Made that mistake once in high school. So naive. Got it exactly right too, but that's not the point. More experienced me recognizes that anything you say to a woman can and will be held against you in the future.
Nope. Never again. Learned my lesson. Fuuuuuck that noise. I just go with healthy. "How much I weigh Justin?" "........u r very healthy ma'am." End of. Unless of course they're obviously UNhealthy, then I jus let em know. I'm not acquiring blame for ur future health problems.
I would always guess a ridiculously low amount, just to be on the safe side.