Changes in adiposity among children and adolescents in the United States, 1999-2006 to 2011-2018

Abstract

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.

Keywords: DXA; NHANES; US children and adolescents; adiposity; body fatness; dual-energy X-ray absorptiometry; fat mass index; percentage body fat.

FIGURE 1

Crude means of adiposity measures by sex, survey years, and 6-mo age intervals—United States, 1999–2006 and 2011–2018. (A) Mean %BF, (B) mean FMI. Estimates were calculated using examination sample weights and accounted for the survey's complex, multistage probability design. For 1999–2006, imputed data were included; means were averaged across imputations. Overall sample sizes: males during 1999–2006, n = 5933; males during 2011–2018, n = 3584; females during 2001–2006, n = 4298; females during 2011–2018, n = 3339. Source: National Center for Health Statistics, NHANES. For the 1999–2006 time period, female data include only 2001–2006. FMI, fat mass index; %BF, percentage body fat.

FIGURE 2

Change in mean %BF, mean FMI, and mean BMI among children and adolescents aged 8–19 y from 1999–2006 to 2011–2018 by age group, race and Hispanic origin, and BMI category—United States. (A) Among males, (B) among females. Estimates were calculated using examination sample weights and accounted for the survey's complex, multistage probability design. Mean differences were averaged across imputations. SEs were pooled across imputations using within-imputation and between-imputation variances. Significance testing was performed using a t-distribution with adjusted df. 95% CIs are provided. Overall sample sizes: males during 1999–2006, n = 5933; males during 2011–2018, n = 3584; females during 2001–2006, n = 4298; females during 2011–2018, n = 3339. Source: National Center for Health Statistics, NHANES. For the 1999–2006 time period, female data include only 2001–2006. Data for 1999–2006 (2001–2006 in females) are standardized to the sex-specific, race and Hispanic origin–specific, and 6-mo age–specific distributions of 2011–2018 to allow for comparison across time frames. ^*,**Significant change: *P < 0.05; **P < 0.01. FMI, fat mass index; %BF, percentage body fat.

FIGURE 3

Mean-difference plots for the differences in distribution of %BF and FMI among children and adolescents aged 8–19 y between 1999–2006 and 2011–2018—United States. (A) Among males, (B) among females. Plots show the difference for each quantile across time periods compared with the average of each quantile across time periods. For 1999–2006, imputed data were included; quantiles were averaged across imputations. Estimates were calculated using examination sample weights and accounted for the survey's complex, multistage probability design. The 10th, 50th, and 90th percentiles are marked by dotted lines. Overall sample sizes: males during 1999–2006, n = 5933; males during 2011–2018, n = 3584; females during 2001–2006, n = 4298; females during 2011–2018, n = 3339. Source: National Center for Health Statistics, NHANES. For the 1999–2006 time period, female data include only 2001–2006. Data for 1999–2006 (2001–2006 in females) are standardized to the sex-specific, race and Hispanic origin–specific, and 6-mo age–specific distributions of 2011–2018 to allow for comparison across time frames. FMI, fat mass index; %BF, percentage body fat.