Dr. Arya Sharma, who holds the opinion that “Health cannot be measured by stepping on a scale,” looked into the history of the body mass index standard of measurement.
Like many other public health conventions, this one began with the military, way back in the mid-1800s. The Belgian mathematician, astronomer, and social statistician Adolphe Quételet published a book about the average measurements of French soldiers. His ideas were very influential, and what was originally called the Quételet index became the Body Mass Index.
For an opposing view, Dr. Sharma references a paper written by Stuart Nicholls of the University of Ottawa. Apparently, there are some problems:
While Nicholls also discusses the misuse of BMI as a (rather poor) surrogate for body fatness, his main argument against the use of BMI rests on the overly simplified usage of BMI-based obesity classifications and the problematic application of population level standards to individuals.
Nicholls points out that it is naïve to treat everyone within category as a homogeneous group, for technical reasons that he explains. More significant are the psychological effects, as people tend to misuse and abuse such classification, which can lead to stereotyping and other undesirable social outcomes. Placing people in arbitrary pigeonholes “may affect whether we wish to associate with the individual or how we do so. “
Oversimplification that ignores complexity can lead to inaccurate conclusions, especially when standards are applied broadly across races, cultures, and nations. Nicholls warns:
Definitions of overweight using the BMI provides only a crude population-level measure, and while valuable for its convenience and simplicity in public health surveillance, screening, and similar purposes it lacks the sensitivity or specificity to be used as a diagnostic tool.
Like the Social Security number, which used to exist for one purpose only, BMI has suffered from mission creep and, according to Dr. Sharma, “found its way into clinical, bureaucratic and regulatory guidelines for which it was never intended.” He suspects that classifying people by BMI alone leads to the over- or under-treatment of large numbers of patients. He prefers the more nuanced Edmonton Obesity Staging System (EOSS).
For MedScape.com, Nancy A. Melville acknowledges that BMI and waist circumference (WC) are the most popular methods…
But BMI fails to directly distinguish between fat and lean tissue, and neither measurement reflects underlying obesity-related functional status or health conditions, which can include diabetes, hypertension, dyslipidemia, osteoarthritis, liver disease or kidney disease, or metabolic syndrome.
For one thing, any obesity classification system really needs to distinguish between lean tissue and fat. EOSS also takes into account a person’s basic health status (including any underlying conditions) and is said to be more useful, especially as a calibrator of cardiometabolic risk and predictor of mortality.
The EOSS tool ranks obese and overweight people according to a five-point scale based on factors relating to an individual’s underlying health status (as revealed by blood pressure and serum lipid and fasting glucose test results, among other indicators). Taking into account not just weight but the presence or absence of underlying health conditions is said to make EOSS a better predictor of mortality.
Of the five points on the scale, 0 is the best possible score, meaning no apparent risk factors. Obviously, 5 is the worst and includes “severe (potentially end-stage) disabilities from obesity-related chronic diseases, severe disabling psychopathology, severe functional limitations and/or severe impairment of well-being.”
Your responses and feedback are welcome!
Source: “How BMI Obfuscates Public Health and Clinical Approaches to Obesity,” DrSharma.ca, undated
Source: “Obesity Ranking System Predicts Mortality,” MedScape.com, 08/15/11
Image by Barney Moss