You Need to Know About The Minnesota Starvation Experiment Part One
If you have a restrictive eating disorder, you might already be familiar with The Minnesota Starvation Experiment and if you aren't then you need to be. It is the single, most important scientific experiment that has been undertaken into the effects on a person of semi-starvation and what happens when recovering from a semi-starved state. This kind of experiment will not be repeated for ethical reasons but the results of this experiment, carried out during the Second World War, continues to educate and inform scientists and health professionals today, nearly eighty years after it was conducted.
This first post of two about the Minnesota Starvation Experiment covers what the experiment involved and some of the key findings from it. In the next post, I will cover why the results from the Minnesota Starvation Experiment matter to people with restrictive eating disorders today and what the experiment teaches us about how a body and brain are effected both by being fed inadequately and when 'refed' back to health from a semi-starved state.
A reader recently asked me to write and talk about how to cope with weight gain in overcoming an eating disorder and a critical first step in beginning to accept weight gain in recovery is to understand why it is so necessary. Knowing about the learnings from the Minnesota Starvation Experiment will help. In future posts, I will also discuss set point and overshoot theories and why these scientific understandings about the optimal health requirements of a body are important, perhaps making it then that little bit easier to 'rationalise' why you do need to accept and allow the weight gain in order to fully heal and emerge from the addicted state of energy deficit that an eating disorder will create.
**Please note that the following information is also taken from my book, Addicted to Energy Deficit, which also includes so much more!**
Restrictive Eating Disorders Create a State of Semi-Starvation
A restrictive eating disorder puts your body into a state of energy deficit, which in simpler terms is a state of semi-starvation. This is true whether you look starved in a skin-and-bone emaciated sense or not. If your body weight is below the level that your brain recognises to be optimal for your health, then you are in a state of starvation.
A semi-starved state occurs with a restrictive eating disorder when you are consistently eating restrictively compared to your body needs and/or compensating for the energy you do take in. And while your body stores of fat and lean tissues also remain below the level that is optimal for your set point, you will remain in a state of semi-starvation. It is for this reason that you need to know about the Minnesota Starvation Experiment.
The Minnesota Starvation Experiment
The experiment was conducted during the Second World War between 1944–1945 by Dr Ancel Keys and Dr Josef Brozeck. The intention was to study the effects of dietary restriction and develop an understanding of how best to support people overcoming a starved state. This information was needed to improve understanding of how best to rehabilitate people during the post-war period who had been food deprived or prisoners of war.
Thirty-six healthy young men were selected from two hundred volunteers for the experiment. They were conscientious objectors to the war and they ranged in age between twenty and thirty-three.
The initial experiment was made up of three phases:
Three Month Control Period - During this initial phase, the men were fed individualised amounts to maintain their 'ideal body weight' (also called their control weight). The average amount that each man was fed in this period was 3,492 calories.
Six Month Semi-Starvation Phase - The aim of this phase was for each man to lose 25% of his 'ideal body weight'. The average intake for this phase was 1,570 calories but the amount each individual man was fed was dependent on his individual rate of weight loss. The men were fed two meals a day and meals were made up of mainly cabbage, potatoes and dark bread to mimic typical foods consumed in European wartime diets.
Three Month Rehabilitation Phase - Thirty two of the original thirty six men reached this final stage. These men were then divided into four groups, each group fed a controlled amount of either an additional 400, 800, 1,200 or 1,600 calories to the amount they had been fed in the semi-starvation phase. After five weeks of refeeding at this level, the rate of improvement was much slower than expected, and so the intake of the men was reviewed again (this is covered in more detail below).
THE UNRESTRICTED REHABILITATION PHASE
At the end of the experiment, twelve men volunteered to continue on for another two months, during which time they would be able to eat without restrictions but be observed, and have their intake level monitored.
Findings from the Minnesota Starvation Experiment
Findings from the Control Period
During this initial phase, when each man was eating enough to maintain his ideal body weight, the men were said to feel good; they were energised and engaged. They volunteered in local community projects, some studied at the university, and they took part in a variety of cultural activities in the city. They were essentially healthy young men who were interested in life, engaged, social and active.
Findings from the Semi-Starvation Phase
During the first few weeks in which the men had their calories cut by around half to the amount they had needed to maintain their control weight, they generally remained in good spirits and interested in their weight loss. But as time went on, the men developed some significant physical, psychological, social and cognitive symptoms.
Physically, the men became increasingly weak. In 2002, nineteen of the original men who took part in the study were interviewed about their experiences by researchers. One of the men could remember not being able to open a department store door because he had become so weak. They developed a decreased tolerance of the cold, dizziness, vertigo, tiredness, hair loss, reduced coordination and ringing to their ears. The men had a dramatic drop in their heart rate and blood pressure. Some of the men developed significant oedema. Their need to urinate increased and their digestive system slowed down, giving them constipation and other stomach issues. Cuts and bruises healed more slowly, and sleep became interrupted. Their sex drive and interest in relationships also disappeared.
