The best-researched peptide for losing fat while keeping muscle is tesamorelin (Egrifta). In its larger phase 3 trial, deep belly fat fell 15.2% on tesamorelin while it rose 5.0% on placebo (Falutz 2007, Human RCT, n=412), and a later analysis found larger trunk-muscle area in people who responded (Adrian 2019). It is FDA-approved only for excess abdominal fat in people with HIV-associated lipodystrophy. GLP-1 drugs remove far more fat but also lean mass, and most “muscle” peptides sold online have small trials, animal data only, or no approval.
| Peptide | US FDA and compounding | WADA (2026 List; 2027 List from 2027-01-01) |
|---|---|---|
| Tesamorelin | Approved as Egrifta (2010) for excess abdominal fat in HIV lipodystrophy; deemed a biologic (BLA) 2020-03-23 (Drugs@FDA) | Prohibited at all times, peptide hormones class (USADA) |
| Tirzepatide | Approved as Zepbound for chronic weight management (FDA) | Not prohibited; on the 2027 monitoring program (USADA) |
| Growth hormone | Use as an anti-aging agent is not FDA-approved and its distribution for that purpose is illegal in the US (Liu 2007) | Prohibited at all times, S2.2 (USADA) |
| Collagen peptides | Dietary supplement; FDA does not approve supplements before sale (FDA) | Not mentioned in USADA’s 2027 advisory (checked 2026-11-03) |
| CJC-1295, ipamorelin | Not approved; ipamorelin in Category 2 for 503B; CJC-1295 withdrawn from Category 2 (FDA) | Prohibited at all times, peptide hormones class (USADA) |
| Ibutamoren (MK-677) | Not approved; Category 2 for 503A and 503B (FDA) | Prohibited; listed under S1 in USADA’s 2027 advisory |
| AOD-9604 | Not approved; withdrawn from Category 2; phase 2b obesity program ended (FDA briefing) | Prohibited, S2.2 (FDA briefing) |
| BPC-157 | Not approved; withdrawn from Category 2; PCAC voted 8–6 (1 abstention) on 2026-07-23 to recommend 503A listing for ulcerative colitis; advisory, no FDA rule yet (FDA meeting) | Prohibited at all times, S0 (USADA) |
| MOTS-c | Not approved; withdrawn from Category 2; PCAC voted 7–5 (2 abstentions) to recommend 503A listing for obesity and osteoporosis; advisory, no FDA rule yet | Prohibited at all times, S4.4.1 (USADA) |
| Strongest evidence | Human RCTs: tesamorelin (n=412, n=404); tirzepatide DXA substudy (n=160) | From 2027, S0 names “peptides” in general |
| Human trials | Tesamorelin phase 3: NCT00123253; bimagrumab plus semaglutide: NCT05616013 | — |
| Last checked | 2026-11-03 | — |
Key points:
- In the SURMOUNT-1 body-scan substudy, about 75% of the weight lost on tirzepatide was fat and 25% was lean mass, the same split as on placebo.
- Collagen peptides are the only food-grade peptides here with randomized trials: taken alongside resistance training, they added fat-free mass beyond training alone.
- Ibutamoren (MK-677) raised fat-free mass by 1.1 kg in older adults, but strength and function did not change, and fasting glucose rose.
- No human study of ipamorelin and body composition was found on PubMed (searched 2026-11-03).
- From 1 January 2027, WADA’s S0 class names “peptides” in general as prohibited.
Best peptides for muscle and fat loss, ranked by evidence
This roundup orders each option by the strongest evidence that it changes body composition: approved drugs with phase 3 data first, then food-grade peptides and investigational drugs with human trials, then compounds tested only in animals. “Lean mass” and “fat-free mass” in these studies include muscle, organs and water, so a gain is not the same as new muscle. Numbers from different trials are cross-trial comparisons: populations, methods and durations differ, so they cannot be ranked directly against each other.
