnia. People also notice that they’re not as strong as they used to be or that they can’t move as quickly as they age. In both men and women, muscle mass declines steadily over the years. By age 70, you’ve lost

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30% of the muscle mass you had at age 20. A drop in muscle mass means a decrease in strength and an increase in fatigue. As muscles shrink, they become fatigued more rapidly. With age, your ligaments and joints also become stiffer, so you move more slowly. To a large extent, you can compensate for these changes by exercising regularly to maintain strength and flexibility. Weight training increases muscle strength, and stretching increases flexibility. Along with a decline in physical energy, many people find that their mental energy falls somewhat as they age. They have a harder time concentrating and remembering things, and it takes longer to learn new information. In part, these difficulties reflect agerelated chemical changes in the brain that affect memory and learning. On the bright side, staying active mentally by reading and learning new mental skills, such as languages, games, and music, can help offset this age-related decline.

Your health Illnesses—including many that become more common with age—can deplete your energy as well (see “Diseases that cause fatigue,” page 39). Many illnesses can interfere with sleep. For example, people with heart failure may awaken feeling short of breath because body fluids accumulate in the lungs while they’re lying down. People with heartburn often find that their discomfort is greatest when they lie down and stomach acids back up into the esophagus. And hundreds of prescription and over-the-counter drugs can cause daytime drowsiness or fatigue (see “Medications,” page 37). Fatigue is also a common symptom of a wide range of diseases, including anemia, kidney disease, multiple sclerosis, diabetes, and cancer. In some cases, such as in cancer, fatigue may be the earliest sign that something is wrong. If you suddenly feel listless, it’s worth visiting your doctor to make sure nothing serious is going on. 

Boosting Your Energy


Energy and food


nesium, potassium, and dietary fiber—all of which are underconsumed in the typical American diet and all of which directly or indirectly affect your energy level. Similarly, whole grains are an excellent source of B vitamins, iron, and magnesium, which play a role in energy production (see The basics “Vitamins, minerals, and energy,” Much of the food you eat is conbelow). If nothing else, such a diet, verted into glucose (sugar) and which is also recommended for a fat, which provide the essential healthy heart, just makes you feel fuel for energy production. The better. That alone can boost your equation is not as straightforenergy. ward as it seems, however. Unfortunately, changes in The energy potential of food the food industry over the past is measured in calories. But con70 years have led to the developsuming more calories than you ment of highly processed, chemineed won’t give you extra energy. It’s important to pay attention not only to cally enhanced, and nutritionally In fact, it can have the oppo- total calories, but also to the types of foods that supply those calories. deficient products (think food in site effect. Excess calories are boxes). These products—including stored as excess pounds, and the heavier you are, the more effort you’ll need to expend cookies, chips, and most breakfast cereals—are often in walking, pumping blood, and so forth. The more hard to resist, but they contain empty calories that effort you exert, the more energy you need to burn— leave you hungry and tired rather than giving you the nutrients and energy you need to feel your best. and the more fatigued you’ll inevitably feel. It’s important to pay attention not only to total calories, but also to the source of those calories. To provide your body with the optimum fuel, you need Vitamins, minerals, and energy adequate amounts of specific vitamins and minerals, Energy production depends on certain vitamins and as well as a mix of unrefined or minimally refined minerals. Deficiencies in these can contribute to carbohydrates (vegetables, fruits, and whole grains), flagging energy levels, so it’s important to consume proteins (lean meats, poultry, seafood, eggs, beans and enough. However, be aware that if your levels of these peas, soy products, nuts, seeds, and dairy products), nutrients are normal, taking more will not help. and healthy fats (such as olive oil, canola oil, and avoIron. A low level of iron is the most common cause cados). You also need plenty of fluids. of anemia, a shortage of red blood cells (see “Anemia,” Such a diet emphasizes unprocessed or minimally page 48). A deficiency of this vital mineral prevents processed foods for a very good reason. Vegetables the bone marrow from making enough hemoglobin, and fruits contain vitamins A, C, and K, folate, mag- the oxygen-carrying part of red blood cells. Thus, 8

Boosting Your Energy 

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© Cathy Yeulet | Thinkstock

ike the car you rely on to get to work, your body carries its own supply of fuel, and you can replenish it as needed. The food you eat is the stuff of which this energy is made.

anemia impairs the delivery of oxygen to the body’s tissues. Because oxygen is needed to create ATP, doctors assume that the fatigue many people with anemia experience comes from the reduced production of ATP in their cells. Anemia is most common in menstruating women, who lose blood (and, hence, iron) with every period. When this blood loss causes iron-deficiency anemia, iron-rich foods (such as liver, red meat, eggs, rice, and beans) and iron supplements can help restore the body’s iron levels and correct the anemia. If you don’t suffer from an iron deficiency, however, there’s no evidence that taking iron supplements will boost your energy. Indeed, this practice can lead to iron overload, which, in some people, can damage multiple organs in the body, including the liver and heart. This in itself can lead to fatigue as well as a host of serious health problems. Vitamin B12 and folic acid. A deficiency in either of these B vitamins can also cause anemia. Because many packaged foods, including breads and flour, are fortified with folic acid, most people get plenty of that nutrient. However, about 6% of people ages 60 and older are deficient in vitamin B12, in part because it becomes harder with age to absorb enough of the vitamin from foods, such as meat and dairy products. Vitamin B12 deficiency can also be a problem for vegetarians—particularly vegans, who consume no animal or dairy products, the main dietary sources of vitamin B12. Even if your diet contains adequate amounts of vitamin B12 and folic acid, illnesses such as inflammatory bowel disease can interfere with their absorption. Likewise, it has recently been found that people with type 2 diabetes who take the drug metformin for many years may have low vitamin B12 levels. Some people take vitamin B12 shots for energy, but again, this probably won’t increase your energy unless you are B12 deficient. Magnesium. Magnesium helps break down glucose into energy, and low intakes are associated with type 2 diabetes, metabolic syndrome, high blood pressure, osteoporosis, migraine headaches, asthma, and colon cancer. A study by the Center for Magnesium Education and Research suggests that 48% of the U.S. ww w. h ealt h . h ar v ar d . e du

population consumes less than the required amount of magnesium from food (320 mg for women and 420 mg for men). Vitamin D. The most talked-about vitamin in recent years has been vitamin D, which is manufactured in the skin from sunlight. It is also found in some types of fish (such as tuna, salmon, mackerel, and herring) and fortified products such as milk, soy beverages, orange juice, and breakfast cereals. Observational studies suggest that people with high blood levels of vitamin D have lower risks for cancer, heart disease, and diabetes. Vitamin D deficiency, on the other hand, can lessen bone and muscle strength, making you feel weak, which can ultimately impair your ability to perform everyday tasks. Low levels of vitamin D can also depress your mood, another energy sapper. In 2011, the Institute of Medicine (a part of the National Academies of Science, Engineering, and Medicine) increased the Recommended Dietary Allowance (RDA) for vitamin D to 600 international units (IU) per day for adults up to age 70 and to 800 IU per day for those ages 71 or older. Some doctors recommend higher doses, around 1,000 to 2,000 IU per day. The health benefits of such doses are not yet proven, but are being studied. Do not exceed the upper level of 4,000 IU per day. Vitamin and mineral deficiencies are easy to diagnose and, for most people, simple to remedy with supplements. Older people who are deficient in vitamin D should take vitamin D3, which is absorbed more easily than other forms of vitamin D.

Are there energy-boosting foods?

Given that food is fuel, it’s only natural to wonder if certain types of food deliver energy more efficiently than others. Beyond the importance of eating a healthy diet that includes plenty of fruits and vegetables, whole grains, and healthful sources of fat and protein, there’s relatively little scientific information about the effects of specific foods on energy levels (see “Do energy bars pack an extra punch?” on page 14). However, certain foods can give you more energy under specific circumstances. Boosting Your Energy


Carbohydrates and energy Because muscles burn carbohydrates first, tests of physical endurance require a steady supply. Therefore, many people view sugar as an “energy food.” That’s misleading. Sugar is a simple carbohydrate, which means that it’s digested and absorbed into the blood quickly. When you eat a candy bar or some other sugary food, your blood sugar shoots up. You feel more alert and physically energized. But the effect is shortlived, lasting only about half an hour, because your pancreas responds by flooding your bloodstream with large amounts of insulin, the hormone that drives

sugar (glucose) from your blood and into your cells. This rapidly lowers your blood sugar. Afterward, you may actually feel less energetic than you did before eating the sweet snack, so it’s best to avoid sugary foods, despite the temporary lift they give you. To keep your blood sugar and energy levels on an even keel over the long haul, pick your carbohydrates wisely. Try to avoid highly refined carbohydrates and focus instead on complex carbohydrates, such as highfiber whole-grain bread, brown rice, whole-grain pasta, and most vegetables. These take longer to break down, so your blood sugar levels rise and fall more

Table 1: Glycemic load of popular foods, from worst to best Glycemic load is a measure of how much a particular food will raise your blood sugar in the short term. It takes into account both the amount of sugar in the food and the food’s glycemic index (how quickly that sugar is absorbed into your bloodstream). Eating foods with a low glycemic load may help you keep your energy on a more even keel. FOODS



High glycemic load




Low glycemic load


2 six-inch


Ice cream

½ cup


Dates, dried

2 ounces


All-Bran cereal

½ cup



1 cup



4 ounces


Macaroni and cheese

6 ounces


Baked beans

1 cup



2 ounces



4 ounces


Potato, baked

5 ounces


Pumpernickel bread

1 slice



12 ounces



4 ounces


White rice

5 ounces



4 ounces


Raisin Bran cereal

1 cup



4 ounces



1 cup


Green peas

3 ounces



3 ounces



4 ounces


Hummus (chickpea dip)

1 ounce


Medium glycemic load Brown rice

5 ounces


Whole-grain pasta

6 ounces


Oatmeal (rolled oats)

1 cup



1 medium


Orange juice

1 cup


Potato chips

50 grams


While it’s useful to know the glycemic load of a particular food, this shouldn’t be your only criterion for including a food in your diet or avoiding that particular item. For example, as shown in the table above, ice cream has a low glycemic load—but it also has a lot of saturated fat, which is not healthy if taken in large amounts.

Adapted from Foster-Powell K et al. “International tables of glycemic index and glycemic load values: 2002,” American Journal of Clinical Nutrition (July 2002), Vol. 62, pp. 5–56. The article includes a list of the glycemic index and glycemic load for 750 foods.


Boosting Your Energy 

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gradually (see Table 1, page 10). They also contain more vitamins and minerals than refined carbs.

Protein and energy You need protein to maintain your muscles, bones, skin, and every other organ and tissue in your body. Protein has many functions, including building the enzymes that trigger many of the body’s important chemical reactions. A lack of protein in the diet can slow growth, reduce muscle mass, lower immunity, and weaken the heart and respiratory system. A weaker heart and respiratory system make it harder to do physical work and force us to use more energy doing it. Protein deficiency is rare in the United States. In fact, most Americans tend to overestimate how much protein they really need. The recommended intake for protein is 10% to 35% of your total calories, depending on your energy needs. However, recent research suggests that older adults may benefit from a somewhat higher protein intake, especially when combined with regular strength training and aerobic exercise, in order to maintain muscle mass and strength as well as prevent disability. The paradox is that many older adults eat less food over all and therefore may be deficient in protein. Protein consumption should be spread out over the day’s meals. The best sources include lean meats, poultry, seafood, low-fat dairy products, beans and peas, soy products, nuts and seeds, and eggs.

Fats and energy Fats—technically known as fatty acids—also provide energy, but certain types appear to be better than others at getting you through your day. Foods that are loaded with saturated fat (say, a cheeseburger and fries) are not only unhealthy, leading to clogged arteries, but also have a fairly immediate soporific effect. One small study of 31 healthy, normal-weight people showed that higher saturated fat consumption caused more daytime sleepiness. Another found that when people eat more saturated fat and less fiber, they don’t sleep as deeply at night or get as many restorative benefits from sleep. By contrast, scientists have learned that essential fatty acids, which are highly concentrated in the brain, ww w. h ealt h . h ar v ar d . e du

support cognitive performance, providing at least an indirect energy boost. Essential fatty acids include the omega-3 fatty acids (found in fish, flaxseeds, soybeans, walnuts, and canola oil). They are called “essential” because your body cannot manufacture them from other nutrients; they must be acquired through food or supplements. Researchers are learning more about the role omega-3s and other fatty acids play in the brain. Numerous studies have linked low intake of omega-3 fatty acids to a host of cognitive and behavioral problems, including depression, memory problems, poor mood, Alzheimer’s disease, and attention deficit hyperactivity disorder. Deficiency can also hamper the renewal of neural membranes, thus making the brain age faster. One study that used brain imaging techniques to examine eight people with chronic fatigue syndrome found reduced levels of essential fatty acids in the brain. While more research is needed to know whether consuming more omega-3 fatty acids would alleviate chronic fatigue—much less help people with run-of-the-mill energy concerns—it certainly can’t hurt to ensure that you’re getting adequate amounts in your diet.

Don’t forget fluids!

Water is the main component of blood and is essential for carrying nutrients to cells and taking away waste products. If you are short on fluids, one of the first signs is a feeling of fatigue and weakness. Approximately 50% to 60% of your body weight is water, and you are constantly losing water through urine, sweat, and breathing. This water needs to be replenished. Consuming a sufficient amount of fluids in beverages and water-filled food (such as fruits, vegetables, and soup) will help you maintain your energy.

The jolt of stimulants

Certain substances in food give you an energy boost because they contain stimulants that speed up the chemical reactions inside cells. Caffeine, the bestknown stimulant, occurs naturally in coffee, tea, cocoa, and chocolate. It is also added to some soft Boosting Your Energy


drinks and energy drinks and used as an ingredient in some medications. Caffeine has many effects. When you consume a food or drink that contains caffeine, your brain cells fire messages more quickly, improving concentration and reaction time. The heart pumps blood faster and more forcefully, increasing your physical energy. Some people are more sensitive than others to caffeine. For them, a cup of coffee or a can of cola is all it takes to have some or all of the stimulating effects. But people who consume caffeine on a regular basis often develop a tolerance for it, which means that they need to increase their intake to get the same effect. In addition, people can become so dependent on caffeine stimulation that they feel tired and sluggish when the level of caffeine in their blood drops. Nicotine in tobacco is also a stimulant, but because of the detrimental effects of smoking, it should not be used as an energy booster. Indeed, smoking can cause insomnia, which can then lead to daytime sleepiness and fatigue.

Do “energy boosters” work?

Go to the store, and you’ll see a multitude of herbs and other supplements that claim to boost energy. Some are even added to soft drinks and other foods for this purpose. However, there is little or no scientific evidence to support the claims for most of these substances. The fact is, the only pill that’ll reliably boost your energy is one containing a stimulant, such as caffeine—and the effects of these stimulants wear off within hours. The same holds true for drinks touted as energy boosters. Most contain as much caffeine as a cup of coffee, and lots of sugar (see “Energy drinks: Popular but problematic,” page 13). Here’s a look at some of the other substances that are commonly touted as energy boosters. Chromium picolinate. This trace mineral is widely marketed to build muscle, burn fat, and increase energy and athletic performance, but research has not supported these claims. Coenzyme Q10. This enzyme is found in mitochondria, the energy factories of our cells. Supplements have been shown to improve exercise capacity 12

Boosting Your Energy 

in people with heart disease and may do the same in people with rare diseases that affect the mitochondria. In other cases, the effects are not clear. One small European study suggested that people with chronic fatigue syndrome might benefit from supplementation with coenzyme Q10, but more research is needed. Creatine. Another compound produced by the body, creatine is largely found in muscle. It is widely sold as a supplement. Taken as a supplement, there is evidence that it can build muscle mass and improve performance in sports requiring short bursts of muscle activity (like sprinting). Small studies suggest that creatine supplements combined with resistance training can improve muscle mass and strength in older adults. However, there is little evidence that it can reduce a feeling of fatigue in anyone. While no adverse effects of taking creatine in the doses recommended on the bottle (typically 2 to 3 grams per day) have been established, there are too few studies of sufficient size and duration to allow confidence about the lack of adverse effects. DHEA. Sometimes marketed as a “fountain of youth,” this naturally occurring hormone is said to boost energy as well as prevent cancer, heart disease, and infectious diseases, among other things. The truth is that supplemental DHEA has no proven benefits and some potentially serious health risks. Some research shows that DHEA can damage the liver. It can also lower levels of heart-healthy HDL cholesterol. And because this hormone is related to estrogen and testosterone, there is concern that it may increase the risk for breast and prostate cancers. By increasing levels of testosterone, it can also encourage acne and facial hair growth in women. Until further research clarifies the side effects, it’s wise to avoid taking DHEA. Ephedra. Although this product in supplement (pill) form was banned by the FDA in 2004 because of major safety concerns, including increased risk of heart attack and stroke, it remains available for sale on the Internet. Any effectiveness ephedra may have in terms of boosting energy probably results from two substances it contains—ephedrine and pseudoephedrine—which may increase alertness. There is no completely safe amount of ephedra you can consume w w w.h ealt h .ha r va r d.e du

