Dilemma's Quetelet Technological Deficiency, Epistemological Apathy, and the Validation of BMI-C (Body Morphometric Index - Corrected) with NHANES 2015-23 Data

Abstract Why is BMI (Body Mass Index) an inefficient index for Primary Health Care?BMI, proposed by Quetelet in the 19th century, persists as an epidemiological andclinical tool despite its well-known limitation: it does not distinguish fat mass from lean mass,ignores tissue heterogeneity, and treats the body as a plane (cm²) when it is a volume (cm³).Criticisms of the method date back to Quetelet himself, who had already observed thevariation in the weight–height relationship throughout development. Ancel Keys, whennaming it Body Mass Index (BMI), acknowledged its limitations for individual assessment butjustified his choice by the technological unavailability of more precise methods on a largescale — the same limitation that existed in 1832. Nick Trefethen proposed a mathematicalrefinement with exponent 2.5, which does not solve the problem of heterogeneous bodycomposition..We present the BMI-C (Body Morphometric Index – Corrected), an index thatincorporates the third dimension of the body. BMI-C achieves a correlation of 0.926 withtrunk fat measured by DEXA — a value close to the gold standard and with predictivecapacity that BMI lacks.The importance of this improvement goes beyond statistical precision. Bodycomposition directly determines oxygen availability and the body's water reserve: adiposetissue, by causing a gradual volumetric restriction of the lungs, reduces ventilatory capacityand, by replacing muscle, decreases water reserve. This dual restriction — ventilatory andmetabolic — impacts fundamental processes such as the Krebs cycle and oxidativephosphorylation, which depend on an adequate aqueous environment for maintaining theproton gradient, mitochondrial integrity, and efficient ATP production. The gradual correctionof BMI, by refining the estimate of the proportion between lean and fat mass, allows a moreaccurate assessment of the body's metabolic efficiency — a dimension that BMI, by itstwo-dimensional nature, is unable to capture.