Popular diabetes drug could block exercise benefits, new study warns

A common diabetes drug could dampen some of the key benefits of exercise, a new study has found.

Researchers from Rutgers University discovered that adults who took metformin, a widely used generic medication for type 2 diabetes, while exercising saw smaller improvements in blood sugar control, blood vessel function and aerobic fitness than those who exercised without the drug.

Published last month in The Journal of Clinical Endocrinology & Metabolism, the findings add to growing evidence that although both metformin and exercise improve blood sugar control and heart health, combining them may dull some of exercise’s benefits. 

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“Metformin is the most widely used glucose-lowering medication used around the world,” said Steven Malin, lead study author and a professor in the Department of Kinesiology and Health at Rutgers’ School of Arts and Sciences. 

“However, it is not clear that taking both of these treatments together is best,” he told Fox News Digital. “If they are not, people could notice that energy levels may be low and/or their health is not getting better. This could lead to ‘psychological defeat,’ so to speak, and impact overall wellness and quality of life.” 

Nearly 35 million Americans have type 2 diabetes, according to the Centers for Disease Control and Prevention, and millions more worldwide take metformin for blood sugar control or experimental anti-aging uses, according to experts.

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The 16-week, double-blind trial followed 72 adults at risk for metabolic syndrome, a group of conditions including high blood pressure, high blood sugar and excess body fat that increase the risk of diabetes and heart disease. Participants were split into four groups, with two performing high- or low-intensity exercise with a placebo and two performing the same workouts on 2,000 milligrams of metformin daily.

Participants also saw less reduction in inflammation and fasting glucose levels.

At the end of the study, those who exercised without the drug showed clear improvements in vascular insulin sensitivity, meaning their blood vessels responded better to insulin and allowed more oxygen and nutrients to reach muscles. But when metformin was added, those gains shrank. Participants also saw less reduction in inflammation and fasting glucose levels.

Researchers aren’t certain why, but they believe metformin may interfere with the body’s ability to adapt to exercise on a cellular level.

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Malin said it may relate to blood vessel health. “Improved blood vessel function is key for delivering nutrients to tissues, like sugar,” he explained. “If the sugar cannot be delivered to the tissue, this might explain why muscles cannot use the sugar for energy as well in response to insulin.”

Researchers noted the study was small and focused on adults at risk for metabolic syndrome, meaning the results may not apply to everyone with diabetes.

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The researchers stressed that people should not stop taking metformin or exercising, but instead discuss the findings with their doctors to ensure they’re getting the best combination of treatment and activity.

The researchers said future studies should explore how to preserve the benefits of both treatments, and the Rutgers team is now testing whether metformin interacts differently with resistance or strength training and whether adjusting dosage or timing could reduce the effect.

Dr. David Cutler, a board-certified family medicine physician at Providence Saint John’s Health Center in California, told Medical News Today that while the results seem discouraging, they need to be placed in context.

“The small decline in vascular insulin sensitivity needs to be weighed against the great benefit from lowered blood sugar levels achieved with metformin,” said Cutler, who was not involved in the research. “The lowering of blood sugar results in lower risks of all diabetic complications like heart attack, stroke, kidney failure, blindness and amputation.”

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Cutler added that the results shouldn’t influence diabetics who rely on metformin, but may be more relevant to people who use the drug for other reasons, such as anti-aging, polycystic ovary syndrome or cancer prevention.

“For now, metformin should remain the first-line medication for treating type 2 diabetes,” he said.

Fox News Digital has reached out to metformin manufacturers and the American Diabetes Association for comment.