Does Exercise Interfere With Metformin?

August 25th, 2011 by Ryan Luce No Comments

written by Michael O’Leary

Sometimes research surprises, especially when the results seem counter-intuitive. Canadian researchers had just such a surprise when their study looking at the impact that drug therapy and exercise have  on people with type 2 diabetes showed that exercise seems to interfere with the glucose-lowering effects of metformin.

Research has shown that metformin reduces blood sugar in people with type 2 diabetes, and exercise improves insulin sensitivity, so intuitively, one would think doing both would reduce glucose levels even more. But in their small study of 10 people the researchers were surprised to see the opposite occurred. (Link to published site)

While the study size is small, Dr. Normound Boule, associate professor at of the University of Alberta, told Corengi by e-mail that it was adequate to detect many differences between conditions.

“Metformin reduces glucose in the blood and many believe it does so by activating exercise-like pathways,” explains Boulé. “As expected, in our study metformin lowered the blood glucose concentrations measured during a two-hour period after lunch. But we found that on the non-exercise day metformin led to better glucose control after lunch than on the day our participants took metformin and exercised.”

The study published in the July issue of Diabetes Care was designed to look at the effect of metformin on exercise in people with type 2 diabetes, examine the effect of exercise on metformin concentrations in the body, and finally to look at the effects of metformin and exercise on glucose control.

The ten men and women were between 30 and 65 with type 2 diabetes and were not taking glucose-lowering medication or insulin. They were randomly assigned to take metformin or placebo for the first 28 days of the study. Each group then switched and those taking placebo were given metformin and those on metformin were given placebo for another 28 days. On days 27 and 28 of each four-week period participants spent six hours in a exercise physiology lab undergoing a variety of tests, before and after 40 minutes of exercise.

During exercise, the levels of the hormone glucagon, which is secreted by the pancreas to raise glucose levels increased in the blood. But when the exercise was combined with metformin the glucagon levels were almost twice as high.

Boulé thinks that because both metformin and exercise act to lower glucose levels, the combination may have triggered a counter regulatory response by the body to prevent glucose levels dipping too much.

Also surprising was that throughout the day that they exercised, metformin concentrations were higher than on the day that they didn’t. Boulé says the reasons for this are not well understood.

The study did show that metformin increased lactate levels, and increased use of fats as an energy source during exercise, which was consistent with previous studies. However, he believes his study was the first to document a significantly increased heart rate, on average six beats more per minute, during aerobic exercise of various intensities with metformin.

Boulé cautions that the small study should not cause type 2 diabetes patients to cut back on exercising. He pointed out that the fact that the glucose levels were measured after a single bout of exercise as opposed to regular daily exercise may have something to do with the result. He added that exercise has hundreds of benefits and should still be an important part of a healthy approach to glucose control for those with diabetes, including those taking metformin.

“What we’ve learned is that the relationship between exercise and metformin is complex, and this opens the door for more research to examine how different treatments work together, especially because exercise is widely prescribed for people with diabetes and metformin is often the first line drug of choice for treating type 2 diabetes,” said Boulé.