Changes in insulin resistance and Hb[A.sub.1c] are related to exercise-mediated changes in body composition in older adults with type 2 diabetes: interim outcomes from the GREAT2DO trial
Mavros, Y, Kay, S, Anderberg, KA, Baker, MK, Zhao, R, Meiklejohn, J, Climstein, M, O'Sullivan, A, deVos, N, Baune, BT, Baune, SN, Blair, SN, Simar, D, Rooney, K, Singh, N & Fiatarone, MA 2013, 'Changes in insulin resistance and Hb[A.sub.1c] are related to exercise-mediated changes in body composition in older adults with type 2 diabetes: interim outcomes from the GREAT2DO trial', Diabetes Care, vol. 36, no. 8, pp. 2372-2379.
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OBJECTIVE--To investigate changes in body composition after 12 months of high-intensity progressive resistance training (PRT) in relation to changes in insulin resistance (IR) or glucose homeostasis in older adults with type 2 diabetes.
RESEARCH DESIGN AND METHODS--One-hundred three participants were randomized to receive either PRT or sham exercise 3 days per week for 12 months. Homeostasis model assessment 2 of insulin resistance (HOMA2-IR) and glycosylated hemoglobin (Hb[A.sub.1c]) were used as indices of IR and glucose homeostasis. Skeletal muscle mass (SkMM) and total fat mass were assessed using bioelectrical impedance. Visceral adipose tissue, mid-thigh cross-sectional area, and mid-thigh muscle attenuation were quantified using computed tomography.
RESULTS--Within the PRT group, changes in HOMA2-IR were associated with changes in SkMM (r = -0.38; P = 0.04) and fat mass (r = 0.42; P = 0.02). Changes in visceral adipose tissue tended to be related to changes m HOMA2-IR (r = 0.35; P = 0.07). Changes in Hb[A.sub.1c] were related to changes in mid-thigh muscle attenuation (r = 0.52; P = 0.001). None of these relationships were present in the sham group (P > 0.05). Using ANCOVA models, participants in the PRT group who had increased SkMM had decreased HOMA2-IR (P = 0.05) and Hb[A.sub.1c] (P = 0.09) compared with those in the PRT group who lost SkMM. Increases in SkMM in the PRT group decreased HOMA2-IR (P = 0.07) and Hb[A.sub.1c] (P < 0.05) compared with those who had increased SkMM in the sham group.
CONCLUSIONS--Improvements in metabolic health in older adults with type 2 diabetes were mediated through improvements in body composition only if they were achieved through high-intensity PRT.