Elizabeth Kolbert in The New Yorker:
Men are now on average seventeen pounds heavier than they were in the late seventies, and for women that figure is even higher: nineteen pounds. The proportion of overweight children, age six to eleven, has more than doubled, while the proportion of overweight adolescents, age twelve to nineteen, has more than tripled. (According to the standards of the United States military, forty per cent of young women and twenty-five per cent of young men weigh too much to enlist.) As the average person became heavier, the very heavy became heavier still; more than twelve million Americans now have a body-mass index greater than forty, which, for someone who is five feet nine, entails weighing more than two hundred and seventy pounds. Hospitals have had to buy special wheelchairs and operating tables to accommodate the obese, and revolving doors have had to be widened—the typical door went from about ten feet to about twelve feet across. An Indiana company called Goliath Casket has begun offering triple-wide coffins with reinforced hinges that can hold up to eleven hundred pounds. It has been estimated that Americans’ extra bulk costs the airlines a quarter of a billion dollars’ worth of jet fuel annually.
Such a broad social development seems to require an explanation on the same scale. Something big must have changed in America to cause so many people to gain so much weight so quickly. But what, exactly, is unclear—a mystery batter-dipped in an enigma.