The Minnesota Starvation Experiment
This week I want to take you back to 1944 when the Minnesota Starvation Experiment was conducted. This was a study designed to determine the effects of starvation on the body and the mind. The original goal was to help famine victims at the end of World War II, when lack of food was a problem around the world.
It’s a fascinating study to read about. They recruited 36 conscientious objectors of World War II, all young, lean and healthy men. They subjected these men to three different phases:
Phase 1 involved 12 weeks of normal living and eating – during this phase, the men ate just over 3000 calories per day on average. This amount kept their weight stable during this time period. The data collected during this phase defined the baseline physical and mental health of the participants.
Phase 2 involved 24 weeks of semi-starvation – this phase was designed to create a 25% loss of body weight in the participants. So for a 170-pound man, for example, this would mean a 43-pound weight loss, bringing his weight down to 127 pounds. During this phase, the participants ate around 1500 calories per day (about half of the calories the men ate in Phase 1 to maintain their weight). They also continued their regular exercise, which included 22 miles of walking each week. The diet was structured to resemble was people in Europe were likely eating at that time, namely two meals each day that were rich in carbohydrates and low in protein. Examples of foods eaten were macaroni, potatoes, and cabbage.
Phase 3 involved 12 weeks of restricted re-feeding followed by 8 weeks of unrestricted re-feeding – in this phase, the researchers divided the men into four different groups. In the first group, the men increased their daily intake by 400 calories; by 800 calories in the second group; 1200 calories in the third group; and 1600 calories in the fourth group. All the men also received vitamin and protein supplements. After the 12 weeks, all men were allowed to eat as much as they wanted, which ended up being a whole lot.
So here is what the researchers found:
During the weeks of semi-starvation, the men lost about 30% of their body fat and had a 20% decrease in their strength. Their heart rates slowed down from an average of 55 beats per minute (bpm) to about 35 bpm. This suggests that their metabolism was slowing down to decrease the amount of energy they needed to burn while at rest. Essentially, their bodies were conserving energy so they could survive a famine for a longer period of time. Other signs that this was happening was decreased blood volume in the body and a decrease in the size of the heart.
The men also developed brittle hair, and many of them lost hair. The men reported that they felt less coordinated, complained of various aches and pains, and felt less comfortable sitting down. They also felt cold, which makes sense given the decrease in metabolism and body fat.
But the changes the men experienced were more than just physical. Of course, we all know how cranky we can get if we haven’t eaten in a while. So unsurprisingly, the men complained of feeling old and tired, having a decreased sex drive and feeling very irritable, especially if they had to wait too long for food. In other words, they got “hangry.” They also became rather obsessed with food and were reported to constantly look at cookbooks and pictures of food.
Here was another interesting finding: the men were allowed to drink coffee and chew gum at their leisure, and during the semi-starvation phase of the study, the men would chew up to 40 packs of gum per day and drink up to 15 cups of coffee.
Also interesting was that as the men lost weight, they didn’t see themselves as being too skinny, but rather they thought other people looked more fat, which is something often found in people with anorexia.
Things got even more fascinating when the researchers started re-feeding the men. When the men were allowed to eat what they wanted, they ate up to 11,000 calories per day!
The researchers continued to follow the men after the study was over. Participants reported abnormal eating patterns for months to years after the study and most of them gained more weight than what was healthy for them at baseline. Some of the participants endorsed being fearful that food could be taken away from them again, and this contributed to their abnormal eating behaviors.
Many years later, in 1997, researchers at the University of Switzerland looked at the data from 1944 and found that the men’s body fat returned to 100% of their baseline levels faster than lean muscle mass did. Unfortunately, they found that as long as the lean mass was lower than their baseline, they continued to naturally overeat. When they eventually did gain all their muscles back, they had about 180% of their baseline levels of fat.
So what does this all mean for us now in 2021?
Well, first of all, this tells us that our bodies are programmed to defend us against calorie restriction. And it doesn’t necessarily need months of starvation, like the men experienced in this study, to trigger this response. This defence mechanism can kick in even if you’re just trying to lose a few pounds.
Second, when you lose weight, your metabolism slows down, and it slows down more than you’d expect it to. What this means is that your body will require less calories to maintain your new weight than someone who’s been at that same weight for their adult life. This is called metabolic adaptation, and it’s one of the reasons why it’s so darn hard for us to lose weight and keep it off.
Third, we know that when people regain weight after they’ve lost it, they end up with more body fat and less muscle than they had originally. And even though this is very frustrating for us when it happens, it also makes a lot of sense. Fat provides more energy than muscle, so to protect you against times of famine in the future, your body is going to want to hold on to the fat.
Fourth, restrictive diets have a negative impact on mental and emotional health. Your brain quite simply hates not having food, and it’s going to tell you that by making you feel irritable, angry and hungry. On top of this, restrictive approaches to dieting can often backfire, meaning that when we stop dieting, we often start eating more than ever.
Finally, it’s important to remember that how we lose weight is much more important than how quickly we lose it. Most of us who have weight to lose want to lose it as soon as possible, but it’s important that we take a healthy approach so that we lose fat and not muscle mass, so that we do it without mental or emotional suffering, and so that we do it in a way that allows us to continue enjoying life. Really what this means is turning towards eating wholesome foods in healthy amounts and incorporating movement to maintain muscle mass.
Kalm LM, Semba RD. They starved so that others be better fed: remembering Ancel Keys and the Minnesota experiment. J Nutr. 2005 Jun;135(6):1347–52.
Eckert, E. D., Gottesman, I.I., Swigart, S.E., Casper, R.C. (2018). A 57-Year follow-up investigation and review of the Minnesota Study on human starvation and its relevance to eating disorders. Archives of Psychology, 2(3), 1-19.