I did a clay body wrap a few months ago. According to their measurements, I lost 13.5 inches over the course of the hour. I could hardly tell a difference, though. My clothes didn't feel any different and I think it came back within 24 hours, after I drank some water. The attendant said the inches would definitely come back within 3 days.
Overall, it was a really humiliating experience. Standing there naked while a 20-year-old marks me up with a marker, then measures me, and then after getting wrapped and hanging out in a space suit for an hour, having to do all the measurements again, this time cold and wet. Not exactly the relaxing spa experience I was hoping for.
Mel