BMI tests inaccurate

BMI tests inaccurate
The Body Mass Index or BMI is the most trusted means by doctors for measuring body fat in their patients. Yet this once heralded diagnostic tool is now plagued with controversy. What accounts for the increased skepticism and resulting backlash against using the BMI method? BMI calculations are quick and easy. They are also notoriously inaccurate and imprecise. Experts argue there are better methods available to measure body fat and understand a patient’s health.

BMI development
The Body Mass Index began as an experiment by Belgian researcher Adophe Quetelet in 1842. He wanted to determine the ideal male body image and came up with a formula based on taking an individual’s weight and dividing that by height squared. Testing a small sample of Belgian males, Quetelet believed he had found the perfect ideal human form.

But it wasn’t until the early 20th century that this crude formula was plucked out of obscurity and used to test larger portions of the population. Insurance companies wanted a way to prove that overweight policy holders were at greater risk for diabetes or heart disease. Anything beyond the normal range pointed to greater health risks. Premium calculations were based on little more than a constructed trend.

Eventually doctors saw the BMI as the perfect diagnostic tool. It was quick, easy to perform, and the results were readily understood by patients. As a user-friendly diagnostic tool the BMI quickly became the standard means of measuring body fat percentage. In 1998 a set of numbers such as 25 and 30 were introduced making it easier for patients to understand where they fell on the fat scale.

BMI shortcomings
The BMI’s ease is a double-edged sword in that it is greatly inaccurate in getting a proper diagnosis. The data from other tests including measuring skin folds or waist circumference are not much more difficult, but the information is not quite as malleable. Height and weight are measured and calculated in mere seconds and a number is quickly produced. Alternate methods also lack the round numbers the public is so fond of, requiring more lengthy and painstaking explanations about their outcomes.

Experts speak out
But the body mass index could still not provide the complete story of an individual’s health. BMI measurements are consequently imprecise and inaccurate in their findings, as they do not point out the difference between fat weight and muscle weight. According to the charts, the higher the BMI calculation, the more unhealthy the patient. Dr. Kelly Brownell, Director of the Yale Center for Eating and Weight Disorders explains that fit and fat can and do meet. A fat individual who is fit can be far better off than a slim counterpart who is unfit.

Dr. Jonathan C.K. Wells has produced several studies for the International Journal of Obesity to support his criticisms of the BMI. In ‘A Hattori Chart analysis of body mass index in infants and children’ Wells concludes that BMI is a poor choice to determine obesity. Obesity is having more fatty tissue, not just weighing more. Wells argues against relying on those easily readable set points such as 25 and 30 that cannot tell fat from true obesity.

These numbers fall short of explaining the patient’s health, explains Dr. Kathleen M. Zelman. A number can raise false alarm or false hope; a patient may unnecessarily change their diet or believe their body fat is just right. Muscular athletes weigh more because they have more muscle tissue than fat tissue and conversely the elderly little old lady may not have lost weight but will have lost muscle mass. Zelman points out that the BMI ignores a patient’s gender, dietary habits, level of physical activity and family medical history.

Further evaluations should be carried out to get the full story about a person’s body fat measurements. If the athlete and the little old lady end up with the same numbers as per the BMI, how could they be possibly have the same physical fitness? Zelman concedes the BMI is a starting point and nothing more.

Popular with doctors and patients alike, the Body Mass Index enjoys a loyal following among those who want to measure body fat quickly. But its findings are inaccurate and imprecise. Strength and fitness tests, weights measured over time, and personal histories are far better indicators. Health is more than numbers that have little substance behind them.


This article has been featured previously on one of the editor's writing sites, and is the original creation of the BellaOnline Menopause site Editor. It has been presented here for the interest of Menopause site readers.

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