Exercised Quotes

“It behooves us, however, to remember that exercise is a truly odd sort of medicine. It is largely medicinal because the absence of physical activity is unhealthy. Further, exercise not only is an abnormal behavior from an evolutionary perspective but also never evolved to be therapeutic. Instead, we evolved to spend energy—much more than our ape cousins do—on physical activity primarily out of necessity and for other social reasons and otherwise sensibly reserve scarce calories for the chief thing natural selection cares about: reproductive success. To use energy frugally, many of the genes that maintain our bodies thus depend on the stresses caused by being active.”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“For evidence that social commitment works, you have only to look at our most popular and durable social institutions that help us behave as we aspire: marriage, religion, and education. To varying degrees, all involve a public display of commitment to that institution and its principles in return for some benefit along with social support and censure. While marriage and religion are not good models, I think we should treat exercise more like education. For children, we already do. Just as we compel children to attend school, we require them to exercise (although rarely enough). As with school, we try to make exercise fun by making it social. So why not do the same for adults by treating exercise like college? Going to college is essentially a highly social commitment contract for adults that includes carrots and sticks. Students in my university pay a fortune to have professors like me compel them to read, study, and work under penalty of getting bad grades or failing. My students compete for and agree to these conditions because they know they would not learn as much without the school’s nudges, shoves, and requirements. In return, they enjoy a social experience that is usually fun, involves support from fellow students and staff, and encourages them to participate in something larger than themselves. Can this kind of commitment contract model help promote exercise, especially among youth?”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“Despite its utilitarian benefits, I oppose mandating universal exercise because adults have the right to make unhealthy decisions. The dilemma is that most people who struggle unsuccessfully to exercise also want to exercise.32 It’s not anyone’s fault that we inherited tendencies (some of us more than others33) to avoid unnecessary physical activity but were born to a world in which physical activity is no longer required and increasingly hard to do thanks to commuting, desk jobs, elevators, shopping carts, streets without sidewalks, buildings without easily accessible stairs, and so on. Instead of being shamed and blamed for being inactive, we deserve compassionate help to make exercise more necessary. The most acceptable way to do that is to find ways of coercing ourselves through agreed-upon nudges and shoves.”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“So, yes, exercise can become more rewarding and fun. But let’s not deceive ourselves or others. 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.”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“Exercise can also make us feel good, which helps make it enjoyable. After a good workout I feel simultaneously alert, euphoric, tranquil, and free from pain—not unlike taking an opioid. Actually, natural selection did adopt this drug-pushing strategy by having our brains manufacture an impressive cocktail of mood-altering pharmaceuticals in response to physical activity.16 The four most important of these endogenous drugs are dopamine, serotonin, endorphins, and endocannabinoids, but in a classic evolutionary design flaw these primarily reward people who are already physically active.”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“Like most organisms, we have been selected to enjoy and desire sex, eating, and other behaviors that benefit our reproductive success and to dislike behaviors like fasting that don’t help us have more babies. If our Stone Age ancestors found unnecessary physical activities like optional five-mile jogs unpleasant, they would have avoided squandering limited energy that could have been allocated toward reproduction. That may be a “just-so story,” but few would disagree that non-exercisers are not entirely irrational because exercise is a modern behavior that is by definition unnecessary and often unrewarding physically and emotionally. For many, it is also inconvenient and inaccessible. If we can’t make exercise necessary and fun, perhaps we can make it more necessary and more fun.”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“But didn’t we already know that? If there were an effective, dependable way to transform sedentary people into regular exercisers, it would spread like wildfire. Why aren’t any of these interventions more likely to succeed than our generally ill-fated New Year’s resolutions?”