Fragment 176-191 vs AOD-9604: these are nearly the same molecule, a 16-amino-acid piece from the tail end of human growth hormone that was studied as a fat-burning drug. FDA describes AOD-9604 as growth hormone’s amino acids 177 to 191 with an extra tyrosine added at the front;[1] Fragment 176-191 is the same stretch starting one position earlier. AOD-9604 was tested in about 900 people, and in its largest trial of 502 adults it did not cause significantly more weight loss than placebo.[6][1] Fragment 176-191 has no human trials at all.[9] Neither is approved.
See the AOD-9604 profile, the HGH profile and the muscle and metabolism peptides hub.
Fragment 176-191 vs AOD-9604 at a glance
| Fragment 176-191 | AOD-9604 | |
|---|---|---|
| Structure | hGH amino acids 176-191[2] | hGH 177-191 plus an added tyrosine[1] |
| Developed | Studied in rats since the 1970s[2] | Monash University, Melbourne, 1990s[15] |
| Animal results | Related 177-191 fragment cut weight gain in obese mice[3] | Raised fat burning and cut weight gain in obese mice[4] |
| Human trials | None found | Six company trials, about 900 people[6] |
| Largest trial result | Not applicable | No significant weight loss vs placebo[1] |
| Blood sugar | Brief glucose rise in rats[2] | No effect on IGF-1 in humans[1] |
| FDA compounding | Not evaluated by name | Advisers voted 0 to 12 against[7] |
| Sport | Banned[12] | Banned[12] |
Are they the same thing?
Growth hormone is a 191-amino-acid protein. In the 1970s, Australian researchers made short synthetic pieces of its tail end to find which part carried which effect. In rats, the pieces covering 172-191, 176-191, 177-191 and 178-191 all caused a short-lived rise in blood sugar and a longer rise in insulin.[2]
Later, the same Monash group found that the 177-191 piece reduced weight gain and fat tissue in obese mice.[3] They then added a tyrosine to the front to make AOD-9604 (“Anti-Obesity Drug 9604”).[1] So the two names describe peptides that differ by at most one amino acid at the start. A 2026 review even describes AOD-9604 as “hGH 176-191,”[10] which shows how loosely the names are used. A vial labeled one could plausibly contain the other.
How they are supposed to work
In obese mice, both growth hormone and AOD-9604 increased fat burning and reduced weight gain. Unlike growth hormone, AOD-9604 did not raise blood sugar, did not bind the growth hormone receptor and did not make cells multiply in those experiments.[4] In mice lacking a key fat-cell receptor (the beta-3 adrenergic receptor), long-term AOD-9604 no longer reduced body weight, although the authors concluded the receptor was not its direct target.[5] Whether these mouse pathways work the same way in people is not known.
Evidence quality
AOD-9604 in people
- OPTIONS trial: 536 adults with obesity enrolled and 502 were randomized to 0.25, 0.5 or 1 mg by mouth daily or placebo, with diet and exercise, for 24 weeks. Weight loss was not significantly different from placebo at 12 or 24 weeks, and the company ended obesity development.[1]
- Other trials: six company-funded studies included about 900 people, mostly testing safety.[6] FDA notes the main efficacy results were never published in a medical journal.[1]
- Injection under the skin, the way it is sold today, was never tested in a human efficacy trial.[1]
Fragment 176-191 in people: none. The only recent primary study we found tested it alongside a chemotherapy drug in breast cancer cells in a lab.[9] A 2026 review lists it among peptides promoted for fat metabolism despite limited clinical evidence.[11]
Side effects and safety
AOD-9604 (FDA review of company data):[1]
- Oral use: headache, diarrhea and gas were most common.
- IV use: headache, fatigue and dizziness; chest tightness and euphoria were judged possibly related.
- No change in IGF-1, and no antibodies found in tested participants.
- Cancers were reported in a 12-week trial; investigators judged them unrelated, and FDA said too little detail was given to assess this.
FDA adds that the peptide can clump and carry impurities, raising immune-reaction concerns for injected forms.[1][8]
Fragment 176-191: no human safety data. The rat study found brief rises in blood sugar and insulin, contrary to marketing claims of no metabolic effects.[2]
Both: products sold online are unregulated. Belgian authorities seized vials of AOD-9604 that had to be identified by lab analysis.[13]
Doses studied
Only AOD-9604 has human dosing data, and none of it involved the injection under the skin used by today’s sellers.[1]
| Route | AOD-9604 doses studied in people |
|---|---|
| IV, single doses | Small, short studies in healthy volunteers[1] |
| By mouth, 12 weeks | Up to 30 mg daily[1] |
| By mouth, 24 weeks (OPTIONS) | 0.25, 0.5 or 1 mg daily[1] |
| Injection under the skin | Never tested in a human efficacy trial[1] |
For Fragment 176-191, there is no human dose of any kind. The rat study that found brief blood sugar rises used research doses that do not translate to people.[2] Doses listed online come from sellers, not trials. A clinician should be involved in any decision about an unapproved substance.
Legal status
- Not approved: neither has FDA approval.[1]
- AOD-9604 compounding: nominations were withdrawn, but FDA reviewed it anyway, and in December 2024 its compounding advisory committee voted 0 to 12 against it.[1][7] FDA lists it among substances with possible immune-reaction risks.[8]
- “GRAS” claims: in 2012 the company announced a self-affirmed GRAS (generally recognized as safe) determination for food use, made by its own expert panel, not FDA.[14]
- Sport: WADA bans growth hormone fragments, including AOD-9604 and hGH 176-191, at all times.[12]
See peptides and GRAS status. This is general information, not legal advice.
Questions to discuss with a clinician
- Is weight loss the goal? Approved medicines have large positive trials; see best peptides for weight loss.
- Do you have diabetes or prediabetes? The rat data on blood sugar are worth discussing.[2]
- Do you compete in tested sport? Both are banned.[12]
The verdict
AOD-9604 is the better-studied of the two, and the key human trial was negative.[1] Fragment 176-191 is essentially the same peptide with no human testing at all.[9] What is known: both cut weight gain in mice. What is not known: any proof that either helps people lose fat. Related: IGF-1 LR3 vs MGF, peptides vs SARMs and peptides vs prohormones.
