Why do you get fat after getting married？

Bridget Jones, in print and on screen, called them the "Smug Marrieds" - the happy couples that seemed to have it all. But maybe the fictional Jones should have called them the "Plump Marrieds." Because along with offering couples unbridled bliss, marriage can cause them to pack on some extra pounds. That's according to a study in The Journal of Family Issues.

Sociologist Jay Teachman, at Western Washington University, examined data from the National Longitudinal Study of Youth. The data included info about more than 3,000 African Americans over a 20-year period.

Teachman tracked body-mass-index, BMI, a measure of obesity, from adolescence to middle age. And he analyzed the relationship between BMI, marital status and changes in marital status. It turned out that living without a partner usually equated to being thinner and having a lower BMI compared with married people and couples living together. The single folks included the never-marrieds and divorced.

Both men and women gained weight but when it came to race, black women had the most rapid weight gain, followed by white women and then black and white men.

The weight gain was just a few pounds - but even a slightly higher BMI is associated with weight-related health issues.

Several reasons exist for the weight discrepancy between the single and married people. For example, married men and women may be less concerned about their body weight because they're no longer actively seeking a mate. Plus, married people have a regular dining partner, possibly leading to more meals. On the single side, those who are widowed or have gone through a divorce may lose weight due to stress.

So while this news may not be good for the smug marrieds, it may be welcomed by Bridget Jones. The single, and very weight-conscious, Jones may actually have had the easier path to staying thin than her married friends.