'Dad Bod' Backed by Science: Men Gain Weight When They Become Fathers

Vince Vaughn is one celebrity known for his "dad bod' physique. Mario Anzuoni/Reuters

It turns out that the "dad bod"—or even the man-inching-toward-middle-age bod—isn't just an entertaining little trend invented by the tabloid industry to describe why celebrity fathers such as Vince Vaughn and Adam Sandler are wearing ill-fitting jeans these days. New research supports the phenomenon that new fathers tend to put on a little weight once a child enters the picture.

According to a new study published this week in the American Journal of Men's Health, men may gain averages of 3.3 or 4.4 pounds beginning in the first year of fatherhood. On the other hand, men who chose to not have children actually lose weight as they go into their 30s. The study involved 10,253 men who had their body mass index measured at four different points in their life: early adolescence, late adolescence, mid-20s and early 30s. Then the researchers examined the trends in their BMIs over the 20-year time period. Study participants were divided into three categories: new fathers who lived with their child, new fathers who lived outside the child's primary residence and men who were childless.

After controlling for a number of factors, such as age, race, class and education level, the researchers found that new fathers who live with their children will gain an average of 4.4 pounds. This adds up to a 2.6 percent rise in BMI. Dads who don't live with their kids are still at risk for putting on a little weight. Those men gained an average of 3.3 pounds, or a 2 percent increase in BMI. Childless men lost an average of 1.4 pounds over the same time period. These estimates are calculated based on a man who is 6 feet tall.

The researchers say the extra weight gain is due to a number of lifestyle changes that occur with fatherhood when time is limited. This includes more sedentary activity, an unused gym membership, getting less sleep, grabbing food on the go and even finishing the leftovers on a child's plate.

Unfortunately, for many men, fatherhood weight gain follows newlywed weight gain (according to one study, that's an indication of being happily married). All of these extra pounds over time increase a man's risk for a number of age-related conditions, including heart disease, diabetes and cancer. The main advice from researchers is simple enough: Stay away from your kid's leftover chicken nuggets, ice cream and pizza.