i went to school with a girl who went from 16stone to 9stone in just over a year age 14ish, i know she has a lot of loose skin because of it however dont speak to her now so not sure whats happened, she did a lot of exercise to try and get rid of it but i think if you loose too quickly then your skin doesnt get a chance to suck in. exercise and water are meant to help but it just goes to show you should loose weight healthily and gradulaly.