A friend of mine managed to loose humongous amount of weight after he was diagnosed with medical problems. Now, this guy was fat all his life. He used to be live on junk food and called all kinds of names during his school days. But one day when he was diagnosed with several health problems owing to his weight. He resolved to loose weight.
He managed to loose about 50 Kgs. in 10 months. And he is one of fittest persons I know of. He's also working on a book called "Common Sense of loosing weight".
You can read his story [rediff.com].
Check out Rishi's site at: http://www.commonsenseofloosingweight.com/