| Option | Best evidence | Key body-composition finding |
|---|---|---|
| Tesamorelin | Human RCT, phase 3 (n=412) | Visceral fat −15.2% vs +5.0% placebo (Falutz 2007) |
| Tirzepatide | Human RCT substudy (n=160) | Fat −33.9%, lean mass −10.9% at week 72 (Look 2025) |
| Growth hormone | Systematic review of RCTs (220 treated) | Fat −2.1 kg, lean +2.1 kg in healthy older adults (Liu 2007) |
| Collagen peptides | Human RCT (n=53) | Fat-free mass +4.2 kg vs +2.9 kg with training (Zdzieblik 2015) |
| Ibutamoren (MK-677) | Human RCT (n=65) | Fat-free mass +1.1 kg vs −0.5 kg; fat unchanged (Nass 2008) |
| Bimagrumab (antibody) | Human RCT, phase 2 (n=75) | Fat −20.5%, lean +3.6% (Heymsfield 2021) |
| BPC-157 | Animal (rats) | Faster healing of a cut thigh muscle (Staresinic 2006) |
| MOTS-c | Animal (mice) | Better physical performance at all ages tested (Reynolds 2021) |
Tier 1: tesamorelin, benefits for deep belly fat and trunk muscle
Tesamorelin is a growth hormone-releasing hormone (GHRH) analogue: it prompts the pituitary to release more of the body’s own growth hormone. Its phase 3 results are the strongest peptide evidence found for cutting deep belly fat without lowering body weight. In the first phase 3 trial, 412 adults with HIV and abdominal fat build-up took tesamorelin or placebo for 26 weeks; visceral fat, the fat packed around the organs, fell 15.2% on tesamorelin and rose 5.0% on placebo, and triglycerides fell (Falutz 2007, Human RCT). A second trial of 404 patients found a 10.9% drop versus 0.6%, with smaller waists and no change in fat under the skin of the limbs (Falutz 2010, Human RCT).
The muscle signal is encouraging but secondary. An exploratory re-analysis of CT scans from both trials found larger lean area in all four trunk muscle groups in 193 responders compared with 148 placebo patients (Adrian 2019, secondary analysis of RCTs); it included only people whose visceral fat fell at least 8%. The Egrifta label states it is not indicated for weight loss, calling its effect weight neutral, and lists joint pain, injection-site reactions, swelling, muscle pain and possible glucose intolerance. The tesamorelin vs CJC-1295 + ipamorelin comparison covers this pair in depth.
Tier 1: GLP-1 drugs, large fat loss with some lean loss
GLP-1 drugs such as tirzepatide (Zepbound) are peptides too, and for fat loss alone they have the largest effects of anything here. In a substudy of SURMOUNT-1, 160 adults had full-body DXA scans: over 72 weeks, fat mass fell 33.9% on tirzepatide versus 8.2% on placebo, while lean mass fell 10.9% versus 2.6% (Look 2025, Human RCT substudy). Roughly three quarters of the weight lost was fat and one quarter lean mass. Add-on drugs meant to spare muscle, such as bimagrumab (below), are now being tested alongside GLP-1 drugs. FDA approved tirzepatide as Zepbound for adults with obesity, or overweight with a weight-related condition, and notes thyroid C-cell tumors in rats with unknown relevance to humans. Our weight-loss peptide roundup compares the whole class.
Growth hormone itself: real changes, real side effects
Growth hormone is the hormone that GH-releasing peptides aim to raise, so its own trial results are a useful reference point. A systematic review of randomized trials in healthy older adults (18 study populations, 220 people on GH) found fat mass down 2.1 kg and lean mass up 2.1 kg, with no change in body weight (Liu 2007, systematic review). The same review found more swelling, joint pain, carpal tunnel syndrome and breast enlargement in men, and a trend toward diabetes, and concluded GH cannot be recommended as an anti-aging therapy.
