Longitudinal analysis of changes in indices of obesity from age 8 years to age 18 years. Project heartbeat!

To compare growth patterns of obesity indices derived from body composition and anthropometric measures, the authors analyzed data from Project HeartBeat!, a longitudinal study of cardiovascular disease risk factors in childhood and adolescence. A total of 678 children initially aged 8, 11, and 14 years in The Woodlands and Conroe, Texas, were enrolled and followed with 4-monthly examinations between October 1991 and August 1995. Trajectories of change from age 8 years to age 18 years were estimated for body mass index, percent body fat, abdominal circumference, the sum of two skinfolds, and the sum of six skinfolds. All indices varied importantly with age. Percent body fat, sum of two skinfolds, and sum of six skinfolds shared similar growth patterns, with strong divergence between males and females. Males' body fat decreased with age and females' increased or remained nearly constant with age. In contrast, both body mass index and abdominal circumference increased monotonically with age in both sexes, exhibiting little sex difference as children reached late adolescence. Sex differences were more striking among Blacks than among non-Blacks. The authors conclude that growth patterns of adiposity differ according to the measure chosen. Furthermore, changes in different obesity indices may not relate in the same way to changes in blood pressure or blood lipid concentrations.