Effect of insulin treatment on the body composition of Type 2 diabetic patients.

OBJECTIVE: Insulin is used commonly in Type 2 diabetes and is often accompanied by weight gain. The composition of this weight gain is poorly understood. Predominant increases in fat mass could increase cardiovascular risks. The aim of the study was to evaluate insulin-induced body composition changes. RESEARCH DESIGN AND METHODS: Body weight and composition of 35 Type 2 diabetic patients during their first 6 months of insulin therapy was compared with those in 34 Type 2 diabetic individuals treated with insulin for at least 1 year prior to commencing the study. Body composition was determined by the simultaneous measurement of body water spaces and body density. RESULTS: Over 6 months, glycaemic control improved in the new treatment group only (HbA(1c): 7.26 +/- 0.81 vs. 9.66 +/- 1.60%; P < 0.0001), remaining stable in the previously treated group (7.67 +/- 1.25 vs. 7.76 +/- 1.26%; P = NS). Weight significantly increased over time in the newly treated group (+1.7 kg; P = 0.04), but not in the previously treated group (-0.3 kg). It comprised of both fat (+0.85 kg) and fat-free mass (+0.55 kg). Total body water remained unchanged. Using bioelectrical impedance analysis, the gain in fat mass was +2.2 kg; P = 0.048. CONCLUSIONS: Over 6 months, insulin therapy leads to a weight gain of 1.7 kg because of an increase in both fat and fat-free mass. When body composition is determined by bioelectrical impedance analysis, the results are biased by fluctuations in hydration.