Debunking the Hunter-Gatherer Workout: Findings suggest inactivity is not the source of modern obesity
DARWIN isn’t required reading for public health officials, but he should be. One reason that heart disease, diabetes and obesity have reached epidemic levels in the developed world is that our modern way of life is radically different from the hunter-gatherer environments in which our bodies evolved. But which modern changes are causing the most harm?
Many in public health believe that a major culprit is our sedentary lifestyle. Faced with relatively few physical demands today, our bodies burn fewer calories than they evolved to consume — and those unspent calories pile up over time as fat. The World Health Organization, in discussing the root causes of obesity, has cited a “decrease in physical activity due to the increasingly sedentary nature of many forms of work, changing modes of transportation and increasing urbanization.”
This is a nice theory. But is it true? To find out, my colleagues and I recently measured daily energy expenditure among the Hadza people of Tanzania, one of the few remaining populations of traditional hunter-gatherers. Would the Hadza, whose basic way of life is so similar to that of our distant ancestors, expend more energy than we do?
Our findings, published last month in the journal PLoS ONE, indicate that they don’t, suggesting that inactivity is not the source of modern obesity.
Previous attempts to quantify daily energy expenditure among hunter-gatherers have relied entirely on estimation. By contrast, our study used a technique that calculates the body’s rate of carbon dioxide production — and hence the calories burned per day — by tracking the depletion of two isotopes (deuterium and oxygen-18) in an individual’s urine over a two-week period.