Could GLP-1 Weight-Loss Drugs Give Athletes a Performance Boost?
GLP-1 medications have become widely known for helping people lose weight and improve aspects of their health. But as their popularity grows, sports scientists and anti-doping experts are beginning to ask a different question: could these drugs also affect athletic performance?
The debate has gained additional attention following comments from tennis legend Serena Williams, who has spoken publicly about using tirzepatide after struggling to lose weight following pregnancy.
Tirzepatide, sold under brand names including Zepbound and Mounjaro, works by mimicking hormones involved in regulating appetite and feelings of fullness.
For athletes, however, the issue is more complicated than simply losing weight.
Are GLP-1 drugs considered doping?
At present, GLP-1 medications are not prohibited in professional sport.
The World Anti-Doping Agency (WADA) does, however, monitor GLP-1 receptor agonists, including drugs such as semaglutide and liraglutide. Monitoring does not mean that the substances are banned, but it allows anti-doping authorities to track their use and look for potential patterns of misuse.
Experts say there is currently not enough evidence to conclude that GLP-1 drugs directly enhance athletic performance.
One major problem is the lack of research involving elite athletes. Most studies have focused on people with obesity, diabetes or other health conditions rather than highly trained competitors.
Could weight loss provide an advantage?
The potential advantage may be particularly relevant in sports where athletes compete according to weight.
Boxing and wrestling, for example, require competitors to remain within specific weight categories. A medication capable of helping an athlete lose several kilograms could potentially make it easier to reach a particular division.
That is one reason scientists believe the issue deserves closer examination.
However, simply weighing less does not automatically mean an athlete will perform better.
The muscle-loss problem
GLP-1 medications can lead to substantial weight loss, but some of that reduction can involve lean body mass, including muscle.
That could be a serious disadvantage for athletes because muscle is essential for strength, speed, endurance and injury prevention.
Research cited by scientists suggests that the proportion of lean mass lost can vary between medications. Maintaining resistance training and adequate protein intake may help reduce muscle loss, although researchers are still studying the long-term effects.
GLP-1 drugs may have benefits beyond weight loss
The debate becomes even more complicated because researchers have found that GLP-1 medications can influence the body in ways that go beyond reducing appetite.
Studies have linked these drugs with improvements in metabolic health and cardiovascular outcomes, while researchers are also investigating their effects on inflammation and blood flow.
Some scientists believe these changes could theoretically influence exercise recovery or performance.
But there is an important caveat: there is currently no strong evidence showing that GLP-1 drugs improve performance in healthy elite athletes.
As one expert noted, the absence of evidence does not necessarily prove that there is no effect — it simply means the science has not yet provided a clear answer.
Could the drugs actually hurt performance?
There is another side to the debate.
Because GLP-1 medications suppress appetite, athletes taking them could struggle to consume enough food to meet the enormous energy demands of intensive training.
Sports scientists refer to inadequate energy intake as under-fuelling, a problem that can affect recovery, training adaptation and competitive performance.
In severe cases, insufficient energy availability can contribute to Relative Energy Deficiency in Sport (RED-S), which can affect bone health, mood and physical performance.
For an elite athlete, losing weight may therefore provide little benefit if it comes at the expense of adequate nutrition and muscle mass.
Serena Williams adds another dimension to the debate
Serena Williams has publicly discussed her experience with a GLP-1 medication and has described improvements in areas including her weight, joints and cardiovascular health.
She has also said that the medication helped her perform movements that she previously found difficult.
Williams has presented her experience as part of a wider effort to reduce the stigma surrounding weight-loss medications.
But her status as one of the world's most recognisable athletes has also raised concerns among some experts that her use of these drugs could influence younger athletes and encourage people who do not medically need them to consider medication as a shortcut to changing their bodies.
What happens next?
For now, GLP-1 medications remain legal in professional sport, and there is no scientific consensus that they should be classified as performance-enhancing drugs.
However, their increasing popularity means the issue is unlikely to disappear.
Sports authorities will need more research involving elite athletes to determine whether these medications can genuinely provide a competitive advantage — or whether their potential risks, including muscle loss and under-fuelling, could actually make performance worse.
For athletes, the question may ultimately be less about how much weight they can lose and more about whether the medication helps or harms the balance between nutrition, muscle, recovery and performance.
The bottom line
GLP-1 drugs are not currently considered doping, but scientists are watching closely. Their effects on weight, metabolism, inflammation and appetite could theoretically influence athletic performance, yet there is still not enough evidence to say whether they offer athletes a genuine competitive advantage.
Keywords: GLP-1 drugs, weight loss drugs, athletic performance, performance enhancing drugs, doping, Serena Williams, tirzepatide, semaglutide, athletes, WADA, sports medicine, weight loss, Ozempic, Mounjaro, Zepbound, sports health