[Birth weight predicts physical indicators in adulthood: a large population-based study in Chinese twins].

To quantitate the association between birth weight and phenotypes of physical indicators in adulthood, i.e. BMI and waist circumference (WC) and to what degree genetic or environmental factors affect birth weight-obesity association. A total of 6 623 gender matched twin pairs aged 25 to 79 years were recruited through the Chinese National Twin Registry. The twins reported their own birth weight, current height and weight, and WC using a self-administered questionnaire. BMI was calculated according to the self-reports of body height and weight. Within twin-pair design was used to quantitate the association between birth weight and phenotypes related to obesity while bivariate structural equation models were used to decompose the phenotype correlation. After adjusted for multiple factors, twin-pair analyses within monozygotic (MZ) showed that, on average, a 1.0 kg increase in birth weight corresponded to an increase of 0.33 kg/m(2) in BMI and 0.95 cm in WC in adulthood (<0.001). Bivariate structural equation models showed significant positive unique environmental correlation between birth weight and the two obesity-related phenotypes. The study supported the role of twin-specific supply line factors on relationship between birth weight and physical indicators in adulthood.