Weight-loss drugs known as GLP-1 receptor agonists, including Ozempic and Mounjaro, will not be banned by the World Anti-Doping Agency (Wada) for 2027, but they will stay on its monitoring list. This decision follows a meeting of Wada’s executive committee, which is still evaluating whether the drugs could enhance athletic performance or pose a risk of misuse in sports. The updated rules will take effect in January and are reviewed every year to ensure they remain current with developments in medicine and sports science. These drugs have gained popularity beyond elite sports, with high-profile figures like 23-time Grand Slam champion Serena Williams revealing she had used weight-loss medication during a break from professional tennis. Wada’s senior director for science and medicine, Professor Olivier Rabin, urged athletes to use such drugs only under medical supervision. "These medications cause significant changes in your body, and they can lead to serious side effects, especially for athletes," he told BBC Sport. He emphasized the need for caution, noting that the physiological effects seen in obese patients may not apply to non-obese, highly trained athletes. Semaglutide, the active ingredient in Ozempic and Wegovy, was added to Wada’s monitoring list in 2024, while Tirzepatide, found in Mounjaro, was recently included. To be banned, a substance must meet two of three criteria: the ability to enhance performance, health risks for athletes, or a violation of the spirit of sport. Wada is currently conducting studies to assess the effects of these drugs in conditions that mimic high-level athletic performance. Rabin explained that these studies are complex and take time to complete, as they require controlled environments and specific conditions. Weight-loss drugs may be particularly tempting for athletes in sports with weight categories, such as boxing, wrestling, and horse racing, where strict weight limits are enforced. However, Rabin noted that weight management is a concern across many sports, including long-distance running, cycling, and even those where physical appearance is important, like gymnastics and horse riding. While these drugs might help athletes achieve weight goals, they could also cause side effects like nausea, fatigue, and muscle loss, which could hinder athletic performance. Publicly, few athletes have discussed using weight-loss drugs. Serena Williams is one of the most notable exceptions, having spoken about her use of such medication after childbirth. She is also a spokesperson for Ro, a company that sells GLP-1 drugs, and her husband is an investor in the firm. A recent study by Loughborough University found that 12% of sports medicine physicians globally were aware of athletes using GLP-1 drugs without a medical need, highlighting the potential for misuse despite the drugs not yet being banned.