The Minnesota Starvation Experiment

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This article was written by Student Dietitian Sarah Hall, and reviewed by Dietitian Maeve Hanan.


Background to the Study

Over centuries people have provided anecdotal reports on the effects of starvation; however, there was little actual research on the subject until the 1940s.

Recognising the growing incidence of starvation in Europe during World War II physiologist, Ancel Keys, and psychologist, Josef Brozek, conducted a study to determine how diet can be used to rehabilitate individuals who had experienced starvation. 

Rather than just focusing on the nutritional requirements, they wanted to offer insight on whether semi-starvation had behavioural consequences and whether this affects personality.

As refeeding was the aim of the research, the subjects would first have to be semi-starved. The study known as the Minnesota Starvation Experiment provides significant insight into the effect of semi-starvation on the psychological and physiological state, which also shows parallels with dieting, disordered eating and eating disorders (1). 

Although this study provided very useful insights into starvation and refeeding, it would certainly not be allowed to go ahead today due to how risky it was for the participants.

What Did This Study Involve?

In 1944, Keys recruited 36 young, healthy male conscientious objectors to World War II to participate in a 13-month study.

A conscientious objector is an “individual who has claimed the right to refuse to perform military service”, whether for conscience or religious reasons. They were assigned to the Civilian Public Service, and Keys was able to recruit from this cohort. 

Over 400 men responded to a brochure which asked, “Will you starve so they can be fed?”. This number was whittled down to 100 volunteers who were interviewed and examined before the 36 men deemed the most mentally and physically fit were selected. Other criteria for selection included getting along with others and having a sense of responsibility concerning improving the nutritional status of those experiencing starvation. (2)

The participants slept in the football stadium at the University of Minnesota, which served as a dormitory. Throughout the study period, they worked in the laboratory, walked 22 miles a week, and participated in university classes. Body measurements were taken routinely, as were psychomotor, endurance, psychological tests and hand-eye coordination tests. Each participant was also required to also write in a journal.

Phases of the Study

The study was split into three phases: a 12-week control period, a 24-week semi-starvation period and a 12-week refeeding period. Twelve of the participants received an additional eight weeks of rehabilitation, and follow-up continued for a further 12 months.

Phase 1: 

During the 12-week control period, normal eating behaviours were observed. Under the supervision of a dietitian, the participants ate meals that were adjusted to their calorie needs to maintain their body size; this worked out as around 3500 calories of food per day.

Phase 2: 

During the 24-week semi-starvation period, the men were restricted to approximately 1600-1800 calories, a similar amount to many of today’s diets and meal plans.

It was designed to mimic a European diet during war which was low in protein, high in carbohydrate and based around potatoes, root vegetables and bread. They ate breakfast and lunch but no dinner (oh hello, intermittent fasting!).

As a result, they gradually lost approximately 25% of their weight at a rate of 2-2.5 pounds (~1kg) per week.  

Phase 3: 

For the 12-week refeeding period, the men were divided into four groups and allowed an extra 400, 800, 1200 or 1600 calories. However, none of the men knew what group they were in, and even those receiving an extra 1600 thought they were in the lowest calorie group.

Each group was subdivided further to account for different protein and nutrient intakes.

A small group of participants stayed for an additional eight weeks and were able to eat unrestricted.   

Results of The Minnesota Starvation Experiment

The men immediately reported a decline in physical energy and personal motivation as soon as their calorie intake was reduced. Not surprisingly, notable changes were observed in the participants.

Physical Changes:

  • Weakness
  • Emaciation
  • Lower body temperature
  • Reduced sex drive
  • Decreased heart rate

The participants’ physical changes were significant. Apart from the obvious physical signs of weight loss (19% – 28%) among the final 32 participants, physical changes included protruding bones, a 70% reduction in fat mass and a 40% reduction in muscle loss.

In addition, their basal metabolic rate (BMR), which is the amount of energy the body requires at rest, decreased by 40% due to the low caloric intake, which reduced the body’s need for energy. Participants also suffered headaches, dizziness, hair loss, oedema, gastrointestinal discomfort and intolerance to the cold. 

During refeeding, extreme hunger has been associated with fat and muscle depletion, with fat repletion taking precedence (3).

Following refeeding, they had 140% of their original body fat by the time they hit their original weight. Following a period of dieting, the body doesn’t understand you just wanted to look hot in the bikini and will therefore lay down more fat in case you head into another period of restriction.

