Serena Williams marked her return to high-level tennis with a straight-sets win in women’s doubles at Queen’s in London, partnering with Victoria Mboko. Her comeback reignited a wider sports debate after Williams said last summer she had been taking the GLP-1
Serena Williams stepped onto the grass at Queen’s in west London knowing exactly what she was doing: coming back in a sport that has always measured athletes not just by effort, but by timing.
On Tuesday, she and rising Canadian teenager Victoria Mboko made it clear they weren’t here for a feel-good exhibition. They beat New Zealand’s Erin Routliffe and Nicole Melichar-Martinez of the U.S. 7-6(2). 6-2 in women’s doubles. a straight-sets win with crisp serves and fast court craft that briefly shut down every question about whether Williams still had it.
But the moment didn’t just belong to tennis. It arrived with a second, louder story still hanging in the air—one that started last August, when Williams said she had been taking Zepbound, a drug from the GLP-1 family designed to treat diabetes and also known for helping people lose weight.
Just under a year earlier. the 23-time Grand Slam singles champion. then 44. told Oprah Winfrey that she didn’t want the “shortcut.” She said she decided to take Zepbound after trying “just about every other avenue. ” arguing that getting to where she wanted to be after her two pregnancies wasn’t working through training alone.
“I couldn’t beat the weight. It was the one opponent I couldn’t beat. ” Williams said. and she added that she manages her treatment through Ro. a telehealth company for which she serves as a paid ambassador. Charles Barkley—an NBA Hall of Famer and TV analyst—is also an ambassador for Ro. Williams’ husband. Alexis Ohanian. a founder of Reddit. is described as a major investor in Ro. which displayed adverts during the U.S. broadcast of her comeback match on Tennis Channel.
When Williams returned to competition last week, it also reopened another tension point: whether GLP-1s are turning into a new battleground for sport’s rules.
Williams’ comeback itself began to take shape last week. when she announced she would play doubles at one of the main tuneups for Wimbledon. a tournament she has won seven times. While no one expects the comeback to stop at Queen’s—or even with doubles—Williams has not directly committed to playing singles yet.
Her communication team did not agree to an interview for this story, including to explain her views on the debate over whether GLP-1s could be banned.
For now, the anti-doping position is specific. GLP-1s are being monitored by anti-doping authorities—an approach WADA has been running since 2024. They are not prohibited, and the drugs may never be.
WADA says there is “no timetable” for establishing whether GLP-1s are performance-enhancing. Tennis anti-doping protocol is managed by the International Tennis Integrity Agency (ITIA), and because tennis is an Olympic sport, WADA oversees its compliance with its code.
“The WADA List Expert Advisory Group has discussed their status, as well as other substances of the same class,” WADA said, adding that semaglutides and tirzepatides were added to the Monitoring Program to track patterns of use in sports in and out of competition.
WADA’s Monitoring Program includes substances not on the Prohibited List, but ones WADA “wishes to monitor” to detect potential misuse patterns.
The companies that manufacture these drugs are watching the debate closely too. Novo Nordisk. the pharmaceutical company producing and distributing GLP-1s. said it agreed with WADA’s monitoring decision. telling that it is “supportive of the WADA recommendation” and “strongly discourage use/promotion outside the indicated population and approved label.” Eli Lilly. another GLP-1 manufacturer and distributor. did not respond to messages seeking comment.
What makes the argument so sharp is how sport defines “advantage.” To land on WADA’s banned list. a substance must meet two of three criteria: it must have the potential to enhance sport performance. the potential to risk athletes’ health. and the potential to violate what WADA defines in its code as the “spirit of sport.”.
That “spirit of sport” standard is where the conflict lives. The anti-doping world is divided over whether that phrase is too vague—whether enforcement should be based on science alone. For now. WADA’s own process is still in motion. and it is still tracking the same question at the center of Williams’ story: does using GLP-1s function as a shortcut comparable to substances that alter detection or performance in ways anti-doping rules are built to stop?.
WADA has shown increasing concern about the role of weight-loss drugs in sports. Minutes from a meeting of WADA’s Health and Research Committee last August include discussion of “whether a new class addressing all types of weight management substances should be created. not only for weight category sports but also weight-sensitive ones (e.g. gymnastics, figure skating, cycling).”.
