Pizza is something alot of people love, myself included! So, in order to NOT overdo it...use a fork. Sounds simple. But using a fork forces you to slow down, forces you to digest the food and lets your stomach tell you when it is full!
It takes about 8 minutes for your stomach to get full and let you know. If you eat too fast, you miss that cue and end up with a bloated belly and 5,000 extra calories!