Public health surveillance of obesity describes changes over time and identifies subgroups at risk of obesity-related consequences. We analyzed trends, stratified by race and Hispanic origin, in high weight for length, obesity, and severe obesity in the US from 1999 to 2018.

Background Data from the NHANES indicate that BMI has increased in some subgroups of children and adolescents in the United States over the past 20 y; however, BMI is an indirect measure of body fatness. Objectives We assessed changes in DXA-derived measures of adiposity in a nationally representative population of US children and adolescents aged 8–19 y from 1999–2006 to 2011–2018. Methods Using data from the NHANES, we compared the means and distributions of DXA-derived percentage body fat (%BF) and fat mass index (FMI; fat mass/height2 in kg/m2) between 1999–2006 (n = 10,231) and 2011–2018 (n = 6923) among males and females by age group, race and Hispanic origin, and BMI categories. Estimates were standardized by age and race and Hispanic origin. Results From 1999–2006 to 2011–2018, mean %BF increased from 25.6% to 26.3% (change in %BF: 0.7%; 95% CI: 0.2%, 1.2%; P < 0.01) among all males, whereas mean %BF increased from 33.0% to 33.7% (change in %BF: 0.7%; 95% CI: 0.2%, 1.2%; P = 0.01) and mean FMI increased from 7.7 to 8.0 fat mass kg/m2 (change in FMI: 0.3 fat mass kg/m2; 95% CI: 0.0, 0.6 fat mass kg/m2; P = 0.02) among all females. Changes were not consistent across all age, race and Hispanic origin, and BMI categories. Both %BF and FMI increased among Mexican-American children and adolescents, but not other race and Hispanic origin groups. Conclusions Among US children and adolescents, DXA-derived measures of adiposity increased from 1999–2006 to 2011–2018, albeit not consistently in every age, race and Hispanic origin, and BMI subgroup. These data reinforce the need to consider other measures, besides BMI categories, when studying adiposity in children and adolescents.

Summary 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.

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