Use of a reference four-component model to define the effects of insulin treatment on body composition in type 2 diabetes: the 'Darwin study'

Aims: To define the effects of insulin treatment on body composition and fat distribution, and investigate the potential role of body weight (BWt) gain predictors in patients with poorly controlled type 2 diabetes. Methods: Assessments of body composition, using a four-component model, and biochemical indices were obtained in 19 patients [ mean (SD): age, 60 (8.3) years; BMI, 25.3 (3.3) kg/m(2)] with poorly controlled type 2 diabetes, despite maximal oral hypoglycaemic agents, receiving insulin [ 40 (12.2) units/day] at baseline and after 1, 3 and 6 months. Results: Insulin therapy significantly reduced plasma glucose [- 6.0 (4.3) mmol/l], improved HbA(1)c [- 1.9 (1.8)%], and reversed the BWt lost [3.3 ( 1.8) kg] before treatment. The 6-month BWt gain [+ 5.2 (2.7) kg] consisted of body fat [+ 2.9 ( 2.7) kg] and fat-free mass [FFM; + 2.3 ( 1.8) kg], with the FFM increase due solely to total body water [ TBW; + 2.4 (1.5) l], as there were no detectable changes in total body protein or bone mineral, thereby increasing FFM hydration by 1.3%. More body fat was deposited centrally in patients receiving insulin alone than those receiving insulin with an oral hypoglycaemic agent ( metformin). Daily insulin dose, HbA(1)c and hip circumference were independent predictors of BWt gain. Conclusions: Insulin treatment increased fat and FFM similarly in poorly controlled type 2 diabetes patients, with the FFM gain due entirely to TBW. The possible role of metformin in reducing central fat accumulation following insulin treatment warrants further investigation into its mechanism and potential long-term benefits.