Retatrutide Weight Loss Results
Phase 2 and Phase 3 clinical trial data — dose-level results, study durations, and what the numbers actually mean
In Phase 2 trials, participants taking 12 mg of retatrutide once weekly lost an average of 24.2% of body weight over 48 weeks (NEJM, 2023). Phase 3 TRIUMPH-1 topline results (May 2026) reported 28.3% mean weight loss at 80 weeks and 30.3% at 104 weeks in the 12 mg arm. These are mean results from controlled trials — individual outcomes vary. Retatrutide is not FDA-approved and is not commercially available as of September 2026.
Clinical Trial Weight Loss Data
All figures below are mean (average) weight loss from baseline across participants in each dose group. Phase 3 data are topline announcements from Eli Lilly investor relations and have not yet been peer-reviewed. Phase 2 data are from the published NEJM study.
| Trial | Phase | Duration | Dose | Mean Weight Loss | Placebo | Source |
|---|---|---|---|---|---|---|
| Phase 2 (NCT04881760) | Phase 2 | 48 weeks | 12 mg once weekly | −24.2% | −2.1% | NEJM, 2023 ↗ |
| Phase 2 (NCT04881760) | Phase 2 | 48 weeks | 8 mg once weekly | −22.8% | −2.1% | NEJM, 2023 ↗ |
| TRIUMPH-1 (topline) | Phase 3 | 80 weeks | 12 mg once weekly | −28.3% | Not disclosed | Eli Lilly, May 2026 ↗ |
| TRIUMPH-1 (extension, topline) | Phase 3 | 104 weeks | 12 mg once weekly | −30.3% | Not disclosed | Eli Lilly, May 2026 ↗ |
| TRIUMPH-2 (topline) | Phase 3 | 80 weeks | 12 mg once weekly | −20.8% | −4.0% | Eli Lilly, July 2026 ↗ |
| TRIUMPH-2 (topline) | Phase 3 | 80 weeks | 9 mg once weekly | −19.1% | −4.0% | Eli Lilly, July 2026 ↗ |
| TRIUMPH-2 (topline) | Phase 3 | 80 weeks | 4 mg once weekly | −12.7% | −4.0% | Eli Lilly, July 2026 ↗ |
Phase 3 figures are topline announcements only — not peer-reviewed. Participant counts and placebo data for Phase 3 were not disclosed in topline releases. All results are mean values; individual outcomes vary.
Phase 2 Results — The Published Evidence
The most thoroughly documented retatrutide weight loss data come from a Phase 2 randomized controlled trial (NCT04881760) published in the New England Journal of Medicine in June 2023. The trial enrolled 338 adults with obesity (BMI ≥ 30) or overweight (BMI ≥ 27) with at least one weight-related comorbidity, randomized across five dose groups plus placebo over 48 weeks.
At 48 weeks, mean weight loss by dose group was:
- 1 mg: −8.7%
- 4 mg: −17.3%
- 8 mg: −22.8%
- 12 mg: −24.2%
- Placebo: −2.1%
Notably, the weight loss curve had not plateaued at 48 weeks in the highest dose groups, suggesting continued loss with longer treatment — a pattern confirmed by the Phase 3 extension data showing 30.3% at 104 weeks.
Phase 3 TRIUMPH Results — Topline Data
Eli Lilly announced topline results from the Phase 3 TRIUMPH program in two press releases in 2026. These are investor relations announcements — not peer-reviewed publications. Full data, including participant counts, confidence intervals, and secondary endpoints, have not yet been publicly disclosed.
Important: TRIUMPH-2 enrolled participants with both obesity and type 2 diabetes. People with type 2 diabetes typically lose less weight on GLP-1 receptor agonists than people with obesity alone — this is a known pharmacological pattern, not a failure of the drug. The TRIUMPH-1 and TRIUMPH-2 populations are not directly comparable.
