In The '40s, Scientists Partially Starved 36 Men For 6 Months. They Didn't Expect What Happened Next

World War II and the Cold War were profound periods of scientific discovery. As guided missile technology began, the U.S. military trained pigeons to guide missiles, which laid the groundwork for modern touchscreens. The military ran risky germ warfare experiments on unsuspecting Americans in the 1950s, which may have affected the region's microbial ecology for decades. Since the global conflict meant starvation for millions as well, University of Minnesota (UMN) researchers aimed to learn the physiological and psychological costs of hunger. Among the most surprising changes was how being semi-starved and refed affects people's attitudes and behavior toward food and eating.

In 1944, UMN physiology professor and War Department consultant Ancel Keys led the Minnesota Starvation Experiment. It involved the stringent selection of 36 healthy young men and four study phases — three months of normal eating, six months of semi-starvation (getting about half the calories needed to maintain weight), three months of restricted refeeding, and eight weeks of unrestricted refeeding. Publishing the findings in "Biology of Human Starvation" in 1950, the researchers found that the men suffered several cognitive impairments related to alertness, comprehension, concentration, and judgement. More alarming, though, was how the men's relationship with food changed.

Despite having little interest in food before the experiment, they developed a pre-occupation with food — daydreaming, reading, and talking about it. They struggled to focus on normal activities, and some started collecting kitchen utensils and recipes or even looking through the trash and hoarding. Along with planning how they would eat the rations and mixing unusual foods together (a change in behavior), nearly 40% of them planned to cook after the experiment, and some actually chose food-focused careers afterward.

Of course, experiencing semi-starvation during the UMN experiment resulted in weight loss. The men's body weight dropped an average 25%, which meant that some of them reached a BMI of 14. In the published findings, the researchers noted growing listlessness (lack of energy), tiredness, weakness among them — disadvantages of low BMI that aren't often discussed. The men also progressively reported dizziness, hair loss, headaches, gastrointestinal discomfort, increased cold intolerance, light and noise hypersensitivity, oedema (swollen legs), reduced sleep need and strength, and tingling feet and hands.

Perhaps another unsurprising result was that the men exhibited emotional changes from the semi-starvation, including periods of anxiety, depression, and irritability. They even experienced apathy, with some of them neglecting their personal hygiene. While their emotional responses varied greatly, some of them were severe. These changes didn't revert right away when the food supply was increased, leading to the theory that they were related to body weight rather than food intake. As a result, the researchers concluded that the same is the case for those with anorexia and bulimia nervosa disorders, which is why the experiment is often cited in related research.

The social and sexual changes, however, may have been more unexpected. Although the men were rather outgoing when they entered the semi-starvation experiment, they became more isolated and withdrawn over time. These changes manifested as a reluctance to plan and participate in any activities. As they felt more and more socially inadequate, they also began to lose their senses of comradeship and humor. On top of that, the men's contact with women sharply declined, and their relationships became strained. Some of them lost interest in intimacy, too. These social changes virtually returned for all of the men after eight months.