Quetelet’s statistical researches on the development of the physical and intellectual qualities of man, and an exposition of his concept of the “average man”, which became the by-word of quantitative studies. "Quételet suggested that the ratio of the subject’s weight divided by the square of the height could be used as a measure of fatness that corrected for differences in height. This unit, the Body Mass Index (BMI), is still known as the ‘Quételet Index’ (QI) in some European countries; BMI has been shown to correlate with body fat content, and to predict risk for several of the comorbidities of obesity" (Bray, History of Obesity, IN: Obesity: Science to Practice Edited by Gareth Williams and Gema Frühbeck [2009]). English translation as A treatise on man and the development of his faculties (Edinburgh: William and Robert Chambers, 1842). Digital facsimile of the 1835 edition from the Internet Archive at this link, of the English translation at this link. See No. 171.

In his classification of various populations, Quetelet adopted the plan of determining the standard or typical “mean man” as a basis, using stature, weight, or complexion, etc., as a measure in each particular race or population.