Energy drinks: Popular but problematic

© Mauro Matacchione | Thinkstock


ooking for energy from a bottle? You’re not alone. Energy drinks and shots—including Amp, 5-Hour Energy, Monster Energy, Red Bull, and Rockstar—have become the fastestgrowing category in the beverage industry. They’re consumed both to boost flagging energy levels and to help with weight loss. Most popular among teenagers and young adults, these products are booming at $12.5 billion a year, according to the market research firm Packaged Facts. But there’s really no magic formula here. What gives these drinks their jolt is good old-fashioned caffeine. Consumer Reports tested 27 energy drinks and found that the amount of caffeine ranged from 6 to 242 milligrams (mg) per serving—and there is more than one serving in some cans and bottles. As a point of comparison, coffee has roughly 100 mg of caffeine in a 5- to 8-ounce cup, while 12 ounces of CocaCola has 50 mg. Most of the drinks also contain lots of sugar, which along with the caffeine can lead to a jolt of energy and then a crash (just like the sugar in a candy bar). Energy drinks also contain a mix of herbs and other substances that are marketed as “energy boosters,” but they haven’t actually been proven to increase energy unless the drinks also contain caffeine. But the bigger concern is that some people, particularly young adults, may consume too many of these drinks. When they do, all that caffeine, a diuretic, can contribute to dehydration and other problems. Since 2004, the FDA has received reports of 34 deaths and 56 episodes of adverse reactions—such as blood pressure elevations, convulsions, and heart rhythm abnormalities, most leading to hospitalizations—linked to energy drinks. Emergency room visits related to ingestion of energy drinks have also increased, from 1,494 in 2005 to 20,783 in 2011, the most recent year for which statistics are available. Most of these visits involved people ages 18 to 39, but the largest increase was seen among people 40 or older—perhaps because of caffeine intolerance,

orally. (Some cold remedies also contain ephedrine or pseudoephedrine, but it’s best to use these for no more than a few days. Prescription nasal sprays containing these substances are safer than pills, but should also be used for just a few days as prescribed.) If you want to boost your energy by stimulating your central nervous system, a cup of coffee or another caffeinated beverage will work just as well. Ginkgo biloba. Derived from the maidenhair tree, ginkgo biloba has been used for centuries in Chinese medicine and is now a common dietary ww w. h ealt h . h ar v ar d . e du

Energy drinks are hugely popular for boosting flagging energy, but what gives them their jolt is usually good old-fashioned caffeine and sugar. You’re better off with a cup of coffee. use of prescription drugs that interacted with the drink’s ingredients, or existing medical conditions. Public health experts have also raised alarms about the practice of mixing energy drinks with alcohol, prompting the FDA to warn manufacturers that caffeine is an “unsafe additive” to an alcoholic beverage. The stimulant effect of the energy drinks can counteract the soporific effect of the alcohol, enabling a person to drink longer. In addition, the caffeine can mask a person’s level of intoxication, the FDA said, and many people may erroneously think the energy drink will sober them up and make it safe for them to drive. The bottom line: If you need a quick surge of energy, it is okay to consume an occasional energy drink—no more than one a day—but this shouldn’t be a daily or long-term practice. If you’re dragging, it’s far better to drink a single cup of coffee or tea, or better yet, create energy through proven nutritional, exercise, and lifestyle strategies. (The Special Section, “A 6-step plan to jump-start your natural energy,” starting on page 23, contains a well-rounded program.)

supplement in Western countries. Its effects on cognition (thinking), mood, alertness, and memory have been the subject of many studies, but those studies have not generally been of high quality, so it is hard to draw conclusions about how effective it really is. A Cochrane Collaboration review found the evidence was too weak to conclude that ginkgo biloba improved cognition in people with Alzheimer’s disease. Regarding memory in people without dementia, the evidence is conflicting. Other studies suggest ginkgo biloba may improve some aspects of mood, including alertness Boosting Your Energy


Do energy bars pack an extra punch?


t’s impossible to walk into a drugstore or supermarket without seeing shelves lined with “power bars” that supposedly boost your energy. The manufacturers of such products claim that they’re superior to candy bars because they contain an “ideal ratio” of simple to complex carbohydrates, along with protein and fat. However, there’s no proof that such an ideal ratio exists.

A lack of scientific evidence doesn’t mean these products aren’t popular, however. An online survey of 2,355 adults found that 33% of those surveyed were consuming energy bars and other highly fortified food and supplement products. Those who purchased them most often were men, African Americans, Hispanics, more highly educated people, and those under age 45.

In fact, only a few studies of these bars have been conducted. One from Ohio State University compared the glycemic index of typical energy bars with other sources of carbohydrates. The power bars were no better than a candy bar at providing sustained energy. Another, a military study conducted in Finland, found that high-protein bars were no more effective than standard field rations in preventing an energy deficit during an eight-day training exercise, although they did appear to boost mood and satiety.

If you like the convenience of a power bar or energy bar as a snack, limit your intake to just one per day and look for a bar with the fewest and most natural ingredients (whole grains, nuts, and dried fruit) and the lowest calories (less than 200). Read the label. Ideally, bars will have more than 3 grams of protein and fiber, less than 20 grams of sugar, no hydrogenated oils or trans fats, and no high-fructose corn syrup. Or grab a bag of homemade trail mix—nuts, seeds, and dried fruits—instead.

and calmness, in healthy subjects. By making you more alert and calm, it may increase your sense of energy. Ginseng. This is a relatively safe and popular herb, said to reduce fatigue and enhance stamina and endurance. It is sometimes called an “adaptogen,” meaning it helps the body cope with mental and physical stress and can boost energy without causing a crash the way sugar does. Data from human studies are sparse and conflicting. Some studies report that ginseng improves mood, energy, and physical and intellectual performance. Other research concludes it doesn’t improve oxygen use or aerobic performance, or influence how quickly you bounce back after exercising.


Boosting Your Energy 

Guarana. This herb induces a feeling of energy

because it’s a natural source of caffeine—in fact, it appears to be even more stimulating than caffeine. But consuming a lot of guarana, especially if you also drink coffee and other caffeinated beverages, could ultimately lower your energy level by interfering with sleep. Vitamin B12 . Some doctors give injections of vitamin B12 as energy boosters. But unless they are given to correct anemia that results from a true deficiency of the vitamin, there is little evidence that vitamin B12 treatments boost energy (see “Vitamin B12 and folic acid,” page 9). 

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Energy and exercise


energy. When you work out, your body releases epinephrine and norepinephrine. In large amounts, these stress hormones cause the energy-draining fight-orflight response, but in the modest amounts induced by exercise, they make you feel energized (see “Energy and stress,” page 20). Exercise also boosts levels of compounds called endorphins, “feel-good” chemicals that lift your mood and are often credited for the “runner’s high.” An elevated mood in itself can be an energy booster. Finally, regular aerobic exercise almost guarantees How activity boosts energy There are at least four distinct ways that exercise that you will sleep more soundly—a prerequisite for feeling refreshed. Exercise is the only proven way to makes you feel more energetic. For starters, when you engage your muscles in any increase the amount of time you spend in deep sleep, type of exercise, more energy-producing mitochon- the type that particularly restores your energy (see dria form in your muscle cells. Mitochondria are the “How sleep boosts your energy,” page 18). The more cellular powerhouses that convert glucose and fat into deep sleep you get, the less likely you are to awaken ATP, the molecule that cells use for energy. So while in the middle of the night, and the more rested you’ll exercise burns energy, it also enables muscle cells to feel the next day. Exercise also increases the amount of time you spend in REM (rapid produce more energy. eye movement) sleep, the time Second, exercise increases during sleep when you dream your body’s oxygen-carrying most often and most vividly. capacity. Oxygen, along with gluMore time in REM sleep also cose and fat, is essential to fueling restores your sense of energy, cells, which need oxygen both to though not as much as deep sleep. create ATP and to liberate energy How exercise improves both stored as ATP. An increase in REM and deep sleep is unknown, oxygen therefore gives you more although scientists suspect that it stamina. Any type of regular leads to the production of chemiexercise creates more capillaries, cals that affect alertness. the tiny blood vessels that ferry In a poll conducted for the oxygen to your cells. But aerobic National Sleep Foundation, peoexercise, by making you breathe ple who exercised vigorously on the most deeply and increasing a regular basis reported sleepyour heart rate the most, gets ing better than more sedentary more oxygen circulating. people, even though both groups Third, exercise affects levels Regular exercise boosts your energy in at least got about seven hours of sleep of various hormones and chemi- four distinct ways, so don’t beg off of exercise on weekday nights. Non-exerciscal messengers that can increase just because you feel tired.

© Moneky Business Images | Thinkstock

t may sound strange, but in order to get more energy, you have to do the very thing you don’t feel you have enough energy to do: exercise. Regular exercise boosts your energy in multiple ways. When you understand how, you will never again think of it as a tedious routine that some health nag wants you to do, but rather as a surefire energy enhancer that you can tap into at will.

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Boosting Your Energy


ers reported the least energy and the most sleepiness. However, you should avoid exercising in the two to three hours before you go to bed. Exercising too close to bedtime can make it harder to fall asleep.

How lack of activity drains energy

Picture your energy level as a rechargeable battery. You can plug it in and charge it up with exercise, or let it sit idle and watch the energy drain away.

Why exercise? Energy and beyond Regular exercise helps you feel, think, and look better. Strong evidence from thousands of studies shows that engaging in regular exercise helps ward off numerous diseases. Among its benefits, exercise • reduces your risks for heart disease, stroke, high blood

pressure, and high cholesterol • lowers blood sugar levels and reduces your risk for type 2

diabetes and metabolic syndrome • reduces the risk of certain cancers, including breast and

colon cancers • eases mild to moderate depression • reduces your risk for osteoporosis (provided you do

weight-bearing exercise, meaning exercise where you work against gravity) • helps prevent or ease lower back pain • relieves arthritis pain and expands a limited range of motion • helps maintain muscle mass and prevent falls • boosts mental sharpness in older adults • strengthens your muscles, lungs, and heart • improves functional abilities in older adults—that is,

being able to walk up stairs or through a store, heft groceries, rise from a chair without help, and perform a multitude of other activities that permit independence • helps prevent weight gain and may aid weight loss when

combined with the proper diet • lowers the risk for hip fractures.

Each of the diseases and problems that regular exercise helps protect against can rob people of energy. Thus, regular exercise not only gives you more energy now: it also helps ward off energy-robbing illnesses in the future. In fact, regular exercise does more to protect your health and energy than any medical treatment ever invented or discovered. Through regular exercise, you can do more to protect your health than your doctor can do for you.


Boosting Your Energy 

When you’re inactive, you lose muscle cells­, and the cells that remain have fewer mitochondria. It’s remarkable how little time it takes to see the effects. People who have a limb immobilized because of an injury or illness begin losing muscle cells within just six hours. With weaker muscles, everything you ask your muscles to do requires more effort, leaving less energy for other activities. It’s particularly important to keep exercising as you age because muscle mass tends to decline over the years. Sarcopenia, the gradual decrease in muscle tissue, starts earlier than you may realize—around age 30. The average 30-year-old can expect to lose about 25% of his or her muscle mass and strength by age 70 and another 25% by age 90. The result is not only a decrease in energy, but also an increase in risk for a host of other diseases (see “Why exercise? Energy and beyond,” at left). Lack of exercise also causes changes in your heart and lungs. They become less efficient at oxygenating your blood and pumping that blood (along with nutrients) to all parts of your body. That in turn affects your energy level, most noticeably during periods of physical exertion. Compared with an active person, a sedentary person experiences more fatigue when carrying out a physically demanding task and has both a higher heart rate and lower oxygen consumption. Inactivity also has psychological effects. The less active you are, the less active you want to be. People who don’t exercise have a greater perception of fatigue than people who do.

The exercise prescription

Regular exercise can contribute to a feeling of vitality and energy, and it can also improve your sleep. But what type of exercise should you do? You don’t have to spend a lot of time worrying about this. When it comes to exercise and energy, it’s hard to go wrong— and you don’t have to run for miles or work out to the point of exhaustion to start reaping benefits (see “Exercise regularly,” page 25). Aerobic exercise is an obvious choice, whether you prefer brisk walking, jogging, bicycling, or swimming. In one study of 427 people ages 45 and older, those w w w.h ealt h .ha r va r d.e du

with greater cardiovascular (aerobic) fitness scored higher on a scale measuring vitality than those who were less fit. Studies have demonstrated that aerobic exercise can even reduce fatigue in people who have major health challenges, such as chronic autoimmune conditions or cancer. A review of 36 studies found that 30 to 60 minutes of aerobic exercise three times a week (for at least three months) significantly reduced fatigue in people with diseases such as multiple sclerosis, lupus, and rheumatoid arthritis. A similar review of 19 studies involving people ages 65 and older found that physical activity eased cancer-related fatigue. Most studies linking regular exercise to a greater sense of energy have involved aerobic exercise rather than strength training, so it is difficult to say how strength training compares. However, it probably does help, by building muscle mass and boosting levels of mitochondria. Stronger muscles also mean that the activities that use those muscles can be done more efficiently that is, using less energy. Indeed, many people report an increased sense of energy and alertness from either kind of regular exercise—and a well-rounded exercise program should include both. Even core exercises may help. One recent study of the core-strengthening program known as Pilates found that Pilates improved sleep quality in 22 sedentary people and lessened daytime sleepiness. But

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core work may help improve energy in other, more subtle ways too, beyond enhancing sleep. Among other things, core exercises can help improve your posture whether you’re sitting, standing, or moving. Good posture trims your silhouette and projects confidence—and psychologists say the boost to your psyche may give you mental energy. In fact, the only types of activities that don’t appear to have significant effects on energy are stretching and balance exercises. That doesn’t mean you should ignore them, however, because they have other health benefits. Balance exercises are recommended to help prevent falls. Stretching can help relieve back pain, stiff necks, and sore knees when tight muscles are to blame. If you’re a runner, a tennis player, a golfer, a hiker, or a biker, the right stretching program can set you on a path toward better performance. And as you age, it can help keep you active and flexible, making it easier to accomplish innumerable everyday tasks. It’s never too late to start exercising. If you’ve never had a formal exercise program—or you’ve allowed your exercise regimen to lapse over the years because of illness, time pressures, or family obligations—Starting to Exercise, another Special Health Report from Harvard Medical School, can help you (see “Resources,” page 51). 

Boosting Your Energy


Energy and sleep


f everything we’ve mentioned so far, there is no more obvious influence on energy than sleep. Sleep well, and the next day, everything hums along. Sleep poorly, and you can barely drag yourself through the day’s tasks without a jolt of caffeine. For centuries, scientists scrutinized minute aspects of human activity but showed little interest in sleep. Sleep was perceived as an unvarying period of inactivity when nothing very important happened. Since then, researchers have learned that sleep plays a key role in health and are gradually starting to unravel the complex ways energy depends on adequate sleep.

How sleep boosts your energy

Scientists divide sleep into two major types: REM (rapid eye movement) sleep or dreaming sleep, and non-REM or quiet sleep. Surprisingly, they are as different from each other as each one is from waking— yet both may be important for energy. Non-REM sleep involves three stages. But sleep specialists believe that the last of them—known as deep sleep or slow-wave sleep—is a time for your body to renew and repair itself. This stage of sleep appears to be the one that plays the greatest role in energy, enhancing your ability to make ATP, the body’s energy molecule. In deep sleep, blood flow is directed less toward your brain, which cools measurably. At the beginning of this stage, the pituitary gland releases a pulse of growth hormone that stimulates tissue growth and muscle repair. Researchers have also detected increased blood levels of substances that activate your immune system, raising the possibility that deep sleep helps prepare the body to defend itself against infection. Someone whose deep sleep is restricted will wake up feeling less refreshed than a person who got adequate deep sleep. When a sleep-deprived person gets some sleep, he or she will pass quickly through the lighter sleep stages into the deeper stages and spend 18

Boosting Your Energy 

a greater proportion of time there, suggesting that deep sleep fills an essential role in a person’s optimal functioning. Just as deep sleep restores your body, scientists believe that REM sleep restores your mind, perhaps in part by helping clear out irrelevant information. Studies of students’ ability to solve a complex puzzle involving abstract shapes suggest that the brain processes information overnight; students who got a good night’s sleep after seeing the puzzle fared much better than those asked to solve the puzzle immediately. Other studies, from Harvard Medical School and elsewhere, have found that REM sleep facilitates learning and memory. People who were tested to measure how well they had learned a new task improved their scores after a night’s sleep. If they were prevented from having REM sleep, the improvements were lost. By contrast, if they were awakened an equal number of times from deep sleep, the improvements in the scores were unaffected.

Getting the right amount of sleep

It’s not surprising that getting less sleep than you need leaves you feeling tired, but you may be taken aback to learn that getting more than you need can be just as bad. Many people find that on days when they sleep late, they don’t feel more rested and recharged; instead, they feel more lethargic and unmotivated than usual. That’s because any significant deviation from normal sleep patterns can upset your circadian rhythms. The best solution is to figure out how many hours of sleep are right for you and then stick with it—even on weekends and vacations. For most people, however, the problem is too little sleep, not too much. There are many causes of sleep deprivation, but the most common one is simply burning the candle at both ends. In this 24/7 world, we remain tethered to work and electronic devices well into the night. There are drugs that can help, but w w w.h ealt h .ha r va r d.e du

the first line of defense is to make some basic lifestyle changes that promote sleep (see “Get a better night’s sleep,” page 26). And while caffeine can help keep you awake when you’re dragging, too much reliance on it may make it hard to get a good’s night sleep particularly if you have caffeine after noontime. (For some people, even a single cup of coffee in the morning means a sleepless night.) Caffeine blocks the effects of adenosine, a neurotransmitter thought to promote sleep. It can also interrupt sleep by increasing the need to urinate during the night.

