Book Review: Exercised – Why Something We Never Evolved To Do Is Healthy and Rewarding

I learned of this book from a Twitter account that I follow. The book looks at exercise from the anthropology and biology perspective to answer a few key questions such as:

  • Did we evolve over thousands of years to exercise? Or did we evolve not to spend more energy than we should? Why is exercise such a struggle for many?
  • Why is sitting harmful to our body?
  • How much exercise is enough? What exercise should we do?

The book is jam-packed with research and studies that serve as corroborating evidence of the points that the author tries to make. It must have taken him a long time to dig into hundreds of research like that, including trips to remote places so that he could live with ethnic tribes whose lifestyle is so different from ours dominated by modern technologies. Clearly, the author knows what he is talking about. Even though it’s very research-oriented, the book is well-written and engaging. I do admit that I got tired at times due to its overwhelming length and the number of topics packed in one volume, but for the most part, it was time well spent and an enjoyable read.

The core message of the book is nothing new: Exercise is great for our health and rewarding. But this book offers a little bit more insights into how we can integrate exercise into our daily routine more easily, why certain things happen and how we should design exercise that can benefit us more, especially when we age. I am fairly certain that readers will get away from reading this book with some new knowledge. Below are some of my notes:

“Imagine you have been asked to conduct a scientific study on how much, when, and why “normal” people exercise. Because we tend to think of ourselves and our societies as normal, you’d probably collect data on the exercise habits of people like you and me. This approach is the norm in many fields of inquiry. For example, because most psychologists live and work in the United States and Europe, about 96 percent of the subjects in psychological studies are also from the United States and Europe.

Such a narrow perspective is appropriate if we are interested only in contemporary Westerners, but people in Western industrialized countries aren’t necessarily representative of the other 88 percent of the world’s population. Moreover, today’s world is profoundly different from that of the past, calling into question who among us is “normal” by historical or evolutionary standards. Imagine trying to explain cell phones and Facebook to your great-great-great-grandparents. If we really want to know what ordinary humans do and think about exercise, we need to sample everyday people from a variety of cultures instead of focusing solely on contemporary Americans and Europeans who are, comparatively speaking, WEIRD (Western, Education, Industrialized, Rich, Democratic)

Excerpt From: Lieberman, Daniel. “Exercised : Why Something We Never Evolved to Do Is Healthy and Rewarding

“Which brings us back to physical inactivity. From the perspective of natural selection, when calories are limited, it always makes sense to divert energy from nonessential physical activity toward reproduction or other functions that maximize reproductive success even if these trade-offs lead to ill health and shorter life spans. 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”

“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. Let’s also refrain from stigmatizing anyone for being normal by avoiding nonessential exertion. Unfortunately, we have a long way to go. According to a 2016 survey, three out of four Americans think obesity is caused by a lack of willpower to exercise and control appetite.27 Despite stereotypes of non-exercisers as lazy couch potatoes, it is deeply and profoundly normal to avoid unnecessarily wasting energy. Rather than blame and shame each other for taking the escalator, we’d do better to recognize that our tendencies to avoid exertion are ancient instincts that make total sense from an evolutionary perspective.”

Excerpt From: Lieberman, Daniel. “Exercised : Why Something We Never Evolved to Do Is Healthy and Rewarding

“Although most fat is healthy, obesity can turn fat from friend into inflammatory foe. The biggest danger is when fat cells malfunction from overswelling. The body has a finite number of fat cells that expand like balloons. If we store normal amounts of fat, both subcutaneous and organ fat cells stay reasonably sized and harmless. However, when fat cells grow too large, they distend and become dysfunctional like an overinflated garbage bag, attracting white blood cells that trigger inflammation”

“A second way lengthy periods of sitting may incite widespread, low-grade inflammation is by slowing the rate we take up fats and sugars from the bloodstream. When was the last time you had a meal? If it was within the last four or so hours, you are in a postprandial state, which means your body is still digesting that food and transporting its constituent fats and sugars into your blood. Whatever fat and sugar you don’t use now will eventually get stored as fat, but if you are moving, even moderately, your body’s cells burn these fuels more rapidly. Light, intermittent activities such as taking short breaks from sitting and perhaps even the muscular effort it takes to squat or kneel reduce levels of fat and sugar in your blood more than if you sit inertly and passively for long.38 Such modest extra demands appear to be beneficial because although fat and sugar are essential fuels, they trigger inflammation when their concentrations in blood are too high.39 Put simply, regular movement, including getting up every once in a while, helps prevent chronic inflammation by keeping down postprandial levels of fat and sugar.

Excerpt From: Lieberman, Daniel. “Exercised : Why Something We Never Evolved to Do Is Healthy and Rewarding

“These ubiquitous miniature batteries, which power all life on earth, are called ATPs (adenosine triphosphates). As the name implies, each ATP consists of a tiny molecule (an adenosine) attached to three molecules of phosphate (a phosphorus atom surrounded by oxygen atoms). These three phosphates are bound to each other in a chain, one on top of the other, storing energy in the chemical bonds between each phosphate. When the last of these phosphates is broken off using water, the tiny quantity of energy that binds it to the second phosphate is liberated along with one hydrogen ion (H+), leaving behind an ADP (adenosine diphosphate). This liberated energy powers almost everything done by every cell in the body like firing nerves, making proteins, and contracting muscles. And, critically, ATPs are rechargeable. By breaking down chemical bonds in sugar and fat molecules, cells acquire the energy to restore ADPs to ATPs by adding back the lost phosphate. The problem is, however, that regardless of whether we are hyenas or humans, the faster we run, the more our bodies struggle to recharge these ATPs, thus curtailing our speed after a short while.”

