Structured exercise with aerobic, resistance, or combined training was associated with a 0.67% decrease in hemoglobin A1c level among patients with type 2 diabetes, according to a meta-analysis in the May 4 issue of JAMA.
This compares favorably with the HbA1c reductions reported for combination treatment with noninsulin antidiabetic drugs and maximal doses of metformin, said Daniel Umpierre of the Hospital de Clinicas de Porto Alegre (Brazil) and his associates.
The investigators performed a meta-analysis of 47 randomized controlled trials that assessed the effects of 12 weeks or more of structured aerobic exercise training (848 subjects), structured resistance exercise training (261), combined aerobic and resistance training (404), or unstructured physical activity (7,025) on HbA1c levels.
Structured exercise training was defined as an intervention in which patients engaged in a planned, individualized, and supervised exercise program.
"The general quality of the studies was low, reflecting increased risk of bias in some studies," the investigators noted.
Eighteen studies demonstrated that structured aerobic exercise training was associated with an absolute reduction of 0.73% in HbA1c level. Four studies showed that structured resistance exercise training was associated with an absolute reduction of 0.57%. And seven studies showed that combined aerobic plus resistance exercise training was associated with an absolute reduction of 0.51%.
These benefits were most marked when the exercise was performed for 150 min/wk or more (absolute reduction of 0.89% in HbA1c), and less so when it was performed less often (absolute reduction of 0.36% in HbA1c). Current guidelines recommend an exercise duration of at least 150 min/wk, Mr. Umpierre and his colleagues said (JAMA 2011;305:1790-9).
In contrast, 24 studies of physical activity demonstrated that it was associated with an absolute reduction of 0.43% in HbA1c. However, physical activity alone did not reduce HbA1c. It was effective only when combined with dietary advice, as shown in 12 studies in which HbA1c level declined by 0.58%.
"To our knowledge, this is the first systematic review to assess the association between physical activity advice interventions and glycemic control," they noted.
Mr. Umpierre’s associates reported ties to Bristol-Myers Squibb, GlaxoSmithKline, Merck Sharpe & Dohme, Servier, Abbott, Aventis, Bioassist, and Boehringer Ingelheim.