Coach Patrick Mouratoglou Says He and Serena Williams 'Had a Few Fights' Over Postpartum Weight After Star Disclosed GLP-1 Use

Patrick Mouratoglou, Serena Williams’ longtime coach, said he and the 23-time Grand Slam champion argued about her weight after she became a mother and during her efforts to return to elite competition, comments that followed Williams’ recent disclosure that she has used a GLP-1 weight-loss medication.

Mouratoglou, who coached Williams for part of her late-career comeback and helped her win 10 of her 23 major singles titles, told NBC’s Today that he remembers “a few fights” with Williams over her post-pregnancy weight. He said his concerns were focused on performance and injury risk, not appearance, and noted that even small changes in body mass can affect movement at the highest level of tennis.

"Tennis is a sport in which you can't afford to be overweight," Mouratoglou said. "First of all, the pressure on your joints and everything is so big that your chances become much higher. The second thing is it's a sport in which you change directions all the time and with a lot of speed. Even one kilo overweight is a lot." He added that Williams, older than many competitors during her attempted comebacks, faced additional challenges in regaining pre-pregnancy form and reducing injury risk.

Williams, 43, publicly revealed in recent interviews that she has been using Zepbound, a glucagon-like peptide-1 (GLP-1) receptor agonist, as part of a weight-loss program. She said the medication helped her lose about 31 pounds over the past year and that it complemented the healthy habits and training she maintained as a former world No. 1. Williams told People she had experienced difficulty returning to a previous weight despite intense training and a healthy diet after the birth of her first daughter, Alexis Olympia, in 2017, and again after her second daughter, Adira River, in August 2023.

GLP-1 medications, approved for treatment of type 2 diabetes and for chronic weight management in certain formulations, work on pathways that help regulate blood sugar and appetite. Popular brand names in this class include Ozempic, Wegovy and Mounjaro; Zepbound is another formulation that has been prescribed for weight loss. Williams said the drug left her feeling "physically and light mentally," reduced joint pain and made her feel more active.

Mouratoglou said Williams sometimes interpreted his comments as judgment about her appearance. "I remember she did not like when I said that because she thought I was judging her," he said. "But I kept telling her, I don't care about your look. It's not my job. My job is your tennis. If you want to come back to the top and make history, then we have to be very efficient on every level — including this one, which for me was the key element."

Williams has been a prominent public figure both for her on-court achievements and off-court advocacy and business activities. She spent 319 weeks as world No. 1 and has the most Grand Slam singles titles in the Open Era for a female player. Her last competitive match was at the 2022 U.S. Open, where she lost a three-set match to Ajla Tomljanovic.

Williams also disclosed that she consulted Ro, a health-care company for which she is a paid spokesperson and in which her husband has invested, when seeking guidance about GLP-1 medication. She said she had experienced periods of rapid weight loss followed by plateaus despite maintaining a professional athlete’s training and diet, prompting her to explore medical options to reach a weight she felt was necessary for performance and comfort.

Medical specialists and professional sports organizations have in recent years discussed the implications of GLP-1 use among athletes and the general public, noting the medications' clinical indications, potential side effects and the importance of medical supervision. Williams described her decision as part of a broader health plan implemented under medical guidance and framed the medication as supporting, rather than replacing, established fitness and nutrition practices.

Mouratoglou’s comments highlight tensions that can arise when athletes reconcile personal health, body changes after pregnancy and the physical demands of elite sport. He said his priority in conversations with Williams was optimizing her on-court efficiency and protecting her long-term physical well-being, concerns that informed his remarks and the disagreements he recalled.

Both Williams’ disclosure about GLP-1 use and Mouratoglou’s account underscore how postpartum weight and medical options to address it intersect with athletic performance, athlete privacy and public conversation about emerging therapies in weight management.