Best Peptides for Weight Loss
Most "best peptide" lists rank by popularity. This one ranks by evidence: how much weight was lost, in how many people, over how long, in a published trial. That filter removes about half the compounds usually recommended for fat loss — and it puts one clear group on top.
One methodological note, because it changes the numbers you will see quoted elsewhere. Modern obesity trials report each result twice. One analysis counts everyone randomised, including those who stopped the drug early. The other models what would have happened if everyone had stayed on it. The second is always the larger number, and it is the one marketing quotes.
The trap is that the three sponsors give these two analyses six different names. What Lilly calls the treatment-regimen estimand, Novo Nordisk calls treatment policy. What Lilly calls efficacy, Novo calls trial product in one trial andif-all-adhere in another. Same two ideas, six labels — which makes it very easy to compare a drug's flattering number against a competitor's conservative one without noticing.Every figure in the ranking and the chart below is the count-everyone analysis, whatever its sponsor calls it, so the comparison holds.
| Trial | Count-everyone analysis | Assume-full-adherence analysis | Gap |
|---|---|---|---|
| Retatrutide, TRIUMPH-1, 80 wk | −25.0% | −28.3% | 3.3 pp |
| Tirzepatide, SURMOUNT-1, 72 wk | −20.9% | −22.5% | 1.6 pp |
| CagriSema, REDEFINE 1, 68 wk | −20.4% | −22.7% | 2.3 pp |
| Semaglutide, STEP-1, 68 wk | −14.9% | −16.9% | 2.0 pp |
| Survodutide, SYNCHRONIZE-1, 76 wk | −13.0% | −16.6% | 3.6 pp |
Read down the gap column and the problem is obvious: the difference between the two conventions is 1.6 to 3.6 points, which is larger than the gap between several adjacent compounds. Pick the wrong column for one drug and you can reorder the ranking without a single number being false.
One limit no amount of estimand discipline fixes: these are still five separate trials with different durations, populations and placebo responses. Retatrutide's 80 weeks against semaglutide's 68 is a real advantage in the numbers that has nothing to do with the drug. Only REDEFINE 4, discussed below, tested two of these against each other directly.
The ranking at a glance
| # | Compound | Mechanism | Best published result | Evidence |
|---|---|---|---|---|
| 1 | Retatrutide | GIP + GLP-1 + glucagon | −25.0% at 80 weeks | Phase 3 topline, not yet published |
| 2 | Tirzepatide | GIP + GLP-1 | −20.9% at 72 weeks | Approved, large Phase 3 |
| 3 | CagriSema (cagrilintide + semaglutide) | Amylin + GLP-1 | −20.4% at 68 weeks | Phase 3 published; lost its head-to-head |
| 4 | Semaglutide | GLP-1 | −14.9% at 68 weeks | Approved, large Phase 3 |
| 5 | Survodutide | GLP-1 + glucagon | −13.0% at 76 weeks | Phase 3 published, NEJM 2026 |
| 6 | 5-Amino-1MQ | NNMT inhibition | Preclinical only | Animal data |
| 7 | AOD-9604 | hGH fragment | Not superior to placebo | Human trials, negative |
| 8 | MOTS-c | Mitochondrial peptide | Preclinical metabolic effects | Animal data only |
1. Retatrutide — the strongest data available
Retatrutide hits three receptors: GIP and GLP-1, like tirzepatide, plus glucagon. The glucagon arm increases energy expenditure rather than only suppressing appetite, which appears to be why the numbers are higher than anything before it. Phase 2 reported 24.2% at 48 weeks in the 12 mg arm with the curve still descending; Phase 3 TRIUMPH-1 then reported 25.0% at 80 weeks counting everyone randomised, or 28.3% assuming full adherence.
You will see 30.3% quoted almost everywhere, usually as "the first obesity drug past 30%". That figure comes from a 104-week extension of only 532 participants — those with a BMI of 35 or above who finished the first 80 weeks and tolerated their dose, then escalated to the maximum dose each could take. It is a real result for that group, and it is not comparable to a whole-trial number from any other drug, so it is not the figure used in the ranking above.
Two more limits worth stating. None of the TRIUMPH results has been peer-reviewed yet — they are press releases and conference presentations. And the catch on retatrutide is regulatory rather than pharmacological: it is not approved, so it exists only as a research compound. Dosing follows a four-week titration from 2 mg toward targets of 4, 9 or 12 mg weekly — see our retatrutide dosage guide for the full schedule.
Verdict: the most effective compound in the class by a clear margin, and the least accessible.
