“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.
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,
Eventually, five of the subjects succumbed to what Keys and his colleagues called “character neurosis,” to be distinguished from the “semi-starvation neurosis” that all the subjects experienced; in two cases, it “bordered on a psychosis.” One subject failed to lose weight at the expected rate, and by week three was suspected of cheating on the diet. In week eight, he binged on sundaes, milk shakes, and penny candies, broke down “weeping, [with] talk of suicide and threats of violence,” and was committed to the psychiatric ward at the University Hospital. Another subject lasted until week seven, when “he suffered a sudden ‘complete loss of willpower’ and ate several cookies, a bag of popcorn, and two overripe bananas before he could ‘regain control’ of himself.” A third subject took to chewing forty packs of gum a day. Since his weight failed to drop significantly “in spite of drastic cuts in his diet,” he was dropped from the study. For months afterward, “his neurotic manifestations continued in full force.” A fifth subject also failed to lose weight, was suspected of cheating, and was dropped from the study.
With the relaxation of dietary restriction, Keys avoided the dietary overindulgence problem that had beset Benedict’s subjects by restricting the rehabilitation diets to less than three thousand calories. Hunger remained unappeased, however. For many of the subjects, the depression deepened during this rehabilitation period. It was in the very first week of rehabilitation, for instance, that yet another subject cracked—his “personality deterioration culminated in two attempts at self-mutilation.”
Even during the last weeks of the Minnesota experiment, when the subjects were finally allowed to eat to their hearts’ content, they remained perversely unsatisfied. Their food intake rose to “the prodigious level of 8,000 calories a day.” But many subjects insisted that they were still hungry, “though incapable of ingesting more food.” And, once again, the men regained weight and body fat with remarkable rapidity. By the end of the rehabilitation period, the subjects had added an average of ten pounds of fat to their pre-experiment levels. They weighed 5 percent more than they had when they arrived in Minneapolis the year before; they had 50 percent more body fat.
These two experiments were the most meticulous ever performed on the effects on body and mind of long-term low-calorie diets and weight reduction. The subjects were selected to represent a range of physiological types from lean to overweight (albeit all young, male, and Caucasian). They were also chosen for a certain strength of character, suggesting they could be trusted to follow the diets and remain dedicated to the scientific goals at hand.
The diets may seem severe in the retelling, but, in fact, fourteen to sixteen hundred calories a day for weight loss could be considered generous compared with the eight-to-twelve-hundred-calorie diets that are now commonly prescribed, what the 1998
In both experiments, even after the subjects lost weight and were merely trying to maintain that loss, they were still required to eat considerably fewer calories than they would have preferred, and were still beset by what Keys and his colleagues had called the “persistent clamor of hunger.” Of equal importance, simply restraining their appetites, independent of weight loss, resulted in a dramatic reduction in energy expenditure. This could be reversed by adding calories back into the diet, but then any weight or fat lost returned as well. One lesson learned was that, for the weight reduction to be permanent, some degree of semi-starvation has to be permanent. These experiments indicated that would never be easy.
Obese patients also get hungry on semi-starvation diets. If they have to restrict their calories to lose weight, then by definition they are forcing themselves to eat less than they would otherwise prefer. Their hunger is not being satisfied. As with lean subjects, their energy expenditure on a semi-starvation diet also “diminishes proportionately much more than the weight,” as the Pittsburgh clinician Frank Evans reported in 1929 of his obese subjects. This same observation was reported in 1969 by George Bray, who was then at the Tufts University School
