Book Summary

• Humans evolved to move, but modern humans don’t “have” to exercise like our ancestors did to find food, shelter, and flee predators.

• Not exercising causes a whole host of problems including but not limited to increased obesity, type 2 diabetes, heart disease, cancer, osteoporosis, and sarcopenia.

• Because we don’t have to exercise for the necessities to survive, we need to intentionally exercise to stave off these diseases and seek out physical activity.

Notes & Highlights

• Exercise today is defined as voluntary physical activity undertaken for the sake of health and fitness.

• Human resting metabolisms are flexible.

• Avoiding exertion are ancient instincts that make total sense from an evolutionary perspective.

• It is reasonable to conclude that those of us who regularly sit in chairs with backrests have weak back muscles that lack endurance, making it uncomfortable to sit for long on the ground or on stools. The result is a vicious cycle of chair dependency.

• The people of the Hadza tribe spend about nine “non-ambulatory” hours on a typical day, mostly sitting on the ground with their legs in front of them, but also squatting about two hours a day and kneeling an hour a day. So while nonindustrial people engage in considerably more physical activity than average industrialized and postindustrialized people, they also sit a lot.

• 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.

• There is little evidence that links habitual sitting in flexed or slouched postures with back pain. There is also little good evidence that people who sit longer are more likely to have back pain.

• A good dose of physical activity early in the day helps sleep come more easily at night.

  • Exercise increases sleep pressure, and it stimulates the body to counter the initial fight-and-flight response with a deeper “rest and digest” response.

• Astronauts in the gravity-free environment of space can lose 20 percent of their muscle mass in just a week or two.

• Grip strength in industrialized countries like the United States and the U.K. declines about 25 percent from the age of twenty-five to seventy-five.

• Studies of aging demonstrate that hunter-gatherers, like postindustrial Westerners, lose strength as the years pass, but at a considerably slower rate.

• As muscle mass declines, people load their bones less, contributing to osteoporosis.

• The average American takes 4,774 steps. Modern-day hunter-gatherers average around 20,000 steps per day.

• Running injury rates follow a U-shaped curve: the highest probabilities of injury are among novices radically increasing their mileage, competitive speedsters, and marathoners, but everyday runners in between these extremes are much less prone to problems.

• Running and other forms of physical activity help promote healthy cartilage and may protect against osteoarthritis.

• Runners with plenty of stamina but weak core muscles and stabilizing muscles in their feet and legs are more at risk of injuries to the knee and elsewhere.

• Most experienced runners and coaches agree on four key, related elements when it comes to running: (1) not overstriding, which means landing with your feet too far in front of your body; (2) taking about 170-180 steps a minute; (3) not leaning too much, especially at the waist; (4) landing with a nearly horizontal foot, thus avoiding a large, rapid impact force with the ground.

• The active grandparent hypothesis raises a classic chicken-or-egg question. How much do humans live to old age so they can be active grandparents helping younger generations, or how much does their hard work cause them to live long lives in the first place?

• “Humans were meant to move.”

• 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.

• Don’t smoke, avoid obesity, eat and drink sensibly, and of course stay physically active.

• We evolved to be physically active as we age, and in turn being active helps us age well.

• When people are asked what keeps them from exercising, they almost always list time as a main barrier.

• Lack of time can be stressful, but even the busiest people manage to find time to do things they enjoy or find rewarding like watch TV, surf the web, or gossip. I suspect millions of non-exercisers would succeed in making exercise a greater priority if they found it more enjoyable, but for them, exercise is often emotionally unrewarding and physically unpleasant.

• Humans evolved to exercise in groups, so workout in a group setting whenever you can.

• Exercise produces a release of endogenous drugs that elevate your mood, alertness, and tranquility. They include dopamine, serotonin, endorphins, and endocannabinoids.

• How to make exercise more fun:

  • Be social: exercise with friends or in a group.

  • Listen to music, podcasts, or watch a movie.

  • Exercise outside.

  • Dance or play sports and games.

  • Mix things up and have a variety of different exercises.

• In the United States, less than one in four children get at least an hour of physical activity a day.

• Exercising a minimum of 150 minutes per week is as good a prescription as any and has the 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.

• Because plaques contain calcium, which shows up nicely in a CT scan, doctors routinely score plaques by their calcium content: a coronary artery calcium (CAC) score.

• Because the fundamental challenge of aerobic activity is to deliver more oxygen at a faster rate to muscles and other organs, this demand stimulates the chambers of the heart to grow stronger, more capacious, and more elastic.

• In blood, aerobic exercise augments the red blood cell count but also increases the volume of plasma, reducing viscosity so the heart can pump more easily.

• Aerobic exercise increases blood flow to the brain and elevates the production of molecules that stimulate brain cell growth, maintenance, and function.

• 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.”

• While overweight people who exercise and are physically fit lessen their risk of chronic disease, if you must choose between being fit and fat or unfit and lean, the evidence overwhelmingly indicates you should gamble on being unfit and lean.

• Being active doesn’t cancel out the higher risk of death associated with obesity, but being active is still beneficial if one is obese.

• Athletes who exclusively weight train without also doing some cardio appear to be at as much risk as sedentary individuals of developing chronic high blood pressure and cardiovascular disease.

• We get osteoporosis only if we failed to develop enough peak bone mass when we were young, or if we lose bone too rapidly as we age.