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Retatrutide: weight and fat research · 2 min read

Retatrutide phase 3 TRIUMPH-1 results: 80-week weight change

Published by Zynx Biopharma · Updated

Synopsis

In the 2026 TRIUMPH-1 phase 3 trial, mean body weight changed by −25.0% in the 12 mg Retatrutide group versus −3.9% with placebo at 80 weeks. The study enrolled adults with obesity without diabetes. These are group averages for body weight, not body-fat percentages or predictions for an individual.

Educational research information. Published studies do not test or endorse Zynx materials. This is not medical advice.

What were the TRIUMPH-1 weight-loss results?

The randomised, double-blind phase 3 trial assigned 2,339 adults with obesity without diabetes to Retatrutide or placebo for 80 weeks. The journal reported the mean percentage change in body weight using a treatment-regimen, intention-to-treat analysis. Dose names below identify study groups; they are not instructions for use.

TRIUMPH-1: mean change in body weight from baseline at week 80
Study armMean body-weight change
Retatrutide 4 mg−17.6%
Retatrutide 9 mg−23.7%
Retatrutide 12 mg−25.0%
Placebo−3.9%

Sources: Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity

Does 25.0% mean 25.0% body-fat loss?

No. The result is a percentage change in total body weight from the start of the trial. Body weight includes fat, lean tissue and water. For illustration only, 25.0% of a 100 kg starting weight is 25 kg; the published average does not predict any person's result or measure how much of that change was fat.

The placebo group also had a mean 3.9% reduction. The difference between the 12 mg group and placebo was 21.0 percentage points in this trial, not 25 percentage points.

Sources: Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity

How does this differ from the 24.2% phase 2 headline?

The earlier phase 2 obesity trial reported a 24.2% estimated mean body-weight reduction in its 12 mg group versus 2.1% with placebo at 48 weeks. TRIUMPH-1 is a separate, larger phase 3 trial reporting results at 80 weeks with a different analysis. The 24.2% and 25.0% figures should not be treated as a direct head-to-head comparison or combined into a single average.

Sources: Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity; Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial

What are the safety and interpretation limits?

The most common adverse events in the published TRIUMPH-1 abstract were gastrointestinal. The trial assessed a defined population under clinical supervision; its results do not establish outcomes in people with diabetes, long-term results beyond the study period, or the properties of a separately supplied research material. Lilly funded the study.

This article summarises the published trial abstract and the earlier phase 2 paper. The original publications contain the methods, full adverse-event reporting and disclosures. Zynx does not offer Retatrutide for purchase on this site.

Sources: Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity; Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial

Sources and further reading

This guide summarises selected sources. Original publications contain the full methods, results and disclosures; the selection is not a systematic review.

  1. Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity (external)

    Jastreboff et al. New England Journal of Medicine (published 29 September 2026). DOI: 10.1056/NEJMoa2604169. TRIUMPH-1, randomised phase 3 trial; weight results use the treatment-regimen estimand.

  2. Triple-Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial (external)

    Jastreboff et al. New England Journal of Medicine (2023). DOI: 10.1056/NEJMoa2301972. Earlier, separate 48-week obesity trial.

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