Re-evaluation of adult obesity thresholds in some ethnic groups has led to the questioning of childhood obesity thresholds. An expert group was convened to examine the representativeness of childhood obesity definitions, evidence for ethnic differences in body composition in UK children and the extent of misclassification of adiposity by current body mass index (BMI) thresholds in south Asian and black groups. The group concluded that the current International Obesity Task Force (IOTF) definitions remained the most appropriate for use in the United Kingdom, but further research was needed on the relationship of body shape, fat mass, metabolic markers and ethnicity in children and adolescents.