The Diabetes Control and Complications Trial (DCCT) demonstrated that intensive diabetes therapy delays the onset and progression of microvascular disease such as retinopathy, nephropathy and neuropathy. The DCCT also showed that the prevalence of obesity, defined as a body mass index (BMI) ≥ 27.8 kg/m2 for men and ≥ 27.3 kg/m2 for women, was 33.1% in the intensive treatment group compared with 19.1% in the conventional treatment group. Intensively treated patients gained an average of 4.75 kg more than conventionally treated patients (P < 0.0001). Weight gain was most rapid during the first year of therapy. Several mechanisms have been proposed to explain the weight gain associated with insulin therapy. These include decreased glycosuria due to improved glycemic control, the direct lipogenic effects of insulin on adipose tissue, and increased food intake due to recurrent mild hypoglycemia.