The Hidden Lessons of the Minnesota Starvation Experiment and Its Impact on Modern Nutrition

"The Minnesota Starvation Experiment"

Introduction

“They starved so that others be better fed.” With these stark words, the University of Minnesota recruited 36 young men in 1944 for one of the most unusual and consequential medical studies ever undertaken. The Minnesota Starvation Experiment, led by physiologist Ancel Keys, asked volunteers to endure months of semi-starvation not for their own benefit, but to answer a pressing humanitarian question: how can the millions of people left starving by World War II be fed back to health? Minnesota starvation experiment and modern nutrition

Historical Background

By 1944, Allied leaders faced a grim reality. Vast regions of Europe and Asia were devastated, with food shortages threatening the survival of entire populations. Relief workers and policymakers lacked even basic scientific guidance: how much food did the starving need? How quickly could they be rehabilitated? What dangers might lie in refeeding too quickly? Ancel Keys, already known for his work on nutrition and physiology, believed that science had a duty to answer these questions. With support from the U.S. government, he launched a study at the University of Minnesota. Recruitment focused on conscientious objectors—men who, because of their pacifist beliefs, refused to bear arms but sought another way to serve. More than 400 volunteered. After rigorous screening, 36 were chosen to become both the subjects and of a study that would test the limits of the human body and mind.

The Volunteers

The men who stepped forward were mostly from Mennonite, Quaker, and Brethren communities. They wanted their wartime service to reflect their values: nonviolence, compassion, and sacrifice. Participation was grueling, but many later said it was one of the most meaningful choices of their lives. These volunteers lived in a controlled environment on campus. They kept journals, took university courses, and engaged in daily chores. Their mission was to embody, in microcosm, the struggle that millions overseas were enduring involuntarily.

Study Design

The experiment unfolded in three main stages:

• Control Phase (12 weeks): Participants consumed about 3,200 calories a day. Researchers measured their physical fitness, mental health, and metabolism to establish a baseline.

• Semi-Starvation Phase (24 weeks): Calories were cut in half, to about 1,560–1,800 per day, designed to induce a 25% weight loss (averaging 16.5 kg or 37 lbs). Their diet consisted mainly of starchy carbohydrates like potatoes, rutabagas, turnips, bread, and macaroni—foods similar to what famine-struck populations might eat, with minimal protein and fat. Physical activity remained constant, including about 22 miles of walking per week, creating a significant energy deficit (often over 1,000 calories daily).

• Rehabilitation Phase (12+ weeks): Different groups received carefully planned increases in food. Some were given an extra 400 calories daily, others up to 1,600, while a subset was permitted unrestricted eating. Researchers tracked how their bodies and minds responded to refeeding.

The Toll of Starvation

The effects were profound and disturbing. On average, the men lost 19–28% of their body weight, including approximately 70% of their initial fat mass and 40% of their initial muscle mass.

They grew gaunt, weak, and cold. Muscles atrophied, heart rates slowed, respiration and body temperature decreased, and fatigue became constant. Edema caused swelling in their ankles and faces, while other physical symptoms included hair loss, dry skin, dizziness, headaches, anemia, neurological deficits, and gastrointestinal discomfort.

Equally striking were the psychological and behavioral changes. The men became obsessed with food, poring over cookbooks, hoarding recipes, talking endlessly about meals, and exhibiting abnormal eating behaviors like plate licking, diluting food with water, or chewing gum excessively. Their moods darkened: depression, anxiety, irritability, and social withdrawal were common. Some experienced body dysmorphia, perceiving others as “too fat” rather than themselves as too thin. Reduced libido and severe emotional distress were reported, with one participant, Sam Legg, resorting to self-harm by amputating three fingers.

