Excersise tones up the muscles under the skin but I don't think there is much you can do about excess loose skin. After my pregnancy it took 2 years to get my skin back in order so I think if you are still relatively young you should go back to normal over time. Otherwise it must be girdle or in the last event surgery.
A guy at work has this problem round his midriff and he wears girdles. The doctor said if he had surgery he would only have a 50 50 chance of survival. Don't know how much of that is true and how much the doc is trying to save his budget tho!