Stretch marks?

I was wondering whether stretch marks will definitely appear during water (only water- no juice) fasts that last for more than 20 days. I definitely intend to start a long-term Water Fast soon, but I worry about ending up with stretch marks all over my body. I know that there are products out there that treat stretch marks, but I don't want any more marks! I already have stretch marks on my thighs and calves :\

I think I may already know the answer to my question, though. The rapid weight loss incurred during extended Water Fasts pretty much guarantees that there will be stretch marks, right?