The body mass index (BMI) is a weight problems indicator and an attempt to quantify the amount of tissue mass (muscle, fat, and bone) in an individual Calculated as body mass divided by square of body height (kg/m2) of the individual. Commonly accepted BMI ranges are underweight: under 18.5 kg/m2, normal optimal weight: 18.5 to 25, overweight: 25 to 30, obese: over 30.
BMI provides a simple numeric measure of a person's thickness or thinness, allowing health professionals to discuss weight problems more objectively with their patients. BMI was designed to be used as a simple means of classifying average sedentary (physically inactive) populations, with an average body composition.
People of Asian descent have different associations between BMI, percentage of body fat, and health risks than those of European descent, with a higher risk of type 2 diabetes mellitus and atherosclerotic cardiovascular disease at BMI lower than the WHO cut-off point for overweight, 25 kg/m2, although the cut-off for observed risk varies among different Asian populations.
BMI is used differently for children.