GENETIC INFLUENCES ON CHANGES IN BODY BASS INDEX - A LONGITUDINAL ANALYSIS OF WOMEN TWINS

Numerous studies have demonstrated genetic influences on body fat, but there also may be genetic effects on its intraindividual variation ov er time, This study examined changes in body mass index (BMI) using lo ngitudinal data from two examinations of the Kaiser Permanente Women T wins Study, performed a decade apart, The analysis included 630 women, 185 monozygotic and 130 dizygotic twin pairs, with average ages of 41 years and 51 years at the two examinations, respectively, Age-adjuste d heritability estimates for the change in BMI over the decade ranged from 0.57 to 0.86 (all p less than or equal to 0.001) using three diff erent statistical analysis approaches, indicating that at least half, and possibly as much as 85%, of the variance in the change in BMI is a ttributable to genetic influences under a polygenic model, These estim ates remained statistically significant after adjusting for environmen tal factors (ranging from 0.57 to 0.78) and with additional adjustment for BMI at baseline (ranging from 0.41 to 0.79), although dizygotic i ntraclass correlations were low after these adjustments. Thus, in addi tion to known environmental and behavioral influences, these results p rovide evidence for genetic influences on changes in BMI over a decade in women.