Stopping a GLP-1-based obesity drug often leads to weight regain, but that does not mean the treatment failed. In the STEP 1 extension, adults who stopped semaglutide 2.4 mg after 68 weeks regained about two-thirds of the weight they had lost over the following year. A randomized withdrawal trial of tirzepatide showed the same direction of effect: people switched to placebo regained substantial weight, while those who continued treatment lost more.
Semaglutide withdrawal was followed by substantial weight regain in STEP 1
STEP 1 randomized 1,961 adults with obesity or overweight plus a weight-related condition, but without diabetes, to semaglutide 2.4 mg or placebo for 68 weeks alongside lifestyle intervention. A 327-person off-treatment extension then followed a subset for another year after both the study drug and structured lifestyle intervention were stopped.
During treatment, participants assigned semaglutide lost an average of 17.3% of body weight. By week 120, one year after treatment ended, they had regained 11.6 percentage points, leaving an average net loss of 5.6% from baseline. The investigators described this as regaining roughly two-thirds of the prior weight loss.
Many cardiometabolic improvements also moved back toward baseline after withdrawal.
Tirzepatide withdrawal produced the same broad pattern in a randomized trial
SURMOUNT-4 used a randomized withdrawal design. A total of 783 adults without diabetes first received tirzepatide for 36 weeks. The 670 participants who completed that lead-in were then randomized to continue tirzepatide or switch to placebo for another 52 weeks.
By week 36, participants had lost a mean 20.9% of their starting weight. From week 36 to week 88, those who continued tirzepatide lost an additional 5.5%, whereas those switched to placebo gained 14.0%. At week 88, 89.5% of participants who continued tirzepatide maintained at least 80% of the weight they had lost during the lead-in, compared with 16.6% after switching to placebo.
The authors concluded that withdrawing tirzepatide led to “substantial regain of lost weight,” whereas continued treatment maintained and augmented the initial reduction.
Why weight comes back when treatment stops
GLP-1 receptor agonists such as semaglutide reduce appetite, alter satiety signaling, and slow gastric emptying. Tirzepatide activates both GIP and GLP-1 receptors. These effects are pharmacologic: they are strongest while the drug is present and receptor signaling remains altered.
Our GLP-1 drugs explainer covers how these pathways influence appetite and glucose regulation, while our tirzepatide mechanism article explains the dual GIP/GLP-1 pharmacology.
When treatment stops, those effects diminish. Appetite can rise again, satiety can weaken, and the biologic pressures that defend body weight can reassert themselves.
Regain is variable and not everyone returns to baseline
The trial averages do not mean every person regains the same amount. In STEP 1, participants still had an average net weight loss of 5.6% from baseline one year after stopping semaglutide. Some regained more, some less, and some maintained a larger fraction of their loss.
Randomized withdrawal trials also select people who have already tolerated and responded to treatment before withdrawal, so they do not predict an exact outcome for every patient in routine practice.
The evidence does not show that stopping permanently slows metabolism
A common interpretation is that GLP-1 drugs somehow “break” metabolism so that weight returns faster afterward. The withdrawal trials do not establish that. They show that the therapeutic effects are not permanent after the medication is removed.
Weight regain after intentional weight loss also occurs after diet-based interventions because energy expenditure, hunger signals, and food reward can adapt to defend a lower body weight. Current evidence does not support the idea that withdrawal causes a unique permanent metabolic injury.
Stopping because of side effects is different from stopping after reaching a goal weight
Some people discontinue because of nausea, vomiting, diarrhea, constipation, gallbladder disease, cost, pregnancy planning, surgery, access problems, or personal preference. Our GLP-1 side-effects guide reviews the common and serious adverse effects that can influence treatment.
There is no single evidence-based tapering schedule proven to prevent regain after stopping semaglutide or tirzepatide for obesity.
What the evidence cannot yet answer
STEP 1’s extension was exploratory and included only a subset of the original randomized population. It also stopped the structured lifestyle intervention at the same time as semaglutide, so the study cannot isolate the effect of drug withdrawal from withdrawal of study-supported lifestyle treatment.
SURMOUNT-4 was funded by Eli Lilly, and STEP 1 was funded by Novo Nordisk. Both programs included company-affiliated investigators. Long-term independent studies are still needed to define optimal maintenance strategies and what happens after many years of use.
For obesity, maintenance appears to be part of treatment rather than an afterthought
The clearest conclusion from current withdrawal studies is that weight-loss medications behave more like chronic therapies than short courses. Stopping can be appropriate, but patients should expect that appetite and weight may move back toward pretreatment levels and should plan follow-up accordingly.
References
- Wilding JPH, Batterham RL, Davies M, et al. Weight regain and cardiometabolic effects after withdrawal of semaglutide: The STEP 1 trial extension. Diabetes Obes Metab. 2022;24:1553-1564. DOI: 10.1111/dom.14725.
- Aronne LJ, Sattar N, Horn DB, et al. Continued Treatment With Tirzepatide for Maintenance of Weight Reduction in Adults With Obesity: The SURMOUNT-4 Randomized Clinical Trial. JAMA. 2024;331:38-48. DOI: 10.1001/jama.2023.24945.