Level 3: Lacking direct evidence
Physical activity is recommended for patients with type 2 diabetes mellitus, but it is important that exercise be gradually increased and coordinated with insulin dosages, glucose monitoring, and meals.
A systematic review of 14 randomized trials evaluated the effects of exercise (compared with no exercise) in 377 patients with type 2 diabetes mellitus (Cochrane Database Syst Rev. 2006:CD002968). The trials ranged from eight weeks to 12 months in duration.
The exercise intervention significantly reduced glycosylated hemoglobin (HbA1c) (mean difference -0.6%, 95% confidence interval [CI] -0.9% to -0.3%) while significantly increasing insulin response and decreasing plasma triglycerides (mean difference -22.1 mg/dL, 95% CI -42.5 to 1.8). There were no significant differences in BP or plasma cholesterol levels. Whole-body mass showed no significant reduction, possibly due to an increase in fat-free mass (muscle), as noted in one trial. In another trial, no significant differences were observed in quality of life.
This review provides good evidence that exercise improves glycemic control, but it does not provide direct evidence of improving health outcomes. Exercise is recommended as a first-line therapy for diabetes based on expected benefits and has been associated with reduced mortality and cardiovascular disease in other studies.