The Minnesota Starvation Experiment: What It Teaches Us About Eating Disorders
- Talia Cecchele
- May 26
- 9 min read
Written by Talia Cecchele, Highly Specialist Dietitian and TCN Founder
If you have been following the learning hub for some time, you may have previously read our post on starvation syndrome, one of the most common topics I talk about with clients in the TC Nutrition Clinic. And if you caught the latest episode of our podcast, Food is Food, you'll know that I dug deep into the research on this recently.
In that episode, I talk through the Minnesota Starvation Experiment (also known as the Ancel Keys Study) and am quite vulnerable in admitting that for over a decade working as an eating disorder dietitian, I wasn't aware that there was a 4th phase of the study. And it is an important one!
This blog is an updated version of our original starvation syndrome post, with new information from recent reviews and interviews from the study participants and further insight into the final phase of the experiment.
This Minnesota Experiment experiment is one of the most comprehensive bodies of evidence we have on what happens to the human body and mind when going through a prolonged period of undernutrition. For ethical reasons, it cannot be replicated in the same way today. There have been recent studies that have researched the impact of reduced energy intake, particularly in military settings, however this is not at the same scale or duration as the Minnesota Experiment.
What Is the Minnesota Starvation Experiment?
The Minnesota Starvation Experiment took place during World War II, led by researcher Ancel Keys at the University of Minnesota. At the time, populations across the globe were facing famine and food scarcity due to wartime rationing, and Keys wanted to understand the physical and psychological impact of semi-starvation and how to safely rehabilitate those affected.
Thirty-six young men, all conscientious objectors, volunteered to live on site at the University of Minnesota for almost a year. All participants were Caucasian males (an important limitation of the study) and were required to be single and have good physical and mental health
The Four Phases of the Study
Phase One: The Control Period (12 weeks)
During the first 12 weeks, the men underwent many physical and psychological tests, to form baseline data for the rest of the experiment. They needed to maintain their weight, and so were given an individualised diet which was reviewed regularly to ensure that they were receiving enough energy. On average, the men were consuming between 3,200–3,500 calories per day.
The diet reflected the foods available in wartime Europe, mainly cabbage, potatoes, pasta, and small amounts of meat and dairy.
The men were also required required to engage in around 25 hours per week of occupational or educational activity, plus 35km of walking per week.
Phase Two: The Semi-Starvation Period (24 weeks)
Overnight, the men's calorie intake was cut by 50% (around 1,600 calories per day). Each week, intake was reviewed and adjusted (either decreased or increased) to ensure participants were losing approximately one kilogram per week, in line with the target of a 25% reduction in body weight over the six month semi-starvation period.
Throughout this phase, the researchers observed many changes, which help us to understand the interplay between undereating and eating disorder presentations. We can summarise the changes in three categories:
Physical changes:
Significant reduction in heart muscle mass, leading to a low heart rate
Up to a 40% reduction in basal metabolic rate (the energy the body uses at rest).
Decreased tolerance to cold (many men asked for extra blankets at night)
Fatigue, dizziness, hair loss and dry skin
Reduced frequency of bowel movements, with some men experiencing a change to one bowel movement per week
Oedema (fluid retention) causing puffiness, particularly in the face
Difficulty sleeping
A reduction in physical strength
One participant described trying to find a driveway whenever he was on one of his walks so he could walk onto the path from the road, rather than stepping onto the gutter because even that felt too effortful.
Psychological changes
Impaired decision-making and difficulty concentrating
An increase in obsessive thoughts, particularly about food
Increased depression, anxiety, irritability, and emotional dysregulation
Social withdrawal and isolation
Decreased sex drive
Decline in personal hygiene
Reduced sense of humour
Several of the men also began dreaming about food, with one reporting that he had dreamt of eating a "forbidden" food and woke up feeling guilty.
Some of the men developed more severe psychological symptoms. One participant became so unwell after a few weeks that he threatened to harm himself, was removed from the study and admitted to a psychiatric ward. Interestingly, after only a few days of eating normally, his symptoms resolved completely and he was discharged.
