Wow! That is great that you are on day 13! WAY TO GO!!! I know with me the really body urge for hungry goes away after 3 days, but I still want to eat a littl bit afterwards. I think it is because I miss the pysical eating because it takes so much of our time to do so. Breakfst, snacks, lunch, dinner, snacks so forth while watching tv, reading books or just with family members.
I think the urge is harder during the summer because of all the cookouts and stuff.
You are doing well, and everyone's body is different and reacts differently to fast depending on the life style lived.
Good luck with your fast! Keep it up. You are doing great!!