Impact of environmental and genetic factors on weight gain in adulthood

Nutrition Research Newsletter, Nov, 2004

Here is an inverse relationship between obesity measured by body mass index (BMI) and multiple indicators of socioeconomic status, including educational attainment, social class, or income level, especially among women. To further investigate the influence of environmental and genetic factors on education-associated disparities in self-reported BMI and weight change, twin study was employed. A twin study is a powerful tool for distinguishing the genetic and environmental factors influencing a phenotype or trait variation.

The data for this investigation was derived from the Finish Twin Cohort, which included 2482 monozygotic and 5113 dizygotic same-sex male and female twin pairs born between 1915 and 1957. Longitudinal postal surveys were performed at 3 points, 1975, 1981 and 1990. Height and body weight was self reported, as was demographic information including length of education and income status.

Education-associated differences in BMI and in weight change were clear in 1975 and 1981, respectively, whereas no differences were seen in weight change between 1981 and 1990 when age and baseline BMI were adjusted for. The trait correlation between baseline BMI and educational attainment (-0.15 in men and women) was mainly due to correlations between additive genetic factors that contributed to BMI in education in men (-0.20; 95% CI: -0.25, -.014) and women (-0.32; 95% CI: -.040, -0.25) when adjusted for age. Among women, a weaker positive correlation was found for the unshared environmental effects contributing to the 2 traits (0.06; 95% CI: 0.02, 0.12). The same factors that affected the association between education and BMI in 1975 largely explained the association between education and weight change in 1981.

These results indicate that common genetic factors affect both educational attainment and body weight, which in turn contribute to educational-associated differences in BMI during adulthood.

K. Silventoinen, S. Sarlio-Lahteenkorva, M. Koskenvuo, et al. Effect of environmental and genetic factors on education-associated disparities in weight and weight gain: a study of Finnish adult twins. Am J Clin Nutr; 80:815-822 (October, 20040). [Correspondence: K Silventoinen, Department of Public Health, University of Helsinki, PO Box 41, Mannerheiminitie 172, FIN-00014, University of Helsinki, Helsinki, Finland. E-mail: karri.silventoinen@helsinki.fi].