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The Minnesota Starvation Experiment

This is a blog about quite possibly the most important obesity experiment ever conducted.

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.

40 thoughts on “The Minnesota Starvation Experiment

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  • Hi Dr. Zoe,

    I really your piece on the Minnesota Starvation Experiment. Just wanted to let you know that I, a dietitian nutritionist, have definitely heard of this experiment as many dietitian nutritionist in the US have. I have been talking to my clients about this experiment since I became a dietitian nutritionist in 1997. Just wanted to let you know that dietitian nutritionists are enlightened individuals, not food cops. Also wanted to let you know your simple, clear summary of the experiment is well-written and I have shared it with clients, with all credits to you attached. ( I have shared the link to the post.) I have held discussions about the experiment in group settings, in which I hoped would help people stop dieting! Diets don’t work!

    • Hi Carol
      I do apologize and I’ve deleted the sentence. This was written 8 years ago and I hadn’t spotted it needed updating. I have since then met and worked with a number of dietitians who are doing great work. I’ve not heard the term dietitian/nutritionist before? Enlightened sounds good!
      Best wishes – Zoe

      • Hi Zoe, Sorry for the long delay in replying. I am getting ready to share your article with someone and I just wanted to check and see the link still works. Thank you so much for your understanding and support! Here’s a little explanation about “dietitian nutritionist.” The professional organization for dietitians nutritionists, the Academy of Nutrition and Dietetics (AND) has re-branded dietitians as dietitians nutritionists or RDNs, registered dietitian nutritionists. Dietitian (RD) is still used by many. In many states in the US, a state license is required to operate as an RD or RDN. Only RDs or RDNs can obtain a license in my state. The addition of nutritionist is an attempt, IMHO, to “protect” the term nutritionist and to separate RDNs from those self-proclaimed nutritionists who may or may not have a rigorous education, etc. Additionally, much confusion exists in the public arena about the difference between a “dietitian” and a “nutritionist.” I get that question a lot. AND wants the public to know, “All dietitians are nutritionists, but not all nutritionists are dietitians.” RDNs complete a minimum of 4 years of college (most RDNs have masters degrees), must participate in a supervised onsite internship, and must pass an exam before getting the RDN credential. Additionally, RDNs must participate in at least 75 hours over 5 years of continuing education to maintain the credential. Thank you again for your support!

  • Thanks Zoe.
    To my previous post, I should perhaps state my age. I was 33 when I first found and studied fasting. This year (2016) I will be 54.
    One of the things I have a while to find out if true, is the extended longevity issue/claim. Restricted calories, fasting, etc., have been reported many times to increase longevity in many animals, mice and rats for example. I hope to report back when I’m 150yrs old!

    • Yes, rats who are deprived of calories do live longer. And recently, research has been done on restricting calories and fasting with improving cancer treatment outcomes. However, eating is one of the most pleasurable activities we do as humans. For those not going through cancer treatment, ask yourself: Is life worth living, especially living longer, if you are constantly restricting calories and fasting?

  • Fasting and starvation are two separate issues. I built up a fasting regime and managed longer and longer fasts. I always felt healthy on these fasts, with a lot of niggly small health issues going away. My eyesight, skin, energy levels, occasional heart palpatations, and many other minor negatives, improved or disappeared completely. On one fast, way back, of 21 days, toward the end, say last few days (maybe a week) I started sprinting a 100m, many times a day, I felt so good and full of energy.

    I fasted for the whole of Feb 2004, no food, only water with a little salt and squeeze of lemon juice. It was the best and gave me a most wonderful spiritual experience/feeling I will never forget.