Aging Older people have trouble falling asleep and staying asleep. They wake up more often, and it takes them longer to fall back asleep, in part because melatonin levels decline with age (see “Hormones and brain chemicals,” page 6). Furthermore, though they still spend about 20% of sleep time in REM sleep, as they did when younger, they spend less time in energyrestoring deep sleep. By age 65, people spend less than 5% of sleep time in deep sleep, compared with about 20% when they were in their 20s. Other age-related changes can interfere with sleep as well. Hot flashes can rob women of rest. According to the National Sleep Foundation, 61% of postmenopausal women have insomnia. (For coping techniques, see “Menopause,” page 36.) And with age, people also become more prone to snoring, which can be a sign of sleep apnea (see “Sleep disorders,” page 40). If you think you have sleep apnea, see a doctor for help. This disorder not only drains your energy, but also raises your risk of major illnesses such as heart disease. As you get older, you’re more likely to make up for your nighttime sleep deficit by napping. But if you nap too late in the day or doze too long, the practice can make insomnia worse by preventing you from falling asleep at bedtime. Research comparing 5-, 10-, 20-, and 30-minute naps suggests that, for most people, the optimal nap length for boosting energy and cognitive function is 10 minutes.

Sunday insomnia People often have trouble falling asleep on Sunday nights. While anxiety about work or school on Monww w. h ealt h . h ar v ar d . e du

day is a potential cause, often the most important factor is a weekend change in sleep habits. When you stay up late Friday night and sleep Saturday morning, you are primed to stay up even later Saturday night and sleep in the next day. By Sunday evening, your body’s clock is programmed to stay up late. People who have developed a pattern of Sunday insomnia may feel their anxiety mount as they anticipate a difficult night. The best way to avoid the Sunday blues is to maintain the same wake-up time and bedtime on the weekends as during weekdays. If this isn’t possible and you end up staying up later than usual on Friday and Saturday, the next best thing is to force yourself to get up at your weekday wake-up time and take an early afternoon nap on Saturday and Sunday. This way, you maintain the same wake-up time while compensating for your sleep deprivation.

Health hazards of insufficient sleep The problem with inadequate sleep isn’t just that you feel sluggish. A number of studies of hand-eye coordination and reaction time have shown that sleep deprivation can be as debilitating as intoxication. It also leaves you prone to two potentially dangerous phenomena—microsleeps and automatic behavior. Microsleeps are brief episodes of sleep that occur in the midst of ongoing wakeful activity. They usually last just a few seconds but can go on for 10 to 15 seconds—and pose a grave danger if they happen when you’re driving. Automatic behavior refers to a period of several minutes or more when you’re awake and performing routine duties but not attending to your surroundings. Examples include a driver who keeps the car on the road but misses an intended exit or a train engineer who continues routine functions but fails to notice an obstruction on the track. In addition, long-term sleep deficits can be a contributing factor in some significant illnesses. Problems include a sharp increase in the risks for type 2 diabetes, high blood pressure, and major depression. Sleep loss has also been linked to weight gain, especially in younger people; lack of sufficient sleep tends to disrupt hormones that control hunger and appetite, and the resulting daytime fatigue often discourages a person from exercising.  Boosting Your Energy


Energy and stress


mminent danger gives you a surge of energy. The fight-or-flight response (also known as the stress response) primes your body to either take on an attacker or run for your life. The body churns out stress hormones such as cortisol, epinephrine, and norepinephrine (see Figure 3, at right). In response, blood flow increases to the brain and heart. Your heart pumps faster, your blood pressure goes up, and you take deeper breaths. Glucose floods your bloodstream to provide fuel for muscles. This is a survival mechanism that evolved hundreds of thousands of years ago to protect people in life-threatening situations. But while emergencies and other short-term stressors can energize you temporarily, the stress response guzzles energy, which is why it’s natural to feel fatigued after a stressful event. Imagine the effect when you’re under constant low-level stress— whether from traffic jams, work deadlines, financial issues, or caring for a sick relative. These, too, can evoke the stress response. No wonder these pressures make you feel tired. According to an American Psychological Association poll known as the Stress in America Survey, seven in 10 Americans reported experiencing physical and nonphysical symptoms of stress. These symptoms prominently included fatigue (37%), changes in sleeping habits (30%), and feeling overwhelmed (35%) and irritable or angry (37%). Many people coped with the excess stress by overeating, eating unhealthy foods, skipping meals, or engaging in sedentary activities like listening to music, watching TV or movies, or reading. But here’s the curious thing. People who regularly feel fatigued don’t necessarily have more stressors in their lives than others. In some cases, what is different is their response to stress. Faced with routine frustrations—a rude remark by a store clerk, a computer crashing, an incorrect charge on a credit card— they may get angrier, more anxious, or more nervous. Learning to dial back the stress response can help.


Boosting Your Energy 

Figure 3: The stress response Pituitary gland



Senses sharpen

ACTH released Blood pressure rises

Muscles tighten

Glucose and fats are released into bloodstream

Breath quickens and lungs take in more oxygen Heart beats faster

B Adrenal glands release cortisol, epinephrine (adrenaline), and norepinephrine (noradrenaline)

Collectively, the hypothalamus, pituitary gland, and adrenal glands make up the HPA axis, which plays a pivotal role in triggering the stress response. The hypothalamus sends a chemical messenger (corticotropinreleasing factor, or CRF) to the nearby pituitary gland, which then releases its own chemical messenger (adrenocorticotropic hormone, or ACTH) into the bloodstream (A). ACTH travels to the adrenal glands, which respond by releasing a number of stress hormones into the bloodstream (B). At the same time, the sympathetic nervous system releases stress hormones, too (not shown). The effects of these hormones are widespread, as this illustration shows. Senses become sharper, muscles tighten, the heart beats faster, blood pressure rises, and breathing quickens. This prepares you to fight or flee in the face of danger—but it also consumes a lot of energy. w w w.h ealt h .ha r va r d.e du

Managing the stress response

Although your response to stress is partly genetic, you can moderate it in several ways. One of those is through regular exercise. Exercise is a great stress reducer, as well as an energy booster in its own right (see “Energy and exercise,” page 15). While it is not clear exactly how exercise promotes stress reduction, there are some reasonable theories. Regular aerobic exercise causes the “stress system”—mainly parts of the brain and the adrenal glands—to generate fewer stress hormones (epinephrine, norepinephrine, and cortisol) in response to daily stressors. In addition, by prompting the production of endorphins in the brain, regular exercise also may have a calming effect that helps in dealing with those stressors. You can also learn to moderate the stress response with meditation and other mind-body techniques or with cognitive behavioral therapy, a type of psychotherapy that helps you identify and change negative thoughts and behaviors. Mind-body relaxation techniques have become well-accepted as stress-reducing strategies and are commonly recommended by both mainstream health care providers and integrative

medicine specialists. Although there are many different techniques that work, their common goal is to turn off the stress response by eliciting its opposite—the relaxation response. All relaxation techniques emphasize a strong connection between the mind and the body. This once-novel idea is now widely accepted as scientists probe how the brain works and get a better understanding of how biological events such as fatigue relate to mental conditions. What happens deep inside your cells when you elicit the relaxation response? Exciting new research suggests that this simple act temporarily throws a switch on certain genes, tamping down the activity of genes associated with the chronic inflammation that many experts believe contributes to heart disease, inflammatory bowel disease, and diabetes. At the same time, it turns up the activity of genes linked with the use of energy in the body, particularly the functions of mitochondria, the cells’ tiny energy powerhouses. There is even preliminary evidence that the relaxation response may slow the aging of our cells. To measure gene activity, the researchers used blood samples taken from two small groups of healthy

Practicing mindfulness in daily life

© Antonio_Diaz | Thinkstock


nergy can come in different guises. Sometimes it seems that nothing but a jolt of sugar and caffeine will power you through a tough day. But in the long run, you’re better off with the calm, focused energy you get from mindfulness—a practice that can help you stay “in the moment.” You can try it no matter what else you’re doing, whether it’s washing the dishes or taking a walk. Here’s how:

• Start by bringing your attention to the sensations in your

body. • Breathe in through your nose. Let your abdomen expand

fully. Then breathe out through your mouth. Notice the sensations of each inhalation and exhalation.

Mindfulness meditation can give you a calm, focused energy that helps power you through your day.

• Proceed with the task at hand slowly and with full

deliberation. • Engage your senses fully. Notice each sight, touch, and

sound so that you savor every sensation. • When you notice that your mind has wandered from the

task at hand, gently bring your attention back to the sensations of the moment. Mindfulness is a lifelong practice. Even if you start practicing

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it as a meditation, you will find it expanding to your daily life, helping you to better appreciate simple everyday experiences. By learning to focus on the here and now, you may find yourself less likely to get caught up in worries about the future or regrets over the past. When you waste less energy on stress, you have more energy for activities and other aspects of your life.

Boosting Your Energy


subjects: long-term practitioners of techniques like yoga, meditation, and repetitive prayer; and novices who hadn’t used these techniques before, but who received training in them as part of the study. While the long-term practitioners had the most profound changes in gene activity, the group with eight weeks of training also showed significant changes in gene activity compared with measurements from when they were complete novices. Are you intrigued? See “Practicing mindfulness in daily life,” page 21, and “Quick and easy relaxation techniques,” page 28, for specific methods to try. In addition, here are some forms of exercise that incorporate mind-body techniques. Qigong. This ancient Chinese art melds breathing, meditation, gentle exercise, and flowing movements. (Qi, or chi, is the Chinese word for the life energy believed to course through the body. Qigong is thought to unblock and properly balance the flow of qi.) When practiced regularly, qigong can lower your blood pressure, pulse, and demand for oxygen, as do other techniques that elicit the relaxation response. As a bonus, it may also enhance balance and flexibility. Rhythmic, repetitive activities. Rhythmic exercises, such as walking, jogging, swimming, or bicycling, can be calming and relaxing. Once you get under way, become aware of how your breathing complements the activity. Breathe rhythmically, repeating a focus word, phrase, or prayer you’ve chosen. Remember to adopt a passive attitude. When disruptive thoughts intrude, gently turn your mind away from them and focus on moving and breathing. A mindful walk. Taking a mindful walk is a good example of exercising with relaxation in mind. As you move and breathe rhythmically, be aware of the sensations of your body. How does it feel as your breath flows in through your nostrils and out through your mouth? Gradually expand your awareness to the sights and smells around you. Notice the freshly mown grass,


Boosting Your Energy 

flowers, trees, fallen leaves, dappled sun, or gray clouds. How does the outside air feel against your body? How does the surface beneath your feet feel and sound? What thoughts are moving through your head? A slow, mindful walk helps center and relax you. Alternatively, a brisker pace that pushes your limits can be calming and energizing in equal parts. In this case, place more emphasis on the sensations of your body, such as your quickened breathing and heartbeat and the way your muscles respond as you tax them. Tai chi. This mind-body exercise regimen, which consists of a series of flowing postures that you perform in a set sequence while centering your mind, is an excellent form of physical activity to reduce stress and boost vitality in older adults. It is an easy exercise regimen to adopt and can break the cycle of sedentary behavior, while improving balance, coordination, flexibility, muscle strength, and stamina. In addition to reducing stress, tai chi can improve body awareness and reduce social isolation when it’s practiced in a group setting. Sessions, which usually last an hour, begin with meditation and progress to the postures, which are performed slowly (although some styles of practice are done at higher intensity). Body posture and deep breathing are key elements of correct practice, and regular, ongoing sessions confer the most benefit. Yoga. Like tai chi, yoga is a proven stress buster with numerous studies showing substantial benefits for the mind and body. To begin with, research demonstrates that the practice of yoga reduces the burden of mental stress, which expends a lot of the body’s energy resources. In addition, yoga improves physical health and the quality of sleep over the long term, which adds up to more vigor. And because stress plays a role in worsening the symptoms caused by most diseases, yoga may be even more beneficial for chronically ill people than for healthy individuals. Regular practice yields the most benefit. 

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A 6-step plan to jump-start your natural energy


here is no pill or energy drink in the stores that will magically restore the energy of your youth. (Only if you have an underlying illness causing fatigue will medication help—by treating the illness, not by directly boosting your energy.) However, certain lifestyle changes—outlined in the six-step plan below—can go a long way toward improving your energy, mood, and overall health. Because these approaches address both the physical and psychological aspects of fatigue, they can improve your strength and ability to exert yourself and sustain your motivation.

© Cathy Yeulet | Thinkstock

Simply getting outdoors in nature can help restore your body and soul, reduce stress, and give you some exercise, all of which can boost your energy.

You’ll want to tailor the strategies to your individual needs, so before reading this section, get a notebook or electronic device so that you can write down each step, followed by the specific changes you can make to accomplish that item. Writing your goals down can help you stay on track. Making daily entries can help you monitor your progress and stay focused.


Eat for energy

Caffeine and sugar can give you a temporary lift. But in the long run, the only diet that will keep you functioning at your best is a well-rounded, healthful diet (see “Energy and food,” page 8). It gives you the vitamins and minerals you need for generating energy. It gives you the unrefined carbohydrates and healthy unsaturated fats that supply the reserves you’ll need throughout the day. But what does this healthy, energy-boosting diet look like? Try these tips.

Let the Harvard Healthy Eating Plate be your guide. With

the overload of diet advice out

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SPECIAL SECTION | A 6-step plan to jump-start your natural energy

there, it can be hard to separate objective, scientific recommendations from those that are slanted by commercial or other agendas. That’s why teams from Harvard Health Publications and the Harvard T.H. Chan School of Public Health came up with a graphical approach to healthy eating (see Figure 4, below right). As you’ll see from the Healthy Eating Plate, half of every meal should consist of fruit and vegetables. Carbs are good, as long as they’re the wholegrain variety. For protein, choose fish, fowl, beans, and nuts over red meat. When you eat a diet packed with vegetables, fruits, nuts, whole grains, healthy fats, and lean protein, you not only consume the finest energy-boosting foods, but you also promote good health—an energy booster in itself.

noon slump. The reasons for this are unclear, but it may reflect the increase in blood sugar after eating, which is followed by a drop in energy later. Avoid crash diets. If you need to lose weight, do so gradually, without skimping on essential nutrients or starving yourself of the calories you need for energy. Poor nutrition and inadequate calorie intake can cause fatigue. And remember to eat regularly throughout the day, even when you’re dieting. Your brain needs a steady supply of glucose from food. When the brain’s glucose levels are low, some people feel hungry, fatigued, or both, which can then trigger a bout of overeating.

Use caffeine to your advantage. Caffeine can increase or

decrease your energy level, depending on when and how much of it you consume. Caffeine does help increase alertness for an hour or two after consumption, so having a cup of coffee before going to a meeting or starting on a project can help sharpen your mind. But it can also cause insomnia, especially when consumed in large amounts or after 2 p.m. (or even noon, if you’re caffeine-sensitive). Limit alcohol. If you’re going to drink, do so in moderation at a time when you don’t mind having your energy wind down. The sedative effect of alcohol is especially strong at midday, when you

Figure 4: Eating for energy and health

Eat small, frequent meals … but don’t overeat. When energy

is the issue, it’s better to eat small meals and snacks every few hours than three large meals a day. This approach can reduce your perception of fatigue because your brain, which has very few energy reserves of its own, needs a steady supply of nutrients. Some people begin feeling sluggish, headachy, or lightheaded after just a few hours without food. But it doesn’t take much to feed your brain—a piece of fruit or a few nuts is adequate. Smaller is especially better at lunch. Researchers have observed that the circadian rhythms of people who eat a lot at lunch typically show a more pronounced after-


Boosting Your Energy

When you eat a diet packed with vegetables, fruits, nuts, whole grains, healthy fats, and lean protein, you not only consume energy-boosting foods, but you also promote good health.

A 6-step plan to jump-start your natural energy | SPECIAL SECTION

normally feel a bit lethargic anyway, so one of the best hedges against the midafternoon slump is to avoid alcohol at lunch. Similarly, avoid the five o’clock cocktail if you want to have energy in the evening to pursue a hobby, stay awake through a movie, spend time with your family, or finish that report for work the next day. That said, many experts advise against having a nightcap just before going to bed. Though alcohol initially relaxes you and causes drowsiness, several hours later it begins to stimulate the brain—particularly the sleep/wake centers. For this reason, it may help you to fall asleep, but the stimulating effect that kicks in two to three hours later may awaken you and make it difficult to get enough deep, restorative sleep for the rest of the night. If you do choose to drink alcohol, a glass with dinner is a reasonable choice. And stay within the limits of moderation: no more than two drinks a day for men and one for women. Drink water. What’s the only fluid that has been shown to enhance performance for most activities? It’s not some pricey sports drink. It’s water. If your body is short on fluids, one of the first signs is a feeling of fatigue. Sports drinks such as Gatorade and Powerade combine water with sugar, vitamins, minerals, and electrolytes—sodium, chloride, potassium, and other substances that help regulate body processes. But

these add-ons won’t give you extra energy for ordinary, everyday activities, and these drinks may provide more calories than you burn. You don’t need them unless your workout is extremely strenuous or long, or you sweat profusely and lose nutrients through perspiration. How much water do you need? The Institute of Medicine recommends that women consume a total of about 91 ounces of fluids a day (about 11.5 cups) and men about 125 ounces (16 cups). These fluids can come from a combination of drinks (such as water, milk, coffee, tea, or soda) and solid foods that contain water (such as fruits and vegetables), so you don’t actually need to drink 16 cups of fluid a day: five to eight is good enough.


