# GLP-1 Evidence > What the trials actually show about semaglutide, tirzepatide and the rest of the GLP-1 class. GLP-1 Evidence tracks the clinical literature on GLP-1 and dual-agonist drugs — efficacy, body composition, cardiovascular outcomes, side effects, and what happens when people stop. Every claim is tied to a PubMed record. ## About this source - **Publisher:** Stéphane Sprauer - **Editorial stance:** Independent. We describe what the evidence shows, including when it is weak or contested. - **Evidence base:** 66 peer-reviewed citations, each linked to its PubMed record or DOI. - **Languages:** 42 European languages. Add a language prefix to any URL, e.g. `https://glp1facts.org/de/`. - **Licence:** Content may be quoted with attribution to GLP-1 Evidence (https://glp1facts.org). - **Not medical advice:** Educational content only. ## How to cite this site > GLP-1 Evidence. "". https://glp1facts.org. Accessed . ## Home - [GLP-1 Evidence](https://glp1facts.org/): Cited summaries of the semaglutide and tirzepatide evidence: how much weight, how much muscle, and what happens when you stop. ## Mechanism - [How GLP-1 drugs actually work](https://glp1facts.org/how-glp1-works/): GLP-1 receptor agonists slow gastric emptying and act on hypothalamic satiety circuits. Here is what the mechanistic trials measured, and what they did not. ## Drugs - [Semaglutide: what the trials show](https://glp1facts.org/semaglutide/): STEP 1 to STEP 5, SELECT, and the head-to-head against tirzepatide — semaglutide effect sizes with the trial designs that produced them. - [Tirzepatide: what the trials show](https://glp1facts.org/tirzepatide/): SURMOUNT-1 and -2, the sleep apnoea and heart failure trials, and the head-to-head win over semaglutide — tirzepatide evidence with effect sizes. - [Oral GLP-1 pills: semaglutide 25 mg and orforglipron](https://glp1facts.org/oral-glp1/): Oral semaglutide and the small-molecule agonist orforglipron — trial results, how they compare with injections, and what a pill changes. - [The drugs](https://glp1facts.org/drugs/): Semaglutide, tirzepatide and the oral agents — one page each, with the trials that produced the numbers. - [Incretin drugs](https://glp1facts.org/drug/): What the trials show for 6 GLP-1 and incretin drugs — effect sizes, limits, and what happens on stopping. - [Semaglutide: what the trials actually show](https://glp1facts.org/drug/semaglutide/): GLP-1 receptor agonist. Type 2 diabetes and, at the higher dose, weight management. What the trials show and what they do not. - [Tirzepatide: what the trials actually show](https://glp1facts.org/drug/tirzepatide/): Dual GIP / GLP-1 receptor agonist. Type 2 diabetes and weight management. What the trials show and what they do not. - [Liraglutide: what the trials actually show](https://glp1facts.org/drug/liraglutide/): GLP-1 receptor agonist. Type 2 diabetes and weight management. What the trials show and what they do not. - [Dulaglutide: what the trials actually show](https://glp1facts.org/drug/dulaglutide/): GLP-1 receptor agonist. Type 2 diabetes. What the trials show and what they do not. - [Oral semaglutide: what the trials actually show](https://glp1facts.org/drug/oral-semaglutide/): GLP-1 receptor agonist, oral. Type 2 diabetes; higher-dose oral formulations for weight management have been trialled. What the trials show and what they do not - [Compounded GLP-1 preparations: what the trials actually show](https://glp1facts.org/drug/compounded-glp1/): Unapproved compounded preparation. Not approved. Sold through compounding pharmacies and online sellers.. What the trials show and what they do not. ## Effects - [How much of GLP-1 weight loss is muscle?](https://glp1facts.org/muscle-loss/): Body-composition data from the semaglutide and tirzepatide trials: how much lean mass is lost, how that compares with dieting, and whether it matters. - [GLP-1 side effects, ranked by how often they happen](https://glp1facts.org/side-effects/): Nausea, vomiting, constipation and the rarer events — GLP-1 side-effect rates from the randomised trials, separated from the anecdotes. - [Do GLP-1 drugs protect your heart?](https://glp1facts.org/cardiovascular/): SELECT, the diabetes outcome trials and the pooled meta-analyses — what GLP-1 receptor agonists do to cardiovascular events. - [GLP-1 drugs beyond weight loss: kidneys, liver, sleep apnoea, addiction](https://glp1facts.org/beyond-weight-loss/): Where GLP-1 receptor agonists have real evidence outside obesity and diabetes — and where the claims are running well ahead of the trials. - [The effects](https://glp1facts.org/effects/): What GLP-1 drugs do to body composition, the gut, the heart, the kidneys and the liver. ## Stopping - [What happens when you stop taking a GLP-1 drug](https://glp1facts.org/stopping/): Withdrawal data from STEP 1 and STEP 4: how much weight comes back, how fast, and what it means for treating obesity as a chronic condition. ## About - [About GLP-1 Evidence](https://glp1facts.org/about/): Who publishes GLP-1 Evidence, how pages are researched, and how the site makes money. - [Editorial policy](https://glp1facts.org/editorial-policy/): How GLP-1 Evidence selects evidence, scores products and handles conflicts of interest. - [Affiliate and partnership disclosure](https://glp1facts.org/disclosure/): Every commercial relationship that could affect what you read on GLP-1 Evidence. - [Privacy](https://glp1facts.org/privacy/): What GLP-1 Evidence collects — which is close to nothing. ## Research - [New research](https://glp1facts.org/research/): Newly indexed peer-reviewed research relevant to GLP-1 Evidence, updated weekly from PubMed and Crossref. - [Research digest, 8 August 2026](https://glp1facts.org/research/2026-08-08/): No newly indexed research matched this site's topics in the week of 8 August 2026. ## Related sites in this network - 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