The Dad Bod And The Weight of Fatherhood Quantified

The Internet has burned this month with commentary about women's alleged new interest in the soft, doughy "dad bod."

If you're like us, you've said: "Are we even sure exactly what kind of bods dads have? Seth Rogen keeps being cited as a 'dad bod' archetype, and he doesn't even have children. I'm really enjoying this national conversation about bods, but I wish it had more quantitative rigor."

Well, your wish has come true. We have figured out exactly how much softer a man's body gets, on average, when he becomes a father. To do this, we zeroed in on men 18 to 45, and compared those who had children who were under 18 and at home with those who did not.

The skinny: On average, dads are 10 pounds heavier than non-dads; they're carrying nearly an extra 2 inches on their waist; and their bellies stick out an extra 1/2 inch.

We know this because the government's Centers for Disease Control and Prevention takes stock of our national beer gut. Every few years the National Health and Nutrition Examination Survey herds about 5,000 men and women into medical trailers to be poked, prodded, measured and weighed. Critically for dad-bod science, health care workers measure the sagittal abdominal diameter by having the subject lie flat on a table so that they can measure how high the navel sits above the table surface to get an objective, scientific assessment of the gut.

The latest data from this survey found that half the non-dads in our 18-to-45 bracket had a sagittal abdominal diameter of less than 8 inches, but only 29 percent of the dads did. But dads seem to wear their extra paunch with some degree of comfort. Despite the extra 10 pounds, nearly as many dads described themselves as being "about the right weight" as those who are not dads. (The exact proportions are 49 percent and 53 percent.)

Call this fatherly self-satisfaction a result of diminished expectations: When asked their ideal weight, dads volunteered a number that was 5 pounds heavier than what non-dads did. And fathers seemed to be making no particular effort to fight the dad bod. They were no more likely than non-dads to say they had tried to lose weight in the last year, with 70 percent saying they hadn't.

We can't definitively say that the dad bod is a consequence, rather than a cause, of fatherhood. After all, if the Internet is right that men with an extra layer of cushioning really are more attractive, perhaps they're more likely to reproduce.

But two interesting pieces of evidence suggest that there is something different about dads' lives that causes the dad bod. Although dads weigh 10 pounds more than non-dads, when those in both groups 27 and older are asked how much they weighed at age 25, the weight difference was much smaller, only 3 pounds.

And the dad bod is barely evident among recent dads - those with only toddlers in the house - while it is much more prominent among those with older children and teens. Over the years, as these men relax into fatherhood, their waistline seems to relax with them.

That relaxation does not seem to be just about getting older. Of the 10-pound difference we found between dads and non-dads, 3 pounds can be attributed to age: In part, dads tend to be a little heavier than non-dads because they tend to be a little older. And married men tend to be heavier than unmarried ones. But even after adjusting for differences in age and marital status, a noticeable difference between dad and non-dad bods persists.

Some in the news media have called the "dad bod" phenomenon a double standard: Nobody's talking approvingly about the "mom bod," even though the same data show approximately equal parenthood gains in weight, waistline and belly size for men and women. Parents of both sexes adjust their expectations in the same way: Moms in our age bracket were 8 pounds heavier than the non-moms, but much like the dads, they adjusted their average desired weight targets up (by 4 pounds). Yet both moms and non-moms are much more likely than dads and non-dads to report that they tried to lose weight in the last year, and on average women report they would like to lose about twice as much weight as men.

The "dad bod" fascination seems to be one of the manifestations of the double standard, and perhaps it's something men across America have already internalized, by deciding it's OK to let themselves go at least a little.

Another finding: The belly gap between dads and non-dads is small compared with the variation among dads and among non-dads. Within the group we examined, 42 percent of dads had smaller paunches than the average non-dad, and 30 percent of non-dads brought more belly to the table than the average dad, at least as measured by the SAD.

So, maybe Seth Rogen isn't such a bad dad-bod model after all. Just as you don't have to go to the beach to get a "beach body," you don't need to have children to have a dad bod, as 30 percent of American non-dads from 18 to 45 already know.