the BMI index is only a guide and a flawed one at that.
It isn't applicable to muscular people, pregnant women, children, etc.
According to the BMI index, I'm obese, but I don't consider myself to be that much overweight (maybe 5kgs or so) and I exercise regularly without too much bother.
Instead of using the BMI, the "experts" are now suggesting we all use hip-to-waist ratio
Oh well, just another theory to confuse us all and make us feel bad about ourselves!