Metformin interferes with training improvements to O2 uptake.

[Eddy Edson]

https://onlinelibrary.wiley.com/doi/10.1002/oby.23410

A new study, adding to the body of evidence that metformin sometimes doesn't sit well with exercise. There really doesn't seem to be good evidence for metformin benefits outside of glycemic control (despite the Internet), but there is good evidence that it can interefere with the benefits of exercise. Anyway, that's the reason I stopped taking it once my BG was sorted.

What is already known?​

• ►Exercise and metformin are first-line therapeutic options for the treatment of prediabetes and type 2 diabetes.
• ►Nevertheless, there is evidence of interfering effects of metformin on the insulin-sensitizing and cardiorespiratory fitness improvements induced by exercise training.

What does this study add?​

• ►Chronic metformin treatment was associated with blunted gains in maximal oxygen uptake (VO2MAX) with intense aerobic exercise training in people with metabolic syndrome and hyperglycemia.
• ►However, the associated blunted VO2MAX development did not prevent exercise-induced improvements in fasting insulin resistance.

How might these results change the focus of clinical practice?​

• ►Although fitness improvements may be blunted by the chronic use of metformin in people with metabolic syndrome, this does not hinder the clinical benefits of exercise training on reducing fasting insulin resistance; therefore, clinical practice should include exercise advice.

This study differs from others in finding that metformin did not interfere with the benefits from exercise to things like fasting BG. There is a commentary in the same edition of the journal addressing this issue and various other subtleties, and also providing references to other studies: https://onlinelibrary.wiley.com/doi/10.1002/oby.23455