Serena Williams publicly disclosed her GLP-1 use in 2025 and has since returned to competitive tennis, a combination PopSugar reports has pushed the question of weight-loss drugs into professional sport. During the Cincinnati Open in August, a Ro banner showing Williams injecting a GLP-1 medication flew above the tournament grounds, and online commenters began tying her body change, her commercial partnership, and her comeback together.

The drugs at the center of this are semaglutide and tirzepatide, the GLP-1 receptor agonists used for obesity and type 2 diabetes. They work in part by suppressing appetite, which is exactly the mechanism that makes the sports question more complicated than it first looks.

What the survey actually found

A newly published study surveyed sports physicians, not athletes. Of those who responded, 12 percent said they were aware of athletes using GLP-1 drugs without medical need, and 13 percent said athletes had approached them about the medications.

Those figures do not describe how common use is among athletes, and the study cannot establish prevalence. Daniel Read, PhD, of the University of Hertfordshire, an author of the study, says the interest physicians encountered appeared to have several motivations, including performance enhancement, body image, and legitimate medical need.

Where WADA has landed

Semaglutide and tirzepatide sit on the World Anti-Doping Agency's Monitoring Program, which tracks substances that are not prohibited but that WADA wants to watch. WADA spokesperson Andrew Maggio says that because the drugs are not prohibited, a positive finding is not reported as an adverse analytical finding and carries no consequences for the athlete.

Maggio also says the WADA Executive Committee has decided not to change the status of GLP-1 receptor agonists for 2027. Monitoring data goes to WADA's List Expert Advisory Group before any listing decision.

Lighter is not the same as faster

"Weight loss and performance enhancement are not the same thing," says Alexandra Sowa, MD, an obesity medicine physician and author of "The Ozempic Revolution." She adds that there is currently no clinical evidence showing GLP-1 medications enhance elite athletic performance.

Sowa notes that appetite suppression can make under-fueling easy against a heavy training load, raising concerns about dehydration and inadequate energy availability, and that significant weight loss includes some lean mass. Read says no research on elite athletes yet exists at a quality sufficient to say whether these medications offer any competitive advantage or disadvantage.

The open question

Read would want randomized, double-blind, placebo-controlled trials comparing athletes who use the drugs with those who do not, and even then researchers would have to define what performance means. Sowa's concern is that potential misuse by already-lean athletes not get conflated with legitimate obesity treatment, and for now WADA is gathering information rather than drawing a line.