Why the BMI is Flawed

Do you dread the part of a doctor’s appointment when you're put on a scale and told to look straight ahead in order to record your height and weight? Then, after a quick calculation you hear the words, “You need to lose some weight, your BMI (Body Mass Index) is too high!”  You can’t believe you’re being chastised since you’ve put so much effort into working out and eating well.  You become so discouraged that you think you’ll go back to your old bad habits, since it's obviously not paying off.

Your BMI should not be the sole indicator of success or failure.  If so, I'd find another doctor. The BMI was introduced in the early 19th century by Lambery Adolphe Jaques Quetelet.  He was a mathematician, not a physician. Quetelet produced the formula to measure the degree of obesity in the general population in order to help the government allocate resources.  His BMI formula used a person's weight in pounds times their height in inches squared, then multiplied it by a conversion factor of 703.  Fast forward to June 1998, where the National Institutes of Health created BMI guidelines in an effort to make sure doctors, researchers, dietitians, and government agencies were all on the same page in regard to classifying obesity.

There are many flaws to the way BMI is calculated.  One being that it doesn't distinguish lean body mass vs. fat weight.  Also, bone is denser than muscle and twice as dense as fat.  Due to this, someone with strong bones, good muscle tone, and low body fat would have a high BMI.  Using the BMI most athletes, bodybuilders, and fitness enthusiasts, would be classified as overweight or even obese.

Taking the BMI into consideration with the older population might even be hazardous.  Generally older people have more body fat than younger people with the same BMI.  Thus, for the older population, the BMI might underestimate body fat resulting in possible health risks as one ages.

Some insurance companies charge higher premiums for people with a high BMI, even though they might be healthier and more fit than someone with a normal BMI.  It is true that a person who is overweight or obese will have a high BMI.  However, a high BMI doesn't necessarily equate to a person being overweight or even obese.

Although the BMI tends to be used because it's a simple, inexpensive method of screening, it should not be the only measurement.  Further assessments like body fat percentage, exercise routine, family history, and nutrition analysis all play an important role in evaluating health risks. Want to know your body fat percentage or how to maximize your exercise routine to decrease your body fat?  Contact Dan at (978) 807-8579 or visit seachangefitness.net.

Dan Kinsella is an Exercise Physiologist with a degree in Sports Medicine.  He's a Certified Strength and Conditioning Specialist (CSCS) through the National Strength and Conditioning Association (NSCA), as well as a Certified Nutrition Specialist.  To learn more about this article, or his personal training services, visit seachangefitness.net or call (978) 807-8579 to schedule your FREE consultation!