New research suggests weight-loss drugs, such as semaglutide and tirzepatide, are being used by some high-level athletes without a medical need, raising questions about their effect on performance and athlete health
The study, led by Loughborough University in the U.K., and surveyed 114 physicians working with highly trained athletes across 93 sports and 38 countries. One in 10 said they were aware of athletes using weight-loss drugs without a medical reason. Forty-four per cent thought the drugs should be prohibited by the World Anti-Doping Agency (WADA)
Low energy availability issues for runners
GLP-1 drugs mimic a hormone involved in blood-sugar control and appetite. The drug class was first developed to treat type 2 diabetes, before some medications were later approved specifically for weight loss. Semaglutide, the active ingredient in Wegovy and Ozempic, suppresses appetite and slows digestion. Tirzepatide, sold as Mounjaro and Zepbound, works through both GIP and GLP-1 pathways
Because both of these drugs can cause substantial weight loss, they have appeal in sports where athletes are taught that being lighter may improve performance. But there are currently no published trials showing that semaglutide or tirzepatide makes competitive runners faster, and almost all of the major research on these medications has looked at people who are dealing with obesity, are overweight or have diabetes, rather than highly-trained athletes
Lighter doesn’t equal faster (or healthier)
Weight loss from GLP-1 drugs doesn’t just come from body fat; studies have also shown losses in lean (muscle) mass
For runners, the biggest concern may be that appetite suppression makes it harder to eat enough to meet the demands of training and can contribute to low energy availability, which occurs when athletes do not consume enough energy to meet both exercise demands and normal body functions. This can also contribute to Relative Energy Deficiency in Sport, or RED-S, which can impact bone health, hormones, metabolism, recovery and performance
Track and field already has a well-documented problem with low energy availability. A study of elite European cross-country runners found that 64 per cent were considered at risk of low energy availability, including nearly 80 per cent of the women and 54 per cent of the men. A2025 study of 38 collegiate female distance runners also found that athletes showing signs of metabolic suppression before the season went on to have poorer performance outcomes
Why you should be aware of RED-S (even if you are neither elite nor female)
WADA is keeping watch
GLP-1 drugs are not currently banned by WADA, but semaglutide has been on WADA’s Monitoring Program since 2024. In the 2026 program, WADA is monitoring markers that are connected to both semaglutide and tirzepatide both in and out of competition
The agency is also supporting research into improved methods for detecting GLP-1 drugs in athletes
