Extent of overweight among US children and adolescents from 1971 to 2000

CONTEXT: The prevalence of overweight (OW) among children in the United States has increased during the last three decades, but prevalence measures fail to reveal the extent to which OW children exceed the OW threshold. OBJECTIVE: To measure the amount by which OW children exceed the OW threshold. To examine the trend in this measure over the last three decades using data with measured weights and heights. DESIGN, SETTING AND PARTICIPANTS: Data used for analysis are from the National Health and Nutrition Examination Survey ( NHANES) for persons between 2 and 19 y of age from 1971 to 2000. Anthropometric measures were obtained by trained health technicians, and the sample sizes range from 4037 in 1999 - 2000 to 10 590 in 1988 - 1994. MAIN OUTCOME MEASURE: The extent of OW is measured as the average amount by which each child's body mass index (BMI) exceeds their age and gender-specific OW threshold. This measure is examined by sex, age group and race/ethnicity. The OW threshold for those aged 2 - 19 y is defined as at or above the 95th percentile of the sex-specific BMI for age growth charts. RESULTS: The extent of child OW has been increasing faster than the prevalence of child OW for all classifications considered in this paper, including the analysis by age, sex, race and ethnicity. The prevalence of OW for children aged 2 - 19 y increased by 182% between 1971 - 1971 and 1999 - 2000, while the extent of OW increased by 247% over the same time period. CONCLUSIONS: Unlike prevalence measures, the measure of the extent of child OW is sensitive to changes in the BMI distribution of the overweight. This analysis reveals that not only have more children become OW in the last three decades, but OW children have been getting heavier.