The fear described in that broader debate is that as companies develop GLP-1s to become faster-acting and more effective. athletes could use them to cut corners in training. In that scenario, the “spirit of sport” criterion could be triggered. The comparison being debated is also specific. Substances like diuretics are on the banned list because they can dilute urine and make it harder to detect actual performance-enhancing drugs through urine tests. But diuretics also play a role in other weight-based sports. helping athletes in boxing and mixed martial arts make weight before a bout.
GLP-1 drugs operate differently. They work more slowly, aiming for a more permanent result, with weight loss taking months. People who take GLP-1s report a significant reduction in “food noise,” the part of the mind that thinks about the next snack or meal. Less appetite can mean major weight loss.
And yet weight loss is not the whole equation for athletes. Fat loss is the main contributor, but studies of GLP-1 patients have shown muscle loss also occurs—an outcome that, for athletes, could do the opposite of enhancing performance.
The muscle-wasting effect has pushed scientists toward countermeasures. In 2023. VERU. a Miami-based pharmaceutical company. announced that one of its experimental drugs. Ostarine—also known as enobosarm—had shown early success in clinical trials to prevent muscle-wasting among elderly patients and people suffering from diseases such as cancer. VERU says it is currently conducting trials that could ultimately lead to Ostarine being used alongside GLP-1 drugs. described as adjunctive therapy. so patients don’t lose lean muscle. VERU also says this option would not be available to athletes. because Ostarine is on WADA’s Prohibited List and can be purchased in the black market.
Mitchell Steiner, chief executive of VERU, said in an interview: “It should be on the list and banned from sport because it’s very effective,” and “It’s a performance drug. Our job is to get the right indication and show the safety in a controlled setting.”
Even then, the question isn’t frozen. GLP-1 manufacturers may eventually tweak molecular structures to minimize muscle loss, which could shift how any performance-enhancement judgment is made.
Matthew Fedoruk, chief science officer at the U.S. Anti-Doping Agency (USADA). said: “I think what you’re going to start seeing is new products being introduced to the market that actually have less of those side effects. which then would be more advantageous for athletes.” He added that this is “a growing threat” that needs to be monitored closely.
If GLP-1s do become prohibited. athletes could apply for therapeutic use exemptions (TUEs). which allow a drug if it treats a legitimate medical condition and does not meaningfully enhance performance. The text of this debate also points to how exemptions work in practice: they can be common among endurance athletes who suffer from asthma and need to take low-grade steroids through an inhaler. In the case of GLP-1 drugs, the most likely exemption could be for diabetes.
Williams, meanwhile, has already made her own position part of public life.
Her comeback story is also tethered to how she moved in and out of the tennis conversation long before she picked up a racket again. In the months after giving birth to her second child in 2023, she faced questions about whether she would return. In an August 2022 essay in “Vogue” announcing her “evolving away” from tennis. Williams wrote that she didn’t have the opportunity to play with the freedom her friend Tom Brady had. referencing that Brady’s then-wife had three children during his career. which lasted uninterrupted—until he was 45 after one change of heart 12 months from the end.
Fitness stayed part of her routine. By last year, rumors circulated about a possible comeback, and in the fall her name appeared in the sport’s anti-doping testing pool, the first step toward a potential return.
Players who leave tennis and remove themselves from the pool must return for six months before being eligible to play in tournaments. Once a player is in the testing pool, they have to commit to being at a certain location for one hour each day and be subject to random drug testing.
In December, Williams took to social media to tell the world it was “much ado about nothing,” saying she was not coming back. A few months later, on “Today,” she dodged Savannah Guthrie’s questions about a return, but refused to take the chance to say it wasn’t happening.
Then, last week, her plans became real. Twenty-four hours after she and Queen’s Club announced the comeback, she released photos of herself in the bespoke Nike kits she plans to wear. On Tuesday, she played.
She cracked serves and whipped forehands and connected on touch volleys and overheads. She walked the court with the “majestic presence” that has long been her trademark. Her two daughters sat courtside, taking it all in with the thousands packed into the main stadium.
“I wish I had done this while I was still playing,” Williams told Winfrey about taking GLP-1s, when her comeback was still only an idea. “It would have made such a big difference for me and my career.”
Now, with the first match of her comeback complete, the sport’s wider reckoning has moved from debate to reality—because for the first time at this level, GLP-1s and performance are being discussed with Williams’ return as the backdrop.
Serena Williams GLP-1 Zepbound WADA monitoring program anti-doping Queen's Victoria Mboko doubles comeback Ro Oprah Winfrey International Tennis Integrity Agency ITIA