Serena Williams is back on a tennis court, and her return arrives with a far bigger question attached to it. The 23-time Grand Slam singles champion has become the most visible elite athlete to compete after openly saying she used a GLP-1 drug for weight loss.
That detail matters because GLP-1 drugs are being watched by anti-doping authorities, even though they are not banned. Williams has now been pulled into a wider debate about whether weight-loss medicines could eventually be treated as performance-enhancing in sport.
Williams Returns To Competition
Williams teamed with rising Canadian teenager Victoria Mboko for a straight-sets doubles win over the No. 3 seeds at the Queen’s grass-court tournament in London. It was her first professional match in nearly three years, and the comeback drew immediate attention across the sport.
No one expects the return to stop at Queen’s, though Williams has not directly committed to singles yet. Her comeback also put her back in the spotlight as one of tennis’s biggest stars, long after she had stepped away to focus on life beyond the court.
Why Her GLP-1 Use Stands Out
Last summer, Williams said on Oprah Winfrey’s podcast that she had been taking Zepbound, one of the newer GLP-1 drugs. She said she had tried almost every other path after her two pregnancies, but training alone was not getting her where she wanted to be.
“I couldn’t beat the weight. It was the one opponent I couldn’t beat,” Williams said, adding that she had used Ro, the telehealth company where she is a paid ambassador, to manage treatment. She later told Winfrey, “I wish I had done this while I was still playing. It would have made such a big difference for me and my career.”
GLP-1s, or glucagon-like peptides, include semaglutides and tirzepatides, the two main classes now on the World Anti-Doping Agency monitoring program. They work by mimicking glucagon, slowing digestion, reducing appetite and helping people lose weight.
What Anti-Doping Officials Are Watching
WADA has not banned GLP-1s, and there is no timetable for deciding whether they should be added to the Prohibited List. The agency says the drugs were placed on its Monitoring Program to track patterns of use in sport, both in and out of competition.
To be banned, a substance must meet two of three criteria: performance enhancement, health risk, or violation of the “spirit of sport.” The last category is the most disputed, and it has fueled debate over whether science alone should decide what belongs on the list.
WADA has also shown growing concern about weight-loss drugs in sports. Minutes from its Health and Research Committee last August showed discussion of creating a new class for weight management substances, including for weight-sensitive sports such as gymnastics, figure skating and cycling.
Health Effects Could Cut Both Ways
The case against GLP-1s as performance enhancers is not simple. While fat loss could help some athletes, studies have also shown muscle loss, which would work against performance in many sports.
That has already pushed researchers and drug makers to look for ways to prevent lean-muscle loss. VERU, a Miami-based pharmaceutical company, has said its experimental drug Ostarine, also known as enobosarm, showed early success in trials for muscle wasting, though it is on WADA’s Prohibited List and available on the black market.
Industry scientists say newer GLP-1 products may be designed to reduce side effects like muscle loss, which could change how anti-doping officials view them. Matthew Fedoruk, chief science officer at USADA, said that could make them “more advantageous for athletes” and described them as “a growing threat.”
Could A Therapeutic Exemption Apply?
If GLP-1s were ever prohibited, athletes could theoretically seek a therapeutic use exemption for a legitimate medical condition. The most likely example would be diabetes, where a drug could be allowed if it did not meaningfully enhance performance.
That possibility shows why Williams’s case resonates beyond tennis. Her use of a weight-loss drug is legal, medically common, and still tied to the same questions that could one day shape how sports treat a whole class of medicines.
For now, Williams is simply back on court, drawing the same attention she always has. But her comeback also places a familiar sports icon at the center of a new argument about treatment, advantage and where the line should be drawn.
