Why diets backfire - the science behind set point theory

Contestants from "The Biggest Loser" still had damaged metabolisms six years later. Here's what groundbreaking research reveals about why diets backfire and what your body is really trying to tell you.

Set Point Theory

Set Point Theory proposes that the body has a biologically determined weight range that it actively defends through physiological mechanisms. This theory suggests that our bodies maintain a relatively stable weight over time through complex interactions between genetic, metabolic, hormonal, and neurological factors that are largely outside of conscious control.

The theory posits that when body weight deviates significantly from this predetermined range, the body initiates compensatory mechanisms to return to its "set point" or more accurately, its "set range." These mechanisms include changes in metabolic rate, hunger and satiety signals, food preoccupation, and energy expenditure.

‍

Evidence Supporting Set Point Theory

Metabolic Adaptation During Caloric Restriction

The most robust evidence for set point theory comes from studies demonstrating metabolic adaptation during periods of energy restriction:

The Minnesota Starvation Study (1944-1945) remains the landmark research in this field. Keys et al. (1950) followed 36 healthy men through a 24-week period of restricted intake, documenting dramatic reductions in metabolic rate (up to 40% below predicted levels), increased food preoccupation, psychological changes, and rapid weight regain during the re-nourishing phases.

Contemporary Research has consistently replicated these findings:

• Leibel et al. (1995) demonstrated that both weight loss and weight gain trigger compensatory changes in energy expenditure that persist long after weight stabilisation
• Rosenbaum & Leibel (2010) showed that metabolic adaptations can persist for years after weight loss
• The Biggest Loser study (Fothergill et al., 2016) found that contestants maintained significantly suppressed metabolic rates six years post-competition, despite substantial weight regain

Hormonal Regulation of Body Weight

Multiple hormonal systems work together to defend body weight:

Leptin and Adiponectin: These adipose tissue-derived hormones signal energy stores to the brain. During weight loss, leptin levels decrease and adiponectin increases, promoting hunger and reducing energy expenditure (Klok et al., 2007).

Ghrelin and GLP-1: Ghrelin (the "hunger hormone") increases during weight loss, while GLP-1 (a satiety hormone) decreases, creating a biological drive to regain weight (Sumithran et al., 2011).

Thyroid Hormones: T3 and T4 levels decrease during caloric restriction, contributing to metabolic slowdown (Danforth et al., 1979).

Clinical Evidence from Eating Disorder Treatment

Research in eating disorder recovery provides compelling evidence for set point theory:

• Studies consistently show that weight restoration to a BMI of at least 20-21 is necessary for psychological and physiological recovery from restrictive eating disorders (Garner & Garfinkel, 1997)
• Research indicates that attempting to maintain weight below an individual's set range perpetuates eating disorder symptoms (Walsh, 2013)

‍

Limitations and Nuances of Set Point Theory

‍

Set Range vs. Set Point

Current research suggests the body defends a weight range rather than a fixed point, typically spanning 4-9kg (Keesey & Hirvonen, 1997). This range can shift over time due to:

• Age-related changes
• Hormonal fluctuations (puberty, pregnancy, menopause)
• Medications
• Environmental factors

‍
Individual Variability in Adaptive Responses

The magnitude of metabolic and hormonal adaptations varies significantly between individuals:

• Some people show more pronounced metabolic suppression than others (Camps et al., 2013)
• Genetic factors influence the degree of adaptive response (Bouchard et al., 1990)
• History of repeated dieting may enhance adaptive mechanisms (Brownell et al., 1986)

‍

Complexity of Hunger and Satiety Signals

While set point theory predicts increased hunger below set weight, clinical reality is more complex:

• Chronic restriction can initially suppress hunger signals due to adaptation
• Eating disorder thoughts and behaviours can override biological hunger cues
• Stress, anxiety, and other psychological factors significantly influence appetite regulation
• Some individuals at higher weights report persistent hunger due to disrupted satiety signaling

‍

Clinical Observations and Weight Trajectory Patterns

The Weight Suppression Phenomenon

Clinical experience suggests that individuals with a history of chronic dieting often experience initial weight gain when transitioning to adequate nutrition, followed by gradual weight reduction (in those who are not underweight) over 18-24 months as metabolic function normalises. This pattern has been observed in:

• Eating disorder recovery (Mehler & Brown, 2015)
• Post-diet weight trajectories (Mann et al., 2007)
• Metabolic rehabilitation programs

This phenomenon may reflect the body's need to:

• Restore depleted energy stores
• Repair metabolic damage from chronic restriction
• Re-establish normal hormonal function

Implications for Treatment and Body Acceptance

Working with Set Point Rather Than Against It

Evidence suggests that sustainable health and well-being come from:

• Accepting one's natural weight range rather than fighting it
• Focusing on health behaviours rather than weight outcomes
• Understanding that genetic factors play a significant role in body size and shape

The Role of Weight-Inclusive Care

Healthcare approaches that acknowledge set point theory include:

• Health at Every Size (HAES) principles (Bacon & Aphramor, 2011)
• Weight-neutral treatment approaches
• Focus on metabolic health markers rather than BMI alone

The Implications for 'Atypical' Anorexia Nervosa

For clients who restrict but maintain higher weights, their bodies may have simply adapted faster or they started from a higher baseline. The psychological and physiological symptoms are identical to those at lower weights, requiring the same intensive treatment approach.

