Body fat differences among US youth aged 8-19 by race and Hispanic origin, 2011-2018.

Background: The association between body mass index (BMI) and adiposity differs by race/ethnicity.

Objective: To examine differences in adiposity by race/Hispanic origin among US youth and explore how those differences relate to differences in BMI using the most recent national data, including non-Hispanic Asian youth.

Methods: Weight, height and DXA-derived fat mass index (FMI) and percentage body fat (%BF) from 6923 youth 8-19 years in the National Health and Nutrition Examination Survey (NHANES) 2011-2018 were examined. Age-adjusted mean BMI, FMI and %BF were reported. Sex-specific linear regression models predicting %BF and FMI were adjusted for age, BMI category and BMI category*race/Hispanic origin interaction.

Results: %BF was highest among Hispanic males (28.2%) and females (35.7%). %BF was lower among non-Hispanic Black (23.9%) compared with non-Hispanic White (26.0%) and non-Hispanic Asian (26.6%) males. There was no difference between non-Hispanic Black females (32.7%) and non-Hispanic White (33.2%) or non-Hispanic Asian (32.7%) females. FMI was higher among Hispanic youth compared with non-Hispanic White youth. Among youth with underweight/healthy weight, predicted %BF and FMI were lower among non-Hispanic Black males (-2.8%; -0.5) and females (-2.0%; -0.3), compared with non-Hispanic White youth, and higher among Hispanic males (0.9%; 0.2) and females (2.0%; 0.5), while %BF but not FMI was higher among non-Hispanic Asian males (1.3%) and females (1.4%). Among females with obesity, non-Hispanic Asian females had lower %BF (-2.3%) and FMI (-1.7) than non-Hispanic White females.

Conclusions: Differences in %BF and FMI by race/Hispanic origin were not consistent by BMI category among US youth in 2011-2018.