Body mass index (BMI) is a way to indicate body fat. It is the most commonly used measure for monitoring the prevalence of overweight and obesity at population level. It is also the most commonly used way of estimating whether a person is malnourished or overweigh. BMI calculated by dividing a person’s weight in kilograms (kg) by the square of height in metres (m2). BMI represents body weight in relation to height. It is helpful in monitoring both malnutrition and obesity.
The current WHO, BMI cut-off points are<16 kg/m2 (severe underweight), 16·0–16·9 kg/m2 (moderate underweight), 17·0–18·49 kg/m2 (mild underweight), 18·5–24·9 kg/m2 (normal range), >=25 (overweight), 25–29·9 kg/m2 (pre obese), >= 30 kg/m2 (obesity). 30–39·9 kg/m2 (obese class I), 35–39·9 kg/m2 (obese class II), >= 40 kg/m2 (obese class III).
For many Asian populations, the suggested categories are, less than 18·5 kg/m2 underweight;18·5–23 kg/m2 increasing but acceptable risk;23–27·5 kg/m2 increased risk;and 27·5 kg/m2 or higher high risk.
Persons with higher BMI are more likely to experience obesity-related health problems.
BMI does not directly measures deposition of fat in body, but it does indicate weight status of individual. A low value (16-18.49 kg/m2) indicate under nutrition and higher value (>=25 kg/m2) indicate need for controlling body weight for minimising health risks and development of diseases. It is important to maintain BMI in normal range (18·5–24·9 kg/m2) by adopting healthy diet and lifestyle.