The old Facebook API provided the user sex/gender as part of the default user data. Apparently the new Graph API does not provide that information, even though the document
As far as I can tell some permissions like user_location simply aren't working at the moment. I can get email permissions and some others but for most of the user_... ones, nope. Yes they are wrong about gender as part of default data and there appears to be no permission for it either. So use the old api until the kinks in the new one get worked out.