The Minnesota Starvation Study, led by Ancel Keys in 1944-1945 during World War II, is a fascinating study, which is constantly referred to in weight loss and obesity medicine circles. Keys rounded up 36 healthy male volunteers to study the physical and mental effects of what he called “semi-starvation” because of the soldiers and civilians across Europe who were chronically underfed as a result of the war. Its findings have a lot to say about the impact of dieting and calorie restriction on our bodies and minds, which I want to explore further today.
Details of the Minnesota Starvation Study
Ancel Keys made sure the 36 male volunteers met specific criteria in terms of their health and baseline eating habits before joining the study. This study spanned an entire year, during which time these men lived in a controlled environment and adhered to very strict guidelines regarding calorie intake, activity, and testing.
For the first 12 weeks they were in a control period. Then came the six-month semi-starvation period, where they had to survive on just half of their usual daily calorie intake. Finally, they entered a 12-week rehab phase.
The impact of this semi-starvation on these men included cognitive and emotional changes, medical and physical changes, and some of the symptoms they experienced even echoed those suffered by people with disordered eating.
It’s worth noting that the men were still getting 1570 calories per day, which is still more than what many modern diets recommend. Some of these mental and physical effects lasted for years, raising serious questions about the harm we might unknowingly be causing ourselves when we willingly put ourselves through diets.
Cognitive effects during the semi-starvation period
The cognitive effects of this study manifested quickly. Within days of the semi-starvation diet, behaviors were even starting to resemble patterns seen in individuals with restrictive eating disorders like anorexia. Participants reported difficulty concentrating, foggy thinking, and being unable to problem solve like before. They became obsessively preoccupied with food, collecting recipes, and even discussing food during social activities, and while watching movies.
Many participants began having intrusive thoughts about food, which I find fascinating as so many of the women that come to me for coaching talk about their desire to stop thinking about food all the time. And so if you are hyper-focused on food and thinking about it all the time, there is a good chance that you might not be nourishing yourself appropriately. The men in the study would find themselves thinking about food even when they really didn’t want to be, which was quite distressing to the point where sometimes they would even dream about food.
Decreased motivation and discipline were noted, not just related to food but in general tasks. Early in the study, many began eating incredibly slowly, stretching meals for hours to create the illusion of more food. Hoarding, stealing, and hiding food became common behaviors, with participants becoming possessive and some even aggressively defending their portions. They constantly compared each other’s calorie allowances, and some went to great lengths to obtain forbidden foods, like sneaking out to buy ice cream.
Participants increased their coffee and gum consumption, often chewing gum so vigorously that they developed mouth sores. Smoking also became a coping mechanism for some during the calorie restrictions. These cognitive and behavioral shifts occurred early in the six-month semi-starvation period, showing the profound effects of dietary practices like this.
Emotional challenges during the semi-starvation period
Nearly all 36 participants in the study experienced an increase in symptoms of depression and anxiety. Many reported feeling despondent, apathetic, and indifferent towards various aspects of life, including dating. Even extroverted individuals became introverted, losing interest in normal social activities. Irritability and easy annoyance became common, with minor issues triggering intense reactions that were rare before the study.
Interestingly, there was a strong emotional response to food wastage. Participants expressed anger and frustration when food was discarded in the cafeteria or removed from serving plates. This observation parallels concerns about food wastage in individuals who struggle with disordered eating, leading to questions about whether this reaction is linked to an underlying hunger when we underfeed ourselves during restrictive diets.
Medical complications during the semi-starvation period
During the six-month period of semi-starvation, the participants experienced a range of medical complications. These symptoms started early in the study and were quite predictable:
- Gastrointestinal Discomfort
- Decreased Need for Sleep
- Hair Loss
- Metabolism: Universally, their metabolism slowed down, with a basal metabolic rate decreasing by approximately 40%. This aligns with findings from modern studies on calorie restriction and its impact on metabolism.
- Cold: Participants felt very cold, potentially due to their decreased calorie intake and lower body fat.
- Fatigue: Extreme fatigue was reported, making even simple tasks like climbing stairs feel strenuous.
- Edema: Swelling, particularly in the ankles, faces, and knees, occurred quite rapidly.
- Muscle Loss: Along with the 25% loss in body weight was a loss in muscle mass of 40%. This muscle loss, combined with reduced calorie intake, contributed to their overall fatigue and weakness.
These medical complications underscore the severe physical toll of the semi-starvation diet, shedding light on the dangers of such practices and the importance of considering the potential health risks associated with restrictive eating habits.
Findings from the 12-week rehabilitation period
In the final three month rehabilitation period, they worked to bring the men back to their baseline caloric intake. One group was allowed an unrestricted diet, while the other three groups were provided with specific calorie targets that increased weekly to reach their baseline levels.
The group with unrestricted intake experienced significant challenges. They consumed as much as 7,000 to 10,000 calories a day, losing touch with their hunger and fullness cues. Participants described feeling physically full but still experiencing intense hunger, leading to episodes of overeating. One individual had to be hospitalized for gastric distension due to excessive eating. Some participants continued to struggle with binge eating or overeating for years after the study, feeling out of control around food.
This finding raises questions about the impact of modern-day calorie restriction in a food-rich environment and whether it contributes to feelings of food-related loss of control. Many participants in the rehabilitation phase reported weight gain beyond their initial study weight, with an average increase of 22 pounds, and some never returned to their pre-study weight.
Remarkably, a follow-up study conducted 57 years later revealed that binge eating or overeating persisted for years in several participants, and some even changed their professions to become chefs due to their ongoing preoccupation with food.
The Minnesota Starvation Study really illustrates just how harmful dieting can be to our emotional, physical, and mental health. We willingly put our bodies through diet after diet in the hopes of losing weight, despite knowing that these things might be the cost and the consequences are long term. So here’s what I want you to ask yourself:
Are any of these symptoms or side effects of calorie restriction showing up in your life in any way?
If they are, I encourage you to take a look at how dieting culture is showing up in your life, and whether or not you are actually eating enough to support your metabolism and properly nourish your body so that it can function as it needs to.
If you are experiencing any symptoms similar to the ones that these men experienced during the semi starvation phase, please reach out to me and let me know. You can email me at firstname.lastname@example.org and I’d love to hear from you.
Resources mentioned in this blog:
- Ancel Keys
- “The Minnesota Semi-Starvation Experiment: What It Teaches Us About Eating Disorders” by Samantha DeCaro, PsyD
- “The Starvation Experiment” by Chantal Gil, PsyD