Body Mass Index is also known as the Quetelet Index, after the Belgian astronomer, statistician, sociologist and mathematician Lambert Adolphe Jacques Quetelet. It is a very easy and frequently used method to assess obesity, though it is not a direct measure of adiposity. It is c alcula ted by dividing the patient body mass (kg) by the square of his/her height (m). BMI = kg/ m 2 Classification of weight status: BMI (kg/m 2 ) Obesity Class Risk of Disease Underweight < 18.5 Healthy weight 18.5–24.9 Overweight 25.0–29.9 Increased Obesity 30.0–34.9 I High Obesity 35.0–39.9 II Very high Extreme Obesity > 40 III Extremely high Obesity is defined as a BMI varying from 30-39.9 kg/ m 2 . It is further classified into grades I, II and III. Extreme obesity with a BMI of greater than 40 is also called as morbid obesity. As seen on the right side of the table above, being overweight and the various classes of obesity is closely related t