Does obesity run in families because of genes? An adoption study using silhouettes as a measure of obesity.

A number of studies, including the Danish adoption study, have shown that, in adults, the familial resemblance of obesity, as measured by the body mass index (weight in kg/(height in m)2), is mainly due to genes. The body mass index may reflect both fat and fat-free body mass. In this further analysis of the Danish adoption study, the degree of obesity was assessed by a silhouette score. There was a significant relationship in scores between the adult adoptees and their biological mothers and between the adoptees and their biological full siblings reared by the biological parents. Weaker, nonsignificant associations were found for the biological fathers and for the maternal and paternal half-siblings. There were no relationships in silhouette scoring between adoptees and adoptive parents. The results confirm the results of our previous analysis of body mass index. We conclude that human obesity is under genetic control, whereas the childhood family environment has little, if any, influence on obesity in adults. It is an important task for future research to identify the genes involved.