This dude thinks part of it is due to macrophilia (attraction to giants) and the crush fetish, where people like the sensation of being literally squashed under heavy weight. There's some belief that men who like really fat women are under chronic stress.  Evolutionary biology suggests that when men are stressed out it triggers a primal reaction.  Way back when we battled the saber tooth tiger, biological stress was most commonly linked to lack of food and potential starvation.  Modern psychological stress reminds our monkey brain of physical stresses and an "ample" woman is preferable when one fears starving to death. But all of that is speculation.  Dudes find that attractive because some dudes are broken, that's my theory.