Could Weight-Loss Drugs Give Athletes an Unfair Edge?
As tennis star Serena Williams returns to professional competition after revealing she used a GLP-1 weight-loss drug, scientists and anti-doping experts are debating a question with no clear answer yet: could these drugs, designed to treat obesity and diabetes, also hand athletes a competitive advantage?
Williams told Oprah Winfrey’s podcast last year that despite training “eight hours a day in the gym,” she could not shift post-pregnancy weight: “The one opponent I could not defeat is the weight… I feel like I may have even gained weight.” She later told Vogue she had used tirzepatide, sold as Zepbound and Mounjaro, and has since become a paid brand ambassador for the company Ro, which administers the drug; her husband, Alexis Ohanian, holds a financial stake in that company. GLP-1 drugs work by mimicking gut hormones that trigger feelings of fullness, suppressing appetite and driving substantial weight loss.
Not yet classified as doping
David Cowan, an anti-doping specialist at King’s College London, says a substance only counts as doping if it enhances performance, endangers an athlete’s health, or breaches the “spirit of sport.” Weight-loss drugs are not currently banned, though the World Anti-Doping Agency keeps them on its monitoring list “to detect potential patterns of misuse in sport,” according to a Wada spokesperson. Cardiologist Massimo Mapelli, of Milan’s Centro Cardiologico Monzino, notes that GLP-1s simply haven’t been studied in elite athletes: “Things are rapidly evolving and what we have considered normal until now is changing.”
The clearest risk area may be combat and weight-class sports. In boxing and wrestling, where athletes must hit specific weight limits, Mapelli says use of the drugs “could be considered doping” because, in his words, “you’re essentially taking a drug that could give you an advantage” — comparable to the long-standing ban on diuretics used to shed water weight quickly.
Beyond weight loss itself, researchers have found GLP-1 drugs lower inflammation and cut cardiovascular risk through mechanisms only partly explained by lost pounds — one Lancet analysis found weight loss accounted for just a third of the reduced heart-attack and stroke risk. Endocrinologist Daniel Drucker of the University of Toronto, who helped pioneer the drugs, says these added effects deserve scrutiny; Williams herself has credited the medication with a 19% drop in cardiovascular risk and says “I can pull moves I could, quite frankly, never do before.” Drucker, who consults for drugmakers, speculates the drugs could make “the metabolic environment more efficient for exercise” by improving blood flow and organ health, though he stresses there is no proof either way: there’s “no data to suggest they’re performance-enhancing, but absence of evidence is not evidence of absence.”
Exercise physiologist Abbie Smith-Ryan, of the University of North Carolina, argues that any inflammation benefit would likely show up first in athletes who are overweight, not already-lean competitors, and that exercise itself “outperforms the drug” at lowering inflammation. She and others see a bigger danger in appetite suppression undermining the huge calorie intake elite athletes need to train and recover, potentially triggering Red-S, a condition linked to poor bone health, mood disturbance and declining performance. Side effects including muscle loss and gastrointestinal problems are also well documented, though specialists such as Michael Joyner of the American College of Sports Medicine say disciplined training could offset muscle loss and that shedding even a few kilos can be “transformative” for speed and endurance at the elite level.
Drugmakers Novo Nordisk and Eli Lilly both say their medicines are intended strictly for approved conditions like type 2 diabetes and obesity, and neither commented on athletes’ use of them. With the drugs easily obtained through private prescribers online, Joyner suggests it could ultimately strike rivals as unfair if some athletes gain an edge through medication rather than lifestyle changes alone.
Source: BBC News