Weight loss depends on your body and how much you "need" to lose. For example, my cousin, 110 pounds (average) fasts for 10 days, loses 5 pounds and gains it right back when she starts eating again. Her weightloss was water only, as she didn't need to lose weight.
I fast 10 days and drop 10 pounds in the first three days (water weight) and then lose a pound per day after. I gain the 10 pounds back, but not the rest.
Here's the key: You WILL gain all the weight back and more IF you break the fast and start eating like you did before the fast. The "and more" is because you've slowed your metabolism down and it takes a while to rev it back up again after thirty days. You MUST break the fast easily AND change your eating habits.
I've seen way too many people complain about gaining the weight back and more, and then admit it was because they went on a food eating rampage afterwards. The weight gain also tends to come back in wierd areas and it's a more cellulite type fat sometimes...