BMI: a useless number

For a long time now BMI has been used to determine if a person is a healthy weight. The cutoffs, as you probably have seen before are as follows:

* Underweight = <18.5
* Normal weight = 18.5-24.9
* Overweight = 25-29.9
* Obesity = BMI of 30 or greater

The truth is that BMI not an accurate assessment of body composition. The equation for BMI is a person's weight divided by his or her height squared. Nowhere in this equation is muscle mass distinguished from fat mass.

To further clarify:
Two people have their BMI assessed and both score 26.5 (Overweight). Person A weighs 185 lbs and is 5'10", but has 30 lbs of fat. Person B also weighs 185 lbs and is 5'10", but only has 9.25 lbs of body fat (5% of total mass, about what elite athletes score) and the rest is lean muscle.

A more accurate assessment of body composition can be found by Hydrodensitometry Weighing (Underwater Weighing), Skin-fold Calipers (Anthropometry), BOD POD (Air Displacement), Bioelectrical Impedance, and a multitude of other ways.