We all know — because we are being constantly reminded — that we are, collectively, getting fat. Americans are at the forefront of the trend, but it is a transnational one. Apparently, it is also transspecies: pets, wild animals, and laboratory animals are also gaining weight. Here’s some country-level data from the New York Times:

In an excellent review of the existing literature, David Berreby at Aeon skewers the idea that a simple, victim-blaming “calories in, calories out” model can explain this extraordinary transnational, transspecies rise in overweight and obese individuals. I won’t summarize his argument here, except to simply list the casual contenders for which there is good evidence:

Sleeplessness

Stress

Viruses

Bacteria

Industrial chemicals

Heavy metals

Electric lights

Air conditioning

Famine in previous generations

If you ever want to have an opinion on fat again, read Berreby now.