The short answer
Tirzepatide produced greater average weight loss in SURMOUNT-5, a trial that compared the two medicines directly. That is more informative than placing results from unrelated studies side by side.
What was tested?
Researchers randomly assigned 751 adults with obesity, without type 2 diabetes, to weekly tirzepatide or semaglutide for 72 weeks. Participants knew which treatment they received. The study used maximum tolerated doses: tirzepatide 10 or 15 mg, and semaglutide 1.7 or 2.4 mg.
Average weight change was −20.2% with tirzepatide and −13.7% with semaglutide. Average waist reduction was 18.4 cm versus 13.0 cm.
Percent of starting weight
Original chart based on the study. Values are reported group averages.
| Group or measure | Average result |
|---|---|
| Tirzepatide | −20.2% |
| Semaglutide | −13.7% |
What does that mean for readers?
The result favors tirzepatide for these weight and waist outcomes in this population. It does not identify the best medicine for every individual or compare every available regimen.
Digestive side effects were the most common in both groups, generally mild or moderate and concentrated during dose increases.
Sources
SURMOUNT-5, NEJM, 2025. Funded by Eli Lilly. Study abstract · Paper.