GLP-1 in Sports: Medical Breakthrough, Performance Tool, or Emerging Risk?

Serena Williams of the U.S. in action during her first round match against Australia’s Maya Joint REUTERS/Toby Melville

When Serena Williams disclosed in 2025 that she was using tirzepatide (Zepbound) after struggling to lose weight following her second pregnancy, the story attracted attention beyond medicine. She emphasized that the treatment complemented, not replaced, training and healthy eating, while also acknowledging a commercial partnership with the prescribing platform. In June 2026, Williams returned to professional tennis after 1,375 days and won her first doubles match. Her return is compelling, but it does not provide evidence that GLP-1-based drugs enhance performance. However, it raises an important question in the sporting arena: when a legitimate metabolic treatment changes body mass, appetite, and fueling capacity, what does that mean for athletes’ health, performance, and fair play?

What are GLP-1 Drugs?

Glucagon-like peptide-1 (GLP-1) is a hormone released from the gut after food intake. It helps regulate blood glucose levels by increasing glucose-dependent insulin secretion, reducing glucagon release, slowing gastric emptying, and signaling satiety in the brain. GLP-1 receptor agonists mimic these effects but are engineered to last much longer than natural GLP-1.

Semaglutide (Ozempic/Wegovy) and liraglutide (Victoza/Saxenda) act on GLP-1 receptors. Tirzepatide (Mounjaro/Zepbound), often discussed alongside these drugs, is technically a dual glucose-dependent insulinotropic polypeptide (GIP)/GLP-1 receptor agonist. These medicines are not interchangeable, and brand names do not reliably indicate clinical indications or doses.

Why Are They Prescribed?

GLP-1-based medicines were developed principally for type two diabetes and obesity, which are chronic diseases with substantial cardiovascular and metabolic consequences. Depending on the product and the regulator, approved indications now also include chronic weight management; reduction of major cardiovascular events in selected adults with cardiovascular disease and overweight or obesity; and, for tirzepatide, moderate-to-severe obstructive sleep apnea in adults with obesity.

“This distinction matters in sport.”

This distinction matters in sport. Athletes with type two diabetes or clinically significant obesity may have a sound medical indication and experience better glycemic control, lower cardiometabolic risk, and improved capacity to train. Prescribed treatments should not be automatically equated with cosmetic use or doping. Conversely, obtaining a drug without a proper assessment simply to “make weight” is a very different and potentially hazardous scenario.

Why Might Athletes be Interested?

Lower fat mass may reduce mechanical loading and improve the ratio between force or power and body mass in some sports. This creates an obvious interest in endurance, jumping, aesthetic, and weight-category sports. Appetite suppression may also make weight management easier.

However, a lighter athlete is not necessarily faster, stronger, or healthier. Most GLP-1 research has involved adults with obesity and/or diabetes, not healthy, highly trained competitors. Currently, there is no convincing direct evidence that these drugs improve athletes’ competitive performance. Therefore, extrapolating clinical weight-loss results to elite sports is scientifically unsafe. Although research on this topic is limited, the potential effects of GLP-1 drugs on athletes are multi-factorial (see figure 1).