Familial resemblance in fatness and fat distribution

Abstract

The purpose of the study was to estimate the degree of familial resemblance in anthropometric indicators of fatness and fat distribution. The sample consisted of 327 Caucasian participants from 102 nuclear families. Indicators 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 included WAIST adjusted for BMI (WAIST(ADJ)), the trunk-to-extremity skinfold ratio, adjusted for SF6 (TER(ADJ)), and the first principal component of skinfolds, adjusted for the mean skinfold of the individual (PC1). A general familial correlation model was fit to the data, and a series of nested reduced models were also fit so as to test hypotheses about familial resemblance. The hypothesis of no familial resemblance (all familial correlations are zero) was rejected for all phenotypes, indicating that fatness and fat distribution aggregate within families. For the three indicators of fatness (BMI, SF6, and WAIST), the sibling and parent-offspring correlations were significant. Further, there were no sex or generation differences in the familial correlations. For the three indicators of fat distribution (TER(ADJ), WAIST(ADJ), and PC1), there was no parent-offspring resemblance; sibling resemblance was significant for TER(ADJ) and PC1. Further, spouse resemblance was not significant for WAIST(ADJ), but was for TER(ADJ) and PC1. For both WAIST(ADJ) and PC1 there were significant sex differences in the familial correlations. A combination of models including no sex or generation differences and no spouse resemblance was the most parsimonious model for BMI, SF6, and TER(ADJ). The environmental model (all correlations equal) was the most parsimonious for WAIST, the model of no sibling resemblance was the most parsimonious for WAIST(ADJ), and the model of no spousal resemblance was the most parsimonious for PC1. Estimates of maximal heritability range from 46-60% for fatness and from 29-48% for fat distribution, independent of overall fatness, suggesting that in this sample the heritability of fatness is greater than that for fat distribution. Further, the pattern of correlations, which generally includes no spousal resemblance but significant parent-offspring and sibling correlations, suggests the role of genes in explaining at least part of the heritability. Am. J. Hum. Biol. 12:395-404, 2000. Copyright 2000 Wiley-Liss, Inc.