A body mass index (BMI) is a value derived from the mass (weight) and height of an individual. The formula is weight in kilograms divided by the square of height in meters. A high BMI can be an indicator of high body fatness. The concept of the BMI was originally established in the 1830s when Belgian astronomer and mathematician Lambert Qutelet developed the Quetelet index as his theory of “the social physique”.
BMI can be used as a screening tool for weight-related health problems such as obesity, heart disease, stroke, type 2 diabetes, and some types of cancer. The interpretation of BMI values varies according to age and sex. For instance, a person who is 25 years old with a BMI of 25 is considered overweight, whereas a person who is 65 years old with a BMI of 25 is considered normal weight.