When a runner hires a coach for the first time, there’s usually a period of mutual discovery, and of getting to know each other. Clients share information about their training history and injury patterns. The more a coach knows up front, the better they can tailor a plan that supports their runner’s progress and prevents setbacks. But when Roch Pedida of Calgary began working with a coach in 2024, he left out one detail: he’d been using a weight-loss medication for more than a year.
For Pedida, the omission wasn’t about secrecy; he just didn’t think it was relevant. “Running is where I focus on building fitness,” he says. “Wegovy mainly affects appetite.” In his mind, the medication is a health tool, not a performance enhancer. The only real overlap is in fuelling. He is careful to make sure he eats enough to support recovery, even when the medication means his hunger cues are muted.
It’s a pragmatic approach, if a bit idealistic. In the running world, food and performance are very closely linked. On the shelves of serious runners, you’ll find titles like Eat, Race, Win by Stacy Sims, Racing Weight by Matt Fitzgerald and Run Fast, Eat Slow by Shalane Flanagan and Elyse Kopecky. These books don’t just offer recipes; they treat food as fuel, but nutrition is also an intrinsic part of their strategy for speed and endurance.
The emergence of popular weight-loss drugs such as Wegovy, Ozempic and Mounjaro have the potential to even the playing field for runners who struggle with weight issues. But the drugs also threaten to disrupt runners’ relationships with food, their bodies and their self-images. As the medications become increasingly popular (and are due to become cheaper in 2026, when generic versions will hit production), it’s important to consider the positives and negatives and to be realistic about the effects of these drugs on health and performance.
How they work
These GLP-1 receptor agonists (as they are referred to by clinicians) mimic GLP (glucagon-like peptide), a hormone that helps regulate insulin and appetite. They slow gastric emptying (the time it takes for food to empty out of the stomach), preserving that “full” feeling for longer, lowering appetite and improving blood glucose control. The first GLP-1 agonist, liraglutide, was approved for weight loss in the U.S. in 2014, but it was the approval of asemaglutide (under the brand name Wegovy) for weight loss in 2021 by Canada and the U.S. that kickstarted the widespread adoption of weight-loss medications.
GLP-1 drugs are now part of mainstream wellness culture; U.S. tennis superstar Serena Williams recently revealed that she lost 31 lb. using a GLP-1 medication. The drugs now dominate prescription TV ad spending in the U.S.
But their near-ubiquitous popularity raises questions about how they’re being used. For runners, who often walk the tight rope between optimal body composition and sustainable fuelling, the implications are complex. Can these drugs offer performance gains by helping users lose weight? Or are they a dangerous shortcut that risks undermining muscle growth, recovery and long-term health? And how do they intersect with broader cultural movements, such as fat positivity and digital health optimization (i.e. using digital tools to guide decisions about health)?
Does leaner equal faster?
Fast running has long been associated with leanness. The “lighter is faster” mindset permeates everything from elite training to recreational goals. For many runners, weight loss isn’t just about health; it’s about performance, and sometimes vanity. There’s a stigma around being a larger runner, and it’s sometimes self-imposed. Even when surrounded by the most supportive groups, there’s still an awareness that most of the people who take running seriously fit into a certain body type: lean. While being larger helps on snowy winter days when your group needs somebody to block the wind while running speed intervals, much running literature emphasizes weight management as an important aspect of performance.
A 2025 study published in the journal Sports Medicine found running economy is influenced by both the size of your body and how efficiently it moves. “Among these, body mass has a particularly significant impact on the energy cost of running,” it said.
Many larger runners know the ignominy of getting their team singlet, and realizing it was designed for someone with a smaller build. Fitness clothing is designed in either “athletic” or “loose” cuts, which some view as code for slim or heavy runners.
So when a solution like GLP-1 comes along, it’s tempting to see it as a shortcut to easier running and better performance. If a drug could help you take off 20 pounds, get you in better physical shape and help you reach your “race weight,” wouldn’t you take advantage?