Exercise regularly

Exercise is the energy booster that is so counterintuitive, most people don’t even think of it. But it’s a proven way to increase your vim and vigor (see “Energy and exercise,” page 15). The Physical Activity Guidelines for Americans recommend 150 minutes of moderate aerobic activity per week (for example, half an hour five days a week) or 75 minutes of vigorous activity, or a mix of the two. The guidelines also advise engaging in two to three strength training sessions per week. Allow at least 48 hours between these muscle-building workouts to give your body time to recover. However, certain people—particularly those with chronic fatigue

syndrome or multiple sclerosis, those who are elderly, or those who have long been couch potatoes— should start slowly and build gradually. Some evidence indicates, for example, that aerobic exercise can aggravate symptoms in some people with chronic fatigue syndrome. And people with multiple sclerosis are prone to overheating quickly, which can make them feel weak and fatigued. Check with your doctor for advice based on your own health history before you begin an exercise program. Whether you are doing aerobic exercise or strength training, start each exercise session with a fiveto 10-minute warm-up. Marching in place and gently swinging your arms, dancing to a song on the radio, or starting slowly on a treadmill or exercise bike are excellent ways to warm up. At the end of each session, finish with a five- to 10-minute cool-down, such as slow walking, until your heart rate and breathing return close to normal. Stretching is also essential at the end of a session to work out muscle kinks and improve range of motion and balance. Aerobic activity. The most convenient and affordable form of aerobic activity is walking. Studies have shown that brisk walking for at least half an hour, five times a week, has nearly the same health benefits as more vigorous exercise (see “How fast is brisk?” on page 26). People who take brisk walks have a lower risk for heart disease, diabetes, high blood pressure, high Boosting Your Energy


SPECIAL SECTION | A 6-step plan to jump-start your natural energy

How fast is brisk? A brisk walk is generally 3 to 4 miles per hour. But since humans don’t come equipped with built-in speedometers, you need some way to measure your walking speed. One way is to count your steps per minute. Provided you’re walking on level ground, you can use the following as general guidance to gauge your pace: • Slow = 80 steps per minute

• Fast = 120 steps per minute

• Moderate to brisk = 100 steps

• Race walking = More than 120

per minute

cholesterol, colon cancer, osteoporosis, and perhaps other diseases. Even mental health problems are less frequent in regular walkers. Although it hasn’t been studied, many regular walkers also believe that this exercise makes them more energetic. If you are starting an exercise program for the first time, begin with a slow walk around the block almost every day. Then, as your energy level rises and your muscles become conditioned, gradually spend more time exercising. Increase the length and intensity of your walk to a degree that’s challenging but not overwhelming. If you are up for more vigorous workouts, you can try running, hiking, biking, aerobic dancing, or swimming. In truth, exercise intensity is dictated more by your level of fitness than the activity—so even a walk can be termed “vigorous” if you pick up the pace and boost your heart rate. Many experts offer the following rule of thumb for aerobic exercise: If you can talk easily while performing your routine, exercise harder. If you can’t carry on a conversation at all, back off. 26

Boosting Your Energy

steps per minute

Strength training. Resistance

exercise, such as weight lifting, is especially beneficial for people in their 60s and older because it builds muscle mass. Weight lifting doesn’t have to involve heavy barbells. Lifting light hand weights can provide adequate resistance, as can using strength training machines at the gym. Choose weights as light as 2 pounds for your first few strength training sessions so you can concentrate on good form—you want to isolate muscles by trying to move only those that you’re exercising. After that, add enough weight so that the maximum number of repetitions you can do per set is about eight to 12. The last few repetitions in each set should require a good deal of effort. Aim for two to three sets per exercise, breathing out as you lift and breathing in as you lower the weight. Rest between sets for a minute to reap the best strength gains. Be sure to exercise all of the major muscle groups of the legs, trunk, arms, and shoulders. Yoga and tai chi. Yoga and tai chi (see page 22) can enhance

energy, too, while also improving balance, coordination, flexibility, muscle strength, and stamina. In addition, a study published in the Journal of Physical Activity and Health found that doing 20 minutes of yoga postures led to better cognitive functioning—specifically, an improved ability to focus and take in and use new information—than 20 minutes of aerobic exercise.


Get a better night’s sleep

Nothing saps your energy faster than a poor night’s rest (see “Energy and sleep,” page 18). But you don’t have to toss and turn all night. Most ordinary sleep difficulties can be solved with a simple set of behavioral changes. (If you suffer from a disorder such as sleep apnea, however, you’ll need to see a doctor who specializes in sleep.) Practice good sleep hygiene.

People who have difficulty sleeping often come to associate their bedroom with the frustration of trying and failing to get to sleep. These associations create anxiety, worsening the insomnia. Reconditioning is a behavioral technique for breaking such negative associations. Here’s what to do: • Use the bed only for sleeping or sex. Watch TV or read in a different room, and keep your bedroom dark for sleep. (That also means covering up lights from chargers and electronic devices. Better yet, keep laptops, cellphones, and other devices in a different room.)

A 6-step plan to jump-start your natural energy | SPECIAL SECTION

• Go to bed and get up at the same time every day, including weekends, to keep your sleep/wake cycle synchronized to your circadian rhythms. Also, try to go outside in natural light early in the day. This will help reset your internal clock. • If you don’t fall asleep quickly, don’t lie in bed tossing and turning and worrying about not sleeping. Get up and go to another room to read or do something calming for half an hour. Then try sleeping again. Avoid smoking. Smoking harms your health in many ways, including increasing your risk for lung cancer and heart disease. But it also siphons off your energy by causing insomnia. Smoking can ruin your sleep with a kind of onetwo punch. As a central nervous system stimulant, the nicotine in tobacco speeds up your heart rate, raises blood pressure, and stimulates brain-wave activity associated with wakefulness, making it harder to fall asleep. What’s more, once you do fall asleep, its addictive power can kick in and awaken you with cravings. People who quit smoking fall asleep more quickly and wake up less often during the night. Although at first many former smokers experience sleep disturbances and daytime fatigue, they often report improvements in their sleep relatively soon. Exercise. Exercise is the only proven way to increase the amount of time you spend in deep sleep,

the type of sleep that is most restorative for your energy. The more deep sleep you get, the less likely you are to awaken in the middle of the night, and the more rested you’ll feel the next day. The National Sleep Foundation’s 2012 survey found that even 10 minutes of light, moderate, or vigorous physical activity had a beneficial effect on sleep, both its duration and its quality. In particular, aerobic exercise, which increases your heart rate, makes it easier to get to sleep and gives you more hours of energy-enhancing deep sleep each night. For normal sleepers, exercising at any time of the day or night can be helpful and shouldn’t interfere with sleep, according to experts. This is well documented in young adults, but less well documented in older adults. If you find that you have trouble falling asleep when you exercise vigorously in the evening, you would be wise to avoid strenuous activity for two to three hours before you go to bed. Restrict your sleep. If you think you may be sleep-deprived, try getting less sleep. That’s right: get less sleep, at least for a few days. People with insomnia often spend more time in bed, hoping this will lead to sleep. In reality, spending less time in bed—a technique known as sleep restriction—promotes more restful sleep and helps make the bedroom a welcome sight instead of a torture chamber. As you learn to fall asleep quickly and sleep soundly, the time in bed

is slowly extended until you obtain a full night’s sleep. Some sleep experts suggest starting with six hours at first, or whatever amount of time you typically sleep at night. Setting a rigid early morning waking time often works best. If the alarm is set for 7 a.m., a six-hour restriction means that no matter how sleepy you are, you must stay awake until 1 a.m. Once you are sleeping well during the allotted six hours, you can add another 15 or 30 minutes, then repeat the process until you’re getting a healthy amount of sleep. Take sleep medications only as a last resort. Although such medications can be helpful in the short term to break a pattern of insomnia, when used long-term, they may actually worsen your fatigue by leaving you groggy during the day. In addition, prescription sleep medications can cause tolerance (the need for progressively larger doses over time to get the same effect). Over-the-counter sleep aids, which typically contain antihistamines, are often ineffective and, in some people, cause irritability. However, when used occasionally, they work well for some individuals.


Control stress

The most common cause of persistent fatigue is stress and the emotional response to it (see “Energy and stress,” page 20). Stress-induced emotions consume huge amounts of energy. Some people are naturally better than others Boosting Your Energy


SPECIAL SECTION | A 6-step plan to jump-start your natural energy

at coping with such emotions, but everyone can learn to modulate them to some degree. Engage in a hobby. Emerging data show that knitting, crocheting, and other rhythmic and repetitive craft activities can be potent stress relievers. For one thing, they distract you from your worries. A seminal study published in The Journal of the American Medical Association found that sewing was more stress-reducing than playing a card game, reading a newspaper, or other activities. The researcher concluded that the act of performing a craft is so absorbing and enjoyable that it is incompatible with worry, anger, obsession, and anxiety. Most importantly, perhaps, crafts and hobbies can induce the relaxation response, the polar opposite of the stress response. The act of doing a task over and over again breaks the train of everyday thought and calms both the body and mind. Use relaxation techniques.

You can’t eliminate stress from your life, but you can learn relaxation techniques that work as an antidote to stress. Deep breathing, meditation, progressive muscle relaxation, and visualization can evoke a state of rest and release. These kinds of relaxation exercises trigger physiological changes, such as lowering blood pressure, slowing heartbeat and respiration, and reducing blood lactate levels, which may be linked with anxiety attacks. If you’re pressed for time, mini relaxation exercises and the 28

Boosting Your Energy

practice of mindfulness can help (see “Quick and easy relaxation techniques,” below, and “Practicing mindfulness in daily life,” page 21). Lighten your load. An overly committed schedule, whether it consists of professional, family, social, or volunteer activities, can sap your energy level. Everyone needs some downtime to relax and restore—even high-energy types. A good first step toward reducing your load is to streamline your list of “must-do” activities. You don’t

need to accept every social invitation, volunteer for every work assignment, or run the entire community fund-raiser yourself. Some people are overloaded because they have trouble saying “no.” If you already have more responsibilities than you can comfortably handle, don’t take on any more. Set your priorities in terms of the most important tasks. Pare down those that are less important. Overload that’s strictly jobrelated is particularly hard to

Quick and easy relaxation techniques


he next time you’re stuck in traffic or faced with a situation that annoys you, one of the following quick relaxation techniques may help ease your day.

➤ When you’ve got one minute

Place your hand just beneath your navel so you can feel the gentle rise and fall of your belly as you breathe. Breathe in slowly. Pause for a count of three. Breathe out. Pause for a count of three. Continue to breathe deeply for one minute, pausing for a count of three after each inhalation and exhalation. ➤ When you’ve got three minutes

While sitting down, take a break from whatever you’re doing and check your body for tension. Relax your facial muscles and allow your jaw to fall open slightly. Let your shoulders drop. Let your arms fall to your sides. Allow your hands to loosen so that there are spaces between your fingers. Uncross your legs or ankles. Let your legs fall comfortably apart. Feel your shins and calves become heavier and your feet grow roots into the floor. Now breathe in slowly and breathe out slowly. Each time you breathe out, relax even more. ➤ When you’ve got five minutes

Try self-massage. Begin by putting fingertip pressure on muscle knots. Knead across muscles, and try long, light, gliding strokes. You can apply these strokes to any part of the body that falls easily within your reach. For a short session like this, try focusing on the muscles in your neck. Next, massage your face. Make a series of tiny circles with your thumbs or fingertips. Pay particular attention to your temples, forehead, and jaw muscles. Use your middle fingers to massage the bridge of your nose and work outward over your eyebrows to your temples. End by closing your eyes. Cup your hands loosely over your face and inhale and exhale easily for a short while.

A 6-step plan to jump-start your natural energy | SPECIAL SECTION

control, especially if you work in a company or a profession where very long days are the norm. Learn efficiency techniques—such as creating schedules for tasks and sticking to them—that let you meet your work goals without working harder or longer than necessary. Consider asking for extra staff or temporary assistance at work. Or ask your boss to help you prioritize your tasks; if nothing else, that will make him or her realize how much you’re doing. Exercise. Regular aerobic exercise seems to help control stress. It causes the “stress system”—mainly parts of the brain and the adrenal glands—to generate fewer stress hormones (epinephrine, norepinephrine, and cortisol) in response to daily stressors. Such exercise generates the production of endorphins in the brain, and these molecules have a calming effect.


Use nature’s energy

Anyone who enjoys the outdoors, whether for gardening, hiking, or taking walks along the beach, knows that getting outside can help restore body and soul. There aren’t many scientific studies documenting that communing with nature can actually fight fatigue, but scientists are beginning to explore this theory. For instance, recent research found that the more time people spent visiting green spaces (such as parks and gardens) in four European cities, the better their mental health and the greater their feeling

of vitality (defined as less fatigue and more energy). Other research also suggests that being in nature can have therapeutic and restorative effects. This supports a theory developed by Harvard biologist Edward O. Wilson known as “biophilia,” which holds that humans have an innate connection to the natural world and to other living things, and that contact with nature can benefit your health. Hospitals and rehabilitation centers often include “healing gardens” as retreats for patients, staff, and visitors to walk and sit in. In addition, some occupational and physical therapy programs offer “therapeutic gardens” where you can participate in a range of both horticultural and nonhorticultural interactive activities. Studies of horticultural therapy and therapeutic gardens, conducted around the world, confirm that gardening and spending time in nature are associated with a host of cognitive, psychological, physical, and social benefits that include reducing anxiety, decreasing physical and psychological measures of stress, boosting mood, improving one’s sense of well-being, stimulating memory and concentration, and improving the immune response and overall physical health. Evolution may indeed have hard-wired us to prefer natural places. If nothing else, getting outdoors can help reduce stress by taking your mind off troubling thoughts. And communing with nature often goes hand in hand

with exercise, a known energy booster.


Keep focused on goals

If you’re having trouble making these changes stick, this is a perfect time to step back and consider some of the reasons why you want to have more energy. Is it simply to feel good? Are there activities you would enjoy if only you had more energy? Motivation in itself is an important aspect of energy. And reaching goals is enormously satisfying—the greater your sense of well-being, the higher your energy level is likely to be. So if you need to reinforce your resolve, try this. Get out a pencil and jot down the things in your life that have most inspired you. Have you trained for a marathon? Earned an advanced degree? Raised money for charity? Created a website? Now make a list of the things that you most enjoy doing, such as traveling, gardening, playing a musical instrument, socializing, reading a good book, or playing bridge, golf, or tennis. Look at the two lists. Are there ways to combine the things you love with goals you can accomplish? The idea is to find something that will be stimulating and energizing, not something that’ll feel like just one more chore. Planning a trip can be stimulating, for example, and saving the money for it can give you a goal. Try to focus on your priorities, so that you channel your energy into the activities that truly matter to you.  Boosting Your Energy


Fatigue: Energy’s enemy


hen you lack energy, you feel physically weak, mentally dull, or both. Effort of any sort can tire you out quickly. This absence of energy is often referred to as fatigue, and it’s a common phenomenon that has been viewed differently over the years. Sometimes when you lack energy, you feel tired or drowsy. But fatigue is not just sleepiness: it includes components that are physical (weariness or weakness), mental (lack of concentration and sharpness), and emotional (lack of motivation or boredom).

Changing views of fatigue

In today’s 24-hour society, fatigue is thought of as something to be avoided, conquered, or, at the very least, denied. But fatigue did not always have a negative connotation. In medieval writings, for example, fatigue is often portrayed as a positive, normal sign that a person has reached his or her limit, and it’s time to rest. The notion that fatigue is an unwelcome condition to be studied and overcome first became popular in the mid-19th century, with the advent of industrialization and its demand for a steady source of indefatigable factory workers. By 1900, the study of fatigue was in full swing, with fatigue laboratories cropping up throughout Europe and scholarly papers about the new science of ergography, or work capacity, filling scientific journals. Interest grew as the military sought to understand how to boost energy and thereby increase the productivity of workers in munitions factories during World War I. Later, the focus of military research shifted from physical to mental fatigue as increasing numbers of tasks—from piloting airplanes to operating radar— required sustained mental alertness. Today, this line of research is changing the way scientists think about fatigue. Some people are better than others at performing well despite a lack of sleep, 30

Boosting Your Energy 

according to a number of Air Force scientists working with pilots. These researchers are using brain imaging technology to examine people who are resistant to fatigue, in hopes of determining whether there is something different about these people’s brains compared with people who cannot perform well when sleep-deprived. It may be that people who decide to become pilots self-select for this characteristic, the researchers suggest, as people who cannot perform well when sleep-deprived are less likely to become pilots. The scientists also hope to find out whether there is a brain chemical that influences this ability.

How common is fatigue?

One of the significant challenges facing contemporary scientists studying fatigue is how to measure its prevalence. Unlike diabetes, obesity, or other well-defined medical conditions, fatigue is very difficult to define because it has varied symptoms and, like pain, is both an objective and subjective state. Moreover, fatigue is part of the human experience and is, at times, entirely normal. In the absence of a clear-cut definition or objective “fatigue test,” attempts to measure how many people experience fatigue—and when it crosses the line from normal to abnormal— are imprecise at best. Despite these hurdles, researchers who have looked at the results of numerous epidemiological (population-based) studies of fatigue have been able to draw some conclusions about how common it is. The first is that fatigue is very common, reported by anywhere from 5% to 45% of people. In a comprehensive health survey of more than 9,000 adults in Britain, for example, only headaches were a more common bothersome symptom than fatigue. And in approximately 5% to 10% of people, bothersome fatigue persists for at least six months. Fatigue tends to become more noticeable with age and chronic illw w w.h ealt h .ha r va r d.e du

nesses, such as arthritis, cancer, or cardiovascular disease. Perhaps not surprisingly, fatigue is also one of the leading reasons people around the world visit primary care providers (see Figure 5, below). One U.S. survey concluded that fatigue was responsible for more visits to primary care doctors than colds, rashes, headaches, or chest pains. Unfortunately, doctors and patients often disagree about the causes of fatigue. In a Dutch study of adults complaining of fatigue, doctors had no idea what was causing the fatigue in a third of the cases. Studies have shown that fatigue can have multiple simultaneous causes and can be associated with many variables, including demographic, social, cultural, and psychological factors. One study involving more than 29,000 adults found that fatigue is common in urban areas and that the highest levels of fatigue occurred among women and people with lower levels of education and less prestigious jobs. There are many theories as to why women might report higher levels of fatigue, ranging from their role in society to the biological differences between women and men and the higher

Primary care doctors are often the first to hear from their patients when fatigue becomes a problem. Here's what one survey revealed about patients who reported symptoms of fatigue to their primary care doctors:



were female



were having trouble sleeping



were feeling symptoms of depression


were feeling stress or worry

were experiencing fatigue lasting more than one year

Source: Canadian Medical Association Journal, November 2009.

