If you're a new Dad and don't quite have that fancy Dad-bod yet, no worries, in due time it'll come in. But in the mean-time you may want to consider supplementing with one of these Daddy's Belly Bag. It is pretty much a fanny pack that's made to look like you have a dirty hairy gut sticking out of your shirt. When in reality it's just a handy hip pack that stores your essentials.
To use the bag, just wrap it around your waist, tuck your shirt underneath, and walk around the city and wait for everyone to stare at you, laugh, and most likely take pictures. You'll then be able to feel what it's like to be slightly overweight with a shirt that just doesn't fit over your gut.