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“Imagine you are the CEO of a company with numerous sedentary employees and your health-care costs are escalating partly because of their inactivity, but unlike Henrik you don’t want to make exercise compulsory. Perhaps you are also a parent struggling to budge a surly, reluctant teenager to exercise. And maybe you have been striving unsuccessfully to get yourself off the couch more often. How do you succeed? Everyone copes with the urge to postpone or avoid exercise, so environments that neither require nor facilitate physical activity inevitably promote inactivity.5 If I have to choose between sitting comfortably in a chair or slogging through a sweaty workout, the chair is almost always more appealing. The slow, rational part of my brain knows I should exercise, but my instincts protest, “I would prefer not to,” and another, enticing voice queries, “Why not exercise tomorrow?”6 Perhaps I don’t have the time or energy, and I have to go out of my way to get physical activity because I am stressed for time, my town lacks sidewalks, or the stairway in my building is dingy and inaccessible. To add to these impediments, maybe I inherited genes that predispose me to being physically inactive. Scientists have bred laboratory mice that are instinctively addicted or averse to running on treadmills, and studies of humans suggest that some of us inherited tendencies to be slightly less inclined to exercise.7”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“Can an evolutionary anthropological approach help us do better? If we evolved to be physically active because it was either necessary or fun, then isn’t the solution to make exercise necessary and fun like my Ironstrength Workout? If only things were that simple. Because exercise is defined as voluntary physical activity, it is inherently unnecessary. And for many people, especially those who are unfit, exercise simply isn’t fun. That said, our social institutions try to accomplish these two goals for most youngsters. Throughout the world, recess, physical education, or sports are mandatory in some primary and secondary schools, and for some students these respites from the classroom are times to have fun.2 Adults, however, are different, and I know of only one place in the world—an unusual company in Stockholm, Sweden—that has attempted to make exercise utterly necessary and also fun for every adult employee. Curious and a little bit skeptical, I swung an invitation to the Björn Borg sportswear company to see for myself.”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“My reasons for exercising that morning accord totally with this book’s mantra that we never evolved to exercise—that is, do optional physical activity for the sake of health and fitness. I participated because I felt I had to and it was supposed to be fun. For generation after generation, our ancestors young and old woke up each morning thankful to be alive and with no choice but to spend several hours walking, digging, and doing other physical activities to survive to the next day. Sometimes they also played or danced for enjoyment and social reasons. Otherwise, they generally steered clear of nonessential physical activities that divert energy from the only thing evolution really cares about: reproduction. The resulting paradox is that 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. Plunk us down in a postindustrial world, and we struggle to replace physical activity with exercise—an optional and often disagreeable behavior. Despite being badgered to exercise by doctors, trainers, gym teachers, and others, we often avoid it. According to a 2018 survey by the U.S. government, almost all Americans know that exercise promotes health and think they should exercise, yet 50 percent of adults and 73 percent of high school students report they don’t meet minimal levels of physical activity, and 70 percent of adults report they never exercise in their leisure time.1”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“So there we were before breakfast in the hotel garden beneath palm trees, all wearing our matching conference T-shirts. The sound of waves crashing into the hotel beach was drowned out by a boom box playing loud electro workout music to pump us up: exuberant, high-octane tunes with pulsating rhythms that keep building to new crescendos. After dividing into teams, we spent the next forty-five minutes racing from one exercise to the next—planks, squats, sit-ups, sprints, and burpees (a combined squat, push-up, and vertical jump)—constantly high-fiving each other and shouting encouragements. At the end, everyone was exhausted, and we all congratulated each other for our efforts, agreeing vociferously how much fun it was. I enjoyed myself, but was it fun? I did the exercises as best I could, but what I actually enjoyed was the camaraderie, the beautiful setting, the high-fiving, and even the music. Afterward, I also enjoyed the feeling of having exercised intensely. But frankly, the planks, squats, sit-ups, sprints, and burpees were hard. The routine brought to mind the running guru George Sheehan’s observation that “exercise is done against one’s wishes and maintained only because the alternative is worse.”