we never evolved to exercise.
exercise today is most commonly defined as voluntary physical activity undertaken for the sake of health and fitness.
[in the old days] no one ever ran or walked several miles just for health.
how would I explain to a hunter-gatherer, a farmer in Pemja, or even my great-great-great-grandparents that I spend most of my days sitting in chairs and then compensate for my idleness by paying money to go to a gym to make myself sweaty, tired, and uncomfortable on a machine that forces me to struggle to stay in the same place?
many of our beliefs and attitudes about exercise are myths. Chief among these myths is the notion that we are supposed to want to exercise.
If exercise, as we are told, is really a “magic pill” that will cure or prevent most diseases, why are more people living longer than ever despite being more physically inactive than ever?
nothing about the biology of exercise makes sense except in the light of evolution, and nothing about exercise as a behavior makes sense except in the light of anthropology.
the myth of the athletic savage. The essential premise of this myth is that people like the Tarahumara whose bodies are untainted by modern decadent lifestyles are natural superathletes, not only capable of amazing physical feats, but also free from laziness. By contending that the men I observed running seventy miles
without training do so naturally, this myth implies that people like you and me who neither can nor will accomplish such feats are, from an evolutionary perspective, abnormal because civilization has turned us into etiolated wimps. As you have probably divined, I object to the myth of the athletic savage. For one, it stereotypes and dehumanizes people such as the Tarahumara. Since that first trip when I spoke with Ernesto, I have talked with hundreds of Tarahumara all over the Sierra Tarahumara and can assure you no one there wakes up in the morning and thinks, “Gee, what a beautiful day. I think I’ll run fifty miles just for fun.” They don’t even go for needless five-mile runs. When I ask Tarahumara on what occasions they run, the most common answer is “when I chase goats.” Instead, I have come to appreciate that the Tarahumara are extremely hardworking, physically fit farmers who never do anything by half and whose culture deeply values running. The reason some Tarahumara run fifty or more miles on rare occasions is not much different from the reason Ironmen do triathlons: they think it is worth it. However, whereas Ironmen subject themselves to full triathlons to test their limits (Anything Is Possible!), Tarahumara run rarájiparis because it is a deeply spiritual ceremony that they consider a powerful form of prayer.
The myth of the athletic savage mistakenly suggests that humans uncorrupted by civilization can easily run ultramarathons, scale enormous mountains, and perform other seemingly superhuman feats without training.
In other words, the training that enables them to run back-to-back marathons is the physical work that is part and parcel of their everyday life.
In other words, typical hunter-gatherers are about as physically active as Americans or Europeans who include about an hour of exercise in their daily routine.
we walk less, drive more, and use countless energy-saving devices from shopping carts to elevators that whittle away, calorie by calorie, at how much physical activity we do. The problem, of course, is that physical activity helps slow aging and promotes fitness and health. So those of us who no longer engage in physical labor to survive must now weirdly choose to engage in unnecessary physical activity for the sake of health and fitness. In other words, exercise.
First, while youngsters have always played and sports are a human universal, exercise outside the context of sports was extremely rare until relatively recently. Second, as recent technological and social developments have diminished industrialized people’s need to be physically active, a growing chorus of experts has never ceased to raise the alarm that we aren’t exercising enough.
“there never was a time in the history of the world when the great mass of mankind could meet the simple exigencies of life with so little expenditure of time and energy as today,” and that “without solid physical education programs, people would become fat, deformed, and clumsy.”
Just as we put wheels in cages for mice in labs, over the centuries we have invented a stunning variety of ways and means for our fellow humans to undertake optional physical activity for the sake of health and fitness.
Unsurprisingly, exercise has become increasingly advertised as virtuous and has been commodified, commercialized, and industrialized. To use the weight machines, treadmills, ellipticals, and other contraptions in the gym around the corner from my house costs seventy dollars per month. When I head out for a morning run, I wear specialized running shoes, chafe-preventing shorts, a snazzy moisture-wicking shirt, a washable cap, and an expensive watch that connects to satellites overhead to track my speed and distance. Oscar Wilde once quipped, “I approve of any activity that requires the wearing of special clothing,” but I suspect even he would be shocked at the popularity of “athleisure”—workout clothes for everyday activities like sitting that help us look athletic without ever having to break a sweat. Worldwide, people spend trillions of dollars a year on fitness and sportswear.
What would my distant hunter-gatherer ancestors have thought of paying lots of money to suffer through needless physical activity on an annoying machine that gets us nowhere and accomplishes nothing?
