I was watching the Extreme Makeover with the guy that had a complete body lift because of his weight lose and thought I might pass this on to you as well.

Apparently, if you get down to your ideal body weight, your skin will shrink back to fit the body. It may take a little time but the guy was told that if there is excess skin (like the belly flab), it was because he still needed to lose a little more weight to get rid of the excess fat still floating in that area.
In the case of the guy on extreme Makeover, he was impatient and was stuggling with keeping the weight off. Age is also a factor in how quickly the skin comes back.