Retatrutide results: the weight loss numbers from every trial, by dose and by week

By Retatrutide Risk editorial team. Published September 21, 2026. Sources at the end of the page.

Retatrutide's results are the reason it is discussed at all. This page collects every efficacy figure that has been published in a peer-reviewed journal or announced by the sponsor, organized by trial, dose and time point, with the source next to each. Nothing here is estimated, extrapolated or rounded beyond what the sources report.

Phase 2 obesity trial: 48 weeks, 338 adults

Jastreboff et al. (NEJM 2023; ClinicalTrials.gov NCT04881760) randomized 338 adults with a BMI of 30 or higher, or 27 to less than 30 with at least one weight-related condition, to once-weekly retatrutide or placebo for 48 weeks. 51.8% were men. The primary end point was the percentage change in body weight at 24 weeks.

Values are least-squares mean percentage changes from baseline. Two features stand out. The curves had not flattened by 48 weeks; the 12 mg arm lost a further 6.7 percentage points between week 24 and week 48. And the 8 mg and 12 mg arms were nearly identical at 24 weeks and separated only modestly by 48 weeks.

Proportion of participants reaching weight loss thresholds at 48 weeks

Every participant on 8 mg or 12 mg who completed the trial lost at least 5% of body weight. At 12 mg, 83% lost at least 15%, which means 17% did not; the mean of -24.2% conceals a range.

Phase 2 type 2 diabetes trial: 36 weeks, 281 adults

Rosenstock et al. (Lancet 2023; NCT04867785) enrolled adults with type 2 diabetes (HbA1c 7.0 to 10.5%, BMI 25 to 50, on diet and exercise or metformin) at 42 U.S. centres. Mean age was 56.2 years and mean duration of diabetes 8.1 years. Dulaglutide 1.5 mg served as an active comparator. The primary end point was the change in HbA1c at 24 weeks.

HbA1c reductions were significantly greater than placebo at every dose except 0.5 mg, and greater than dulaglutide in the 8 mg slow-escalation and 12 mg groups. Weight reductions at 4 mg and above were significantly greater than both placebo and dulaglutide. Note that in this trial the placebo group lost 3.00%, more than the 2.1% seen in the obesity trial at 48 weeks, and that the 8 mg and 12 mg groups were indistinguishable.

Liver fat: the phase 2a substudy

Sanyal et al. (Nature Medicine 2024) report a substudy of the obesity trial in 98 participants who had metabolic dysfunction-associated steatotic liver disease with at least 10% liver fat at baseline.

All retatrutide arms differed from placebo with P below 0.001. The authors report that liver fat reductions were significantly related to changes in body weight, abdominal fat and metabolic measures associated with improved insulin sensitivity and lipid metabolism.

Phase 3 TRIUMPH results (company announcements)

The four completed phase 3 trials have been reported by Eli Lilly in press releases. These figures have not been through peer review, and the full data, including the treatment-regimen estimand that counts participants who stopped treatment, will only be available when the papers are published. The figures below are the efficacy estimand, which describes the effect while on treatment.

In TRIUMPH-1, absolute weight loss was 21.4 kg (4 mg), 29.2 kg (9 mg) and 31.9 kg (12 mg) versus 2.5 kg on placebo. In TRIUMPH-4, baseline weight averaged 112.7 kg and BMI 40.4; the 12 mg arm lost 32.3 kg. In TRIUMPH-2, the announcement reports A1C reductions of up to an average of 1.6%.

TRIUMPH-1 responder rates at 80 weeks

In TRIUMPH-4, 58.6% of the 12 mg arm lost 25% or more, 39.4% lost 30% or more and 23.7% lost 35% or more.

TRIUMPH-1 extension to 104 weeks

A subset of 532 participants with a BMI of 35 or higher continued to 104 weeks in an extension in which each arm was escalated to its maximum tolerated dose. Weight change at 104 weeks was -27.9% (participants originally on 4 mg), -29.5% (9 mg) and -30.3% (12 mg). Participants originally on placebo, switched to retatrutide in the extension, reached -19.2% at 104 weeks. This is the longest retatrutide exposure reported anywhere.

Reading the results honestly

• Group means are not individual predictions. The responder tables show that at the top dose a meaningful minority lost far less than the average.
• People with type 2 diabetes lose less. This was true at every dose in both phase 2 and phase 3, and it matches experience with earlier incretin drugs.
• The efficacy estimand overstates what a whole population would achieve, because it describes participants while on treatment. The treatment-regimen figures from phase 3 have not been released.
• Nothing is published about weight after stopping. Every trial administered retatrutide continuously; the 104-week extension continued treatment rather than withdrawing it.
• The price of the top dose is tolerability. In TRIUMPH-1, going from 9 mg to 12 mg added 2.4 percentage points of weight loss and raised discontinuation because of adverse events from 6.9% to 11.3%. The side effects article has the full picture, and the comparison with tirzepatide puts these figures next to the approved dual agonist.