GLP-1 drugs can offer real benefits for runners, especially those managing chronic conditions. Calgary’s Christina Saviskoff, a recreational runner in her 40s with diabetes, began using Ozempic after a sudden drop in both endurance and blood sugar control. “I had gained about 15 pounds, while my running dropped off,” she says.“ Ozempic helped stabilize my glucose and brought me closer to my original weight.”
Saviskoff’s use of a continuous glucose monitor revealed how exercise affects her blood sugar, helping her fine-tune her fuelling strategy. “I’ve learned some interesting patterns in what exercise does to my glucose levels,” she says.
But she’s quick to note that the medication isn’t a magic bullet. “I’ve had to focus on properly fuelling myself. That’s been a challenge.”
It should be noted that athlete-specific studies into the effects of the use of GLP-1 drugs have been limited. But psychologically, the boost can be profound. Serena Williams’s story reflects a broader trend: weight loss as a catalyst for renewed motivation and self-confidence. For overweight runners, GLP-1 drugs may offer a way tore-engage with their sport after setbacks.
Reward vs. risk
Digital health platforms are taking note. Apple Fitness and others are exploring how GLP-1 protocols can be integrated into personalized training plans, emphasizing muscle retention and recovery alongside weight loss—which brings us to one of the most significant concerns when using GLP-1s: the potential loss of lean muscle.
Dr. Stuart Phillips, professor of kinesiology at McMaster University, warns that up to 25 per cent of weight lost on GLP-1 drugs can be muscle. For runners, this is critical. “Even small reductions in muscle can reduce running economy, impair force production and hinder the ability to maintain pace,” Phillips says.
“Everyone thinks lighter equals better performance,” he goes on. “But there’s a limit. If you lose muscle, you lose power. Muscle loss can lead to slower recovery, increased soreness and higher risk of stress injuries. For runners, that’s a dangerous trade-off.”
The appetite suppression inherent in the medications can also make it difficult to meet your caloric needs, especially during high training loads. Saviskoff learned this the hard way. “The main dietary effect is reduced portion size,” she says, “so I’m making sure what I eat is better quality and more balanced. I learned a hard lesson a few times, when I didn’t eat following a long run because the thought made me feel ill, and then I ‘crashed.’” Now, she pre-plans her post-run meals, to ensure proper recovery.
Chronic underfuelling can also lead to Relative Energy Deficiency in Sport (REDs), a syndrome that occurs when athletes don’t eat enough to keep up with their training and daily energy needs. As Phillips warns, REDs can impair hormonal function, bone health and immune response.
After stabilizing her glucose, Saviskoff was diagnosed with anemia, highlighting how intertwined these issues can be. “I still need longer recovery from what should be easy runs,” she says.
GLP-1 drugs may also cause other side effects, among them nausea, gastrointestinal issues and fatigue.
Do GLP-1s reinforce stigma?
When it comes to weight loss medications, there are also cultural considerations. Some view using GLP-1s as promoting “thinness culture” and eschewing the gains made by the fat-positivity movement, which encourages people to love their larger bodies. Fat positivity challenges traditional metrics like BMI (body mass index) as a measure of health, and promotes advocacy against stigma.
Some experts, such as Dr. Sanjeev Sockalingam, strive to reconcile the positive impact of such movements with the medical implications of obesity. Sockalingam holds a number of positions, including senior vice president of education and chief medical officer at Toronto’s CAMH (Centre for Addiction and Mental Health); vice chair and professor of psychiatry at the University of Toronto; and scientific director at Obesity Canada. His work encompasses both the mental-health aspects of weight issues and their physical ramifications. He cautions that the emotional bene-fits of self-acceptance shouldn’t come at the expense of ignoring the physical impact of obesity. “Obesity, defined as a chronic medical condition where excess fat impairs health and organ dysfunction, is a medical model,” he says.
