Do people gain weight after marriage?  A paper by Jeffrey and Rick (2002) says yes.  Using data collected from 2528 workers over a 2 year period, the authors estimated the effect of marriage and divorce on weight gain.  They found the following:

Getting married increases BMI by 0.70 for men and 0.96 for women.  For the average American male and female, this translates into a 4.8 pound increase for men and a 5.6 pound increase Read more »