Many people experience weight fluctuations throughout their lives, and so-called yo-yo dieting has long been considered a health risk. In some cases, it is even more harmful than remaining overweight.
For example, it is associated with negative health effects such as increased fat mass, decreased muscle mass, decreased metabolic rate, and increased risk of diseases such as type 2 diabetes and cardiovascular disease.
But a careful evaluation of the research does not provide strong evidence that these negative effects are due to yo-yo dieting per se, or that yo-yo dieting is more harmful than persistent overweight, said Phaidon Magkos, a professor at the University of Copenhagen’s School of Nutrition, Exercise and Sport, who together with his German colleagues conducted a comprehensive analysis of the available research.
Many people refrain from trying to lose weight because they are worried that gaining it back afterwards will have a negative effect on their body and metabolism. Our research shows that these concerns are largely unfounded. In most cases, the benefits of weight loss outweigh the potential risks of subsequent weight gain. ”
Professor Phaidon Magkos, Department of Nutrition, Exercise and Sport, University of Copenhagen
What you can learn from analysis
In their analysis, researchers reviewed a wide range of selected studies examining the effects of repeated weight loss and weight regain on body weight, body composition, metabolism, and more, including observational studies, clinical trials, and animal studies.
An important finding is that the association between yo-yo dieting and poor health is often not supported as a causal relationship. Many studies are based on self-reported weight, making it difficult to determine cause and effect. Additionally, it is often unclear whether weight loss is a deliberate attempt or due to an underlying medical condition.
“If we take into account the overall exposure to pre-existing diseases, aging and obesity, the supposed deleterious effects of yo-yo dieting are largely eliminated,” explains Professor Norbert Stephan from the German Diabetes Research Center (DZD), University Hospital Tübingen and Helmholtz University Hospital München.
Gaining weight back is not the same as doing harm
For people whose weight fluctuates, researchers emphasize that many of the health benefits of weight loss are lost when weight is regained.
However, this does not mean that the individual is worse off than before the weight loss, says Phaidon Magkos.
“When you gain weight back, you return to a similar level of risk as before, but not above it. There is a critical difference between losing benefit and causing harm.”
According to the researchers, several large studies have shown that the degree of obesity itself, rather than weight fluctuations, appears to be the main factor in metabolic disease risk.
Impact on weight loss and treatment
Weight loss drugs have become increasingly popular in recent years, and such treatments can lead to significant weight loss, which is often followed by significant weight regain when the drug is discontinued.
According to the authors, this pattern should not necessarily be interpreted as harmful. Conversely, intermittent weight loss can provide meaningful periods of improved metabolic health and quality of life, even if it cannot be maintained permanently.
Researchers also highlight that most people who ultimately achieve long-term weight loss experience multiple failures along the way. Therefore, weight loss and subsequent weight regain is often not a sign of failure or health risk, but a necessary step on the road to success.
As such, both researchers emphasize important messages for patients and clinicians.
“Overweight people should not be deterred from trying to lose weight even if they find it difficult to maintain in the long term. Failed attempts at weight loss are not harmful, but giving up completely may be,” they say.
What you can learn from analysis
Researchers dispute the interpretation that yo-yo dieting itself is harmful.
They found no strong evidence that repeated weight loss and weight gain leads to lasting health damage.
They point out that these concerns shape both public communication and clinical advice, contributing to the widespread recognition that repeated weight loss attempts can do more harm than good.
Our analysis shows that the association between yo-yo dieting and disease is often not causal and may reflect other underlying factors.
Worrying about gaining weight back after losing weight should not prevent you from trying to lose weight.
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Reference magazines:
Magkos, F., Stefan, N. (2026). Is weight cycling clinically harmful? Lancet Diabetes and Endocrinology. DOI: 10.1016/S2213-8587(26)00037-9. https://www.thelancet.com/journals/landia/article/PIIS2213-8587(26)00037-9/abstract
