The History and Evolution of Body Mass Index

We have heard a lot about BMI– Body Mass Index– for decades now, and many of us have our own personal stories to tell of it: being told ours was too high when we were in sixth grade, with a letter sent home to our parents about having an overweight child and how to “correct” it. Or perhaps more recently, being told to lower your bodyweight to fit into a “normal BMI”. Recent conversations have evolved into how BMI is outdated, inaccurate, and doesn’t consider an athletic person with high muscle mass. Yet, we also know high (and low) BMI seems to be associated with increased risk for mortality and other metabolic conditions such as Type II Diabetes and cardiovascular disease. So, what is the truth?

The history of using Body Mass Index, kilograms of weight per meter of height squared (kg/m2) was a way to measure the ratio between height and weight. Originally called the Quetelet Index, it was created in the 1830s by Adolphe Quetelet, a Belgian mathematician and statistician. Originally, Quetelet was on the search for the “ideal human form” - thus, he took thousands of data points of men’s height and weight across Europe to find this “socially ideal” human body. To give you even more of the ick, this idea of the perfect man’s body was then expanded upon later by Francis Galton in the development of eugenics (Heiberg, 2006¹). Despite this, it had begun to be adopted by life insurance companies to evaluate mortality risk in the early 20th century and was renamed Body Mass Index in 1972. 

The Medico-Actuarial Mortality Investigations of 1912 was a five-volume statistical study published by the Actuarial Society of America and the Association of Life Insurance Medical Directors². This composition of population statistics, including using the Quetelet’s Index, was a way for life insurance companies to standardize their evaluation of mortality risk for insurance applications. It was one of the first publications of its kind and put together anthropometric measurements of its population (height, weight, blood pressure) alongside death statistics. This is important because BMI was a population statistical analysis tool that looked at averages, not individualized health risk.

Ancel Keys, who first published the term Body Mass Index in the Journal of Chronic Diseases in 1972, again emphasized that BMI can be used appropriately in population-based studies, but not for individual analysis. From his original paper, he states: “In much of the literature, especially in discussions of clinical problems and in reports from the life insurance industry, relative weight is taken as a measure of obesity or fatness in spite of repeated demonstrations and warnings of the serious errors arising from that confusion.” (Keys, 1972³). He then goes on to suggest body density (body fat percentage or body composition), subcutaneous fat, and waist circumference were better indicators to use– but they were costly compared to BMI.

Times have changed–not only are we living much different lifestyles, and in much different bodies (unlike our malnourished soldiers from the 1800s BMI is based upon), but we also have a much deeper understanding of weight, lifestyle, and mortality risk. Much more of the discourse is about promoting healthy behaviors, rather than hyperfixating on body weight or using BMI as an accurate assessment of an individual’s current or future health status (Behr, 2022⁴). We should remember the history of Body Mass Index, what it is used for (statistical analysis), and why it has been adopted so much more than body composition would be (it’s cheaper). Remember the population used to determine these numbers, and how their bodies and possible malnutrition should not necessarily be something to strive for.

In a bad game of Telephone, the nuance from these original publishing's has been lost and instead we are intensely focused as a society on scale weight as the best indicator of health (and even worthiness and social status). Even the authors warned us of this confusion. So, I wanted to encourage you to continue being active, lifting weights, eating lots of fruits, vegetables, whole grains, unsaturated fats, fish, and lean proteins–and focus on increasing muscle mass, bone density and healthy habits, rather than simply losing pounds on the scale.

- Coach Kayla

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References

1. Heiberg A (2006-11-04). "Notes on the History of Normality – Reflections on the Work of Quetelet and Galton". Scandinavian Journal of Disability Research. (4): 232–246. doi:10.1080/15017410600608491

2. Association of Life Insurance Medical Directors of America, & Actuarial Society of America (Compilers). (1912–1914). Medico-actuarial mortality investigation (Vol. 1). Association of Life Insurance Medical Directors of America; Actuarial Society of America. http://resource.nlm.nih.gov/01930190R

3. Keys, A., Fidanza, F., Karvonen, M. J., Kimura, N., & Taylor, H. L. (1972). Indices of relative weight and obesity. Journal of Chronic Diseases, 25(6), 329–343. https://doi.org/10.1016/0021-9681(72)90027-6

4. Behr, H., Earl, S., Ho, A. S., Lee, J., Mitchell, E. S., McCallum, M., May, C. N., & Michaelides, A. (2022). Changes in Health-Promoting Behaviors and Their Association with Weight Loss, Retention, and Engagement on a Digital Program: Prospective Study. Nutrients, 14(22), 4812. https://doi.org/10.3390/nu14224812