Food = Energy
Energy = Better Workout
In my "bodybuilding" days, this was common practice for many to do an hour on the elipticle on an empty stomach. People passed out, through up and basically had lousy, weak workout sessions. Many quickly got "burned out" and quit.
From my own personal experience, I'd wait at least an hour after eating breakfast to exercise. I've not waited at least an hour, and the entire workout (running), my food was trying to come up and horrible heartburn!
As far as Post Workout nutrition, 3 oz grilled chix, protein bar, protein shake, etc. works fine for me.