Peptides vs GLP-1s for weight loss: what works

The peptides that work for weight loss are the ones you may already know by brand name. Semaglutide (Wegovy) and tirzepatide (Zepbound) are peptides, both are FDA-approved for weight loss, and both have large trials behind them. The “weight-loss peptides” sold online under names like AOD-9604, MOTS-c and CJC-1295 have no comparable human evidence, and as of October 18, 2026 a licensed pharmacy may not compound any of them. Here is how they compare.

GLP-1 medications are peptides

A peptide is a short chain of amino acids. Semaglutide and tirzepatide are both peptides that mimic gut hormones (GLP-1, and for tirzepatide also GIP) that slow digestion and reduce appetite. What sets them apart from most peptides sold online is that they went through the full FDA approval process, with trials of thousands of people.

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These results come from the drugs’ FDA labels (Wegovy, Zepbound). They carry real risks too: a boxed warning for thyroid C-cell tumors, and label warnings about pancreatitis, gallbladder problems and severe stomach problems. A clinician should review your history first.

Compounded semaglutide and tirzepatide also exist. They are not Wegovy or Zepbound and not generics of them, they aren’t FDA-approved, and the rules for compounding them tightened after the shortages ended. Our compounded GLP-1 guide explains where they stand, and our semaglutide vs tirzepatide comparison covers which works better.

The “weight-loss peptides” sold online

These are the peptides most often marketed for fat loss, and where each stands with the FDA.

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AOD-9604

AOD-9604 is a fragment of human growth hormone marketed for fat loss. Its nomination for compounding was withdrawn, so a 503A pharmacy may not use it. On its compounding safety page, the FDA says it “has also identified serious adverse events that may be associated with AOD-9604, though causality is not clear” (FDA).

MOTS-c

MOTS-c is a peptide studied in labs for its effects on how cells use energy. In July 2026 the FDA’s compounding advisory committee voted 7 to 5, with 2 abstentions, to recommend adding it to the compounding list for obesity and osteoporosis, according to law-firm reports (McDermott). The FDA hasn’t acted on the vote, so it can’t be compounded. The FDA says it has not identified any human exposure data on drug products containing MOTS-c.

CJC-1295 and ipamorelin

These two are often sold together to raise growth hormone, with fat loss as one of the selling points. Both had their compounding nominations withdrawn and may not be compounded. The FDA says it has identified serious adverse events with CJC-1295, including increased heart rate, and serious adverse events including death when ipamorelin was given into a vein.

Tesamorelin

Tesamorelin is the one peptide on this list with an FDA approval tied to fat. Sold as Egrifta SV, it is approved to reduce excess abdominal fat in adults with HIV who have lipodystrophy. In two 26-week trials, belly (visceral) fat fell 18% and 14% on tesamorelin, compared with a 2% rise and a 2% fall on placebo (label). Its label says plainly that it is not indicated for weight loss, and it warns about higher blood sugar. It is a biologic, so it can’t be compounded, and none of the providers we track prescribes it.

Sermorelin

Sermorelin prompts the pituitary gland to release growth hormone. A pharmacy may compound it, and some providers prescribe it to support body composition alongside diet and exercise. It has no FDA approval for weight loss, so that use is off-label and the evidence is limited. Read is sermorelin legal and how is it prescribed.

Retatrutide and cagrilintide

These are investigational weight-loss drugs in clinical trials, not approved products. They can’t be lawfully prescribed outside a trial or compounded. The FDA has sent several warning letters, including two on March 31, 2026, over retatrutide and cagrilintide sold online as research chemicals, calling them unapproved new drugs (FDA).

Why the evidence gap matters

A peptide’s popularity online says little about whether it works. For the GLP-1 medications, we know the average weight loss, the side effects and how often they happen, because thousands of people took them in controlled trials reviewed by the FDA. For AOD-9604, MOTS-c and CJC-1295, most of what’s known comes from animal or lab studies, and the FDA says it lacks human safety data for several of them.

There is a legal gap too. Because a licensed pharmacy may not compound these peptides, anything sold under their names comes from outside the prescription system. Buying vials labeled for research only for personal use is unsafe and unregulated: no prescriber checks whether it suits you, and no one checks what is in the vial. Our guide on whether peptides are safe covers the risks.

How to choose

• If your goal is weight loss, start with the evidence-backed options: FDA-approved GLP-1 medications, prescribed by a clinician who knows your history. Compare licensed programs in our GLP-1 rankings and on the weight loss hub.
• If you have HIV-related lipodystrophy, ask your HIV clinician about tesamorelin.
• If you are interested in peptide therapy for other reasons, use a licensed provider and stick to peptides a pharmacy may legally compound. See our ranked list of peptide providers.

The bottom line

The peptides proven to help with weight loss are the GLP-1 medications, semaglutide and tirzepatide, with average losses of 14.9% to 20.9% in their main trials. AOD-9604, MOTS-c, CJC-1295 and ipamorelin have no comparable evidence and can’t be compounded as of October 18, 2026, and retatrutide is still in trials. If a site promises fast fat loss from a peptide that isn’t an approved drug, treat that as a reason to look elsewhere.