OBJECTIVE To assess differences between the effects of aerobic and resistance training on HbA_1c (primary outcome) and several metabolic risk factors in subjects with type 2 diabetes, and to identify predictors of exercise-induced metabolic improvement.

RESEARCH DESIGN AND METHODS Type 2 diabetic patients (n = 40) were randomly assigned to aerobic training or resistance training. Before and after 4 months of intervention, metabolic phenotypes (including HbA_1c, glucose clamp–measured insulin sensitivity, and oral glucose tolerance test–assessed β-cell function), body composition by dual-energy X-ray absorptiometry, visceral (VAT) and subcutaneous (SAT) adipose tissue by magnetic resonance imaging, cardiorespiratory fitness, and muscular strength were measured.

RESULTS After training, increase in peak oxygen consumption (VO_2peak) was greater in the aerobic group (time-by-group interaction P = 0.045), whereas increase in strength was greater in the resistance group (time-by-group interaction P < 0.0001). HbA_1c was similarly reduced in both groups (−0.40% [95% CI −0.61 to −0.18] vs. −0.35% [−0.59 to −0.10], respectively). Total and truncal fat, VAT, and SAT were also similarly reduced in both groups, whereas insulin sensitivity and lean limb mass were similarly increased. β-Cell function showed no significant changes. In multivariate analyses, improvement in HbA_1c after training was independently predicted by baseline HbA_1c and by changes in VO_2peak and truncal fat.

CONCLUSIONS Resistance training, similarly to aerobic training, improves metabolic features and insulin sensitivity and reduces abdominal fat in type 2 diabetic patients. Changes after training in VO_2peak and truncal fat may be primary determinants of exercise-induced metabolic improvement.