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Two types of fatigue

Ask any three people what fatigue feels like, and you’re likely to get three different answers. That’s because the experience that people call “fatigue” may refer to very different things—for example, muscular weakness, lack of endurance, slow reaction times, or poor concentration. The experience of fatigue is often classed as one of two general types: muscle fatigue and central (or brain) fatigue. Muscle fatigue and central fatigue are closely related. When you feel fatigued, you’re usually feeling the effects of both. But you can also experience one without the other. Although the mechanisms are not well understood, the two types of fatigue look different inside the body.

Muscle fatigue

Figure 5: The front line of fatigue


incidence of depression among women, which is associated with fatigue. Other studies conducted in various countries have found that people in lower social classes are more fatigued than those of a higher social standing.

Muscle fatigue is the weakness you feel in your muscles when you’ve tired them out. Make a fist with one hand, then open and close it as fast as you can for one minute, and you’ll feel some weakness in your hand muscles. Then repeat the sequence a few more times. Chances are, your muscles won’t contract as fast as they did when you first started the experiment. To understand how muscles become fatigued, it’s essential to understand the chain of events that makes them work. The first part of the muscle contraction process occurs not in the muscles but in the brain. The motor cortex, the area of the brain that controls movement, sends a nerve impulse to muscles in your arms and hands. To reach the appropriate muscles, the nerve impulse travels down the spinal cord and through a pathway of nerves to the neuromuscular junction, a tiny space between the end of a nerve and the surface of a muscle. A chemical signal travels across the neuromuscular junction to land on the muscle. This, in turn, triggers a series of chemical reactions in the Boosting Your Energy


muscle cells that ultimately leads to the breakdown of ATP, which then provides the energy that enables the muscles to contract. When muscles become fatigued, they don’t contract as forcefully or as quickly as muscles that are not tired. Fatigued muscles have certain characteristics, including a buildup of acid, particularly lactic acid. But it’s not known whether the acid buildup causes the muscle to become fatigued, or whether it occurs along with the fatigue. Therefore, it’s unclear whether attempts to change the acid concentration of exercising muscle—as has been proposed by some fitness professionals—would allow a muscle to work longer and harder without getting fatigued. Although some experts suggest that gradually increasing the intensity of your training and eating a combination proteincarbohydrate snack within 15 minutes after a workout will help reduce lactic acid, there’s no proof that this will increase your endurance or energy level. Many diseases damage muscle fibers. An example is muscular dystrophy. When some fibers are damaged and cannot function effectively, it puts a strain on the muscle fibers that are not damaged. A vicious circle ensues that leads to more muscle damage and muscle fatigue. Other diseases affect the transmission of signals from nerves to muscles. An example is myasthenia gravis. You move a muscle when your brain sends a signal to the muscle to move. When disease interrupts that signal, muscles simply fail to move.

Central (brain) fatigue When most people say they are fatigued or lack energy, they are describing a brain condition called central fatigue or brain fatigue. What they mean is that they are having trouble paying attention or concentrating, or feeling motivated to perform. They may also mean that they feel sleepy. Specific areas of the brain, using certain natural brain chemicals, are responsible for attention and concentration. Other areas are centrally involved in motivation. Still others are involved in alertness and sleepiness. Central fatigue is, to a great degree, a perception or a state of mind. As a result, central fatigue is a much less objective and measurable phenomenon 32

Boosting Your Energy 

than muscle fatigue. Your perception of fatigue usually increases with your muscle fatigue, but the two aren’t always in sync. Experiments show that a person’s perception of fatigue can decline even as the muscles are expending ever more energy and, in all likelihood, showing more signs of fatigue. But sometimes the opposite happens: your perception of fatigue can be greater than your muscle fatigue. You can feel fatigued without having expended much energy at all. Emotional and psychological factors significantly affect how fatigued you feel. Scientists have a method of measuring the perception of fatigue. It’s called the rating of perceptual effort, or RPE. To use this method, an exercising person is asked to pick a number on a scale ranging from no fatigue to maximum imaginable fatigue. Scientists have found that, in general, the more effort you think you’re expending, the more fatigued you will feel. Like the sensation of pain, the perception of fatigue is highly personal. It varies from one individual to the next, depending on personality as well as mood. Fatigue is greater and comes on sooner in people with mood disorders such as depression or anxiety than in those who don’t have these illnesses. An individual’s perception of fatigue can change depending on the situation. In experiments, researchers have been able to manipulate people’s RPEs during physically challenging activities. For example, giving a subject feedback on his or her performance decreases the perception of fatigue, possibly because it helps keep the person motivated to improve. Maintaining mental focus on an activity is one method coaches use to improve athletes’ performances. By contrast, distractions tend to increase a person’s perception of fatigue. When people are distracted, their minds wander. They may think about how tuckered out they should be or anticipate how drained they’re likely to feel if they keep going. They may also think about easier, more pleasurable things they’d rather be doing and then, subconsciously, “feel” fatigued by their present activity. Based on experiments with humans and animals, researchers suggest that certain chemical or electrical stimuli in the brain can alter perceptions of fatigue during exercise. However, none of these experiments w w w.h ealt h .ha r va r d.e du

have yet provided a fatigue-preventing treatment that can be used to improve performance. In the past 20 years, research has also discovered that the immune system can profoundly affect mental functions. The brain has its own immune system that fights infections and helps repair perceived injuries. In waging this fight—a process called inflammation— immune system cells make natural chemicals (cytokines) that send signals to other immune system cells to attack. These chemicals can also alter the function of the brain’s neurons—the cells that do the work of the brain, such as thinking, seeing, feeling, and directing movement. Excessive amounts of cytokines produced over a prolonged period can interfere with attention and concentration, motivation, and alertness. Scientists used to think that the brain was walled off from the rest of the body’s immune system. However, recent research has revealed that inflammation or immune system activation anywhere in the body, such as the intestines or the kidneys, can also affect attention, motivation, and alertness.

When to see a doctor

Even though fatigue is one of the most common medical complaints, you may feel hesitant about making a doctor’s appointment just to say you lack energy. But if you feel so weary or lethargic that you can’t do particular activities as well or as often as you once did, it’s important to make an appointment. Perhaps you used to play tennis once a week without any problem, but now you get winded during the game. Or maybe by the end of the day you often feel too tired to cook dinner or go out to a movie. These are good reasons to see a doctor. Start with your internist or family doctor to find out if you have an underlying medical or psychological illness. Because fatigue is a characteristic of many illnesses, you should describe your symptoms in detail to help your doctor narrow down the possible causes. How, exactly, does the fatigue feel to you? Do you have trouble concentrating? Are you mentally fuzzy—for example, do you take longer to think of words or perform simple math calculations than you used to? Do you tire more quickly? Do certain activities take more ww w. h ealt h . h ar v ar d . e du

Doc around the clock


atigue and sleep deprivation are ongoing concerns for medical residents in hospitals and for the patients they treat. Residents typically work long hours, sometimes with little or no sleep. Fully trained physicians and surgeons, too, may work overnight on call and face a regular schedule of patients the next day. As sleep experts concluded in an article in The New England Journal of Medicine, “Sleep deprivation adversely affects clinical performance and impairs psychomotor performance as severely as alcohol intoxication.” The Accreditation Council for Graduate Medical Education has published guidelines restricting medical trainees in their first postgraduate year to a maximum of 16 hours of continuous work and those in their second postgraduate year to 24 hours. Paradoxically, research studies have not found these restrictions to have improved patient care or reduced medical errors. If you or someone you know is in the hospital, keep this issue in mind. At any time, even in the middle of the day, if the doctor appears exhausted, it’s appropriate to ask how long he or she has been on duty. And if a doctor tells you in the evening or at night that you need an emergency medical or surgical procedure, ask how long that doctor and the doctors doing the procedure have been on duty. It’s a perfectly fair question, and if the answer is that they have been on duty longer than 16 hours, consider asking for a second opinion.

effort than they used to? Answers to these questions indicate how severe your fatigue is and whether it mainly involves muscle fatigue, central fatigue, or both. Be prepared to tell your doctor which activities you’ve had to limit. For example: • You used to enjoy going out to dinner and the theater with friends, but now you can’t stay awake during an evening performance. • You no longer wake up feeling refreshed, even after you’ve slept all night. • When you exercise, your muscles feel achy and weak in less time than they once did. • You’ve done the newspaper crossword puzzle for years, but now your mind wanders, and you lose interest before finishing it. This information yields further clues to the nature and severity of your fatigue. Timing is also important. Tell the doctor when you started noticing a decrease in Boosting Your Energy


your physical or mental energy level. Was the change gradual or sudden? When fatigue involves stress, overwork, or psychological problems, it usually comes on gradually. However, when the cause is chronic fatigue syndrome, fibromyalgia, or a side effect of medication, fatigue often starts suddenly. Did the onset of fatigue coincide with any other significant change in your life: Had you been ill? Did you have an injury? Did you start taking a new medication? Was there a death in the family or among your friends? Are you under an exceptional amount of stress? Your symptoms could be related to any of these factors. Also, make sure to tell your doctor about any other symptoms you might be experiencing. Give details about when the different symptoms began and whether they started together or at different times. Mention physical as well as emotional symptoms. Do you get out of breath easily? Do your muscles or joints ache? Do you have trouble sleeping? Are you feeling unusually sad or anxious? Different symptoms accompanying fatigue suggest different causes. For example,


Boosting Your Energy 

feeling blue and having trouble sleeping are two signs of depression. Shortness of breath can be a sign of heart disease. Diagnosing the cause of fatigue really amounts to a process of elimination. Piece by piece, your doctor will review the evidence about you—your symptoms, your physical examination, and the results of your tests— and compare this evidence to the possible causes. Diseases and conditions that do not fit your case will be discarded, and further testing may be done to examine the diseases that might fit your case. Your primary care physician can easily treat some conditions, such as anemia and diabetes. Others will require the care of a specialist, for example, a psychiatrist for depression or a cardiologist for heart disease. For most people suffering from fatigue, however, a firm diagnosis can’t be made. In such cases, persistent fatigue may be due not to an illness, but rather to some aspect of a person’s daily life—stress, overwork, poor sleep habits, overeating, and other issues discussed in this report—or some combination of these. 

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Common causes of fatigue


he cause of fatigue is not always obvious (see Figure 6, below right). If you have the flu or have just eaten a big lunch, fatigue is to be expected. But if you feel inexplicably groggy throughout the day, not just during the biological trough that normally occurs in midafternoon, that’s reason for concern. Report your symptoms to your doctor. The underlying cause of persistent fatigue can be hard to identify, but that doesn’t mean the fatigue is imaginary. Fatigue often signals that something is wrong, physically or emotionally, or even with the pace and tempo of your daily schedule. This chapter explores some of the most common causes of an ongoing lack of energy.

Shift work

About one-fifth of Americans work nonstandard hours, according to the U.S. Bureau of Labor Statistics. Odd work schedules often go against the body’s natural biological rhythms and can even pose a health risk. In addition to causing fatigue, changes in your worksleep schedule in the short term can lead to irritability, trouble concentrating, slower reflexes, accidents, stomach upset, diarrhea, constipation, and heartburn. Over the long term, night shift work can increase the risk of cardiovascular disease, diabetes, obesity, cancer, depression, and serious gastrointestinal illnesses. Even more challenging than steady night shift work is continually switching back and forth from day hours to night hours. One study found that nurses who rotated every couple of days from day to night shifts were less alert and more likely to make mistakes when checking medical orders and prescriptions than nurses who worked a steadier schedule. In a Sleep in America poll, almost half of train operators and a third of pilots said their work schedules interfered with their ability to get adequate sleep; half of both groups said they never got a good night’s sleep on work nights. ww w. h ealt h . h ar v ar d . e du

A 2015 study from Harvard Medical School tested people’s ability to drive a car on a test track under two separate conditions—after seven hours of sleep and after working the night shift. Following night shifts, participants drove less well (for example, they wove between lanes). They also were sleepier, as determined by measurements of their brain waves and eye movements. Most important, near crashes occurred in 38% of tests following a night shift versus none after a good night’s sleep.

Figure 6: Causes of fatigue Some causes of fatigue are obvious, such as lack of sleep or a medical illness, but many others are harder to pinpoint. Depression or anxiety, overwork, sedentary living, nutritional factors, or even a medication could contribute to fatigue or cause a feeling of low energy. Stress


Sleep difficulties Depression or anxiety

Chronic fatigue syndrome


Multiple sclerosis


Nutritional factors




Boosting Your Energy


Asleep on the job


f you’re having trouble focusing at work or feeling stressed or unmotivated because of fatigue, you’re not alone. A Virgin Pulse survey of 1,139 people found that 76% of workers feel tired at least one day of the work week, if not most days. In fact, 40% admitted to dozing off while at work at least once a month, and 15% said they doze off between once a day and once a week at work. The workers identified a lack of sleep as the primary culprit in their fatigue. Specifically:

• 85% said the temperature in their bedroom was too

high or too low for adequate sleep. • 72% blamed their partner. • 69% cited unwanted noise as the problem. • 53% said the room was too bright. • 40% felt their mattress wasn’t conducive to good sleep. • 36% had young children to tend to in the middle of

the night. • 10% had medical conditions that disturbed their sleep. Source: Virgin Pulse Institute, “Asleep on the Job” (2014).

If you work the night shift, try to avoid exposure to sunlight on the way home (which will cue your body to wake up); wear sunglasses if it’s already light out. Sleep in a very dark room or wear a sleep mask. Give yourself a few days to switch over to the new schedule—it takes time, just as it does when you change time zones. Finally, as you adjust, try to sleep and wake at the same time each day, which can improve the quality of your slumber and reduce fatigue.


Overwork is another common cause of persistent lack of energy. Americans work long hours. During the 1990s, people added an average of 36 hours of work, or nearly a full week, to their work year. Small wonder that a study by the Families and Work Institute found that a third of employees in the United States said their work drains them so much that they have little energy left over for their personal or family life. Overwork isn’t limited to the time spent working and commuting. There’s also the “second shift” 36

Boosting Your Energy 

of meals and household chores, as well as social obligations and the responsibility of caring for an aging spouse, parent, or young children. This second shift is usually longest for women, who generally shoulder more of the home and family responsibilities even when they work full-time (see “Caring for a family member,” page 37).


The hormonal changes that occur during the years leading up to and following menopause can have a profound effect on sleep and, as a result, can contribute to fatigue. The most common menopausal symptom is hot flashes, which affect approximately 80% of women undergoing natural menopause. In addition to making you feel as if someone just cranked up the heat, hot flashes often leave you flushed and soaked with perspiration. Not surprisingly, hot flashes that occur when you’re sleeping (sometimes called night sweats) can awaken you many times during the night. Even if your hot flashes don’t wake you up, they can still disrupt your sleep. And a night of insufficient or poor-quality sleep can make you feel fatigued, lethargic, or sleepy the next day, not to mention irritable and moody. Hot flashes eventually stop, usually within seven years and sometimes sooner. In the meantime, there are some behavioral changes you can make to reduce the frequency and intensity of hot flashes, especially at night. One is regular practice of a yoga breathing technique called paced respiration, in which you breathe deeply and slowly for several minutes. (You can also try it during a hot flash, to lessen its duration.) Weight loss has also been shown to be effective. Other strategies can help you deal with hot flashes when they occur. Dressing in layers during the day, so that it is easy for you to remove clothing when you start to feel hot, helps many women, as does keeping a fan or glass of cold water at the ready. And using a Chillow (a pillow filled with cool water) or wearing moisture-wicking pajamas may reduce the impact of night sweats on your sleep. If lifestyle changes don’t offer adequate relief, talk to your doctor about whether medication may be right for you. The most effective treatment for reducw w w.h ealt h .ha r va r d.e du

ing hot flashes is hormone therapy. Studies show that short-term hormone therapy improves sleep quality in women suffering from night sweats and other menopausal symptoms. Because studies have revealed risks from using hormone therapy for an extended period, experts recommend taking hormones at the lowest effective dose for the shortest possible duration, to minimize the potential risks. If you can’t or don’t want to take hormone therapy, there are other hormonal and nonhormonal options, including birth control pills, clonidine (a blood pressure medication), and the pain and seizure drug gabapentin (Neurontin). Some antidepressants can also diminish the intensity of hot flashes.


