FAT AND FAT-FREE BODY COMPOSITION IN CHILDREN

The purpose of this study is to investigate variation in the fat-free body
composition of children and youth as a function of maturation, sex and
racial background so that a more accurate estimation of body fatness can be
developed for such methods as densitometry, hydrometry, 40K spectrometry
and anthropometry. Previous research using a cross-sectional design has
established a lower density of the fat-free body in black and white
children than for the adult. As a result, body fatness is overestimated in
children when adult equations are used to estimate their body composition.
The proposed investigation is designed to measure changes in the fat-free
body composition in a longitudinal sample to provide more definitive
estimates of the extent of chemical immaturity in children. Furthermore,
additional populations of children with obesity or with a history of high
physical activity will be studied for their variation in fat-free body
composition and compared to the cross-sectional data base established
during the past two years. Components of the fat-free body to be measured
in all subjects include total body water using deuterium oxide dilution,
bone mineral content of the cross-section of the radius and ulna by photon
absorptiometry, body potassium by whole-body 40K spectrometry, body density
by underwater weighing and functional residual lung volume, and
anthropometry. The relationship between anthropometry and body density
will also be studied by obtaining data from several laboratories throughout
the country. In this way, it will be possible to establish interlaboratory
standards for the anthropometric-body composition relationship in
children. Thus, this research is designed to contribute to improved body
composition estimates in children for both research and clinical
applications. The widespread use of anthropometry for the estimation of
body composition in children has not been properly established and is
needed to improve methodological approaches leading to more accurate
assessment of both overweight (obesity) and minimal weight conditions in
the childhood population.