I fast a few time a year. Yes - you'll drop a few pounds.
How long will you be fasting for? I usually go 5 or 6 days on juice/herbal teas and day 2 is always the hardest. I usually come down with a roaring headache by the second afternoon. Once I'm past that it's pretty easy and a few times I've hit day 6 and thought "I could keep going". Don't try and lift while you're fasting but go for a walk each day.
What makes a huge difference for me is how I start and how I finish. If I can eat meat free the 2 days prior to starting and 2-3 days afterwards, I usually feel a lot better. First time I fasted I think I tried to eat a steak on the second day it was over and I felt terrible.
Start slowly, finish slowly. You'll be amazed how much time you normally spend messing about with food.