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The Minnesota Semi-Starvation Experiment: What It Teaches Us About Eating Disorders

Ancel Keys - The Minnesota Semi-Starvation Experiment

Written by: Samantha DeCaro, PsyD (she/her)
Director of Clinical Outreach and Education, The Renfrew Center Ancel Keys - The Minnesota Semi-Starvation Experiment

Those with eating disorders frequently experience both medical and psychological symptoms severe enough to impair functioning across various domains. For those who undereat, whether due to a clinical eating disorder or adherence to a prolonged restrictive diet, malnutrition and semi-starvation can be a harmful and usually unintended consequence of insufficient intake.

Some people are surprised to learn that bodies of all weights, shapes and sizes can experience the detrimental and dangerous effects of prolonged restriction1, as our fat stores cannot provide the essential amino acids, nutrients, vitamins, and minerals necessary for a variety of critical bodily functions2.  Our brains alone require 20% of our resting metabolic rate3.

Many eating disorder providers and treatment centers use psychoeducation as part of their treatment approach, and the results of the Minnesota Semi-Starvation Experiment, including the follow-up study 57 years later, have helped many individuals recognize the psychological, cognitive, and behavioral symptoms of a food-deprived brain and body.

Details of the Minnesota Semi-Starvation Experiment 

In 1944, a group of 36 healthy, male, conscientious objectors to World War II volunteered to be in this experiment conducted by physiologist Ancel Keys and his colleagues at the University of Minnesota. The study aimed to examine both the physical and psychological effects of semi-starvation, as well as inform and hopefully improve the process of refeeding and rehabilitating emaciated civilians. The study lasted a year. There was also a 12-week control period, a 24-week semi-starvation period, and finally a 12-week rehabilitation period.

When people hear the word “starvation” or the term “semi-starvation”, many people assume the subjects consumed close to nothing and exercised excessively. Conversely, the calories consumed during this phase were generally more than what many modern-day weight loss diets recommend, reminding us that starvation and malnutrition are not always caused by a complete and total absence of food.

Many folks with eating disorders do indeed eat, sometimes even multiple times a day, which can result in the minimization or complete denial that the person is in any danger. The meal plans in the experiment simulated the type of diet typically consumed during a famine, mainly starches like dark breads, potatoes, macaroni, and root vegetables.

Contrary to popular belief, the men were not required to exercise excessively. In fact, most of the men avoided unnecessary movement whenever possible. The men in the experiment were required to walk, on average, a few miles a day, as well as work in a lab for 15 hours per week (i.e., doing mainly laundry and clerical type work). There was also a treadmill test for 30 minutes per week. The men were permitted to participate in academic and social activities for 25 hours per week. The protocol required the subjects to hit a weekly weight loss goal, and the meal plans were adjusted if any subjects did not lose enough weight or lost weight too rapidly.

The Physical & Psychological Impacts of Semi-Starvation 

All men were deemed mentally and physically healthy prior to the start of the experiment. The men kept detailed journals of their experiences and were tested extensively, both physically and psychologically, in repeated intervals throughout the year. The researchers monitored and tested their blood, lung capacity, bone density, heart, eyesight, strength, coordination, skin, stomach function, movement during sleep, metabolic rates, and much more. They had meetings with a psychologist on a weekly basis and underwent various psychological tests.

The cognitive effects surfaced early in the study and were nearly identical to the experiences commonly reported by those with restrictive eating disorders. For example, the subjects had difficulty thinking clearly and concentrating. They became hyper-focused on and preoccupied with food, recipes, and cooking. They talked excessively about food in conversation and experienced intrusive thoughts about it.  The men even reported dreaming about food. Many noticed a decrease in their motivation, discipline, and effort around any tasks that involved problem solving.

The men engaged in new and abnormal behaviors during meals. Some would mix food together in unusual ways or eat very slowly, comparable to the food rituals frequently observed in eating disorders. Some subjects started hoarding items, stealing things, and collecting recipes and cookbooks. One subject snuck away from the lab, bought ice cream, and engaged in a binge eating episode (he was dismissed from the experiment for deviating from the diet plan). Some subjects found pleasure in observing others eat, while some subjects tried to avoid the sight of it. Many subjects drastically increased their consumption of coffee, chewing gum, and nicotine.

From an emotional and interpersonal standpoint, subjects reported feeling despondent and apathetic. They became increasingly irritable and annoyed with their peers over trivial matters. They compared their meal plans to others and became angry about wasted food.  They became more introverted and reported a lack of interest in the things they once enjoyed, including dating. One subject recalled, “I didn’t feel like smiling…and I never laughed”. Some men even reported feeling guilty for dreaming about food. Those with eating disorders frequently report similar experiences, including feeling depressed, guilty, isolated, and much less interested in matters beyond food and weight.

The men endured various medical complications. Their metabolic rates, and various other bodily processes, slowed down significantly. Subjects reported feeling frequently cold and tired, even having difficulty performing basic activities like climbing stairs or standing up straight. They suffered from edema, including swollen ankles, knees, and faces. The subjects noticed that their strength, endurance, and coordination had markedly diminished. Most of these experiences mirror the medical issues that occur in restrictive eating disorders, regardless of body size or weight.

The Rehabilitation Period 

The men were divided into groups during the rehabilitation period and their intake was finally increased during the refeeding process. Physical healing proved slow and regaining weight took much longer than expected, however depression scores improved the fastest for those consuming the most calories. Many reported they would finish a meal, feel physically full, yet remain extremely hungry. Many of the men also reported feeling out of control with food when they could finally access food and eating abnormally long after the study was completed.

One subject recalled that it took him approximately 3 years to fully heal his relationship with food. These experiences serve as a grim reminder of what we already know as eating disorder providers: prolonged restriction, whether through dieting or a clinical eating disorder, can significantly increase the risk of binge eating or over-eating while damaging our relationship with food for years to come.

The Follow-Up Investigation: 57 Years Later

Nearly 6 decades later, researchers (Eckert, et al., 2018) interviewed 19 subjects (including the data from the video journal of a deceased subject) to explore the possible long-term effects of semi-starvation.  The men accurately recalled many of the physical and psychological symptoms outlined in the study’s results, however some had trouble remembering the depression and irritability. Along the same vein, those in eating disorder recovery sometimes report that it is easier to recall the “good” things about the eating disorder compared to the negative consequences.

The majority of men recalled binge eating or over-eating in the early stages of the re-feeding process; two subjects recalled eating to the point of involuntarily purging and one required hospitalization for gastric distension. The men who binged claimed that they had never engaged in binge eating prior to undergoing this experiment4. All of the men in the follow-up study reported abnormal eating at various points throughout their lives.


The researchers from the follow-up study shared that the participants went on to live “interesting and productive lives”, without any permanent repercussions. They concluded that the mental and physical symptoms eventually reversed due to consistent adequate nutrition and regained weight, despite the numerous complications that surfaced during and long after the study. The results of both studies continue to educate those in eating disorder recovery and offer hope that the refeeding process, however challenging, will provide similar relief to the distressing cognitive, emotional, medical, and behavioral symptoms.

  4. file://ren-fs01/users/sdecaro/Downloads/50-1-499-1-10-20180319%20(2).pdf
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