• 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 metres (kg/m²).
• 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 gradings in relation to risk may differ for different populations.
• In recent years, there was a growing debate on whether there are possible needs for developing different BMI cut-off points for different ethnic groups due to the increasing evidence that the associations between BMI, percentage of body fat, and body fat distribution differ across populations and therefore, the health risks increase below the cut-off point of 25 kg/m² that defines overweight in the current WHO classification.

Source:WHO