Body mass index (BMI) is a calculated measurement of a person's height and weight for the purpose of classifying individuals as underweight, normal weight, overweight, or obese. BMI is sometimes referred to as the Quetelet Index, named after Lambert [Page 102]Adolphe Jacques Quı´telet (1796–1874), the Belgian sociologist and statistician who developed it. Quı´telet, who wrote a book about the ‘average man,’ was interested in developing a simple method for classifying an individual's weight scaled according to height. His Quetelet Index, which later became the modern BMI measurement, is the most recognized calculation for obesity statistics. The BMI calculation is frequently used by national and international organizations in health policy discussions concerning obesityrelated issues.