The SURMOUNT-3 results show that tirzepatide added further weight loss after people had already lost weight through diet and exercise. After an initial average loss of 6.9%, the tirzepatide group lost another 18.4% over 72 weeks. The placebo group, which received a look-alike injection without tirzepatide, gained 2.5%. These were averages in a selected group, not a forecast for everyone starting treatment.
What question did the SURMOUNT-3 trial ask?
The question was simple: could medication add to weight loss that diet and exercise had already achieved?
Thomas Wadden and colleagues reported the trial in Nature Medicine in 2023. It was a phase 3 study, a large later-stage trial that measures benefits and harms. Participants were randomized, meaning assigned by chance, and double-blind, meaning neither they nor investigators knew the assignments. Eli Lilly funded the study.
Who qualified after the lifestyle lead-in?
The lead-in, the period before medication testing, lasted 12 weeks. Of 806 adults who entered it, 579 lost at least 5% and met the other requirements for randomization. Their average loss was 6.9%. The results describe those 579 people, not everyone who entered the program.
Adults qualified with a BMI, a height-to-weight screening number, of at least 30. A BMI of at least 27 qualified with a weight-related condition, such as high blood pressure. Diabetes, prior weight-loss surgery, and large recent weight changes were among the exclusions. Average age was 45.6 years; about 63% were women.
The program included eight counseling sessions, reduced-calorie eating, and a goal of at least 150 minutes of activity a week. After randomization, both groups continued nutrition and activity counseling.
The registry record, NCT04657016, documents the design. Tirzepatide targeted a maximum tolerated dose, the highest study dose a person could handle, of 10 or 15 mg weekly. The 72-week medication period included 20 weeks of planned dose increases. These were study doses, not a personal dosing plan.
What did the study measure?
There were two primary endpoints, the main results chosen before the trial began: average percentage weight change and the share losing at least another 5%. Both measured change from randomization, after the lifestyle loss.
The headline numbers use the treatment-regimen estimand, the question of what happened regardless of whether people stayed on treatment. Participants remained in their assigned groups even if they stopped injections. Missing weights were estimated statistically.
A separate efficacy estimand asked about results assuming continued treatment. That distinction explains why summaries of the same trial sometimes give different numbers.
SURMOUNT-3 results: additional loss and total loss
The main analysis found another 18.4% weight loss with tirzepatide, compared with a 2.5% gain on placebo. The paper reported an estimated 20.8-percentage-point difference, meaning the gap between the two percentage changes. The headline averages are rounded.
About 7 in 8 tirzepatide participants lost at least another 5%. About 1 in 6 placebo participants did.
| Result over 72 weeks after randomization | Tirzepatide | Placebo |
|---|---|---|
| Average weight change | −18.4% | +2.5% |
| Lost at least another 5% | 87.5% | 16.5% |
| Lost at least another 10% | 76.7% | 8.9% |
| Lost at least another 15% | 65.4% | 4.2% |
| Lost at least another 20% | 44.7% | 2.2% |
These are the paper's treatment-regimen estimates. Including the lifestyle phase, total average loss from the original starting weight was 24.3% with tirzepatide and 4.5% with placebo.
The on-treatment analysis estimated another 21.1% loss versus a 3.3% gain. Its total-loss figures were 26.6% and 3.8%. Those belong to a different analysis. Also, the initial and later percentages use different starting weights, so simply adding them gives the wrong total.
Side effects and why people stopped
About 4 in 10 tirzepatide participants reported nausea. Stomach and bowel symptoms were mostly mild or moderate and occurred mainly while doses increased.
An adverse event is a health problem reported during a trial, whether or not the medicine caused it. Serious events include problems such as those requiring hospitalization. The paper's safety table reports:
| Reported event | Tirzepatide, 287 people | Placebo, 292 people |
|---|---|---|
| Nausea | 39.7% | 14.0% |
| Diarrhea | 31.0% | 9.2% |
| Constipation | 23.0% | 6.8% |
| Vomiting | 18.1% | 1.4% |
| Serious adverse events | 5.9% | 4.8% |
| Stopped treatment because of an adverse event | 10.5% | 2.1% |
About 1 in 10 tirzepatide participants stopped because of an adverse event. A large average weight change does not mean everyone could comfortably stay on the medicine.
What the authors questioned, and what later studies added
The authors raised a key limitation: people who responded well to lifestyle support might also respond well to medication. People who did not reach the 5% threshold were not randomized. That selection could make the average loss larger than it would be in a broader population.
The study also did not compare starting medication and lifestyle support together with starting them in sequence. It cannot establish that diet first is the best order. Most participants were white, and the trial ran in only three countries.
SURMOUNT-1 results cover a trial without this successful-lifestyle entry requirement. Later, Aronne and colleagues in JAMA, 2024, tested continuing versus withdrawing tirzepatide. The SURMOUNT-4 results explain that separate maintenance question. SURMOUNT-3 did not test what happens after stopping an established course.
As of September 30, 2026, the day this article was written, a newer analysis included 515 SURMOUNT-3 participants. Sattar and colleagues published it in PLOS One on August 13, 2026. They examined weight-loss, blood-pressure, and cholesterol goals together, using measurements collected while people were on treatment. More tirzepatide participants met the combined goals. This was a post hoc analysis, a question examined after the original trial; it cannot establish fewer heart attacks or strokes.
What this means for someone considering tirzepatide
Successful diet and exercise did not close the door to additional weight loss in this trial. It also did not guarantee a particular result. Selection, dose tolerance, and time in treatment all shaped the averages. The tirzepatide clinical-trials overview places this question within the wider evidence.
As of September 30, 2026, the day this article was written, the Zepbound label, marked “Revised: 08/2026,” pairs weight treatment with reduced-calorie eating and increased physical activity.
SURMOUNT-3 tested Lilly's manufactured injections. A compounded medication is one prepared by a pharmacy for an individual prescription.
Through Promise, tirzepatide is dispensed as a compounded medication, which is different from an FDA-approved product: the formulation offered here is not FDA-approved. The FDA explains that it does not verify compounded medications' safety, effectiveness, or quality before marketing. Trial averages cannot establish the same outcomes for that preparation.
A licensed provider may still prescribe a compounded formulation; that decision is between the patient and the doctor.
What the visit needs to settle
A useful conversation connects weight history with realistic goals, side-effect tolerance, and how progress will be reviewed. The prescriber sets the actual dose and schedule.
At Promise, a licensed provider reviews every request, and not everyone qualifies.
