In 2004, while on the faculty of the math department at the University of Pittsburgh, I married. My wife is a Johns Hopkins ophthalmologist, and she would not move. So I began looking for work in the Beltway area. Through the grapevine, I heard that the N.I.D.D.K., a branch of the National Institutes of Health, was building up its mathematics laboratory to study obesity. At the time, I knew almost nothing of obesity.
I didn’t even know what a calorie was. I quickly read every scientific paper I could get my hands on.
I could see the facts on the epidemic were quite astounding. Between 1975 and 2005, the average weight of Americans had increased by about 20 pounds. Since the 1970s, the national obesity rate had jumped from around 20 percent to over 30 percent.