Elevated ALT is an indirect marker of NAFLD in patients with non-alcohol abuse and without other known causes of chronic hepatitis. Obesity, type 2 diabetes and some dyslipidemias are associated to this condition. The purpose of this study was to determine the frequency of increased aminotransferases and associated metabolic anomalies among overweight and obese children. Children from an elementary school with obesity or overweight were included. Medical history and anthropometrics measurements were recorded and serum liver function tests, lipid profile, glucose and insulin levels, and HOMA index were determined. NAFLD diagnosis was considered in those children with ALT>40 U/L and AST/ALT ratio40 U/L) were found in 34/ 80 (42%) obese and overweight children; mean age was 9.5+/-1.1 years and mean BMI of 25.8+/-3. The metabolic abnormalities in the study group were similar, there were no differences in insulin concentration, insulin resistance determined by HOMA-IR Index, serum lipid profile and serum glucose between children with or without increased ALT. The frequency (42%) of elevated ALT levels in children with excess body weight in this study was greater to those reported in other pediatric populations. There were no differences among the metabolic alterations with or without increased ALT; these findings support that the principal pathogenic factor involved in the development of the hepatic injury may be located in the liver.