The Flaws Of BMI

The body mass index has been used for years to determine whether a person is overweight or underweight. Doctors and trainers routinely use this standard of body fat measurement. However, there are flaws to the BMI, and some researchers are working hard to design a different method to measure body fat.

What is BMI?

Lambert Adolphe Jacques Quetelet created body mass index (BMI) in the 1830s. Since that time, medical professionals have used the simple formula of dividing a patient’s weight in kilograms by their height in meters squared to get the BMI. A person with a BMI between 18.5 to 25 is considered to be healthy. However, there are some flaws to this standard for measuring body fat.

The Flawed BMI

In the United States, there is a weight and obesity problem. It makes sense for doctors and health professionals to be on the lookout for specific health issues. The National Institutes of Health (NIH) stated that “the higher your BMI, the higher your risk for certain diseases such as heart disease, high blood pressure, type 2 diabetes, gallstones, breathing problems, and certain cancers.” For these reasons, the BMI scale is still essential for many health providers.

One of the main flaws of the BMI is the indirect measure of the fat that doesn’t take into account sex, age, bone structure, or fat distribution. The BMI focuses on two numbers: weight divided by height squared. With the BMI scores, certain groups can have their body fat miscalculated by these measurements.

As more people are placed in the overweight or obese categories, the BMI is coming under attack. BMI does not take into account the difference between fat and muscle, so its prediction for weight-related health issues is not accurate.

One study with 40,000 people reported that 30 percent are in the “normal” BMI range. However, they are unhealthy based on bad cholesterol levels, triglycerides, blood pressure, glucose, and C-reactive protein tests. On the other side, 50 percent of overweight and 29 percent of obese people were healthy based on their medical examinations. This study believes that 74 million people listed as “unhealthy” by the BMI might be healthy in medical terms.

Some Groups Do Not Benefit from BMI

There are certain groups of people who should not use BMI to measure their overall health and body fat. They include the following:


Nursing or pregnant women should find other ways to measure body fat. Women tend to have a higher body fat percentage and weight during this time. This higher body fat is due to supplying nourishment to the infant. Even nonpregnant women should not take read too deeply into the BMI numbers. When compared to men, women will have higher levels of body fat.

Ethnic Groups

If you are Asian and want an accurate body fat measurement, you also might need to find a different measurement than BMI. In general, Asian people have smaller bodies, and BMI is not a good indicator of health risks. Your health issues might increase before you see an uptick in your weight.


Those older than age 65 often have higher BMIs. According to some studies, a BMI lower than 23 is often associated with more health risks. The ideal BMI for the elderly is around 27. A BMI at 27 can help improve fall risk, immunity, and overall functionality.


Athletes’ BMI levels are often not an accurate representation of their actual body fat percentage. Denser bones and lean muscle mass can result in higher weight and BMIs. Lean muscle is beneficial as it can increase metabolism to prevent heart disease and diabetes. While an athlete’s BMI is higher, that is not an indication that they are unhealthy.

There Are Alternatives to Consider

For those determining their health risks, there are other factors to consider, including age, past medical history, gender, blood tests, and family history. Waist circumference is one way to determine future health problems. The National Heart, Lung, and Blood Institute recommends that women should have a waist circumference of less than 35 inches, while men should have a waist less than 40 inches.

The waist-to-height ratio is another important fact. A ratio of more than 0.5 can put those individuals at risk for heart disease and diabetes. The World Health Organization believes that a ratio above 0.85 (women) and 0.9 (men) can put you at a higher risk for heart disease. With all these measurements, they are often a better indicator of health issues down the road.

Body Fat Percentage is Very Important

Body fat percentage can be measured by many different methods, including underwater weighing (hydrostatic), dual-energy X-ray absorptiometry (DXA), and skinfold. If the body fat is located in certain areas, like the abdomen, then the individual typically will have a higher risk of heart disease and type 2 diabetes. Excess weight in this area is known as visceral fat, and it can increase the risk of significant organ and cardiovascular diseases. In some cases, your body fat percentage measurement is a more accurate way to determine your fitness and health levels.

Why Still Use BMI?

Even though there are issues with BMI, it is still the standard for measuring fat in the body. In most cases, the calculations are not wrong. The NIH states that the BMI measurements are correct 80 percent of the time. Secondly, there need to be more scientific studies before alternatives can replace BMI. Another reason that many professionals chose BMI is due to the cost factors. With BMI, you need a scale and tape measure. New methods, like MRIs and underwater weighing, are labor-intensive and costly. Even waist measurements can be error-prone as well.

There are many flaws in BMI calculations. However, it is still used by many professionals to measure your body fat. While it may be flawed, BMI levels are just one factor that you should use to determine the percentage of fat in your body.

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