I need help

Maybe he is in a depression? I mean, if he feels that he eats normally and has lost an appetite for food...and his parents are sending him to hospitals, maybe there is something wrong with him. The normal way-out from this situation would be if his parents STOPS worrying about him and stops sending him to hospitals. And one morning this guy will wake up and understand that he is so weak and that nobody will take care of him, that he must do it by himself. And problem solved! He will start to eat normally and might become physically stronger. It helped for me. Maybe will help him as well. :)

Your friend probably has very fast metabolism,that is normal and my dad has been skinny all his life with more than healthy appetite. There is nothing wrong with that,most people would consider that a blessing. But if that bothers your friend so much,maybe he should try working out and growing some muscle,that would make him look bulkier and make him popular with girls:)