In the Winter of 1944, World War II was ending and there were horrific stories of widespread starvation across Europe. The American government would soon be responsible for a massive refeeding project overseas, but there were no medical guidelines for how this should be done. Ancel Keys, a professor of physiology at the University of Minnesota, had been involved at the start of the war in the development of field rations for the American military. Now he was asked to design a study that could provide data to guide the refeeding project. Thirty-six men volunteered to participate in a year-long study of starvation. These men were all conscientious objectors who were allowed to participate in human performance studies as an alternative to military service.

During the first three months of the study, each participant was fed a tightly controlled diet intended to standardize his weight to match the average for American men of his height. Most needed to gain a fair amount. After the three-month standardization phase, during which the volunteers’ three daily meals totaled about 3200 calories, the six-month starvation phase of the experiment began. In a single day, the men’s calorie allotment was cut approximately in half.

To put this in context, if an adult male today asks for guidance about going on a quick yet still safe way to lose weight without medical supervision, the recommendation would be to limit his daily intake to 1500 calories. That’s low but is still considered safe and nutritionally adequate. For a woman, that number would be 1200 calories a day. In contrast, to reproduce the effects of involuntary starvation, the average number of calories allowed in the Minnesota experiment was 1570 per day—more than many dieters would now be advised to eat on a non-medically supervised weight-loss regimen!

This made me wonder about the more restrictive dieters who I see in therapy. Although it’s considered a medically safe level of intake, what are the psychological consequences of such a diet? How might it affect adherence when meals aren’t being carefully controlled as they were in the experiment? After losing weight on such a diet does eating just return to normal? What are the long-term effects of this kind of self-deprivation on the body’s metabolism afterward?

In the starvation experiment, the psychological effects of the diet began quickly and soon became dramatic. After just a few weeks, volunteers who kept diaries began to describe how the time between meals had become difficult. One participant began to have nightmares about cannibalism—dreaming that he was the cannibal. This affected that volunteer’s adherence to the routine as well. In an effort to end these dreams, he began cheating on the diet. During their unsupervised free time, he began to leave the university campus where the experiment was being held, to go into the nearby town where he would buy milkshakes and ice cream. The cheating was quickly discovered because his expected weight loss had leveled off. But even after he was caught and his freedom to leave campus was taken away, he found other ways to cheat on the diet and he was soon released from the experiment.

Although this was the earliest psychological reaction among the participants, the others soon began to show signs of abnormal food preoccupation as well. One notable incident occurred when Dr. Keys, the director of the experiment, decided to offer a “relief” meal to the group in order to boost morale and hopefully prevent others from cheating. The calorie content of this meal was considerably more generous than the typical ration, and it included an orange for dessert. When the men finished eating and they were ready to return their trays, nothing was left but the silverware, plates, used napkins, and orange peels. As Todd Tucker described the scene in his book, The Great Starvation Experiment, “None of them could bring themselves to throw it away. The idea came to them collectively. They picked up the orange peel and ate it, every one of them.” Keep in mind that this was after a relief meal of 2,366 calories, after fifteen weeks at the starvation level. The impulse to eat orange peels was not borne of hunger, but psychological scarcity.

As the days wore on, there were more incidents of cheating. Another person was dropped from the experiment when, alone at his night job in a grocery store in town, he suddenly found himself binging on stale cookies and rotten bananas that he was about to throw into the dumpster. Another had to fight the urge to root through a trashcan full of decaying garbage while on his daily walk.

Although the purpose of the experiment was to learn how to safely refeed starving civilians, the volunteers’ stories also highlight important lessons about the effects of dieting on the mind and body.  The key lesson is that even restricting food to a degree that might be considered reasonable for a normal weight-loss diet, can have profound psychological and behavioral effects. It’s worth taking that into account if you’re thinking about starting–or recommending–a diet.