The study’s diet, high in carbohydrates (likely 60–80% of calories) and low in protein (possibly as low as 20 g/day, compared to ~100 g/day in the control phase) and fat, reflected wartime scarcity. Example meals included a small bowl of farina, two slices of toast, fried potatoes, jello, jam, and a small glass of milk, or cabbage, turnips, rye bread, or beans. While the study wasn’t designed to isolate calorie restriction from nutrient deficiencies, we can infer their contributions:

• Calorie Restriction: The severe energy deficit drove metabolic adaptation, including a 40% reduction in basal metabolic rate (BMR) to conserve energy, leading to weight loss, fatigue, weakness, reduced heart rate, and cold intolerance. Psychological effects like depression, anxiety, and food preoccupation stemmed from disrupted brain chemistry, with lower serotonin and dopamine levels—similar to patterns in eating disorders like anorexia nervosa. Edema could also partially result from metabolic stress.

• Protein Deficiency: Low protein exacerbated muscle wasting (due to amino acid deficiency), edema (via reduced albumin levels), hair loss and dry skin (due to inadequate proteins like keratin), and possibly anemia (limiting hemoglobin synthesis, though micronutrient shortages also contributed).

• Combined Effects: Symptoms like neurological deficits and gastrointestinal issues likely arose from both energy and protein deficits, with calorie restriction impairing function and low protein limiting enzyme and neurotransmitter production. Minimal fat likely contributed to hormonal imbalances, such as reduced libido.

The Challenge of Refeeding

When semi-starvation ended, researchers faced unexpected challenges. Some men ate until they vomited or needed medical intervention. Others consumed up to 10,000–11,500 calories a day without feeling satisfied, with hunger persisting until fat stores were largely replenished. In the 12-week restricted rehabilitation phase, participants received additional calories (400, 800, 1,200, or 1,600) with varying protein and vitamin supplements. Recovery was slow, but fastest in higher-calorie groups, regardless of protein levels, suggesting calorie restriction was the dominant factor. Ancel Keys concluded that “unless calories are abundant, then extra proteins, vitamins, and minerals are of little value.” In the 8-week unrestricted phase, the emphasis on caloric abundance (4,000+ calories/day) further highlighted the primacy of energy deficit over specific nutrient shortfalls.

Connection to Modern Dieting

The Minnesota Starvation Experiment offers striking parallels to modern dieting, particularly low-calorie, including hypo-caloric low-carbohydrate diets, which often replicate the psychological and physical effects observed in the study. The experiment’s participants, consuming 1,560–1,800 calories daily, experienced food obsession, depression, irritability, and social withdrawal—symptoms mirrored in today’s dieters on severely calorie-restricted regimens, whether high or low in carbohydrates. The fixation on food, such as poring over recipes or fantasizing about meals, is a common experience among those on restrictive diets, as the brain prioritizes energy acquisition during perceived scarcity. This is evident even in calorie restricted ketogenic diets, where some clients report heightened food cravings or preoccupation despite ketosis, which has appetite-suppressing effects due to ketone production.

Ketogenic diets, which are low in carbohydrates but much higher in fat and in most cases also in protein than the experiment’s starchy diet, may mitigate some effects (e.g., less muscle loss due to higher protein intake and ketones’ muscle-sparing potential). However, when these diets are severely calorie-restricted, the mental toll—depression, anxiety, and irritability—persists, as the brain’s energy deficit disrupts neurotransmitter balance, much like in the study. Clients in the ketogenic space often describe feeling “foggy” or emotionally volatile when calories are too low, underscoring that energy availability, not just macronutrient composition, drives these outcomes.

The experiment’s refeeding phase also resonates with modern weight regain patterns. Participants regained more fat than muscle, as the body prioritized fat storage to restore energy reserves, a phenomenon seen in “yo-yo” dieting. The study found that hunger persisted until participants approached their pre-starvation fat mass levels, suggesting that the body’s drive to restore fat stores, rather than muscle, fueled overeating (up to 10,000+ calories daily). However, a modern hypothesis suggests that some dieters may overeat until they regain lost muscle mass, which is harder to rebuild due to the need for adequate protein (1.6–2.2 g/kg body weight), resistance training, and a controlled caloric surplus. Because muscle regain is slower and more complex than fat storage, prolonged overeating to restore muscle can lead to excess fat accumulation, as excess calories are preferentially stored as fat. In the Minnesota study, muscle recovery lagged behind fat regain, and the lack of exercise or high-protein diets during refeeding meant that participants regained a higher proportion of fat, mirroring challenges faced by modern dieters.

