International Journal of Obesity (1997) 21, 1167±1175 ß 1997 Stockton Press All rights reserved 0307±0565/97 $12.00 Age- and maturity-related changes in body composition during adolescence into adulthood: The Fels Longitudinal Study SS Guo, WC Chumlea, AF Roche and RM Siervogel Division of Human Biology, Departments of Community Health and of Pediatrics, Wright State University School of Medicine, Yellow Springs, OH, USA OBJECTIVES: To examine patterns of change in total body fat (TBF), percent body fat (%BF), and fat-free mass (FFM), from 8±20 y of age and the effect of rate of skeletal maturation. To determine the degree of tracking of body composition for individuals from childhood into adulthood. RESEARCH DESIGN: Annual serial data for TBF, %BF and FFM from underwater weighing using a multicomponent body composition model were collected from 130 Caucasian males and 114 Caucasian females between 1976 and 1996. Rate of maturation was de®ned as FELS skeletal age (SA) less chronological age (CA). Random effects models were used to evaluate general patterns of change and tracking of individual serial data over the 12 y age range. RESULTS: Changes in TBF followed a quadratic model for males and for females with declining rates of change. Changes for %BF followed a cubic model for males and females. General patterns of change for FFM followed a cubic model for males and a quadratic model for females. TBF for males and females increased with age, but the rates 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 change 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 increased thereafter. FFM for males and females increased with age, but the rates of change decreased with age. The extent of tracking is inversely related to the length of the time interval. At the same age, rapidly-maturing children have signi®cantly larger amounts of TBF, %BF and FFM than slow- maturing children. Tracking in body composition for individuals 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 rates of maturation; (3) signi®cant tracking in body composition for individuals persists from childhood to adulthood. Keywords: body composition; maturation; patterns of change Introduction %BF and FFM for individuals from childhood into adulthood has not been reported. Understanding and quantifying the patterns of change in body composi- Changes in body composition occur in conjunction tion and the tracking of levels of body composition with growth in body size and shape during adoles- from childhood into adulthood, would allow the early cence.1 Growth produced changes in total body fat recognition of children and adolescents with aberrant (TBF), percent body fat (%BF) and fat-free mass changes and=or unusual levels of body composition. (FFM) during childhood affect adult body composi- This knowledge would facilitate their subsequent tion and fat distribution, all of which, in turn, affect management. risk factors for cardiovascular and related diseases.1±4 Our knowledge of the changes in body composi- However, there is a paucity of knowledge regarding tion, from childhood into adulthood, depends on the the long-term patterns of change in body composition availability of long-term serial studies of children, but from childhood into adulthood. The tracking of available serial data are scant. Most reports of changes indices of body composition such as the body mass in body composition during childhood and adoles- index (BMI) from childhood into adulthood has been cence have used cross-sectional data,1,8,9 or were reported.5,6 BMI values at an age are highly correlated based upon changes in estimates of body composition with concurrent measures of TBF and %BF7 and from indirect methods.10,11 Analyses of limited serial indicate potential risk for obesity later in adulthood.6 data, have been reported by Chumlea and collea- However, the tracking of measured values for TBF, gues.12,13 These investigators reported annual incre- ments in body composition variables for 69 children Correspondence: Shumei S Guo, PhD, Department of aged 10±18 y, using data from the Fels Longitudinal Community Health, Wright State University School of Medicine, Study. These short term serial data, permitted simple 1005 Xenia Avenue, Yellow Springs, OH 45387-1695, USA. descriptions of changes, based upon two or three E-mail: [email protected] Received 19 February 1997; revised 14 July 1997; accepted 6 consecutive annual examinations only. These data August 1997 were insuf®cient for modelling individual patterns of Age- and maturity-related changes in body composition SS Guo et al 1168 change over time or for relating changes to subsequent pant's birthdays from 1976 to 1988. Because of the adult outcomes. timing of scheduled visits and the ages of the partici- It is well recognized that there is a relationship pants at the beginning and the end of this period of data between the maturation of a child and his or her collection, some participants had incomplete data sets growth and development, especially during adoles- within the age range of the analysis. Some participants cence. Using data from the Fels Longitudinal Study, were older than 8 y when the measurements began in Reynolds14 demonstrated that early sexual maturity in 1976, and some were younger than 23 y when the most girls and boys, aged 6±16 y, based upon secondary recent data for the present analysis were recorded. The gender characteristics, was related to increased rates absence of these values did not alter the descriptions of of growth in radiographic measures of muscle and the changes that occurred in body composition. The subcutaneous adipose tissue. Similar ®ndings have inclusion of serial data up to the age of 23 y in the been reported by others.15,16 However, these earlier analysis improved the accurate description of the pat- studies were not able to incorporate the rate or level of terns of change near the age of 20 y. maturation, with concurrent changes in body compo- sition over long time periods, into multivariate serial analytical models. Body composition methods The present study examined the pattern of age- Measures of TBF, %BF and FFM were obtained from related changes in TBF, %BF and FFM during a 12 y a multicomponent body composition model. The age- age range, from childhood and adolescence to young and gender-speci®c values for the concentrations of adulthood. We addressed three questions. First, what the major constituents of FFM were used to calculate values for its density in different age groups for each were the age- and gender-speci®c patterns of change 18 18 in TBF, %BF and FFM from 8±20 y of age? The gender. We smoothed the Lohman values for the patterns of change in TBF, %BF and FFM were density of FFM by using a ®xed-knot cubic spline technique and calculated FFM from body density modelled, and the annual rates of change for body 19 composition were derived. Secondly, what was the using these smoothed values. Let d1 be the density effect of the rate of biological maturation on the and d2 be the density of fat (0.9 g=cc). The value for %BF is: patterns of change in body composition values? Indices of rates of maturation were incorporated into 1 d d d %BF 1 2 2 Â 100; the analysis to evaluate their effects on changes in BD d d d d body composition during adolescence. Thirdly, what 1 2 1 2 was the extent of the tracking of body composition and TBF and FFM can be obtained from %BF as: from childhood into young adulthood? The likelihood TBF W Â %BF and FFM W 1 %BF: of individuals remaining in the same percentile chan- nel in body composition over time was evaluated. The Body density was determined from underwater weigh- sensitivity and speci®city of childhood and adolescent ing and residual volume, which was measured on a body composition measures, as predictors of adult Gould 2100 computerized spirometer.19 In the multi- values, were computed. component model, the density of the fat-free compo- nent varied due to changes in its water and bone mineral content.18,19 Stature was measured to 0.1 cm on a Holtain stadiometer, (Seritex, Carlstadt, NJ, USA) and weight was measured to 0.1 kg on a beam Subjects and Methods balance scale. The data for the present study were from 130 Cauca- Maturational data sian males and 114 Caucasian females, all of whom Skeletal ages were assessed using the FELS method20 are participants in the Fels Longitudinal Study in from left hand-wrist radiographs obtained on the same southwestern Ohio. The Fels Longitudinal Study 17 day as the body composition measures. Rate of started in 1929 and has been described in detail. maturation was de®ned as skeletal age (SA) of the Participants enter the Fels Longitudinal Study at or left hand-wrist less chronological age (CA), that is, before birth and are followed at regularly scheduled SA 7 CA. For each participant, the average of visits. Body composition measures start at the age of SA 7 CA over the period from 8 y to maturity was 8 y. For the present analysis, we included participants obtained. A participant with an average value > 1 who had at least 6 serial body composition measures indicated a tendency for rapid maturation; a partici- taken between the ages of 8 and 23 y.