Why are people around the world so much fatter today than ever before in human history? Is it because they’re eating more, or eating more bad food, and not exercising? That’s true for some people, but David Berreby, surveying the latest scientific literature, says gluttony cannot explain it all. Excerpt:

Yet the scientists who study the biochemistry of fat and the epidemiologists who track weight trends are not nearly as unanimous as Bloomberg makes out. In fact, many researchers believe that personal gluttony and laziness cannot be the entire explanation for humanity’s global weight gain. Which means, of course, that they think at least some of the official focus on personal conduct is a waste of time and money. As Richard L Atkinson, Emeritus Professor of Medicine and Nutritional Sciences at the University of Wisconsin and editor of the International Journal of Obesity, put it in 2005: ‘The previous belief of many lay people and health professionals that obesity is simply the result of a lack of willpower and an inability to discipline eating habits is no longer defensible.’

More:

Consider, for example, this troublesome fact, reported in 2010 by the biostatistician David B Allison and his co-authors at the University of Alabama in Birmingham: over the past 20 years or more, as the American people were getting fatter, so were America’s marmosets. As were laboratory macaques, chimpanzees, vervet monkeys and mice, as well as domestic dogs, domestic cats, and domestic and feral rats from both rural and urban areas. In fact, the researchers examined records on those eight species and found that average weight for every one had increased. The marmosets gained an average of nine per cent per decade. Lab mice gained about 11 per cent per decade. Chimps, for some reason, are doing especially badly: their average body weight had risen 35 per cent per decade. Allison, who had been hearing about an unexplained rise in the average weight of lab animals, was nonetheless surprised by the consistency across so many species. ‘Virtually in every population of animals we looked at, that met our criteria, there was the same upward trend,’ he told me.

It isn’t hard to imagine that people who are eating more themselves are giving more to their spoiled pets, or leaving sweeter, fattier garbage for street cats and rodents. But such results don’t explain why the weight gain is also occurring in species that human beings don’t pamper, such as animals in labs, whose diets are strictly controlled. In fact, lab animals’ lives are so precisely watched and measured that the researchers can rule out accidental human influence: records show those creatures gained weight over decades without any significant change in their diet or activities. Obviously, if animals are getting heavier along with us, it can’t just be that they’re eating more Snickers bars and driving to work most days. On the contrary, the trend suggests some widely shared cause, beyond the control of individuals, which is contributing to obesity across many species.

Berreby goes on to look at various theories of why this is happening. I had no idea it was occurring in animals too. Did you?

In last week’s issue of The New Yorker, Meghan O’Rourke writes about her devastating struggle with autoimmune disease. It’s not available to link to non-subscribers, but as soon as the magazine frees it up, I’ll post a link on this blog. O’Rourke writes that scientists are observing an epidemic of autoimmune disease in the industrial world. By some counts, it has risen fourfold in the past 40 years — much higher than can be accounted for by better diagnostic techniques. Last week I went to see my doctor for a bronchial infection, and mentioned to him the O’Rourke piece. He told me that he’s been seeing a lot more autoimmune disorders in his patients. FWIW…

[H/T: Turmarion]