At a glance

What is AOD-9604?

AOD-9604 is a synthetic peptide based on the C-terminal (tail) region of human growth hormone, with an added amino acid to stabilize it. The name stands for "Advanced Obesity Drug," reflecting its original development by Metabolic Pharmaceuticals as a weight-loss candidate. It is sold on the wellness and "research peptide" market for fat loss, often under the broader "hGH fragment 176-191" label, though it is a modified version of that fragment rather than the bare fragment.

How does it work?

The proposed idea is that the tail region of growth hormone carries its fat-burning activity without the rest of the hormone's effects. In animal and cell studies, AOD-9604 increased both fat breakdown and fat oxidation while it reduced fat storage, reportedly without activating the growth hormone receptor or causing growth or insulin-resistance effects. In rodents, it also raised markers of fat metabolism (here¹ and here²). These are animal and laboratory findings; the human trials below tested whether they translate.

Is it FDA-approved?

No. AOD-9604's regulatory status covers several points:

• Not approved by the FDA for any use, and never reached market as a drug
• A history that includes an attempt to position it as a food/supplement ingredient
• Not an approved compounding substance
• Prohibited at all times in sport under the WADA list, which covers growth hormone fragments including AOD-9604

What does the research show?

Unusually for a wellness peptide, AOD-9604 was tested in real human trials, and they were negative. A 24-week Phase 2b obesity trial of 536 participants did not produce significant weight loss³ versus placebo, and development for obesity was terminated in 2007; an earlier, smaller signal did not replicate. The supporting mechanism data remain animal and cell-based. So the best human evidence does not support the marketed fat-loss use; it argues against it.

More for digestive & weight