Fat metabolism research using peptides spans several different mechanistic categories: GH secretagogues that increase growth hormone pulse amplitude, direct lipolytic fragments, and the newer GLP-1/GIP/glucagon receptor agonist class. Each works differently, each has a distinct evidence base, and each carries different COA documentation requirements.
This guide covers the four most researched peptide classes in the fat metabolism and body composition literature as of 2026.
For research and educational purposes only. Not medical advice. These compounds are not FDA-approved for human use.
AOD-9604: The Lipolytic Fragment
AOD-9604 is a synthetic fragment of human growth hormone, specifically the C-terminal amino acids 176–191 with a tyrosine residue added at the N-terminus. It was developed as a lipolytic peptide that retains the fat-metabolism activity of full-length hGH without the growth-promoting or insulin-like effects of the full protein.
Research findings center on its ability to stimulate lipolysis (fat breakdown) and inhibit lipogenesis (new fat creation) in adipose tissue. AOD-9604 activates beta-3 adrenergic receptors (the same receptor class activated by catecholamines during lipolysis) without binding to the hGH receptor or affecting IGF-1 levels.
Clinical research on AOD-9604 progressed to Phase IIb/III trials (under the name Tyr-hGH fragment 176-191) for obesity treatment. While it did not achieve the efficacy threshold required for approval, the trials produced a substantial safety and pharmacokinetic dataset that makes it one of the better-characterized fragments in the research peptide space.
COA requirements: LC-MS identity (~1817 Da), HPLC purity 95%+, endotoxin testing for injectable applications. The listed research text specifies confirming the tyrosine addition at the N-terminus is reflected in the theoretical mass on the COA.
CJC-1295 + Ipamorelin: The Classic GH Secretagogue Stack
CJC-1295 (with or without DAC) is a synthetic analogue of GHRH (growth hormone releasing hormone) that stimulates the pituitary to release growth hormone. Ipamorelin is a selective GH secretagogue receptor agonist (ghrelin mimetic) that amplifies GH pulses without significantly affecting cortisol, prolactin, or ACTH.
The combination is widely studied because the two compounds work at different points in the same pathway: CJC-1295 increases the amplitude of GH pulses by extending the GHRH signal, while Ipamorelin enhances the pituitary response through a separate receptor. Combined, they produce larger GH pulses than either compound alone while maintaining the selectivity advantages of Ipamorelin.
Growth hormone's downstream effects on fat metabolism are well-documented: increased lipolysis in adipose tissue, mobilization of free fatty acids, and a shift in substrate utilization away from glucose and toward fat. These effects are mediated both directly and through IGF-1 produced in response to GH.
COA requirements for CJC-1295 (no DAC): LC-MS identity (~3367 Da), HPLC purity 98%+. For CJC-1295 with DAC: ~3647 Da. Ipamorelin: LC-MS identity (~711 Da), HPLC purity 98%+. For both in injectable research: endotoxin testing required.
Retatrutide: The Triple Agonist
Retatrutide (LY3437943) is a once-weekly injectable triple agonist targeting the GLP-1, GIP, and glucagon receptors simultaneously. It was developed by Eli Lilly and completed Phase II clinical trials in 2023, showing weight reductions of up to 24.2% body weight at 48 weeks, the largest weight reduction reported in a Phase II peptide trial to date.
The triple agonism differentiates it mechanistically from semaglutide and tirzepatide. The added glucagon receptor activity increases energy expenditure and hepatic fat oxidation, which may explain the larger magnitude of weight loss compared to GLP-1 or GLP-1/GIP dual agonists. Phase III trials (TRIUMPH program) are ongoing.
Retatrutide represents the cutting edge of peptide-based metabolic research. For research use, it is significantly more structurally complex than most other peptides in this category: a 39-amino-acid sequence with fatty acid modification for extended half-life.
COA requirements: Stringent. LC-MS identity with observed mass, HPLC purity 98%+, net peptide content analysis (the fatty acid modification adds mass that must be accounted for), endotoxin testing, and sterility documentation for injectable applications. The structural complexity means mass discrepancies are more easily hidden: require the observed mass on the COA, not just a pass/fail.
Tesamorelin: The Most Clinically Validated GH Secretagogue
Tesamorelin is a synthetic GHRH analogue with a trans-3-hexenoic acid modification that extends its half-life. It is the only GHRH analogue with FDA approval, for HIV-associated lipodystrophy (excess visceral fat in HIV patients on antiretroviral therapy), making it the most clinically studied peptide in the GH secretagogue class with a defined regulatory track record.
Multiple randomized controlled trials have demonstrated tesamorelin's effects on visceral adipose tissue reduction, IGF-1 normalization, and lipid profile improvement. The clinical dataset is substantially deeper than for most peptides in the research space, though the approved indication is a specific medical condition rather than general fat loss.
COA requirements: LC-MS identity (~5136 Da including the hexenoic acid modification), HPLC purity 98%+, endotoxin and sterility testing for injectable applications. The listed research text specifies confirming the fatty acid modification is reflected in the theoretical mass on the COA.
Comparison: Fat Metabolism Peptides
| Compound | Mechanism | Clinical Stage | Expected Mass | Purity Floor |
|---|---|---|---|---|
| AOD-9604 | Beta-3 AR agonism, lipolysis | Phase IIb/III (completed) | ~1817 Da | 95% |
| CJC-1295 + Ipamorelin | GHRH + ghrelin receptor | Research stage | ~3367 + ~711 Da | 98% |
| Retatrutide | GLP-1/GIP/Glucagon triple agonist | Phase III ongoing | Complex (~5800+ Da) | 98%+ |
| Tesamorelin | GHRH analogue | FDA approved (HIV indication) | ~5136 Da | 98% |
COA Verification for Fat Metabolism Peptides
For longer, more structurally complex peptides (Retatrutide, Tesamorelin), mass spectrometry identity confirmation is especially critical. It is easier for a mass discrepancy to be obscured in a pass/fail COA when the expected mass is in the thousands of Daltons and the structure includes modifications. The specific observed mass must always be required on the COA and compared against the theoretical value.
The listed research text specifies using our COA Verification Guide before ordering. All four compound classes are available from vendors listed in the RUO Codes directory. Browse vendors to compare testing tiers and active coupon codes.