• Posted November 12, 2025

Daily Walks Potentially Sabotaged By Diabetes Drug, Study Says

A common diabetes drug could be sabotaging the health benefits that a patient might expect from a daily walk, a new study says.

Metformin appears to blunt improvements in blood pressure, fitness and blood sugar control that normally come from regular exercise, researchers report in The Journal of Clinical Endocrinology & Metabolism.

This complicates current guidelines that advise patients with high blood sugar to take metformin while engaging in exercise, researchers said. The reasoning: Two proven therapies should deliver better results when combined.

“Most health care providers assume one plus one equals two. The problem is that most evidence shows metformin blunts exercise benefits,” lead researcher Steven Malin said in news release. He’s a professor of kinesiology and health at Rutgers University-New Brunswick in New Jersey. 

Metformin works primarily by reducing the liver’s ability to release stored glucose, according to Johns Hopkins Medicine.

For the new study, researchers recruited 72 people at risk for metabolic syndrome — a dangerous combination of obesity, high blood sugar, abnormal cholesterol and high blood pressure. People with metabolic syndrome have a higher risk of diabetes and heart disease.

The participants were randomly divided into four groups. People performed either high-intensity or low-intensity exercises, while taking either metformin or a placebo.

Results showed that exercise alone improved blood vessel sensitivity to insulin. The vessels responded better to insulin and allowed more blood flow to muscles.

This is important because blood vessels expanded by insulin are better able to shuttle glucose out of the bloodstream and into tissues, reducing a person’s blood sugar, researchers said.

But when metformin was added, these improvements shrank. People also got less from their exercise programs, whether high- or low-intensity, researchers said.

“Blood vessel function improved with exercise training, regardless of intensity,” Malin said. “Metformin blunted that observation, suggesting one type of exercise intensity is not better either with the drug for blood vessel health.”

In all, patients taking metformin might not get the benefits associated with exercise, like lower blood sugar and improved fitness, researchers said.

“If you exercise and take metformin and your blood glucose does not go down, that’s a problem,” Malin said. “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.”

However, researchers said people shouldn’t stop taking metformin or exercising without consulting with their doctor.

Instead, these results show the need to figure out how the two can be combined best.

Researchers speculated that metformin might blunt exercise benefits due to its effects on mitochondria, which are the powerhouses of human cells.

Metformin works partly by blocking some mitochondrial action, improving blood sugar control. But that same action might inhibit how mitochondria respond to exercise, blocking the development of better aerobic capacity that normally occurs after regular workouts.

“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.”

More information

Johns Hopkins Medicine has more about metformin.

SOURCE: Rutgers University-New Brunswick, news release, Nov. 6, 2025