It's that time of the year when a middle-aged person's fancy turns to treadmills and diets. Scientific literature on excess weight and health is expanding along with global waistlines, and yet, it's hard to find a solid, coherent scientific explanation for why some people get fat and others don't, and why some overweight people get Type 2 diabetes and heart disease and others don't.
Beliefs about fat often follow a science-y sounding quasi-religious narrative: Our prehistoric ancestors had to scramble for food, and therefore evolved voracious appetites that we've inherited like original sin. Only self-control can save us, and the association between fat and disease goes without question; it is seen as punishment for the sins of gluttony and sloth.
This narrative acknowledges evolution, but it's not real evolutionary biology. This month, however, a real evolutionary biologist published a sweeping picture of human fat and health in the Proceedings of the National Academy of Sciences.