How Accurate Is The Body Mass Index Scale?

How Accurate Is The Body Mass Index Scale?

The body mass index scale is a simple and easy tool to estimate whether you are underweight, in a healthy range, overweight, or obese. However, because it does not take into account any factors other than your height and weight, it is not extremely accurate for all people. Nonetheless, it is quite successful in identifying people with high risk factors for obesity-related diseases and conditions, and for that reason it is commonly used by doctors.

BMI is an inexpensive and easy to use formula that can very quickly determine if someone is at risk for diseases related to being underweight or overweight. The equation, developed in the 1800s and popularized in the 1950s and 1960s, has long been effective in gathering statistical information about obesity, determining health insurance premiums, and identifying individuals at risk for certain weight-related diseases.

How is the Test Administered?

The BMI test is a mathematical equation that compares a person's weight to their height. It does not measure body fat percentages, but rather estimates what a healthy weight is based on how tall you are. Because it is so easy to calculate, it is widely used throughout the world to determine weight problems. To calculate BMI, you complete the following equation:

BMI = weight (pounds) x 703

Height2 (inches2)

How Do You Read the Results?

There are four major categories associated with the results. For underweight people, their BMI would be below 18.5. A normal range of weight is between 18.5 and 25. Anything over 25 is considered overweight, with a number over 30 signifying obesity.

How Accurate are These Results?

The accuracy of the different categorizations of weight under the BMI formula has long been debated by doctors and scientists. It does not take into account several factors that may affect categorization, including:

  • Gender
  • Age
  • Ethnicity

Because ethnicity is not accounted for in the equation, different countries have determined different thresholds for what is considered obese, as a South Asian is considered obese at a much lower level than that of an American - 23 compared to 26.

These numbers are not meant to diagnose any medical conditions, but to help identify those individuals who are potentially at risk for health problems. To effectively use this tool, you must take into account other issues that can relate to the results such as frame size and muscularity, as many users of this system may fall into the overweight category when they are indeed at a healthy weight.

If you are concerned about your results, contact your doctor to further discuss if you are within a healthy weight range. There are other tests that can be done to determine your body's fat percentage along with discussing your lifestyle and diet with your doctor to determine if there are any improvements to be made to lower your BMI.

1 Comment

  1. Lucy

    The BMI is a flawed tool and should be discarded. It is too general and fails to take crucial information into account, such as age and muscle mass vs fat. It’s misleading and simplistic. As far as I’m concerned, it is of no value. Stop pushing it.

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