ABSTRACT
The possible contribution of genetic factors to individual differences in human fatness or its extreme variant, obesity, must be seen on the background of the evident strong environmental influences, even under conditions of unrestricted food supply. The idea of the adoption method is that resemblance in the trait between the adoptee and the members of the biological family presumably is due to shared genes, whereas resemblance between the adoptee and the members of the adoptive family presumably is due to shared family environment. Since 1964 nine studies have used adoptees or foster children in the study of fatness. It is assumed that the biological-adoptee-adoptive family set is representative of the background population of natural families in terms of the role of genetic and environmental factors affecting the trait. Large population studies show minor gender-related differences which the available adoption studies probably do not have the power to detect.
