OBESITY RELATED PHENOTYPES IN FAMILIES SELECTED FOR EXTREME OBESITY AND LEANNESS

BACKGROUND: Obesity is a multigenic trait, and special methods and sam pling designs are needed for gene identification. OBJECTIVE: To descri be characteristics of families selected to increase information for ge netic linkage studies of obesity. DESIGN: Families having extremely ob ese siblings with a lean parent and sibling. SUBJECTS: 594 members of 94 Caucasian families. MEASUREMENTS: Measured height and weight, bioel ectric impedance, skinfolds, circumferences and questionnaires. RESULT S: Families have an extreme range of obesity phenotypes, which are bim odally distributed. The obese individuals are predominantly women with an onset of obesity early in life. Obesity onset age was negatively c orrelated with level of obesity, and onset ages were correlated among family members. Individual obesity measures were highly correlated. Th e extreme range of phenotypes within families increases family variabi lity and presumably gene segregation. CONCLUSION: Sampling families th rough extremely obese sibling pairs with a lean parent and sibling res ults in families with an extreme range of obesity and leanness, The la rge within-family variance and early age of onset should make these fa milies highly informative for gene mapping and gene identification stu dies.