Why Diets Don’t Work?

Did you know that up to 80% of people who lose weight may eventually regain it, and that many regain even more than they lost? This isn’t just a matter of willpower – there are many physiological and behavioral factors at play. A meta-analysis of 29 studies found that weight loss led to a significant reduction in resting metabolic rate, which can make it harder to maintain weight loss over time (1). Additionally, weight loss can cause changes in hormones that regulate hunger and satiety, making it more difficult to control food intake. A meta-analysis of 24 studies found that weight loss led to significant reductions in the hormone leptin, which signals fullness, and increases in the hormone ghrelin, which signals hunger (2).

Finally, there are many environmental and social factors that can make it difficult to stick to healthy habits, such as stress, lack of sleep, and exposure to unhealthy foods and environments. A meta-analysis of 58 studies found that stress was associated with increased food intake and poorer diet quality, while another meta-analysis of 20 studies found that short sleep duration was associated with higher body weight and increased risk of obesity (3, 4).

But there is hope! Research suggests that sustained weight loss and maintenance is possible with a long-term commitment to healthy habits. A meta-analysis of 80 studies found that higher levels of physical activity and a balanced diet were associated with successful weight loss and maintenance (5). It’s also important to work with a healthcare provider or registered dietitian to develop a personalized plan that works for you. 

Don’t give up – with the right support and strategies, you can achieve and maintain a healthy weight for life. 


Rosenbaum M, et al. Changes in energy expenditure resulting from altered body weight. N Engl J Med. 2018; 378(4): 372-381.

Erdmann J, et al. Physiology and pathophysiology of leptin. Horm Metab Res. 1997; 29(12): 613-619.

Kiecolt-Glaser JK, et al. Stress, food, and inflammation: psychoneuroimmunology and nutrition at the cutting edge. Psychosom Med. 2010; 72(4): 365-369.

Cappuccio FP, et al. Sleep duration and all-cause mortality: a systematic review and meta-analysis of prospective studies. Sleep. 2010; 33(5): 585-592.

Johns DJ, et al. Diet or exercise interventions vs combined behavioral weight management programs: a systematic review and meta-analysis of direct comparisons. J Acad Nutr Diet. 2014; 114(10): 1557-1568.