The Minnesota Semi-Starvation Experiment (1944-1945)

“They went from 3000 calories (as healthy individuals and determined by there individual stats) they then went into the semi starvation calories stage, bring their calories down to 1570. They mapped the changes, which many were psychological among other things. In short they deteriorated significantly when being reduced to 1570 calories. They were moody, depressed, no energy…. When they went into the rehabilitation phase they increased food (depending on the persons stats) from 1970, 2380, 2770 and 3170… and they still didn’t put on weight (or much weight), then they continued to increase their food by 800 calories….. they tested multivitamins which they found weren’t needed.”

The Minnesota Semi Starvation Experiment, Photograph 1
Image: The Minnesota Semi Starvation Experiment (1944-1945)

The Minnesota Starvation Experiment, also known as the Minnesota Semi-Starvation Experiment, the Minnesota Starvation-Recovery Experiment and the Starvation Study, was a clinical study performed at the University of Minnesota between November 19, 1944 and December 20, 1945. The investigation was designed to determine the physiological and psychological effects of severe and prolonged dietary restriction and the effectiveness of dietary rehabilitation strategies.

The motivation of the study was twofold: first, to produce a definitive treatise on the subject of human starvation based on a laboratory simulation of severe famine and, second, to use the scientific results produced to guide the Allied relief assistance to famine victims in Europe and Asia at the end of World War II. It was recognized early in 1944 that millions of people were in grave danger of mass famine as a result of the conflict, and information was needed regarding the effects of semi-starvation—and the impact of various rehabilitation strategies—if postwar relief efforts were to be effective.

The study was developed in coordination with the Civilian Public Service (CPS) and the Selective Service System and used 36 men selected from a pool of over 200 CPS volunteers.[1]:46

The study was divided into three phases: A twelve-week control phase, where physiological and psychological observations were collected to establish a baseline for each subject; a 24-week starvation phase, during which the caloric intake of each subject was drastically reduced—causing each participant to lose an average of 25% of their pre-starvation body weight; and finally a recovery phase, in which various rehabilitative diets were tried to re-nourish the volunteers. Two subjects were dismissed for failing to maintain the dietary restrictions imposed during the starvation phase of the experiment, and the data for two others were not used in the analysis of the results.

In 1950, Ancel Keys and his colleagues published the results of the Minnesota Starvation Experiment in a two-volume, 1,385 page text entitled The Biology of Human Starvation (University of Minnesota Press).[2] While this definitive treatise came too late to substantially impact postwar recovery efforts, preliminary pamphlets containing key results from the Minnesota Starvation Experiment were produced and used extensively by aid workers in Europe and Asia in the months following the cessation of hostilities.[1]:183–184

The Minnesota Semi Starvation Experiment, Photograph 2
Image: The Minnesota Semi Starvation Experiment (1944-1945)

Principal investigators

Ancel Keys was the lead investigator of the Minnesota Starvation Experiment. He was responsible for the general supervision of the activities in the Laboratory of Physiological Hygiene and was directly responsible for the X-ray analysis and administrative work for the project. Keys founded the Laboratory of Physiological Hygiene at the University of Minnesota in 1940 after leaving positions at Harvard’s Fatigue Laboratory and the Mayo Clinic. Starting in 1941, he served as a special assistant to the U.S. Secretary of War and worked with the Army to develop rations for troops in combat (K-rations).[1]:30–31 Keys served as Director for the Laboratory of Physiological Hygiene for 26 years, and retired in 1972 after a distinguished 36-year career at the University of Minnesota.

Olaf Mickelsen was responsible for the chemical analyses conducted in the Laboratory of Physiological Hygiene during the Starvation Study, and the daily dietary regime of the CPS subjects—including the supervision of the kitchen and its staff. During the study, he was an associate professor of biochemistry and physiological hygiene at the University of Minnesota and received his Ph.D. in biochemistry from the University of Wisconsin in 1939.

Henry Longstreet Taylor had the major responsibility of recruiting the 36 CPS volunteers used in the Minnesota Starvation Experiment, maintaining the morale of the participants and their involvement in the study. During the study he collaborated with Austin Henschel in conducting the physical performance, respiration and postural tests. He received his Ph.D. from the University of Minnesota in 1941 and joined the faculty at the Laboratory of Physiological Hygiene, where he held a joint appointment with the Department of Physiology. His research concentrated on problems in cardiovascular physiology, temperature regulation, metabolism and nutrition, aging and cardiovascular epidemiology.