Eating behaviour changes
This is the section I find most significant in the context of eating disorder presentations and helping us understand what behaviours are likely driven by undereating vs the eating disorder.
Some of the behaviours which developed over the six months:
Hoarding and stealing food
Binge eating behaviours - during a walk, one participant stopped at multiple ice cream parlours and milkshake bars, completely breaking the requirements of the restricted diet
Obsessing over recipe books - five men started collecting them, one collected over 100 recipe books during the study year
Distress about food waste, including searching through rubbish bins
Guarding food defensively at mealtimes, worried that others would take it
Watering down or "souping" food to make it last longer
Adding excessive spices and condiments to food
Eating extremely fast, or extremely slowly
Licking plates clean
Increasing coffee consumption — some men had up to 15 cups a day to manage hunger
Starting smoking (four men) to suppress appetite
Chewing gum excessively - some consuming 40 to 60 packets per day, which led to Keys placing a limit on gum consumption
One man bought a dozen doughnuts and gave them to children on the street so he could watch them eat, rather than eat them himself
Do any of those behaviours sound familiar? We see them in clinic every single day. And yet they emerged in men who had no eating disorder, no prior history of disordered eating, and were in excellent psychological health before the study began.
What we know is that these behaviours are a natural, adaptive response to being under-fed rather than a personality or character flaw, or a symptom unique to eating disorders. This study is one of the most compelling pieces of evidence we have for why under-eating is often the driving force behind eating behaviours we associate with eating disorders.
Four men were removed from the study during this phase — three for breaking the diet and one for failing to achieve the required weight loss. Thirty-two men continued into phase three.
Phase Three: The Controlled Rehabilitation Period (12 weeks)
The 32 remaining men were divided into four groups and each given different caloric amounts. Ancel Keys wanted to understand how much energy the body needed to rehabilitate. Some men were also given supplementary vitamins or additional protein.
What Dr Keys and the participants discovered is that in the early weeks of this phase, it didn't matter which group a man was in - none of them were regaining weight or seeing meaningful reversal of symptoms. Keys continued to increase calorie targets throughout the 12 weeks, with some men eventually consuming around 4,200 calories per day. Despite this increase, none of the men returned to their original pre-study weight by the end of this phase.
This tells us something important about recovery: healing and rehabilitation takes time and more energy. Twelve weeks of controlled rehabilitation, even at higher calorie intakes, was not enough to undo six months of significant restriction.
Phase Four: The Unrestricted Period (8 weeks)
This is the phase most people (including myself) don't talk about.
After the controlled rehabilitation period, Ancel Keys asked 12 of the men to remain for a further eight weeks. During this time, there were initially no restrictions on how much they could eat.
And what did they eat?
On average, these men consumed approximately 4,500 to 5,000 calories per day. Some consumed up to 7,000 to 11,000 calories in a single day.
This phenomenon is called compensatory hyperphagia — an intense, adaptive increase in food intake that occurs in response to a period of caloric deficit, designed to restore energy balance. It is the body doing exactly what it is supposed to do.
What is also important to share with you, is that in 2002-2003, 19 participants were interviewed and shared that during the rehabilitation period:
Two men engaged in purging behaviours
One man had to be hospitalised to have his stomach pumped because he ate too much
11 men experienced episodes of overeating (not binge eating)
6 engaged in behaviours that would meet the criteria for binge eating disorder
Again, these were men with no previous history of eating disorders. The restriction they experienced led directly to the emergence of binge eating and purging behaviours. This is not evidence of a personal failing or psychological weakness. It is evidence that dietary restriction can create the very behaviours we associate with eating disorders like bulimia nervosa and binge eating disorder.
What Happened in the Long Term?
For many months, the men reported a persistent, intense sensation of hunger that they simply could not satisfy, no matter how much they ate.
