Repeated weight loss followed by weight gain, often referred to as “yo-yo dieting” or weight cycling, has long been thought to be unhealthy and potentially even worse than remaining overweight. However, an important new review has been published. Lancet Diabetes and Endocrinology We argue that this belief is not supported by strong scientific evidence.
In an invited article for Personal View, Professor Phaidon Magkos of the University of Copenhagen and Professor Norbert Stefan of the German Diabetes Research Center (DZD), Tübingen University Hospital, Munich Helmholtz Professor reviewed decades of research in both humans and animals. After reviewing the evidence, we found no convincing evidence that weight cycling itself causes long-term harm to obese people.
“Many people struggling with weight are deterred from trying to lose weight for fear that ‘yo-yo dieting’ will lead to muscle loss and impair metabolism in some way,” Professor Magkos says. “Our research shows that these concerns are largely unfounded. In most cases, the benefits of trying to lose weight clearly outweigh the theoretical risks of weight cycling.”
Long-standing concerns about yo-yo dieting
For years, weight cycling has been associated with a wide range of health concerns, including increased fat storage, accelerated muscle loss, decreased metabolism, and increased risk of diabetes and cardiovascular disease. These concerns have influenced public opinion and even medical advice, with some believing that repeated diet attempts may ultimately do more harm than good.
A new analysis challenges that idea.
What researchers discovered
Researchers reviewed observational studies, randomized clinical trials, and animal studies that focused on repeated weight loss and weight regain. They looked at how weight cycling affects body weight, body composition, metabolism, and blood sugar control.
“Proper consideration of pre-existing health conditions, aging and overall exposure to obesity largely eliminates the expected deleterious effects of weight cycling,” explains Professor Stephan.
This review found no consistent evidence that weight cycling leads to excessive loss of lean (muscle) mass or causes permanent metabolic decline. In many cases, people who regain weight end up with a body composition similar to their original state, rather than being worse off. The researchers also found no strong evidence that weight cycling was responsible for the slow, long-term weight gain that is common in obesity.
Weight regain and real harm
The authors highlight important differences. When you gain weight back, many of the positive effects of weight loss are reversed, such as improved blood sugar, blood pressure, and cholesterol levels. But losing these benefits doesn’t necessarily mean you’re any worse off than you were before you lost weight.
“When you gain weight back, people return to their risk baseline, but not beyond it,” Magkos says. “There is a crucial difference between loss of profit and harm.”
Several large studies have shown that when researchers calculate a person’s average weight over time, weight fluctuation itself is no longer associated with an increased risk of diabetes or cardiovascular disease. Rather, excess body fat is thought to be the main factor causing metabolic risk.
Obesity drugs and their impact on treatment
The study results come at a time when new obesity treatments, such as GLP-1 and dual incretin agonists, are becoming increasingly popular. Although these drugs can cause significant weight loss, many patients regain weight when treatment is discontinued, forming a pattern similar to weight cycling.
According to the researchers, this recovery should not automatically be considered harmful. Even temporary weight loss can provide important health benefits and improve quality of life, even if the weight loss is not permanent.
A reassuring message to patients
Magkos and Stefan argue that this evidence should encourage people who are overweight or obese not to abandon their weight loss efforts just because weight loss is difficult to maintain.
“The idea that ‘yo-yo dieting messes with your metabolism’ is not supported by solid evidence,” they say. “Trying to lose weight and even failing is not harmful. But giving up completely may be.”
