Physical activity advice only or structured exercise training and association with HbA1c levels in type 2 diabetes: a systematic review and meta-analysis.

CONTEXT: Regular exercise improves glucose control in diabetes, but the association of different exercise training interventions on glucose control is unclear.
OBJECTIVE: To conduct a systematic review and meta-analysis of randomized controlled clinical trials (RCTs) assessing associations of structured exercise training regimens (aerobic, resistance, or both) and physical activity advice with or without dietary cointervention on change in hemoglobin A(1c) (HbA(1c)) in type 2 diabetes patients. DATA SOURCES: MEDLINE, Cochrane-CENTRAL, EMBASE, ClinicalTrials.gov, LILACS, and SPORTDiscus databases were searched from January 1980 through February 2011. STUDY SELECTION: RCTs of at least 12 weeks' duration that evaluated the ability of structured exercise training or physical activity advice to lower HbA(1c) levels as compared with a control group in patients with type 2 diabetes. DATA EXTRACTION: Two independent reviewers extracted data and assessed quality of the included studies. DATA SYNTHESIS: Of 4191 articles retrieved, 47 RCTs (8538 patients) were included. Pooled mean differences in HbA(1c) levels between intervention and control groups were calculated using a random-effects model. Overall, structured exercise training (23 studies) was associated with a decline in HbA(1c) level (-0.67%; 95% confidence interval [CI], -0.84% to -0.49%; I(2), 91.3%) compared with control participants. In addition, structured aerobic exercise (-0.73%; 95% CI, -1.06% to -0.40%; I(2), 92.8%), structured resistance training (-0.57%; 95% CI, -1.14% to -0.01%; I(2), 92.5%), and both combined (-0.51%; 95% CI, -0.79% to -0.23%; I(2), 67.5%) were each associated with declines in HbA(1C) levels compared with control participants. Structured exercise durations of more than 150 minutes per week were associated with HbA(1c) reductions of 0.89%, while structured exercise durations of 150 minutes or less per week were associated with HbA(1C) reductions of 0.36%. Overall, interventions of physical activity advice (24 studies) were associated with lower HbA(1c) levels (-0.43%; 95% CI, -0.59% to -0.28%; I(2), 62.9%) compared with control participants. Combined physical activity advice and dietary advice was associated with decreased HbA(1c) (-0.58%; 95% CI, -0.74% to -0.43%; I(2), 57.5%) as compared with control participants. Physical activity advice alone was not associated with HbA(1c) changes.
CONCLUSIONS: Structured exercise training that consists of aerobic exercise, resistance training, or both combined is associated with HbA(1c) reduction in patients with type 2 diabetes. Structured exercise training of more than 150 minutes per week is associated with greater HbA(1c) declines than that of 150 minutes or less per week. Physical activity advice is associated with lower HbA(1c), but only when combined with dietary advice.