An anecdotal introduction to dimensional theory is used to focus on the issue of combining samples that differ allometrically with size. None of the ideas are original with the author. Indeed, the principles are well-known. Proponents of the body mass index who propose a common scale for individuals 20 to 65 years old blatantly ignore them. The error of combining samples is demonstrated using log log regressions of weight on one predictor height for men, women, and combined samples of men and women in five-year age increments from age 20 to 65 years. This paper serves as an invitation to examine the assumption of biological constancy illustrated by the so-called body mass index that was never true and now in the microcomputer age is unnecessary.
Allometry; BMI; Conceptual error; Height; Weight; Meredith; Quetelet; Ratios; Tanner; Cross-sectional samples; Men; Women
