Subcutaneous fatness and stature: Relationship from infancy to adulthood

Patterns of change in relationships between stature and radiographic fat thicknesses at medial calf and 10th rib sites were investigated using serial records of participants in the Fels Longitudinal Study. Cubic polynomials of fat thicknesses were fitted stepwise relative to recumbent length or stature within selected sex- and age-specific groups from 6 months of age to adulthood. Resultant values of r² and R² were smoothed across age using a resistent nonlinear smoothing procedure. The general age-related pattern in the magnitude of associations between fat thicknesses and stature is one of rather low levels in infancy, followed by increasing correlations through middle childhood and pubescence, and decreasing in late adolescence toward generally low levels in young adulthood. Adult levels of about 3-5% shared variance of fat thickness and stature are present in each sex by about 17-18 years of age, except for 10th rib fat thickness and stature associations in males, where adult associations are greater than at all earlier ages. There is a shift from a generally linear relationship in infancy and early childhood to a positively asymptotic curvilinear relationship between 7 and 11 years in boys and 9 and 14 years in girls. This curvilinearity was more evident at the 10th rib site than at the calf site, and was more pronounced in females than males.