Nineteen-year-old Billy Robbins weighs 60 stone and is reported to be the world's heaviest teenager. He has spent the past three years living in a chair as his mother cooks for, cleans and feeds him. But Billy has made the decision to turn his life around in the hope that one day he may be able to move out of his mother's home. Billy realises that after being fed up to 8,000 calories a day, he has to change his diet not only in order to gain his own independence from his mother, but if he is to live into his twenties. The seriousness of his condition is confirmed by Billy's doctor, Dr Nowzaradan, who tells him that the strain on Billy's heart is now critical. He must begin the slow and torturous route to a target weight of just over 14 stone - undergoing a possible seven operations in the process. This astonishing story also revolves around Billy's relationship with his mother and the co-dependency that seems to exist between them.