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Body mass index is a clever way of approximating how heavy a person is. It is a way of taking your height and weight and giving you a relative number that is used to show how light or heavy a person is compared to others. This measurement first became popular in the 60's and has since become the standard for approximating weight. Since the 80's it has been the standard measurement of obesity statistics used by many international health organizations. Despite it's popularity, there are some limitations to the BMI that should be mentioned as well.

Doctors and medical personnel often use the body mass index as a quick way of expressing how thin or obese a person is. Instead of saying that a person is 6 feet tall and weighs 180 pounds, a doctor can quickly just say that the person has a BMI of 24.4.

The calculation of your body mass index is simple, but you may need a calculator to do it quickly. The formula for BMI is your weight in kilograms divided by your height in meters, squared. The formula looks like this:

(Height in meters) / (weight in kilograms)2

Normal BMI is between 18.5 and 24. You are considered underweight if the value is below 18.5. You are moderately overweight with a BMI of 25-30. People with a body mass index of over 30 are considered obese and can be at hight risk of obesity related illnesses.

The body mass index does have some limitations. It is not particularly useful for use in children, mostly because their small bodies do not have the same proportions as adults. In addition, this calculation does not tell you what the composition of a persons weight is. For example, a body builder may have the same height and weight as a person who is out of shape, but the body builder will have a high percentage of dense and heavy muscles, artificially raising his BMI.

BMI does not take in to account fat distribution. New studies are showing that other measurements of body parameters may be better indicators of health risk. One of these measurements is waist circumference, which is related to central obesity. Central obesity, which is fat carried around your trunk and internal organs, is being linked to greater risk of health problems than fat carried around your arms and legs.

In general however, body mass index is a reasonable approximation of your level of obesity. Studies have shown a definite increase in health problems for people with a BMI of over 40. If your personal BMI is up in this range, you should look in to ways to loose weight and get yourself in better condition.

Learn more about this author, Erich Rosenberger M.D..
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