On-again-off-again weight loss journeys are often referred to as “yo-yo” diets or “weight cycling,” and have picked up a reputation for being bad for our health, potentially making future battles with the bulge even more challenging. But a recent review into decades of evidence has found that yo-yo diets are not responsible for greater fat accumulation, faster muscles loss, or a slowed metabolism.
The review, published in The Lancet, aimed to find out if the old adage that yo-yo diets are bad for our health was based in science, or merely a matter of opinion. To set the record straight, two distinguished professors looked at the data from decades of studies, involving both humans and animals, and concluded that there was no causal evidence to show a link between weight cycling and long-term harm in people living with obesity.
“Many people struggling with weight are discouraged from trying to lose weight because they fear ‘yo‑yo dieting’ will lead to muscle loss and somehow damage their metabolism,” commented Professor Faidon Magkos. “Our review indicates that these fears are largely unsupported. In most cases, the benefits of trying to lose weight clearly outweigh the theoretical risks of weight cycling.”
Is Yo-Yo Dieting Bad for Your Health?
The review found no consistent evidence to show that weight cycling causes a disproportionate loss of lean muscle mass or long-term suppression of the metabolism. Instead, most people who regain weight after a yo-yo diet return to a similar starting point, going back to their previous body composition rather than an unhealthier one.
The professors point out that regaining weight does reverse many of the benefits of weight loss, such as improvements in blood sugar, blood pressure, and lipid levels. But this does not imply that a person is worse off than before they lost the weight in the first place. “Regaining weight brings people back toward baseline risk — not beyond it,” Magkos explained. “There’s a crucial difference between losing benefits and causing harm.”
Professor Norbert Stefan added that while yo-yo diets may get the blame, other factors are at play. “Once you properly account for pre‑existing health conditions, aging, and overall exposure to obesity, the supposed harmful effects of weight cycling largely disappear,” he concluded.
When average body weight, over time, is considered, weight cycling does not predict diabetes or cardiovascular disease risk. Higher adiposity itself, not weight fluctuation, appears to be the dominant driver of such risk.
With people now jumping on and off GLP-1 medications, the effects of yo-yo diets are of great interest. “The idea that ‘yo‑yo dieting ruins your metabolism’ is not supported by robust evidence,” is the take home message emphasized by both professors. “Trying—and even failing—to lose weight is not harmful. But giving up altogether may be.”
