Visceral, subcutaneous, and total fat mass accumulation in a prospective cohort of adolescents

Abstract

Background: Race and sex differences in adolescents' body fat are demonstrated in cross-sectional cohorts, yet a longitudinal design would better identify patterns of fat distribution over time.

Objectives: The aim was to examine race and sex differences in adiposity between black and white adolescents over 2 y.

Methods: A cohort of adolescents aged 10-16 y (38% black; 52% girls; 15% overweight, 34% with obesity) underwent body composition measurements at baseline (n = 309) and 2 y later (n = 236), using DXA to quantify whole-body fat mass (FM) and MRI for abdominal subcutaneous (SAT) and visceral adipose tissue (VAT) volumes. General linear models were used to examine race and sex differences in log-transformed FM, SAT, and VAT, adjusting for age, sexual maturation, extended BMI percentile, and race-by-sex interaction. SAT and VAT models in addition controlled for baseline FM and change in FM (for change models).

Results: Mean (95% CI) baseline FM (kg) was higher among white [18.5 (17.9, 19.2) than among black adolescents [17.4 (16.6, 18.2), P = 0.03] and girls [19.5 (18.8, 20.3) than boys [16.5 (15.8, 17.2), P < 0.0001]. Mean (95% CI) baseline SAT (L) was higher among girls [4.4 (4.2, 4.6)] than among boys [3.9 (3.7, 4.1), P < 0.0001]. Mean (95% CI) baseline VAT (L) was higher among white [0.5 (0.5, 0.6)] than among black [0.3 (0.3, 0.4)] adolescents (P < 0.0001) and boys [0.5 (0.4, 0.5)] than girls [0.4 (0.4, 0.4), P = 0.04]. Over 2 y mean (95% CI) FM change (kg) was higher among white [3.7 (2.9, 4.5)] than among black adolescents [2.3 (1.3, 3.3), P = 0.04] and girls [4.0 (3.0, 4.9)] than boys [2.0 (1.1, 3.0), P = 0.007], but SAT change (L) did not differ by race or sex. VAT change (L) was higher among white [0.1 (0.1, 0.1)] than among black adolescents [0.0 (0.0, 0.1), P = 0.003] and boys [0.1 (0.1, 0.1)] than girls [0.0 (0.0, 0.1), P = 0.034].

Conclusions: Sex and race differences in the deposition and accumulation of excess fat are important considerations for understanding obesity prevalence and obesity-related disease risk among adolescents.This trial was registered at clinicaltrials.gov as NCT02784509.

Keywords: African Americans; abdominal fat/diagnostic imaging; adipose tissue/anatomy and histology; ectopic fat; intra-abdominal fat/diagnostic imaging; longitudinal studies; obesity/ethnology; racial groups/genetics; sex characteristics.

FIGURE 1

Least-squares adjusted means from general linear models reporting race- and sex-specific baseline FM adjusted for age and sexual maturation (A); baseline abdominal SAT volume adjusted for age, sexual maturation, and total FM (B); and baseline VAT volume adjusted for age, sexual maturation, and total FM (C). n = 307 (49 black boys, 67 black girls, 99 white boys, 92 white girls). Values are reverse transformed from the ln. Error bars indicate 95% confidence limits. FM, fat mass; SAT, subcutaneous adipose tissue; VAT, visceral adipose tissue.

FIGURE 2

Least-squares adjusted means from general linear models reporting race- and sex-specific change over 2 y in FM adjusted for age and sexual maturation (n = 229; 34 black boys, 50 black girls, 77 white boys, 68 white girls) (A); abdominal SAT volume adjusted for age, sexual maturation, total FM, and change in FM (n = 224; 32 black boys, 49 black girls, 77 white boys, 66 white girls) (B); and VAT volume adjusted for age, sexual maturation, total FM, and change in FM (n = 225; 35 black boys, 51 black girls, 74 white boys, 65 white girls) (C). Values are reverse transformed from the ln. Error bars indicate 95% confidence limits. FM, fat mass; SAT, subcutaneous adipose tissue; VAT, visceral adipose tissue.