Ethnic and gender differences in body fat in British schoolchildren as measured by DXA

Background: There are known to be ethnic differences in body composition in adults which are related to ethnic differences in adult disease. Objectives: To evaluate gender and ethnic differences in percentage body fat in British schoolchildren and to compare these differences with classification of obesity using body mass index (BMI) criteria. Design: A cross-sectional study of 1251 healthy children and adolescents aged 5-18 years from white, South Asian and African-Caribbean ethnic groups. Percentage body fat was determined by dual x ray absorptiometry and the subjects classified using BMI criteria for overweight and obesity. Results: Significant gender differences in percentage body fat were seen, with girls having higher values from the age of 5 years. Girls had 3.8% higher percentage body fat at 5 years of age increasing to 12.9% at 18 years of age. Significant ethnic differences were found, with South Asian girls and boys having the highest percentage body fat from 5 and 7 years of age, respectively. These differences increased with age, being most significant in the teenage years. Although South Asian girls and boys were over-represented in the group containing children with more than 25% body fat (p < 0.0001, X-2 test), African-Caribbean subjects were more likely to be classified as obese using BMI criteria. Conclusions: There are clear gender and ethnic differences in percentage body fat in British schoolchildren which may relate to known differences in the risk of type 2 diabetes in adolescence and adulthood. BMI criteria for defining overweight and obesity do not accurately identify ethnic differences in body fat.