Prevalence and Trends of Severe Obesity Among US Children and Adolescents

Objective: To determine the extent to which the 2007 definitions for severe obesity (body mass index [BMI] ≥99th percentile for age and gender) and morbid obesity (BMI ≥40 kg/m²) affects different groups of American children and adolescents and has increased over time. Methods: Analysis of nationally representative data from the National Health and Nutrition Examination Survey (NHANES) II, III, and 1999-2004; 12 384 US children and adolescents ages 2 to 19 years were included in the analysis. Outcome measures were the proportion of subjects with severe and morbid obesity, with age, gender, race, and poverty-income ratio (PIR) as key variables. Results: In 1999-2004, 3.8% of children 2 to 19 years old had a BMI in the ≥99th percentile, with higher prevalence among boys than girls (4.6% vs 2.9%; P < .001). Prevalence was highest among blacks, 5.7% and Mexican Americans, 5.2%, compared with whites, 3.1% (P < .001). The prevalence differed by the PIR category as well (4.3% for those with PIR ≤3 vs 2.5% for those with PIR > 3; P = .002). BMI ≥40 kg/m² was found in 1.3% of adolescents ages 12 to 19 years, with similar associations with race and poverty. The overall prevalence of BMI ≥99th percentile has increased by more than 300% since NHANES II (1976), and over 70% since NHANES III (1994) in children 2 to 19 years of age. Conclusions: Rates of severe childhood obesity have tripled in the last 25 years, with significant differences by race, gender, and poverty. This places demands on health care and community services, especially because the highest rates are among children who are frequently underserved by the health care system.