How Much Weight Can You Lose on GLP-1 Medications? What the Trials Show
The "up to 20%+" headlines are real trial averages, not marketing exaggeration — but they're averages, not guarantees. Here's exactly what STEP-1 and SURMOUNT-1 found, how individual results actually vary, and what happens if you stop.
Publication date: 2026-08-04Last updated: 2026-08-04Reading time: 10 minAuthor: The Iron Verdict Research Team
What You'll Learn
SemaglutideThe exact STEP-1 result, with citation.
TirzepatideThe exact SURMOUNT-1 result, with citation.
Why Results VaryWhat actually predicts a stronger or weaker response.
The TimelineWhen weight loss starts and when it plateaus.
After StoppingWhat the regain data actually shows.
Realistic ExpectationsHow to read these numbers for yourself, not the trial average.
Short answer: In pivotal trials, average weight loss was 14.9% of body weight on semaglutide (STEP-1, 68 weeks) and 16.0–22.5% on tirzepatide depending on dose (SURMOUNT-1, 72 weeks) — both far above placebo, but with a wide range of individual results around those averages.
Semaglutide Results (STEP-1)
14.9% average weight loss at 68 weeksRCT, n=1,961
Wilding JPH, et al. (STEP-1) — New England Journal of Medicine, 2021
Adults with overweight or obesity, without diabetes, randomized 2:1 to semaglutide 2.4mg or placebo, both with lifestyle intervention. Semaglutide produced a 12.4 percentage-point (roughly 28 lb) greater average reduction in body weight than placebo at 68 weeks. 86% of semaglutide participants lost at least 5% of body weight.
DOI: 10.1056/NEJMoa2032183 ↗
Tirzepatide Results (SURMOUNT-1)
16.0–22.5% average weight loss at 72 weeksRCT, n=2,539
Jastreboff AM, et al. (SURMOUNT-1) — New England Journal of Medicine, 2022
Adults with obesity or overweight randomized to tirzepatide 5mg, 10mg, 15mg, or placebo. Results scaled with dose: the 15mg group averaged 22.5% weight loss, with about 9 in 10 participants losing weight on tirzepatide overall.
PMID: 35658024 ↗
The gap between the two drugs' averages is consistent with tirzepatide's dual GIP/GLP-1 mechanism — see our guide to what GLP-1 medications are for how that mechanism differs from single-receptor semaglutide.
Why Individual Results Vary
A trial average describes the middle of a distribution, not a guarantee for any one person. Response magnitude in these trials varied with dose actually reached (not everyone tolerates or reaches the top dose), adherence over many months, and individual metabolic and physiological factors that aren't fully predictable in advance. A meaningful minority of participants in every pivotal trial lost substantially less than the average — that's normal variance, not a sign anything went wrong. How large a minority is worth knowing: 13.6% of the semaglutide group in STEP-1 never reached 5% loss, and half never reached 15%. If your own result is below the headline figures, that page has the full distribution and what is worth checking.
How those trial numbers were produced
HealthRX — physician-supervised GLP-1 care
Every figure above comes from a supervised programme with a titration schedule and a clinician adjusting it. The drug alone did not produce those results — the supervision was part of the protocol.
See what the intake involves →
United States only. Prescription treatment: you complete a medical intake reviewed by a licensed provider, who decides whether anything is appropriate for you.
Disclosure: we earn a commission if you start a plan through this link, at no extra cost to you. It does not change what this page says. HealthRX dispenses compounded semaglutide and tirzepatide, which are pharmacy-prepared formulations, not the FDA-approved branded products. Nothing on this page is medical advice — that is what the provider review is for.
The Weight-Loss Timeline
| Phase | What trial data shows |
|---|
| Early weeks (dose titration) | Weight loss begins, typically gradually, as the dose is increased in steps |
| Mid-trial (once at target dose) | Weight loss accelerates and continues over months |
| Later trial period (~52–72 weeks) | Rate of loss slows as the body approaches a new equilibrium — the plateau |
A plateau isn't treatment failure — it's the expected physiology of any intervention that changes energy balance. See our note on managing GI side effects during the titration phase specifically, since that's when GI symptoms are typically most noticeable too.
