What's with all the fat faced QB's?

Some friends and I were discussing some of our favorite quarterbacks last night. I noticed something... Why are so many of them so chubby headed? A collection of a few who, from the neck up, do not look like pro athletes.

Jay Cutler. Diabetic? No way!
Jamarcus Russell. At least his head is big enough that it detracts from the crooked tie.

Kyle Orton. Boiler Up!

Phillip Rivers. Clearly, he just saw a cupcake.
Ben Roethlisberger. With a head that big, why would you need a helmet? Even when motorcycling?

If double chins are now the requirement for professional athletes, sign me up.