Austin Henschel shared the responsibility of screening the CPS volunteers with Taylor for selection in the Minnesota Starvation Experiment and, in addition, had charge of the blood morphology and scheduling all the tests and measurements of the subjects during the course of the study. He was a member of the faculty in the Laboratory of Physiological Hygiene and the Department of Medicine at the University of Minnesota.

Josef Brožek (1914–2004)[3] was responsible for psychological studies during the Starvation Study, including the psychomotor tests, anthropometric measurements and statistical analysis of the results. Brožek received his PhD from Charles University in Prague, Czechoslovakia in 1937. He emigrated to the United States in 1939 and joined the Laboratory of Physiological Hygiene at the University of Minnesota in 1941, where he served in a succession of posts over a 17-year period. His research in the Laboratory of Physiological Hygiene concerned malnutrition and behavior, visual illumination and performance, and aging.

The Minnesota Semi Starvation Experiment, Photograph 3
Image: The Minnesota Semi Starvation Experiment (1944-1945)

Participant volunteers

An essential ingredient for the successful execution of the Minnesota Starvation Experiment was the availability of a sufficient number of healthy volunteers willing to subject themselves to the year-long invasion of privacy, nutritional deprivation and physical and mental hardship necessary to complete the study. From the outset, the experiment was planned in cooperation with the Civilian Public Service and the Selective Service System, with the intention of using volunteers selected from the ranks of conscientious objectors already inducted into public wartime service. Keys obtained approval from the War Department to select participants from the CPS.

In early 1944, a recruitment brochure was drafted and distributed within the network of CPS work camps throughout the United States. Over 400 men volunteered to participate in the study as an alternative to military service; of these, about 100 were selected for detailed examination. Drs. Taylor, Brožek, and Henschel from the Minnesota Laboratory of Physiological Hygiene traveled to the various CPS units to interview the potential candidates and administer physical and psychological tests to the volunteers. 36 men were ultimately selected who demonstrated evidence of the required mental and physical health, the ability to get along reasonably well within a group while enduring deprivation and hardship, and sufficient commitment to the relief and rehabilitation objectives of the investigation to complete the study. The subjects were all white males, with ages ranging from 22 to 33 years old.

Of the 36 volunteer subjects, 15 were members of the Historic Peace Churches (Mennonites, Church of the Brethren and Quakers). Others there included Methodists, Presbyterians, Baptists, and one of each who was Jewish, Episcopalian, Evangelical & Reformed, Disciples of Christ, Congregational, and Evangelical Mission Covenant, along with two participants without a declared religion.[4]

The 36 CPS participants in the Minnesota Starvation Experiment were: William Anderson, Harold Blickenstaff, Wendell Burrous, Edward Cowles, George Ebeling, Carlyle Frederick, Jasper Garner, Lester Glick, James Graham, Earl Heckman, Roscoe Hinkle, Max Kampelman, Sam Legg, Phillip Liljengren, Howard Lutz, Robert McCullagh, William McReynolds, Dan Miller, L. Wesley Miller, Richard Mundy, Daniel Peacock, James Plaugher, Woodrow Rainwater, Donald Sanders, Cedric (Henry) Scholberg, Charles Smith, William Stanton, Raymond Summers, Marshall Sutton, Kenneth Tuttle, Robert Villwock, William Wallace, Franklin Watkins, W. Earl Weygandt, Robert Wiloughby and Gerald Wilsnack.

The Minnesota Semi Starvation Experiment, Photograph 4
Image: The Minnesota Semi Starvation Experiment (1944-1945)

Goals and methods

The primary objective of the Minnesota Starvation Experiment was to study in detail the physical and psychological effects of prolonged, famine-like semi-starvation on healthy men, as well as their subsequent rehabilitation from this condition. To achieve these goals, the 12-month study was divided into four distinct phases:

  1. Control Period (12 weeks): This was a standardization period when the subjects received a controlled diet of approximately 3,200 kilocalories of food each day. The diet of the subjects who were close to their “ideal” weight was adjusted so as to maintain caloric balance, while the diets of the underweight and overweight individuals was adjusted so as to bring them close to their ideal weight. On average, the group ended up slightly below their “ideal” weight.[2]:74 In addition, the clinical staff of the Laboratory of Physiological Hygiene routinely conducted a series of anthropometric, physiological and psychological tests designed to characterize the physical and mental health of each participant under normal conditions.
  2. Semi-Starvation Period (24 weeks): During the 6-month semi-starvation period, each subject’s dietary intake was cut to approximately 1,560 kilocalories per day. Their meals were composed of foods that were expected to typify the diets of people in Europe during the latter stages of the war: potatoes, rutabagas, turnips, bread and macaroni.
  3. Restricted Rehabilitation Period (12 weeks): The participants were divided into four groups of eight men; each group received a strictly-controlled rehabilitation diet, consisting of one of four different caloric energy levels. In each energy-level group, the men were further subdivided into subgroups receiving differing regimens of protein and vitamin supplements. In this manner, the clinical staff examined various energy, protein and vitamin strategies for re-nourishing the subjects from the conditions of famine induced during the semi-starvation period.
  4. Unrestricted Rehabilitation Period (8 weeks): For the final rehabilitation period, caloric intake and food content was unrestricted but carefully recorded and monitored.