“Sugar is synonymous with sweetness, but it’s first and foremost a fuel used to recharge ATPs through a process termed glycolysis (from glyco for “sugar” and lysis for “break down”). During glycolysis, enzymes swiftly snip sugar molecules in half, liberating the energy from those bonds to charge two ATPs. Restoring ATPs from sugar doesn’t require oxygen and is rapid enough to provide almost half the energy used during a thirty-second sprint. In fact, a fit human can store enough sugar to run nearly fifteen miles. But there is a consequential catch: during glycolysis the leftover halves of each sugar, molecules known as pyruvates, accumulate faster than cells can handle. As pyruvates pile up to intolerable levels, enzymes convert each pyruvate into a molecule called lactate along with a hydrogen ion (H+). Although lactate is harmless and eventually used to recharge ATPs, those hydrogen ions make muscle cells increasingly acidic, causing fatigue, pain, and decreased function. Within about thirty seconds, a sprinter’s legs feel as if they are burning. It then takes a lengthy period of time to slowly neutralize the acid and shuttle the surplus lactate into the third, final, but long-term aerobic energy process”

Excerpt From: Lieberman, Daniel. “Exercised : Why Something We Never Evolved to Do Is Healthy and Rewarding

“If you keep up a regimen of two sessions a week of HIIT, your muscles will gradually improve their ability to produce high, rapid forces in part by augmenting how many fibers contract simultaneously when stimulated by nerves. In addition, your muscles will change composition. Although HIIT cannot stimulate your body to produce more fast-twitch muscle fibers, the ones you have will thicken, making you stronger and hence faster. On average, sprinters’ muscles are more than 20 percent thicker than distance runners. HIIT can also modify slower, more fatigue-resistant pink fibers into faster, more fatigable white fibers; lengthen fibers slightly, thus boosting their shortening speed; and increase the percentage of fibers in a muscle that contracts, thereby increasing force. But these and other changes don’t happen on their own, and require constant effort to maintain. If you want to run faster, you have to try to run faster.”

“The benefits of regular HIIT go well beyond its effect on muscles. Among other payoffs, HIIT increases the heart’s ability to pump blood efficiently by making its chambers larger and more elastic. HIIT also augments the number, size, and elasticity of arteries and increases the number of tiny capillaries that infuse muscles. HIIT further improves muscles’ ability to transport glucose from the bloodstream and increases the number of mitochondria within each muscle, thus supplying more energy. These and other adaptations lower blood pressure and help prevent heart disease, diabetes, and more. The more we study the effects of HIIT, the more it appears that HIIT should be part of any fitness regimen, regardless of whether you are an Olympian or an average person struggling to get fit.”

Excerpt From: Lieberman, Daniel. “Exercised : Why Something We Never Evolved to Do Is Healthy and Rewarding

“And therein lies an important lesson about why we exercise. Because exercise by definition isn’t necessary, we mostly do it for emotional or physical rewards, and on that horrid April day in 2018, the only rewards were emotional—all stemming from the event’s social nature. For the last few million years humans rarely engaged in hours of moderate to vigorous exertion alone. When hunter-gatherer women forage, they usually go in groups, gossiping and otherwise enjoying each other’s company as they walk to find food, dig tubers, pick berries, and more. Men often travel in parties of two or more when they hunt or collect honey. Farmers work in teams when they plow, plant, weed, and harvest. So when friends or CrossFitters work out together in the gym, teams play a friendly game of soccer, or several people chat for mile after mile as they walk or run, they are continuing a long tradition of social physical activity.”

Excerpt From: Lieberman, Daniel. “Exercised : Why Something We Never Evolved to Do Is Healthy and Rewarding

“In the end, the 2018 HHS panel concluded that some physical activity is better than none, that more physical activity provides additional health benefits, and that for “substantial health benefits” adults should do at least 150 minutes per week of moderate-intensity or 75 minutes per week of vigorous-intensity aerobic physical activity, or an equivalent combination of the two. (Moderate-intensity aerobic activity is defined as between 50 and 70 percent of your maximum heart rate; vigorous-intensity aerobic activity is 70 to 85 percent of your maximum heart rate.) They also reaffirmed the long-standing recommendation that children need an hour of exercise a day. Finally, they recommended everyone also do some weights twice a week.”

Excerpt From: Lieberman, Daniel. “Exercised : Why Something We Never Evolved to Do Is Healthy and Rewarding

“Aerobic exercise additionally stimulates the growth and upkeep of just about every other system in the body. Within muscles, it increases the number of mitochondria, promotes the growth of muscle fibers, and increases their ability to store carbohydrates and burn fat. In terms of metabolism, it burns harmful organ fat, improves the body’s ability to use sugar, lowers levels of inflammation, and beneficially adjusts the levels of many hormones including estrogen, testosterone, cortisol, and growth hormone. Weight-bearing aerobic activities (alas, not swimming) stimulate bones to grow larger and denser when we are young and to repair themselves as we age, and they strengthen other connective tissues. In moderation, aerobic exercise stimulates the immune system, providing enhanced ability to ward off some infectious diseases. And last but not least, aerobic exercise increases blood flow to the brain and elevates the production of molecules that stimulate brain cell growth, maintenance, and function. A good cardio workout really does improve cognition and mood.”

Excerpt From: Lieberman, Daniel. “Exercised : Why Something We Never Evolved to Do Is Healthy and Rewarding
Physical Activity Guidelines for Americans. Source: HHS

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