Most of us have tried a diet, lost weight, and watched the pounds creep back a few months later.
For decades the warning has been that repeating this pattern wears out your metabolism.
A review published in October 2026 in Nature Reviews Endocrinology complicates that story. The real question, the authors argue, is what you weighed before you started.
Faidon Magkos at the University of Copenhagen and Norbert Stefan at the German Center for Diabetes Research reach a counterintuitive conclusion.
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For people with obesity, repeated weight loss and regain appears to cause little lasting harm beyond the obesity itself.
For adults who were already at a healthy weight, the picture may be more concerning.
Muscle and fat
When a person with obesity loses weight, most of what drops is body fat.
When a person at a normal weight loses the same amount, a larger share tends to come from muscle and other lean tissue.
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That matters for what happens next. Muscle burns calories at rest, so losing it lowers the body's energy needs.
When the weight returns, a bigger slice tends to come back as fat.
Over several cycles, the authors argue, a genetically susceptible lean adult may slowly drift toward obesity.
They stress that this remains a hypothesis still waiting for direct comparison trials.
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A warning aimed at the drug era
Many lean adults already diet anyway.
"Remarkably, nearly 30% of people who are neither overweight nor obese want to lose weight and have already tried to do so in the past," Magkos said. His comment came in a statement from the German Center for Diabetes Research.
The review lands as prescription weight-loss drugs reach more adults than ever.
The authors point to off-label use by people who are not medically overweight but still want to shed a few pounds.
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That matters because stopping and restarting these drugs produces its own cycles of loss and regain.
For someone with obesity, the review sees little reason to fear those swings.
For a healthy-weight adult using the drugs off-label, the same pattern may nudge body composition in the wrong direction over time.
The authors recommend that physicians weigh both the goal and a patient's starting weight before counseling someone on another attempt at weight loss.
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This article is made and published by Ida-Marie Palm Varbæk, who may have used AI in the preparation.