Expectant fathers should expect to punch an extra hole in their belt buckle.
According to a report in the American Journal of Men's Health that studied 10,000 men, a new father can expect to gain an average of 4.4 pounds. At the same time, non-fathers lost 1.4 pounds over the documented span.
The study's lead author, Dr. Craig F. Garfield, found the results surprising and warned new fathers about taking care of themselves as the priorities in their lives changed — staying up late with the baby makes it tough to make that early-morning workout.
"We need to find a way to engage men for their improved health," Garfield told CNN. "By helping a father take care of himself, he ends up role-modeling for his children."
Author Kermyt G. Anderson echoed the sentiment, but didn't find the results surprising. Anderson in 2012 published "Fatherhood: Evolution and Human Paternal Behavior."
"It's common sense in a way," he said. "It's not the biology of fathering a child. It's after you have a baby. Are you living with that kid? Are you getting up in the middle of the night? Are you spending time with the kid instead of going to the gym?"
Not that four pounds means "danger zone," but the study notes that children with an overweight father and even a normal-weight mother are 4.18 times more likely to be obese. To compare, an overweight mother and normal-weight father isn't thought to have much of an effect on childhood obesity.