At the other extreme, as he points out, are those who call out weight-loss drugs as hacks or shortcuts, implying that people who use them aren’t willing to do the hard work necessary to lose weight. Sockalingam mentions The Biggest Loser—the reality show that gamified extreme weight loss. “That show really reinforces that it’s all about diet and exercise,” Sockalingam says. “‘Burn off 6,000 calories a day, and you’ll be fine.’ Of course, that’s insane.”
The show, which ceased production in 2020, shored up the shame and stigma surrounding weight gain and the difficulty of weight loss, while masquerading as health programming. “If you have weight problems, you should fix it yourself, because you let this happen,” is how Sockalingam sums up its ethos. “Would you say that to someone with diabetes or arthritis, to just get over it? Of course not.”
This is where self-image in the running world butts up against the reality of obesity. In a sport full of people who like to spout mantras such as “we know it’s hard, that’s why we do it,“ and in which doping is so pervasive that we question world records the moment they are set, GLP-1s may be seen by some as just another form of doping.
Those arguments, Sockalingam says, are barking up the wrong tree. Obesity is a chronic medical condition, and has been treated by medical professionals as a disease for more than a decade; he draws a parallel with depression, which was long viewed as a personal weakness, but is now recognized as a medical condition that can’t be self-treated. Obesity should be looked at the same way, he says.
GLP-1s as performance enhancers
Research gaps remain. The World Anti-Doping Agency (WADA) is watching closely. Semaglutide, Ozempic’s active ingredient, is now on its monitoring list—substances that are not on the WADA Prohibited List, “but which WADA wishes to monitor in order to detect potential patterns of misuse in sport.”
Phillips says there is a pressing need for controlled trials investigating GLP-1 use in endurance athletes. He’d like those tests to focus on changes in body composition and effects on performance metrics, such as VO2 max and running economy, as well as recovery and injury incidents. He also thinks trials should look at strategies to mitigate lean mass loss, and examine sex-specific responses, since GLP-1 medications are hormonal in nature and can impact people in different ways. “We need to under-stand how these drugs affect performance metrics,” he says.
In reality, the likelihood of using GLP-1s as performance enhancers is slim. In addition to the potential muscle loss and side effects such as nausea, the drugs are only effective when users have the disease they’re intended to treat. A runner without excess fat or adipose tissue who uses GLP-1s is likely to lose weight from the wrong places and see a decline in performance.
“I’m sure many runners with excess weight or obesity see the appetite suppression as a plus; it’s what the drugs are intended to do, after all,” Phillips says. “I think the good outweighs the bad. But if you are using the drug without a health need, that’s never a good idea, in my opinion.”
In addition, athletes who are serious enough to be looking for performance-enhancing tricks are likely to be focusing on tactics that can improve each element of their training. With the challenges around appetite, fuelling and muscle loss, weight loss drugs could have a negative impact on the areas athletes are looking to fine-tune.
So, what do GLP-1 medications mean for runners? They offer opportunity in the form of improved health and weight control. For some, they unlock a return to movement after years of struggle. But they also pose challenges: muscle loss, under fuelling and injury risk are real concerns.
For runners like Pedida, progress still comes down to one simple element: time on feet. “Over the past year, I’ve definitely lost weight, and I’m fitter and faster than I was a year ago,” he says. “Wegovy has played a role in that weight loss, but whether it directly made me a faster runner is harder to say. Running progress still comes down to putting in the miles, being consistent and listening to my body. The medication has supported my health, but my running gains have really come from the training itself.
Strategies for runners using GLP-1 drugs
Strength Training: Experts recommend resistance training at least twice weekly, focusing on hips, hamstrings, quads and core.
Protein Intake: Aim for at least 1.6 grams per kilogram of body weight per day. Quality matters, especially when appetite is low.
Meal Timing: Fuel before you experience hunger cues .Plan your post-run meal ahead of time.
Monitoring Tools: Use body composition scans and glucose monitors or glucose meters to track progress.
Medical Oversight: Avoid compounded drugs, which could contain active ingredients that haven’t been approved for weight loss. Work with health-care providers to adjust dosages and monitor health markers.
Andrew McKay is a Toronto runner and freelance writer.
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