Up to 30.3% average weight loss at two years: no trial had ever published numbers like these. Retatrutide’s results circulate everywhere in shorthand — a percentage, a headline — but the studies themselves are dense scientific reading. What follows is the record, trial by trial — exact figures, caveats included.
Phase 2 (NEJM, 2023): the starting point
The trial published in the New England Journal of Medicine in June 2023 followed 338 adults with obesity for 48 weeks, split between placebo and four dose levels. Average weight loss at 48 weeks:
| Dose | Average loss |
|---|---|
| 1 mg | −8.7% |
| 4 mg | −17.1% |
| 8 mg | −22.8% |
| 12 mg | −24.2% |
| Placebo | −2.1% |
Two striking details: at 8 and 12 mg, 100% of participants lost at least 5% of their body weight (27% on placebo), and the curve showed no plateau at the end of the trial — weight was still coming down at week 48. Side effects, mostly digestive, were dose-related and eased by a lower starting dose.
TRIUMPH-4 (December 2025): the first phase 3
The first phase 3 trial to report, TRIUMPH-4 followed 445 people with obesity or overweight and knee osteoarthritis for 68 weeks, at the two highest doses:
- −28.7% average weight loss at 12 mg (more than 70 lb), −26.4% at 9 mg, versus −2.1% on placebo;
- knee pain reduced by up to an average of 75.8% on the WOMAC scale, with more than one participant in eight completely free of knee pain by the end of the trial;
- improved cardiovascular markers (non-HDL cholesterol, systolic blood pressure).
TRIUMPH-1, 2 and 3 (2026): confirmation at scale
The TRIUMPH programme has enrolled more than 5,800 participants in total. The 2026 readouts:
- TRIUMPH-1 (May 2026, the pivotal obesity trial): −28.3% on average at 80 weeks and −30.3% at 104 weeks at the highest doses — in the range previously reported for bariatric surgery.
- TRIUMPH-2 and TRIUMPH-3 (July 2026): efficacy confirmed in harder-to-treat populations — type 2 diabetes, severe obesity with established cardiovascular disease (around −22.6% at 80 weeks in TRIUMPH-3) — with improved HbA1c in participants with diabetes.
What these numbers don’t tell you
Three caveats when reading these numbers, the same as for any trial:
- No head-to-head comparison: putting these percentages next to Wegovy®‘s or Mounjaro®‘s from different trials is unreliable — populations, durations and protocols differ. Only a direct trial would settle it.
- A trial is not real life: selected participants, close follow-up, structured diet and activity support throughout.
- Regulatory review is still ahead: the FDA filing is planned for early 2027 (potential US approval in late 2027, with Europe to follow). Until then, the molecule is approved nowhere — our article on retatrutide and its nicknames (“reta”, R3) covers why so many people already use it outside any medical framework, and what that implies.
For day-to-day tracking, the Doza app does include retatrutide in its catalogue — clearly labelled “Clinical trial” — as a pure journal: doses, weight and an estimated level curve, never any dose advice — and your measurements and doses never leave your iPhone.
FAQ — the retatrutide studies
How much weight loss does retatrutide show in studies?
On average −24.2% at 48 weeks at the highest dose in phase 2, −28.3% at 80 weeks and −30.3% at 104 weeks in the pivotal phase 3 trial TRIUMPH-1. These are clinical-trial averages, in supported and monitored participants.
Is retatrutide more effective than Wegovy or Mounjaro?
Its published figures are higher, but no head-to-head trial exists: comparisons across different trials are unreliable. Regulatory review will settle the benefit–risk balance.
What side effects were seen in the trials?
Mainly digestive (nausea, vomiting, diarrhoea), dose-related, generally mild to moderate, and eased by a lower starting dose — a profile close to the rest of the family.
When will retatrutide be available?
The US FDA filing is planned for early 2027, with potential US approval in late 2027. Europe would follow, with the EMA’s review and then national coverage decisions.
Sources: Jastreboff et al., NEJM 2023 — phase 2 trial · Eli Lilly — TRIUMPH-4, December 2025 · Eli Lilly — TRIUMPH-1, May 2026 · Eli Lilly — TRIUMPH-2 and 3, July 2026. General information written from the official publications and announcements — neither medical advice nor an encouragement to use an unapproved substance.