Mentally, the men became increasingly irritable and impatient. Little things their friends did that would usually not bother them now made them very upset. They became annoyed by the eating habits of other people. Over the three months, the men became increasingly withdrawn and introverted. The researchers observed indifference and boredom among them. Some pulled out of their university classes because they no longer had the motivation or mental energy to attend. Depression was also observed. They started to neglect their personal hygiene, had difficulty making decisions, lost their sense of humour and developed more rigid thinking. They increasingly found conversation with others difficult and pointless, and if they did go to the cinema, they found they could recognise comedy but no longer felt compelled to laugh.
Food obsession developed. Eating in ritualised ways became standard. Some of the men would eat very slowly to make the food last longer, while others would eat incredibly quickly. Licking of plates at the end of a meal became the norm. The men became upset at the sight of food waste, and many reported dreaming about food. Some of the men would go to diners just to watch other people eating, while others would actively avoid having to see others eat when they couldn’t. Some of the men collected cookbooks, with one participant later reporting that during the study period, he collected over a hundred. Food became their main focus, with one man later reporting that food became the most important, if not the only, thing in his life, reflecting that this also makes life pretty dull.
During the start of the semi-starvation phase, the men were allowed to freely drink water, tea and coffee. This resulted in many of them being observed to drink coffee and tea obsessively to fill their stomach. Keys therefore decided that this consumption needed to be limited, and so the men were restricted to nine cups a day. They were also allowed to chew gum during this stage of the experiment, but this also dramatically increased, to the point one man (later removed from the experiment) was observed to chew up to forty packs a day.
The men reported trying to keep themselves distracted from their hunger as best they could. Some of them started to collect and hoard both food and non-food-related items that they didn’t need, such as books or trinkets. In the 2002 interviews, one of the men still couldn’t make sense of the hoarding behaviour he experienced at the time (this was very likely a part of the scarcity mindset what you can read more about here).
The behaviour and psychological state of some of the men became more concerning. One man was chopping wood one day with an axe and cut off three of his fingers. Years later when interviewed, he said, I admit to being crazy mixed up at the time. I am not ready to say that I did it on purpose. I am not ready to say that I didn’t.
Four men didn’t complete the experiment. Of these, two were hospitalised during the semi-starvation phase for pre-psychotic symptoms. One man impulsively broke his diet repeatedly and began to go on minor shoplifting sprees, stealing sweets and trinkets that were all but worthless to him. He was seen to write 'voluminously and creatively'. He was admitted to a psychiatric ward after he developed a violent emotional outburst and threatened suicide. After being allowed to eat freely again, his mental state and behaviours quickly returned to normal.
Another man stole food items and rooted in rubbish bins. He was dropped from the experiment due to failure to lose weight. At this point, he ate huge amounts in a binge-like way, causing him to vomit, and he sought admission for psychiatric help. His symptoms also subsided after a few weeks, and he later denied experiencing any further psychiatric problems during his lifetime.
Of the final two participants not to remain to the end, one had an episode of passing blood in his urine and was taken out of the experiment. His urine reportedly cleared soon after he was eating normally again. The final participant didn’t lose weight at the rate Keys hoped, and so Keys suspected him of cheating. The man denied it, but Keys omitted his data from the results that were published.
Findings from the Rehabilitation Phase
Many men reported that the start of the rehabilitation phase was the most challenging part of the experiment. This was because they experienced no noticeable relief from the hunger despite now being given more food. Some of the men were also surprised when they initially lost weight in this refeeding stage, which was attributed to some loss of oedema as they began to eat more. Ongoing feelings of weakness also frustrated the men as it took longer to improve than they had hoped.
The men were split into four groups during this 12 week rehabilitation phase, each group receiving a different increased number of calories to the level they were receiving during the semi-starvation phase. The men weren't told which group they were in, and none of them thought themselves to be in the group receiving the highest amounts. The group receiving the smallest additional intake at this time only received an additional 400 calories a day to the amount they had been eating. After five weeks, the rate of improvements in the men was much slower than expected, although this was proportional to which group they were in. At this point, Keys and the research team increased the feeding amounts again by another 800 calories a day, so they were either given an additional 1,200, 1,600, 2,000 or 2,400 a day to the amounts they received during the starvation phase. This finally resulted in more noticeable rises in their weight, and more importantly their mood also improved. Levels of depression were noted to reduce in line with how much food was now given.
At the end of this 12 week period of controlled refeeding, none of the men were back at their starting weight. On average, weights were back to 36.7 percent of what had been lost. Physically, the men still felt a long way from their pre-starvation levels of energy and strength.
