Too many new devotees get lost in worrying about total fasting, etc. If we are thinking about how hungry we are, then the goal of fasting is defeated. The idea is to be more faciliated to think/meditate on Krishna more, chant japa more, read more, etc. But if our consciousness is one of food, or lack of food (same thing really) then its not serving the purpose. If one can fast and NOT think of food, great. If one's mind is drifting too much in the direction of hunger and eating, then eat and go chant, read, serve, etc. (By the way, Prabhupada made it easy for us by making acceptable things like peanuts, tapioca, and other nongrain filling foods.)