“One general feature of the post-experimental history,” the Carnegie researchers reported, “is the excess eating immediately indulged in by the men.” Despite repeated cautions about the dangers of overindulgence after such a strict diet, the men “almost invariably over-ate.” As the Carnegie report put it, “the circumstances militated against” any acquisition of “new dietetic habits.” In particular, the cravings for “sweets and accessory foods of all kinds,”—i.e., snacks—were now free to be indulged, and so they were. Perhaps for this reason, Benedict’s young subjects managed to regain all the lost weight and body fat in less than two weeks. Within another three weeks, they had gained, on average, eight pounds more, and came out of this exercise in calorie restriction considerably heavier than they went in. “In practically every instance the weight prior to the beginning of the experiment was reached almost immediately and was usually materially exceeded,” Benedict and his collagues wrote.

In 1944, Ancel Keys and his colleagues at the University of Minnesota set out to replicate Benedict’s experiment, although with more restrictive diets and for a greater duration. Their goal was to reproduce and then study the physiological and psychological effects of starvation of the kind that Allied troops would likely confront throughout Europe as the continent was liberated. Thirty-two young male conscientious objectors would serve as “guinea pigs,” the phrase Keys used in this context. These volunteers would eventually spend twenty-four weeks on a “semi-starvation diet,” followed by another twelve to twenty weeks of rehabilitation.

The subjects consumed an average of 1,570 calories each day, split between two meals designed to represent the daily fare of European famine areas. “The major food items served,” the researchers noted, “were whole-wheat bread, potatoes, cereals, and considerable amounts of turnips and cabbage. Only token amounts of meats and dairy products were provided.”*75 This diet provided roughly half the calories that the subjects had been consuming to maintain their weight. It was expected to induce an average weight loss of 20 percent—or forty pounds in a two-hundred-pounder—aided by a routine that required the subjects to walk five to six miles each day, which would burn off another two to three hundred calories.