Peptides for Body Composition

Across the 19 peptides covered on this page, evidence for body composition effects spans a wide spectrum. At the strongest end, tesamorelin and HGH 191AA (somatropin) hold FDA approvals for specific indications—HIV-associated lipodystrophy and growth hormone deficiency, respectively—supported by Phase 3 trials. L-carnitine injectable sits in the next tier, with meaningful human clinical data for IV use in carnitine deficiency and dialysis, though subcutaneous administration for fat oxidation remains off-label. Sermorelin, GHRP-2, MK-677, and hexarelin have Phase I–II data, often from GH-deficient populations or diagnostic settings. AICAR and ACE-031 represent early human or mixed evidence, while compounds like ipamorelin and CJC-1295 are supported mainly by preclinical models. The ranking weighs regulatory status, trial design, sample size, and consistency of body composition outcomes. Readers should note that FDA approval applies only to the branded products and labeled indications, not to research-grade peptides.

Tesamorelin (tesamorelin acetate) is a synthetic 44-amino-acid analog of human growth hormone-releasing hormone (GHRH) and currently the only FDA-approved medication for reducing excess abdominal fat in HIV-infected adults with lipodystrophy, marketed as Egrifta. It works by stimulating endogenous growth hormone and IGF-1 production. In March 2025, the FDA approved Egrifta WR, a weekly-reconstitution formulation. Phase 3 trials demonstrated significant reductions in visceral adipose tissue over 26 weeks, alongside a generally well-tolerated safety profile. These trials also reported increases in skeletal muscle area and density. Evidence Rating: A. Category: Growth Hormone Secretagogue. The approval is specific to HIV-associated lipodystrophy; body composition effects in other populations have not been established by pivotal trials. Research continues to explore the mechanism of GHRH analogs, but tesamorelin's clinical data remain the most robust among peptides in this category.

HGH 191AA refers to recombinant human growth hormone (somatropin), a 191-amino-acid, single-chain polypeptide with a molecular weight of approximately 22,124 g/mol. Its sequence is identical to endogenous pituitary growth hormone. The FDA has approved somatropin for growth hormone deficiency in children and adults, Turner syndrome, chronic renal insufficiency, Prader-Willi syndrome, and HIV-associated wasting. In peptide research circles, '191AA' distinguishes legitimate somatropin from the older 192-amino-acid variant, somatrem, which contained an extra methionine and exhibited higher immunogenicity. Evidence Rating: A. Category: Growth Hormone. Clinical trials in GH-deficient adults show improvements in body composition, including lean mass and fat distribution. However, these findings are specific to diagnosed deficiency states; the evidence does not extend to non-deficient populations. As a recombinant protein, somatropin is regulated as a biologic, and research-grade material is not FDA-approved for any indication.

Injectable L-carnitine is a naturally occurring amino acid derivative (molecular weight ~161.2 g/mol) that facilitates the transport of long-chain fatty acids across the mitochondrial inner membrane for beta-oxidation. Oral L-carnitine has poor bioavailability, reported at 5–18%, whereas subcutaneous injection achieves near-100% bioavailability, making it a more efficient delivery method in research settings. The FDA has approved an intravenous form (Carnitor) for primary carnitine deficiency and for dialysis patients. Subcutaneous use for fat oxidation enhancement is off-label and is commonly encountered in metabolic optimization clinics. Evidence Rating: B. Category: Metabolic / Fat Oxidation. Key claims from studies include enhanced fat oxidation during exercise and improved exercise performance. However, much of the human data on body composition comes from IV or oral routes, and the evidence for subcutaneous administration in this context remains less robust. Research limitations include small sample sizes and variability in exercise protocols.

Sermorelin is a synthetic 29-amino-acid peptide (molecular weight ~3357.9 g/mol) corresponding to the first 29 amino acids of naturally occurring growth hormone-releasing hormone (GHRH). It was previously FDA-approved as Geref for the diagnosis and treatment of growth hormone deficiency in children, but the product was voluntarily discontinued for commercial reasons. The FDA confirmed in 2013 that it was not withdrawn for safety reasons. Sermorelin preserves the body's natural GH feedback loop via somatostatin, a mechanism proposed to offer safety advantages over exogenous HGH. Evidence Rating: C. Category: Growth Hormone Secretagogue. The 1997 JCEM trial remains the most substantial evidence for its effects in adults, demonstrating improvements in IGF-1, body composition, and well-being over 5 months. However, this trial is older, and larger contemporary studies are lacking. Sermorelin is not currently FDA-approved, and it is not marketed as a therapeutic in the United States.

