Juan Siliezar in The Harvard Gazette:
Contemporary Americans have access to custom workout routines, fancy gyms, and high-end home equipment like Peloton machines. Even so, when it comes to physical activity, our forebears of two centuries ago beat us by about 30 minutes a day, according to a new Harvard study.
Researchers from the lab of evolutionary biologist Daniel E. Lieberman used data on falling body temperatures and changing metabolic rates to compare current levels of physical activity in the United States with those of the early 19th century. The work is described in Current Biology. The scientists found that Americans’ resting metabolic rate — the total number of calories burned when the body is completely at rest — has fallen by about 6 percent since 1820, which translates to 27 fewer minutes of daily exercise. The culprit, the authors say, is technology.
“Instead of walking to work, we take cars or trains; instead of manual labor in factories, we use machines,” said Andrew K. Yegian, a postdoctoral fellow in the Department of Human and Evolutionary Biology and the paper’s lead author. “We’ve made technology to do our physical activity for us. … Our hope is that this helps people think more about the long-term changes of activity that have come with our changes in lifestyle and technology.”
While it’s been well documented that technological and social changes have reduced levels of physical activity the past two centuries, the precise drop-off had never been calculated. The paper puts a quantitative number to the literature and shows that historical records of resting body temperature may be able to serve as a measure of population-level physical activity.