Keys’s conscientious objectors lost, on average, a dozen pounds of fat in the first twelve weeks of semi-starvation, which constituted more than half of their original fat tissue, and they lost three more pounds of body fat by the end of twenty-four weeks. But weight loss, once again, was not the only physiological response to the diet. Nails grew slowly, and hair fell out. If the men cut themselves shaving, they would bleed less than expected, and take longer to heal. Pulse rates were markedly reduced, as was the resting or basal metabolism, which is the energy expended by the body at rest, twelve to eighteen hours after the last meal. Reflexes slowed, as did most voluntary movements: “As starvation progressed, fewer and fewer things could stimulate the men to overt action. They described their increasing weakness, loss of ambition, narrowing of interests, depression, irritability, and loss of libido as a pattern characteristic of ‘growing old.’” And, like Benedict’s subjects, the young men of the Minnesota experiment complained persistently of being cold. Keys’s conscientious objectors reduced their total energy expenditure by over half in response to a diet that gave them only half as many calories as they would have preferred. This was a reasonable response to calorie deprivation, as Keys and his colleagues explained, “in the sense that a wise man reduces his expenditure when his income is cut.”

More than fifty pages of the two-volume final report by Keys and his colleagues, The Biology of Human Starvation, document the “behavior and complaints” induced by the constant and ravenous hunger that obsessed the subjects. Food quickly became the subject of conversations and daydreams. The men compulsively collected recipes and studied cookbooks. They chewed gum and drank coffee and water to excess; they watered down their soups to make them last. The anticipation of being fed made the hunger worse. The subjects came to dread waiting in line for their meals and threw tantrums when the cafeteria staff seemed slow. Two months into the semi-starvation period, a buddy system was initiated, because the subjects could no longer be trusted to leave the laboratory without breaking their diets.