Introduction: while the traditional idea has been that patients with type 1 diabetes mellitus (DM1) are thin, the prevalence of overweight and obesity has increased in parallel with the general population. Intensive treatment reduced microvascular complications, but generated overinsulinization, hypoglycemia, defensive intake and weight gain, with coexistence of elements of the metabolic syndrome. Objectives: to determine the frequency of overweight, obesity and the associated risk factors and degree of insulin resistance in patients with DM1. Patients and methods: 414 DM1 ≥18 years, women 52%, age 34.8±13.9 years of 14 departments of the province of Mendoza were stratified according to BMI in normal weight N, overweight and obesity. The following were analyzed: age, physical activity ≥3 times/week, HbA1c, LDL-C