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December 5, 1986

A Twin Study of Obesity-Reply

Author Affiliations

University of Pennsylvania School of Medicine Philadelphia
National Cancer Institute Bethesda, Md

JAMA. 1986;256(21):2959. doi:10.1001/jama.1986.03380210054010

In Reply.—  We appreciate Dr Knight's pointing out the importance of context in interpreting the findings of our twin study of obesity. As he notes, concordance rates and heritability estimates are critically dependent on the environment in which they are measured, and different environments can give rise to different estimates of heritability. The role of environment is particularly important in assessing obesity, in which gene-environment interaction must surely be of great importance. And as he (and we) have noted, such interaction is not measured in twin studies. This limitation makes it important to assess the role of genetics in human obesity by methods that can assess gene-environment interaction. Adoption studies constitute one such method, and a recent adoption study1 has confirmed the importance of genetic factors in human obesity.The data of our study do not, as Dr Knight says, support general conclusions regarding the relative roles of heredity