Now that I think about it I guess I'm asking myself the wrong question. I guess what I should be asking is how much water can the human body hold - what's in your stomach?
How much water can your other tissues hold that won't be readily urinated? That would answer my question I guess. Why I would be retaining so much water I have no idea because this is never happened before but maybe it was because of the 5-day fast.
I do not professionally fight but I do train and I m around guys all the time that are cutting weight for fights and some guys cut 15 to 20 pounds. Half to three fourths of that is going to be water so if people are cutting that much water I guess the human body could hold 20 lbs of water or more because if not they would be dying right there in the gym from losing all of their water