Keys et al. also found that following a period of starvation, a person needs at least 4000 calories a day to recover. 

Changes in Eating Behaviour:

Participants started guarding their food defensively, afraid others would steal it and would become agitated and aggressive if other participants had more food than them. The participants would also become aggressive if anyone left any food on their plate as it was wasteful. 

At mealtimes, the men were recorded licking their plates and used tactics to make food go further or make it appear there was more food on their plate than there was. They would push food around their plate, cutting it into small pieces, and hold food in their mouths for long periods.

Some would drink excessive amounts of water to feel full, others chewed gum, and some started smoking. 

Those who stayed the extra eight weeks at the end of the study were observed experiencing difficulties reading their hunger cues and started eating several meals in one sitting.

During the first two weeks, each participant was allowed to choose their meals and consequently ate between 7,000-10,000 calories per day and on occasion as many as 11500 in a single day, reporting insatiable hunger which they couldn’t satisfy. Some of the men developed binge-eating and purging behaviours. One man was admitted to hospital after a binge episode. After five months of refeeding, they continued to use these behaviours, although their mood stabilised.

Psychological Changes:

  • Food obsession
  • Irritability and mood swings
  • Anxiety and depression
  • Body image concerns
  • Apathy

Participants notably became far more preoccupied with food which became focal points in conversations. Some volunteers struggled to concentrate due to their preoccupation with food. Their interest in food expanded into reading cookbooks and collecting recipes. One of the men collected over 100 cookery books while participating in the study. Three participants became chefs, and one went into agriculture, reflecting their newfound interest in food.

“Food became the one central and only thing in one’s life. And life is pretty dull, if that’s the only thing”

Harold Blickenstaff

At the beginning of the study, the men were physically and psychologically healthy. However, following semi-starvation, they developed symptoms similar to those of eating disorders.

Previously extraverted participants became isolated and felt socially inadequate. One participant observed that although he recognised comedy, he never felt compelled to laugh anymore.

Significant increases in anxiety were recorded, and participants became more sensitive and argumentative with others. Keys et al. noted that these men only showed positive emotional responses in response to discussions around weight or food talk. 

Body image also shifted, and even though these men had lost a considerable amount of weight, they didn’t see themselves as too thin. They did, however, compare themselves to other people, who they saw as too fat.

One participant was excluded from the study after seeking out unauthorised food. Although he had feelings of euphoria at the time, feelings degenerated into extreme pessimism and remorse. He felt he had failed and had nothing to live for.

Another was also excluded for breaking the diet, and two were excluded after being hospitalised due to psychotic symptoms.

One participant began having dreams that featured cannibalism only a few weeks into the restriction phase of the experiment, and both recovered after a few days of eating a regular diet.

During the refeeding phase, many men reported feeling even more depressed than during the semi-starvation phase. The men in the group who received the least amount of calories were the worst affected. Plate licking continued, irritability, aggression and mood swings became more severe. One of the men amputated three fingers while using an axe and admitted feeling “crazy mixed up at the time”, explaining, “I’m not ready to say I did it on purpose, I’m not ready to say I didn’t”.   

Conclusion

The act of starvation impacts an individual’s overall physical and psychological well-being. Interestingly the amount of calories used for the starvation diet was similar to many current weight-loss diets (1700 kcals per day). 

Physical changes included suppressed metabolism, during starvation and refeeding, emaciation, extreme hunger and at least 4000 calories per day was needed for restoration and recovery.

Psychological changes included anxiety, depression, mood swings, food obsession and body image issues. As a whole, eating disorder symptoms and behaviours emerged in those with no prior history of this.

In 1950 Keys et al. published “The Biology of Human Starvation”, which describes the impact of long-term food deprivation on human physiology and behaviour to help famine relief. However, the legacy left by the Minnesota Starvation Experiment is the impact it has had in the research into the effects of food deprivation in those with eating disorders (4).

References:

  1. Tucker (2007) “The great starvation experiment: Ancel Keys and the men who starved for science” University of Minnesota Press.
  2. Kalm et al. (2005) “They starved so that others be better fed: remembering Ancel Keys and the Minnesota experiment”. The Journal of nutrition, 135(6), pp.1347-1352.
  3. Dulloo (2021) “Physiology of weight regain: Lessons from the classic Minnesota Starvation Experiment on human body composition regulation”. Obesity Reviews, 22, p.e13189.
  4. Keys et al. (1950) “The Biology of Human Starvation (2 volumes)”. University of Minnesota Press.

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