The question the trial actually tested
When two medicines are studied separately, comparing their headline percentages can be misleading. The groups may differ, the follow-up may differ, and the statistical methods may answer different questions. A head-to-head randomized study puts both treatments inside the same research framework. That makes SURMOUNT-5 a particularly useful starting point for understanding the comparison, without turning it into a recommendation for every reader.
SURMOUNT-5 randomized 751 adults with obesity and without type 2 diabetes. In this open-label trial, participants received weekly injections of maximum tolerated tirzepatide, 10 or 15 mg, or semaglutide, 1.7 or 2.4 mg, for 72 weeks. Eli Lilly funded the study.[1]
What the weight results mean
Mean weight reduction was 20.2% with tirzepatide and 13.7% with semaglutide. These are group estimates, not promised individual outcomes. The arithmetic difference is 6.5 percentage points; calling it a 6.5% difference would obscure the denominator.
Both bars start at zero on the same 0–25% scale. SURMOUNT-5 group averages; lower body weight relative to baseline.
For illustration only, a 6.5 percentage-point difference applied to a 200-pound starting weight equals 13 pounds. That arithmetic helps explain the scale of the study result; it does not predict what a person starting at 200 pounds will lose. Nor does it tell us which treatment will be easier for that person to continue.
The STEP 1 semaglutide results provide useful background, while our SELECT analysis explains why cardiovascular outcomes require a separate comparison.
Read the comparison without changing the question
| Question | Useful interpretation |
|---|---|
| Which group lost more weight? | Tirzepatide at the studied doses, within this trial. |
| Does everyone benefit more? | A group average does not identify an individual response. |
| Which service provides better care? | No online care services were compared. |
| What about other doses or formulations? | Do not treat unstudied products as interchangeable with these interventions. |
The trial also reported greater waist reduction with tirzepatide. Gastrointestinal adverse events were the most common in both groups, generally mild to moderate and mainly during dose escalation. “Generally” matters: an average description of tolerability does not erase the experience of someone who cannot continue treatment. A result should be read alongside the treatment burden rather than used as a substitute for that discussion.
Where the evidence stops
Because the trial was open-label, participants and clinicians knew the assigned treatment. That is a design limitation worth retaining even when the primary measurement is body weight. The absence of diabetes also matters: this comparison should not be silently relabeled as a trial in people with type 2 diabetes. Its duration is a defined observation period, not a lifetime guarantee.
Sponsor funding is relevant context, but it is not a reason to dismiss a study automatically. A useful reading asks whether the question, comparison, endpoints and limitations are visible. It also resists promoting one successful endpoint into every other endpoint. Greater weight reduction does not, by itself, prove greater cardiovascular protection, better quality of life for every participant, or superior long-term adherence.
Do not combine the weight percentages here with a separate cardiovascular trial as though they formed a single leaderboard. Our SELECT explainer concerns a different population and a different primary outcome. Choosing the outcome first is more useful than choosing the largest number first.
Bring the result into a care conversation
A useful clinician conversation starts with the goal: what health problem is being treated, what outcome matters, and what tradeoffs are acceptable? Ask how the proposed product and dose relate to the evidence, what follow-up will look like, and how difficulties with treatment will be handled. These are clinical questions before they become shopping questions.
Then compare the service around the prescription. Our provider shortlists distinguish payment and support models, while the Ro review examines one insurance-navigation route. A provider appearing on a shortlist does not inherit a clinical trial’s outcomes. Ask for a written quote naming the exact product and supply period, and use the quote comparison tool only after the product question is clear.
A lower monthly headline can be attractive while leaving medication, follow-up or a longer payment obligation unresolved. Keep those unknowns beside the clinical evidence. The strongest decision is one in which the medicine, the service and the recurring cost each have their own clear explanation.