GLP-1 medications are transforming how many people approach weight management, but a growing question is emerging in sports science: what do they mean for performance? A dietitian who began using a GLP-1 noticed an unexpected shift in wearable data after 30 days, including lower heart rate variability and a slightly reduced VO2 max, even while training consistently.
What Researchers Are Seeing
At the Annual Conference of Sports Dietitians in New Orleans, performance specialists discussed how these medications are becoming more common among athletes and fitness-focused adults. Yet the science is still catching up. James Burns, a sports dietitian, said responses can vary widely: some athletes may benefit from improved body composition, while others see performance markers soften.
One peer-reviewed study in the American Journal of Physiology tracked 66 active adults using a GLP-1 for 12 weeks. The findings showed lower body mass, a modest rise in resting heart rate, and a drop in HRV. Greg Grosicki, the study's author and a research scientist at WHOOP, noted that these changes can appear within weeks and may matter to highly trained athletes who closely monitor recovery.
Fueling Still Matters
Experts emphasize that the biggest issue is not the medication itself, but the way it can reduce appetite and make it easier to underfuel. That can affect recovery, training quality, and focus. Sports dietitians recommend structured meal timing, intentional pre- and post-workout nutrition, and attention to nutrients such as vitamin D and vitamin B12.
For athletes, the message is clear: GLP-1s are not a shortcut, and performance goals still depend on smart nutrition, recovery, and monitoring. As research expands, wearables and clinical data may help define how these medications fit into modern training. The next phase of sports science may be shaped by how well medicine, nutrition, and performance data work together.