I have a cousin who used to be a good 450 lbs. at 5-10. He had gastric bypass surgery 4 years ago and he's about 140 now. He's literally skin and bones. He looks horrible, just in the opposite way of before.
Now, the funny thing is that once he lost all the weight he had a problem with his balance for a while. He was literally falling down all the time. He was so fat for so long that he had adapted his walk and simple things like getting into his car to his size. Once he lost all that weight he had to go through an adjustment period. I remember playing a game of basketball at a family gathering for the 4th of July and he was falling down every 10 seconds because he was so used to being fat and didn't know how to run and jump without all that weight. I felt sorry for him, but it was one of the funniest things I've ever seen.