A widely prescribed diabetes drug may be blunting the beneficial effects of exercise in patients, a new study suggests.
More than 450 million people across the world suffer from type 2 diabetes – with that number rising by the year – and treatment often hinges on lifestyle changes combined with medication.
For nearly half a century now, doctors have prescribed metformin and recommended daily physical activity to diabetes patients. The reasoning is the two proven therapies deliver better results together.
Metformin reduces blood glucose levels by inhibiting the liver’s glucose production and by helping cells use their own insulin more effectively.
Now, however, researchers say metformin may sabotage the beneficial effects of exercise.
“Most health care providers assume one plus one equals two,” Rutgers University kinesiologist Steven Malin, an author of the new study published in The Journal of Clinical Endocrinology & Metabolism, said. “The problem is that most evidence shows metformin blunts exercise benefits.”
Researchers say the latest study raises urgent questions for doctors about how the two therapies can be better combined.
The study recruited 72 adults at risk of metabolic syndrome, a cluster of conditions known to raise the risk of diabetes and heart disease, and divided them into groups of those who did high-intensity exercise while taking a placebo, high-intensity exercise with metformin, low-intensity exercise with placebo, and low-intensity exercise with metformin.
For four months, researchers tracked changes in the function of blood vessels of the participants under insulin stimulation, a process known to help the vessels dilate and deliver oxygen, hormones and nutrients after meals.
They found that exercise helped the blood vessels respond better to insulin, allowing more blood flow to muscles, but these improvements shrank if metformin was added.
Metformin also appeared to diminish gains from aerobic exercises and reduce the positive effects on inflammation and fasting glucose.
Researchers suspect that the very process that makes metformin effective may be blocking the body's ability to respond fully to physical training.
“Blood vessel function improved with exercise training, regardless of intensity,” Dr Malin noted.
“Metformin blunted that observation, suggesting one type of exercise intensity isn’t better either with the drug for blood vessel health. People taking metformin also did not gain fitness. That means their physical function isn't getting better and that could have long-term health risk.”
Researchers call for further studies to find strategies that can preserve the benefits of both exercise and metformin.
“We need to figure out how to best recommend exercise with metformin,” Dr 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.”
