Yep, that's fine for guys, but the last thing most girls want is to say they weigh more then around 120lbs.
Man, this one time I asked this fat girl how much she weighed, and she said she weight 140lbs. I looked at her and was like "in your arm?" She got mad and ate herself to death. True story.
No it's not, but still, you get the idea, why do girls obviously lie about their weight? It's not hard to tell the general weight of a person.
Off topic, but still...