Moms often complain about baby weight, but being a dad can also impact the waistline.

Researchers at Northwestern University in Illinois collected data from 10,000 men in their 20’s and 30’s, and tracked their body mass index over a 20-year period.

They looked at three groups; fathers living with children, fathers who did not, and men who were not fathers.

Overall, the body mass index of men tended to increases with age, but fatherhood made a difference.

Fathers who lived with their kids experienced the biggest gains — around 4.4 pounds for a six-foot-tall man compared to 3.3 pounds on average for non-resident fathers and 1.4 pounds for men without kids.

The research is in the American Journal of Men’s Health.

(The Associated Press)