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“As Hippocrates would have predicted, scores of other studies on the effects of physical activity on morbidity and mortality yield similar results.61 That doesn’t mean, however, that physical activity is a surefire Fountain of Youth, and remember it doesn’t delay mortality by preventing aging per se. Instead, physical activity triggers a suite of mechanisms that increase the chances of staying healthy with age by retarding senescence and preventing many chronic diseases that contribute over time to mortality. This logic raises three vitally important insights that help explain the Donald Trumps of the world who don’t die young in spite of being sedentary and overweight. First, and most fundamentally, the mortality and morbidity statistics I have been citing are probabilities. Eating sensibly and exercising don’t guarantee long life and good health; they just decrease the risk of getting sick. By the same token, smokers have a higher risk of getting lung cancer, and individuals who are unfit or obese are more likely to get heart disease or become diabetic, but plenty don’t. Second, advances in medical care are shifting the relationship between morbidity and mortality.62 Conditions like diabetes, heart disease, and some cancers are no longer imminent death sentences but instead can be treated or held at bay for years with drugs that maintain blood sugar levels, decrease harmful cholesterol levels, lower blood pressure, and combat mutant cells. In Donald Trump’s case, for example, his reportedly normal blood pressure and cholesterol levels likely reflect the medications he takes to lower these risk factors.63”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“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.”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“In medical jargon, this longer period of illness prior to death is termed the extension of morbidity. Among westernized populations, many people become sick for a long time before they die from heart disease, type 2 diabetes, Alzheimer’s, and chronic respiratory disease; many also suffer from osteoarthritis, osteoporosis, and a growing list of autoimmune diseases.56 At least one in five Americans over the age of sixty-five is in fair or poor health. Despite this high morbidity, we nonetheless live much longer than our farmer ancestors, and a little longer than hunter-gatherers. The average American in 2018 lives to be seventy-eight years old, almost twice as long as one a hundred years ago.57 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. By not dying rapidly from smallpox in our youth, aren’t we fortunate to die slowly from heart disease at an older age? This thinking is mistaken.”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“We all die of something, and if you are following my argument in this chapter skeptically—as you should—that includes physically active people who eat sensibly and do everything else they are supposed to. In fact, despite being told to exercise, more inactive people like Donald Trump are living longer and in better health today than ever before. To evaluate this conundrum, let’s look closely at the probabilistic relationship between death (mortality) and illness (morbidity). Too often, statistics on aging focus on life span without also considering health span (the length of time spent in good health without morbidity). A useful way to think about both life span and health span is to graph functional capacity (a measure of health) on the y-axis versus time on the x-axis, as shown in figure 28. Someone who is generally healthy is at nearly 100 percent functional capacity most of the time, despite occasional, temporary illnesses. Then, at some point, age-related senescence commences and functional capacity declines because of serious illness, eventually leading to death.”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“An alternative to coddling one’s body with products that mimic the effects of exercise is to try non-physically active forms of suffering. This kind of “no pain, no gain” philosophy has inspired a dizzying array of self-inflicted hardships thought to ward off aging (an added benefit is their aura of virtue). Hoping to live longer, people take cold showers, restrict their caloric intake, endure long periods without eating, shun carbohydrates, burn their digestive tracts with spicy food, and more.53 Some of these strategies are downright questionable, and, with the exception of intermittent fasting, none is yet supported by solid evidence as a way to extend human longevity.54 Why is regular physical activity the best way to delay senescence and extend life? Recall that according to the costly repair hypothesis, organisms with restricted energy supplies (just about everyone until recently) must allocate limited calories toward either reproducing, moving, or taking care of their bodies, but natural selection ultimately cares only about reproduction. Consequently, our bodies evolved to spend as little energy as possible on costly maintenance and repair tasks. So while physical activities trigger cycles of damage and restoration, selection favors individuals who allocate enough but not too much energy to producing antioxidants, ramping up the immune system, enlarging and repairing muscles, mending bones, and so on. The challenge is to maintain and repair any damage from physical activity just enough and in the right place and the right time.”