Up to −20.9% body weight in 72 weeks: SURMOUNT-1 is the trial that put Mounjaro® among the reference treatments for obesity. And its three-year extension delivered a second, less famous but perhaps more important result: a 94% lower risk of progressing to type 2 diabetes in people with prediabetes. Here is the study, number by number.
The trial in brief
Published in the New England Journal of Medicine in July 2022, SURMOUNT-1 followed 2,539 adults with obesity (BMI ≥ 30) or overweight with a weight-related complication (BMI ≥ 27), without diabetes, for 72 weeks, split between placebo and three weekly tirzepatide doses.
The results at 72 weeks
| Dose | Average loss |
|---|---|
| 5 mg | −15.0% |
| 10 mg | −19.5% |
| 15 mg | −20.9% |
| Placebo | −3.1% |
About 9 in 10 participants on tirzepatide lost at least 5% of their body weight, versus roughly 3 in 10 on placebo. The most frequent side effects were digestive (nausea, diarrhoea, constipation), mostly during dose escalation, and generally mild to moderate.
One note as you read: the 5% threshold isn’t arbitrary — it defines a clinically meaningful response, and it’s also the threshold France uses for continued reimbursement.
The 3-year follow-up: the least-known result
The trial was extended to 176 weeks (nearly three and a half years) in participants with prediabetes at baseline (1,032 people):
- weight loss was sustained over time (up to −22.9% at 15 mg at 176 weeks, efficacy analysis);
- above all, 98.7% of tirzepatide-treated participants had not developed type 2 diabetes at 3 years, versus 86.7% on placebo — a 94% reduction in the risk of progressing to diabetes.
For a population where prediabetes frequently progresses to diabetes, that is a major prevention result.
What SURMOUNT-1 doesn’t say
- No direct comparison with Wegovy® in this trial: SURMOUNT-1 is placebo-controlled. (A later head-to-head trial, SURMOUNT-5, compared the two molecules — a story for another article.)
- A trial is not real life: structured diet and activity support, close follow-up, participants without diabetes.
- Averages hide variability: around −20.9%, some lose far more, others much less. Individual response can’t be predicted — it can only be observed, week after week.
That is what a journal is for: the Doza app logs your injections and weigh-ins and works out your percentage lost from your starting weight — your own curve, to set against the trial averages and show at your appointment.
FAQ — the SURMOUNT-1 trial
How much weight loss does Mounjaro show in SURMOUNT-1?
On average −15.0% at 5 mg, −19.5% at 10 mg and −20.9% at 15 mg over 72 weeks, versus −3.1% on placebo, in adults without diabetes.
Does tirzepatide prevent diabetes?
In SURMOUNT-1’s three-year extension in people with prediabetes, the risk of progressing to type 2 diabetes was cut by 94% (98.7% of treated participants remained diabetes-free, versus 86.7% on placebo).
Do the results hold over time?
Yes, within the trial: at 176 weeks, weight loss was largely maintained on treatment. What happens after stopping is a matter for other studies — and for a conversation with your doctor.
Is Mounjaro more effective than Wegovy?
SURMOUNT-1 doesn’t compare them (it’s placebo-controlled). A head-to-head trial, SURMOUNT-5, was run later — serious comparisons rest on that kind of trial, not on numbers from different studies.
Sources: Jastreboff et al., NEJM 2022 — SURMOUNT-1 · Eli Lilly — SURMOUNT-1 results (NEJM) · Eli Lilly — SURMOUNT-1 at 176 weeks: 94% lower diabetes risk. General information only: what these data mean for your case is your doctor’s call.