The Minnesota Starvation Experiment

This is a blog about quite possibly the most important obesity experiment ever conducted. Please let me know if you come across a dietician who has ever heard of it, let alone studied it…

America joined WWII in 1941 – by which time Europe was already experiencing rationing and food shortages. A couple of years later, an American doctor, Ancel Keys, realised that it would be crucial to know what would happen if the war did not end soon and rationing turned to starvation. He set about one of the most ambitious health experiments ever undertaken – to provide the definitive study of hunger and re-feeding. Keys achieved this goal and also, unintentionally, he provided one of the most crucial insights into dieting and weight loss to this day.

The “Minnesota Starvation Experiment” started with an advert, posted across America in May 1944. “Will you starve that they be better fed?” Two hundred conscientious objectors volunteered, as an alternative to war, and Keys and his team of researchers whittled these down to 36 men. The men (all aged 20-33) were chosen for their physical and mental resilience. The results, 1,385 pages in total, were published in “The Biology of Human Starvation” (1950).

The year long experiment was split into four phases:
1) The Control Period (12 weeks): The key goal of this period was to determine the calorie requirement for the men. It was established that the men maintained their weight at approximately 3,210 calories a day whilst walking 22 miles each week – an average of just three miles a day (45-60 minutes walking).

2) The Starvation Period (24 weeks): The fact that the study was referred to as a “starvation experiment” is so interesting, because the six-month ‘starvation’ was actually a calorie controlled diet of approximately 1,600 calories per day (more calories than many modern diets allow). The meals were made up of foods typically available in Europe during the latter stages of the war: potatoes, turnips, bread and macaroni – i.e. starchy carbohydrates. Ancel Keys set out to try to induce a 25% weight loss in each man in 24 weeks.

3) Restricted Rehabilitation Period (12 weeks): The men were divided into four groups of eight (four had been dismissed for stealing food and binging) and given different calorie, protein and vitamin levels to see what would best re-nourish them back to health.

4) Unrestricted Rehabilitation Period (8 weeks): For the final period, the men could eat as much as they wanted and the research team carefully recorded what they did in fact eat.

This invaluable study tells us the following about dieting and weight loss:

1) Hunger is comparable with war in terms of the devastating effect it has on humans. Many of the volunteers came to believe that military service would have been an easier option than their chosen path.

Keys put 36 physically and mentally healthy men on a calorie controlled diet, with a moderate amount of exercise, and, in a matter of weeks, he turned them into physical and emotional wrecks (bulimics to all intents and purposes).

Physically, the men reported incessant hunger, weakness, exhaustion and they lost 21% of their strength in the first 12 weeks alone. They experienced dizziness, muscle wasting, hair loss and reduced coordination. Several withdrew from their university classes, because they simply didn’t have the energy or motivation to attend.

Psychologically, the men became obsessed with food, meal times and everything to do with eating (a number became chefs after the experiment; such was their interest in food). They had to ‘buddy up’ to avoid breaking their diets, as their drive to binge was so enormous. Before the buddy system was put in place, a couple did get hold of some forbidden food and binge and suffered extreme guilt and self-loathing as a result. (It is fair to assume, therefore, that, had this not been a confined experiment, all men would have given up on their ‘diet’). The men reported extreme depression, irritability, a sense of deprivation and they lost all interest in sex. (They actually lost all interest in anything other than food – such is the human drive to overcome hunger).

2) You may have heard of the saying “To lose 1lb of fat you need to create a deficit of 3,500 calories.” The Minnesota experiment alone renders this statement invalid.

The deficit, in Keys’ study, started off at 1,640 calories a day. Assuming that the deficit remained at 1,640 for the 24 week ‘starvation’ period, if the 3,500 formula were correct, during the 24 weeks, every man should have lost at least 78 pounds in fat alone and more on top of this in water and lean tissue. The average weight loss of the men was less than half of this – 37 pounds – 1.5 pounds per week. If the 3,500 formula were correct, the lightest man in the study, Bob Villwock from Ohio, should have finished the study below three stone (he would, of course, have died long before this).

