Average Weight Loss on Zepbound: The SURMOUNT Numbers

If you are weighing whether Zepbound is worth it, or trying to set a realistic target, the most useful number is the one that comes straight from its pivotal trial. Zepbound is the obesity brand of tirzepatide, and its headline efficacy data come from SURMOUNT-1, a 72-week randomized trial of 2,539 adults with obesity or overweight, published in the New England Journal of Medicine in 2022. This piece lays out the tirzepatide weight loss by dose from that trial, in plain numbers, and — just as importantly — what those averages do and don’t tell you about your own likely result.

Want to translate these percentages into pounds for your own starting weight? Our GLP-1 weight loss projector does that math for you before we get into the trial detail.

The headline SURMOUNT-1 numbers

SURMOUNT-1 randomized participants to one of three tirzepatide maintenance doses — 5 mg, 10 mg, or 15 mg once weekly — or placebo, on top of a reduced-calorie diet and increased physical activity. Everyone started at 2.5 mg and titrated up over 20 weeks. The average baseline body weight was about 104.8 kg (roughly 231 lb) and the average BMI was 38.

Here is the average change in body weight from baseline at week 72, using the trial’s primary (treatment-regimen) analysis:

In SURMOUNT-1, average weight loss over 72 weeks was about 15% on 5 mg, 19.5% on 10 mg, and 20.9% on 15 mg of tirzepatide — versus roughly 3% on placebo.

Weekly dose	Average weight change at 72 weeks
Placebo	−3.1%
Tirzepatide 5 mg	−15.0%
Tirzepatide 10 mg	−19.5%
Tirzepatide 15 mg	−20.9%

For someone starting near the trial average of ~231 lb, −20.9% works out to roughly 48 lb; −15.0% is about 35 lb. Placebo — diet and activity alone, plus a weekly dummy injection — averaged around 7 lb.

You may also see slightly higher figures quoted (about 16.0%, 21.4%, and 22.5%). Those come from a second, “efficacy” analysis that estimates the effect in people who took the drug as directed without needing rescue interventions. Both sets of numbers are legitimate; the table above is the more conservative, real-world-style estimate, which is why we lead with it.

Why the dose curve flattens

The pattern in that table matters. Going from 5 mg to 10 mg added about 4.5 percentage points of average loss. Going from 10 mg to 15 mg added only about 1.4. In other words, the dose-response curve is real but it bends: more milligrams buy more loss, but with diminishing returns near the top.

That is a useful thing to know before you assume the maximum dose is the goal. Tirzepatide is a dual GIP/GLP-1 receptor agonist, and the reasons that mechanism produces this kind of dose-response are covered in our explainer on how the dual agonist changed the field. For many people, a middle dose delivers most of the benefit; the label lists 5 mg, 10 mg, and 15 mg all as valid maintenance doses precisely because the right one is individual.

An average is not a promise

This is the part that gets lost when a number like “up to 22.5%” ends up on a billboard. An average is the center of a wide spread, not a floor.

SURMOUNT-1 reported that roughly 85% of people on 5 mg, 89% on 10 mg, and 91% on 15 mg lost at least 5% of their body weight — compared with about 35% on placebo. Those are strong response rates. But flip them around: a meaningful minority lost less than 5%, and some lost very little. On the other end, plenty of participants lost far more than the average. Your own result depends on adherence, diet, activity, sleep, other medications, and biology that no trial average can predict for you.

So treat the table as a benchmark to orient by, not a target you are owed. If you are tracking your own loss against these figures, do it over months, not weeks, and expect your personal line to wobble around the trend.

How these numbers compare and where they came from

Tirzepatide’s averages in SURMOUNT-1 are among the largest reported for a weight-management drug, and they sit above the roughly 15% average seen for semaglutide 2.4 mg (Wegovy) in its own pivotal STEP-1 trial. But cross-trial comparisons are rough — different populations, durations, and analyses — so the cleaner comparison is a head-to-head, which we get into elsewhere.

Two framing points worth keeping straight:

• These are results with lifestyle change built in. Every arm, including placebo, received diet and activity counseling. The drug’s effect is on top of that foundation, not a replacement for it.
• The trial ran 72 weeks. Weight loss on tirzepatide builds over roughly the first year and then tends to plateau; the trial averages reflect that full ramp, not month one.

If you want the plain-language version of what the drug is, who it’s approved for, and how it’s dosed, start with our explainer on what Zepbound is. The dosing, indication, and titration details in this article come directly from the FDA label.

The takeaway

In SURMOUNT-1, Zepbound produced average weight loss of about 15% at 5 mg, 19.5% at 10 mg, and 20.9% at 15 mg over 72 weeks, versus roughly 3% on placebo — with 85–91% of participants losing at least 5% of body weight. The dose-response is real but flattens near the top, and every one of those figures is an average wrapped around a wide range of individual outcomes. Use them to set expectations, not to grade yourself.

To see what these percentages mean for your specific starting weight, run the numbers through our GLP-1 weight loss projector, and for the full picture on starting and staying on these medications, see our complete GLP-1 guide.

This article is educational and not medical advice. Trial averages describe groups, not individuals; decisions about Zepbound belong with a clinician who knows your history.

Sources

• Jastreboff AM et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). N Engl J Med 2022 (PubMed)
• Zepbound (tirzepatide) prescribing information — DailyMed (FDA label)