What Happens After You Stop
~50–60% of lost weight regained within a year of stoppingMeta-regression, 2026
Systematic review and nonlinear meta-regression — PMID 41938838
Pooling trials and observational studies on GLP-1 receptor agonist discontinuation, this analysis found substantial weight regain after stopping — greater in absolute terms for semaglutide/tirzepatide than for liraglutide, consistent with their larger initial effect sizes.
PMID: 41938838 ↗
Weight and cardiometabolic reversal after semaglutide withdrawalRCT extension follow-up
Wilding JPH, et al. (STEP-1 extension) — Diabetes, Obesity and Metabolism, 2022
A follow-up of the original STEP-1 trial population after stopping semaglutide, documenting the trajectory of weight regain and reversal of cardiometabolic improvements that had accrued during treatment.
Full study on PMC ↗
Bottom line: Current clinical guidelines treat obesity as a chronic, relapsing condition — regain after stopping is framed as disease recurrence, the same way blood pressure rises again after stopping antihypertensive medication, not as a personal failure.
Setting Realistic Expectations
- Use the range, not just the average. Trial averages describe the middle of a wide distribution.
- Expect gradual, not linear, progress — titration, acceleration, and plateau are all normal phases.
- Plan for muscle preservation from day one. See our full guide to GLP-1 and muscle loss for the two interventions proven to help.
- Think about maintenance before you need it. The regain data above makes clear that what happens after reaching a goal weight matters as much as getting there.
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Everything on this page, and the other 33 articles, in one 151-page book — plus a 30-day protocol, four weeks of meal plans and the tracker pages, none of which are on the site.
19 peer-reviewed references, cited by PMID and DOI. Where two studies disagree, both are shown.
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Where treatment actually starts
The trial averages are on this page. What they cannot tell you is what a provider would say about your own case.
Hims is a US telehealth service that connects you with licensed providers for an online consultation. If a provider prescribes treatment, it is fulfilled through FDA-regulated pharmacies. Whether anything is prescribed is their decision, not ours and not yours.
The Iron Verdict earns a commission if you subscribe. It changes nothing on this page. The trade-offs, the side effects and the numbers that do not flatter the drugs are all still here, and they stay here.
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Available in the United States only. This is not medical advice, and nothing here is a recommendation to take any medication.
FAQ
How much weight can you realistically lose on semaglutide?
In the STEP-1 trial, average weight loss was 14.9% of body weight over 68 weeks versus placebo, with 86% of participants losing at least 5% of body weight.
How much weight can you lose on tirzepatide?
In the SURMOUNT-1 trial, average weight loss ranged from 16.0% to 22.5% of body weight depending on dose, over 72 weeks.
What happens to your weight if you stop taking a GLP-1 medication?
Systematic-review data shows substantial regain is common, with pooled analyses finding roughly 50 to 60 percent of lost weight regained within a year of stopping semaglutide or tirzepatide.
Does everyone lose the same amount of weight on GLP-1 medications?
No. Trial results are averages; individual response varies widely based on dose reached, adherence, and individual physiology.
Is weight regain after stopping GLP-1 medication a personal failure?
No. Current clinical guidelines frame obesity as a chronic, relapsing condition, so regain after stopping treatment is treated as disease recurrence, not a failure of willpower.
Scientific References
- Wilding JPH, et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP-1). New England Journal of Medicine, 2021. DOI: 10.1056/NEJMoa2032183.
- Jastreboff AM, et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). New England Journal of Medicine, 2022. PubMed PMID: 35658024.
- Wilding JPH, et al. Weight regain and cardiometabolic effects after withdrawal of semaglutide: The STEP 1 trial extension. Diabetes, Obesity and Metabolism, 2022. Full text on PMC.
- Trajectory of weight regain after cessation of GLP-1 receptor agonists: a systematic review and nonlinear meta-regression, 2026. PubMed PMID: 41938838.
Medical Disclaimer
This article is educational and not medical advice, and does not recommend, endorse, or provide dosing guidance for any prescription medication. Individual results vary. Talk to a qualified clinician about what to expect from any treatment, and before starting, stopping, or changing any medication.