I think it's a case of you feeling like shit so you treat yourself like shit so you start to look like shit. Either that or you look like shit so you start to feel like shit. According to this study, at least depression has ties to obesity due to "metabolic disturbances involving the hypothalamic–pituitary–adrenocortical axis" Ah there's that keyword - pituitary. "Iz mai hormones fault I be so biiiig"