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“On account of diseases, predators, harsh weather, and other cruelties of nature (what biologists euphemistically term “extrinsic mortality”), older individuals inevitably become less common. As a result, natural selection acts less intensely on genes in elderly people that prolong life and promote repair. So even if middle-aged and old people help out younger generations, thus postponing Medawar’s selective shadow, the older we get, the less natural selection cares about fighting the accumulation of wear and tear that comes with age.39 Like it or not, the shadow eventually comes. But thankfully, its arrival and severity can be slowed and reduced by physical activity.”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“As we have learned, the immune system stimulates inflammation to defend us from pathogens as well as self-inflicted damage caused by physical activity. In short bursts, inflammation is lifesaving, but low levels of inflammation that last for months or years are pernicious because they slowly attack our bodies. Over time, the destructive effects of chronic, simmering inflammation accumulate in cells and tissues from head to toe including neurons in the brain, cartilage in joints, the walls of arteries, and insulin receptors in muscle and fat cells. If oxidation, mitochondrial dysfunction, mutations, glycation, and inflammation were not enough, plenty of other processes also contribute to senescence by damaging and degrading cells. Over time, tiny molecules glue themselves to the DNA in cells. These so-called epigenetic (on top of the genome) modifications can affect which genes are expressed in particular cells.31 Because environmental factors like diet, stress, and exercise partly influence epigenetic modifications, the older we are, the more of them we accumulate.32 Most epigenetic modifications are harmless, but the more you have for a given age, the higher your risk of dying.33 Other forms of senescence include cells losing the ability to recycle damaged proteins,34 inadequately sensing and acquiring nutrients,35 and (less likely) being unable to divide because the little caps (telomeres) that protect the ends of chromosomes from unraveling have become too short.36”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“Oxidation burns things gradually and steadily. Just as oxidation causes metal to rust and apple flesh to brown, it damages cells throughout the body by zapping DNA, scarring the walls of arteries, inactivating enzymes, and mangling proteins. Paradoxically, the more oxygen we use, the more we generate reactive oxygen species, so theoretically vigorous physical activities that consume lots of oxygen should accelerate senescence. A related driver of senescence is mitochondrial dysfunction. Mitochondria are the tiny power plants in cells that burn fuel with oxygen to generate energy (ATP). Cells in energy-hungry organs like muscles, the liver, and the brain can have thousands of mitochondria. Because mitochondria have their own DNA, they also play a role in regulating cell function, and they produce proteins that help protect against diseases like diabetes and cancer.29 Mitochondria, however, burn oxygen, creating reactive oxygen species that, unchecked, cause self-inflicted damage. When mitochondria cease to function properly or dwindle in number, they cause senescence and illness.30”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“As we age, not all of us will get high blood pressure, dementia, or incontinence. In addition, some species seem immune to senescence. Bowhead whales, giant tortoises, lobsters, tortoises, and some clams can live and reproduce after hundreds of years. (The world record is a clam named Ming who researchers dredged up and, in the cruelest of ironies, then killed to determine it was 507 years old.)28 How and why do certain animals and humans, including those who exercise, tend to senesce more slowly?”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“Aging is inexorable, but senescence, the deterioration of function associated with advancing years, correlates much less strongly with age. Instead, senescence is also influenced strongly by environmental factors like diet, physical activity, or radiation, and thus can be slowed, sometimes prevented, and even partly reversed. The distinction between aging and senescence may seem obvious, but the two processes are frequently confused. Many conditions occur more commonly with advancing age, but only some are actually caused by age. Menopause, for example, is a normal consequence of aging that happens when a woman’s ovaries run out of eggs. In contrast, type 2 diabetes occurs among some older people for reasons not intrinsic to the aging process itself but instead from factors like obesity and physical inactivity whose damaging effects accumulate with age.”