Percent body fat and chronic disease risk factors in U.S. children and youth.

BACKGROUND The dramatic increase in pediatric obesity has renewed interest in accurate methods and screening indexes for identifying at-risk children and youth. Whether age-specific standards are needed is a factor that remains uncertain. PURPOSE This study was designed to describe the age-specific fatness-risk factor relationship in boys and girls across a wide age range. METHODS Data were from 12,279 white, black, and Mexican-American children and adolescents from the National Health and Nutritional Examination Surveys (NHANES) III (1998-1994) and IV (1999-2004). Children were grouped based on percent fat, estimated from subscapular and triceps skinfolds, and the age-specific relationships between percent fat and chronic disease risk factors (e.g., blood pressure, lipids and lipoprotein levels, glucose, insulin, and circulating C-reactive protein levels) were described in boys and girls, aged 6-18 years. RESULTS Percent fat was significantly related to risk factor levels. At higher levels of percent fat, the prevalence of adverse cardiovascular disease risk factors was higher, particularly above 20% fat in boys and above 30% fat in girls. In boys and girls, the interaction term age by percent fat was a significant predictor of risk factors, whereas the percent fat by race interaction term was nonsignificant. CONCLUSIONS The results demonstrate a strong relationship between chronic disease risk factors and percent fat in children and youth that varies by age in boys and girls.