This happened to me after quitting smoking too! I was always such a skinny guy and now not so much anymore. Lately I've been trying to not eat as much and I'm trying to ignore the groans that my stomach makes until at least noon. I read that this feeling in the stomach is a signal for when your body goes into "Starvation Mode" - and that is when it starts to go after the fat. Fat are reserves of energy that the body puts away for later use when there is no energy coming in.

I don't know if will work but I'm trying.