Is "BMI" B.S.?

A few weeks ago my 5 year old had his kindergarten physical.  He was so excited to find out how much he had grown since his last visit, I tried to distract him with magazines when the nurse tried to tell me his “BMI” put him right at the edge of being at an unhealthy weight.  I didn’t want him to hear her say he is borderline “fat” when he was so excited about his growth.

For those not familiar with the BMI indicator, it is a way to determine a person’s body fat based on his weight and height.   It has been a measurement under scrutiny for years and is still so widely used as a measurement tool because it is so easy to calculate.  But it doesn’t actually measure the percentage of body fat on a person, nor does it take into account a person’s body frame or muscularity. 

Why is it that we continue to accept the BMI as a measurement tool for our children?  Does anyone else agree that since children are still growing it is an inaccurate way to determine their healthy weight? 

When you see a child who clearly looks healthy and well proportioned, how can you say he needs to lose weight?  In my son’s case, he’d look sickly if he lost any weight at all because of his body frame.

I’d expect I’m accurate in saying a professional athlete wouldn’t react well to a higher BMI rating indicating he is overweight, when he most likely has about 3% body fat.  Hence the reason the BMI would never be used on a professional athlete.

What are your thoughts?  How do you determine the appropriate weight for your children?  Do you follow the BMI guidelines or use your own measurement?