Comparing Peptides for Muscle, Fat Loss and Recovery

Not all secretagogues work the same way

Lifters often treat growth hormone (GH) secretagogues as interchangeable. They aren't. They differ in how hard they push GH release and in what comes along with it, mainly appetite and stress hormones.

Two families usually get combined. Growth hormone releasing peptides (GHRPs) such as GHRP-6, GHRP-2, hexarelin and ipamorelin act on the ghrelin receptor and trigger a GH pulse from the pituitary. GHRH analogs such as CJC-1295 act on the receptor for growth hormone releasing hormone and make each pulse bigger. Because the receptors are separate, the pairing should release more GH than either alone, and nearly every community protocol uses it. As of October 2026, though, we found no controlled human trial of the popular Mod GRF 1-29 plus ipamorelin combination. Our guide to peptide stacking strategies covers the combination logic.

One caution: human studies of these peptides mostly measured GH and IGF-1 in blood, not strength or body composition in people who train. A bigger lab number isn't the same as more muscle, so most of what follows on results comes from user reports.

The GHRP spectrum: hunger, hormones and fading response

GHRP-6 is one of the first GHRPs. It's a ghrelin mimetic, and the side effect users mention most is strong hunger within about 15-30 minutes of an injection. Some lifters trying to bulk treat that as useful. People who are cutting usually don't.

GHRP-2 is usually described by users as producing at least as much GH as GHRP-6 with less hunger. In a 1998 swine study, GHRP-2 was more potent than GHRP-6 by dose but reached a slightly lower peak, and both raised ACTH and cortisol. In Japan it's approved only as a single-dose diagnostic test for GH deficiency.

Ipamorelin is chosen for selectivity. In that same study, it released GH about as well as GHRP-6 in rats and pigs but didn't raise ACTH or cortisol in pigs, even at more than 200 times the dose needed for GH release. Users commonly report little hunger at the 100-300 mcg doses they describe, which fits the animal data. Human evidence is thin: one IV dosing study in 48 healthy men, and a Phase 2 trial in 117 adults after abdominal surgery that missed its primary endpoint. That trial's ipamorelin group had more low potassium, high blood sugar and insomnia than placebo, plus two deaths; FDA reviewers said in 2024 it was unclear whether the deaths were drug-related.

Hexarelin is described by users as the strongest GHRP for raw GH release and the one whose effect fades fastest, with tolerance commonly reported after about four weeks. The one long human study is less alarming. In 12 healthy older adults given twice-daily subcutaneous hexarelin for 16 weeks, the GH response fell by about 45%, then returned to baseline within four weeks of stopping (Rahim and Shalet, 1998). Cortisol also rose after an IV dose in a small human study.

Rough comparison of GHRPs

These ratings are approximate, blending small human and animal studies with user reports. No human trial has compared all four.

CJC-1295 with DAC vs. without DAC

The name CJC-1295 covers two different products, and vials aren't always labeled clearly.

CJC-1295 with DAC. The drug affinity complex (DAC) lets the peptide bind to albumin in the blood, stretching its half-life to roughly 6-8 days. In two placebo-controlled trials in healthy adults, a single injection raised average GH 2- to 10-fold for six days or more and IGF-1 1.5- to 3-fold for 9-11 days (Teichman, 2006).

Forum guides, including an earlier version of this page, say this causes a constant "GH bleed" that wipes out the natural pulse pattern. The one human study that measured it found otherwise. Ionescu and Frohman (2006) sampled blood every 20 minutes overnight in healthy men before and one week after a dose of CJC-1295. The frequency and size of GH pulses didn't change. What rose was the level between pulses: trough GH went up about 7.5-fold, mean GH 46%, and IGF-1 45%. The pulses stayed, and the floor under them went up. Whether that higher floor changes results or side effects hasn't been tested.

Safety is the bigger open question. FDA's 2024 review reports injection-site reactions in about 70% of participants after one dose in the early trials. It also describes an unpublished Phase 2 trial in HIV lipodystrophy that stopped after a participant had a fatal heart attack 2 hours after his 11th weekly dose; the attending physician blamed undiagnosed coronary artery disease.

CJC-1295 without DAC (Mod GRF 1-29) is a modified form of the first 29 amino acids of GHRH, without the albumin-binding part. Users and vendors put its half-life at around 30 minutes, though we couldn't find a published human pharmacokinetic study to confirm that. Because it clears quickly, users pair each dose with a GHRP to boost one pulse at a time. It's the form most forum users actually describe, usually 100-300 mcg with ipamorelin at bedtime.

