With a baby comes a belly - but it turns out that's not just true of women, new research published in the American Journal of Men's Health has suggested.
On average, new fathers gain between 3.5 pounds and 4.5 pounds in the immediate aftermath of having children, even if they don't actually live with or deal directly with the child.
The US researchers who identified the trend dubbed it the “fatherhood effect”, and put it down to a shift in priorities.
"You have new responsibilities when you have your kids and may not have time to take care of yourself the way you once did in terms of exercise," explained lead researcher Dr Craig Garfield.
On top of that, there tends to be a sudden increase in irresistible treats lying around, like ice cream and biscuits.
"We all know dads who clean their kids' plates after every meal," said Garfield, who admitted his own weakness was scraping the leftover cheese from his children's pizzas.
The findings came from an analysis of weight changes among 10,000 men at four different points in their lives: early adolescence, later adolescence, mid-20s and early 30s. Each man was categorised either as a non-father, resident father or non-resident father.
Weight gain followed fatherhood for men of all ages, even when race, education, income, marriage status and activity level were taken into account. Non-fathers, meanwhile, actually lost an average of 1.4 pounds during the equivalent time.
But while watching their weight may take a back seat as men get to grips with fatherhood, Garfield warned that if left unchecked for too long it could damage men's health, and that they should remember to look after their own health as well as their children's.
Fatherhood can affect the health of young men, above the already known effect of marriage. The more weight the fathers gain and the higher their BMI, the greater risk they have for developing heart disease as well as diabetes and cancer.