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Before we start calculating our Body
Mass Index (BMI), let's discuss what BMI is, and what it isn't.
BMI, or the body mass index, is a tool that's used to determine
whether or not a person is at a normal weight for his or her height. It was invented between
1830 and 1850 by mathematician and scientist Adolphe Quetelet. Though it's been almost 200
years since he created the BMI, it's used today almost exactly as he outlined.
While BMI isn't the final word in whether or not someone is at a
normal weight, it's one of the first tools often used to determine if someone's overweight.
Because the BMI doesn't distinguish between weight from fat and weight from muscle (other tools
must be used to determine the actual amount of fat) it doesn't work well for very muscular people
like athletes. But for most of us, BMI is a pretty accurate measure of whether we're
underweight, a normal weight, overweight or obese.
Calculating BMI isn't difficult once you understand the
formula. The basic formula is weight divided by height squared, or kg/m2. You simply take
your height in meters and square it which means you take the number of meters times itself.
Then divide that number into your weight in kilograms. So a person who's five-and-a-half-feet
tall stands about 1.7 meters. To get 1.7 meters squared, you simply multiply 1.7 times 1.7,
which equals 2.89. Now, convert weight to kilograms.
So if someone weigh 200 pounds, that's about 91 kilograms.
To determine the BMI of someone about five-and-a-half-feet tall who weights 200 pounds, or who
stands 1.7 meters tall who weights 91 kilograms, we divide the weight by the height squared, or 91
divided by 2.89. That gives us the result of about 31. This individual is classified as
obese. How do I know that?
A BMI of 18.5 or below indicates an underweight person. The normal
weight range is from 18.5 to 24.9. Overweight people will have a BMI of 25 to 29.9. A BMI of
30 or greater indicates obesity. So a person with a BMI of 31 is in the obese range, but not by
much. By calculating BMI again with different weights, you can see that the person would only
need to lose 5 kilograms, or about 11 pounds, to no longer be obese, but merely overweight.
And a loss of 19 kilograms, or about 42 pounds, will put this person within a normal weight
range. Calculating BMI to determine how much weight one should lose can be a big help for
someone who's not sure.
Calculating BMI can be made even more simple if you're not sure
how to convert to kilograms
Always consult your physician before starting this or any weight loss
program.
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