Loss of Excess Skin During Fast?

Hi all, I am new to this site. I have just started what I plan to be a three to four week water fast. Years ago I lost over 120 lbs. This resulted in loose skin. I had removal surgery, but am still very loose in places. I have heard from some sources that during a Water Fast the body will use the excess skin. Does anyone have an opinion on this?
I also have some excess body fat, probably 40 lbs worth right now, so it won't just be skin my body is drawing from. I am also concerned about muscle loss and if I should be taking any minerals. Please let me know. Thanks!!