Professor Faidon Magkos of the University of Copenhagen has a straightforward message for the millions of people who have abandoned weight loss efforts: fear of yo-yo dieting is likely holding you back from trying something that could genuinely improve your health.
A major review published in The Lancet Diabetes & Endocrinology challenges decades of received wisdom about weight cycling—the pattern of losing weight and regaining it. For years, people have been warned that repeated dieting attempts might actually damage their metabolism, cause lasting muscle loss, and increase their risk of diabetes and heart disease. These fears have been so widespread that many people struggling with their weight have decided the risks of trying simply aren't worth it. But Magkos and his colleague Professor Norbert Stefan of the German Center for Diabetes Research (DZD), University Hospital Tübingen, and Helmholtz Munich, spent months examining the accumulated evidence and found something surprising: there is no convincing proof that weight cycling itself causes long-term harm.
The researchers reviewed decades of studies involving both humans and animals—observational studies, randomized clinical trials, and animal research focused on how repeated weight loss and regain affects body weight, body composition, metabolism, and blood sugar control. What they discovered fundamentally reframes the conversation. "Once you properly account for pre-existing health conditions, aging, and overall exposure to obesity, the supposed harmful effects of weight cycling largely disappear," Stefan explains. The review found no consistent evidence that cycling leads to excessive muscle loss or causes lasting metabolic slowdown. In many cases, people who regained weight returned to a body composition similar to where they started—not worse off than before.
The distinction between regaining weight and causing actual harm is crucial. When people regain weight, they do lose many of the positive effects of their initial weight loss: improvements in blood sugar, blood pressure, and cholesterol levels. But this difference matters enormously. "Regaining weight brings people back toward baseline risk—not beyond it," Magkos says. Several large studies showed that when researchers account for a person's average body weight over time, weight cycling itself is no longer linked to higher risks of diabetes or cardiovascular disease. Instead, excess body fat emerges as the main factor driving metabolic risk.
The timing of this research is significant. New obesity medications, including GLP-1 and dual incretin agonists, are becoming increasingly common and can produce significant weight loss. But many patients regain weight after stopping treatment—a pattern that mirrors weight cycling. According to the researchers, this regain should not be viewed as harmful in itself. Even temporary periods of weight reduction provide important health benefits and can improve quality of life, even if the weight loss is not permanent.
For people genuinely stuck between the desire to lose weight and the fear that trying and failing might make things worse, the evidence offers reassurance. "The idea that 'yo-yo dieting ruins your metabolism' is not supported by robust evidence," Magkos and Stefan write. "Trying—and even failing—to lose weight is not harmful. But giving up altogether may be."