GHRP-2 (pralmorelin) is a synthetic hexapeptide growth hormone secretagogue with the sequence D-Ala-D-2-Nal-Ala-Trp-D-Phe-Lys-NH2 and a molecular weight of approximately 817.97 g/mol. It stimulates potent, dose-dependent GH release via the ghrelin receptor (GHS-R). Compared with GHRP-6, it is considered more potent and to cause less appetite stimulation. Evidence Rating: C. Category: Growth Hormone Secretagogue. In Japan, pralmorelin is approved as a diagnostic agent for GH deficiency. Clinical studies have used it in GH-deficient children for 8–24 months, with maintained efficacy on growth velocity. Clinical studies show a placebo-like safety profile at therapeutic doses. However, GHRP-2 is not FDA-approved for any indication in the United States, and its use for body composition remains investigational. Research limitations include a focus on diagnostic and pediatric GH deficiency contexts, with limited data on body composition outcomes in healthy adults.

Evidence Rating: C · Category: Growth Hormone Secretagogue

MK-677 (ibutamoren) is the outlier in this category on two counts: it is non-peptide and orally active. It reaches the same target as the injectable growth hormone secretagogues — the ghrelin receptor, GHS-R1a — but through a small molecule, and studies indicate that a single dose sustains elevated GH and IGF-1 for up to 24 hours. That profile stands in contrast to the pulsatile secretion the endogenous somatotropic axis produces.

Human trials have been conducted in growth hormone deficiency, muscle wasting, bone density and sleep quality, yet no regulatory approval exists for any indication. The breadth of that list can be misleading: body-composition endpoints specifically are supported by a narrower set of controlled data than the range of studied populations suggests, and the persistence of IGF-1 elevation between doses leaves questions about continuous receptor stimulation unresolved in the published literature. As with other GHS-R1a agonists, appetite effects are mechanistically expected and have been noted in trial reporting.

Evidence Rating: C · Category: Growth Hormone Secretagogue

Among synthetic hexapeptide growth hormone secretagogues, hexarelin elicits one of the largest acute GH responses described in the clinical literature, and its activity at the ghrelin receptor (GHS-R1a) supplements rather than duplicates GHRH signalling. Potency carries a cost, however: receptor desensitisation develops comparatively rapidly, and studies report attenuated GH responses within a shorter interval than is seen with milder secretagogues such as ipamorelin — a finding that explains why research protocols in the literature tend to be brief.

A second line of investigation has little to do with growth hormone at all. Cardioprotective effects have been described in models of cardiac ischaemia, and because they appear to persist independently of GH release, they are generally attributed to direct receptor-mediated activity on cardiac tissue. That distinction matters for evidence appraisal: the cardioprotective claims rest largely on preclinical work, while the GH data derive from acute-dose human studies. The Phase I–II designation reflects early human exposure rather than demonstrated body-composition benefit, and hexarelin holds no FDA approval for any indication.

Evidence Rating: C · Category: Metabolic / Exercise Mimetic

AICAR (5-aminoimidazole-4-carboxamide ribonucleoside, ~258.2 g/mol) is a cell-permeable nucleoside analogue that is phosphorylated intracellularly to ZMP, the intermediate that directly activates AMP-activated protein kinase. Because AMPK sits at the centre of the cellular response to energy deficit, pharmacological activation reproduces several adaptations ordinarily triggered by muscular contraction — enhanced glucose uptake, increased fatty acid oxidation, mitochondrial biogenesis and improved insulin sensitivity — without exercise being performed.

The exercise-mimetic framing is the source of both the research interest and the interpretive limits. The strongest controlled human data come from Phase II/III trials in cardiac ischaemia, a cardiovascular indication rather than a body-composition one, and extrapolating those results to lean-mass or fat-mass outcomes in healthy populations is not supported by the trial record. WADA classification as a metabolic modulator further constrains human research in athletic settings. Evidence for body-composition effects therefore rests primarily on mechanistic and preclinical work, and the compound is not approved for any therapeutic use.

