BURN

An evolutionary anthropologist explores the evergreen science of human metabolism.

“Each ounce of living human tissue burns ten thousand times more energy each day than an ounce of the Sun.” So writes Pontzer, a research professor at the Duke Global Health Institute, in this nifty piece of science writing. Without dumbing down the topic or eliding elements of contention, the author outlines the broad workings of human metabolism by examining people across different cultures with vastly different lifestyles. Among other fascinating topics, he delves into the mechanics of metabolism on the cellular level, the varied metabolic strategies that evolved in our species and other primates, and the radical metabolic acceleration of warmblooded creatures favored by natural selection to increase energy availability for growth, survival, and reproduction. Particularly illuminating is Pontzer’s smooth rendering of the interactive, complex system that manages our physical activity, growth, thermoregulation, and digestion. Humans developed the metabolic strategy of storing extra calories as fat, a kind of rainy-day fund for disruptions in energy supply. However, in today’s industrialized world, when few people rely on hunting or gathering to procure their daily calories, rainy days are fewer and further between. Since our metabolism can find an energy balance when supplies are low, continuing to consume more calories leads directly to obesity, Type 2 diabetes, heart disease, and other ailments. Pontzer offers a host of fruitful explanations of satiety and reward signals from the brain; flavor engineering by junk-food chemists, who use “a mind-boggling array of techniques and additives to make food that is highly palatable without being satiating”; the role of foods that are filling, rich in nutrients, and low in calories; and the importance of movement bequeathed to us by our hunter-gatherer forebears—and evident today among the Hadza people of Tanzania, who “don’t develop obesity and metabolic disease for the simple reason that their food environment doesn’t drive them to overconsume.”

An absorbing, instructive lesson for anyone concerned about their health.