BMI Blunder

by: AndreaDow
Total views: 574
Word Count: 493

Thursday, August 2nd

At some point you have probably heard about BMI (Body Mass Index) as a way to determine certain health factors and appropriate body weight. The calculation is very basic- weight (in kg) divided by your height (in meters) squared. The measurement only takes your weight and height into consideration and is NOT the best way to determine if you are overweight. The main problem with this equation is that it does not take into account your body frame or muscle mass. Most professional athletes would be considered overweight/obese because they have substantial muscle mass. Also, if BMI does label you as overweight, you will have no idea where the body fat is located. Knowing the location of fat can help indicate your overall disease risk.

Dr. Oz reports in O magazine about an easy measure to determine your stress level. Simply take a tape measure and wrap it around your waist at your belly button. The measurement around your waist should not be more than half of your height (make sure to measure in inches). According to Oz, by reducing the size of your waist, you can "reduce your risk of heart disease, hypertension, diabetes, high cholesterol, cancer, joint disease, and kidney failure". For an exact number to measure yourself against, women with a measure of 35 or more and men with a measure of 40 or more are considered to be at high risk for diesease. I like this easy measurement and think it is quite effective.

A more refined measurement is the hip-to-waist ratio. Men should have a ratio below .95 (waist size is less than 95% of the width of the hips) and women below 0.80 otherwise, they are considered to be at greater risk.

Most of the gyms use a skinfold caliper that assesses subcutaneous fat at certain points on the body. The error here is plus or minus 3% and that is if you use the same test administrator. The gold standard is still considered underwater weighing. I remember this test from my Kinesiology days at UW-Madison and it was not fun (although very accurate). It costs about $75 and is usually done at research institutions (the equipment is $$$). Lastly I want to mention the Bod Pod. It has the same error range as skinfold testing and costs about $50. This device looks like a mini tanning both pod and uses air displacement to determine your body's composition. Since the Bod Pod gives the same error range as skinfold testing, you may as well stick with the cheaper test.

With all this said, there are errors in all of these tests and measures. I like the least costly methods like skinfold testing and measuring your waist against your height. There is no need to spend your money on the more expensive stuff and do not rely on BMI to determine your health related risks.

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