Demographic and socioeconomic correlates of adiposity assessed with dual-energy X-ray absorptiometry in US children and adolescents

Background: Associations between demographic-socioeconomic characteristics and childhood obesity are complex in the United States. Objective: We examined associations between demographic-socioeconomic characteristics (age, sex, race-ethnicity, family income, household size, and birthplace) and adiposity measured by dualenergy X-ray absorptiometry in US children. Design: Data were from 8-19-y-old US children enrolled in NHANES 2001-2004 (n = 5436). Adiposity was expressed as the fat mass index (FMI = fat mass/height²; in kg/m²), percentage body fat (%BF), and prevalence of normal, overfat, and excess fat corresponding to %BF <25%, 25-29.9%, and ≥30% in boys and <30%, 30-34.9%, and ≥35% in girls, respectively. We used sexspecific linear and multinomial logistic regression models adjusted for demographic-socioeconomic factors. Results: The prevalence of excess fat was higher in Mexican American (36%) than in white (28%; P ≤ 0.10) and black (21%; P < 0.05) boys; higher in Mexican American (44%) than in white (36%; P ≤ 0.10) and black (35%; P < 0.05) girls; and higher in US-born (38%) than in foreign-born (29%; P ≤ 0.10) Mexican American boys. In boys, %BF was higher in Mexican Americans and lower in blacks than in whites (P < 0.05). Adiposity was negatively associated with family income in white boys and girls and in Mexican American girls (P < 0.05). Racial-ethnic disparities in adiposity persisted (P < 0.001) after control for demographic-socioeconomic factors available in NHANES. The R² for sex-specific models of %BF or FMI regressed on age, race-ethnicity, family income, household size, and birthplace ranged from 2% to 11%. Conclusion: The association between demographic-socioeconomic factors and adiposity among US children varied substantially by age, sex, and race-ethnicity.