After he's gotten your attention with his "winning" personality  This is most of it.  Fat guys are especially guilty of thinking that life works like an RPG.  If you put points into Health and Fitness, you must have taken them out of Intelligence and Personality.  Fat women try to pretend they're hot, fat guys generally know they're fat but think their personality will win you over.  So in his fat-drowned brain, if he can just get his foot in the door he's golden because you'll love him for who he is. In reality, "who he is" is at least as disgusting, if not more, than what he looks like.