Overall weight gain since 1960 is slightly greater for women (18.5 percent) than for men (17.6 percent). And both sexes have gained roughly an inch in height over the same period, which accounts for some of that weight gain.
But story is mostly one of growing girth, and it basically boils down to three factors: we're eating less healthy food, we're eating more of it, and we're not moving around as much. According to a study published in 2012 in the journal BMC Public Health, Americans are now the world's third-heaviest people, behind only the Pacific island nations of Tonga and Micronesia.
The average American is 33 pounds heavier than the average Frenchman, 40 pounds heavier than the average Japanese citizen, and a whopping 70 pounds heavier than the average citizen of Bangladesh. To add up to one ton of total mass, it takes 20 Bangladeshis but only 12.2 Americans.
Together, the world's adult human beings added up to 287 million tons of biomass in 2005, according to the BMC Public Health study. But if every country had the same weight distribution as the U.S., the world would be 58 million tons fatter, an increase of 20 percent.
The study concludes that "tackling population fatness may be critical to world food security and ecological sustainability." And as with so many of the world's problems, the solutions start at home -- on the bathroom scale in this case. But boy, those donuts sure do look delicious.