Prevalence of Extreme Obesity in a Multiethnic Cohort of Children and Adolescents

Objective To estimate the prevalence of extreme obesity in a large, multiethnic contemporary cohort of children and adolescents. Study design In a cross-sectional study, measured weight and height were extracted from electronic medical records of 710 949 patients aged 2 to 19 years (87.8% of eligible patients) who were enrolled in an integrated prepaid health plan in 2007 and 2008. Prevalence of extreme obesity was defined as body mass index (BMI)-for-age ≥1.2 times 95th percentile or BMI ≥35 kg/m2. Results Extreme obesity was observed in 7.3% of boys and 5.5% of girls. The prevalence peaked at 10 years of age in boys and at 12 years of age with a bimodal distribution in girls (second peak at 18 years; P value for sex × age interaction = .036). The prevalence of extreme obesity varied in ethnic/racial and age groups, with the highest prevalence in Hispanic boys (as high as 11.2%) and African-American girls (as high as 11.9%). Conclusion Extreme obesity in Southern California youth is frequently observed at relatively young ages. The shift toward extreme body weights is likely to cause an enormous burden of adverse health outcomes once these children and adolescents grow older.