actually, i read that it has nothing to do with the rest of your body for certain people. my mother was always complaining about having a double chin and wanting plastic surgery, so my brother and i decided to prove her wrong saying all she really needs is a good diet and some excercise, eventually we stumbled upon something that basically said, a double chin is something that certain people can not get rid off and there for need plastic surgery, im not saying this is everyone with a double chin, but i have heard of such cases, and since you sound like someone with a good diet and excercise this may be the case for you, but dont just take my word for it, dont give up!!!