But nothing is simple in food and nutrition, Hager, the Nestlé geneticist, told me. He thinks of diets like medicine. They work only for some people, some of the time. I asked him for his view on what caused so many people to start overeating back in the eighties. “The simple answer is that obesity is energy in, versus energy out,” he said. “If you get more energy in than you expend, you gain weight, and so obesity is a consequence of a sedentary lifestyle, and the very, very easy availability of cheap food.”
