This is the area most prone to error in Retatrutide coverage, so precision matters.
What has been published
The Phase II obesity trial (Jastreboff et al., 2023, NEJM) has been published. In 338 obese adults without diabetes, the 12 mg dose group lost an average of 24.2% at 48 weeks. In the 12 mg group, all participants lost at least 5%, 93% lost at least 10%, and 83% lost at least 15%. In higher dose groups, weight was still declining at week 48, so Phase III trials were designed to run 80 weeks.
The Phase II type 2 diabetes trial (Rosenstock et al., 2023, The Lancet) has been published. In 281 adults over 36 weeks, with dulaglutide as active comparator, the 12 mg group lost 16.9% body weight versus 2.0% for dulaglutide.
The Phase 2a liver fat substudy (Sanyal et al., 2024, Nature Medicine) has been published. In 98 patients with fatty liver, 12 mg for 24 weeks reduced liver fat by 82.4%, with 86% of patients returning to normal liver fat. Placebo: none.
One Phase III trial in type 2 diabetes (Bajaj et al., 2026, The Lancet) has been published. This is the only Phase III trial published in a journal to date. In 537 adults over 40 weeks, the 12 mg group reduced HbA1c by 1.94 percentage points versus placebo and reduced weight by 15.3% versus placebo.
What has not been published
The four TRIUMPH obesity trials are the source of the most-cited numbers.
Trial Population Reported result Status
TRIUMPH-4 Obesity + knee osteoarthritis 28.7% at 68 weeks, 12 mg Dec 2025 summary
TRIUMPH-1 Obesity, no diabetes 28.3% at 80 weeks, 12 mg May 2026 summary
TRIUMPH-2 Obesity + type 2 diabetes 20.8% at 80 weeks Summary, Jul 2026
TRIUMPH-3 Severe obesity + cardiovascular disease 22.6% at 80 weeks Summary, Jul 2026
In TRIUMPH-1, Lilly also reported that 45.3% of participants on 12 mg lost at least 30% of body weight. As of now, this figure appears only in a press release.
Why the distinction matters
The 28% figure is real in the sense that Lilly reported it. But it is not peer-reviewed, because no one outside Lilly has seen the methodology, full safety tables, or dropout analysis. Until those documents are available, it should be treated as a strong company claim, not conclusive evidence.
One more limitation worth noting: all published Retatrutide trials were funded by Lilly, and Lilly employees are co-authors on all papers. This is normal at this stage of development, but it remains a limitation.
Conclusion
Published data and press-release data are not the same thing. Understanding this distinction helps assess Retatrutide’s true evidence strength.