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What does the Minnesota Starvation Experiment tell us about the psychological impact of severe calorie restriction?

Updated: Jan 17

Embarking on a weight loss journey has traditionally involved severe calorie restriction. However, this practice can have profound psychological effects over the long term. The Minnesota Starvation Experiment, a landmark study conducted during World War II, provides valuable insights into the psychological aspects of prolonged calorie restriction and offers guidance on how individuals can mitigate these challenges.

 


Sad woman in a field of wheat

The Minnesota Starvation Experiment: Unveiling the Psychological Toll


Conducted from 1944 to 1945, the Minnesota Starvation Experiment aimed to investigate the physiological and psychological effects of severe calorie restriction on healthy individuals. Led by researcher Ancel Keys, the experiment involved 36 physically and mentally healthy men who volunteered to participate in the study. The participants were subjected to a semi-starvation diet for 6 months, consuming approximately 1,560 calories per day, which was roughly half of their estimated caloric needs. The diet primarily consisted of foods commonly available in war-torn Europe at the time. (Note that consuming 50% of normal calories per day was regarded as a ‘semi-starvation diet’. Many people on low-calorie diets today reduce their calorie intake by much more than 50% and for much longer than 6 months!).


Physical Consequences

As expected, the participants experienced significant physical changes, including drastic weight loss, decreased muscle mass, and reduced metabolism. These findings highlighted the body's adaptive responses to calorie restriction, emphasizing the importance of understanding both the physiological and psychological aspects of such dietary interventions.

 

Psychological Effects Observed

The findings from the Minnesota Starvation Experiment shed light on the various psychological effects of prolonged calorie restriction (see if you recognise any of these symptoms in yourself when you have previously followed low-calorie diets):


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1. Irritability and Emotional Distress: Participants exhibited heightened irritability, anxiety, and emotional distress during the semi-starvation phase. The constant preoccupation with food and the sensation of hunger led to increased tension and irritability.


2. Obsessive Thoughts about Food: A significant psychological consequence was the development of obsessive thoughts about food. Participants reported an overwhelming preoccupation with recipes, cooking, and the anticipation of meals.


3. Social Withdrawal: The psychological strain extended beyond individual experiences, as participants withdrew socially. Interpersonal relationships suffered as a result of the intense focus on food and the emotional challenges associated with calorie restriction.


4. Depression and Apathy: The semi-starvation phase induced symptoms of depression and apathy among participants. This was attributed to a combination of physiological changes and the psychological toll of sustained hunger.


5. Cognitive Impairments: Cognitive functions such as concentration, alertness, and memory were compromised during the experiment. Participants reported difficulties in maintaining focus and processing information efficiently.


6. Binge Eating Behaviour: One striking observation was the emergence of binge eating behaviour during the rehabilitation phase when participants were allowed to eat freely. Many individuals reported consuming large quantities of food in a short period, reflecting a compensatory response to the prolonged deprivation experienced during the calorie-restricted phase.


7. Changes in Body Image Perception: The experiment also revealed changes in body image perception. Participants developed a distorted view of their bodies, often seeing themselves as underweight despite significant weight loss. This highlights the role of psychological factors in shaping body image and the potential negative consequences of persistent calorie restriction on self-perception.

 

Understanding these psychological disturbances during severe calorie restriction


To comprehend the psychological effects of long-term calorie restriction, it is crucial to explore the underlying mechanisms driving these changes. Several key factors contribute to the intricate interplay between calorie intake and mental well-being.


Food and cup of coffee place on cable knit jumper with book saying 'my brain has too many tabs open'


Neurotransmitter Regulation: Caloric intake influences the production and function of neurotransmitters, the chemical messengers in the brain that regulate mood and behaviour. Prolonged calorie restriction may lead to alterations in serotonin and dopamine levels, contributing to mood disturbances and changes in reward processing related to food.


  • Serotonin and Mood Regulation: Serotonin, a neurotransmitter associated with mood regulation, is influenced by dietary factors. Calorie restriction can reduce serotonin synthesis, potentially contributing to feelings of depression and anxiety observed in individuals undergoing prolonged dietary restrictions.

  • Dopamine and Reward Processing: Dopamine, a neurotransmitter involved in reward processing, plays a crucial role in the brain's response to food cues. Calorie restriction can lead to heightened responsiveness to food-related stimuli, potentially contributing to the obsessive thoughts and preoccupation with food observed in the Minnesota Starvation Experiment.

  • Hormonal Changes: Calorie restriction triggers hormonal responses aimed at conserving energy and maintaining metabolic stability. These hormonal changes, including alterations in ghrelin, leptin, and cortisol levels, can influence hunger, satiety, and stress responses, contributing to the complex psychological landscape during calorie restriction.

