How important is being slim, huh? Well, for me, for my own self, I prefer to be on the slimmer side, and so I try to keep an eye on my weight. I sort of have the whole lanky, nerdy thing going on, which seems to work all right for picking up girls.
But how important is it that my significant other be slim? Eh, not very, and I actually prefer a woman with a bit of meat on her. There's something about a girl who's too skinny that just turns me off; I just imagine a skinny woman siting on my dick and her rib cage working as a cheese-greater against it -- not that my dick is long enough to reach the inside of her rib cage, of course, just being silly. lol
So, eh, I don't think that being slim is all that important.