ObjectiveTo verify if there is an increase in frequency of type 2 diabetes mellitus (DM2) and glucose intolerance in children and adolescents who are overweight and obese.MethodsThis was a cross-sectional survey. The study population consisted of 2757 students of both sexes (1415 girls and 1342 boys) attending public schools in São Paulo state, Brazil,aged 10–19 years, from 2011 to 2012. Students not within this age range and those with type 1 diabetes mellitus were excluded. Upon interview, anthropometry, capillary blood glucose testing, fasting glucosemia (FG) and glucosemia 2 hours after 75 g of dextrose (AD) variables were obtained. We emphasize that, inspite of the 2757 students included in the next stage, only 88 students agreed to participate, and low compliance of those participants is due to the fact that they were children and adolescents who depend on the authorization of their parents or tutors, who have demonstrated deficient knowledge of familial chronic diseases such as obesity and its consequences, and the risk of DM2.ResultsMore often girls, 1415 (51.3%). A total of 27.3% was overweight/obese/severely obese. Capillary blood glucose testing was performed in 88 (3.2%) children and adolescents with low values of glycemic results after the glucose load. There was no statistical significance between sex and glucosemia, with an average FG and AD of 92.8 mg/dL (male), 91.8 mg/dL (female) and 89.1 mg/dL (male) and 88.9 mg/dL (female), respectively.ConclusionThis survey emphasizes that more attention should be paid to diet interventions and practicing of physical activities demanding habit changes and acquisition of special behaviour for self-care, and provision of a better educational health program, suggesting the effective participation of the family.