Can water retention mask fat loss?

Normally I am on a diet of 1500 or more calories a day. Now I am juice fasting and it's day number four. I've been taking in lots of veggie juice, which adds up to a total of 390-585 calories a day.

I have lost about four pounds, but I think most of it was probably the stuff in my intestines. I feel really puffy and look just awful. LIke the waking dead. I feel puffy all over! Is this water retention? Might I actually be losing fat and not know it because all the detox is causing water retention?

Just sooooo curious what is going on with me...

Thanks!
Anne