3) The less you eat, the less you must continue to eat to have any chance of losing more weight and weight loss will stop, at some point, whether you like it or not.

As Keys showed, the men needed 3,200 calories, on average, to maintain their weight. As the men were given 1,570 calories a day in the ‘starvation period’, they lost weight and their energy need fell and therefore the calorie level needed to fall, to maintain the deficit.

Interestingly, Keys rejected the 3,500 formula from the outset and relied instead on adjusting the calorie intake every week to try to induce his desired weight loss of 25%. Keys found he needed to limit some men to 1,000 calories a day to try to induce further weight loss (the men should have been losing over 5lbs per week, at this calorie intake, having created a deficit of almost 2,500 calories a day from their original calorie need. In reality the body had adjusted energy need to resist any further weight loss).

All reached a plateau around week 20 and further weight loss could not be induced. At least one diary recorded weight gain in the final month of the ‘starvation’ period.

4) The body will do whatever it takes to reverse the effects of starvation/dieting.

During the restricted rehabilitation period, the four different groups of men were given 400, 800, 1,200 or 1,600 additional calories per day. Within each group of eight men, some were also given additional vitamin and protein supplements. Ancel Keys concluded that the only thing that determined the speed at which the men recovered was the calorie intake. The body didn’t respond to vitamins or protein – it just wanted the energy (calorie) deficit to be reversed.

It can be no surprise; therefore, that when given free access to food, in the final two months, the men overate and binged to correct the calorie deficit they had suffered. One man managed to eat 11,500 calories in one day and men still felt hungry consuming twice the number of calories that maintained their weight in the control period. They all gained all their weight back and approximately 10% more than they weighed before the experiment. Men who had previously shown no awareness of body size and image reported ‘feeling fat’.

Surely we have just observed the pre-requisite for an obesity epidemic? Eat less, get hungry, slow the metabolism, increase the desire to consume energy, reduce the desire to expend energy, put on weight, try to eat less and so on. We have certainly just described the Western World, since we started our obsession with calorie counting.

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18 comments on “The Minnesota Starvation Experiment
  1. avatar A dietitian says:

    This study is part of dietetic training.

    As a dietitian I would never be so unkind or unprofessional about your profession.

    • avatar nadia says:

      So what did you learn from reading about the experiment?

    • avatar MimiR says:

      She is entirely unprofessional because she can’t grasp the basics of the experiment. As you lose weight, your daily calorie expenditure drops. EVERYONE’S does. This is because it takes more calories to keep a bigger body running. So their deficit was not 1500 calories throughout the experiment. She even admitted this later when she saw that Ancel Keys had to adjust the deficit to keep up with the lower metabolism of a lighter body. At first, they ate MUCH MORE than 1500 calories–probably about 2,500, from their starting point and total weight loss.

      Plus, 3500 calories is for fat. Lean mass is lost with just 1800 calories of deficit per pound.

      To call them bulimic is absurd. They were being starved. They had the reactions of starved people.

      A dietician should be able to grasp these things.

  2. avatar Lianda says:

    It amazes me how people will read anything they want to find into research findings. Of course, you want to know how the study was done to make sure it wasn’t effected by researcher’s assumed and desired outcomes.

    But this study is very clear. Starvation diets are temporary measures to lose weight. The weight loss didn’t even fit into the “Law of Thermodynamics” or that the “eat less and exercise more” Taliban want you to believe is the only way to lose weight.

    I guess the bottom line is: You can lose weight, maybe not as much as you think you should; but at some point, unless you are in prison or a refuge camp, when you have access to food, the weight will come back as fast as you can get food into your mouth. And you are COMPELLED by your brain & physiology to replenish those lost calories.
    Dieting made those men temporarily insane by any standards. And think about how many women do that to themselves on a daily basis!
    For me: diets are a temporary measure to lose weight, make yourself fixated on food, and then assure you will gain back weight, plus additional insurance pounds in case of future dieting. It’s a recipe for obesity. How do I know? I did it for 35 years.