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“All Hadza women dig, but grandmothers dig more than mothers in part because they don’t have to nurse or spend as much time taking care of little ones. According to measurements by Kristen Hawkes and colleagues, a typical Hadza mother forages about four hours a day, but grandmothers forage on average five to six hours a day.18 On some days they dig less and spend more time collecting berries, but overall they work longer hours than mothers do. And just as grandmothers spend about seven hours every day foraging and preparing food, grandfathers continue to hunt and to collect honey and baobab fruits, traveling just as far on most days as younger men do. According to the anthropologist Frank Marlowe, “Old men are the most likely to fall out of tall baobab trees to their deaths, since they continue to try to collect honey into old age.”19 How many elderly Americans dig several hours a day, let alone climb trees and hunt animals on foot? We can, however, compare how much Americans and Hadza walk. A study of thousands found that the average twenty-first-century woman in the United States aged eighteen to forty walks 5,756 steps a day (about two to three miles), but this number declines precipitously with age, and by the time they are in their seventies, American women take roughly half as many steps. While Americans are half as active in their seventies as in their forties, Hadza women walk twice as much per day as Americans, with only modest declines as they age.20 In addition, heart rate monitors showed that elderly Hadza women actually spent more of their day engaged in moderate to vigorous activity than younger women who were still having children.21 Imagine if elderly American women had to walk five miles a day to shop for their children and grandchildren, and instead of pulling items off the shelves, they had to dig for several hours in hard, rocky soil for boxes of cereal, frozen peas, and Fruit Roll-Ups. Not surprisingly, hard work keeps elderly hunter-gatherers fit. One of the most reliable measures of age-related fitness is walking speed—a measure that correlates strongly with life expectancy.22 The average American woman under fifty walks about three feet per second (0.92 meter per second) but slows down considerably to two feet per second (0.67 meter per second) by her sixties.23 Thanks to an active lifestyle without retirement, there is no significant age-related decline in walking speed among Hadza women, whose average pace remains a brisk 3.6 feet per second (1.1 meters per second) well into their seventies.24 Having struggled to keep up with elderly Hadza grandmas, I can attest they maintain a steady clip even when it is blisteringly hot. Older Hadza men also walk briskly.”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“To what extent and in what circumstances physical activity shifts metabolisms thus offsetting efforts to lose weight remains to be elucidated, but the fact remains that many studies have shown that exercise, including walking, can lead to weight loss. But to do so, one needs to walk considerably more than half an hour per day for many months. In addition, people who exercise more may compensate metabolically, negating some of the effects of added physical activity. Finally, it truly is faster and it’s often easier to lose weight by dieting because everyone needs to eat but no one has to exercise, and not eating five hundred calories of energy-rich food (four slices of bacon) requires less time and effort than walking five miles a day. Please, I do not wish to trivialize how hard it is to exercise if one is unfit and overweight: it can be uncomfortable, unpleasant, and disheartening, and disabilities can make it challenging or impossible. But for those unwilling or unable to run, swim, or do other vigorous exercises, walking remains an inexpensive and pleasant way to get a moderate and useful dose of physical activity. Even more important, regardless of how one initially loses weight, keeping the weight off almost always demands physical activity. The majority of dieters who do not exercise regain about half their lost pounds within a year, and thereafter the rest typically creeps back slowly but surely. Exercise, however, vastly increases the chances of maintaining weight loss.49 One example of this payoff comes from an experiment conducted here in Boston. When doctors put 160 overweight police officers on low-calorie diets for eight weeks, some with and some without exercise, all the officers lost sixteen to thirty pounds (seven to thirteen kilograms) with the ones who exercised losing slightly more. But once the crash diet was over and the policemen went back to their normal diets, only the officers who continued to exercise avoided weight regain; all the rest regained most or all of the pounds they initially lost.50 Many other studies confirm that physical activity, including walking, helps keep those lost pounds off.51 Maybe those ten thousand steps a day aren’t such a bad idea after all….”