During the starvation period, the subjects received two meals per day designed to induce the same level of nutritional stress for each participant. Since each subject had distinct metabolic characteristics, the diet of each man was adjusted throughout the starvation period to produce roughly a 25% total weight loss over the 24-week period.

The researchers tracked each subject’s weight as a function of time elapsed since the beginning of the starvation period. For each subject, the weight versus time plot was expected—as well as enforced—to form a particular curve, the prediction weight-loss curve, whose characteristics were decided before the commencement of the experiment. The postulated curves turned out to be quite predictive for most subjects. If a subject did veer off his curve in any given week, his caloric intake for the next week would be adjusted, by varying the amount of bread and potatoes, to bring him back to the curve; however, the required adjustments were usually minor.[2]:75 The shapes of the curves were chosen “based on the concept that the rate of weight loss would progressively decrease and reach a relative plateau” at the final weight.[2]:74

For each subject, the weight vs. time curve was taken to be quadratic in time (in fact, an upward-opening parabola) with the minimum located at 24 weeks, at which point the weight is supposed to be equal to the final target body weight (the minimum is where the curve has zero slope; this corresponds to the “plateau” mentioned above). Mathematically, this means that the curve for each subject was given by:


where t is the time (measured in weeks) elapsed since the beginning of the starvation period, W(t) is the subject’s weight at time t, and Wf is the final weight that the subject was supposed to reach at the end of the 24-week period. The constant K is determined by the requirement that W(t=0) be the initial weight Wi, i.e. by solving:

Wi = Wf + K(24−0)

for K; this gives K = Wi − Wf / 24^.

The authors expressed this in terms of the percent total weight loss P, P = 100 × Wi − Wf / Wi

(which, as stated above, was supposed to be about 25% for all subjects), obtaining:

K = P / 100 x 24^ Wi.

Throughout the duration of the study each man was assigned specific work tasks, was expected to walk 22 miles (35 km) each week and required to keep a personal diary.[5] An extensive battery of tests was periodically administered, including the collection of metabolic and physical measurements; X-ray examinations; treadmill performance; and intelligence and psychological evaluation.

The Minnesota Semi Starvation Experiment, Photograph 5
Image: The Minnesota Semi Starvation Experiment (1944-1945)


The full report of results from the Minnesota Starvation Experiment was published in 1950 in a two-volume, 1,385-page text entitled The Biology of Human Starvation (University of Minnesota Press). The 50-chapter work contains an extensive analysis of the physiological and psychological data collected during the study, and a comprehensive literature review.

Among the conclusions from the study was the confirmation that prolonged semi-starvation produces significant increases in depression, hysteria and hypochondriasis as measured using the Minnesota Multiphasic Personality Inventory. Indeed, most of the subjects experienced periods of severe emotional distress and depression.[1]:161 There were extreme reactions to the psychological effects during the experiment including self-mutilation (one subject amputated three fingers of his hand with an axe, though the subject was unsure if he had done so intentionally or accidentally).[6] Participants exhibited a preoccupation with food, both during the starvation period and the rehabilitation phase. Sexual interest was drastically reduced, and the volunteers showed signs of social withdrawal and isolation.[1]:123–124 The participants reported a decline in concentration, comprehension and judgment capabilities, although the standardized tests administered showed no actual signs of diminished capacity. This ought not, however, to be taken as an indication that capacity to work, study and learn will not be affected by starvation or intensive dieting. There were marked declines in physiological processes indicative of decreases in each subject’s basal metabolic rate (the energy required by the body in a state of rest), reflected in reduced body temperature, respiration and heart rate. Some of the subjects exhibited edema in their extremities, presumably due to decreased levels of plasma proteins given that the body’s ability to construct key proteins like albumin is based on available energy sources.

