In the 30-plus years that Richard Atkinson has been studying obesity, he has always maintained that overeating doesn’t really explain it all. His epiphany came early in his career, when he was a medical fellow at U.C.L.A. engaged in a study of people who weighed more than 300 pounds and had come in for obesity surgery. “The general thought at the time was that fat people ate too much,” Atkinson, now at Virginia Commonwealth University, told me recently. “And we documented that fat people do eat too much — our subjects ate an average of 6,700 calories a day. But...
