TRIUMPH-1: a fuller picture
What interests me about the latest retatrutide evidence is the chance to ask more than “How much weight did people lose?” I also want to understand movement, sleep and what treatment was like to live with.
This entry was updated on 4 October 2026 after the TRIUMPH-1 paper appeared in the New England Journal of Medicine on 29 September. The earlier June reporting remains part of the story below.
The trial included 2,339 adults with obesity without diabetes and followed treatment for 80 weeks. People were assigned by chance to treatment groups. In the analysis intended to reflect everyone assigned to a group, average weight reductions were 17.6%, 23.7% and 25.0% for the 4 mg, 9 mg and 12 mg groups, compared with 3.9% for placebo. Those doses identify the study groups; they are not instructions for use.
There were also groups of 574 participants with knee osteoarthritis and 243 with obstructive sleep apnoea, a condition involving repeated breathing interruptions during sleep. The abstract reports improvements in pain and breathing-event frequency in those groups. It does not tell us every participant had every benefit.
Stomach and bowel side effects were common. Lilly funded the trial. This update checked the publication details and abstract, rather than carrying out a full review of the paper and its extra data.
Why you may have seen a different number
You may have seen 28.3% in the June announcement. That headline and the published figures above use different ways of analysing the results. They should not be swapped around as though they answer exactly the same question.
I find it more useful to keep the comparison beside the number than to pick whichever sounds biggest. Retatrutide remains investigational, and none of these results verifies a product sold online.
The earlier June report
Lilly’s 6 June 2026 announcement brought together findings presented at the American Diabetes Association meeting. The diabetes results were also published in The Lancet.
Its selected results included 28.3% average weight reduction over 80 weeks in TRIUMPH-1’s highest-dose group. In a separate diabetes trial, TRANSCEND-T2D-1, HbA1c — a measure of blood sugar over time — fell by up to 2.0 percentage points at 40 weeks.
The company also reported knee-pain scores falling by up to 4.3 points on a 0–10 scale in the osteoarthritis trial within TRIUMPH-1, and breathing disturbances falling by up to 36.1 events an hour in the sleep-apnoea trial.
These were selected changes from where people started, rather than the extra improvement compared with placebo. They involved different groups and doses. Less knee pain does not establish that cartilage has repaired.
The same June report described stomach and bowel symptoms and altered skin sensations. In TRIUMPH-1, 11.3% of the highest-dose group stopped because of adverse events, compared with 4.9% taking placebo.
For me, that is the point of keeping this history together: the benefits, the difficult parts and the way each number was calculated all belong in the conversation.