When it comes to losing weight, the fear of “ruining your metabolism” is widespread. Indeed, many people who have lost weight and then put it back on feel that every failed attempt leaves them worse off than before, with more fat, less muscle, greater hunger, lower energy, and an ever-diminishing ability to lose weight again.

For those looking to lose weight, the so-called “yo-yo effect” has become an almost constant threat. According to this view, losing and regaining weight is not only frustrating but also dangerous. It even leads some people to believe that they are better off not trying to lose weight at all.

However, a critical review published in The Lancet Diabetes & Endocrinology calls for a reevaluation of this idea. The authors review the available evidence on “weight cycling” – repeated cycles of weight loss and regain – and conclude that there is no solid evidence that this phenomenon, in itself, causes long-term clinical harm in people with obesity.

Nuance is important here. This does not mean that regaining weight is desirable, nor that every diet is a good idea. It highlights something more specific: current evidence does not support the claim that losing weight and then regaining it “breaks” the metabolism or necessarily leaves a person worse off than before.

This finding is important because the fear of the yo-yo effect can become a barrier to seeking help, making changes, or resuming healthy habits after regaining weight. And given that obesity is a chronic and recurrent condition, suggesting that every failed attempt causes irreversible damage can lead to feelings of guilt, despair and resignation.

Read more: How does your body lose weight? An obesity doctor explains why one size doesn’t fit all in weight loss

What we know – and don’t know – about weight cycling

Part of the confusion stems from the way many observational studies have been interpreted. People who have been through multiple cycles of weight loss and regain tend to have........

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