BMI Is Not Racist
The Truth Behind BMI
Background
Body mass index (BMI) is a calculation used to describe relative weight in physical terms across different populations. It is defined as weight (in kilograms) divided by height (in meters) squared.
The phrase body mass index was first coined by Ancel Keys and colleagues but it was originally named the Quetelet index. The Quetelet index was created by Adolphe Quetelet in order to describe average human development. Quetelet was not interested in obesity, the index was developed to describe human growth at different ages. In Quetelet’s book “A Treatise on Man and the development of his aptitudes”, his observations on the relationship between weight and height showed even during periods of development this relationship can be described by his index (BMI). Quetelet’s usage of statistics and measurement to describe human physical characteristics was then expanded to describe other aptitudes such as behavior. He was essentially a founder of the social sciences.
Ancel Keys and colleagues in the 1970s noticed a problem in studying different populations of people; there was no set measurement for relative weight differences between individuals. Different countries, industries, and scientific studies used varying indexes to describe weight and body fat. Using varying indexes made it difficult not only to conduct research but for crafting public health policies, conducting medical examinations, and dealing with insurance policy. Keys and colleagues repeatedly noted the index they were proposing was meant to be used as a population-based metric as there were more accurate measures of individual body fatness.
Usage
Again, BMI was intended to be used as a population-based metric. Ancel Keys and colleagues realized other tools used to describe weight and health were inadequate for various reasons. To compare the relationship of weight between populations there needed to be a standardized measurement, this lead to the use of BMI. Keys validated BMI for use in his Seven Countries Study. Keys and colleagues did this by correlating BMI with other more measures, such as the more accurate skinfold measure. BMI correlated well with this more accurate measure and it also correlates pretty well with other measures.
Keys and colleagues looked primarily at thousands of men from various different countries. Of course, skinfold measures aren’t as precise as other measurements of body fatness, this was noted by Keys. However, it was the best measurement available for that amount of participants. More specialized equipment would cost more and conducting research on thousands of participants would be unattainable.
Criticisms and Defense
As a population-based metric BMI is useful for describing the relationship between weight and health outcomes for a variety of populations. It is relatively easy to use and correlates well with other more accurate measures of body composition.
BMI was originally used on white European men. However, beyond its original usage, the metric has been utilized in various studies with various demographics in numerous countries. Researchers have data from millions of participants from around the world. The link between higher BMI and chronic illnesses like CVD is clear. High BMI in itself is a risk for mortality outside of chronic illness.
The narrative of the inaccuracies of BMI has been already noted by the original researchers who proposed to standardize this index. BMI has numerous applications in the public health literature and has been used on millions of people from various populations. It is safe to say the body mass index is a useful population-based tool for measuring relative weight on a population and public health level.
To state it is inaccurate based on its origin alone is committing the genetic fallacy. Current context matters in these discussions. Even with the early application of BMI being skewed towards white European men, this does not negate its current application, validity, or usage.
Conclusion
