Body composition in children and adults by air displacement plethysmography

Abstract

Objectives: Air displacement plethysmography (ADP) may provide a partial alternative to body density (B_d) and therefore body composition measurement compared to conventional hydrodensitometry (H_d) in children. As there are no evaluation studies of ADP in children, this study had a two-fold objective: to compare B_d estimates by ADP and H_d; and to compare fat estimates by both ADP and H_d to fat estimates by another reference method, dual energy X-ray absorptiometry (DXA).

Setting: Obesity Research Center, St. Luke’s/Roosevelt Hospital, New York, USA.

Subjects: One hundred and twenty subjects (66 females/54 males) who ranged in age from 6–86 y and in body mass index (BMI, kg/m²) from 14.1–40.0 kg/m² met study entry criteria.

Study Design: Cross-sectional study of healthy children (age≤19 y) and adult group for comparison to earlier studies. Each subject completed ADP, H_d, and DXA studies on the same day. Only subjects with subjectively-judged successful H_d studies were entered into the study cohort.

Results: There was a high correlation between B_d by ADP and H_d (B_d Hd=0.11+0.896×B_d ADP; r=0.93, SEE=0.008 g/cm³, P<0.0001), although the regression line slope and intercept differed significantly from 1 and 0, respectively. Additional analyses localized a small-magnitude B_d bias in the child (n=48) subgroup. Both ADP and H_d%fat estimates were highly correlated (r>0.9, P<0.0001) with%fat by DXA in child and adult subgroups. Bland–Altman analyses revealed no significant%fat bias by either ADP or H_d vs DXA in either children or adults, although a bias trend (P=0.11) was detected in the child subgroup.

Conclusion: With additional refinements, the air displacement plethysmography system has the potential of providing an accurate and practical method of quantifying body fat in children as it now does in adults.

Sponsorship: This study was in-part supported by NIH Grants RR00645, NIDDK 42618 and NIDDK 37352.