According to the World Health Organization, the Body Mass Index is an index commonly used to classify underweight, overweight and obesity in adults. BMI is obtained by dividing the weight in kilograms by the square of the height in meters (kg/m2). It is a commonly used index to classify overweight and obesity in adults. (1, 2)
This index is age and gender independent. However, it has some limitations, since:
- Different populations present different body proportions and body build. This means that a BMI in one country has distinct health implications when compared with the same BMI in another country;
- It doesn’t consider the varying contributions of bone mass, muscle mass and fluid to body weight;
- The percentage on body fat increases with age and is higher in women.
The BMI has the following cutting points, representing several classifications.
|Underweight||less than 18.50|
|Severe thinness||less than 16.00|
|Moderate thinness||16.00 - 16.99|
|Mild thinness||17.00 - 18.49|
|Normal range||18.50 - 24.99|
|Pre-obese||25.00 - 29.99|
|Obese class I||30.00 - 34.99|
|Obese class II||35.00 - 39.99|
|Obese class III||≥ 40.00|