After the study concluded, 21 of the men were followed up at eight months and eight were followed up at one year. Then, in 2002 and 2003, two significant research papers were published interviewing surviving participants (by then in their 70s and 80s) to assess any lasting physical or psychological effects.
The short story: no lasting physical or psychological effects were reported.
The longer story: It took between six months and five years for eating behaviours and weight to return to normal.
Many of the men experienced weight overshoot, meaning that their weight restored above their pre-study weight before settling back down. The mean of overshoot above control weight was 3.3kg kilograms, though at the upper end of the range, one man restored to around 116% of their starting weight before settling. Three men never returned to their exact pre-study weight, remaining slightly above.
During the restoration period, the men's bodies also prioritised rebuilding fat mass before fat-free mass (muscle). This mirrors what we see in eating disorder recovery, where some people notice changes in body composition, particularly around the abdomen, before weight begins to redistribute more evenly. This is the body protecting its vital organs. It is biology, not a sign that something has gone wrong. (I will be doing a whole separate podcast episode on the science of weight restoration and body composition, because there is a lot to cover).
What This Means for Eating Disorder Recovery
The Minnesota Starvation Experiment is one of the most important pieces of evidence we have as eating disorder dietitians. Here is what it tells us:
Many of the physical and psychological symptoms of under-eating are not symptoms of an eating disorder, they are symptoms of not eating enough. They resolve with adequate nutrition.
Eating and psychological behaviours we associate with eating disorders are often driven by energy restriction. Bingeing, purging, food hoarding, eating rituals, obsession with food and recipes - these emerged in men who had none of these tendencies before the study began. Under-eating can create the very cycle of behaviours that sustains an eating disorder.
Hunger after restriction is intense, adaptive, and normal. Compensatory hyperphagia is the body doing its job. It is not greed, it is not a lack of willpower - it is biology.
Nutritional rehabilitation takes time. The timeline varies and weight may overshoot before it settles. Trust that process.
A Note on the Study's Limitations
As with any research, it is important to acknowledge the limitations. All 36 participants were Caucasian males, which means we cannot assume these findings translate equally to people of all genders, ethnicities, ages, and body sizes. The lived experience of under-eating and recovery will look different for different people. What this study gives us is a foundational understanding of human physiology under restriction.
You Don't Have to Navigate This Alone
If you relate to any of what has been described in this post, please know that rehabilitation takes time, and it programmed in your very cells what needs to happen to return to good physical and psychological health (from a rehabilitation perspective).
If you would benefit from specialist dietetic support through your recovery, we would love to hear from you. You can book a free 20 minute discovery call with one of our eating disorder dietitians at Talia Cecchele Nutrition to talk about how we can help.
And if you haven't listened to the Food is Food episode on the Minnesota Starvation Experiment yet, head over to our podcast page.
Talia Cecchele
TCN Director and Lead Specialist Dietitian
Talia Cecchele Nutrition (TCN) is a virtual clinic with a team of registered dietitians specialising in eating disorders and disordered eating. Our services include 1:1 consultations, group meal support and group programs to support you to break free from food rules and chronic dieting and find food freedom. Talia and her team work by incorporating a compassion-led, non-diet and weight inclusive. To enquire about a private consultation please fill out a contact form.
REFERENCES:
Keys, A., Brozek, J., Henschel, A., Mickelson, O., & Taylor, H.L. (1950). The biology of human starvation (Vols. 1–2). University of Minnesota Press.
Kalm, L.M. & Semba, R.D. (2005). They starved so that others be better fed: Remembering Ancel Keys and the Minnesota Experiment. Journal of Nutrition, 135(6), 1347–1352.
Tucker, T. (2006). The Great Starvation Experiment. Free Press.
Galmiche, M., Déchelotte, P., Lambert, G. and Tavolacci, M.P. (2019). Prevalence of eating disorders over the 2000–2018 period: a systematic literature review. The American Journal of Clinical Nutrition, 109(5), pp.1402–1413.
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