Familial aggregation of subcutaneous fat patterning: Principal components of skinfolds in the Québec family study

Familial resemblance was examined for each of the principal components arising from an analysis of six skinfolds (triceps, biceps, subscapular, abdominal, suprailiac, and medial calf) measured in 1,237 participants of the Québec Family Study. Most of the phenotypic variance among the skinfolds (83%) was accounted for by the first two principal components. Examination of the skinfold loadings on each principal component, as well as intraindividual cross-trait correlations with other body composition and fat pattern measures (body mass index; total fat mass and fat-free mass estimated from body density obtained through underwater weighing; the sum of six skinfolds; and the ratio of trunk to extremity skinfolds) support the interpretation of the first component as a general measure of adiposity and the second component as a trunk-extremity contrast. Parent-child and sibling correlations for each of the two principal components indicate that familial effects reach 46% (general) and 52% (trunk-extremity). Although the eigenvalues for the remaining four principal components (accounting for 17% of the variance) are <1.0, it is noteworthy that each exhibits significant familial resemblance (31–60%). Further, the intraindividual correlations for the additional four components with the other body size indicators are quite low, suggesting that they capture somewhat different aspects of relative fat distribution. © 1996 Wiley-Liss, Inc.