A direct comparison matters
Which worked better in a direct trial? That's a more useful starting point than placing two percentages from unrelated studies side by side. SURMOUNT-5 compared tirzepatide and semaglutide within one study in adults with obesity who did not have type 2 diabetes. The shared design makes the comparison informative. The specific population also tells us where to be careful about applying it. The study publication is the reference for the numbers below.
What SURMOUNT-5 reported
The open-label trial randomized 751 participants and followed treatment for 72 weeks. The reported mean weight change was −20.2% with tirzepatide and −13.7% with semaglutide. The study compared maximum tolerated tirzepatide doses of 10 or 15 mg with semaglutide doses of 1.7 or 2.4 mg; these are trial details, not personal dosing instructions. Gastrointestinal events were the most common adverse events in both groups. Lilly funded the study. The original publication provides the design and results.
An average is not a forecast
A group average describes the study population under the study’s conditions. It does not predict an individual reader’s outcome. Nor does a larger average reduction settle every treatment decision. A clinician may also consider the reason for treatment, other conditions, tolerability, contraindications, preferences and access. The comparison addresses an important research question; it does not replace that broader conversation.
Read the limits as carefully as the headline
Open-label means the treatments were not concealed from participants and investigators in the same way as a blinded trial. The study also tested particular doses over a particular period. It should not be presented as a comparison of every formulation or dose available now or in the future. Similarly, results in people without diabetes should not simply be substituted for evidence in people with diabetes. Always check which patient group a comparison is about before applying its conclusion.
The gap is 6.5 percentage points
The reported averages, 20.2% and 13.7%, differ by 6.5 percentage points. Calling that “6.5% more weight loss” blurs the distinction between a percentage-point difference and a relative percentage difference. More importantly, neither number is a personal forecast. They summarize groups in this trial. Keep the arithmetic attached to that setting rather than turning it into a promise about what an individual reader would lose. See the trial results.
Product identity is part of the evidence
Semaglutide and tirzepatide are ingredients in approved medicines, but that does not mean every product offered under those ingredient names is FDA approved. FDA consumer information describes concerns involving unapproved and compounded versions. Evidence about a trial product does not establish the quality of an independently marketed preparation. Read the FDA’s explanation. If your main interest is a newer investigational compound, our retatrutide explainer covers why regulatory status and trial results should be tracked separately. Comparisons are most useful when they preserve these distinctions rather than reduce treatment to a ranking.
Sources & further reading
Research context last reviewed September 21, 2026. Wording, presentation and catalog links updated September 27, 2026. This article is AI-assisted and has not been reviewed by a clinician. It is educational and does not replace individual medical advice. Read our editorial approach.
