My father and his medical colleagues used the now-antiquated height-weight charts to assess patients’ health. I believe that these were compiled from the statistical studies performed for the life insurance industry to view death rates.
For decades, I and others decried the height-weight charts because they ignored body composition as bodyfat—the concerning portion of someone’s weight—was not broken out from the weight.
I slammed the charts as grossly quantitative when a qualitative assessment was required. Any medical student who has excelled in analytical chemistry appreciates this.
My mentor, Ellington Darden, PhD, commonly stated that for a bathroom scale to work qualitatively, it would provide several windows: one for fat, another for bone, another for skin, another for muscle, etc.
Eventually and briefly, skin-fold calipering became a favored fat-assessment tool among a small but growing following. It was the most practical approach, but it left much to be desired as it could only be used to show changes in fat but not the fat values. The fat values required regression equations that were derived from faulty underwater weighing studies and cadaver studies performed with poor controls and expressed with poor statistical significance. Moreover, teaching both medical and paramedical staff to properly use the calipers was formidable.
Enter the BMI
The advent of the Body Mass Index (BMI) temporarily threw me. What’s this? Is it qualitative? Is it really different from the old height-weight charts? Why has the BMI become so instantly pervasive among the medical community? If it is better, why is it better? Was it part of the great technical advances being made in medicine (wink, wink)?
The BMI, like the old height-weight charts, is merely quantitative and provides no better assessment of the patient’s health. As Ellington Darden crudely pointed out, jumping up and down while naked provides a better assessment of bodyfat, as anything that moves around that should not be moving around is fat.
The BMI is better for the medical community as it provides a single number—an index—to concisely record into the patient’s chart. And this only indirectly and slightly and questionably helps the patient. Perhaps it merely confuses the patient.
I struggle to grasp how BMI has helped me over my focus on my bodyweight.
The CPI Compared to the BMI
As I have been hammering, the Consumer Price Index (CPI) is merely an index of the price changes of several cherry-picked commodities. And like the BMI, it is grossly quantitative, providing no qualitative breakout of the individual economic forces that affect it. It is a proverbial bathroom scale that does not provide multiple windows for inflation, scarcities, gluts, taxes, etc.
In a sense, both indexes obscure, deliberately or ignorantly, the valuable information that is crucially needed to meaningfully appraise their related situations. And let’s not overlook that index is the perfect word to instill confusion with everyone.
During the past 40 years, I have not heard anyone use the BMI to express the degree of someone’s fatness, but daily, I hear and see many statements by many people erroneously using the CPI as a measurement of inflation.
Well done Ken ... Thanks! 💪