Weight loss drugs in sport — WADA’s watchlist, performance trade offs & what athletes need to know

GLP-1 drugs like Ozempic and Mounjaro have recently made waves in sport with elite athletes — including former tennis player Serena Williams — bringing attention to their use. Originally developed for diabetes and weight management, these medications are now part of a broader conversation about performance, recovery and regulation.

While GLP-1s haven’t been banned by the World Anti‑Doping Agency (WADA), they’re being actively monitored. This is a formal step used to track substances that might enhance performance, pose health risks or undermine the spirit of sport. That status matters because labs are already looking for patterns of use and — if evidence of abuse emerges — GLP‑1 drugs could shift from ‘watched’ to ‘prohibited’ in a future ‘Prohibited List’ update.

Here, Georgina Rothwell, Thorrun Govind and Catherine Forshaw explore what’s known, what’s emerging and what athletes need to consider as interest grows and scrutiny intensifies.

Why sport is watching Ozempic

Ozempic is the brand name for semaglutide — a GLP‑1 receptor agonist originally designed for type 2 diabetes. At higher doses, it was later approved for chronic weight management. In simple terms, semaglutide helps the pancreas to release insulin when needed, suppresses glucagon, slows gastric emptying and reduces appetite. These effects improve metabolic control and make it far easier to maintain a calorie deficit.

This is why endurance and weight‑sensitive sports are paying attention. Less body mass can mean a better power‑to‑weight ratio without living in a constant state of hunger that typically comes with cutting weight. It’s a clear performance incentive which is precisely why WADA placed GLP‑1s on its ‘Monitoring Program’. 

Why athletes are considering GLP-1s

Health improvements

When used for their intended medical purposes, GLP-1 drugs can deliver substantial health benefits. Athletes who meet clinical criteria may see better glycaemic control, improved cholesterol and triglycerides and lower rates of major adverse cardiovascular events. For master athletes or those with metabolic issues, that can be life‑changing in the long run. 

However, these benefits are documented in therapeutic contexts with medical oversight. Translating them directly into safe performance gains isn’t automatic. 

Competitive advantages

The most compelling sport‑specific draw is improved relative power. If your ‘engine’ stays the same while the ‘chassis’ gets lighter, climbing and long‑course economy can improve. That’s why some swimmers, cyclists and triathletes are discussing the use of GLP‑1s and why WADA’s science leadership has publicly flagged possible advantages based on weight‑to‑power dynamics. 

It’s important to note that these advantages aren’t universal. Sprint power, repeated accelerations and collision resilience depend heavily on lean mass. If your weight loss includes muscle (and for many athletes, it does), the net effect can be neutral — or even negative. 

Side effects that shape performance

Athletes often experience two very different realities on GLP‑1s. On one hand, appetite suppression and steadier blood sugar can make it easier to stay in a small, consistent energy deficit without the mood swings and constant cravings that sabotage dieting. 

On the other hand, a meaningful portion of weight loss can be lean tissue — especially when protein intake and resistance training aren’t carefully protected. This erodes peak power, repeatability and injury resilience. 

In addition, slowed gastric emptying raises the odds of nausea, reflux and an unsettled stomach during hard training and racing. This can derail in‑race carbohydrate plans and — over time — push you towards low energy availability and relative energy deficiency in sport (RED‑S). The result is a classic short‑term/long‑term trade‑off — while it may be easier to get lighter, you can become a lot less durable if the basics aren’t nailed. 

Half‑life, washout & why timing matters

Semaglutide has a half‑life of roughly a week. While this means that it’s great for once‑weekly dosing, clinically relevant levels linger for weeks after you stop. With albumin binding and slow clearance, it can remain in your system for about five weeks following the final injection. 

From a practical standpoint, the fact that semaglutide stays in your system for weeks after the last dose affects how you should plan your training and competition. It can influence when side effects like nausea or gastric discomfort show up during key sessions and it limits your flexibility if you need to stop before a major event or respond quickly to changes in anti-doping rules.

Permitted use, concentrations & how it shows up in tests

Semaglutide isn’t currently on WADA’s Prohibited List so there are no threshold concentrations or decision limits to worry about right now — just having it in your system isn’t an anti‑doping rule violation. That said, WADA’s strict liability principle still applies to prohibited items and substances can move from monitored to banned if evidence justifies it. Stay alert to that possibility each January when the new List and Monitoring Program are released. 

If you have a legitimate medical need, speak to your team doctor and your anti‑doping organisation about a Therapeutic Use Exemption (TUE) and keep pristine documentation. 

On detection, semaglutide behaves differently from many classic doping agents. Very little of the intact drug molecules appear in urine so anti‑doping labs focus on blood tests. This includes dried blood spots (DBS) and use liquid chromatography–mass spectrometry to detect the modified peptides. WADA has specifically funded method development for GLP‑1 agonists like semaglutide, liraglutide and tirzepatide (more commonly known as ‘Mounjaro’), reflecting the interest in targeted surveillance as usage grows. In practice — if a lab looks for it — semaglutide can be found in blood for weeks due to its pharmacokinetics. 

What recent reporting & sport‑specific chatter tell us

Mainstream and specialist outlets have chronicled the tension between potential advantages and risks. Triathlon and endurance publications have highlighted rapid weight drops alongside improved lab markers — but they also report that athletes are battling gastrointestinal issues at intensity and struggling to fuel long efforts. This is a deal‑breaker in marathon, long‑course triathlon or stage racing. 

Meanwhile, sport pages have documented the cultural pressure around leanness in cycling and the broader conversation sparked when elite athletes like former professional tennis player Serena Williams have discussed GLP‑1 use. All of this has sharpened WADA’s focus on whether use in elite circles is drifting from therapy into abuse. 

Where this could be headed

WADA’s monitoring isn’t just a formality — it’s a data‑gathering step that’s preceded prohibition for other substances when patterns of abuse became clear. Detection methods for GLP‑1s in blood and DBS are improving and anti‑doping organisations are steering athletes towards authoritative medication status tools rather than social media lore. 

For athletes, the strategic question isn’t simply “does a lighter body help?” but “can I stay fast, fuelled and robust while managing the side effects — and do so within rules that might tighten?” The answer varies by discipline, physiology and support structure but the common thread is that performance still rests on adequate energy availability, muscle function and reliable gastrointestinal tolerance on race day. Drugs don’t change those fundamentals. 

Talk to us

Our sports law team is widely recognised as one of the most experienced and multidisciplinary groups in the industry, advising athletes and organisations on complex regulatory issues. 

With specialists in anti-doping compliance — including UK Anti-Doping (UKAD) Accredited Advisor Catherine Forshaw and practising pharmacist and trusted national health commentator Thorrun Govind — we provide clear, practical guidance on WADA rules, TUEs and the evolving status of substances.

If you need advice on permitted use, monitoring requirements or risk management, get in touch today for a confidential consultation by calling 0333 004 4488, emailing hello@brabners.com or completing our contact form below.