I don't think there are good arguments but that doesn't mean that it doesn't exist - in the same way that there aren't good arguments for racism but that doesn't mean it doesn't exist.

I suspect that psychologically some people associate a slim figure with self-discipline, but even if there's some sort of vague correlation there (and I have no idea how you would measure such a thing), doesn't mean that you should make judgements on it in the same way, that you shouldn't assume a woman isn't good at mathematics just because on average men are better at mathematics than women.