Evidence Rating: C · Category: Muscle Growth / Research

ACE-031 approaches muscle regulation from entirely outside the growth hormone axis. It is a soluble ActRIIB ectodomain fused to a human IgG1 Fc domain (~90,000 g/mol), designed as a ligand trap: circulating myostatin, activin, GDF-11 and related TGF-beta superfamily ligands bind the receptor fragment instead of their endogenous receptors, removing a brake on muscle growth.

Acceleron Pharma advanced the molecule through Phase I and Phase II trials in Duchenne muscular dystrophy, a population selected because myostatin-pathway inhibition offered a mechanistically rational route to preserving lean mass. Development was discontinued after vascular safety signals emerged — epistaxis and telangiectasias among participants — an outcome that illustrates how a clean preclinical hypertrophy profile can fail to translate when the same pathway is engaged chronically in humans. For body-composition research, ACE-031 functions best as a case study in pathway validity versus therapeutic index: the target appears real, but systemic ligand traps of this class carry liabilities that narrow the usable window. No regulatory approval exists for any indication.

Evidence Rating: C · Category: Growth Hormone

CJC-1295 with DAC is a GHRH analogue carrying a lysine-linked maleimidopropionic acid moiety that forms a covalent bond with circulating albumin after administration. The Drug Affinity Complex is what separates this compound from the unmodified analogue: native GHRH has a half-life measured in minutes, whereas albumin conjugation extends it to roughly 8 days, and study designs in the literature have accordingly used once- or twice-weekly administration.

The same modification that produces that durability also shapes pharmacodynamics. CJC-1295 without DAC preserves a GH release pattern closer to endogenous pulsatility; the DAC form yields sustained, relatively flat GH elevation. Whether that distinction alters downstream outcomes is an open question, and it illustrates the trade-off between convenience and physiological fidelity that runs through this category. Human data remain Phase I–II in scope — pharmacokinetic and endocrine endpoints rather than body-composition endpoints — and the material is a research compound with no FDA approval.

Evidence Rating: D · Category: Growth Hormone Secretagogue

Ipamorelin (C38H49N9O5, ~711.86 g/mol) is a synthetic pentapeptide growth hormone secretagogue distinguished less by potency than by selectivity. The pharmacological literature characterises it as releasing GH in a pulsatile fashion from the pituitary while producing minimal measurable effect on cortisol, prolactin or appetite — the off-target hormonal activity that complicates interpretation of results obtained with less selective GHRPs.

That selectivity underlies its frequent appearance in body-composition and recovery discussions. The evidence supporting those applications is the weakest on this page, which is why the rating is D: characterisation is largely preclinical and mechanistic, human trial data are sparse, and no FDA approval exists for any indication. Receptor selectivity does not by itself establish benefit for any body-composition endpoint, and the tolerability and desensitisation profile reported for ipamorelin has not been characterised in long-duration human studies. It remains a laboratory research compound.

CJC-1295 originated at ConjuChem Technologies as a GHRH analogue bearing a Drug Affinity Complex, an albumin-binding moiety intended to prolong circulation time. The same peptide backbone without DAC — commonly designated Mod GRF 1-29 — is the form this section covers, and it is treated as a distinct research material from the DAC conjugate profiled elsewhere on this page. Half-life separates the two sharply: roughly 30 minutes for the DAC-free analogue against a reported 5.8–8.1 days for the conjugated version.

Human data on the unconjugated peptide is thin. Two 2006 randomized, placebo-controlled, double-blind trials (Teichman et al.) enrolled healthy adults aged 21–61 and reported dose-dependent growth hormone increases of 2- to 10-fold and IGF-1 increases of 1.5- to 3-fold. Those are hormonal endpoints captured over a short observation window, and the D rating reflects that body-composition change has not been measured as a primary outcome in that literature. For regulatory context, tesamorelin (Egrifta) is the GHRH analogue that holds FDA approval, for HIV-associated lipodystrophy — an approval that does not extend to CJC-1295 or to any research-grade analogue.

Commentary on the analogue frequently describes its pulsatile release, absent DAC, as closer to endogenous GHRH signalling than the sustained exposure produced by the conjugate, though head-to-head comparisons of the two forms remain absent from the published record.