Hundreds of over-the-counter and prescription drugs can cause daytime drowsiness or fatigue. The most common classes of drugs associated with such side effects are antihistamines, blood pressure medications, antibiotics, antidepressants, and anti-anxiety drugs. Drugs can cause sleepiness or fatigue in several ways. Some medications, such as antihistamines for allergies and colds, do so by depressing the central nervous system. Others initially act as stimulants, but ultimately leave you tired because they keep you awake at night. Among these drugs are theophylline, used to treat asthma and other upper respiratory problems, and nicotine patches to help smokers quit. Still other medications can cause muscle weakness, including certain drugs that normalize an irregular heartbeat (anti-arrhythmic agents). If you’re taking a drug that is known to cause drowsiness or fatigue, don’t stop without talking with your doctor. First, not all drugs that can cause such side effects do so in every person who takes them. Just because you’re using a medication that can cause fatigue doesn’t necessarily mean that it’s the source of your fatigue. Second, if the drug is responsible for your sleepiness or fatigue, your doctor may be able to prescribe another medication that won’t have the same effect. If there’s no available substitute, you might be able to reduce the side effects by taking the medication at ww w. h ealt h . h ar v ar d . e du

a time of day when drowsiness or fatigue is less of a problem, such as in the evening. For example, people with allergies can often take an oral antihistamine at night, when its sleep-inducing effect isn’t a problem, and control symptoms during the day with a nasal corticosteroid spray, such as budesonide (Rhinocort, Pulmicort), which doesn’t cause drowsiness.


Alcohol can cause fatigue in two ways. First, as a sedative, it depresses the central nervous system. So drinking wine, beer, or hard liquor during the day can make you feel drowsy or lethargic. If you didn’t sleep well the night before, even one drink can make you drowsy, especially if you drink during one of your usual low-energy times—for example, midafternoon or late evening. Second, though a nightcap may make you feel drowsy at first, alcohol has delayed effects that can interfere with sleep. Several hours after drinking, alcohol raises the body’s level of epinephrine, a stress hormone that increases the heart rate and generally stimulates the body, which can result in nighttime awakenings. Indeed, alcohol may account for 10% of chronic insomnia cases. Alcohol can also interrupt sleep by relaxing throat muscles, thereby worsening nocturnal breathing problems and causing sleep apnea. It also may disrupt sleep by causing the need to urinate during the night. So while a drink before bedtime may make it easier to fall asleep, it may cause you to awaken more easily and to spend less time in deep sleep.

Caring for a family member

Perhaps you are among the one in five American adults helping an elderly or disabled family member with the daily tasks of life. The spectrum of tasks that unpaid caregivers undertake is vast. It runs the gamut from grocery shopping, cooking, and cleaning house to helping with baths or personal hygiene or providing hands-on medical care. As the very embodiment of love and commitment to others, caregiving is one of the most worthwhile jobs you may ever undertake, but it can be exhausting and cause undeniable strain. Boosting Your Energy


Relief for the caregiver


aregiving can drain your energy and lead to depression and health problems. If you are a caregiver, you owe it to yourself and the people you love to stay healthy, reasonably happy, and sane. The tips below are designed to help you take care of yourself so you can regain your vitality. Ask for help. Tell friends and family the job is too much for you alone. Ask them to help brainstorm solutions. Always accept help when it’s offered. Some people will make specific offers of help. You can encourage others to choose from a list you create of what’s needed or assign jobs you’ve matched to their capabilities. Tap into religious communities. A religious or spiritual community can be a strong source of assistance if you or the person you are caring for belongs to one. Try a support group. Many organizations, hospitals, health care plans, and religious groups offer support groups for caregivers. Support groups are a good place to blow off steam and share ideas with people who are facing similar situations. Lean on friends. Friends who listen— and offer advice only when you ask directly—are invaluable. Try to choose people who aren’t judgmental. Ask outright if you can use them as a sounding board whenever the need arises. Bundle errands. Make a weekly master list of everything that needs to be done, including appointments,

shopping, drugstore runs, trips to the gas station, and other errands. Dole out simple tasks, if possible, or do as much as you can in one time slot. Clear your schedule. Set aside time to spend with a partner or family. Start small—just one evening a week, or breakfast out together if you’re caring for someone in your home—and add to it when you can. Let the answering machine pick up calls during certain hours. Look for shortcuts. Could cooking happen on certain days only? If a clean house is important to you, can you make your room an oasis of clean and calm while being less strict about other areas? Can you let some jobs slide or hire help to get them done? Refuse to do it all. Opt for grocery delivery or cleaning services that can give you more time for yourself. Consider outside respite services, such as adult day care, once or twice a week. Can other family members help pay for these services? For more information, go online to HelpGuide ( and search for “adult day care services.” Quell your guilt. Caregiving attracts guilt like a magnet pulls iron filings.

About six in 10 family caregivers juggle work responsibilities while caring for someone else. And caregiving itself amounts to a part-time job: the average caregiver puts in 24 hours of “helping time” per week. Perhaps not surprisingly, many of the 44 million adult caregivers in the United States suffer from emotional and physical stress, which can lead to fatigue.


Boosting Your Energy 

There’s always something else you could be doing or should have done. But odds are good that you do a great deal. Pat yourself on the back for all you give; don’t excoriate yourself for failing to give more. Eat well. Include plenty of vegetables and fruits in your diet, and choose whole grains over refined-grain products. Limit or cut out unhealthy fats and excess sweets. Keep healthy snacks available, like air-popped popcorn or fruit. Stay active. Frequent exercise delivers proven health benefits, such as lowering cholesterol and blood pressure. Try to get 30 to 60 minutes of moderate exercise a day, most days of the week. Enjoy yourself. Listen to music you like, enjoy a luxurious bath, take a yoga class, do an activity you enjoy, or go out to dinner. Regular time off can renew your spirit and energy and remind you that you’re neither invincible nor completely irreplaceable. Stay connected. Catch up with friends by phone or email. Establish a weekly walk with a friend or an occasional lunch or movie. Ease stress. Take time to alleviate stress. Learn meditation or other relaxation techniques. See the stressrelieving tips and exercises in “Control stress,” page 27.

If you are a family caregiver, you frequently act with someone else’s happiness and health in mind. But for the sake of your own health, try to care for yourself as well (see “Relief for the caregiver,” above). For starters, take a break once in a while to spend time with friends or on activities that make you happy. Check with your employer about what resources might be available to you. Try to find ways to relieve physical and emotional stress. 

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Diseases that cause fatigue


host of illnesses can cause fatigue, from depression and anxiety to sleep disorders, chronic fatigue syndrome, fibromyalgia, anemia, heart failure, multiple sclerosis, traumatic brain injury, cancer, chronic infections, and hormonal disorders.

Depression or anxiety

As many as 20% to 40% of people who seek help for ongoing fatigue suffer from depression or anxiety.

How depression and anxiety affect energy With depression, fatigue can manifest itself in two ways. One is mental fatigue, specifically a decreased drive or motivation to do things that you once enjoyed. Another is a change in sleep patterns—some people sleep more than usual, others develop insomnia. Either way, they grow weary during the day. Depression doesn’t have to be severe to cause fatigue. Persistent depressive disorder (formerly called dysthymia) can make a person feel tired or fatigued much of the time. People with anxiety, on the other hand, are prone to panic, fear, and other high-stress responses, which cause fatigue by increasing levels of stress hormones. These people are also more likely to have chronic highstress reactions, the most debilitating and energyrobbing kind. Anxiety causes a host of emotional and physical symptoms, including worry, restlessness, and irritability, as well as rapid heartbeat, hyperventilation, upset stomach, or general aches and pains. Many people with anxiety also suffer from depression. Developing knowledge of brain chemistry, genetics, nerve pathways, and the biology of stress has led to a greater understanding of depression. It’s often said that it results from a chemical imbalance, but that description doesn’t capture how complex the disease is. Research suggests that depression doesn’t spring from simply having too much or too little of certain ww w. h ealt h . h ar v ar d . e du

brain chemicals. Rather, depression has many possible causes, including genetic vulnerability, stressful life events, and faulty mood regulation by the brain.

How do you know you have depression or anxiety? There are certain hallmark signs and symptoms that can tip you and your doctor off that you have depression or an anxiety disorder. Depression. Having four or more of the following symptoms—in addition to feeling sad or burdened or losing interest in nearly all activities on most days for at least two weeks—may indicate major depression: • a change in appetite that sometimes leads to weight loss or gain • insomnia or, less often, oversleeping • a slowdown in talking or in performing tasks or, conversely, restlessness and an inability to sit still • loss of energy or feeling tired much of the time • feelings of worthlessness or excessive, inappropriate guilt • problems concentrating or making decisions • thoughts of death or suicide, or suicide plans or attempts. Anxiety. Doctors look for excessive anxiety and worry occurring more days than not for at least six months, plus at least three of the following symptoms: • restlessness • being easily fatigued • difficulty concentrating • irritability • muscle tension • disturbed sleep.

Treating depression Regardless of the cause, getting help for depression and anxiety is extremely important. Several therapies, including medication and psychotherapy, can relieve the symptoms of depression within a matter of weeks. Boosting Your Energy


Certain medications to treat anxiety work almost immediately. If you suspect that you are suffering from depression or anxiety, start by seeing your primary care doctor. He or she can assess your symptoms with the goal not only of uncovering depression or anxiety, but also of diagnosing possible underlying medical problems. If the evaluation points to depression, the doctor may suggest some combination of antidepressant medication, psychotherapy, and lifestyle changes such as exercise. Medication. Antidepressants work by adjusting levels of brain chemicals that play a role in depression. Selective serotonin reuptake inhibitors (SSRIs), one class of antidepressants, increase the brain’s level of serotonin, a neurotransmitter that affects mood, arousal, anxiety, impulses, and aggression. SSRIs are the most commonly prescribed medicines for depression. Serotonin and norepinephrine reuptake inhibitors (SNRIs) constitute another class of antidepressants; as their name implies, they target not only serotonin levels, but also levels of norepinephrine, a neurotransmitter that affects mood, anxiety, and drive. Tricyclic antidepressants, an older class of medication, also increase both serotonin and norepinephrine. Tricyclic antidepressants are often the best choice for someone with sleep problems, although they should be prescribed with caution in people with known heart disease. In addition, there are some antidepressants that don’t fall neatly into one class or another. Since side effects vary among medications, your doctor can recommend the one that’s best for you. Psychotherapy. Another effective way to beat depression is psychotherapy with a qualified counselor, such as a psychiatrist, psychologist, or social worker. The combination of psychotherapy with an antidepressant is often an effective strategy and has been gaining favor recently. Exercise. A sustained exercise program can improve the mood of people with mild or moderate depression. It might also augment antidepressant treatment for people with severe depression. You don’t have to exercise a lot to obtain mental health benefits: studies have found that doing an average of 30 minutes or more of moderate-intensity aerobic exercise at 40

Boosting Your Energy 

least three times a week can alleviate mild or moderate depression as effectively as antidepressants or cognitive behavioral therapy (a form of psychotherapy that aims to correct ingrained patterns of negative thoughts and behaviors). Besides boosting your mood, exercise can also increase your energy level.

Treating anxiety As with depression, anxiety can be treated with medications, psychotherapy, or both. For long-term treatment of anxiety, there are two options: antidepressants or the anti-anxiety drug buspirone (BuSpar). In addition, short-term psychotherapy is at least as effective as anti-anxiety medications alone. Cognitive behavioral therapy is especially helpful.

Sleep disorders

Sleep disorders can cause fatigue. Besides insomnia— which can be a symptom of many medical and mental health conditions—these disorders include restless legs syndrome and narcolepsy. The most common sleep disorder, however, is obstructive sleep apnea. Sleep apnea occurs when the upper airway is blocked by excess tissue such as a large uvula, the tongue, the tonsils, fatty deposits in the airway walls, nasal congestion, or a floppy rim at the back of the palate. People with sleep apnea tend to have smaller airway openings then those who don’t. A narrow airway makes obstruction all the more likely when airway muscles relax at the onset of sleep. A potentially life-threatening lack of oxygen and buildup of carbon dioxide, as well as increasing efforts to breathe, cause the sleeper to wake and gasp loudly for air until blood oxygen levels return to normal. Some people with sleep apnea repeat this cycle hundreds of times a night without being aware of it.

How sleep disorders affect energy Sleep disorders wreak their havoc in different ways. With sleep apnea, periodic gasping for air may pull people back from deeper stages of sleep into lighter ones that are not as refreshing—or may actually wake them up, so they have difficulty getting back to sleep. Restless legs syndrome, by contrast, may make it difw w w.h ealt h .ha r va r d.e du

A SAMPLE SLEEP HISTORY QUESTIONNAIRE In order to better understand your sleep habits, your doctor may ask you some of the following questions during an evaluation for a sleep problem. You may find it helpful to write down your answers to these questions and bring the completed questionnaire to the exam so you and your doctor can discuss it. 1.  What bothers you most about your sleep habits? 2.  How long have you had trouble sleeping, and what do you think started the problem? Did it come on suddenly? 3.  How would you describe your usual night’s sleep? 4.  What time do you go to bed, and when do you wake up? 5.  What’s your bedroom like? 6. What do you do in the few hours before bedtime? 7.  Do you follow the same sleep pattern during the week and on weekends? If not, how are weekends different? 8.  How well do you sleep on the first few nights when you’re away from home? At home, do you sleep better in your bedroom or in another room in the house? 9.  Do you fall asleep at inappropriate times or places? 10.  Do allergies or nasal congestion bother you at night? 11.  What medications or drugs (including alcohol and nicotine) do you use? Have you ever taken sleep medications? If so, which ones?

ficult to fall asleep in the first place or compel a person to get in and out of bed many times per night. While narcolepsy’s symptoms tend to be most evident during the day, when people may suddenly fall asleep for a few seconds or even several minutes, the opposite also occurs—unwelcome awakenings can deprive sufferers of restorative sleep at night. Regardless of how and why a sleep disorder arises, any problem that routinely reduces your total amount of sleep or frequently interrupts it can make it impossible for you to feel fully rested.

How do you know you have a sleep disorder? If you suspect that you have sleep apnea or another sleep disorder, talk with your doctor. He or she may refer you to a sleep specialist, who will ask you questions assessing the quality of your sleep (see “A sample sleep history questionnaire,” above). You may also need to do a sleep study. This is an overnight test— often done in a hospital or special laboratory, though increasingly done at home—in which monitoring ww w. h ealt h . h ar v ar d . e du

12.  Do you have physical aches and pains that interfere with sleep? 13. Do you often have indigestion at night? 14.  Do you ever feel discomfort or a fidgety sensation in your legs and feet when you lie down? Do you have to get up and walk around to relieve the feeling? 15. Do you kick or thrash around at night? 16.  Do you ever have trouble breathing when you lie down, or do you awaken because it’s hard to breathe? 17.  Does your bed partner or roommate mention that you snore loudly or gasp for air at night? 18.  Do you ever awaken with a choking sensation or a sour taste in your mouth? 19.  Do you wake up with a headache or with cramps in your legs? 20.  How have you been feeling emotionally? Does your life seem to be going as well as you would like?

devices record your brain waves, heart beat, breathing, eye movements, and leg movements.

Treating sleep disorders Though basic sleep hygiene is always a good idea (see “Get a better night’s sleep,” page 26), you may need to take additional steps. Insomnia. Finding a remedy for insomnia requires uncovering the cause. Nearly half of insomnia cases stem from psychological or emotional problems. Stressful events, mild depression, or an anxiety disorder can keep you awake at night. With proper treatment of the underlying cause, the insomnia usually recedes. If it doesn’t, additional treatment focusing on sleep may help. The two main approaches to treating insomnia—behavioral therapy and medications—are both effective, but behavioral therapy has proven to be longer lasting and doesn’t have the side effects that can occur with medications. In particular, a variation of cognitive behavioral therapy—called CBT-i—uses talk therapy to target unproductive thinking patterns and Boosting Your Energy


habits that fuel insomnia and has been shown to be as good as or better than sleep medications. Sleep apnea. The best treatment for sleep apnea is usually the use of a CPAP (continuous positive airway pressure) machine at night. Restless legs syndrome. Exercise can ease the symptoms. Drugs that ease the tremors of Parkinson’s disease also reduce the number of leg movements and thus improve quality of sleep. Narcolepsy. The first-line drugs are two “wakefulness-promoting agents,” modafinil (Provigil) and armodafinil (Nuvigil).

Chronic fatigue syndrome

According to the CDC, about one million to four million adults in the United States suffer from chronic fatigue syndrome (CFS). (Another name for this condition—myalgic encephalomyelitis/chronic fatigue syndrome, or ME/CFS—is increasingly being used in the scientific community.) CFS is about twice as common in women as in men, and can occur (less often) in teenagers and younger children. The causes of CFS are still unknown, and there is no accurate diagnostic test. However, scientists have concluded that it is not a psychiatric illness (see “CFS and depression,” below). They have identified a number of abnormalities in the brain and nervous system that are associated with the disease.

