Familial resemblance of 7-year changes in body mass and adiposity

Objective: To investigate the familial resemblance of 7-year changes in body mass and adiposity among Canadian families. Research Methods and Procedures: The sample consisted of 655 women and 660 men from 521 families who participated in the Canada Fitness Survey in 1981 and the follow-up Campbell's Survey in 1988. Indicators of baseline and 7-year changes in body mass and adiposity included body mass (kilograms), body mass index (BMI; kilograms per square meter), sum of five skinfolds (SF5; millimeters), and waist circumference (WC; millimeters). The data were adjusted for the effects of age and sex, and the change scores were adjusted for baseline levels. A familial correlation model was used to determine the heritability of each phenotype using maximum likelihood techniques. Results: Significant familial resemblance was observed at baseline and for 7-year changes in all phenotypes. At baseline, moderate heritabilities were observed [body mass: heritability coefficient (h(2)) 56%; BMI, h(2) = 39%; SF5, h(2) = 41 %; and WC, h(2) 39%], whereas values were attenuated for each change score except for WC (Deltabody mass, h(2) 23%; DeltaBMI, h(2) = 14%; DeltaSF5, h(2) = 12%; and WC, h(2) 45%). Discussion: Changes in body mass and adiposity significantly aggregate within families over 7 years. However, baseline values are characterized by higher heritability levels except WC. The significant heritabilities observed for change scores suggest that lifestyle, transient environmental factors, and possibly age-related gene effects are important determinants of changes in body mass and adiposity.