Prescription drugs are meticulously studied and investigated to determine not only their safety for use by the public but also their effectiveness. Metformin, a common medication for Type 2 diabetics, is no exception. Doctors often prescribe both metformin and regular exercise for patients with Type 2 diabetes as methods of controlling their blood glucose levels. However, in a study about metformin, exercise, and the effects of both on blood sugar, researcher Normand Boulé received results that he did not expect.
“The study had three objectives: we wanted 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, which is essential for people with diabetes,” said Boulé. The project was a randomized, crossover double-blind study involving five different faculties at the University of Alberta.
The study followed ten men and women, all between the ages of 30 and 65, with Type 2 diabetes. The participants were not taking any glucose-lowering medication or insulin. They were randomly assigned to take either metformin or placebo for 28 days; after the first phase, their medications were reversed for another 28 days. The participants spent six hours in the lab on days 27 and 28 performing various physical tests, including 40 minutes of physical activity on day 28 of the study.
“Metformin reduces glucose in the blood and many believe it does so by activating exercise-like pathways,” says 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.” While the blood-glucose lowering effects of both metformin and exercise are documented, it appears that combining them on the same day isn’t always as effective in lowering blood sugar as simply using metformin alone.
Boulé believes that the phenomenon occurs because both metformin and exercise cause blood sugar levels to drop. On the days when study participants used the medication and exercised, the body may have responded by preventing blood glucose levels from dropping too much. “During exercise, glucagon concentrations increased in the blood (a hormone secreted by the pancreas that raises glucose levels) but when we combined exercise and metformin the glucagon levels were almost twice as elevated,” said Boulé.
However, Boulé doesn’t believe the study shows metformin alone is always better than a combination of exercise and metformin. The timing of the meals relative to the exercise sessions probably affected the results of the study. The intensity levels may have also played a part, in addition to the fact that data was collected only from a single exercise session rather than from a more regular exercise routine.
Despite the unexpected findings, Boulé’s study confirmed the results of previous studies which showed that patients taking metformin displayed increased lactate levels and increased use of fats as an energy source during exercise. According to Boulé, the study was also the first to show that patients taking metformin had a higher average heart rate—six beats more per minute—than those taking placebo.
“However, all participants were able to complete the exercise portion in both metformin and placebo conditions,” said Boulé. “Also surprising is that throughout the day that they exercised, metformin concentrations were higher than on the day that they didn’t.”
Boulé stressed that exercise has great benefits for diabetics and that it should still be an integral aspect of glucose control for any diabetic.