    • Ghrelin and Hunger: Ghrelin, often referred to as the "hunger hormone," increases during periods of calorie restriction. Elevated ghrelin levels signal the brain to increase food intake, contributing to the heightened feelings of hunger observed in individuals undergoing prolonged calorie restriction.

    • Leptin and Satiety: Conversely, leptin, the hormone responsible for signalling satiety, decreases during calorie restriction. Reduced leptin levels can disrupt the normal regulation of appetite, leading to increased food-seeking behaviour and potential overconsumption during refeeding phases.

    • Cortisol and Stress Response: Calorie restriction can also elevate cortisol levels, the body's primary stress hormone. Elevated cortisol may contribute to increased anxiety and mood disturbances observed in individuals undergoing prolonged dietary restrictions.

 

  • Evolutionary Perspectives: From an evolutionary standpoint, the psychological responses to calorie restriction can be seen as adaptive mechanisms designed to ensure survival during periods of food scarcity. The heightened focus on food, increased motivation to seek high-calorie sources, and alterations in mood and behaviour may have conferred a survival advantage in ancestral environments where food availability was unpredictable.

 


A soft toy in shape of a half avocado sitting against a green wall with a smile on its face

Preventing Psychological Challenges during Calorie Restriction


It is clear that severe calorie restriction is not the best way to lose weight in the long term (or even the short term). So, how can individuals prevent or mitigate these issues while striving for weight loss? Several strategies can be employed:


1. Gradual Calorie Reduction: Instead of drastic calorie cuts, opt for a gradual reduction in daily intake. This approach minimizes the shock to both the body and mind, allowing for a more sustainable adjustment.


2. Nutrient-Dense Foods: Prioritize nutrient-dense foods to ensure that the body receives essential vitamins and minerals. This not only supports overall health but may also positively impact mood and cognitive function.


3. Regular Monitoring and Support: Regular check-ins with healthcare professionals or nutritionists can provide guidance and emotional support during the weight loss journey. Monitoring physical and mental well-being is crucial to identifying potential issues early on.


4. Incorporate Variety: Including a variety of foods in the diet can help alleviate monotony and reduce obsessive thoughts about specific foods. This approach may also prevent nutritional deficiencies associated with restrictive diets.

 

Low-Carb Diets: a focus on nutrients rather than calories


Beyond general strategies, exploring specific dietary approaches, such as low-carb diets, may offer additional benefits in mitigating the psychological effects of long-term calorie restriction:


  • Stabilizing Blood Sugar Levels: Low-carb diets, such as the ketogenic diet, emphasize the reduction of carbohydrate intake, leading to stabilized blood sugar levels. Fluctuations in blood sugar can contribute to mood swings and irritability, so maintaining stability may help mitigate these psychological effects.

  • Focus on nutrient density: Low-carb diets focus on eating foods that are nutrient dense, i.e., they contain a broad range of vitamins and minerals, many of which are crucial to the metabolism of fat for energy and the metabolism of protein for muscle building - both of which enable sustained and healthy weight loss.

  • Enhanced Cognitive Function: Some studies suggest that low-carb diets may have cognitive benefits, including improved focus and mental clarity. By providing an alternative energy source (ketones) to the brain, these diets may help counteract cognitive impairments associated with calorie restriction.

  • Appetite Suppression: Low-carb diets have been linked to increased feelings of satiety. This can be particularly beneficial during calorie restriction, as individuals may experience less intense hunger and reduced preoccupation with food.


  • Maintenance of Metabolic Rate: Due to a higher protein intake, low-carb diets can help to minimise the fall in metabolic rate that generally occurs on low-calorie diets. To fully maximise this effect it is important to include regular resistance training to prevent muscle wastage and improve muscle building.

  • Potential Impact on Mood: While more research is needed, some studies suggest that low-carb diets may have positive effects on mood. The mechanisms behind this are not fully understood but could be related to the influence of ketone bodies on brain function or may act through improvements to the gut microbiome, enhancing serotonin production (90-95% of serotonin is made in the gut and then transported to the brain via the gut-brain-axis).

Conclusion


Embarking on a weight loss journey often involves navigating the complex interplay between physical and psychological factors. The Minnesota Starvation Experiment provides valuable insights into the profound psychological effects of long-term calorie restriction. By adopting gradual approaches, monitoring well-being, and considering dietary strategies such as low-carb options, individuals can better navigate the challenges associated with weight loss, ensuring a more sustainable and mentally resilient journey.

 

Reference

The Minnesota Starvation Experiment:

 Keys, A., Brožek, J., Henschel, A., Mickelsen, O., & Taylor, H. L. (1950). The biology of human starvation (Vol. 1-2). University of Minnesota Press.

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