Findings from the Unrestricted Rehabilitation Phase
The twelve men who stayed on to be observed and monitored over another eight weeks while now being allowed to eat completely unrestrictedly described feeling a complete loss of control over their eating when they could eat freely, and many ate abundantly.
One of the men in the later interviews described a day when he had eaten several large meals in town in a very short space of time and was sick on the bus on the way back to the accommodation because his stomach couldn’t cope with it. He said that he simply couldn’t satisfy his craving for food despite a full stomach. Another man during this time had to be taken to hospital to have his stomach pumped as he had eaten so much. In the first couple of weeks of the unrestricted rehabilitation phase, most of the men ate high amounts with some eating up to 11,500 calories a day.
When Keys and the researchers became alarmed to witness these seeming 'overeating behaviours', they became concerned and reintroduced some control over food access in the week but not at weekends. In doing so they noted a pattern of 'weekend gorging' where the men were observed to eat 50-200 percent more food at the weekends than during the days of controlled refeeding in the week.
Longer-Term Findings of the Minnesota Starvation Experiment
The impact of taking part in the Minnesota Starvation Experiment was much longer lasting on each individual man than the length that the study ran for. Nineteen of the men were interviewed when they were in their eighties about their experiences and of these, ten reported that their food perceptions and perspectives were forever altered.
One man described the year following the experiment as a 'year-long cavity' that needed to be filled and a year of eating 'excessively'. In fact, eight months after the rehabilitation phase, around a third of the men were still reported to be eating large quantities of food. Some of the men also said that it was at least two years before they felt their body had fully recovered, returning to their previous strength and stamina.
Body weight in the men peaked around eight months into rehabilitation and seven of the men reported being very concerned about the initial fat accumulation on their abdomen and buttocks, and that this had made them feel 'fat'. They recalled that as they gained weight, it was initially distributed in different places to where they had carried weight before the experiment, stating that they felt their thighs, buttocks and midsection all appeared fuller and their face fatter.
Most of the men reported that it took around two years for their body weight to stabilise back to their pre-experiment weight range and distribution.
The depression seen in all the men improved rapidly when they were eating freely again. One man who reported a deep, dark depression during the experiment said that it improved during the rehabilitation phase, and he had no further 'psychiatric problems' in his lifetime.
The adult children of one of the men were interviewed recently, and they reported that their late father’s relationship with food and his body was forever altered by the experiences he went through in the experiment. They could recall him telling them that food deprivation was the hardest thing that could ever be inflicted on a person, creating a loss of any kind of life sustenance. They also spoke about the fact that their father always had to have food close at hand, so he knew it was there when he needed it.
After the study, many of the men chose to enter into either charitable work that involved getting food to the starving or hungry, and a couple of them even had careers working with people who were deprived or hungry. There was a sense of need to support others who were starved because of their understanding and empathy for how hard hunger is.
These men went through a life-changing ordeal during the Minnesota Starvation Experiment but when asked later if they would repeat it if they were asked to, all but one of them said that they would.
Concluding This Post...
If you have a restrictive eating disorder and you are in a state of semi-starvation, then I'm sure that you can relate to a lot of the findings from the Minnesota Starvation Experiment and these findings matter. They teach us so much about what starvation does to a person, eating disorder or not. And understanding this can help you to recognise that maybe some of your traits or the symptoms that you have put down to 'just being you' are in fact symptoms of a starved body and brain. Learnings from the Minnesota Starvation Experiment should help you to recognise why you do need to eat more to find your way out of energy deficit and discover just how much will improve if you do.
This is a long first post about the Minnesota Starvation Experiment in which just some of the facts and findings or it are given. In the second post on this topic, I will relate some of the key findings of the experiment to restrictive eating disorders and the experiences of those with an eating disorder or in the process of overcoming one.
Leah M. Kalm, Richard D. Semba. They starved so that others be better fed: Remembering Ancel Keys and the Minnesota Experiment. The Journal of Nutrition, Volume 135, Issue 6, June 2005, Pages 1347–1352, https://doi.org/10.1093/jn/135.6.1347.
Eckert, Elke & Gottesman, Irving & Swigart, Susan & Casper, Regina. (2018). A 57-YEAR FOLLOW-UP INVESTIGATION AND REVIEW OF THE MINNESOTA STUDY ON HUMAN STARVATION AND ITS RELEVANCE TO EATING DISORDERS. 2.
Malcolm Gladwell, Revisionist History Podcast.
**For more information on eating disorders and how to overcome one, please don't miss my newly available books,
The information for this post was largely taken from Addicted to Energy Deficit.
If you like to listen, as well as (or instead of read!) then this blog post is the transcript of a podcast episode which you will find on my podcast series,
available on this website, all mainstream podcast platforms and on YouTube.