The mystery is not the modest increase of obesity from 1890 to 1975. This increase is very likely caused by reduced activity and increased caloric consumption.

The mystery is not the modest increase of obesity from 1890 to 1975. This increase is very likely caused by reduced activity and increased caloric consumption. It is the dramatic increase in obesity from around 1980 and onward that is a mystery. And part of the mystery is that animals living around humans, in the wild or in the lab, seems to have gone through a similar increase in body weight. The article goes through why this dramatic increase can not just be due to reduced exercise or increased caloric consumption, but must have some other, unknown factors, to explain it.