Congrats on your decision! Fasting is definately a great way to get a new body, very quickly.
First three days are hard, I felt very lonely (no comfort from food) but the thing that kept me going was the huge amounts of energy that I had simply by not having to digest food. Hopefully you'll get that too depending on how bad your diet used to be. (mine was horrible!! McDonalds EVERY DAY, now that I think about it I want to puke and puke!)