My eldest son, now 18, has a severely disabling genetic disorder; since childhood, he has been carefully cared for by a team of doctors at Columbia University Medical Center in Manhattan. His geneticist, one of the most formidable intellects I have ever met, had worked on the Human Genome Project in the 1990s, sequencing the LEP gene, which encodes leptin, a hormone that helps inhibit hunger. She longed to distill her research into an eureka pill for those of us susceptible to nighttime refrigerator intrusions, that extra slice of chocolate cake – a holy grail of treatments. In the end, however, she and her colleagues fell short. “It’s all about diet and exercise,” she told me once, “just as your mother begged you when you were a child.”
“Exercised”, a new comprehensive and vigorous work by Daniel Lieberman, Professor Edwin M. Lerner II of Biological Sciences at Harvard, investigates how and why exercise is so good for us when, as a species, we evolved as moccasins to conserve calories for scarce seasons. Lieberman opens the book with a pun: the title refers not only to physical effort in search of good health, but also to the adjective exercised, “to be bored, anxious, worried, harassed”. As he knows, many of us are confused about the exercises; the thought of 30 minutes on a NordicTrack elliptical or deadlift at the gym can raise our blood pressure.
But is there an evolutionary basis for our collective dread? Lieberman argues that even our iron-skinned ancestors were lazy. When we analyze a range of cultures around the world, or even our close primate relatives, such as chimpanzees, we detect a clear pattern: our species is adept at spending a lot of our time just relaxing in order to conserve calories. Throughout the book, Lieberman refers to the Hadza, a foraging people grouped in Tanzania; despite the profound differences between their routines and ours, between their diets and ours, common biology is not so different. They sit in the camps at almost the same rates as us, caught in administrative work.
He considers sitting and if it’s as bad for us as smoking (it’s not)[HC1] [k2]. And he ponders about fitness marketing. “For me, the apotheosis of what is good and bad in contemporary exercise is the treadmill. Treadmills are incredibly useful, but they are also noisy, expensive, and occasionally treacherous. . . The only way to endure the boredom and discomfort of a workout on the treadmill is by listening to music or a podcast. What would my distant hunter-gatherer ancestors have thought of paying a lot of money to suffer through unnecessary physical activity on an irritating machine that gets us nowhere and does nothing? “
There is a dry didactic quality to “Exercizado”; Lieberman is a first-rate scientist and convincing writer, but the book lacks the stylistic spark of a Robert Sapolsky or David Eagleman. And yet, Lieberman’s clarity never falters. When the book changes to prescriptive sections – should I focus on cardio instead of dumbbells? Are gym exercises still beneficial as we age? – he readily recognizes that the data is more suggestive than certain. (A runner, he leans toward cardio as his favorite exercise.) He is particularly good at destroying myths, organizing chapters around debunking assumptions about what constitutes fitness and health. Eight hours of sleep may not be the most effective way to rest. Charles Atlas, on the contrary, has evolved, as the title of a chapter describes, “from strong to thin”, taking advantage of our most graceful forms about, say, most Neanderthals. Your answers to physiological questions – “Does it go bad for your knees?” “Should my 90-year-old grandmother do bench press every week?” – dispel lazy buzzwords.
They also inspire. He presses his case on preventive care, often rejected by Americans as a violation of their freedom to be addicted to television. “I am aware that people like me often sound like broken records. . . . Please do not react like this with cancer, because the potential of exercise to fight cancer is underestimated and exploited inefficiently. . . . Just as natural selection favors humans who acquire and expend as much calories in reproduction as possible, selection that leads to cancer favors malignant cells that acquire as many calories as possible and use them to create more copies of themselves. ”He highlights the main culprits – reproductive hormones, sugar, inflammation and antioxidants – and explains why exercise can be our most powerful weapon to keep the emperor away from all diseases.
Going back to the Columbia geneticist’s point of view: if “Exercised” occasionally reads in the tone of his mother’s stern voice, wagging his finger and begging you to eat your vegetables and run around the block, then that’s fine. Lieberman accomplished his mission. But the science behind his arguments is revealing, with exciting implications for evolutionary biology. Written in vivid prose, with ample graphics, “Exercised” is an excellent compendium on the broad medical benefits of exercise and a roadmap for our pandemic for better health.
Hamilton Cain is the author of “This Boy’s Faith: Notes from a Southern Baptist Education” and a member of the National Book Critics Circle. He lives with his family in Brooklyn, NY
Exercise: Why something we never evolved to do is healthy and rewarding
Daniel Lieberman
Pantheon, 464 pages, $ 29.95