Retatrutide

Retatrutide is a synthetic peptide that was developed by Eli Lilly and Company to act as a multi‑hormone receptor agonist. It is engineered from the backbone of the hormone Glucose‑dependent insulinotropic polypeptide (GIP) and contains 39 amino acids in its peptide chain.

Retatrutide is designed to simultaneously activate three receptors: GIP, Glucagon‑like peptide‑1 (GLP‑1), and Glucagon. Its purported benefits include substantial reduction in body weight, improved glucose control and enhanced metabolism of fat, as shown in clinical trials where it achieved weight loss in overweight individuals.

In human trials of adults with obesity or type 2 diabetes, Retatrutide produced substantial weight loss, with reductions of about 22.8 % to 24.2 % over 48 weeks at higher doses ¹. In another study of people with type 2 diabetes, it also improved glycaemic control meaningfully ². In pre‑clinical studies in obese rodents, tri­agonists like Retatrutide improved energy expenditure and fat reduction more than dual or mono‑agonists ³.

Beyond weight loss and glucose control, Retatrutide showed important metabolic improvements such as large reductions in liver fat content in obese adults (e.g., more than 80 % reduction in liver fat in some groups). It also improved several metabolic biomarkers like insulin, lipids and fat mass in meta‑analysis of trials ^{4, 5}. Retatrutide appears to provide strong benefits via notable weight reduction, improved glycaemic control, reduced liver fat and broader metabolic enhancements, making it a promising agent for obesity and related metabolic dysfunction.

The most frequently reported side effects of Retatrutide in clinical trials are gastrointestinal in nature. In a phase 2 trial of adults with obesity, participants receiving the drug experienced nausea, vomiting, diarrhea and constipation, and the severity of these effects increased with higher doses ⁶. A systematic review of randomized controlled trials noted “non‑severe gastrointestinal and hypersensitivity adverse events” occurring more often in the Retatrutide group than placebo ⁷. Elevated heart rate was also observed in some participants; for example, one review reported a mean increase of up to 6.7 beats per minute ⁸.

Retatrutide activates three different hormone receptors in the body: the glucose‑dependent insulinotropic polypeptide (GIP) receptor, the glucagon‑like peptide‑1 (GLP‑1) receptor, and the glucagon receptor. Through GIP and GLP‑1 receptor activation the drug enhances glucose‑stimulated insulin secretion and slows gastric emptying which helps reduce food intake and improve glycaemic control ^{9, 10}. Activation of the glucagon receptor increases fat oxidation and energy expenditure, as seen in animal studies of tri‑agonist compounds, supporting greater weight loss beyond the effects of appetite suppression alone ¹¹. In sum, retatrutide works by combining reduced food intake, improved insulin response, and increased energy burn to affect body weight and metabolism.

Retatrutide is not FDA-approved for human use in the United States. However, it is currently being studied in clinical trials as an investigational drug for obesity and metabolic disorders ¹². For sport, Retatrutide is not currently on the World Anti-Doping Agency (WADA) Prohibited List and is therefore generally allowed in sports governed by the WADA code. However, WADA has been monitoring the use of GLP-1 medications, including retatrutide, since 2024 to detect potential patterns of misuse and may ban them in the future if they are found to meet two of the three criteria for prohibition (performance enhancement, health risk, or violation of the spirit of sport).