Body Mass Index (BMI)
Body Mass Index (BMI) is a simple index of weight-for-height that is commonly
used to classify underweight, overweight and obesity in adults. It is defined as
the weight in kilograms divided by the square of the height in meters (kg/m2). For
example, an adult who weighs 70kg and whose height is 1.75m will have a BMI of 22.9.
BMI = 70 kg / (1.75 m2) = 70 / 3.06 = 22.9
Table 1: The International Classification of adult underweight, overweight and obesity
according to BMI
|
Classification
|
BMI(kg/m2)
|
|
|
Principal cut-off points
|
Additional cut-off points
|
|
Underweight
|
<18.50
|
<18.50
|
|
Severe thinness
|
<16.00
|
<16.00
|
|
Moderate thinness
|
16.00 - 16.99
|
16.00 - 16.99
|
|
Mild thinness
|
17.00 - 18.49
|
17.00 - 18.49
|
|
Normal range
|
18.50 - 24.99
|
18.50 - 22.99
23.00 - 24.99
|
|
Overweight
|
≥25.00
|
≥25.00
|
|
Pre-obese
|
25.00 - 29.99
|
25.00 - 27.49
27.50 - 29.99
|
|
Obese
|
≥30.00
|
≥30.00
|
|
Obese class I
|
30.00 - 34.99
|
30.00 - 32.49
32.50 - 34.99
|
|
Obese class II
|
35.00 - 39.99
|
35.00 - 37.49
37.50 - 39.99
|
|
Obese class III
|
≥40.00
|
≥40.00
|
Source: Adapted from WHO, 1995, WHO, 2000 and WHO 2004.
Note: BMI values are age-independent and the same for both sexes. However,
BMI may not correspond to the same degree of fatness in different populations due,
in part, to different body proportions. The health risks associated with increasing
BMI are continuous and the interpretation of BMI grading in relation to risk may
differ for different populations.
|