Finding Professional Support

Individuals seeking to understand and work with their set point should consider working with:

• Registered dietitians specialising in eating disorders and intuitive eating
• Mental health professionals trained in body acceptance and eating disorder recovery
• Healthcare providers familiar with weight-inclusive care approaches

‍

Preparing for Set Point Acceptance

It's important to understand that your natural set point may be:

• Higher than cultural ideals or personal preferences
• Higher than family members or peers
• Higher than previous weights achieved through restriction
• Different from medical recommendations based solely on BMI

Professional support around body acceptance, weight stigma, and intuitive eating can be invaluable in this process.

‍

Conclusion

Set Point Theory is currently our best understanding of why long-term weight control through caloric restriction is so difficult and often counterproductive.
While the theory continues to evolve with new research, the evidence consistently points to the body's remarkable ability to defend its preferred weight range through multiple biological mechanisms.

Understanding and accepting these biological realities can be liberating for individuals trapped in cycles of dieting and weight regain, offering a path toward a more peaceful relationship with food and body weight.

‍

Download our free resource:

Stop Fighting Your Body and Start Working With It: A Guide to Set Weight Theory which explores how to end the exhausting battle against biology. This resource explains why restriction slows metabolism and increases food preoccupation, and how understanding these protective mechanisms becomes the key to working with their body instead of against it for lasting peace and health.

‍

References

Bacon, L., & Aphramor, L. (2011). Weight science: evaluating the evidence for a paradigm shift. Nutrition Journal, 10(1), 9.

Bouchard, C., Tremblay, A., Després, J. P., Nadeau, A., Lupien, P. J., Thériault, G., ... & Fournier, G. (1990). The response to long-term overfeeding in identical twins. New England Journal of Medicine, 322(21), 1477-1482.

Brownell, K. D., Greenwood, M. R. C., Stellar, E., & Shrager, E. E. (1986). The effects of repeated cycles of weight loss and regain in rats. Physiology & Behavior, 38(4), 459-464.

Camps, S. G., Verhoef, S. P., & Westerterp, K. R. (2013). Weight loss, weight maintenance, and adaptive thermogenesis. The American Journal of Clinical Nutrition, 97(5), 990-994.

Danforth Jr, E., Horton, E. S., O'Connell, M., Sims, E. A., Burger, A. G., Ingbar, S. H., ... & Braverman, L. E. (1979). Dietary-induced alterations in thyroid hormone metabolism during overnutrition. Journal of Clinical Investigation, 64(5), 1336-1347.

El Ghoch, M., Calugi, S., & Dalle Grave, R. (2013). Weight and eating concerns in adolescents with anorexia nervosa: Treatment outcome and predictors at 1-year follow-up. Psychiatry Research, 210(3), 402-407.

Fothergill, E., Guo, J., Howard, L., Kerns, J. C., Knuth, N. D., Brychta, R., ... & Hall, K. D. (2016). Persistent metabolic adaptation 6 years after "The Biggest Loser" competition. Obesity, 24(8), 1612-1619.

Garner, D. M., & Garfinkel, P. E. (1997). Handbook of treatment for eating disorders. Guilford Press.

Keesey, R. E., & Hirvonen, M. D. (1997). Body weight set-points: determination and adjustment. Journal of Nutrition, 127(9), 1875S-1883S.

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

Klok, M. D., Jakobsdottir, S., & Drent, M. L. (2007). The role of leptin and ghrelin in the regulation of food intake and body weight in humans: a review. Obesity Reviews, 8(1), 21-34.

Leibel, R. L., Rosenbaum, M., & Hirsch, J. (1995). Changes in energy expenditure resulting from altered body weight. New England Journal of Medicine, 332(10), 621-628.

Mann, T., Tomiyama, A. J., Westling, E., Lew, A. M., Samuels, B., & Chatman, J. (2007). Medicare's search for effective obesity treatments: diets are not the answer. American Psychologist, 62(3), 220-233.

Mehler, P. S., & Brown, C. (2015). Anorexia nervosa–medical complications. Journal of Eating Disorders, 3(1), 11.

Rosenbaum, M., & Leibel, R. L. (2010). Adaptive thermogenesis in humans. International Journal of Obesity, 34(1), S47-S55.

Sumithran, P., Prendergast, L. A., Delbridge, E., Purcell, K., Shulkes, A., Kriketos, A., & Proietto, J. (2011). Long-term persistence of hormonal adaptations to weight loss. New England Journal of Medicine, 365(17), 1597-1604.

Walsh, B. T. (2013). The enigmatic persistence of anorexia nervosa. American Journal of Psychiatry, 170(5), 477-484.

‍