MYTH #2 It Is Unnatural to Be Indolent
To be more precise, we’d ask you to drink some very expensive, harmless water that contains a known quantity of rare (heavy) hydrogen and oxygen atoms and then collect samples of your urine over the next few days. This sounds like a creepy magic trick, but by measuring the rate at which these heavy atoms become less abundant in urine, we can calculate the rates at which both the hydrogen and the oxygen atoms leave the body from sweating, urinating, and breathing. Because hydrogen exits the body only in water but oxygen leaves in both water and carbon dioxide, the difference in the concentration of these two atoms in urine allows us to compute exactly how much carbon dioxide someone produced from breathing, hence how much energy he or she used.
even if you are a highly active person, you probably spend more energy maintaining your body than doing stuff. Understandably, this fact seems counterintuitive. As I sit here writing these words, there is little visible evidence that every one of my body’s systems is working industriously to keep me alive apart from the fifteen to twenty gentle breaths I take every minute. Yet my heart is contracting sixty times a minute to pump blood to every corner of my body, my intestines are digesting my last meal, my liver and kidneys are regulating and filtering my blood, my fingernails are growing, my brain is processing these words, and countless other cells in every tissue of my body are busily replenishing themselves, repairing damage, fending off infection, and monitoring what’s going on.
The key lesson to digest from the starving men’s dramatically lower resting metabolic rates is that human resting metabolisms are flexible. Most critically, resting metabolism is what the body has opted to spend on maintenance, not what it needs to spend.
Stated simply, we evolved to be as inactive as possible. Or to be more precise, our bodies were selected to spend enough but not too much energy on nonreproductive functions including physical activity.
ancient, fundamental strategy to allocate scarce energy sensibly. Apart from youthful tendencies to play and other social reasons (topics for later chapters), the instinct to avoid nonessential physical activity has been a pragmatic adaptation for millions of generations.
But then I wondered if I was being one of those annoying exercists who nags people (in this case myself) to sneak in more physical activity by parking at the back of the lot. How did something as normal and instinctive as saving energy become associated with the sin of slothfulness?
To early Christian thinkers like Thomas Aquinas, sloth had nothing to do with physical laziness, but instead was a sort of mental apathy, a lack of interest in the world. By this definition, sloth is sinful by causing us to neglect the pursuit of God’s work. It was only later that sloth came to mean the avoidance of physical work, perhaps because almost no one back then, apart from a few elites, could avoid regular physical labor.
So let’s banish the myth that resting, relaxing, taking it easy, or whatever you want to call inactivity is an unnatural, indolent absence of physical activity.
MYTH #3 Sitting Is Intrinsically Unhealthy
Technically, “inflammation” describes how the immune system first reacts after it detects a harmful pathogen, something noxious, or a damaged tissue. In most cases, inflammation is rapid and vigorous. Whether the offenders are viruses, bacteria, or sunburns, the immune system quickly launches an armada of cells into battle. These cells discharge a barrage of compounds that cause blood vessels to dilate and become more permeable to white blood cells that swoop in to destroy any invaders. This extra blood flow brings critically needed immune cells and fluids, but the swelling compresses nerves and causes the four cardinal symptoms of inflammation (which literally means “to set on fire”): redness, heat, swelling, and pain.
As scientists started to study when and how cytokines turn inflammation on and off, they discovered that some of the same cytokines that ignite short-lived, intense, and local inflammatory responses following an infection also stimulate lasting, barely detectable levels of inflammation throughout the body. Instead of blazing acutely in one spot for a few days or weeks, as when we fight a cold, inflammation can smolder imperceptibly in many parts of the body for months or years. In a way, chronic, low-grade inflammation is like having a never-ending cold so mild you never notice its existence.
The mechanisms by which too much fat, especially in and around organs, can ignite low-grade, chronic inflammation suggest that too much sitting may be hazardous simply because it causes weight gain.
the hormone cortisol. This much-misunderstood hormone doesn’t cause stress but instead is produced when we are stressed, and it evolved to help us cope with threatening situations by making energy available.
Cortisol shunts sugar and fats into the bloodstream, it makes us crave sugar-rich and fat-rich foods, and it directs us to store organ fat rather than subcutaneous fat.
Consequently, long hours of stressful sitting while commuting or a high-pressure office job can be a double whammy.
muscles regulate inflammation during bouts of moderate to intense physical activity similarly to the way the immune system mounts an inflammatory response to an infection or a wound.