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“Nothing about metabolism, however, is simple, and one last and important complication regarding efforts to walk off weight is a still poorly understood phenomenon known as metabolic compensation. Once again, studies of the Hadza play a role in how we understand this phenomenon. When Herman Pontzer and his colleagues measured daily energy expenditures in the Hadza, they were surprised to find that the highly active Hadza spend about the same total number of calories per day as sedentary industrialized people with the same lean body weight.44 In addition, when Pontzer and colleagues collected energetic data from adults in many countries including the United States, Ghana, Jamaica, and South Africa, they observed that more active people spent only slightly more calories per day than more sedentary people who weighed the same. In addition, individuals who were more physically active didn’t have total energy budgets as high as their exertions would predict.45 How could someone who spent five hundred extra calories a day exercising not have a total energy budget that is five hundred calories higher? The proposed explanation is that people’s total energy budgets are constrained: if I use five hundred extra calories walking, I’ll spend less energy on my resting metabolism to help pay for my exertions.46 This controversial idea (termed the constrained energy expenditure hypothesis) is still being tested, as is its relevance to weight loss. If correct, then contrary to many people’s expectations, exercisers might spend almost the same number of total calories per day as similar-sized but more sedentary individuals despite devoting more energy to being active. To appreciate the implications of this phenomenon, consider that the Hadza spend about 15 percent more of their total energy budget on activities like walking, digging, and carrying.47 In addition, as we will see later, exercise can stimulate repair and maintenance mechanisms that elevate people’s resting metabolic rates—an “afterburn”—for a few hours to as much as two days afterward.48 Yet if very active Hadza hunter-gatherers and exercising industrial people have total energy budgets that are about the same as similar-sized but physically inactive industrials, then they must spend less energy on other things like maintenance or reproduction. This may seem implausible, but we have already seen this phenomenon in people who lose a lot of weight, like the extreme dieters in the Minnesota Starvation Experiment whose resting metabolic rates plummeted.”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“Lo and behold, studies that prescribe higher, more evolutionarily normal levels of exercise, including walking, have the potential to be more effective for weight loss. One intriguing study asked fourteen overweight and unfit men and women to hew to the standard 150 minutes a week by walking briskly five times a week, but assigned another sixteen individuals the task of walking twice as much. Apart from the prescribed exercise, both groups were otherwise free to eat and sit as much as they wished. After twelve weeks, the 150-minute-a-weekers barely lost any weight, but the 300-minute-a-weekers lost an average of six pounds.42 At this rate they potentially could lose twenty-six pounds in a year. An even more demanding study compared obese men prescribed seven hundred calories of exercise a day (about five miles of jogging) with men asked simply to cut back their diets by the same number of calories. Over three months, both groups lost almost seventeen pounds (seven and a half kilograms), but the ones who exercised lost more unhealthy organ fat, even though they also ate more.43”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“If I follow a standard prescription of briskly walking thirty minutes a day, almost two extra miles, I’ll spend about a hundred extra calories per day, theoretically allowing me to shed approximately five pounds in half a year—about the reductions most studies report. If a skinny hunter-gatherer mother loses five pounds in six months, she’s in trouble, but many obese American dieters aim to lose about fifty-five pounds.39 Losing that many pounds that quickly through exercise alone would theoretically require Herculean efforts like running eight miles a day. Although far from easy, dieting is unquestionably more effective for shedding many pounds. While walking 30 minutes a day won’t lead to rapid, spectacular weight losses, an evolutionary and anthropological perspective puts a different spin on the argument that walking expends too few calories to shed excess pounds. While the commonly prescribed two-mile daily walk expends a pittance—just 4 percent—of the average person’s daily energy budget of twenty-seven hundred calories, that pittance is partly attributable to setting the exercise bar so low. It bears repeating that the standard public health recommendation is 150 minutes of moderate exercise every week. This amounts to a paltry 21 minutes a day, one-sixth the level of physical activity among nonindustrial people like the Hadza.40 Although jobs, commuting, and other obligations fill our days with necessarily sedentary activities, the average American still spends at least eight times as much time (170 minutes per day) watching television.41 It is no wonder that studies using modest exercise doses report modest weight losses.”