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Only one class actually works — the GLP‑1s. Everything else sold as a weight-loss peptide is unproven, off-label, or grey-market. Here is the whole landscape, sorted honestly.
~21% at 72 weeks (SURMOUNT-1)
The most effective weight-loss peptide you can actually get. A prescription injectable, FDA-approved, with the largest average loss of any approved drug.
~15% at 68 weeks (STEP 1)
The other proven peptide. Same class, slightly behind tirzepatide, available as an injection and now a pill (oral semaglutide 25 mg, ~13.6%).
~5-8% (daily injection)
The original GLP-1 for weight loss. FDA-approved and real, but a daily shot for less than half the effect of tirzepatide — largely superseded.
28.3% at 80 weeks (TRIUMPH-1 Phase 3)
The genuinely exciting one — and the only non-approved peptide here worth watching. Lilly's Phase 3 delivered 28.3% average loss, with 45% of the top-dose group losing at least 30% of body weight. It is investigational and NOT yet FDA-approved, so anything sold as "retatrutide" today is grey-market and unverified.
~18% trunk fat — in HIV lipodystrophy only
FDA-approved, but only to reduce visceral fat in people with HIV-associated lipodystrophy. It is not approved or shown to work for general weight loss, and using it for that is off-label. The med-spa framing quietly drops the "in HIV patients" part.
2.6 kg vs 0.8 kg placebo over 12 weeks
Marketed as a fat-loss peptide. Its one decent trial showed a couple of kilos over placebo — trivial next to a GLP-1 — and it is not FDA-approved for weight loss. Not worth the needle or the money.
No weight-loss trials
These raise growth hormone and IGF-1; they do not have controlled trials showing weight loss, and they are not FDA-approved for it. They are sold almost entirely grey-market, "for research purposes only" — the exact products the FDA warns about.
No human weight-loss trials
Experimental. Interesting biology in animals around metabolism, no human weight-loss evidence, no approval. Anything sold today is unregulated.
Why the search results are full of med spas. The peptides with no evidence are the ones clinics can sell you directly — the GLP-1s need a real prescription and a pharmacy, the others get compounded or sold grey-market at high margin. When a page ranks these as equals, follow the money. The honest ranking and the profitable one are not the same list.
Only the GLP-1 class, and it is not close. Tirzepatide (Zepbound) averages about 21% body-weight loss and semaglutide (Wegovy) about 15% in their trials — both FDA-approved, both peptides. Everything else sold under the "peptide" banner for weight loss is either not approved, not studied for weight loss, or approved for something entirely different. Retatrutide, Lilly's triple agonist, is the one genuine exception on the horizon — 28% in Phase 3 — but it is not FDA-approved yet, so nothing you can buy labelled "retatrutide" today is a verified product.
No, and that is the honest answer med spas selling them will not give you. CJC-1295 and ipamorelin raise growth hormone but have no controlled trials showing weight loss. AOD-9604's best study showed about two kilograms over placebo in 12 weeks — a rounding error next to a GLP-1. MOTS-c has no human weight-loss data at all. None of them is FDA-approved for weight loss, and nearly all are sold grey-market as "research chemicals" — the products the FDA has issued warning letters about. If a clinic is offering you these as a weight-loss programme, you are paying for hope, not evidence.
Ozempic (semaglutide) IS a peptide — that part is true, and it is why "peptides for weight loss" and "GLP-1" overlap so much. But "peptide" is a chemistry word, not a quality guarantee. A prescription GLP-1 and a grey-market "research peptide" vial can both be peptides while being worlds apart in whether anyone has verified the molecule, the dose and the sterility. The word does not make two things equivalent.
Buying "research peptides" online to inject yourself is where people get hurt. These are unregulated, often labelled "not for human consumption" as a legal dodge, and the vial may contain the wrong molecule, too much, too little, or nothing. Dosing them "in units" from a reconstitution calculator is a documented overdose route. If cost is the reason you are considering it, there are legal routes to a real GLP-1 that are far cheaper than the retail sticker — and none of them ask you to become your own pharmacist.