CFS and depression Some doctors have questioned whether CFS is a form of psychiatric illness, particularly depression. But psychiatric studies find that most people with CFS have no history of psychiatric illness in the years before developing CFS, and a substantial number—25% to 50%—don’t develop depression even after the onset of their illness. There is other evidence that CFS is not a manifestation of depression. For example, certain brain hormone levels that are often seen in people with depression are not seen in people with CFS. Also, one study found that the antidepressant fluoxetine (Prozac) did not relieve either fatigue or depression in people with CFS. 42

Boosting Your Energy 

How CFS affects energy CFS affects many parts of the body and also alters basic energy production. The brain. Many studies indicate that the symptoms of CFS are most likely caused by abnormalities in the brain, particularly in a part of the brain called the limbic system that governs emotions. These differences in the brain show up on imaging tests, such as magnetic resonance imaging (MRI), in studies of various brain hormones, and in studies of brain waves. Some research has found that people with CFS also have variations in genes that affect the function of the limbic system. The autonomic nervous system. The autonomic nervous system is the part of the nervous system that controls vital involuntary body functions such as blood pressure, heartbeat, and body temperature. Many people with CFS show a tendency for blood pressure to drop and the heart to race when they stand up and remain on their feet after sitting or lying down. Doctors are testing various medications that might correct this condition. The immune system. Various parts of the immune system are continually activated in CFS, as if the immune system is engaged in a battle against something it perceives to be foreign. There is no evidence of an immune system deficiency that would make people with CFS especially vulnerable to infection, such as occurs with AIDS. CFS can follow an infection with Epstein-Barr virus, human herpesvirus-6, parvovirus, or the spirochete that causes Lyme disease. However, it has not been proven that any of these infectious agents is the cause of the persistent symptoms of CFS. Also, there are cases of CFS that do not start with an apparent infection. Most experts think it is unlikely that CFS is caused by a single infectious agent, in the way that AIDS is caused by a single kind of retrovirus (HIV). Energy metabolism. Every cell in the body makes the energy it needs to live and perform its function. In CFS, there appear to be irregularities in cellular energy production and the function of the mitochondria—the tiny “power packs” inside every cell where energy is made. Oxidative stress. Oxidants, also known as free radicals, are unstable oxygen molecules that damage w w w.h ealt h .ha r va r d.e du

cell membranes, proteins, and DNA. As the mitochondria generate energy, they produce oxidants as a chemical byproduct. However, the body produces antioxidants that help block or repair such damage. In CFS, there appears to be a state of “oxidative stress” in which levels of oxidants outstrip the levels of antioxidants.

How do you know you have CFS? CFS is defined by a set of symptoms. In 2015, a panel of experts convened by the Institute of Medicine concluded that for a person to be diagnosed with CFS, the illness must have lasted at least six months, be causing substantial impairment of normal activities, be causing profound fatigue that is new in a person’s life, and be accompanied by several other important and distinctive symptoms: • Post-exertional malaise: A prolonged worsening of fatigue after exertion or stress. The effect may not be seen immediately. • Unrefreshing sleep: Feeling unrefreshed after sleeping many hours. • Cognitive impairments: Problems with thinking that grow worse after physical or mental exertion, effort, stress, or time pressure. • Orthostatic intolerance: A pattern in which symptoms worsen when you sit up or stand, and improve at least in part if you lie back down or elevate your feet. The symptoms of CFS tend to wax and wane, but most people remain impaired to some degree, even on their good days. Unlike other causes of persistent fatigue, which come on gradually, CFS often appears suddenly, with an infectious-like illness (having symptoms such as fever, sore throat, or aching muscles).

Treating CFS About 50% or more of children with CFS eventually recover, but only 15% to 40% of adults do. However, certain treatments and lifestyle modifications can help relieve the symptoms. Set priorities. Make a list of the things that you want to have more energy to do, and eliminate as many nonessential activities and obligations as you ww w. h ealt h . h ar v ar d . e du

can. The goal is to conserve your energy for the most important activities in your life. At the same time, guard against becoming too passive. Push yourself to your limits, and trust your body to know when you’ve reached those limits. Exercise. An exercise program in which you gradually increase your activity level can be effective in reducing the severity of symptoms. Ask your doctor for a referral to a physical therapist who knows about CFS and can help you design an exercise program that is light enough that it doesn’t cause exhaustion, but challenging enough that it’s invigorating. Cognitive behavioral therapy. This type of psychotherapy helps you identify and change negative thoughts and behaviors. It can help some people cope and can reduce symptoms, but not everyone benefits, and it is not a cure. Tricyclic antidepressants. Low doses of a tricyclic antidepressant (such as amitriptyline) seem to improve the quality of sleep, reduce pain, and increase energy. As yet, no scientific studies have been conducted of this treatment in patients with CFS, but studies have found a clear benefit from low-dose tricyclics in people with a similar illness, fibromyalgia. Other medications. The headaches, joint pain, and muscle pain that characterize CFS can be relieved with nonsteroidal anti-inflammatory drugs (NSAIDs), such as ibuprofen (Advil, Motrin) or naproxen (Aleve), or another over-the-counter painkiller, acetaminophen (Tylenol). There is some evidence that fish oil capsules (3,000 mg per day) may also help reduce the symptoms of CFS. Experimental treatments. Among experimental approaches currently being explored are medications to treat abnormalities of the autonomic nervous system, specific antiviral drugs, and drugs that target the immune system. None of these treatments has yet proved effective.


Fibromyalgia, which affects 2% to 4% of Americans, is similar to CFS—so similar that many experts view them as variants of the same condition. Both disorBoosting Your Energy


ders are more common among women; both produce symptoms of unremitting fatigue and muscle pain; and both can begin following an infection. But in fibromyalgia, pain, more than fatigue, is the predominant symptom. Psychiatric problems, such as depression and anxiety, are also more common in people with fibromyalgia than in the general population.

How fibromyalgia affects energy People suffering from fibromyalgia have a heightened sensitivity to pain, which is debilitating physically and emotionally. These individuals have high levels of chemicals in the brain that sense pain, and they have low levels of other chemicals that tend to reduce pain.

This double whammy is called “central sensitization” by doctors.

How do you know you have fibromyalgia? The symptoms that lead to the diagnosis of fibromyalgia are shown in Figure 7, below. Areas of tissue that become painful when pressed, particularly in the locations shown, are called “tender points.” They often develop in people with fibromyalgia, occur less frequently in people with other conditions (such as chronic fatigue syndrome), and occur rarely in healthy individuals.

Treating fibromyalgia Given the similarity between fibromyalgia and CFS,

Figure 7: Diagnosing fibromyalgia Fibromyalgia is now seen as a continuum with greater and lesser degrees of pain. The American College of Rheumatology developed the following criteria to aid doctors in diagnosis and give them a sense of where a patient falls on the continuum. 1. Put an X over each red dot that indicates an area where you have had pain or tenderness in the past seven days. Be sure to mark the right and left sides separately. This indicates how widespread your pain is.

Right jaw

Right shoulder

Right lower arm

• Chest

or breast


Left upper arm

Right lower leg


Upper back

Left lower arm •

• Lower back hip/ • Left buttocks

hip/ • Right buttocks Right upper leg

• •

Left jaw Left shoulder

Right upper arm

Left upper leg

Left lower leg

Boosting Your Energy 

No problem Slight or mild Moderate Severe

a. Fatigue b. Trouble thinking or remembering c. Waking up tired (unrefreshed)

3. D  uring the past six months, have you had any of the following symptoms? No Yes

a. Pain or cramps in the lower abdomen b. Depression c. Headache

☐ ☐

☐ ☐

4. H  ave the symptoms in questions 2 and 3 and pain been present at a similar level for at least three months? ☐ ☐

5. D  o you have a disorder that would otherwise explain the pain? ☐ ☐

Adapted from Clauw DJ. "Fibromyalgia and related conditions." Mayo Clinic Proceedings (Jan. 2015), Vol. 90, No. 5, pp. 680–92.


2. U  sing the following scale, indicate for each item your severity over the past week by checking the appropriate box.

SCORING: Give yourself 1 point for each location checked on the body map (0–19), 0–3 points for the severity of each of the three issues in question 2 (a total of 0–9), and 1 point each for irritable bowel, depression, and headache. You meet diagnostic criteria for fibromyalgia if you have (1) a widespread pain index of 7 and symptom severity score of 5, or a widespread pain index of 3–6 and symptom severity score of 9, (2) symptoms that have been present at a similar level for at least three months, and (3) no other disorder that would explain the pain.

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it’s not surprising that, in many cases, the same treatments are helpful for both. Heat and massage can relieve musculoskeletal pain in the short term. Light- to moderate-intensity aerobic exercise— such as swimming, walking, biking, or low-impact step classes—can also reduce muscle pain and tenderness. Start slowly and gently, and build in intensity as you become more fit and tolerant of exercise. It also helps to perform strengthening and stretching exercises twice a week to build muscle and improve flexibility. Cognitive behavioral therapy can help people cope with the pain of the illness. Studies show that tai chi and yoga both may be excellent exercises for people with fibromyalgia. If you decide to try either of these forms of exercise, however, be sure to tell your instructor that you have fibromyalgia, so he or she can alert you to modifications for postures that may be difficult or painful for you, and recommend cushions, straps, bolsters, and even chairs to lessen the stress on your musculoskeletal system. Several medications offer many patients pain relief, although not perhaps as much as exercise and cognitive behavioral therapy. These include the muscle relaxant cyclobenzaprine (Flexeril), drugs used to manage epilepsy such as gabapentin (Neurontin) and pregabalin (Lyrica), and the antidepressants amitriptyline (Elavil), milnacipran (Savella), and duloxetine (Cymbalta).

Multiple sclerosis

Multiple sclerosis (MS) is an unpredictable autoimmune disease affecting about 400,000 people in the United States and about 2.3 million worldwide. With MS, the body’s immune system mistakenly attacks myelin, the substance that surrounds and protects nerve fibers. Most people with MS experience their first symptoms between the ages of 20 and 40, but a diagnosis is often delayed because of the transitory nature of the disease. People experience symptoms during “flare-ups” that could last weeks or months, followed by a period of remission before symptoms reappear.

How MS affects energy The most debilitating part of MS can be severe fatigue, which affects approximately 80% of people ww w. h ealt h . h ar v ar d . e du

with the disease. Even in the absence of muscular weakness or fatigue, there is often central (brain) fatigue in which general exhaustion and difficulty concentrating is so great that it’s difficult to engage in any activity. While most people with MS have fatigue, other symptoms can vary significantly from one person to the next, depending on the location of affected nerve fibers. Symptoms range from mild to severe and can be long-lasting or short-lived. They may include anything from vision problems to dizziness, tremors, bladder and bowel problems, and depression. Although most people recover completely between flare-ups, some suffer progressive loss of function, which can lead to advanced muscle weakness, paralysis, and blindness. Imaging studies have shown a correlation between MS fatigue and reduced metabolism of glucose in certain areas of the brain responsible for processing and motivation. This may explain why MS fatigue frequently includes both muscle and central fatigue. Sometimes, however, fatigue in MS is the secondary effect of other symptoms. For instance, sleep disturbances caused by bladder problems or nighttime spasms—both common symptoms of MS—can lead to daytime fatigue. Depression is also a contributor. Yet these symptoms can’t explain the full extent of exhaustion experienced by most MS patients.

How do you know you have MS? In some people who are unaware that they have MS, fatigue is the most prominent initial red flag, while other symptoms are minimal. How can someone tell if fatigue is a symptom of MS? There are certain characteristics that set MS fatigue apart from the fatigue typically experienced by healthy individuals. They include fatigue that • is more intense and debilitating than what healthy people experience after sustained physical, mental, or emotional exertion • occurs on a daily basis for at least half of all days for six weeks or more • is worsened by heat and humidity • tends to come on suddenly • interferes with daily activities or duties • inhibits the ability to concentrate Boosting Your Energy


• occurs early in the morning, even after a good night’s rest. Usually fatigue is accompanied by another early sign of MS—such as numbness and tingling in your arms, legs, or elsewhere in your body—but sometimes it’s the only early indicator. If you are experiencing the symptoms above, talk to your doctor. He or she will be able to determine if you should be evaluated for MS.

Treating MS-related fatigue Even if you have MS, there are ways to boost your energy levels. The best approach is a comprehensive plan that combines lifestyle changes and medications. Your doctor can help you identify factors contributing to your fatigue, so that you can minimize their impact. The following are some general tips for increasing your stamina. Exercise. Regular exercise can improve cardiovascular fitness and muscle strength as well as mental health and reduce fatigue in people with MS. Be sure to start slow, and stop if you become tired. A physical therapist can develop a regular exercise program tailored to your fitness level and individual needs. Stay cool. MS fatigue can be worsened by heat. During warmer months, be sure to exercise in the morning or late evening when it’s coolest. So you don’t overheat, take frequent breaks and consider wearing a cooling vest. Address sleep problems. Treat symptoms that interfere with sleep, including spasticity (stiffness or spasms in certain muscles) or urinary problems. Talk to your doctor about sleep medications. Also, see “Get a better night’s sleep,” page 26. Adjust your routines. Plan ahead to bundle errands, pace yourself, and conserve your energy. Talk to your employer about reducing your workload, altering your schedule, or working at home some of the time. An occupational therapist can help you simplify tasks at work and home that may be draining your energy. Medications. MS is one of the great success stories in medicine, and numerous drugs are now being marketed to treat it, including injectable interferons (Avonex, Betaseron, Extavia, Plegridy, Rebif) and glatiramer acetate (Copaxone, Glatopa) and the infusible 46

Boosting Your Energy 

drugs natalizumab (Tysabri) and alemtuzumab (Lemtrada). Three oral drugs have been released as well: teriflunomide (Aubagio), dimethyl fumarate (Tecfidera), and fingolimod (Gilenya). All of these medications may arrest the progression of the disease and disability, especially when they are started soon after diagnosis, but they do not generally affect the symptom of fatigue. Short-term clinical trials have shown that amantadine (Symadine, Symmetrel), a drug that helps restore the balance of neurotransmitters in people with Parkinson’s disease, improves fatigue in patients with MS. Other treatments that may improve fatigue are • modafinil (Provigil) and armodafinil (Nuvigil), drugs used to increase wakefulness in people with narcolepsy and shift work disorder • methylphenidate (Concerta, Ritalin) and amphetamine plus dextroamphetamine (Adderall), drugs used to treat attention deficit hyperactivity disorder (ADHD) • aspirin, perhaps because of an effect on quieting the autoimmune attack on the brain and spinal cord that is at the heart of MS • resistance training (strength training), especially if you continue to increase the challenge over time by either increasing the weight you use or by doing more repetitions of each exercise—or both • mindfulness training, which helps people with MS focus in a nonjudgmental way on their moment-tomoment experience (see “Practicing mindfulness in daily life,” page 21). The over-the-counter supplement acetyl-L-carnitine has been proposed as a treatment for the fatigue of MS, but there are limited data on it as yet. In one small study, carnitine at a dose of 2 grams daily was better tolerated and more effective than amantadine in reducing fatigue in people with MS.

Traumatic brain injury

Traumatic brain injury (TBI) has become a prominent concern over the past few years as more and more military personnel have returned from Iraq and Afghanistan with explosion-related injuries. In addition, many football players, boxers, and other athletes suffer concussions, which if not properly treated can have longw w w.h ealt h .ha r va r d.e du

lasting, devastating consequences affecting a wide range of cognitive, physical, and psychological functions. The CDC defines TBI as a “bump, blow, or jolt to the head or a penetrating head injury that disrupts the normal function of the brain.” This can occur as a result of a car accident, an assault, or a fall (the most common cause of TBI in adults over the age of 60), as well as from injuries sustained during military combat and sports activities (see Figure 8, below). According to the CDC, visits to hospital emergency departments for TBI rose by 70% from 2001 to 2010. In 2010, approximately 2.5 million emergency visits, hospitalizations, and deaths in the United States were associated with TBI alone or in combination with other injuries.

How TBI affects energy Fatigue and lethargy are cardinal symptoms of TBI. How and why TBI leads to fatigue is unclear, however. One possibility is that the brain injury activates the immune system to repair the injury. This, in turn leads to the production of immune system chemicals called cytokines that can damage the brain.

Figure 8: L eading causes of traumatic brain injury









Source: CDC.

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How do you know you have TBI? Depending on the degree of the assault on the brain, TBI can be mild, moderate, or severe in intensity. Mild TBI. A concussion is the most common form of mild TBI (and the most common type of TBI over all). Symptoms can include a brief loss of consciousness; a headache; confusion; issues with memory, thinking, and concentration; lightheadedness; dizziness; blurred vision; ringing in the ears; a bad taste in the mouth; and changes in mood or behavior. Moderate or severe TBI. In addition to the symptoms listed above, more severe TBI may result in a headache that persists, repeated episodes of nausea and vomiting, seizures, coma, dilation of the pupils, loss of coordination, restlessness and agitation, weakness or numbness in the arms and legs, and slurred speech. Long-term consequences span a range of cognitive, behavioral, and psychological issues. Some individuals with severe injuries may live with little functional ability; some persist in a coma or nonresponsive vegetative state.

Treating TBI Any head injury should be examined immediately by a health professional, who may order imaging tests such as x-rays and CT scans. Even though treatment can’t reverse the brain damage caused by the injury, it is often possible to prevent further damage. Medical interventions include administering oxygen and controlling blood pressure with medications. People with severe TBIs that result in ruptured blood vessels (hematomas), bruising of the brain tissue, or swelling in the brain often need surgery. Physical, occupational, and speech therapy as well as counseling are often used to rehabilitate individuals with TBI.

Other neurological conditions

Fatigue can be an important problem with several other neurological conditions besides MS and TBI: Parkinson’s disease, strokes, amyotrophic lateral sclerosis (ALS, also called Lou Gehrig’s disease), myasthenia gravis, autoimmune neuropathies, muscular dystrophy, and postpolio syndrome. In these diseases, Boosting Your Energy


as in MS, the fatigue can be out of proportion to what would be expected to result from the neurological symptoms (such as paralysis and uncoordinated movements). The causes of fatigue in these neurological conditions has not been determined.

Other medical conditions

Fatigue is a symptom of numerous illnesses, from minor infections such as colds to serious diseases such as cancer and heart disease. It is a primary symptom of the illnesses discussed below. Some of these disorders cause fatigue directly, by sapping the body’s energy supply; others do so indirectly, as the immune system attempts to fight off the illness. Either way, once you get treatment or the infection subsides, your energy level should rebound.

