If you are one of the more than 150 million people worldwide who take metformin in order to improve insulin sensitivity and like to workout, you might be surprised to learn that a new study suggests the drug could weaken several of the important benefits gained from exercise.
Here’s what you need to know.
The study, led by a team at Rutgers University, appears to show that metformin may diminish exercise based improvements in a variety of areas, such as vascular health and blood sugar control. While the traditional advice has been to combine metformin with exercise for a two-pronged approach to battling type 2 diabetes, Rutgers researchers say the evidence is not so straight forward.
“Most health care providers assume one plus one equals two,” said Steven Malin, a professor and lead author of the study. “The problem is that most evidence shows metformin blunts exercise benefits.”
How was this Metformin study carried out?
72 adults at risk of metabolic syndrome (a variety of conditions that raise the risk of diabetes and heart disease) were divided into four groups:
- People performing high-intensity exercise on a placebo
- People performing high intensity exercise on metformin
- People performing low-intensity exercise on a placebo
- People performing low intensity exercise on metformin
Over the course of 16 weeks, scientists monitored changes in blood vessel function under insulin stimulation to help the vessels dilate and deliver oxygen, hormones, and nutrients after meals.
What were the results?
Exercise alone was shown to improve vascular insulin sensitivity, allowing greater blood flow to the muscles, but in the groups taking metformin, the benefits were decreased. Metformin diminished aerobic fitness gains and even lessened positive effects towards inflammation and fasting glucose levels in those who combined the drug with exercise. “Blood vessel function improved with exercise training, regardless of intensity,” said Professor Malin. “Metformin blunted that observation, suggesting one type of exercise intensity is not better either with the drug for blood vessel health.”
These results are disappointing for those on metformin who like to workout, because exercising reduces blood sugar levels and improves physical function. “If you exercise and take metformin and your blood glucose does not go down, that’s a problem,” said Professor Malin. “People taking metformin also didn’t gain fitness. That means their physical function isn’t getting better and that could have long-term health risks.”
The reasons for these effects are not perfectly understood yet, but it is thought metformin could be blocking parts of the mitochondria and the system that normally regulates blood sugar balance and oxidative stress.
So, what are we to make of these findings? Professor Malin says that people shouldn’t stop taking metformin to chase gains, or stop exercising, but it does mean that the medical community needs to figure out future strategies to improve the response to exercise while on the drug. “We need to figure out how to best recommend exercise with metformin,” concluded Professor Malin.
Previous experiments have suggested that timing of metformin intake could help. One study found that morning moderate-intensity exercise combined with pre-breakfast metformin was more effective at reducing blood glucose levels over several weeks compared to taking metformin after breakfast. “We also need to consider how other medications interact with exercise,” Malin said.
