Why is BMI a better measure than weight alone?
Currently, the body mass index (or BMI) is considered the best available indicator of excess body weight. BMI is calculated by dividing an individual's weight in kilograms by the square of the height in meters.
BMI is used to predict which patients are at the highest risk for weight-related medical problems and identify which patients would benefit most from procedures designed to help them lose weight. People with clinically severe obesity are at a much greater risk of serious health problems and death than those of the same age at ideal body weight.