Last month, researchers affiliated with the World Health Organization and the London School of Hygiene and Tropical Medicine reported that, worldwide, people’s waistlines are expanding, with the total combined weight of human beings on Earth now exceeding 287 million tons. About 3.5 million tons of that global human biomass is due to obesity, a third of which exists in North America, although we account for only 6 percent of the world’s population.
The study was widely publicized, especially after the BBC used its findings to develop a diverting online tool that lets users compare their biomass to that of people in other nations. (I learned that I have the B.M.I. of your average, middle-aged Eritrean.)
The study, however, did not address possible underlying causes of the ever-growing weight of nations.
But a group of groundbreaking new reports, being published online as a series today in The Lancet, suggest that voluntary physical inactivity, a practice once confined mostly to North America and parts of Europe, is spreading rapidly to the rest of the world and likely contributing materially to global gains in tonnage and declines in health.
Consider the findings of perhaps the most sobering of the new studies, which looked at the extent to which sedentary lifestyles are colonizing the world.