Quetelet was a Belgian mathematician, astronomer, naturalist and statistician, a pioneer of demographic study and founder of the Royal Observatory of Belgium.
BMI is a measurement that is used to calculate a person's body mass. Also called the Quetelet index after its founder, this index is calculated using weight and height. Initially designed for adults, new growth charts have been developed in recent decades for children aged from 0 to 18 years. It is used as a standard tool for evaluating the risks related to excess weight in adults and has also defined standard categories - underweight, normal, overweight, obese - based on the statistically proven relationship between BMI and mortality.