Familial clustering of multiple measures of adiposity and fat distribution in the Québec Family Study: a trivariate analysis of percent body fat, body mass index, and trunk-to-extremity skinfold ratio.
OBJECTIVE
To assess whether independent or common (pleiotropic) familial factors (i.e., genetic and/or common environment) underlie the observed associations among measures of body mass, body fat, and its distribution.


METHODS
A familial correlation model involves both parents and offspring, and gives rise to three types of familial correlations (spouse, parent-offspring, and sibling). A pattern of significant familial correlations suggests that the trait is determined by familial factors (i.e., genetic and/or environmental heritability). Cross-trait familial correlations are also estimated, both within individuals (intraindividual) and between family members (interindividual). Interindividual cross-trait familial correlations (e.g., trait 1 in parents with trait 2 in offspring) lead to the same type of familial inferences regarding bivariate heritabilities.


METHODS
Measures of total body fat (% body fat-%BF), fat distribution (trunk/extremity skinfold ratio-TER), and body mass index (BMI) were assessed in 1239 individuals from 309 nuclear families participating the Québec Family Study.


RESULTS
All three adiposity measures are cross-correlated within individuals. However, interindividual cross-trait correlations, which alone are capable of suggesting common familial determinants, are significant only for BMI with each of %BF and TER (bivariate heritabilities of 10% and 18%, respectively), and not for %BF and TER.


CONCLUSIONS
Although all three adiposity measures are correlated within individuals, there appear to be entirely different underlying genes and/or environmental factors influencing the adiposity phenotypes of total body fat and fat distribution. The BMI, however, apparently shares some familial determinants with both total body fat and fat distribution.
Rice
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Division of Biostatistics, Washington University School of Medicine, St. Louis, Missouri 63110, USA. treva@wubios.wustl.edu
Bouchard
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Pérusse
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Rao
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D000293:Adolescent; D000328:Adult; D001823:Body Composition / Q000235:genetics* / Q000502:physiology*; D015992:Body Mass Index; D002648:Child; D002675:Child, Preschool; D016000:Cluster Analysis; D005192:Family Health; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D008957:Models, Genetic; D015233:Models, Statistical; D010641:Phenotype; D011792:Quebec; D012885:Skinfold Thickness; D013223:Statistics as Topic