If I gulp down four cups of coffee all at once, I’ll become jittery and get a headache, but if I drink them over the course of a day, I’ll be fine. Is the same true for sitting? Additionally, does a daily bout of hard exercise negate the effects of sitting for the rest of the day?
Even those who engaged in more than seven hours per week of moderate or vigorous exercise had a 50 percent higher risk of dying from cardiovascular disease if they otherwise sat a lot.
Altogether, these and other alarming studies suggest that even if you are physically active and fit, the more time you spend sitting in a chair, the higher your risk of chronic illnesses linked to inflammation, including some forms of cancer. If these results are correct, then exercise alone doesn’t counter all the negative effects of sitting.
These activities aren’t serious exercise, but experiments that ask people to interrupt long periods of sitting even briefly—for example, just a hundred seconds every half hour—result in lower levels of sugar, fat, and so-called bad cholesterol in their blood. In turn, less circulating blood sugar and fat prevent inflammation as well as obesity. In addition, small and occasional bouts of moving stimulate muscles to
quench inflammation and reduce physiological stress.
For this reason, squatting and other more active forms of sitting may be healthier than sitting in chairs by requiring intermittent muscle activity, especially in the calves, thus recirculating blood in the legs.
Another way to sit actively is to fidget, or do what researchers drily term “spontaneous physical activity.”
that simply fidgeting while seated can expend as much as twenty calories an hour as well as promote beneficial levels of blood flow to restless arms and legs. One study even found a 30 percent lower rate of all-cause mortality among people who fidget after adjusting for other forms of physical activity, smoking, diet, and alcohol consumption.
Standing is not exercise, and as yet no well-designed, careful study has shown that standing desks confer substantial health benefits.
One massive fifteen-year-long study of more than ten thousand Danes found no association between time spent sitting at work and heart disease.
An even bigger study on sixty-six thousand middle-aged Japanese office
workers yielded similar results. Instead, leisure-time sitting best predicts mortality, suggesting that socioeconomic status and exercise habits in mornings, evenings, and weekends have important health effects beyond how much one sits during weekdays at the office.
Sleep: Why Stress Thwarts Rest
I sometimes experience this phenomenon when I stay up late trying to comprehend complex information (like how sleep affects the brain). As the night progresses, my brain becomes increasingly muddled, and eventually I give up and go to bed. But then in the morning, almost miraculously, everything seems to make sense. What happened while I was asleep?
For every hour spent awake storing memories and amassing waste, we need approximately fifteen minutes asleep to process those memories and clean up. That ratio, however, is highly variable: some people like the elderly sleep less, while others, especially children, need more.
College students are a special breed of humans, in part because so many of them are enjoying their first taste of being grown up without yet shouldering the responsibilities of being adults.
“In twenty years, people will look back on the sleeping-pill era as we now look back on the acceptance of cigarette smoking.”
We label sitting as bad and sleeping as good. In truth, both ways of resting are utterly normal but highly variable behaviors with complex costs and benefits that are strongly influenced by our environment and contemporary cultural norms.
It bears repeating that sleep and physical activity are inextricably linked: the more physically active we are, the better we sleep because physical activity builds up sleep pressure and reduces chronic stress, hence insomnia. In that sense, physical activity and sleep are not trade-offs but collaborators. Maybe it is not so paradoxical that the same well-intentioned people who nag us to exercise sometimes also badger us to spend more time in bed.
Wondering how lions could develop such strength without using weights, Angelo figured they must get strong by “pitting one muscle against another.” He started to experiment with what he called “dynamic tension,” which today we call isometric training.
When asked to do as many push-ups, pull-ups, and chin-ups as they could, the Aché were fit but similar to Westerners with one important difference: as they aged, their strength declined at lower rates, presumably reflecting how they stay physically active throughout the life span including middle age.
One potential drawback of bulking up too much is sacrificing power. Strength is how much force I can produce; power is how rapidly I produce it. Strength and power are not independent, but there is some trade-off between the two:
Indeed, aging does not put an end to muscles’ capacity to respond to resistance exercise; instead, modest levels of resistance exercise slow and sometimes reverse sarcopenia regardless of age they would probably be confused by how we spend money to needlessly lift things whose sole purpose is to be lifted.
Humans are endurance walkers.
“Walking on a regular basis—whether going for a brisk, structured walk, or just fitting in more steps every day—can help you shed pounds and inches and, most importantly, keep them off.”