Tier 2: collagen peptides with resistance training
Collagen peptides are a food protein with several randomized trials showing benefits for body composition when combined with strength training. In 53 older men with sarcopenia (age-related muscle loss) doing 12 weeks of supervised training, those taking collagen peptides gained 4.2 kg of fat-free mass versus 2.9 kg on placebo, lost 5.4 kg of fat versus 3.5 kg, and gained more leg strength (Zdzieblik 2015, Human RCT); one author worked for a collagen research institute. In 77 premenopausal women, collagen plus training raised fat-free mass and lowered fat more than training alone (Jendricke 2019, Human RCT). In 25 young men, fat-free mass rose more with collagen, but fat mass did not differ (Oertzen-Hagemann 2019, Human RCT). The trials are small and short, and every group trained. As a supplement, collagen is not reviewed by FDA for safety or effectiveness before sale (FDA).
Tier 2: growth hormone secretagogues (sermorelin, CJC-1295, ipamorelin, MK-677)
These compounds push the pituitary to release growth hormone. Their human body-composition evidence is thin:
- Sermorelin-type GHRH: in 19 adults aged 55–71 given a GHRH(1-29) analogue for 16 weeks, lean body mass rose in men only, with no other body-composition change (Khorram 1997, single-blind controlled trial).
- CJC-1295: in two dose-ranging trials in healthy adults, one injection raised growth hormone 2- to 10-fold for 6 days or more and IGF-1 1.5- to 3-fold (Teichman 2006, Human RCT); body composition was not measured. FDA lists increased heart rate and a systemic vasodilatory reaction among serious adverse events (FDA).
- Ipamorelin: a PubMed search for human studies of ipamorelin and body composition, lean mass or fat mass returned no results (searched 2026-11-03). FDA cites serious adverse events, including death, when it was given intravenously for gut motility.
- Ibutamoren (MK-677): an oral, non-peptide ghrelin mimetic. In a randomized trial of 65 adults aged 60–81, fat-free mass rose 1.1 kg versus a 0.5 kg fall on placebo, but fat mass, visceral fat, strength and function did not change, fasting glucose rose and insulin sensitivity fell (Nass 2008, Human RCT). FDA notes a hip-fracture trial stopped early for a possible heart-failure signal.
The MK-677 vs ipamorelin page compares the last two side by side.
Tier 2: AOD-9604 and bimagrumab, two different outcomes
AOD-9604 is a fragment of growth hormone that was developed as an obesity drug, but its human program stopped: the developer announced in February 2007 that phase 2b results did not support commercial viability for obesity, and FDA’s 2024 review found “a lack of evidence to support the effectiveness” for obesity (FDA briefing).
Bimagrumab is an antibody, not a peptide, but it has the clearest trial data found for losing fat while gaining lean mass. It blocks activin type II receptors, which normally limit muscle growth. In 75 adults with type 2 diabetes and obesity, 48 weeks of infusions cut fat mass 20.5% and raised lean mass 3.6%, versus almost no change on placebo (Heymsfield 2021, Human RCT, phase 2). In the 507-person BELIEVE trial, weight fell 17.8 kg with high-dose bimagrumab plus semaglutide 2.4 mg, 14.2 kg with semaglutide alone and 3.3 kg on placebo; muscle spasms, diarrhea and acne were common (Heymsfield 2026, Human RCT, phase 2). It is investigational and not obtainable legally outside trials.
Tier 3: animal-only findings (BPC-157, MOTS-c)
In rats with a fully cut quadriceps, daily BPC-157 improved muscle healing, strength at failure and walking over 72 days (Staresinic 2006, Animal). That is an injury-healing finding, not muscle growth or fat loss, and no registered BPC-157 trial measures either; one rotator-cuff surgery trial is not yet recruiting (NCT07803250, checked 2026-11-03). In mice, MOTS-c improved physical performance in young, middle-aged and old animals (Reynolds 2021, Animal), but FDA reports no human exposure data for MOTS-c products. The MOTS-c vs 5-Amino-1MQ comparison covers its metabolic data.
Which has more evidence for which goal?
Tesamorelin has the most evidence for reducing deep belly fat without losing weight overall, in people with HIV. Tirzepatide and other GLP-1 drugs have the most evidence for total fat loss, with a measured lean-mass cost. Collagen peptides have the most evidence for adding fat-free mass, but only alongside resistance training. Growth hormone and MK-677 shift lean mass in older adults without proven strength gains. For muscle preserved during GLP-1 weight loss, bimagrumab has the only phase 2 data. A clinician is the person to decide whether any of these fits a specific situation.