Anemia Anemia is a condition in which the blood has too few red blood cells and, thus, low levels of hemoglobin, the protein inside red blood cells that delivers oxygen to tissues throughout the body. Anemia can lead to fatigue because the cells of your body need oxygen both to create ATP and to liberate energy stored as ATP. A shortage of oxygen can therefore mean a shortage of energy. Anemia is a common condition, especially among women, and is most often caused by iron deficiency. But iron-deficiency anemia typically does not cause fatigue unless it’s severe. Another form of anemia, known as pernicious anemia, results from a deficiency in vitamin B12; this causes the bone marrow to produce red blood cells that are larger and shorter-lived than normal red blood cells, thereby reducing the number of oxygen-carrying cells. Diagnosis. Anemia is easily diagnosed with a blood test. Treatment. For most types of anemia, there are effective treatments. For example, anemia caused by a deficiency in iron or vitamin B12 can be cured with supplements of those nutrients. Generally, supplements are taken orally, but if your deficiency stems from your stomach’s inability to absorb vitamin B12, that vitamin can be given by injection. Whether it’s 48

Boosting Your Energy 

from iron deficiency or vitamin B12 deficiency, the anemia and your fatigue should lift within three to six weeks after beginning supplements. Low levels of vitamin B12 that are not low enough to cause anemia can still cause depression, mood swings, and cognitive problems. If your blood level is close to or below the lower limit of normal, you might benefit from treatment with 100 micrograms (mcg) of vitamin B12 a day. People who are grossly deficient in the vitamin may need a larger initial dose given by an injection.

Cancer Many different types of cancer can cause loss of appetite and energy, even before the cancer causes other symptoms. Most likely, the fatigue is a result of increased levels of cytokines—chemicals made when the immune system is fighting an infection or a cancer. While the chance of cancer is fortunately small in a person with a recent loss of appetite and energy, it is likely enough to warrant a visit to your doctor about it. This is particularly true if you have lost weight without trying or if you have other worrisome symptoms such as unexplained fevers, new pain someplace in your body, unusual lumps in your breast or testicles, or swelling of the lymph nodes in your neck, under your arms, or in your groin. Fatigue is also one of the most common side effects of both chemotherapy and radiation treatments for cancer. The fatigue can range in severity from mild to moderate to totally debilitating, and it typically worsens toward the end of a treatment cycle as the drugs or radiation accumulates in the body. For some people, it can be so bad that it interferes with their ability to work and participate in their usual activities. Treatment. A number of nondrug therapies can help combat cancer-related fatigue. These include yoga and mindfulness-based techniques for stress and pain relief. You’ll also want to conserve your energy by limiting your activities, asking for help from your family and friends, and scheduling rest time. However, limiting your activities doesn’t mean cutting out exercise. Research shows that staying physically fit and eating well can improve vitality and quality of life after cancer treatment. Be sure to tell your health care prow w w.h ealt h .ha r va r d.e du

viders that you’re experiencing fatigue—they can often help you manage it, particularly if you’re having trouble sleeping. Treatment-related fatigue often resolves gradually after chemotherapy and radiation end.

Chronic infections Unlike acute infections such as a cold or flu, which go away in a week or two, chronic infections can last for months or years. During that time, the body expends large amounts of energy trying to overcome the infection, which can leave a person feeling lethargic and weak. The immune system mounts an attack on the infection by unleashing a group of chemicals called cytokines. The cytokines are known to cause exhaustion, possibly by increasing the production of stress hormones. Chronic infections that cause particularly severe fatigue include tuberculosis, Lyme disease, and any form of hepatitis. Treatment. Each of these illnesses has effective therapies, and once treated, most people find that their energy level improves. However, a small fraction of people with Lyme disease who receive prompt diagnosis and adequate treatment nevertheless continue to experience debilitating fatigue for months or years afterward. Some doctors prescribe long-term antibiotics for these patients, on the theory that the bacteria that cause Lyme disease may not have been eradicated by the initial treatment. However, recent studies have cast doubt on that theory.

Heart failure Heart failure occurs when the heart is unable to pump enough blood to meet the body’s needs. Insufficient blood flow through the brain, kidneys, and muscles can cause weakness and fatigue. Compounding the problem, the failing heart works extra hard to pump blood, using up more than its share of energy. Diagnosis. Your doctor can detect heart failure through a physical examination and diagnostic tests, such as an electrocardiogram (ECG) or chest x-ray. Treatment. The disease can be controlled by a combination of appropriate medications and lifestyle changes, such as avoiding salty foods. Depending on the person’s age and the severity of the condition, treatment can, to some degree, relieve the fatigue. ww w. h ealt h . h ar v ar d . e du

Hypothyroidism This condition occurs when the thyroid gland does not produce enough thyroid hormone. If you have hypothyroidism, you may feel lethargic because your metabolism (the breakdown of food for energy) slows down. Almost 10 million people in the United States have hypothyroidism. The condition becomes increasingly common with age, and it’s more common in women than in men. Women are five times more likely than men to experience hypothyroidism, according to the American Association of Clinical Endocrinologists. Hypothyroidism has several causes. The most common is Hashimoto’s thyroiditis, an autoimmune disease in which the immune system attacks the cells of the thyroid, causing inflammation and cell destruction. Interestingly, particularly in people over age 60, too much thyroid hormone (a condition called hyperthyroidism) also can produce fatigue—along with jitteriness and weight loss despite a good appetite. This condition, called “apathetic hyperthyroidism,” is often overlooked by doctors. Diagnosis. Thyroid disorders can be diagnosed with blood tests that measure your levels of various thyroid hormones. The most commonly measured of these is thyroid-stimulating hormone (TSH). Treatment. Hypothyroidism usually is treated with thyroid hormone replacement, which provides synthetic versions of natural thyroid hormones. When the dose has been adjusted properly, thyroid hormone replacement is successful and energy levels are restored. If an overactive thyroid is causing your fatigue, your hyperthyroidism can be treated in one of three ways—by using medication to block your thyroid’s hormone production, taking radioactive iodine to destroy part of the thyroid, or having surgery to remove all or part of the gland (thyroidectomy).

Diabetes Blood sugar (glucose) provides energy to cells, but first it must get inside the cells to be converted to a usable energy form. The pancreas makes insulin, the hormone that helps transport sugar into cells. In type 1 diabetes, the pancreas doesn’t make enough insulin. Boosting Your Energy


In type 2 diabetes, the pancreas initially makes more than enough insulin, but the cells are resistant to it. In either type of diabetes, not enough sugar gets into the cells, impairing their ability to generate energy. Lack of physical and mental energy is among the many symptoms of diabetes. Diagnosis. Diabetes can be diagnosed with a blood test that measures levels of glucose in the blood. Treatment. Although there’s no cure, a variety of treatments can help control diabetes, including medications that supply added insulin or increase the body’s insulin sensitivity, and lifestyle changes, particularly exercise and weight loss. A 2015 study found that after 12 weeks of combined aerobic and resistance exercise (consisting of three weekly 60-minute sessions), adults with type 2 diabetes had greater muscle strength and endurance, more vitality, and improved mental health.

Kidney disease Various diseases that damage the kidneys may indirectly cause fatigue by reducing production of erythropoietin (EPO), a hormone that stimulates the bone marrow to make and release red blood cells. The kidneys produce most EPO in your body, so if kidney function is impaired, you could develop anemia and the accompanying fatigue. Diagnosis. Your doctor can diagnose most kidney diseases with simple blood and urine tests. Treatment. In many cases, your fatigue will be remedied once the underlying kidney problem is treated. If you have chronic kidney disease, the first step in treating anemia is usually iron supplements, which enable the EPO you produce naturally to promote production of red blood cells. If this is not sufficient to keep your hemoglobin levels normal, you may be eligible for injections of a synthetic form of EPO. Particularly for people who are very anemic (such as those undergoing dialysis for kidney dysfunction), an analysis of multiple studies published in 2012 confirmed that injections of EPO increase hemoglobin levels and improve fatigue. Talk with your doctor about which options are best for you.


Boosting Your Energy 

Mitochondrial disorders Mitochondria produce ATP, the energy molecules that power all of the chemical reactions inside a cell. There are rare diseases of the mitochondria that produce many severe symptoms, including brain and muscle fatigue. Recent research has revealed that more subtle abnormalities of the mitochondria may also be important in many major diseases and may produce brain and muscle fatigue. How commonly such subtle mitochondrial abnormalities cause fatigue, and what treatments might counteract these abnormalities, are areas of active research.

In conclusion

In many ways, life in the 21st century has become less exhausting. Certainly, most jobs have become less physically demanding, as machines have replaced muscle power in one industry after another and more work has shifted to desk jobs. At home, labor-saving devices, such as washing machines, dishwashers, and snow blowers, have helped to lighten the load. And motorized vehicles allow us to travel with a minimum of exertion. At the same time, the pace of life has sped up. There is more to think about, more to worry about, more to do, more multitasking that pulls us in several directions at once. This is more exhausting. And the lack of exercise from all that time spent sitting also saps energy. Paradoxically, the many conveniences of modern life can thus conspire to drain energy rather than boost it, if you’re not aware of what’s going on and do not take the steps outlined in this report to counteract the problem. For some people, however, finding the energy they lack involves the diagnosis and treatment of a disease. As you can see from this report, a great many conditions may contribute. Whatever constellation of causes is responsible for your fatigue, we hope you have found strategies in this report to help restore your energy and reclaim your life. With dedication and persistence, a few simple steps may be all it takes. 

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Resources Organizations American Horticultural Therapy Association 610 Freedom Business Center, #110 King of Prussia, PA 19406 610-992-0022 This nonprofit organization is devoted to the practice and development of horticultural therapy. The website offers information about the benefits of gardening and spending time in green spaces, events, and guidance on how to become a certified horticultural therapist.

American Lyme Disease Foundation P.O. Box 466 Lyme, CT 06371 This private organization offers reputable information on the prevention and treatment of Lyme disease and other tick-borne infections.

Brain Injury Association of America, Inc. 1608 Spring Hill Road, Suite 110 Vienna, VA 22182 800-444-6443 or 703-761-0750 This advocacy group seeks to boost awareness of how to prevent traumatic brain injuries, and advance research, treatment, and education. The website provides access to a network of state affiliates, local chapters, and support groups, as well as information on living with a brain injury.

Brain Trauma Foundation 1 Broadway, 6th Floor New York, NY 10004 212-772-0608 This foundation is devoted to clinical research and developing and refining practice guidelines for traumatic brain injuries. On the website, consumers can find educational articles on traumatic brain injury and myths and facts about concussion.

Caregiver Action Network 11300 Connecticut Ave. NW, Suite 300 Washington, DC 20036 202-454-3970 The leading family caregiver organization, formerly known as the National Family Caregivers Association, offers information to a broad spectrum of the more than 65 million Americans who are caring for loved ones. The nonprofit organization is free to join and offers many educational resources on caregiving topics, online forums, and peer support.

Centers for Disease Control and Prevention (CDC) 1600 Clifton Road Atlanta, GA 30333

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800-232-4636 (toll-free) The portion of the CDC’s website devoted to chronic fatigue syndrome includes information about diagnosis and treatment, help with finding support groups, updates on research, and summaries of peer-reviewed articles on chronic fatigue syndrome by experts in the field.

National Fibromyalgia Association 1000 Bristol St. N, Suite 17-247 Newport Beach, CA 92660 This nonprofit advocacy group for people with fibromyalgia and other chronic pain disorders sponsors National Fibromyalagia Awareness Day (May 12 annually) and provides consumers with information on the condition through conferences, published materials such as Fibromyalgia AWARE magazine, and its website.

National Fibromyalgia Research Association P.O. Box 500 Salem, OR 97308 503-315-7257 This nonprofit activist organization provides news and information about fibromyalgia, including updates on scientific research, links to patient organizations, and suggested books and other resources.

National Multiple Sclerosis Society 773 3rd Ave., 3rd Floor New York, NY 10017 800-344-4867 (toll-free) This nonprofit group provides the latest research information on MS, support groups and activities in its 50 state chapters and online, and resources for coping with MS.

National Sleep Foundation 1010 N. Glebe Road, Suite 310 Arlington, VA 22201 703-243-1697 This foundation conducts research on sleep and sleep disorders and provides information on a wide variety of sleep topics, including issues related to menopause. The website features an interactive sleep diary, as well as links to sleep centers by state.

Solve ME/CFS Initiative 5455 Wilshire Blvd., Suite 806 Los Angeles, CA 90036 704-364-0016 This association offers information about symptoms, diagnosis, and therapies for chronic fatigue syndrome, as well as advice on insurance, workplace issues, and related legal matters. The website provides a reading list and a listing of support groups by state.

Boosting Your Energy


Resources  continued Special Health Reports The following Special Health Reports from Harvard Medical School elaborate on some of the topics covered in this report. To order, go to or call 877-649-9457 (toll-free).

The Harvard Medical School 6-Week Plan for Healthy Eating Teresa Fung, R.D., Faculty Editor, and Kathy McManus, M.S., R.D., Nutrition Editor (Harvard Medical School, 2015) It’s not easy to overcome such ingrained habits as diet. But this step-by-step plan helps you transition to a healthy diet by making just a few changes each week.

Improving Sleep: A guide to a good night’s rest Lawrence Epstein, M.D., Medical Editor (Harvard Medical School, 2015) This report provides an authoritative discussion of the complex factors that can interfere with a good night’s sleep and lead to daytime fatigue. It also offers practical suggestions for improving sleep.

Starting to Exercise Lauren E. Elson, M.D., Medical Editor, and Michele Stanten, Fitness Consultant (Harvard Medical School, 2015)


Boosting Your Energy 

This step-by-step guide describes how to start and maintain an exercise program if you’ve been inactive for any reason, whether you’ve had an illness or simply let exercise lapse because of time pressures or family obligations. You’ll find advice on being a savvy consumer when it comes to fitness products, as well as useful tools and tips designed to help make exercise work for you.

Stress Management: Techniques for preventing and easing stress Gregory L. Fricchione, M.D., Medical Editor (Harvard Medical School, 2016) This report teaches you how to identify triggers for stress and explains the ways in which stress affects your body. It also provides step-by-step instructions for a variety of stress control techniques, including meditation, progressive muscle relaxation, breathing exercises, cognitive restructuring, and guided imagery. Understanding Depression Michael Craig Miller, M.D., Medical Editor (Harvard Medical School, 2016) This report provides comprehensive, in-depth information on one of the main causes of fatigue. It includes the latest findings on the underlying biology of depression and the most effective treatments.

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Glossary adenosine triphosphate (ATP): The molecule that carries energy for all cells.

insulin: The hormone that carries glucose from the blood into the cells.

anemia: A decline in the number of red blood cells or the amount of hemoglobin in the blood, which lowers the oxygen-carrying capacity of the blood.

melatonin: A hormone that induces drowsiness, produced by the pineal gland as daylight turns to darkness.

central (brain) fatigue: A lack of concentration or alertness as well as a sense of lethargy and loss of motivation; involves the central nervous system. chronic fatigue syndrome (CFS): A disorder characterized by at least six months of fatigue, together with impaired concentration or memory and other symptoms. circadian cycle: The biological clock that regulates sleep and waking and that controls the daily ups and downs of physiologic patterns, including body temperature, blood pressure, and the release of hormones.

mitochondria: Small, threadlike structures within the cell’s cytoplasm where ATP, the energy molecule, is made; often called the body’s energy factories. multiple sclerosis (MS): An autoimmune disease in which the body’s immune system mistakenly attacks myelin, the substance that covers nerve fibers. muscle fatigue: Weakness you feel in your muscles when you’ve tired them out. non-REM sleep: The type of sleep that includes deep sleep, the period considered most important for preventing daytime fatigue.

fatigue: A decrease in the ability to perform a physical or mental task. It includes muscle fatigue as well as central fatigue, which originates in the central nervous system and influences the perception of fatigue.

pineal gland: A gland located in the middle of the brain, between the brain’s two hemispheres, that produces melatonin in response to declining light.

fibromyalgia: A disorder characterized by pain and tenderness in muscles and joints, as well as by fatigue. Similar in many respects to chronic fatigue syndrome.

REM (rapid eye movement) sleep: A period of intense brain activity during sleep, often associated with dreams. It is named for the rapid eye movements that occur during this time.

glucose: A simple sugar that circulates in the bloodstream and serves as a source of energy for cell metabolism. It’s formed mainly by the digestion of carbohydrates.

sleep apnea: A sleep disorder in which a person repeatedly stops breathing momentarily during sleep. This often causes daytime drowsiness.

glycemic load: A measure of how much a particular food will raise your blood sugar. It takes into account both how much sugar is contained in a serving of the food and how quickly that sugar is absorbed into your bloodstream.

stimulant: A substance, such as caffeine, contained in some foods or beverages that speeds up chemical reactions inside cells and provides a boost of energy.

heart failure: A disorder that occurs when the heart is unable to pump enough blood to meet the body’s needs. Insufficient blood flow can cause weakness and fatigue. hormones: Chemicals, produced by glands, that are responsible for regulating a wide variety of physical functions. Many can influence energy level. hypothalamus: The part of the brain that controls the autonomic nervous system and that regulates sleep, appetite, body temperature, and other biological states. insomnia: The inability to fall asleep or remain asleep long enough to feel rested.

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stress: An innate survival response in which certain hormones are released, increasing blood flow to the brain or heart. The stress response leads to an energy surge, enabling a person to flee dangerous situations. Ongoing stress, however, can sap energy and damage health. suprachiasmatic nucleus: A small group of nerve cells, located in the hypothalamus, that controls the sleep/wake cycle and functions as the body’s internal clock. traumatic brain injury: Injury to the head that disrupts normal brain functioning. The injury can be superficial or penetrating, and can result from a car accident, an assault, a fall, an explosive blast, or sports activities.

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