High intensity aerobic exercise lowers blood sugar levels and improves fitness in people with type 2 diabetes

Grace A, Chan E, Giallauria F et al. Clinical outcomes and glycaemic responses to different aerobic exercise training intensities in type II diabetes: A systematic review and meta-analysis Cardiovasc Diabetol. 2017;16:37.

Review question

Do aerobic exercise programs decrease blood sugar levels, increase physical fitness and improve other health outcomes in people with type 2 diabetes? What intensity of aerobic exercise is most effective?

Background

Healthy diet and exercise are known to improve blood sugar levels in type 2 diabetes. Researchers have found that when combined, aerobic (cardio) and resistance (strength training) exercise work well for controlling blood sugar in diabetes. In people without diabetes, high intensity aerobic exercise has been shown to help regulate blood sugar levels and improve physical fitness.

How the review was done

This is a review of 27 randomized-control trials conducted from 1986 to 2014, including a total of 1 372 participants. All the studies were combined in a meta-analysis.

• All participants were adults with type 2 diabetes.
• Study participants took part in exercise programs that ranged from four weeks to one year in duration. The exercise sessions varied in intensity and occurred between two to five times per week, with each session being 15 to 75 minutes long, depending on the study.
• Researchers measured participants’ blood sugar levels (HbA1c), blood insulin levels and insulin resistance (HOMA-IR), a marker of diabetes control. Researchers also measured participants’ physical fitness levels (VO₂), as well as lean body mass, body mass index (BMI) and body composition.
• Results were compared to control groups who did not participate in the exercise programs.

What the researchers found

Aerobic exercise helped to lower blood sugar (HbA1c) and increase fitness levels among participants. Programs that were longer in duration led to greater decreases in blood sugar levels. Compared to low or moderate intensity exercise, high intensity exercise was slightly more effective in decreasing blood sugar and effective in increasing fitness. Insulin resistance, fasting glucose and insulin levels were also improved by the exercise programs.

Conclusion

Aerobic exercise is an effective way to decrease blood sugar levels and improve fitness in people with type 2 diabetes. High intensity aerobic exercise done regularly over longer time periods is most effective.