A widely prescribed diabetes drug might be undermining the health improvements patients typically gain from regular physical activity, according to new research.
Metformin appears to diminish the usual benefits of exercise—including improvements in blood pressure, cardiovascular fitness, and blood sugar regulation—researchers reported in The Journal of Clinical Endocrinology & Metabolism.
These findings challenge existing medical guidelines that recommend patients with elevated blood sugar take metformin while maintaining an exercise routine, based on the assumption that combining two effective treatments should produce superior results.
Lead researcher Steven Malin, a professor of kinesiology and health at Rutgers University-New Brunswick in New Jersey, explained in a news release: “Most health care providers assume one plus one equals two. The problem is that most evidence shows metformin blunts exercise benefits.”
How Metformin Works
According to Johns Hopkins Medicine, metformin functions primarily by limiting the liver’s capacity to release glucose that’s been stored in the body.
Study Details
For this research, investigators enrolled 72 individuals at risk for metabolic syndrome—a dangerous cluster of conditions including obesity, elevated blood sugar, unhealthy cholesterol levels, and high blood pressure. People with metabolic syndrome face increased risks of developing diabetes and cardiovascular disease.
Participants were randomly sorted into four groups based on two variables: they performed either high-intensity or low-intensity exercise routines while taking either metformin or a placebo pill.
Key Findings
The results revealed that exercise by itself enhanced blood vessel sensitivity to insulin. These vessels showed improved responses to insulin and facilitated better blood flow to muscle tissue.
This matters because insulin-responsive blood vessels more effectively transfer glucose from the bloodstream into body tissues, thereby lowering blood sugar levels, researchers explained.
However, when metformin was introduced, these positive changes diminished. Participants gained fewer benefits from their exercise programs regardless of whether they followed high-intensity or low-intensity routines.
Malin noted: “Blood vessel function improved with exercise training, regardless of intensity. Metformin blunted that observation, suggesting one type of exercise intensity is not better either with the drug for blood vessel health.”
Overall, patients taking metformin may not experience the typical exercise-related benefits such as reduced blood sugar and enhanced fitness levels.
Malin elaborated: “If you exercise and take metformin and your blood glucose does not go down, that’s a problem. People taking metformin also didn’t gain fitness. That means their physical function isn’t getting better and that could have long-term health risk.”
Important Cautions
Researchers emphasized that people should not discontinue metformin or stop exercising without first consulting their healthcare provider.
Instead, these findings highlight the need to determine optimal strategies for combining the medication with physical activity.
Possible Mechanisms
Scientists theorize that metformin may reduce exercise benefits through its effects on mitochondria—the cellular structures responsible for energy production.
Metformin operates partially by inhibiting certain mitochondrial functions, which helps control blood sugar. However, this same mechanism might interfere with how mitochondria adapt to exercise, potentially blocking the aerobic capacity improvements that normally develop through consistent workouts.
Moving Forward
Malin stressed the importance of additional research: “We need to figure out how to best recommend exercise with metformin. We also need to consider how other medications interact with exercise to develop better guidelines for doctors to help people lower chronic disease risk.”
The study underscores the complex interactions between medications and lifestyle interventions, suggesting that treatment approaches may need refinement to maximize patient outcomes.