Effects of adding exercise to a 16-week very low-calorie diet in obese, insulin-dependent type 2 diabetes mellitus patients

Abstract

Context: Reduction of 50% excess body weight, using a very low-calorie diet (VLCD; 450 kcal/d) improves insulin sensitivity in obese type 2 diabetes mellitus patients. Objective: The objective of the study was to evaluate whether adding exercise to the VLCD has additional benefits. Design: This was a randomized intervention study. Setting: The study was conducted at a clinical research center in an academic medical center. Subjects: Twenty-seven obese [body mass index 37.2±0.9 kg/m2 (mean±SEM)] insulin-treated type 2 diabetes mellitus patients. Intervention: Patients followed a 16-wk VLCD. Thirteen of them simultaneously participated in an exercise program (E) consisting of 1-h, in-hospital training and four 30-min training sessions on a cycloergometer weekly. Outcome Measures: Insulin resistance was measured by a hyperinsulinemic euglycemic clamp. Insulin signaling, mitochondrial DNA (mtDNA) content, and intramyocellular lipid content was measured in skeletal muscle biopsies. Results: Baseline characteristics were identical in both groups. Substantial weight loss occurred (-23.7±1.7kg VLCD-only vs.-27.2±1.9kg VLCD+E,P=NS within groups). The exercise group lost more fat mass. Insulin-stimulated glucose disposal increased similarly in both study groups [15.0±0.9 to 39.2±4.7 μmol/min-1 · kg lean body mass (LBM-1) VLCD-only vs. 17.0 ± 1.0 to 37.5 ± 3.5 μmol/min-1 · kg LBM-1 in VLCD+E], as did phosphorylation of the phosphatidylinositol 3-kinase-protein kinase B/AKT insulin signaling pathway. In contrast, skeletal muscle mtDNA content increased only in the VLCD+E group (1211±185 to 2288±358, arbitrary units, P=0.016 vs. 1397±240 to 1196±179, P=NS, VLCD-only group). Maximum aerobic capacity also only increased significantly in the VLCD+E group (+6.6±1.7 ml/min-1 · kg LBM-1 vs. +0.7 ± 1.5 ml/min-1 · kg LBM-1 VLCD-only, P = 0.017). Conclusion: Addition of exercise to a 16-wk VLCD induces more fat loss. Exercise augments maximum aerobic capacity and skeletal muscle mtDNA content. These changes are, however, not reflected in a higher insulin-stimulated glucose disposal rate. Copyright © 2012 by The Endocrine Society.