Body Mass Index (BMI): Is this really a good gauge on health?

Body Mass Index (BMI) is a great way to get a gauge for your overall health, but there are a lot of considerations you must take into account when using this formula:

Step 1:  Calculate height in inches

Step 2:  Calculate BMI, using height in inches in the following equation

BMI = (weight(lbs) / [height (in) x height (in)]) x 704.5

Here is an example:

I am 6' 11"; therefore my height is 71"

BMI = (165 / 71x71) x 704.5 = 23.06

So how do you use this number?  Follow the chart below to determine what this number should tell you:

BMI Standards (International Sports & Sciences Association)
Underweight                         <18.5
Normal                                18.5 - 24.9
Overweight                          25 - 29.9
Obesity, Class I                   30 - 34.9
Obesity, Class II                  35 - 39.9
Extreme Obesity, Class III   >40

Now this is not a perfect system, but a good gauge to use as a starting point.  Here are some things to consider which may throw your BMI way off the charts.  BMI does not take into account physical fitness or bone structure, and it doesn't differentiate between weight gained due to muscle building versus eating out at your favorite fast food restaurant.  If you’re one of those who is building a lot of muscle you may end up with a BMI in the obese range. (For example, at the peak of his bodybuilding career, Arnold Schwarzenegger had a BMI of 33, which is considered obese.)  For those who know me, I am an ultra runner with a body fat percentange of about 6% yet I calculate at the high range of the Normal zone.  So use this calculation as a starting point, but keep in mind some considerations and go from there.  A better method to use is to do a body fat percentage test, estimated healthy weight for your height and body composition, and compare these numbers to your goals.  You can also use your blood pressure as a gauge to how healthy your really are no matter your size.