I've just turned 14 last month, and because of how narrow-minded a lot of people are at my school, I never say my weight, won't hurt here, though, since I think you can spare a moment for me to explain.
Well, I'm 5'5" but I weigh in at 149 lbs. 14 years old, female. I work out like god knows what, though. My stomach has lean muscle, as do my upperarms (Unflexed: 8" in diameter; Flexed: 11" in diameter) while my stomach only has a diameter of about 25 1/2".
So I frankly think the BMI can be a load of bull in my case.