Retatrutide for Weight Loss: What the Evidence Shows
What human and animal studies show about Retatrutide for weight loss, how strong that evidence is, and what is still unproven.
Medically reviewed by Juan Pablo Frías, MD · · DisclosureGLP-1 / GIP / glucagon triple agonistUpdated
- Strongest evidence
- Human RCT
- Human studies
- 71
- PubMed records, our ledger
- Animal studies
- 7
- PubMed records, our ledger
- Studies we summarised
- 13
- with an outcome for weight loss
Evidence for weight loss
Each row is an outcome related to weight loss from a published study, strongest design first. Animal and cell results are labelled and are not human results. User reports are not counted as evidence here.
| Outcome | Result | Study type | Source |
|---|---|---|---|
| Body weight | Mean body weight change was -25.0% with 12 mg, -23.7% with 9 mg and -17.6% with 4 mg, versus -3.9% with placebo. | Human RCTn = 2339 | The New England journal of medicine 2026, PMID 42814954 |
| Body weight at week 80 (primary) | At week 80 body weight changed by -18·8% with 12 mg, -16·8% with 9 mg and -11·9% with 4 mg, versus -5·1% with placebo. | Human RCTn = 1152 | Lancet 2026, PMID 42810372 |
| Body weight at week 40 | Body weight changed by -15·3% with 12 mg, -13·9% with 9 mg and -11·5% with 4 mg, versus -2·6% with placebo. | Human RCTn = 537 | Lancet 2026, PMID 42250575 |
| Total fat mass (DXA) | Total fat mass fell by 26·1% with 8 mg (pooled), 23·2% with 12 mg and 15·2% with 4 mg (pooled), versus 2·6% with dulaglutide and 4·5% with placebo. | Human RCTn = 189 | The lancet. Diabetes & endocrinology 2025, PMID 40609566 |
| Lean mass share of weight loss | The authors report lean mass loss as a proportion of weight loss was similar to other obesity treatments. | Human RCTn = 189 | The lancet. Diabetes & endocrinology 2025, PMID 40609566 |
| Hunger and disinhibition | Perceived hunger and tendency to overeat were reduced with higher retatrutide doses versus placebo. | Human RCTn = 275 | Diabetes, obesity & metabolism 2025, PMID 40916752 |
| Link to weight, abdominal fat and insulin sensitivity | Liver fat reductions were significantly related to changes in body weight, abdominal fat and metabolic measures (an association, not a separate abdominal-fat result). | Human RCTn = 98 | Nature medicine 2024, PMID 38858523 |
| Body weight at 24 weeks (primary) | At 24 weeks body weight changed by -17.5% with 12 mg and -7.2% with 1 mg, versus -1.6% with placebo. | Human RCTn = 338 | The New England journal of medicine 2023, PMID 37366315 |
| Body weight at 48 weeks | At 48 weeks body weight changed by -24.2% with 12 mg and -8.7% with 1 mg, versus -2.1% with placebo. | Human RCTn = 338 | The New England journal of medicine 2023, PMID 37366315 |
| Proportion reaching 5%, 10%, 15% weight loss | With 12 mg, 100%, 93% and 83% reached a 5%, 10% and 15% weight reduction at 48 weeks, versus 27%, 9% and 2% with placebo. | Human RCTn = 338 | The New England journal of medicine 2023, PMID 37366315 |
| Body weight at 36 weeks | At 36 weeks body weight fell by 16·94% with 12 mg escalation, versus 3·00% with placebo and 2·02% with 1·5 mg dulaglutide. | Human RCTn = 281 | Lancet 2023, PMID 37385280 |
| Body weight (placebo-adjusted) | Placebo-adjusted weight reduction was dose dependent, up to -8·96 kg in the 3/6/9/12 mg group. | Human RCTn = 72 | Lancet 2022, PMID 36354040 |
| Weight loss vs other incretin drugs | Retatrutide and dual agonists achieved mean weight loss of -11.0 kg versus -9.0 kg with GLP-1RAs; retatrutide had an odds ratio of 54.6 for at least 15% weight loss. | Meta-analysisn = 29506 | Obesity 2025, PMID 40685589 |
| Body weight, BMI and waist circumference | Versus placebo, retatrutide reduced body weight by a weighted mean difference of -10.66 kg, BMI by -4.53 kg/m2 and waist circumference by -6.61 cm. | Meta-analysisn = 640 | Metabolism open 2024, PMID 39318607 |
| Steatohepatitis markers | In female mice, retatrutide over the final 2 weeks of a 31-day model reduced body weight, ALT, liver triglycerides and cholesterol, and liver inflammatory markers versus vehicle. | Animal · mouse (not a human result) | American journal of physiology. Gastrointestinal and liver physiology 2025, PMID 41056349 |
| Body weight and glycaemic control in obese mice | In obese mice, LY3437943 (retatrutide) decreased body weight and improved glycaemic control. | Animal · mouse (plus a human phase 1 single-ascending-dose study reported in the same paper) (not a human result) | Cell metabolism 2022, PMID 35985340 |
| Weight reduction after a single human dose (phase 1) | In the early single-ascending-dose human study, body weight reduction persisted up to day 43 after a single dose. | Animal · mouse (plus a human phase 1 single-ascending-dose study reported in the same paper) (not a human result) | Cell metabolism 2022, PMID 35985340 |
PubMed records for Retatrutide and weight loss: 71 human, 7 animal (search counts, not studies we reviewed). Grades follow our evidence scale.
