I have tried fasting, one 24hr fast in each of the last 2 weeks, and the results have been awesome!!
I have a friend who is a pro athlete trainer, and extreme health nut, and he recommends fasting to everyone. The nutrient loss in such a short period of time is minimal, especially if you are still taking supplements (quality multi, D, efa's etc) He even works out on days that he is fasting and says there is no difference. He says your body gets used to not having food (fuel) at its disposal, and starts to use what it gets more efficiently.
I am planning on trying some longer ones in the next couple weeks.
The juice you are consuming at the end, is best if its pure vegetable juice, (juice your own) instead of the sugary crap at the store.