Living as we do in the “low-carb nation”—where, despite the gospel according to Atkins, obesity rates are escalating—it’s easy to forget that as recently as the 1930s many Americans worried about eating too little, not too much.

Yale medical historian Susan E. Lederer, Ph.D., sees the end of World War II as a turning point. Until then, scarcity dominated people’s anxieties. Now, we worry about the effects of abundance on our bodies. Given her scholarly perspective, you’d think Lederer might have anticipated that even her daughter might be affected by “an ideal [of thinness] that virtually no one can achieve.” But when five-year-old Emma declined to sample a Flintstones vitamin after seeing a picture of a chubby baby Pebbles (“It’s going to make me fat.”), Lederer recalls, “I was really kind of stunned.”

That incident, in part, inspired the associate professor of the history of medicine to offer a course at Yale College called “Fat and Thin: A History of American Bodies.” Lederer expected 50 to 75 students, and she ended up with 358. She had to expand her team of teaching fellows from two to nine.

The course, offered last spring, surveyed the evolution since Colonial times of notions of nutrition, food choices and ideal body weight, and how both scarcity and plenty can mark the body. The story began with scarcity. Although Native Americans had developed strategies to avoid famine, by following food or by storing it, European newcomers arrived unprepared. In a 1607 diary entry, Jamestown settler Master George Percy describes his group’s reprieve from hunger: “It pleased God, after a while, to send those people which were our mortall enemies to releeve us with victuals, as Bread, Corne, Fish and Flesh in great plentie. … Otherwise we had all perished.” During the winter of 1609-1610, 80 percent of the James-town settlers did perish, of starvation and sickness.

Three centuries later, Lederer’s students learned, scarcity still marked the bodies of Americans. In the South, prisoners and orphans suffered from “the four D’s” of pellagra—dermatitis, diarrhea, dementia and death. U.S. Public Health Service physician Joseph Goldberger, M.D., set out to prove that pellagra resulted from their cornmeal-based diet. In his 1915 Rankin prison farm experiment, he induced pellagra in convicts in return for clemency. (Except for one protest, the only objection to this experiment came from those who were upset that convicts in prison for serious crimes were released in return for their participation.) Even then, he failed to convince detractors that the disease was caused by a diet deficient in niacin, not by microbes.

The contemporary obesity epidemic derives in part from the plethora of manufactured snacks, says Lederer. In the 1920s, she notes, ready-made snacks were few: popcorn, Graham crackers, biscuits, penny candy. “Now we have more food choices than anyone else on the planet, and we’re so conflicted over them,” she says. When researchers asked people what they associate with a slice of double-chocolate cake, French respondents said “Celebration.” Americans said “Guilt.”

A study of 2,600 elementary school children in New York City, reported by the city’s health department in 2004, found that 40 percent were overweight, and one in four was obese. Hispanic children were most likely to be overweight and Asian students were least likely.

Among Yale students, Lederer says, “There’s a lot of interest in bodies,” especially among athletes. Twenty-five women from the Yale track team enrolled in the course, along with football player Nate Lawrie, a senior who was drafted by the Tampa Bay Buccaneers last spring. The caption next to Lawrie’s photo on the team’s website reads: “TE Nate Lawrie has the frame to add weight without sacrificing speed.”

For historical perspective on obesity, Lederer uses a cartoon from The New Yorker. Two witches watch as a plump boy and girl walk by the witches’ candy-festooned gingerbread cottage. One witch asks the other: “Remember when we used to have to fatten the kids up first?”