Can they be combined?
A PubMed search for tesamorelin, sermorelin, ipamorelin or CJC-1295 with semaglutide or tirzepatide returned three reviews and no trials. No controlled human study of these combinations was found on PubMed or ClinicalTrials.gov (searched 2026-11-03). The only tested combination for keeping muscle during GLP-1 weight loss is bimagrumab plus semaglutide in BELIEVE.
Safety and regulatory status
Only tesamorelin and the GLP-1 drugs are approved for a body-composition use, and each for a defined group. Tesamorelin can cause glucose intolerance, joint pain and swelling (Egrifta label). FDA keeps ibutamoren in Category 2 for both 503A and 503B compounding over heart-failure risk and ipamorelin in Category 2 for 503B; CJC-1295, AOD-9604, BPC-157 and MOTS-c were withdrawn from Category 2 by their nominators, which does not make them approved (FDA). The July 2026 advisory votes on BPC-157 and MOTS-c are recommendations, not FDA rules (FDA meeting).
For athletes, tesamorelin, CJC-1295 and ipamorelin are prohibited at all times (USADA), and from 2027 WADA’s S0 class names peptides in general (USADA 2027). GLP-1 drugs are not prohibited but are monitored (USADA GLP-1). Anyone who suspects a side effect from these peptides or any other drug or product can report it to the FDA through MedWatch.
What users report
What follows are unverified self-reports from people who usually bought unregulated products; they are not evidence. People who post about muscle and fat-loss peptides on forums, YouTube and social media most often describe GH-releasing stacks such as CJC-1295 with ipamorelin, or MK-677, and say they notice better sleep, fuller-looking muscles and slightly lower body fat over several weeks to a few months. MK-677 users commonly complain of strong hunger, water retention, puffy hands and lethargy, and some report higher blood sugar on home tests. Recurring complaints about injected peptides include site redness, flushing, tingling or numb hands, and no visible effect at all. A frequent argument is whether any change comes from the peptide or from the diet and training people start at the same time. Product quality is a constant worry, with posters disputing whether vials contain what the label says. People who use GLP-1 drugs often say they worry about losing muscle and ask whether a peptide can prevent it, a question the trials above have not answered for any peptide.
Frequently asked questions
What are the best peptides for body recomposition?
The best-researched option is tesamorelin: in a 412-person trial, visceral fat fell 15.2% on it and rose 5.0% on placebo, with trunk-muscle gains in responders; it is approved only for HIV lipodystrophy. Collagen peptides added fat-free mass in small trials, but only alongside resistance training (Zdzieblik 2015). No peptide has been shown to build muscle and burn fat in healthy adults without training.
Which is better, sermorelin or ipamorelin?
Neither has strong body-composition data. A 16-week trial of a sermorelin-type GHRH analogue raised lean mass in 9 older men but not in 10 women (Khorram 1997). For ipamorelin, no human body-composition study was found on PubMed (searched 2026-11-03). Both are prohibited in sport, and the three-way comparison sets out their evidence.
Do GLP-1 drugs make you lose muscle?
They cause some lean-mass loss along with fat. In the SURMOUNT-1 scan substudy, tirzepatide cut fat mass 33.9% and lean mass 10.9% over 72 weeks, about a 3-to-1 split that matched placebo (Look 2025). Lean mass includes organs and water, not only muscle. Trials are now testing add-ons such as bimagrumab to protect muscle.
Are peptides steroids?
No. Anabolic steroids are synthetic relatives of testosterone, while peptides are short chains of amino acids that usually act on specific receptors, such as the GHRH receptor targeted by tesamorelin. Many muscle peptides are still banned in sport: USADA lists tesamorelin, CJC-1295 and ipamorelin as prohibited at all times (USADA). Our peptides vs steroids vs SARMs guide compares all three.
