BMI is a commonly heard abbreviation these days and stands for
Body Mass Index. It has been used in research studies for many
years, but only recently has been used clinically instead of
the old height – weight charts. Both methods are ways to evaluate
someone’s relative weight compared to their height. The advantage
to the BMI measurement is that the numerical value obtained
for individuals of varying weights and heights can be compared
to the same standard values. Although BMI is used as a way
to evaluate total body fat content, it has the same limitations
as the height – weight tables in certain body types. A very
muscular person with very high lean body mass, but low body
fat may erroneously be identified as overweight. Conversely
a person who may have higher body fat than considered healthy,
but has very low lean tissue may be identified as normal or
healthy because the weight relative to height appears normal.
However, in most cases, the BMI gives a fairly accurate estimate
of body composition for the majority of the population.
BMI is calculated using metric measures as:
Weight (kg) ¸Height squared (m2).
BMI can be estimated using pounds and inches
by the following formula:
[Weight (pound) ¸ Height (inches)2]
X 704.5
For example, the BMI of a person weighing
180 pounds with a height of 5’5” (65inches) would be calculated
as:
[180 ¸ (65)2] X 704.5 = 30
A person with a BMI of 30 would be classified
with Class I Obesity according to the table below.
*CLASSIFICATION OF OVERWEIGHT AND
OBESITY BY BMI
|
|
|
Obesity
Class
|
BMI
(kg/m2)
|
|
Underweight
|
|
<
18.5
|
|
Normal
|
|
18.5
– 24.9
|
|
Overweight
|
|
25.0
–29.9
|
|
Obesity
|
I
|
30.0
– 34.9
|
|
|
II
|
35.0
– 39.9
|
|
Extreme Obesity
|
III
|
>40
|
* From the 1998 Clinical Guidelines
on the Identification, Evaluation, and Treatment of Overweight
and Obesity in Adults from the National Heart, Lung, and Blood
Institute of the National Institutes of Health.
|