What These Numbers Cannot Tell You
Clinical trial averages describe what happened to a group of participants under controlled conditions. They cannot predict individual outcomes. Several factors limit how these results should be interpreted:
Trial populations are not representative
Clinical trial participants are screened for eligibility and typically exclude people with certain medical conditions, recent medication use, or other factors. Real-world patients are more diverse.
Phase 3 data are not yet peer-reviewed
TRIUMPH topline results are investor announcements. The full dataset — including confidence intervals, secondary endpoints, and adverse event rates — has not been published in a peer-reviewed journal as of September 2026.
Individual variability is substantial
In the Phase 2 trial, weight loss ranged widely within each dose group. Some participants lost significantly more than the mean; others lost less or did not respond.
Results require sustained treatment
Weight loss in GLP-1 trials accumulates over months. The 28.3% figure reflects 80 weeks of continuous treatment — not a short-term result.
Retatrutide is not available
These results come from authorized clinical trials. Retatrutide is not FDA-approved and is not commercially available. Products sold online as "retatrutide" are not the pharmaceutical-grade compound used in these trials.
Frequently Asked Questions
How much weight did people lose on retatrutide in clinical trials?
In the Phase 2 trial published in the New England Journal of Medicine (2023), participants taking 12 mg once weekly lost an average of 24.2% of body weight over 48 weeks. Phase 3 TRIUMPH-1 topline results (May 2026) reported 28.3% mean weight loss at 80 weeks and 30.3% at 104 weeks in the 12 mg arm. These are mean results from controlled trials — individual outcomes vary.
What is the difference between Phase 2 and Phase 3 weight loss results?
Phase 2 trials are smaller, shorter studies designed primarily to evaluate safety and identify effective doses. Phase 3 trials are larger, longer, and designed to confirm efficacy for regulatory approval. Retatrutide's Phase 3 results (28.3% at 80 weeks) exceeded Phase 2 results (24.2% at 48 weeks), likely reflecting the longer study duration and larger, more diverse population.
What does "mean weight loss" mean in a clinical trial?
"Mean weight loss" is the arithmetic average across all participants in a dose group. Some participants lost more than the mean; others lost less. Clinical trial averages cannot predict what any individual will experience. Factors including baseline weight, diet, physical activity, adherence, and individual biology all affect outcomes.
How does retatrutide's weight loss compare to tirzepatide?
Tirzepatide (Zepbound) produced approximately 20–22% mean weight loss at 72 weeks in the SURMOUNT-1 Phase 3 trial. Retatrutide's Phase 3 TRIUMPH-1 topline reported 28.3% at 80 weeks. These are separate trials in different populations — no head-to-head randomized controlled trial comparing the two drugs has been published.
Are the Phase 3 results peer-reviewed?
As of September 2026, the TRIUMPH Phase 3 results are topline announcements from Eli Lilly's investor relations communications. Full peer-reviewed publications have not yet appeared. Topline results are preliminary and may differ from the final published data.
What were the TRIUMPH-2 dose-level results?
TRIUMPH-2 topline results (July 2026) reported mean weight loss at 80 weeks of: 4 mg — 12.7%; 9 mg — 19.1%; 12 mg — 20.8%; placebo — 4.0%. TRIUMPH-2 enrolled participants with obesity and type 2 diabetes, a population that typically shows lower weight loss than obesity-only populations.
What are the limitations of retatrutide weight loss data?
Key limitations include: (1) Phase 3 data are topline only — not yet peer-reviewed; (2) trial participants are not representative of all people with obesity; (3) weight loss was measured under controlled trial conditions with regular monitoring; (4) long-term maintenance data beyond 104 weeks are not yet available; (5) retatrutide is not FDA-approved and is not commercially available.
Does weight come back after stopping retatrutide?
Long-term maintenance data for retatrutide are not yet available. Evidence from other GLP-1 receptor agonists (semaglutide, tirzepatide) consistently shows substantial weight regain after discontinuation. Whether retatrutide differs in this regard is not yet established.
How much weight loss per week does retatrutide produce?