Research brief · 2026-09-09
Why Does Weight Come Back After Stopping Semaglutide?
Semaglutide is a prescription medication approved for type 2 diabetes and for chronic weight management. It works by acting on GLP-1 receptors, lowering appetite and slowing how quickly the stomach empties, for as long as the drug is present in the body. A natural question is what happens when it is no longer present. Two well-designed trials have looked at exactly that.
The first is the STEP 1 trial extension, published by Wilding and colleagues in Diabetes, Obesity and Metabolism in 2022. STEP 1 itself had randomised 1,961 adults with obesity to weekly semaglutide or placebo for 68 weeks, with average weight change of minus 14.9 percent versus minus 2.4 percent. A subset of 327 participants who completed the trial were then followed for a further year with all treatment stopped. That group had lost 17.3 percent on average during treatment. One year off treatment, they had regained 11.6 percentage points of it, leaving a net loss of 5.6 percent. Roughly two-thirds of the lost weight had returned, and improvements in blood pressure and lipids moved back toward their starting values alongside it.
The second trial, SURMOUNT-4, tested the related drug tirzepatide and was built specifically for this question. Published by Aronne and colleagues in JAMA in 2024, it gave all 783 participants tirzepatide openly for 36 weeks, during which they lost 20.9 percent on average. Then 670 of them were randomised to either continue the drug or switch to placebo, without knowing which. Over the following 52 weeks, the group that continued lost a further 5.5 percent. The group switched to placebo regained 14.0 percent. Nearly nine in ten people who stayed on treatment held onto at least 80 percent of their loss, compared with about one in six of those switched to placebo.
The trial authors interpret this the same way in both papers: obesity behaves like a chronic condition. The drugs reduce appetite while they are present but do not appear to reset the underlying biology, so when the drug clears, appetite signalling and weight tend to return. The STEP 1 extension authors concluded that ongoing treatment is needed to maintain the improvements.
The limits are real. Both trials stopped treatment abruptly, so nothing is known from randomised data about tapering or lower maintenance doses. The averages hide wide individual variation, and no one has established what separates people who regain little from those who regain a lot. Follow-up ran about a year, not longer. Decisions about starting, continuing or stopping these medications belong with a physician.
Sources
- Wilding JPH, et al. Weight regain and cardiometabolic effects after withdrawal of semaglutide: The STEP 1 trial extension
- Diabetes, Obesity & Metabolism 2022
- Aronne LJ, et al. Continued Treatment With Tirzepatide for Maintenance of Weight Reduction in Adults With Obesity: The SURMOUNT-4 Randomized Clinical Trial
- JAMA 2024
- Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1)
- New England Journal of Medicine 2021
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