    • avatar Rachel says:

      Lianda, this is an odd comment. They were lean men being starved. No one who isn’t mentally ill does this on purpose. No one tolerates starvation. This doesn’t mean a calorie deficit. This means emaciation. If your BMI drops below 16 or so, you will be pretty desperate to eat to regain normal function. This doesn’t have a think to do with overweight people dropping into a healthy weight level with a sensible deficit. Yes, as soon as you drop under a BMI of 16, you will be miserable. But these men were at a BMI of around 21 to 22 to start with. The same distance from starvation for women is a BMI of 19 to 20. When they regained, they regained at first above their initial BMI because they had lost so much muscle mass. And they actually WERE fat. They were “skinny-fat.” Because fat is replaced with simple refeeding but not much muscle. It took them much longer to get back their previous weight and muscle level.

      If you’ve seen “refed” anorexics, you’d see how chubby they look at low weights. That’s because they are often denied exercise for fear that they were turn to exercise to try to lose weight instead of gain it. In my opinion, this is a dreadful mistake and every anorexic’s recovery should involve weight lifting to restore muscle mass. Otherwise, they are not only going to still be medically fragile, but they will be more likely to relapse due to the fact that they aren’t just fat in their minds but suffering from sarcopenic obesity, that is, being skinny-fat. And yes, you can be normal weight AND underweight and have sarcopenic obesity.

  3. avatar mae says:

    @Fatty: I do not see anywhere in that article where the men from the study stated that they would do it again. And seriously, who in their right mind would willingly choose high carb diet if they thought that they would lose their sex drive or be driven to dismember themselves?

    This way of eating is precisely why there is a current upswing in the number of obese individuals; individuals on anti-depressants; and why the buddy system is the only way to lose weight on a low fat/high carb diet.

    For many people on LCD or VLCD, the deciding factor in weight loss and stalling appears to be the ratio of protein to fat eaten daily. Adjustments made here tend to cause weight to be lost again or for a plateau to be maintained. Increasing good fats while lowering the amount of protein required as weight is lost tends to help. Counting calories tends to be less important than the ratio of fat/protein/carbs, and keeping fat at 80% or above makes the weight come off faster as long as protein intake does not go too high. And the more fat you have to lose, the larger the initial weight loss, until the inevitable stall occurs as the body adjusts.

    Exercise is not required, however the human body is designed for a certain level of exercise. It should be in the form of: sprinting several times a week; lifting heavy objects (try flipping a large tire in your back yard) or monkey bars to develop upper body strength.

    • avatar Ex-Anorexic says:

      As I believe you will not read this comments, I would like to set the record straight. They did say they would do it again, as it helped survivors of the war, it was a remarkable study, and they felt like they did something meaningful.

      “Sixty years later, Johns Hopkins interviewed the surviving study participants for their first-hand experiences and they all said they would do it again:

      [T]he men continued to look back on participation in the Minnesota Experiment as one of the most important and memorable activities in their lives. Wesley Miller reported, “It’s colored my whole life experience… [and was] one of the most important things I ever did… I’m proud of the work the Civilian Public Service did during the war.” Samuel Legg seemed to speak for all of the men when he commented, “I think probably most of us are feeling we did something good and are glad we did it, and that helps us live a better life.” ”

      Also, I did not understand your statement about high carb diet, as all of this experiment showed that it is not about the carbs or protein, but ourelu about calories. You can starve with high or low carbs, and you will lose your mind, sex drive, and perhaps fingers, by starving yourself. Even with low carbs.

      • avatar Rachel says:

        These are people who assume everyone’s overweight and weight loss is normally “good,” so they “must have been doing it wrong.”

        Weight loss in an already slender person is bad. For some of the men, it was close to deadly.

  4. avatar Carina says:

    Hm. I was 10 kilos more than now for most of my adult life. I decided to lose these 10 kilos 2 years ago, after I stopped breast feeding my son. I managed. Then I decided to stay that weight and not have another Jo-Jo effect any more. I managed. By weighing myself every day and strictly having 2000 calories a day. That sometimes felt like a diet, but it’s enough to occasionally allow me any treats I like to have. Admittedly, I exercised – I ran for 30 minutes every day. (I had been running before, I didn’t just start it then, I just did it more regularly.) And I probably really had on average a bit more than 2000. Then I got a degenerative tendinitis and couldn’t run any more, doctor forbade it. I gained 2 kilos but have, with the help of a calorie-counting app and an exercise bike, been able to maintain that even without doing my most beloved exercise. My body now seems to be actually adjusted to the new weight, it seems to be trying to stay at that 10-kilos-below weight that it hasn’t really had since I was in adolescence. My current weight is a ‘normal’ weight, even at the upper limits of ‘normal’. BMI. Before, I was overweight. And even though my weight is normal now — I do struggle to keep my waist circumference under 80 cms.

