Retatrutide Results: How Much Weight Loss Do Studies Show?
What retatrutide trials actually report: Phase 2 weight loss up to ~24% at 48 weeks, diabetes and liver-fat data, and Phase 3 topline figures — with sources.
Retatrutide (LY3437943) is an investigational triple agonist that has produced some of the largest weight-loss figures reported for any obesity drug. This guide sticks to what the published trials and official trial readouts show — with the sources — and flags clearly where the widely repeated numbers are not yet verifiable.
Retatrutide is not an approved medication. It remains investigational and is being studied in clinical trials. Nothing here is medical advice.
The Phase 2 obesity trial: the headline numbers
The most-cited evidence is the Phase 2 obesity trial published in the New England Journal of Medicine in 2023 (Jastreboff et al.). It enrolled 338 adults with obesity and ran for 48 weeks. Average (least-squares mean) body-weight change by dose:
| Dose | Weight change at 48 weeks |
|---|---|
| Placebo | −2.1% |
| 1 mg | −8.7% |
| 4 mg | −17.1% |
| 8 mg | −22.8% |
| 12 mg | −24.2% |
So the commonly quoted "up to ~24% at 48 weeks" figure is accurate — it's the 12 mg group average. Weight loss was already well underway by the halfway point (about −17.5% at the 12 mg dose by 24 weeks) and had not plateaued by week 48, which is part of why the drug drew so much attention.
The proportion of participants hitting weight-loss milestones at 48 weeks was also high at the upper doses:
| Lost at least… | 4 mg | 8 mg | 12 mg | Placebo |
|---|---|---|---|---|
| 5% of body weight | 92% | 100% | 100% | 27% |
| 10% of body weight | 75% | 91% | 93% | 9% |
| 15% of body weight | 60% | 75% | 83% | 2% |
We're deliberately not listing ≥20%, ≥25% or ≥30% responder percentages: those figures circulate widely but we couldn't confirm exact values in the openly available trial report, so we're leaving them out rather than publish numbers we can't source.
Diabetes and liver-fat trials
Retatrutide has been studied beyond simple weight loss.
In a separate Phase 2 trial in people with type 2 diabetes published in The Lancet (Rosenstock et al., 2023), the 12 mg dose reduced HbA1c (a long-term blood-sugar marker) by about 2.16 percentage points over 36 weeks — a larger reduction than the active comparator dulaglutide — alongside weight loss of roughly 17% at the higher doses.
A dedicated Phase 2a trial in fatty liver disease (MASLD), published in Nature Medicine in 2024 (Sanyal et al.), reported dramatic reductions in liver fat: at 48 weeks, liver fat content fell by about 86% at the 12 mg dose, and 93% of participants on 12 mg reached normal liver fat levels (under 5%), versus none on placebo. These are striking, though it was a small study (98 participants).
Phase 3 topline data — promising, but not yet peer-reviewed
Retatrutide's Phase 3 program (TRIUMPH) began reporting in late 2025 and 2026. Two important points before the numbers:
- These are company topline announcements, not peer-reviewed publications. The full data and independent review aren't published yet.
- The first readouts come from specific populations, so they aren't a clean stand-in for a general-obesity result.
With that framing, Lilly's December 2025 topline announcement for TRIUMPH-4 — a trial in adults with obesity and knee osteoarthritis — reported average weight loss of about 28.7% at the 12 mg dose over 68 weeks (roughly 71 pounds), with meaningful reductions in knee-osteoarthritis pain. A subsequent topline announcement in May 2026 for the registrational obesity trial TRIUMPH-1 reported average loss of about 28.3% at 12 mg. Several other TRIUMPH trials had not yet read out, and those results are not public — so any figures floating around for them should be treated as speculation.
Why "before and after" photos deserve skepticism
Searches for retatrutide results surface a lot of user-posted before/after photos. Treat them cautiously:
- Trial averages reflect controlled dosing, supervised escalation, and lifestyle support that random online users may not replicate.
- Products sold online as "retatrutide" are not verified to be the same molecule, dose, or purity as the trial drug. See tirzepatide vs retatrutide for why the research-grade vs approved-medicine distinction matters.
- Photos can't show side effects, muscle loss, or whether the loss was sustained.
The trustworthy numbers are the trial figures above, not anecdotes.
What happens if you stop?
This is where the evidence runs out for retatrutide specifically: there is no published retatrutide discontinuation or maintenance study. What we can say comes from the closely related drug tirzepatide. In the SURMOUNT-4 trial (JAMA, 2024), people who switched from tirzepatide to placebo regained a large share of their lost weight over the following year, while those who continued kept losing. GLP-1-class drugs broadly show significant regain after stopping.
The reasonable expectation, then, is that retatrutide's results would also depend on continued treatment and lifestyle change — but for retatrutide itself, that's an inference from related drugs, not a proven finding.
The bottom line
Retatrutide's trial results are genuinely among the strongest reported in obesity medicine: about 24% average weight loss at 48 weeks in Phase 2, with higher Phase 3 topline figures and large metabolic and liver-fat improvements. But "investigational" still applies — the Phase 3 data isn't peer-reviewed, the durability question is unanswered for this specific drug, and it isn't approved or available as a prescription product.
For how the trials structured dosing, see retatrutide dosing in clinical trials; for what the drug does mechanistically, see how retatrutide works; and for the safety picture, see retatrutide side effects.
FAQ
How much weight do people lose on retatrutide?
In the Phase 2 obesity trial, participants on the highest 12 mg dose lost about 24% of body weight on average at 48 weeks, versus about 2% on placebo. The 4 mg dose averaged about 17%. Phase 3 topline data has reported even higher figures, but that data is not yet peer-reviewed.
Is retatrutide more effective than Ozempic or Mounjaro?
Cross-trial comparisons suggest retatrutide's Phase 2 figures (~24% at 48 weeks) run higher than semaglutide's (~15%) and tirzepatide's (~21%) pivotal results, but these are separate trials in different populations, not head-to-head comparisons, and retatrutide is not approved.
How long does it take to see results on retatrutide?
In the Phase 2 trial, weight loss was already substantial by 24 weeks (around 17–18% at the higher doses) and continued to 48 weeks without a clear plateau.
Do you keep the weight off after stopping retatrutide?
There is no published retatrutide-specific data on stopping. For the closely related drug tirzepatide, switching to placebo led to substantial weight regain, and the GLP-1 class generally shows significant regain after discontinuation. Durability after stopping retatrutide is inferred, not established.
References
Jastreboff AM, Kaplan LM, Frías JP, et al. Triple–hormone-receptor agonist retatrutide for obesity — a phase 2 trial. New England Journal of Medicine, 2023.
Rosenstock J, Frias J, Jastreboff AM, et al. Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, phase 2 trial. The Lancet, 2023.
Sanyal AJ, Kaplan LM, Frías JP, et al. Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial. Nature Medicine, 2024.
Eli Lilly and Company. Lilly's triple agonist retatrutide delivered weight loss in first Phase 3 trial (TRIUMPH-4 topline). December 2025.
Aronne LJ, Horn DB, le Roux CW, et al. Continued tirzepatide treatment vs withdrawal on weight maintenance (SURMOUNT-4). JAMA, 2024.