Retatrutide (RTA) — 10 mg — American Peptides
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2. Tirzepatide — the best evidence-to-availability ratio
Tirzepatide's SURMOUNT-1 trial reported 20.9% weight reduction at 72 weeks at the 15 mg dose, in 2,539 participants. Unlike retatrutide it is an approved medicine, which means a prescription pathway exists and the safety database is genuinely large.
Verdict: if you want the strongest result that is actually approved, this is it.
3. CagriSema — amylin plus GLP-1
Cagrilintide is a long-acting amylin analogue; paired with semaglutide it produced 20.4% reduction at 68 weeks in the REDEFINE 1 Phase 3 trial. You will often see 22.7% quoted instead — that is the trial-product estimand assuming full adherence, not the primary result. The interesting part is the mechanism: amylin signals satiety through a pathway independent of GLP-1, so the two components add rather than overlap.
REDEFINE 4: the head-to-head that CagriSema lost
Almost every comparison in this class is indirect — different trials, different populations, different years. REDEFINE 4 is the rare exception: 809 adults randomised to CagriSema or tirzepatide 15 mg directly against each other for 84 weeks. Novo Nordisk reported the result in February 2026, and CagriSema did not meet its primary endpoint of non-inferiority.
| At 84 weeks | CagriSema | Tirzepatide 15 mg |
|---|---|---|
| Weight change, "if-all-adhere" estimand | −23.0% | −25.5% |
| Weight change, treatment-regimen | −20.2% | −23.6% |
Two honest caveats. The trial was open-label — everyone knew which drug they were on, which is a real limitation in a head-to-head where the outcome is behaviourally influenced. And Novo did not disclose the numerical non-inferiority margin, so how far short CagriSema fell cannot be stated precisely; only that it fell short. Note also that Novo calls its adherence-assuming analysis the "if-all-adhere" estimand while Lilly calls the same concept the "efficacy" estimand — three sponsors, three labels, one idea.
Verdict: a strong combination that lost the only head-to-head it has fought. The mechanism remains genuinely interesting; the claim that it beats tirzepatide does not survive contact with REDEFINE 4.
4. Semaglutide — the most studied
14.9% at 68 weeks in STEP-1, plus cardiovascular outcome data from SELECT that no other compound in this list has. Less weight loss than the newer agents, but the deepest evidence base and the longest real-world track record.
Verdict: the conservative choice, and the one with proven outcomes beyond the scale.
5. Survodutide — no longer a Phase 2 compound
Survodutide is a GLP-1 and glucagon dual agonist, and it moved up a tier in June 2026 when its Phase 3 trial, SYNCHRONIZE-1, was published in theNew England Journal of Medicine. That changes how it should be read: it is no longer a dose-finding signal but a completed randomised Phase 3 result, in 725 adults with obesity and without diabetes, over 76 weeks.
| At 76 weeks | Survodutide 6.0 mg | Survodutide 3.6 mg | Placebo |
|---|---|---|---|
| Weight change, treatment-regimen | −13.0% | −12.2% | −5.4% |
| Weight change, efficacy estimand | −16.6% | — | — |
| Achieved ≥5% reduction | 71.9% | 72.6% | 46.3% |
Those first two rows are the clearest illustration on this page of why the estimand matters. They describe the same 725 people in the same trial. The 16.6% is the figure that appears in most coverage; the 13.0% is the primary analysis. A 3.6 percentage-point gap opens up purely from which convention gets quoted — roughly the whole difference between two adjacent compounds on this list.
Gastrointestinal symptoms were the most common adverse events, mostly mild to moderate, and no deaths were reported. Survodutide also carries separate interest in liver outcomes, which is where the glucagon component tends to show up.
Verdict: real Phase 3 evidence now, at a level below the leaders — and a useful reminder to check which estimand a headline is using.
6–8. The weaker options, and why they rank low
5-Amino-1MQ inhibits NNMT and reduced fat mass in obese mice. It is widely sold and heavily marketed, but human trial data does not exist yet — the enthusiasm is running well ahead of the evidence.
AOD-9604 is the clearest cautionary tale here. It reached human trials, the obesity program was discontinued in 2007, and no peer-reviewed paper reporting a benefit over placebo was ever published. It is still sold as a fat-loss peptide anyway.
MOTS-c has interesting mitochondrial and insulin-sensitivity effects in animals, and its popularity is rising fast, but human weight-loss data is not there. Worth watching, not worth ranking above the GLP-1 class.
