Evidence explainerWomen's GLP-1 & Weight
Semaglutide vs Tirzepatide: How Much Weight the Trials Showed, and What Happens When You Stop
The headline numbers come from 68- to 72-week trials with diet and activity support. The less-quoted number is what happened when people stopped.
Key takeaways
- STEP 1: semaglutide 2.4 mg weekly, 14.9% average loss at 68 weeks vs 2.4% on placebo (15.3 kg vs 2.6 kg) [1].
- SURMOUNT-1: tirzepatide 5, 10 and 15 mg, 15.0%, 19.5% and 20.9% average loss at 72 weeks vs 3.1% on placebo [2].
- STEP 4: after 20 weeks on semaglutide, switching to placebo led to 6.9% regain by week 68, while continuing led to a further 7.9% loss [3].
- Gastrointestinal side effects caused 4.5% of STEP 1 participants on semaglutide to stop, vs 0.8% on placebo [1].
Semaglutide (Wegovy): STEP 1
STEP 1 randomized adults with overweight or obesity to semaglutide 2.4 mg weekly or placebo for 68 weeks, both with lifestyle counseling [1]. Average weight change was -14.9% vs -2.4%, and 86.4% vs 31.5% lost at least 5% [1].
Half of the semaglutide group (50.5%) lost 15% or more, vs 4.9% on placebo [1]. Nausea and diarrhea were the most common side effects, typically transient and mild to moderate [1].
Tirzepatide (Zepbound): SURMOUNT-1
SURMOUNT-1 randomized adults with obesity, or overweight with a weight-related condition, to tirzepatide 5, 10 or 15 mg weekly or placebo for 72 weeks [2]. Mean baseline weight was 104.8 kg [2].
Average weight change was -15.0%, -19.5% and -20.9% across the three doses vs -3.1% on placebo, and 50% (10 mg) and 57% (15 mg) lost 20% or more [2]. Side effects were mostly gastrointestinal and occurred mainly during dose escalation; 4.3% to 7.1% stopped because of adverse events vs 2.6% on placebo [2].
What happens when you stop
STEP 4 put 803 adults (79% women) on semaglutide for 20 weeks, where they lost an average of 10.6%, then randomized them to keep going or switch to placebo [3]. From week 20 to 68, the continued group lost another 7.9% while the placebo group regained 6.9% [3].
If cost is what would make you stop, compare the published prices and insurance routes before you start.
Caveats
These were trials of the brand-name drugs at labeled doses, with structured follow-up. They do not tell you how compounded versions perform; the FDA does not review compounded drugs for safety, effectiveness or quality [4].
Partners we link to
- FoundPaid linkWeight care with named board-certified clinicians: brand-name GLP-1 prescriptions (medication billed separately, insurance accepted) or compounded semaglutide and tirzepatide, which are not FDA-approved. LegitScript certified.See Found's weight plans
- GalaPaid linkWomen-focused online weight care: compounded semaglutide or tirzepatide (not FDA-approved) at a published flat $179/mo on a yearly subscription, visits and shipping included (checked Oct 8, 2026). LegitScript certified.See Gala's GLP-1 plans
Quick answers
Is tirzepatide stronger than semaglutide?
In separate placebo-controlled trials, tirzepatide 10 to 15 mg produced larger average losses (19.5% to 20.9%) than semaglutide 2.4 mg (14.9%), but those trials were not head-to-head comparisons [1][2].
Will I regain the weight if I stop?
In STEP 4, people switched to placebo regained 6.9% of their body weight over 48 weeks [3].
More in Women's GLP-1 & Weight
References
- [1]Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP 1). N Engl J Med, 2021.
- [2]Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). N Engl J Med, 2022.
- [3]Effect of Continued Weekly Subcutaneous Semaglutide vs Placebo on Weight Loss Maintenance in Adults With Overweight or Obesity: The STEP 4 Randomized Clinical Trial. JAMA, 2021.
- [4]FDA's Concerns with Unapproved GLP-1 Drugs Used for Weight Loss (content current as of 10/01/2026). U.S. Food and Drug Administration, 2026.