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“And therein lies another key difference between walking today and in ancient times. If I walk ten thousand extra steps to place my body in negative energy balance, it is literally a piece of cake for me to wipe out the extra cost of such a walk. The ease of refueling with a donut or a Gatorade or just by sitting at my desk for the rest of the day helps explain the counterintuitive result we just saw from the DREW study in which the women who exercised the most lost less weight than predicted: they ate more.36 Happily, more than a dozen studies on the effects of exercise, food intake, and non-exercise physical activity on weight loss found that modest doses of prescribed exercise rarely cause people to spend the rest of the day as couch potatoes erasing the benefits of their exertions.37 However, several experiments that required large doses of exercise (one involved training for a half marathon) did cause exercisers to eat more.38 When the body regulates energy balance like a thermostat, it apparently does so more through diet than through physical activity.”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“For someone who is fifty pounds overweight, losing three to five pounds over half a year is a frustrating drop in the bucket. Accordingly, a stock response to these studies has been to declare exercise futile for trimming your waist. Before we entirely dismiss the weight control benefits of walking, the most fundamental type of endurance physical activity, let’s examine the major arguments behind this contention through the lens of evolutionary anthropology. The first is the specter of compensatory mechanisms, notably fatigue and hunger. If I walk ten thousand extra steps, I’ll be more tired and hungry, so I’ll rest and eat more to recoup lost calories. From an evolutionary perspective, these urges make sense. Because natural selection ultimately favors those who can allocate as much energy as possible to reproduction, our physiology has been tuned over millions of generations to hoard energy, especially fat. Further, because almost no one until recently was able to become overweight or obese, our bodies primarily sense if we are gaining or losing weight rather than how much excess fat we have. Whether you are skinny or stout, negative energy balance—including dieting—causes a starvation response that helps us restore energetic equilibrium or, better yet, gain weight so we can shunt more energy toward reproduction.35 It’s unfair, but losing ten pounds elicits food cravings and the desire to be inactive regardless of whether one is skinny or obese.”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“On the face of it, it seems preposterous to think that walking doesn’t help with weight loss. Recall that energy balance is the difference between the calories one ingests and the calories one spends. You probably burn roughly 50 calories more by walking a two-thousand-step mile than driving the same distance. So trudging ten thousand additional steps a day (five miles) will expend a respectable extra 250 calories per day.30 To be sure, those ten thousand added steps might make you hungrier, but if you snack sensibly and consume 100 calories less than you walked off, those supplementary steps will eventually amount to a deficit of about 3,000 calories a month. That amount is just shy of 3,500 calories, the supposed number of calories in a pound of fat according to a much-cited, overly simplistic, and inaccurate 1958 study.31 Further, low- to moderate-intensity activities like walking burn relatively more fat than carbohydrates (hence the “fat-burning zones” on some exercise machines).32 As a result, lots of people try to trudge away extra pounds. Biological systems such as bodies are messy, and anyone who has struggled to lose weight knows that simple theories rarely apply to the convoluted realities of weight loss. What works for one person fails for another, and while many people successfully shed pounds when they start a new weight-loss plan, satisfaction often turns to frustration as the initial rate of weight loss diminishes and then reverses. Study after study has shown that overweight or obese people prescribed standard doses of exercise for a few months usually lose at most a few pounds. For example, one experiment with the clever acronym DREW (Dose Response to Exercise in Women) assigned 464 women to 0, 70, 140, and 210 minutes of slow walking a week (140 minutes is about five added miles). Apart from their prescribed exercise, the women took about five thousand additional steps per day as they went about their normal activities. After six months, those prescribed the standard 140 minutes a week lost only five pounds, while those assigned 210 minutes lost a paltry three pounds (more on this unexpected result below).33 Other controlled studies on overweight men and women report similarly modest losses.34”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding

“Because life is fundamentally about acquiring and using scarce energy to make more life, those better able to conserve energy would have had a reproductive advantage.”
― Daniel E. Lieberman, Exercised: Why Something We Never Evolved to Do Is Healthy and Rewarding