MYTH #10 It’s Normal to Be Less Active as We Age
Hippocrates wrote twenty-five hundred years ago, “Eating alone will not make a man well; he must also take exercise.”
Endurance promotes endurance.
If exercise is so destructive, why is it healthy? One explanation is that once she stopped exercising, my wife’s body reacted by repairing whatever harm she caused and, crucially, also repairing some of the damage that she had accumulated beforehand when she wasn’t exercising. As a result, she restored many tissues to their previous state.
his advocacy of vitamin C was quackery. Dozens of studies have found that taking antioxidant pills is no substitute for physical activity to fight senescence. A comprehensive review published in examined sixty-eight clinical trials that compared the effects of commonly prescribed antioxidants like vitamin C with placebos on more than 230,000 people. Three or four studies reported a modest benefit, but the rest found that antioxidants provided no benefit or even increased the risk of dying.
This shift, in which more of us live longer but die from chronic rather than infectious diseases, thus extending morbidity, is known as the epidemiological transition and widely hailed as medical progress.
In 1984, he and his students began studying more than five hundred members of amateur running clubs along with more than four hundred healthy but physically inactive controls. Back then, the subjects were over the age of fifty and healthy: few smoked, none drank heavily, and none were obese. Then, for the next twenty-one years, Fries and his colleagues patiently kept track of each subject’s physical activity habits, administered a yearly disability questionnaire that measures functions like the ability to walk, dress, and do routine activities, and recorded the year and cause of every death that occurred. Fries and colleagues had to wait two decades for the results, but I have summarized them for you instantaneously in figure 29. They are worth a careful look. The top graph plots the runners’ and non-runners’ probability of not dying in a given year against time; the graph below plots disability against time. As you can see, the healthy non-runners died at increasingly faster rates than the runners and by the study’s end were about three times more likely to pass away in a given year. In terms of cause of death, the non-runners were more than twice as likely to die of heart disease, about twice as likely to die of cancers, and more than three times as likely to die of neurological diseases. In addition, they were more than ten times as likely to die of infections like pneumonia. Just as important, the disability scores plotted on the bottom show that the non-runners lost functional capacity at double the rate of the runners. By the end of the study their disability scores were more than twice as high as the runners’, indicating that the runners’ bodies were approximately fifteen years younger by this measure. In sum, running caused a compression of morbidity, thus also extending lives.
MYTH #11 “Just Do It” Works
“exercise is done against one’s wishes and maintained only because the alternative is worse.”
our bodies never evolved to function optimally without lifelong physical activity but our minds never evolved to get us moving unless it is necessary, pleasurable, or otherwise rewarding.
If we can’t make exercise necessary and fun, perhaps we can make it more necessary and more fun.
I think there is a deeper evolutionary explanation for why almost every book, website, article, and podcast on how to encourage exercise advises doing it in a group. Humans are intensely social creatures, and more than any other species we cooperate with unrelated strangers. We used to hunt and gather together, and we still share food, shelter, and other resources, we help raise one another’s children, we fight together, we play together. As a result, we have been selected to enjoy doing activities in groups, to assist one another, and to care what others think of us. 15 Physical activities like exercise are no exception.
Dopamine. This molecule is the linchpin of the brain’s reward system. It tells a region deep in the brain “do that again.” First, dopamine levels go up only while we exercise. So they don’t get us off the couch. Worse, dopamine receptors in the brain are less active in people who haven’t been exercising than in fit people who are regularly active. And to add insult to injury, people who are obese have fewer active dopamine receptors.
Serotonin. This still mysterious neurotransmitter helps us feel pleasure and control impulses, but it also affects memory, sleep, and other functions. Our brains produce serotonin when we engage in beneficial behaviors like having physical contact with loved ones, taking care of infants, spending time outdoors in natural light, and, yes, exercising.
Although some people with depression take pharmaceuticals to maintain normal serotonin function, exercise has been shown to be often as effective as any prescription.
Endorphins. Endorphins are natural opioids that help us tolerate the discomfort of exertion. The body’s own opioids are less strong than heroin, codeine, and morphine, but they too blunt pain and produce feelings of euphoria.
endorphins aren’t produced until after twenty or more minutes of intense, vigorous activity, making them more rewarding for people who are already fit enough to work out that hard.
Endocannabinoids. For years, endorphins were thought to cause the infamous runner’s high, but it is now evident that endocannabinoids—the body’s natural version of marijuana’s active ingredient—play a much greater role in this phenomenon. 24 Despite causing a truly pleasurable high, this system has little relevance for most exercisers because it usually takes several hours of vigorous physical activity before the brain releases these mood-and sensory-enhancing drugs.
