Metformin is a first-line medication used to treat type 2 diabetes, widely prescribed to manage high blood sugar and lower cardiovascular risk. But recent research published in The Journal of Clinical Endocrinology & Metabolism suggests it may interfere with the benefits of exercise. A new study explored whether metformin affects vascular insulin sensitivity depending on exercise intensity in adults at risk for metabolic syndrome.
Vascular insulin sensitivity determines how effectively blood vessels respond to insulin, which helps regulate blood sugar after meals. When blood vessels respond properly, they dilate and deliver oxygen, nutrients, and hormones like insulin to muscles and other tissues.
In the study, researchers looked at 72 adults at risk for metabolic syndrome over a 16-week trial. Participants were randomly assigned to low- or high-intensity exercise over the trial, paired with either 2,000 milligrams of metformin daily or a placebo. They tracked vascular insulin sensitivity, blood sugar, inflammation markers, VO2 max, and body composition.
Results showed that exercise alone improved aerobic fitness and vascular insulin sensitivity regardless of intensity. Those taking metformin, however, showed no increase in VO2 max and smaller improvements in both large and small blood vessel function.
“If you exercise and take metformin and your blood glucose does not go down, that’s a problem,” said Steven Malin, PhD, kinesiology professor at Rutgers University and lead author of the study. “People taking metformin also didn’t gain fitness. That means their physical function isn’t getting better and that could have long-term health risks.”
It’s not totally clear why metformin impacts the benefits of exercise. Metformin partially blocks mitochondrial function, which helps control blood sugar but may also prevent the cellular changes exercise triggers, including better aerobic capacity and mitochondrial health.
Overall, the study concludes that metformin may limit some of the vascular and metabolic benefits of exercise, affecting both large arteries and small capillaries. The findings highlight a growing need to evaluate how drugs may impact lifestyle and long-term health outcomes.
“We need to figure out how to best recommend exercise with metformin,” Malin said. “We also need to consider how other medications interact with exercise to develop better guidelines for doctors to help people lower chronic disease risk.”
Diabetes Drug May Limit Exercise Benefits, Study Says