The study’s findings highlight the risks of severe calorie restriction, regardless of diet type. While ketones may offer neuroprotection and appetite suppression in ketogenic diets, severe energy deficits still trigger psychological distress and physical symptoms like fatigue or hair loss, as seen in the experiment. These insights emphasize the need for balanced, sustainable approaches to weight loss, incorporating adequate calories, protein, and exercise to minimize metabolic and mental harm, and caution against extreme restriction that echoes the starvation conditions of the 1940s.

Legacy and Impact

The results were published in 1950 in the monumental two-volume work The Biology of Human Starvation. It became the foundational reference for humanitarian organizations and governments managing famine relief. Early findings were shared with aid groups even before publication to guide efforts in Europe and Asia. The experiment’s observations continue to inform eating disorder treatment, showing that symptoms like food obsession, depression, and social withdrawal stem from starvation itself, not character flaws. It also deepened awareness of refeeding syndrome, a dangerous metabolic complication when nourishment is reintroduced too rapidly. While ethical constraints prevent modern replication, the study remains a cornerstone for understanding protein-energy malnutrition.

Voices from the Experiment

The participants’ own words vividly capture the toll and purpose of their sacrifice. Marshall Sutton, a Quaker, described the physical and emotional numbness: “After you’ve not had food for a while your state of being is just numb. I didn’t have any pain. I was just very weak. One’s sexual desires disappeared.” He also reflected on emotional volatility: “When something good happened, we would explode with joy and when we were pessimistic we were very depressed. I had a very close friend there and often I’d speak sharply to him and I’d find myself going to him almost every night and apologizing.” Sam Legg, who resorted to self-harm, admitted, “I’m not ready to say I did it on purpose. I’m not ready to say I didn’t,” revealing the psychological turmoil of starvation. Roscoe Hinkle found recovery challenging: “Rehabilitation turned out to be worse for me than anything else. I had troubles because I didn’t really feel that I was coming back at all.” Max Kampelman, reflecting in 1993, framed their participation as a moral duty: “Why do people who were drafted go to fight wars, without escaping? Because there’s a duty. It’s the same kind of a thing, just a different battlefield.” Another participant noted, “Food became the most important, if not the only, thing in his life, reflecting that this also makes life pretty dull.” Decades later, many insisted they would volunteer again, viewing their suffering as a small price to pay for relieving global hunger. Several pursued careers in humanitarian work, education, diplomacy, and service, continuing their ethic of contribution.

Conclusion

The Minnesota Starvation Experiment remains a landmark in both science and ethics. It reminds us that knowledge often comes at a human cost, and that acts of sacrifice can ripple outward for generations. Above all, it underscores a sobering truth Ancel Keys emphasized: hunger is not just a biological state but a profound social and political crisis. The 36 men who starved in Minnesota did so willingly, believing their suffering might ease the suffering of millions. Their story endures as both a scientific milestone and a testament to human solidarity.

References

1. Keys, A., Brožek, J., Henschel, A., Mickelsen, O., & Taylor, H. L. (1950). The Biology of Human Starvation(Vols. 1–2). University of Minnesota Press.

2. Tucker, T. (2006). The Great Starvation Experiment: The Heroic Men Who Starved So That Millions Could Live. Free Press.

3. Kalm, L. M., & Semba, R. D. (2005). They Starved So That Others Be Better Fed: Remembering Ancel Keys and the Minnesota Experiment. The Journal of Nutrition, 135(6), 1347–1352.

4. University of Minnesota, Laboratory of Physiological Hygiene. (1946). Human Starvation and Its Consequences. Journal of the American Dietetic Association, 22, 860–864.

5. Minnesota Starvation Experiment participant interviews, as cited in “The Starvation Experiment,” American Experience, PBS, 2003. Available at: https://www.pbs.org/wgbh/americanexperience/.