Weight loss peptides range from FDA-approved prescription drugs to unproven products sold online. The best-studied are the GLP-1-based medicines semaglutide (Wegovy) and tirzepatide (Zepbound), which produced average weight loss of about 15% to 21% in large trials.[2][3] Pipeline drugs such as retatrutide may go further, while products like AOD-9604 have no good evidence of weight loss in people.[4][13]

What are weight loss peptides?

Weight loss peptides are short chains of amino acids that act on hormone receptors controlling appetite, digestion and energy use. Most of the effective ones copy gut hormones, especially GLP-1, a natural regulator of appetite.[7]

The term is used loosely. It covers approved drugs, drugs still in trials, and products sold as “research peptides” that have never been shown to work in people. Two compounds often grouped with them, orforglipron and SLU-PP-332, are small molecules rather than peptides, and so is 5-Amino-1MQ. Weight loss also overlaps with blood sugar control; see metabolic peptides for diabetes drugs and mitochondrial compounds.

Browse all weight loss peptides

See all 17 weight peptides ↓

How weight loss peptides work

GLP-1 agonists such as semaglutide and liraglutide activate the GLP-1 receptor. This lowers appetite and slows how fast the stomach empties, so people eat less.[7] Tirzepatide also activates the GIP receptor, a second gut hormone pathway.[8]

Glucagon combinations add a third lever. Retatrutide activates the GIP, GLP-1 and glucagon receptors; in mouse studies the glucagon component increased energy use.[22] Survodutide, mazdutide and pemvidutide pair GLP-1 with glucagon.[10][12][21]

Amylin analogs copy a hormone released from the pancreas with insulin that signals fullness and slows stomach emptying.[23] Cagrilintide is a long-acting version tested alone and with semaglutide.[11]

The unproven products work through different routes. AOD-9604 is a piece of growth hormone meant to stimulate fat breakdown.[13] 5-Amino-1MQ blocks an enzyme called NNMT, and SLU-PP-332 switches on exercise-related genes; both reduced fat in mice but have not been tested in people.[14][15]

FDA-approved vs research peptides for weight loss

The difference is the size and quality of the evidence.

  • Approved drugs: semaglutide 2.4 mg lowered weight by 14.9% over 68 weeks versus 2.4% on placebo in STEP 1.[2] Tirzepatide’s top dose lowered it by 20.9% over 72 weeks versus 3.1% in SURMOUNT-1.[3] In the head-to-head SURMOUNT-5 trial, tirzepatide beat semaglutide, 20.2% versus 13.7%.[1] Liraglutide, the older daily option, produced 8.4 kg of weight loss versus 2.8 kg on placebo.[6]
  • Investigational drugs: retatrutide 12 mg produced 25.0% average weight loss over 80 weeks in TRIUMPH-1.[4] Survodutide produced 12.2% to 13.0% over 76 weeks.[10] CagriSema lowered weight by 20.4% versus 3.0% on placebo.[11] Mazdutide, approved in China, lowered it by up to 14.0% over 48 weeks in Chinese adults.[12] These trials are large and well designed, but none of these drugs has FDA approval yet.
  • Unproven products: AOD-9604’s largest human trial, in 536 people, found no significant weight loss versus placebo, and the developer ended obesity development in 2007.[13] 5-Amino-1MQ and SLU-PP-332 have only animal data.[14][15]

Who the approved drugs are for

Wegovy and Zepbound are approved for chronic weight management in adults with obesity, or with overweight plus at least one weight-related condition such as high blood pressure or type 2 diabetes, alongside diet and exercise.[7][8] Both labels now go beyond weight: Wegovy is also approved to lower the risk of heart attack, stroke and cardiovascular death in adults with heart disease and excess weight, and Zepbound to treat moderate to severe obstructive sleep apnea in adults with obesity.[7][8] None of the investigational or unproven compounds on this page has an approved use, so there is no label telling patients or doctors how to use them safely.

Oral vs injectable weight loss drugs

Most weight loss peptides are weekly injections under the skin, because peptides are broken down in the gut. Two approved pills now exist:

  • Wegovy tablets contain semaglutide with an absorption enhancer and are taken once daily. Oral semaglutide must be taken on an empty stomach with a small amount of water, before eating.[7]
  • Foundayo (orforglipron) is a small molecule, not a peptide, so it survives digestion and can be taken with or without food.[9] In its 72-week phase 3 trial, the top dose lowered weight by 11.2% versus 2.1% on placebo.[5]

The pills are easier for people who dislike needles, but in their main trials orforglipron produced less weight loss than the strongest injections.[5][3] Pills can also help people keep weight off: in ATTAIN-MAINTAIN, people switched from Zepbound or Wegovy to orforglipron kept most of their weight loss, while those switched to placebo regained much of it.[24] Products sold online as oral or nasal versions of injectable peptides have not been tested in this way.

Safety, legality and sports rules

Approved drugs carry known risks. The most common side effects are nausea, diarrhea, vomiting and constipation. Labels for semaglutide and tirzepatide carry a boxed warning about thyroid C-cell tumors seen in rodents, and warn about pancreatitis and gallbladder problems.[7][8]

Unapproved and “research” products carry extra risks. FDA has warned companies selling semaglutide, tirzepatide, retatrutide, survodutide and mazdutide labeled “for research purposes” or “not for human consumption,” and says the quality of these products is unknown.[16] FDA also states that retatrutide and cagrilintide cannot legally be used in compounding.[16] A 2026 JAMA news article described a growing black market for unapproved GLP-1 drugs such as retatrutide and the risks of using them.[19]

On compounding, FDA lists AOD-9604 among substances it flagged as possible significant safety risks before their compounding nominations were withdrawn by the nominators.[17] In December 2024, FDA’s compounding advisory committee voted 0 to 12 against adding it to the 503A bulks list.[25] FDA’s 503A nominations list shows which other substances have been put forward.[18]

Growth hormone-related products such as AOD-9604 are also covered under growth hormone peptides, and exercise mimetics like SLU-PP-332 under performance peptides.