The peptide weight loss guide

Semaglutide is a GLP-1 receptor agonist originally developed for type 2 diabetes that has demonstrated significant weight loss effects in clinical trials. Sold under the brand names Ozempic (diabetes) and Wegovy (weight management), it is the most prescribed anti-obesity medication worldwide as of 2026. Semaglutide works by mimicking the incretin hormone GLP-1, reducing appetite, slowing gastric emptying, and improving insulin sensitivity. The STEP clinical trial program — spanning over 10,000 participants across multiple studies — established semaglutide as a breakthrough treatment for obesity, with average weight loss of 14.9% over 68 weeks. An oral formulation (Rybelsus for diabetes, oral Wegovy for weight loss) expanded access beyond injection-only delivery. Semaglutide also demonstrated cardiovascular benefits in the SELECT trial, reducing major adverse cardiovascular events by 20% in overweight adults.

Tirzepatide is a first-in-class dual GIP/GLP-1 receptor agonist that has demonstrated greater weight loss than any other approved anti-obesity medication. Sold as Mounjaro (diabetes) and Zepbound (weight management), it activates two complementary incretin pathways simultaneously. The SURMOUNT clinical trial program showed average weight loss of 20.9% at the highest dose — with over half of participants losing 20%+ of body weight. In the landmark SURMOUNT-5 head-to-head trial against semaglutide, tirzepatide produced statistically superior weight loss (20.2% vs 13.7%). Developed by Eli Lilly, tirzepatide represents a paradigm shift from single-receptor to multi-receptor approaches in obesity treatment.

Retatrutide (LY3437943) is a first-in-class triple hormone receptor agonist developed by Eli Lilly that simultaneously activates three metabolic pathways: glucose-dependent insulinotropic polypeptide (GIP), glucagon-like peptide-1 (GLP-1), and glucagon receptors. No other obesity medication in clinical development targets all three receptors in a single molecule. The compound emerged from Eli Lilly's incretin research program, with Phase 1b results published in The Lancet in 2022 (PMID: 36354040) demonstrating approximately 9 kg of body weight reduction in just 12 weeks — enough to advance rapidly into Phase 2. The Phase 2 obesity trial, published in the New England Journal of Medicine in 2023 (PMID: 37366315), produced what was then the highest weight loss ever reported for any pharmaceutical agent: 24.2% body weight reduction over 48 weeks at the 12 mg dose. Every participant in the highest dose group lost at least 5% of their body weight, and 83% lost at least 15%. A parallel Phase 2 trial in patients with type 2 diabetes, published in The Lancet in 2023 (PMID: 37385280), demonstrated dual metabolic benefits: up to 16.9% weight loss alongside a 2.02% reduction in HbA1c at 36 weeks. A dedicated liver fat substudy, published in Nature Medicine in 2024 (PMID: 38858523), showed near-complete resolution of hepatic steatosis — 86% relative reduction in liver fat at the highest dose, with 86% of participants dropping below the 5% threshold that defines normal liver fat content. Retatrutide entered Phase 3 in 2023 through the TRIUMPH clinical trial program — a novel basket trial structure testing the compound simultaneously for obesity, obstructive sleep apnea, and knee osteoarthritis across four major studies enrolling over 5,800 participants (PMID: 41090431). The first Phase 3 readout came in December 2025 from TRIUMPH-4, which tested retatrutide specifically in adults with obesity and knee osteoarthritis. Topline results showed 28.7% average body weight loss at 68 weeks (26.6% placebo-adjusted, approximately 71.2 pounds) at the 12 mg dose — peer-reviewed publication pending. The trial also demonstrated a 75.8% reduction in knee osteoarthritis pain scores, with one in eight participants becoming completely free of knee pain. However, TRIUMPH-4 also revealed a new safety signal not seen in Phase 2: dysesthesia (abnormal sensations of touch), occurring in 8.8% of participants at 9 mg and 20.9% at 12 mg versus 0.7% on placebo. While generally mild and infrequently leading to discontinuation, this finding is being closely monitored in subsequent TRIUMPH readouts. Seven additional Phase 3 readouts are expected throughout 2026, including data on obstructive sleep apnea and cardiovascular disease populations. If results remain positive, Eli Lilly is projected to submit a New Drug Application to the FDA in late 2026, with potential approval in the first half of 2027. Retatrutide is not currently available by prescription, through compounding pharmacies, or from research peptide vendors — the FDA has explicitly stated it cannot be legally compounded.

Liraglutide is an older GLP-1 receptor agonist requiring daily injection. Sold as Victoza (diabetes) and Saxenda (weight loss), it has been largely superseded by weekly semaglutide but remains widely prescribed.

Survodutide is a dual GLP-1/glucagon receptor agonist developed by Boehringer Ingelheim, currently in Phase 3 trials for obesity and metabolic liver disease.