While these and other chemicals released by exercise help us exercise, their drawback is they mostly function through virtuous cycles. When we do something like walk or run six miles, we produce dopamine, serotonin, and other chemicals that make us feel good and more likely to do it again. When we are sedentary, however, a vicious cycle ensues. As we become more out of shape, our brains become less able to reward us for exercising. It’s a classic mismatch: because few of our ancestors were physically inactive and unfit, the brain’s hedonic response to exercise never evolved to work well in persistently sedentary individuals.
Commonly recommended, sensible methods to make exercise more fun (or less unfun) include: Be social: exercise with friends, a group, or a good, qualified trainer. 27 Entertain yourself: listen to music, podcasts, or books, or watch a movie. Exercise outside in a beautiful environment. Dance or play sports and games. Because variety is enjoyable, experiment and mix things up. Choose realistic goals based on time, not performance, so you don’t set yourself up for disappointment. Reward yourself for exercising.
Because we never evolved to be inactive and out of shape, the adaptations that make physical activity feel rewarding and become a habit develop only after the several months of effort it takes to improve fitness. Slowly and gradually, exercise switches from being a negative feedback loop in which discomfort and lack of reward inhibit us from exercising again to being a positive feedback loop in which exercise becomes satisfying.
No matter what we do to make exercise more enjoyable, the prospect of exercising usually seems less desirable and less comfortable than staying put. Every time I plan to exercise, I first struggle to prevail over instincts to not exercise. Afterward, I never regret it, but to overcome my inertia, I usually have to figure out how to make it seem necessary.
From a purely utilitarian perspective, how is requiring exercise different from mandating seat belt use?
MYTH #12 There Is an Optimal Dose and Type of Exercise
All things are poison and nothing is without poison; only the dose permits something not to be poisonous.
Paffenbarger published many brilliant studies (including one contending that regular chocolate consumption adds nearly a year to your life3),
Middle-aged alumni who exercised more than two thousand calories per week had a 21 percent lower risk of dying than their sedentary classmates, and those who were over seventy and exercised the same amount had half the risk of dying in a given year as their inactive classmates. alumni who reported they exercised moderately or vigorously did better than their classmates who exercised only lightly. Finally, alumni who took up exercise later in life had similarly lower rates of mortality compared to those who had been active all along. It’s never too late to start.
By the 1990s, so many studies had accumulated that three major health organizations decided to convene expert panels to review the evidence and make recommendations. In 1995 and 1996, all three panels published essentially the same advice: to reduce the overall risk of chronic disease, adults should engage in at least 30 minutes of moderate-intensity exercise at least five times a week. 6 They also concluded that children should engage in 60 minutes of physical activity a day. the study further concluded that half an hour of vigorous exercise and an hour of moderate exercise confer the same benefit.
In the final analysis, exercising a minimum of 150 minutes per week is as good a prescription as any and hasthe advantage of being a clear, attainable dose. But there is no optimal, most beneficial dose of exercise.People who exercise the least have the most to gain from just modest added effort, more is better, and the benefits of additional exercise gradually tail off. “these findings reinforce the notion that light to moderate doses of exercise have a substantial positive impact on health but that continued dose escalation appears neither incrementally better nor worse.”
marathoners and ultramarathoners had higher rates of self-reported respiratory tract infections following their grueling races than fit individuals who exercised more moderately. 16 Additional studies found lower levels of disease-fighting white blood cells in the bloodstream and saliva immediately following intense bouts of vigorous exercise. These and other data led to the hypothesis that the energetic demands of extreme exercise create a temporary “open window” for infection.
That said, there is no question that anyone fighting a serious infection should avoid overexertion.
An experiment that gave mice a deadly form of influenza and then forced them to exercise before their symptoms developed found that low levels of moderate exercise (twenty to thirty minutes of daily running) doubled their rate of survival compared to sedentary mice, but extremely high levels of exercise (two and a half hours of running a day) caused them to die at even higher rates.
In the eighteenth century it was fashionable to lift church bells that were silenced (made “dumb”) by having their clappers removed, hence the term “dumbbells.”
Given that each of us is an “experiment of one” with different backgrounds, goals, and predilections that change with age, there can be no optimal mixture of exercise type any more than there can be an optimal amount.
Make exercise necessary and fun. Do mostly cardio, but also some weights. Some is better than none. Keep it up as you age.