  5. avatar Nour Zibdeh, MS RD CLT says:

    Good article. But, why attack dietitians? There are many dietitians, including myself, who are very knowledgeable about this study. Have you ever read Intuitive Eating By Tribole and Resch?

  6. avatar Tora says:

    I first heard about this experiment a few years ago when studying with Dr George Blair-West. It should be compulsive study for anyone giving out weight loss advice.

  7. avatar Stefanie says:

    I am a dietitian and I have thoroughly studied this experiment and use it in my weight loss approaches.

  8. avatar Fatty says:

    Yet the volunteeres when followed up said they’d do it again and most returned to their pre study weight within a year or so, supporting the set point theory.

    Before rejecting the 3500Kcal/lb “myth” maybe a look at Kevin D. Hall What is the Required Energy Deficit per unit Weight Loss? would help. That and Key’s own findings that BMT`R slowed considerably so the defecit induced wasn’t the consumption at control period minus consumption during starvation.

    Key’s study showed evidence for the “startvation mode” that is that the body adapts to restriction, but this was only applicable in the subject group, fit healthy Lean men between 20 and 35. LCD ad VLCD studies in obese individuals show that this responce is lessened in individuals with a high percentage bofy fat at study start.

    Set point and leptin resistance studies support the idea that the body tries to reach equalibrium, with a 10% margine of error initally but settling back within a year. It also indicates around a 3 year period to re-set, but most diet study follow ups are poor and drop outs tend to be the re-gainers so the evidence is weak.

    Still it is a great bit of evidence, but I’m not sure you can show that your theory is fully supported by it. Low carb studies tend to be LCD/VLCD type within obese individuals and these don’t show the same issues around starvation.

    • avatar Rachel says:

      They returned to their old behaviors. Because they’d lost muscle, their old way of eating at first made them fatter (because fat is less metabolically active than muscle), and they felt fat because they were carrying close to twice the amount of fat that they had been going into the study. But after their old behaviors allowed them to slowly get their muscles back, their excess fat dropped off. Set point “theory” is bunk. Lifestyle rules. In this case, returning to a lifestyle that resulted in a lean BMI of 21 resulted in them returning to a lean BMI of 21.

  9. avatar Louise says:

    This is like reading my own diet story, I once did the cambridge diet for 3 week which restricts calories to about 500 a day, all i did for 3 week is think about food, i would day dream about all the foods i was going to eat when id return to normal eating. I even bought cookery magazines(id never done this previously or since) and cut out all the recipes i wanted to try, i was literaly salivating over the pictures. This diet also came to an end with an almighty binge!

    I have to add the cambridge diet cannot at all be good for you, i did lose 14lbs in 3 week but i literaly went saggy (not nice) but worse i was freezing , i could just not get warm and i constantly had a cold runny nose.

    • avatar Rachel says:

      This is not at all like your experience because they were emaciated. You, I assume, were still wanting to lose excess fat. But when you are hungry, you are hungry.

      Fad diets are stupid, and it’s impossible to get the nutrients you need for a long term diet in 500 calories a day. That rate of loss would increase muscle loss, too, unless you are extremely obese. There is nothing wrong with short-term fasts for health or religious reasons–people who fast are consistently shown to live longer than those who don’t–but any kind of long-term diet needs to be a sustainable lifestyle change, not something you do for a while before you go back to your old way of doing things. The old way of doing things is how you got fat. (In the Minnesota case, though, it’s how they were healthy, so when they went back, they got healthy again!)

  10. avatar hcufflin says:

    Wow. If only these were the sort of things our children were taught in school.

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