Familial resemblance in fatness and fat distribution

The purpose of the study was to estimate the degree of familial resemblance in anthropometric indicators of fatness and fat distribution. The sample c onsisted of 327 Caucasian participants from 102 nuclear families. Indicator s of fatness included the body mass index (BMI), the sum of six skinfolds ( SF6: triceps + biceps + medial calf + subscapular + suprailiac + abdominal) , and waist circumference (WAIST), while indicators of fat distribution inc luded WAIST adjusted for BMI (WAIST(ADJ)), the trunk-to-extremity skinfold ratio, adjusted for SF6 (TERADJ), and the first principal component of skin folds, adjusted for the mean skinfold of the individual (PC1). A general fa milial correlation model was fit to the data, and a series of nested reduce d models were also fit so as to test hypotheses about familial resemblance. The hypothesis of no familial resemblance (all familial correlations are z ero) was rejected for all phenotypes, indicating that fatness and fat distr ibution aggregate within families. For the three indicators of fatness (BMI , SF6, and WAIST), the sibling and parent-offspring correlations were signi ficant. Further, there were no sex or generation differences in the familia l correlations. For the three indicators of fat distribution (TERADJ, WAIST (ADJ), and PC1), there was no parent-offspring resemblance; sibling resembl ance- was significant for TERADJ, and PC1. Further, spouse resemblance was not significant for WAIST(ADJ) but was for TERADJ and PC1. For both WAIST(A DJ) and PC1 there were significant sex differences in the familial correlat ions. A combination of models including no sex or generation differences an d no spouse resemblance was the most parsimonious model for BMI, SF6, and T ERADJ. The environmental model tall correlations equal) was the most parsim onious for WAIST, the model of no sibling resemblance was the mast parsimon ious for WAIST(ADJ), and the model of no spousal resemblance was the most p arsimonious for PC1. Estimates of maximal heritability range from 46-60% fo r fatness; and from 29-48% for fat distribution, independent of overall fat ness, suggesting that in this sample the heritability of fatness is greater than that for fat distribution. Further, the pattern of correlations, whic h generally includes no spousal resemblance but significant parent offsprin g and sibling correlations, suggests the role of genes in explaining at lea st part of the heritability. (C) 2000 Wiley-Liss, Inc.