The Broken BMI

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As we are all well aware, BMI or body mass index is one of the foundations of health care around the world. BMI is a mathematical formula that divides a person’s weight by the square of their height to arrive at a number that falls into various bodyweight categories. This number, in turn, is used to determine someone’s risk for certain diseases, their insurance premiums, and even whether or not someone qualifies for certain medical procedures.

However, BMI was never intended to measure an individual’s health. It was developed in the early 1800’s with the actual term coined in 1972, to study weight variations across populations. The inventor of BMI, Adolphe Quetelet, was not a doctor; rather, he was an academic whose studies included astronomy, mathematics, statistics, and sociology. BMI was never intended as a measure of individual body fat, build, or health. It was created to measure populations, not individuals, for the purpose of statistics and not health.

According to a study published in the International Journal of Obesity, more than 74,000,000 American adults were miscategorized as “unhealthy” or “healthy” based on their BMI alone. Further, nearly half of people considered overweight and almost 30% of those in the obese category were metabolically healthy, meaning they were found to have normal levels of blood sugar, cholesterol, and blood pressure.

BMI is unable to distinguish between weight that is from fat or muscle. It doesn’t say anything about how the body fat is distributed, as fat that is distributed more around the thighs and hips is not as concerning as that which is concentrated in the abdomen. BMI does not accurately reflect changes that occur with age and is based largely on data from Caucasian European males, not of people from other ethnicities or locales. It also doesn’t include exceptions for women who are pregnant or nursing.

When we rely so heavily on BMI as the sole indicator of health, individualized patient care suffers as does a more holistic, comprehensive approach. BMI is a product of its social context and is being recognized more and more as an ineffective measure of overall health.  While it may be a useful indicator of health risk for some, it is not a good indicator of their health habits. BMI does not tell you what someone eats, how they move their body, the quality of their sleep, or their stress levels — all things that influence health. What’s more, health habits go a long way in protecting you no matter your weight.

The moral of the story? BMI is one among many screening tools and should not be used on its own to assess a person’s health risk.

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