Side effects across the class
The GLP-1 family shares a predictable profile: nausea, vomiting, diarrhea and constipation, concentrated around dose increases and usually easing at a stable dose. Slow titration is the main mitigation. Serious events are rarer — pancreatitis and gallbladder disease appear in trial safety data — and the compounds carry a contraindication for personal or family history of medullary thyroid carcinoma. Loss of lean mass alongside fat is a real consideration across all of them, which is why resistance training and protein intake come up in every serious discussion of these drugs.
Frequently asked questions
Which peptide produces the most weight loss in trials?
Retatrutide, though by a smaller margin than most coverage suggests. Comparing like with like — the analysis that counts every participant randomised — TRIUMPH-1 reported 25.0% at 80 weeks, against tirzepatide at 20.9% over 72 weeks, CagriSema at 20.4% over 68 weeks, semaglutide at 14.9% over 68 weeks and survodutide at 13.0% over 76 weeks. The widely quoted 30.3% for retatrutide is a different analysis of a selected subgroup, and comparing it to the others is not a fair comparison.
Are there non-prescription peptides for weight loss?
None are approved for weight loss without a prescription. Compounds like retatrutide, cagrilintide and 5-amino-1MQ are available only as research chemicals, which is a legal category for laboratory work rather than an over-the-counter alternative.
Do fat-loss peptides like AOD-9604 work?
AOD-9604, a fragment of human growth hormone, showed promise in mouse studies. It went into human trials, the obesity program was discontinued in 2007, and no peer-reviewed result showing benefit over placebo was ever published. The evidence behind it is not merely weaker than the GLP-1 class — for humans it is absent.
What happens when you stop taking a GLP-1 peptide?
Trial follow-up consistently shows substantial weight regain after discontinuation. In the semaglutide withdrawal extension, participants regained about two-thirds of what they had lost within a year of stopping.
The full GLP-1 research line — American Peptides
Retatrutide, tirzepatide, semaglutide, cagrilintide and blends — all with batch certificates of analysis. Coupon below for 10% off.
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Sources
- Jastreboff AM et al. Triple–Hormone-Receptor Agonist Retatrutide for Obesity — A Phase 2 Trial. New England Journal of Medicine, 2023;389(6):514–526. PubMed
- Eli Lilly. TRIUMPH-1 Phase 3 topline results, May 2026 (NCT05929066) and TRIUMPH-3 topline, July 2026 (NCT05882045). Trial design: Giblin K et al. Diabetes, Obesity and Metabolism, 2026;28(1):83–93. PubMed
- Jastreboff AM et al. Tirzepatide Once Weekly for the Treatment of Obesity (SURMOUNT-1). New England Journal of Medicine, 2022;387(3):205–216. PubMed
- Garvey WT et al. Coadministered Cagrilintide and Semaglutide in Adults with Overweight or Obesity (REDEFINE 1). New England Journal of Medicine, 2025;393(7):635–647. PubMed
- Wilding JPH et al. Once-Weekly Semaglutide in Adults with Overweight or Obesity (STEP-1). New England Journal of Medicine, 2021;384(11):989–1002. PubMed
- le Roux CW, Wharton S, Startseva E, et al. Survodutide Once Weekly for the Treatment of Adults with Obesity (SYNCHRONIZE-1). New England Journal of Medicine, published online 7 June 2026. PubMed · doi:10.1056/NEJMoa2600751
- le Roux CW et al. Glucagon and GLP-1 receptor dual agonist survodutide for obesity: a randomised, double-blind, placebo-controlled, dose-finding phase 2 trial. The Lancet Diabetes & Endocrinology, 2024;12(3):162–173. PubMed
- Novo Nordisk. REDEFINE 4 head-to-head results versus tirzepatide, February 2026. Company announcement · registry record NCT06131437. Not peer-reviewed; the non-inferiority margin was not disclosed.
- Wilding JPH et al. Weight regain and cardiometabolic effects after withdrawal of semaglutide: the STEP 1 trial extension. Diabetes, Obesity and Metabolism, 2022;24(8):1553–1564. PubMed
Related guides
- Best peptides for fat loss — the same compounds judged on body composition rather than total weight
- GLP-1 comparison chart: every agonist on one analysis
- Retatrutide: complete guide
- CagriSema: cagrilintide plus semaglutide
- Survodutide: the glucagon dual agonist
- Retatrutide dosage and titration chart
- Best place to buy retatrutide online: supplier comparison
- Peptide reconstitution calculator
- Are peptides safe?