Comment by SCNP

There is an Okinawan principle to eating that says to eat until 80% full. There is a lag between actually being full and your brain realizing you're full. I can't find actual papers about it but if you look up Hara Hachi Bu you can find a ton of pulpy news articles about it.

Edit: I have the same problem. I ate a whole frozen pizza a few days ago and felt like crap for a day afterward. Not just a little personal one either. A full Screamin' Sicilian pepperoni...