Retatrutide
Weight-loss research is complemented by published phase 2 DXA data in type 2 diabetes. Composition changes and demonstrated function remain separate questions.
Signal summary
Retatrutide is the clearest example of why RecompSignal separates weight efficacy from body-composition evidence maturity.
Study details
Doses studied — not a dosing recommendation. Regimens belong to the named study, formulation and population.
Phase 2 obesity trial
- Population
- 338 adults with obesity or overweight and a weight-related condition.
- Doses and administration studied
- Target groups: 1, 4, 8 or 12 mg subcutaneously once weekly. Higher-dose groups used different starting doses/escalation schemes.
- Duration
- 48 weeks; primary endpoint at week 24
- Reported finding / status
- At week 48, mean weight change was -24.2% in the 12 mg group versus -2.1% with placebo.
- Interpretation and limitations
- Gastrointestinal events were dose-related; heart-rate increases were observed. Later phase 3 sponsor results must be read separately from this published phase 2 regimen.
Source tier B · Read the original study or record
Phase 2 type 2 diabetes DXA substudy
- Population
- Adults aged 18-75 with type 2 diabetes and BMI 25-50. Of 189 substudy participants, 155 had baseline DXA and 103 completed treatment and both scans.
- Doses studied — not a dosing recommendation
- Target groups: retatrutide 0.5, 4, 8 or 12 mg subcutaneously weekly; comparator dulaglutide 1.5 mg weekly or placebo. The 4/8 mg groups used differing starting-dose schemes.
- Duration
- 36 weeks
- Reported finding
- Fat mass fell 15.2%, 26.1% and 23.2% in pooled 4 mg, pooled 8 mg and 12 mg groups, respectively, versus 4.5% with placebo. Authors reported lean loss as a share of weight loss similar to other obesity treatments.
- Limitations
- Incomplete DXA follow-up and on-treatment analysis limit interpretation. Diabetes population; do not generalize automatically. DXA lean mass is not muscle strength. These findings do not establish complete lean preservation or superior function.
Source tier B · Published DXA substudy (2025)
Outcome Evidence Strength
Published randomized evidence measures weight, fat and lean mass. Composition evidence includes a 36-week type 2 diabetes substudy; lean loss occurred. Demonstrated strength/function benefit is not established in these cited studies.
What is actually established?
- Lilly reported average 28.3% weight loss at 80 weeks for the 12 mg group in TRIUMPH-1.
- In July 2026, Lilly reported additional positive Phase 3 TRIUMPH-2 and TRIUMPH-3 results.
- Lilly has stated that it plans a U.S. regulatory submission in Q1 2027.
What is not established?
- Retatrutide remains investigational and is not FDA-approved.
- Detailed peer-reviewed Phase 3 body-composition evidence is not yet as mature as the weight-loss evidence.
- Strong weight loss does not prove superior lean-mass preservation.
Still being studied
Detailed peer-reviewed Phase 3 composition, lean-tissue and function outcomes—and how those signals compare with established therapies.
Best human evidence at a glance
| Evidence | Population | Comparator & duration | Outcome measured | Evidence state |
|---|---|---|---|---|
| Phase 2 DXA substudy | Adults with type 2 diabetes | Placebo and dulaglutide · 36 weeks | Fat and lean mass by DXA | Peer-reviewed randomized substudy; incomplete scan follow-up. |
| TRIUMPH-1 | Adults with obesity or overweight, without diabetes | Placebo · 80 weeks | Scale weight and metabolic outcomes | Sponsor-reported Full peer-reviewed Phase 3 detail remains important. |
| TRIUMPH-2 / 3 | Additional Phase 3 populations | Controlled Phase 3 programs | Weight and cardiometabolic outcomes | Sponsor-reported Composition-specific interpretation remains limited. |
Safety evidence context
Safety and tolerability evidence is still developing within an investigational Phase 3 program. Sponsor summaries are not a substitute for complete peer-reviewed and regulatory review.
Interpretation boundary
This card tracks research and does not recommend investigational use, dosing or sourcing.
Added the 2025 DXA substudy; fat and lean evidence ratings are now 3/5. These rate evidence for measured change, not preservation. Function benefit remains 0/5.
Why the triple-agonist mechanism matters—and what it does not prove.
Use this short explainer as an entry point, then return to the source-labeled evidence above.
Explore the pipelineEvidence sources
TRIUMPH-1 topline results
TRIUMPH-2 and TRIUMPH-3; Q1 2027 submission target