    After 2004, I didn’t get to fast for ten yrs or more, all the time wanting to do another. Eventually I decided and managed to fast again, somewhat apprehensive of the effect of not fasting for so long. This last Feb 2016, the whole month. On this fast I did however have a couple of (2 or 3) bitter almonds a day for about half of it. I also experimented with a little bicarb of soda and sea salt in the water I drank. All the usual benefits occured.
    There is a rebound weight gain but that adjusts itself and you end up back where you started. I did not fast to lose weight only/exactly – I also wanted to feel the amazing clarity, health, etc.. I believe long term health is improved, for instance, arteries. Although I could not see the condition of my arteries and plaques therein, judging by the other issues that improved, I am confident that a lot of invisible good took place. I will be disciplining myself to fast more regularly, like one a year – an extended fast – at least a month. I think I can go longer. I try to listen to my body when fasting as it is said that your body tells you when the fast is over – after that, if you keep going, you are starving yourself. It takes a lot of faith that you are doing the right thing, that fasting is OK and not just OK but one of the best healing practices ever. All that I’ve read, admittedly old physician books of the alternative physician of 1800, 1900s, talked of the benefits of fasting and gave many real patient evidence and experimentation of a sort. They did some great work, I’d recommend anyone to read those. I relied on these to reassure myself that I wasn’t injuring my health, sustaining untold irreversible damage to my organs, etc., etc.. I am confident in this practice and proved it to myself and thus anyone prepared to believe me and try this themselves. I’m sure it will benefit all human beings to do this – although timing might be important and paradoxically some may be too ill to do it. There are some circumstances where fasting would not be recommended, others where other treatment, cures would be needed before a fast may be undertaken. I would like to say/disclaim by saying consult a medical doctor for advice or supervision of the fast, but in general it seems most in the medical profession haven’t a clue. Most doctors would say you are crazy to fast for a week, let alone a month. You would have to find the right doctor or be strong and decide for yourself, do it and just let common sense guide the rest. I, for instance, took my blood pressure every day, sometimes two or three times. On a fast you will feel light headed if you rise from sitting too fast, for instance. My blood pressure dropped to around 95/65. It is normally a little under the average anyway, like 110/70. I think this is a good indicator of how you are doing, once fasting, to have a steady state after a short while.
    For what it is worth, I share my experience/experiment.

    • Hi Neil
      Many thanks for sharing this and you’re right – fasting and starvation (or low cal dieting, as this was) are very different. If you haven’t come across Dr Jason Fung yet – he’s a huge supporter of fasting and has many many reasons as to why. Click on fasting on the tag cloud on the right hand side on his site
      Best wishes – Zoe

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  • This study is part of dietetic training.

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

    • 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.

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  • 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.

    • 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.

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  • @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.

    • 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.

      • 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.

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  • 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.

    • I only wish I can eat 2000 calories. I am eating 1200 now and I gained three pounds from eating 3 oz of ham.

      • I do hope you have had a thyroid test done? If you are deficient in thyroxine, however little you eat, you can still gain weight, as well as suffer from slower thinking, excess fatigue unrelieved by sleep, drier skin, and possibly losing hair too. Oddly you would almost certainly lose the outer third of your eyebrows too. If most/all of the above seem to apply to you, then please get your thyroid function tested.

  • 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?

    • Thank you Nour! I am a dietitian nutritionist too. I as well, have studied this study!
      Maybe she didn’t mean to attack dietitians per se – perhaps she thinks of dietitians as food cops, thus made an assumption based on that perception. Please people — dietitians aren’t food cops!

  • 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.

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

  • 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.

    • 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.

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  • 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.

    • 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!)

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

    • Now there’s a thought! Why are no dietitians hired to go into public schools like the school nurse? At least, not in South Carolina, they aren’t hired to teach in the classrooms or consult. Please correct me if I am wrong. However, schools have social workers, counselors, nurses, and I am sure more than I am thinking of now, but where are the dietitians? Planning the school lunch menu based on Federal guidelines? Another assumption is that anyone can teach nutrition. It’s often left to nurses to teach nutrition. While nurses are totally intelligent, they don’t get the amount of nutrition education that a dietitian nutritionist does. I was very popular when I gave nutrition classes in cardiac rehab years ago — with the nurses! The cardiac Nurses who were teaching the patients in a home health setting, bombarded me with questions about diet every day until I started coming in early once in a while and held a nutrition meeting for the nurses so they could ask me their questions and I could do the work I was hired to do! Some of the questions nurses asked me indicated to me that they did not have enough knowledge to teach patients nutrition in the home health setting. Yet, insurance companies do not pay dietitians to go in the home health setting. Maybe this is changing, but not in South Carolina — unless it’s specialized like starting an insulin pump and then the pump company pays.

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