GLP-1 receptor agonists
Also known as: semaglutide, Ozempic, Wegovy, tirzepatide, Mounjaro, Zepbound
Prescription medicines with large clinical trials behind them — the benchmark the research chemicals are measured against.
Regulatory status: Approved for type 2 diabetes and, at higher doses, chronic weight management — prescription-only, under medical supervision.
What it is
GLP-1 receptor agonists are peptide-based medicines — semaglutide (Ozempic, Wegovy) and tirzepatide (Mounjaro, Zepbound) are the best known. They are included in this reference not as “fitness peptides” but as the benchmark: regulated, rigorously-trialled, prescription medicines against which the unregulated compounds can be honestly compared.
Composition
They are engineered peptides that mimic GLP-1 (glucagon-like peptide-1), a gut hormone released after eating. Modifications make them last far longer than natural GLP-1 — days rather than minutes — allowing once-weekly dosing. Tirzepatide additionally acts on the GIP receptor.
Proposed mechanism
They activate GLP-1 (and, for tirzepatide, GIP) receptors, which increases insulin secretion when glucose is high, slows stomach emptying, and reduces appetite via the brain — together lowering blood sugar and food intake.
Claimed benefits
Weight loss, appetite control and improved blood-sugar control. Unusually for this section, these claims are backed by strong evidence.
What the evidence shows
Well-supported· human data. Large randomised placebo-controlled trials — the STEP programme for semaglutide (Wilding et al., NEJM 2021) and SURMOUNT for tirzepatide (Jastreboff et al., NEJM 2022) — enrolled thousands of participants and showed clinically meaningful, sustained weight loss and metabolic improvement. This is what a mature evidence base looks like: pre-registered trials, large samples, hard endpoints, regulatory review.
Legal & regulatory status
Approved for type 2 diabetes and, at higher doses, chronic weight management — prescription-only, under medical supervision. They are not currently on the WADA prohibited list (always check the current list if you compete). Grey-market “research” semaglutide and tirzepatide are sold, but an unlicensed vial carries the same purity, dose-accuracy and sterility risks as any research chemical — the approval process exists precisely so a licensed product is verifiably what it claims to be.
Known risks & unknowns
Common effects include nausea, other gastrointestinal symptoms and reduced appetite; rarer risks (pancreatitis, gallbladder issues) and specific contraindications are why these are prescription medicines. Rapid weight loss can include muscle loss without adequate protein and resistance training. These are real medicines with real risks — used properly, under a clinician, not bought from a peptide vendor.
Sources
Frequently asked questions
- Are GLP-1 drugs peptides?
- Yes — semaglutide and tirzepatide are peptide-based medicines. We include them here to contrast a rigorously-evidenced, regulated, prescription peptide with the unregulated 'research chemicals' that make up most of this section.
- How strong is the evidence for GLP-1 agonists?
- Strong, by the standards of this section: large randomised placebo-controlled trials (the STEP programme for semaglutide, SURMOUNT for tirzepatide) with thousands of participants and clinically meaningful weight and metabolic outcomes, reviewed and approved by regulators.
- Can I buy GLP-1 peptides as 'research chemicals'?
- Grey-market 'research' semaglutide and tirzepatide are sold, but they carry the same quality, purity and dosing risks as any unregulated peptide. The whole point of the approval process is that a licensed product is what it says it is — which grey-market vials are not.
- Are GLP-1 agonists banned in sport?
- They are not currently on the WADA prohibited list. That said, anyone competing should always check the current list, which is updated annually.
Related compounds
- Tesamorelin — Well-supported
An evidence-tiered, non-promotional explainer on tesamorelin (Egrifta): a GHRH analogue, the one GH-releasing peptide with FDA approval and robust trial data — for a specific medical use, not fitness.
- HGH Fragment 176-191 — Marketing claim
An evidence-tiered explainer on HGH Fragment 176-191 / AOD-9604: a growth-hormone fragment marketed for fat loss whose largest human trial failed, leading its developer to abandon it.
Written and reviewed by Mathew Beale — MSc Biotechnology, University of Reading.
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