Why am I so hungry all of a sudden?

stillhere1981

I have been doing MFP for about a month and it's going well so far (although I seem to have stalled this week, but I know weight loss isn't a straight line). The first week or so I was so hungry that I was just angry all the time. That passed and I was OK for about two weeks. This week has been rough though even though my diet hasn't really changed (my diary is open). I bought a FitBit and I have been working out a lot. My clothes are definitely looser/fitting better. I'm just wondering what would change to make me so hungry all of a sudden. Is it the exercise? Even days I don't work out I feel really hungry. I'm not a binger, just a constant snacker, but I was craving a whole pizza yesterday (I didn't have it though).