Body Mass Index (BMI)

What is it?  Why do we need it?

It is:  a statistic which measures your body fat based upon your height and your weight only.  The equation is Weight divided by Height.

This Factor is then categorized to determine what is healthy and what is not.  The normal BMI chart displays BMI as a function of Weight (along the horizontal axis) and Height (along the vertical axis).  Using contour lines you can plot your Weight and Height and find your personal BMI.

It does not actually measure you percentage of body fat.  It is only a tool used by physicians and health insurance companies to help them determine your healthiness.  It was developed between 1830 and 1850 by a Belgian Mathematician, Adolphe Quetelet.

The Basic Categories are:

  1. Underweight – BMI < 18.5
  2. Normal – BMI 18.5 to 25
  3. Overweight – BMI 25 to 30
  4. Obese – BMI > 30

A couple of  examples would be:  You are 5′-0″ and weigh 115 pounds.  Your BMI would be 23 (115/5) and you would fall in the “Normal” Range.  Or, if you are 6′-0 and weigh 240 pounds, your BMI would be 40 (240/6) and you would fall into the “Obese” Range.

But what if you are all muscle and have very little body fat?  BMI really does not give you a fair assessment.  You are better served by finding your percentage of body fat by using underwater and skinfold measurements which calculate your Body Volume Index (BVI).

In general, the BMI factors are not looked at as strict measurements of your “fatness” or “thinness”.  They are general at best and must be considered as an aid to determining your health.  Private medical insurance companies use them but modify the levels for overweight and obese.

It is a controversial health index.  Some argue that the error in the BMI is significant and so pervasive that it is not generally useful in evaluation of health. University of Chicago political science professor, Eric Oliver, says “BMI is a convenient but inaccurate measure of weight, forced onto the populace, and should be revised”.

Sources:  World Health Organization web site


About Gary

I am retired, but not tired. I still want to be valuable to others. I know that others are valuable to me. After looking back on six decades, I have asked myself this question: “What do I believe?” My mind filled up. My heart started beating faster. My spirit soared. I post blogs to share what my mind is working on, what my heart believes would help others and, what my spirit is communicating to me. What do I believe, you ask? Decisions dictate your path In love, not hate In tolerance, not prejudice In health, not sickness In wealth, not poverty In kindness, rudeness In happiness, not sadness In encouragement, not discouragement In faith, not doubt In courage, not fear I have been and will be challenged in each one of these beliefs, but the biggest belief is to stay positive and not turn negative. This belief helps me maintain all of the others.

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