Physical activity attenuates genetic effects on BMI: Results from a study of Chinese adult twins.

<bold>Objective: </bold>This study aimed to examine the gene-environment interaction of physical activity and body mass index (BMI) using the Chinese National Twin Registry (CNTR).<bold>Methods: </bold>A total of 19,308 same-sex adult twins from CNTR were included in the analysis. Twin zygosity was determined by self-reported questionnaire. Height and weight were measured using self-reported questionnaire. The vigorous physical activity was defined as greater or equal to five times a week of at least 30 min moderate- or high-intensity physical activity. A twin structural equation model was used to analyze the gene-environment interaction of vigorous exercise with BMI among 13,506 monozygotic twins and 5,802 dizygotic twins.<bold>Results: </bold>A structural equation model adjusting for age and sex found vigorous exercise significantly moderated the additive genetic effects (P < 0.001) and shared environmental effects (P < 0.001) on BMI. The genetic contributions to BMI were significantly lower for people who adopted a physically active lifestyle [h(2) = 40%, 95% confidence interval (CI): 35%-46%] than those who were relative sedentary (h(2) = 59%, 95% CI: 52%-66%). The observed gene-physical activity interaction was more pronounced in men than women.<bold>Conclusions: </bold>Our results suggested that adopting a physically active lifestyle may help to reduce the genetic influence on BMI among the Chinese population. [ABSTRACT FROM AUTHOR]