Body Mass Index: BMI Calculator
The Body Mass Index (BMI) is the standard, generally accepted way of expressing weight. In deciding if the weight of a person is excessive, insufficient, or normal, it is difficult to just refer to weight alone as the height of the person is equally important.
The BMI is a calculated value achieved by dividing the
weight (kg) by the square of the height (metres). It has the advantage of being a
simple measure to collect, and providing a correlation with the amount of fat in the body in the
majority of people.
Calculating your BMI - Note that I think that BMI can be very
misleading. (see below)
For typical Western population the following are terms describing weight using the BMI as the measure:
| BMI |
Name |
| < 18.5 |
Underweight |
| 18.5 - 25 |
Normal |
| 25 - 30 |
Overweight |
| Above 30 |
Obese |
| Above 35 |
Severely obese |
| Above 40 |
Morbidly obese |
| Above 50 |
Superobese |
When BMI can be Misleading
- In Athletes: The BMI can be misleading in athletes (such a body builders) who have a low body fat percentage, but deliver an excessive BMI as they have a significant increase in muscle mass. As the index is a calculation of weight and height alone, it assumes that the increase is due entirely to body fat.
- In Children: The BMI can be misleading in children, as body fatness changes over the years as they grow, and girls and boys also differ in their body fatness as they mature. In children it is better to express weight as a percentile value, in which it is compared to others at the same age and sex.
- In Ethnic Groups: For some ethnic groups the BMI values need to be modified. For Chinese, Indian and Malaysian people, a BMI greater than 23 is regarded as overweight and a BMI greater than 27.5 is regarded as
obese
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