AGE-RELATED AND MATURITY-RELATED CHANGES IN BODY-COMPOSITION DURING ADOLESCENCE INTO ADULTHOOD - THE FELS LONGITUDINAL-STUDY

OBJECTIVES: To examine patterns of change in total body fat (TBF), per cent body fat (%BF), and fat-free mass (FFM), from 8-20y of age and th e effect of rate of skeletal maturation. To determine the degree of tr acking of body composition for individuals from childhood into adultho od. RESEARCH DESIGN: Annual serial data for TBF, %BF and FFM from unde rwater weighing using a multicomponent body composition model were col lected from 130 Caucasian males and 114 Caucasian females between 1976 and 1996. Rate of maturation was defined as FELS skeletal age (SA) le ss chronological age (CA). Random effects models were used to evaluate general patterns of change and tracking of individual serial data ove r the 12y age range. RESULTS: Changes in TBF followed a quadratic mode l for males and for females with declining rates of change. Changes fo r %BF followed a cubic model for males and females. General patterns o f change for FFM followed a cubic model for males and a quadratic mode l for females. TBF for males and females increased with age, but the r ates of change declined with age. %BF for females increased from age 8 -20 y. For males, %BF increased with age, but the positive rates of ch ange declined and became a negative when aged about 13 y and reached a minimum at about the age of 15 y. The rate of change for %BF increase d thereafter. FFM for males and females increased with age, but the ra tes of change decreased with age. The extent of tracking is inversely related to the length of the time interval. At the same age, rapidly-m aturing children have significantly larger amounts of TBF, %BF and FFM then slow-maturing children. Tracking in body composition for individ uals persisted from childhood to adulthood. CONCLUSIONS: (1) There are gender-associated differences in these patterns of change for %BF and FFM but not for TBF; (2) TBF, %BF and FFM increased with increased ra tes of maturation; (3) significant tracking in body composition for in dividuals persists from childhood to adulthood.