The Minnesota Semi Starvation Experiment, Photograph 6
Image: The Minnesota Semi Starvation Experiment (1944-1945)

Related work

One of the crucial observations of the Minnesota Starvation Experiment discussed by a number of researchers in the nutritional sciences—including Ancel Keys—is that the physical effects of the induced semi-starvation during the study closely approximate the conditions experienced by people with a range of eating disorders such as anorexia nervosa and bulimia nervosa. As a result of the study it has been postulated that many of the profound social and psychological effects of these disorders may result from undernutrition, and recovery depends on physical re-nourishment as well as psychological treatment.[1]

Minnesota Starvation Experiment – An Interesting Dieting Case Study by Pratik Thakkar

The basic objective of this study was to see the physical, mental, and social effects of food restriction on otherwise healthy subjects and the long-lasting effects of disordered eating. Looking at the objective, you might already be assuming that these subjects were almost on the verge of starving to death. The average caloric intake during the ‘semi-starvation’ period was 1600 kcals. Much more than most people these days tend to diet on.

The main reason this study was conducted was that post World War II, the US media was flooded with war victims and refugees suffering from food shortages and starving. Ancel Keys, one of the most influential researchers in the field of nutrition thus decided to conduct this study to provide useful data an insight for relief workers.

Hundreds of volunteers came forward for the study but only 36 men who were deemed mentally and physically healthy were selected for this study.

The Minnesota Semi Starvation Experiment, Photograph 7
Image: The Minnesota Semi Starvation Experiment (1944-1945)

The main notes of the study are:

  1. The experiment began with a 12-week control period and on an average, the men were fed ~3400 kcals per day.
  2. They had basic daily work assignments, had to walk 22 miles a week, maintain a diary.
  3. Apart from the dietary restrictions, there were no other restrictions placed on them socially.
  4. After the control period, their caloric intake was slashed by 55% and brought down to ~1500 kcals per day for the next 24 weeks inducing a period of semi-starvation.
  5. The subjects lost 24.5% of weight on average towards the end of the study period.
  6. Their metabolic rate/expenditure dropped by 40% by the end, of which 25% was associated with the drop in body mass and the remaining 15% due to adaptive thermogenesis.

The above stats were only concerning the body weight, energy expenditure, and adaptive thermogenesis. What about the social and the mental aspects of the diet?

The Minnesota Semi Starvation Experiment, Photograph 8
Image: The Minnesota Semi Starvation Experiment (1944-1945)

Some of the social behavior observations by the researchers were:

  1. The men reported a decline in physical energy and personal motivation.
  2. Plate licking was a common practice at the dinner table to extend the meal timing and feel fuller.
  3. They diluted potatoes with water, held bites in their mouths for a long time without swallowing, or labored over combining the food on their plate making weird and seemingly distasteful concoctions.
  4. Many men stayed up till 5 a.m. collecting recipes from recipe books.
  5. They guzzled water, to keep themselves full.
  6. Some started purchasing or stealing food whereas one man started stealing cups from a coffee shop.
  7. Some took to smoking and chewing up to 30 packs of gums a day until it was banned by the lab.
  8. Budding romances collapsed and sexual desire evaporated.

The mental behavior change observations were:

  1. The men found themselves distracted by daydreams of food most of the time.
  2. They would bicker and fight in the line standing for food.
  3. They would coddle [the food] like a baby or handle it and look over it as they would some gold. They played with it like kids making mud pies.
  4. They preferred going to the movies alone and would recognize comedy but never felt compelled to laugh at it.
  5. They used to get easily pushed around in a store due to their frail frames and they never used to care about it.
  6. Their usual emotion was resignation.
  7. Sometimes, this dullness would give way to moments of euphoria followed by an emotional crash.
The Minnesota Semi Starvation Experiment, Photograph 9
Image: The Minnesota Semi Starvation Experiment (1944-1945)

This semi-starvation period ended with a 20-week rehabilitation phase and the data that emerged was even more surprising. Their physical recovery started progressing but the mental state deteriorated even further.

The plate licking went on, irritability became aggression, mood swings became more severe. One of the subjects brought down the ax on his own hand while chopping wood, amputating three fingers in the process. He later explained, “I am not ready to say I did it on purpose. I am not ready to say I didn’t.”

The subjects’ social moods somewhat stabilized after 3 months while some of them were binging to the point of sickness even 8 months later.

These observations were first published in Men and Hunger: A Psychological Manual For Relief Workers.

Post this study, these men constantly struggled to distinguish between appetite and hunger. Appetite demands for a meal whereas hunger is a need that begs for satisfaction by any means.[2]

  1. Minnesota Starvation Experiment (Wikipedia)
  2. Minnesota Starvation Experiment – An Interesting Dieting Case Study
  3. Men and hunger: a psychological manual for relief workers (1946) by Guetzkow, Harold Steere

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