Weight changes in adult twins.

Longitudinal study of 514 pairs of US white male twin veterans was made possible by compiling data from military records, mailed questionnaires, and physical examinations. Height and weight were used to calculate the Quetelet index for twins at different ages covering induction into the Armed Forces (generally 17-24 years), 25 years, 40-50 years at questionnaire response, and 42-56 at physical examination. Cross-sectional analyses of Quetelet Index at these 4 points in time showed consistent evidence of significant genetic variance. Additional twin analyses of change in Quetelet Index both from induction and from age 25 to approximately age 48 were done. Both analyses showed significant genetic variance for change in Quetelet Index during this time span of 25 or more years for most subjects. Heritability estimates were 0.6 for change in Quetelet Index from induction (mean age 20) to examination (mean age 48) and 0.7 for change in Quetelet Index from age 25 to examination. While studies of younger twins have shown significant genetic influence on growth (height and weight), this study of adults demonstrates significant genetic influence on change in weight even after maturation.