The old version of this page also called the DAC form "a recipe for receptor downregulation." We found no human study showing that. Preferring short, timed pulses is reasonable, but no outcome trial has compared the two forms. Our CJC-1295 profile covers both.

Specialized options: fat loss and recovery

HGH fragment and AOD-9604 for fat loss

HGH Fragment 176-191 is sold as the fat-burning tail end of the growth hormone molecule. The best-studied version is AOD-9604, a closely related fragment (amino acids 177-191 of human GH plus an extra tyrosine).

In obese mice, AOD-9604 reduced weight gain and increased fat oxidation and lipolysis without raising blood sugar, unlike full growth hormone (Heffernan, 2001). The human trials, all oral or IV, were less encouraging. The largest, OPTIONS, gave 536 adults with obesity oral doses of 0.25-1 mg daily for 24 weeks, and weight loss wasn't significantly different from placebo. Development for obesity stopped in 2007. FDA's 2024 review notes the sponsor reported no IGF-1 difference from placebo. As of October 2026, no human trial has tested the subcutaneous injections users describe.

So the old claim that the fragment leaves blood sugar and IGF-1 alone has some support. The claim that it's an effective fat-loss agent doesn't. Many users describe little or no change over 12 weeks; a minority report losing inches. Our AOD-9604 profile goes through the trials.

A GHRP plus GHRH stack raises GH and IGF-1 instead, and lifters on a cut use it hoping to keep muscle. No trial has tested that, and FDA's review notes that long-term GH treatment in people is generally linked to higher blood sugar and insulin resistance.

BPC-157 and TB-500 for recovery

Neither is a GH secretagogue. BPC-157 is a 15-amino-acid peptide derived from a stomach protein. In a 2003 rat study it sped healing of a cut Achilles tendon; angiogenesis (new blood vessel growth) is one proposed mechanism. A 2025 systematic review found that 35 of its 36 included studies were preclinical, with no clinical safety data. As of October 2026, human evidence is limited to a few small uncontrolled pilots.

TB-500 is usually sold as synthetic thymosin beta-4, but anti-doping chemists found that a TB-500 product contained a seven-amino-acid fragment (Ac-LKKTETQ), not the full protein. Human trials of full thymosin beta-4 say little about the fragment, which has no human data. Users commonly stack the two, calling BPC-157 the local healer and TB-500 the systemic one; that split comes from community guides, not studies.

What users report for each goal

These are community protocols, not tested regimens. No controlled human trial has studied these combinations.

• Mass: Users chasing size often pick GHRP-2 with Mod GRF 1-29, commonly reported at 100 mcg of each, 2-3 times a day (often after training and before bed), for 12-16 weeks. Some hardgainers use GHRP-6 for the hunger.
• Lean gains or recomposition: Ipamorelin with Mod GRF 1-29 is the usual choice, reported at 100-200 mcg of each, 2-3 times a day. Some forum guides describe runs of up to six months, far beyond ipamorelin's human safety data (single doses and up to 7 days of IV use, per FDA's 2024 review).
• Cutting: Users report HGH fragment 176-191 at 250-500 mcg once or twice daily on an empty stomach. The only human trials of the related AOD-9604 used oral doses of 0.25-1 mg daily and found no meaningful weight loss.
• Injury recovery: A common stack is BPC-157 at 250-500 mcg/day by subcutaneous injection near the injury, with TB-500 at about 2-2.5 mg twice weekly, a figure from vendor guidance. Some add ipamorelin at 100-200 mcg/day. No human trial has tested these doses or compared injection sites.

As of October 2026, WADA's 2026 Prohibited List places CJC-1295, ipamorelin, hexarelin, GHRP-2 and GHRP-6 under S2.2.4, AOD-9604 and hGH 176-191 under S2.2.3, BPC-157 under S0, and thymosin beta-4 derivatives including TB-500 under S2.3, so all are banned in tested sport. None is approved as a treatment in the US.

What we still don't know

• Whether the GH and IGF-1 increases from any of these peptides lead to more muscle or less fat in healthy adults who train. No trial has measured it.
• Whether the raised GH baseline from CJC-1295 with DAC acts differently from the short pulses of Mod GRF 1-29.
• How safe months of continuous use is. Our article on long-term effects of peptide use covers what's known.
• How much of the spread in user reports comes from product quality, since users can't easily check what's in a gray-market vial.