Trial results
Phase 2 figures · verify before publishing
| Weekly dose | Weight change, 48 wk |
|---|---|
| Placebo | −2.1% |
| 1 mg | −8.7% |
| 4 mg | −17.1% |
| 8 mg | −22.8% |
| 12 mg | −24.2% |
Source: Jastreboff AM et al., New England Journal of Medicine 2023;389:514–526 (phase 2; PMID 37366315; ClinicalTrials.gov NCT04881760). Least-squares mean change at 48 weeks; the 4 mg and 8 mg rows combine both starting-dose groups. The primary end point was at 24 weeks.
How strong is it?
Strongest evidence:Human RCT evidence, 4 of 4
A human randomized trial outweighs any number of animal studies. Animal and cell results show a mechanism worth testing, not that it works in people.
Other peptides people research for weight loss
All peptides for weight loss, comparedCommon questions
Does Retatrutide help with weight loss?
In the phase 2 obesity trial, average weight change at 48 weeks reached about −24.2% at the highest dose versus −2.1% on placebo (pending a final check). It is not approved for weight loss.
Is Retatrutide approved for weight loss?
No. Retatrutide is not FDA approved for any use, including weight loss.
What is the best peptide for weight loss?
There is no single answer. Our weight loss overview compares each candidate by evidence grade and legal status rather than by popularity.
More on Retatrutide
DosageDoses used in published trials, the titration pattern and a units chart.CalculatorVial, water and dose to syringe units.Side effectsWhat labels and studies report, and what is unknown.ResultsStudy outcomes and when they were measured.PricePrice per mg and per week from dated listings. No vendor links.Legal statusFDA, compounding and WADA status with dates.
Sources
- 1Triple-Hormone-Receptor Agonist Retatrutide for Obesity: A Phase 2 Trial (Jastreboff AM et al.)New England Journal of Medicine · 2023PMID 37366315Accessed 2 Oct 2026
- 2Retatrutide, a Triple Hormone Receptor Agonist, for Treatment of Obesity (TRIUMPH-1; Jastreboff AM et al.)New England Journal of Medicine · 2026PMID 42814954Accessed 2 Oct 2026
- 3A Phase 2 Study of Once-Weekly LY3437943 Compared With Placebo in Participants Who Have Obesity or Are Overweight With Weight-Related Comorbidities (NCT04881760; arms and posted results)ClinicalTrials.gov (U.S. National Library of Medicine) · 2021clinicaltrials.govAccessed 2 Oct 2026
- 4Retatrutide in adults with obesity and type 2 diabetes (TRIUMPH-2): a double-blind, parallel-group, randomised, placebo-controlled, phase 3 trial.Lancet (London, England) · 2026PMID 42810372Accessed 2 Oct 2026
- 5Efficacy and safety of retatrutide, a GIP, GLP-1, and glucagon receptor agonist, in people with type 2 diabetes and inadequate glycaemic control with diet and exercise (TRANSCEND-T2D-1): a double-blind, randomised, phase 3 trial.Lancet (London, England) · 2026PMID 42250575Accessed 2 Oct 2026
- 6Effects of retatrutide on body composition in people with type 2 diabetes: a substudy of a phase 2, double-blind, parallel-group, placebo-controlled, randomised trial.The lancet. Diabetes & endocrinology · 2025PMID 40609566Accessed 2 Oct 2026
- 7Appetite, eating attitudes, and eating behaviours during treatment with retatrutide in adults with type 2 diabetes: Results of a phase 2 study.Diabetes, obesity & metabolism · 2025PMID 40916752Accessed 2 Oct 2026
- 8Triple hormone receptor agonist retatrutide for metabolic dysfunction-associated steatotic liver disease: a randomized phase 2a trial.Nature medicine · 2024PMID 38858523Accessed 2 Oct 2026
- 9Retatrutide, a GIP, GLP-1 and glucagon receptor agonist, for people with type 2 diabetes: a randomised, double-blind, placebo and active-controlled, parallel-group, phase 2 trial conducted in the USA.Lancet (London, England) · 2023PMID 37385280Accessed 2 Oct 2026
- 10LY3437943, a novel triple GIP, GLP-1, and glucagon receptor agonist in people with type 2 diabetes: a phase 1b, multicentre, double-blind, placebo-controlled, randomised, multiple-ascending dose trial.Lancet (London, England) · 2022PMID 36354040Accessed 2 Oct 2026
- 11Efficacy and Safety of GLP-1 Receptor Agonists, Dual Agonists, and Retatrutide for Weight Loss in Adults With Overweight or Obesity: A Bayesian NMA.Obesity (Silver Spring, Md.) · 2025PMID 40685589Accessed 2 Oct 2026
- 12Effects of once-weekly subcutaneous retatrutide on weight and metabolic markers: A systematic review and meta-analysis of randomized controlled trials.Metabolism open · 2024PMID 39318607Accessed 2 Oct 2026
- 13Retatrutide improves steatohepatitis in an accelerated mouse model of diet-induced steatohepatitis with a fructose binge.American journal of physiology. Gastrointestinal and liver physiology · 2025PMID 41056349Accessed 2 Oct 2026
- 14LY3437943, a novel triple glucagon, GIP, and GLP-1 receptor agonist for glycemic control and weight loss: From discovery to clinical proof of concept.Cell metabolism · 2022PMID 35985340Accessed 2 Oct 2026
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