The Gender Weight Gap: Sons, Daughters, and Maternal Weight

Although the effect of parents on their children has been the focus of much research on health and families, the influence of children on their parents has not been well studied. In this paper, I examine the effect of the sex composition of children on mothers' physical condition, as proxied by their weight. Using two independent datasets, I find that, many years after the birth of their children, women who have first-born daughters weigh on average 2-6 pounds less than women who have first-born sons. This weight gap emerges around the time that the first-born child is in his or her pre-teen years and is largest during the child's teen years. I find indirect evidence that this gender weight gap is associated with bargaining power shifts and with mothers' appearance-centered behaviors in the presence of daughters, but find no support for the hypothesis that mothers with sons weigh more because sons eat more than daughters and induce mothers to eat more. I also show that it is unlikely that underlying biological factors like a Trivers-Willard effect are significantly biasing these estimates. Although this weight gap may appear small, weight gains of this magnitude may contribute to increased risk of breast cancer. This study is the first to show that children can have real impacts on the physical condition of their parents and points to a novel channel through which policy makers may be able to influence health.