A popular diabetes drug sometimes taken to slow aging may diminish some of the expected health benefits of aerobic exercise in healthy older adults, according to a new report. The drug, metformin, can blunt certain physical changes from exercise that normally help people to age well.

The results raise questions about the relationship of pills and physical activity in healthy aging and also whether we know enough about how drugs and exercise interact. The results are particularly disconcerting given that healthy, active people may be considering taking the drug to slow aging.

Metformin currently is the most-prescribed medication globally for people with Type 2 diabetes. It allows people with Type 2 diabetes to improve their blood-sugar control and insulin sensitivity, in large part by reducing the amount of sugar released by the liver into the blood. In people with diabetes, the benefits can clearly outweigh the risks.

But in recent years, scientists, physicians and plenty of other people entering middle age have become intrigued by the idea that it might also change how healthy people age. Worms and rodents given metformin typically outlive their unmedicated labmates. These animal studies suggest that the drug not only reduces blood sugar, it also reduces inflammation and produces other cellular effects that alter aging.