This study aimed to determine the prevalence of and risk factors associated with elevated alanine aminotransferase (ALT) levels among a sample of normal weight, overweight and obese youth from two urban populations in Central Mexico.Baseline data from 1262 youth aged 8-19 years who participated in the Mexican Health Worker Cohort Study from March 2004 to April 2006 were reviewed, including 680 girls and 582 boys, with a total of 83 participants with elevated ALT level (>40 U/L). Information was obtained from self-administered questionnaires, anthropometric results and clinical measurements. Associations of interest were examined using multivariate logistic regression models.A total of 3.8% of girls and 9.8% of boys had elevated ALT levels. Elevated ALT was observed in 28.9% of the obese and 14.2% of the overweight participants. Metabolic syndrome (MS) occurred in 6.1% of the study population and those with MS had a high percentage of elevated ALT (14.5% of girls and 40.0% of boys, respectively). Abdominal obesity and insulin resistance were also associated with a greater risk of elevated ALT.Obesity and certain metabolic risk factors are important predictors for elevated ALT. Screening for ALT levels in obese youth could help to identify those at risk and reduce the possibility of future liver diseases.© 2013 Wiley Publishing Asia Pty Ltd and Chinese Medical Association Shanghai Branch, Chinese Society of Gastroenterology, Renji Hospital Affiliated to Shanghai Jiaotong University School of Medicine.