Serena Williams is returning to tennis — and bringing the GLP-1 debate with her

Serena Williams is set to return to the WTA Tour at the HSBC Championships in Queen's Club, four years after her farewell match at the US Open.

During her time away, the 23-time Grand Slam winner and former highest-earning woman in sport has expanded her business portfolio and inked major endorsement deals—including a multi-year partnership with Ro, a digital health platform that provides GLP-1 drugs for weight loss.

In 2025, Williams opened up about her experience taking Zepbound, citing not only weight loss but improved health overall. “Some of my health stats are even better than they were when I was playing tennis professionally, if you can imagine that!” she said.

With her return to professional competition looming, questions follow. What does the World Anti-Doping Agency (WADA) say about GLP-1 drugs like Zepbound and Ozempic? Do they enhance or impair performance? And would Serena need to stop taking them while competing?

Our deep dive on GLP-1s, tennis and WADA—and what it all means for Serena—covers everything you need to know.

Read More: Holger Rune defends Serena Williams after Ro's Super Bowl ad backlash

What are GLP-1 drugs?

GLP-1s (glucagon-like peptide-1 receptor agonists) are medications originally developed to treat type 2 diabetes and now widely prescribed for chronic weight management. They work by mimicking a gut hormone that reduces appetite and cravings, while helping regulate blood sugar through increased insulin production.

Common GLP-1 drugs include semaglutides (Ozempic, Wegovy) and tirzepatides (Mounjaro, Zepbound). Most are taken via weekly or daily self-injection.

What is Ro? Does Ro provide GLP-1 drugs?

Ro (formerly ‘Roman’), is an online telehealth platform launched in 2017 that gives patients access to two FDA-approved GLP-1 medications, Wegovy and Zepbound, as part of its weight-loss program, the Body Program.

To qualify, Ro patients must have a body mass index (BMI) of 27–30 or higher and at least one weight-related health condition, such as type 2 diabetes, high cholesterol or high blood pressure.

What is Serena Williams’ relationship with Ro?

Williams became a brand ambassador for Ro in 2025. She has credited Zepbound for her post-tennis weight loss in interviews and on social media, frequently sharing training clips that fueled early comeback speculation.

She also starred in Ro’s largest ad campaign to date, launching the “Healthier on Ro” campaign during Super Bowl LX. The spot drew mixed reactions amid broader debate around celebrity endorsements of weight loss drugs.

Ro refers to Serena as “a real Ro member and paid partner” and discloses a family investment in the company. Her husband, venture capitalist and Reddit co-founder Alexis Ohanian, is an investor and serves on Ro’s board.

How much weight did Serena Williams lose on GLP-1s?

Williams says she lost 34 pounds after one year on Zepbound (tirzepatide). She has also reported steadier blood sugar levels, reduced cardiovascular risk and a 30 percent improvement in total cholesterol—noting that some markers are now better than when she was competing.

“There’s less stress on my knees, so I can pull off moves that I could, quite frankly, never do before,” Serena said in a video shared on Ro’s social channels. “Plus I just have so much more energy now to show up for my kids, for my family and just for my life in general."

Ro says its patients lose an average of 14–20 percent of body weight after a year, with total cholesterol improving by about 4.8 percent.

Why did Serena Williams start taking a GLP-1?

Williams detailed her decision in a Vogue interview published in August 2025, confirming her use of Zepbound and her desire to address stigma around GLP-1 drugs.

“I’ve heard negative comments, along with a tremendous amount of positive comments, about my body my entire life,” she told Vogue’s Margaux Anbouba. “For lack of a better way to say it, I don’t really care what people are saying about my body anymore. But what is important to me is transparency…

“It was so hard after I had (my first daughter) Olympia. I was literally on the court every day, doing nothing else. I had been the ultimate super-athlete… but I just could never get back to where I needed to be, no matter what I did.

“My whole life is being in the gym… I would always get to a certain point on the scale, but I could never get below that. That’s when I decided that it was time to try something different and got on the GLP-1 with Ro.”

What is WADA’s stance on GLP-1s like Zepbound?

According to WADA, semaglutides and tirzepatides remain permitted in sport, meaning Williams would not be required to stop taking Zepbound while competing if she chooses.

Both drug classes are under scrutiny. Semaglutide was added to WADA’s Monitoring Program in 2024, with tirzepatide following in 2025. The program allows WADA labs to track usage trends and potential health risks without issuing sanctions.

Substances on the Monitoring Program are reviewed annually and may later be added to the Prohibited List. Other monitored substances include stimulants such as Wellbutrin, caffeine and nicotine, as well as narcotics like codeine, fentanyl and tramadol.

Do GLP-1 drugs affect athletic performance?

There’s no clear consensus. Current evidence does not show that GLP-1 drugs inherently enhance performance in healthy, non-diabetic athletes—though they are being closely examined in weight-sensitive sports such as cycling, equestrian, wrestling, gymnastics and figure skating.

Potential drawbacks also exist. Appetite suppression can make it harder to meet calorie and carbohydrate needs, affecting fueling, endurance and recovery. Slower gastric emptying means food stays in the stomach longer, which can also complicate pre-match nutrition timing.

Among the biggest concerns are fatigue and the potential for lean muscle loss. Elite athletes like Serena can help mitigate those risks through structured strength training, appropriate vitamin and supplements use, adequate hydration and a diet that includes a significant amount of protein.