References
- Falutz J, et al. (2007). Metabolic effects of a growth hormone-releasing factor in patients with HIV. N Engl J Med. PubMed 18057338
- Falutz J, et al. (2010). Effects of tesamorelin in HIV-infected patients with abdominal fat accumulation. J Acquir Immune Defic Syndr. PubMed 20101189
- Adrian S, et al. (2019). Tesamorelin decreases muscle fat and increases muscle area in adults with HIV. J Frailty Aging. PubMed 31237318
- US FDA. Egrifta (tesamorelin) prescribing information, 2010. FDA label
- US FDA. Drugs@FDA: BLA 022505, Egrifta. Drugs@FDA
- Look M, et al. (2025). Body composition changes during weight reduction with tirzepatide in the SURMOUNT-1 study. Diabetes Obes Metab. PubMed 39996356
- US FDA (2023). FDA approves new medication for chronic weight management. FDA
- Liu H, et al. (2007). Systematic review: the safety and efficacy of growth hormone in the healthy elderly. Ann Intern Med. PubMed 17227934
- Zdzieblik D, et al. (2015). Collagen peptide supplementation in combination with resistance training in elderly sarcopenic men. Br J Nutr. PubMed 26353786
- Jendricke P, et al. (2019). Specific collagen peptides with resistance training in premenopausal women. Nutrients. PubMed 31010031
- Oertzen-Hagemann V, et al. (2019). Hypertrophy resistance training with collagen peptide supplementation in recreationally active men. Nutrients. PubMed 31091754
- US FDA. FDA 101: Dietary supplements. FDA
- Khorram O, et al. (1997). Endocrine and metabolic effects of long-term administration of a GHRH analog in age-advanced men and women. J Clin Endocrinol Metab. PubMed 9141536
- Teichman SL, et al. (2006). Prolonged stimulation of GH and IGF-I secretion by CJC-1295 in healthy adults. J Clin Endocrinol Metab. PubMed 16352683
- PubMed search: ipamorelin and body composition in humans, run 2026-11-03. PubMed
- Nass R, et al. (2008). Effects of an oral ghrelin mimetic on body composition in healthy older adults. Ann Intern Med. PubMed 18981485
- US FDA. Certain bulk drug substances for use in compounding that may present significant safety risks (Category 2). FDA
- US FDA (2024). Briefing document: AOD-9604, Pharmacy Compounding Advisory Committee. FDA
- Heymsfield SB, et al. (2021). Effect of bimagrumab vs placebo on body fat mass in adults with type 2 diabetes and obesity. JAMA Netw Open. PubMed 33439265
- Heymsfield SB, et al. (2026). Bimagrumab plus semaglutide for obesity: a randomized phase 2 trial (BELIEVE). Nat Med. PubMed 41772149
- ClinicalTrials.gov. NCT05616013: Bimagrumab and semaglutide in adults with overweight or obesity. ClinicalTrials.gov
- ClinicalTrials.gov. NCT00123253: TH9507 (tesamorelin) in HIV-associated lipodystrophy. ClinicalTrials.gov
- Staresinic M, et al. (2006). Effective therapy of transected quadriceps muscle in rat: BPC 157. J Orthop Res. PubMed 16609979
- ClinicalTrials.gov. NCT07803250: BPC-157 after rotator cuff repair. ClinicalTrials.gov
- Reynolds JC, et al. (2021). MOTS-c is an exercise-induced regulator of age-dependent physical decline and muscle homeostasis. Nat Commun. PubMed 33473109
- US FDA. July 23–24, 2026 meeting of the Pharmacy Compounding Advisory Committee. FDA
- USADA. Athlete advisory: 2027 Prohibited List. USADA
- USADA. Anthony McCauley accepts doping sanction. USADA
- USADA. 6 things to know about peptide hormones and releasing factors. USADA
- USADA. What is MOTS-c? USADA
- USADA. #AskUSADA: What is a non-approved substance and why are they prohibited? USADA
- USADA. Weight loss drugs: what athletes need to know about GLP-1s. USADA
Change log
2026-11-03: first published after review by the editorial team.