The World Anti-Doping Agency Still Won't Ban GLP-1 Drugs

The World Anti-Doping Agency's executive committee met in Belgrade last month, reviewed whether to add GLP-1 drugs to its list of banned substances for 2027, and said no — for the second year in a row, even as its own science director admits athletes are almost certainly already using them.

What WADA decided

WADA's executive committee approved the 2027 Prohibited List on September 10, with the full list taking effect January 1, 2027, according to Athletics Illustrated and The Barbell Spin. Semaglutide and tirzepatide — the GLP-1 receptor agonist class behind Novo Nordisk's and Eli Lilly's weight-loss and diabetes drugs — stay off it. Instead they remain on WADA's Monitoring Program, a separate watch list for substances the agency tracks for patterns of misuse without punishing anyone for using them. Semaglutide was added to that list in 2024; tirzepatide followed in 2026.

Olivier Rabin, WADA's senior director of science and medicine, said the agency's expert group looked at the literature and concluded "there is insufficient evidence to conclude with confidence" that GLP-1 drugs meet the criteria for a ban. Two research efforts are already underway to close that gap, he said: "We anticipate that these studies will provide the data needed to make a firm decision." One of them, led by exercise physiologist Morten Hostrup in Copenhagen, is a randomized trial tracking roughly 40 high-level endurance runners on a GLP-1 drug over four and a half months, measuring 5K times, muscle mass and mental state — the first study of its kind in trained athletes rather than people with obesity or diabetes, according to Washington Post reporting syndicated by the Anchorage Daily News. Results are expected in about a year.

Why a weight-loss drug could plausibly count as doping

A substance only lands on WADA's banned list if it meets two of three tests: it enhances performance, it poses a health risk, or it violates the "spirit of sport." GLP-1 receptor agonists slow digestion and suppress appetite, which is why they produce weight loss in the first place — but that same mechanism is exactly what would matter to an athlete trying to make a weight class, qualify for a lighter boxing division, or shave grams in a judged or aesthetic sport. The math is also different at the elite end: an average person might need to lose roughly 10% of their body weight to notice a change, while a professional runner might only need to shed a pound or two to feel the difference, Daniel Drucker, a University of Toronto endocrinologist who helped discover the GLP-1 hormone pathway decades ago, told the Post. Oliver Catlin, president of the testing firm Banned Substances Control Group, put it more bluntly about a retired athlete who has discussed using the drugs publicly: "That's an athlete who's literally experiencing the performance-enhancing benefits of it as we speak."

A survey of 114 sports medicine physicians across 38 countries and 93 sports, published in the journal Sports Medicine by a Loughborough University team, found the physicians had already seen this play out: reported use clustered in weight-sensitive sports like cycling, aesthetic sports like artistic swimming, physique sports like bodybuilding, and endurance sports like swimming. Twelve percent of the physicians said they were aware of athletes using GLP-1 drugs with no medical need for them, and lead researcher Daniel Read told the Post he suspects the real number is higher, since physicians can only report what they happen to find out about.

What's actually known versus what isn't

The physician survey measures perception, not performance — it tells you sports medicine doctors are worried, not whether the drugs make anyone faster or stronger. On the actual physiology, the evidence cuts in different directions. Trials in people with obesity have found that 25% to 39% of the weight GLP-1 drugs remove is lean muscle mass, not fat — a trade an athlete in a power or speed sport would want no part of. Forty-four percent of the surveyed physicians said they thought GLP-1 drugs should eventually be banned in sport; 38% were unsure, and the researchers' own recommendation was education and monitoring over an immediate ban. Drucker's summary of the state of the science was unambiguous: "There's just insufficient data to come down on either side of this."

There's also a detection problem that has nothing to do with whether the drugs work. Synthetic GLP-1 compounds clear the body within hours to weeks depending on the version, which means a short-acting one could in principle be timed around a competition's testing window. A separate research effort, described in the same Post report, is trying to get around that by looking for a chemical marker left behind by how these drugs are manufactured, rather than testing for each specific compound — an approach its lead researcher expects is roughly two years from working. Stuart Phillips, a kinesiology professor at McMaster University, told the Post that use will likely keep climbing regardless: "Athletes are currently using them, and will probably begin to use them more and more until somebody tells them that they can't."

What this means for researchers

GLP-1 drugs join a long list of substances that reached wide real-world use well before anyone generated the controlled data needed to say what they actually do in the specific population — trained, healthy, highly motivated athletes — that regulators are being asked to rule on. The Journal has covered that evidence gap before in a broader form: most peptide research still happens in animals, and a finding in mice or in people with obesity doesn't automatically transfer to a different body under different stress. Here it's the same structural problem in miniature, playing out in real time on a regulator's own calendar — WADA reviews its list every September, which means this exact question comes back up again next year regardless of whether the Copenhagen trial or the detection work has finished.

For now, the rule in writing is a prescription and an honest answer about why it was written. Torrey Labs' compound guide covers how GLP-1 receptor agonists work in more detail; what remains unresolved — and will stay that way until the data WADA is waiting on actually exists — is what happens when the same drug is taken by someone the rule wasn't written for.