Most women gain weight after marriage. However, this may not just be do to having a child.
The New York Times reports on a recent study by Annette Dobson in the American Journal of Preventive Medicine. They find that “[a]fter adjusting for other variables, the 10-year weight gain for an average 140-pound woman was 20 pounds if she had a baby and a partner, 15 if she had a partner but no baby, and only 11 pounds if she was childless with no partner. The number of women with a baby but no partner was too small to draw statistically significant conclusions.”
The study does a good job of documenting the weight gain, but does not fully explain why this is occurring. One of my previous studies looks at just this question. My co-author and I hypothesize that married individuals have less of an incentive to maintain their weight, because they are not in the dating market. In fact, the study finds evidence that women who begin cohabitating with their mate gain less weight than if they had gotten married. Since in both cases the women live with their partner, the weight gain cannot be due to simply moving in with one’s significant other. We find evidence that the probability a couple will separate (based on marital status and other factors), directly affects weight. Women in more stable relationships gain more weight then women in less stable relationships, likely because the women in less stable relationships know they may soon re-enter the dating market.
However, the effect of the “dating market” on weight is only 2.4 kg (about 5 lb). Thus, this effect doesn’t cause one to be obese, but can explain some of the weight gain after marriage. Marriage does have many other salubrious effects, and one should not avoid marriage simply to avoid a minimal weight gain.