The short answer
The highest-dose group lost an average of 25.0% of its starting weight over 80 weeks, compared with 3.9% with placebo. This was a placebo comparison—not a race against tirzepatide or semaglutide.
The study in brief
TRIUMPH-1 randomly assigned 2,339 adults with obesity without diabetes to weekly retatrutide or placebo. Neither participants nor investigators knew the assigned treatment.
These are study regimens, not dose recommendations. The weight analysis counted participants according to their assigned group, including treatment interruptions. Digestive adverse events were the most common.
Percentage of starting weight
Original chart based on the study. Values are reported group averages.
| Group | Average weight change |
|---|---|
| Retatrutide 4 mg | −17.6% |
| Retatrutide 9 mg | −23.7% |
| Retatrutide 12 mg | −25.0% |
| Placebo | −3.9% |
What to take from it
The study found substantial average weight loss. It does not establish that retatrutide beats another medicine: that requires a direct comparison. Nor does an average tell us how any one person will respond.
Retatrutide remains investigational as of October 30, 2026. Lilly describes it as acting at GIP, GLP-1 and glucagon receptors; “triple agonist” describes that mechanism.
Sources
Jastreboff AM and colleagues, Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity, NEJM, 2026. Study abstract · Paper. Funded by Eli Lilly. Current development status.