BMI Isn't a Good Indicator of Health Risks

The Body Mass Index (BMI) used around the world to define overweight and obesity isn't a good indicator of weight-related problems, researchers argue.

Body mass index was developed by Belgian scientist Adolphe Quetelet in the 1830s. It is a number calculated according to a person's weight and height. Doctors use BMI to assess whether or not a person has healthy weight.

A person is underweight if BMI is below 18.5, normal if it is 18.5- 24.9, overweight if it is 25.0-29.9 and obese if it is 30.0 and above. According to many experts, the flaw with this tool is that it does not measure the fat - muscle ratio and so isn't helpful in assessing health of athletes who weigh more due to muscles and not fat.

A mathematician from the University of Oxford had recently said that the BMI is flawed because it doesn't account for the fact that some people are taller and so might be carrying extra natural weight.

Many studies are now focusing on "obesity paradox" where being overweight or obese can actually save peoples' lives, especially if they've undergone a recent heart surgery. Previous research has shown that people with high BMI have a higher chance of surviving after treatment for a heart disease.

A newly published report in the journal Science wrote about why BMI is an inaccurate measurement of health.

"Most studies depend on BMI, and we know it's not a very accurate measure,"  Dr. Rexford Ahima, a medical professor at the University of Pennsylvania, in Philadelphia, and co-author of the editorial, told Livescience.

According to Ahima, BMI doesn't indicate the location of fat. Many studies have shown that excess belly fat (the abdominal fat) rather than BMI, increases risk of heart disease and diabetes. Also, BMI doesn't account for race, gender and age- all of which can raise risk of obesity-related complications.

One of the ways to deal with the BMI flaw is to measure the waist. To measure waist, place the tape around the waist, lined up above the top of the hip bone. There are many sites on the internet that use waist circumference along with gender and age to calculate A Body Shape Index, which is a better system to measure health risks, reports Huffington Post.

More accurate tests about levels of fat and associated health risks include MRI and CT scans that show the location of fat. However, these tests are expensive and time-consuming. Measuring the levels of the hormone leptin is another way to estimate fat levels in the body, according to Livescience.

According to estimates by Centers for Disease Control and Prevention, a third of all people living in the U.S are obese. Obesity can raise risk of chronic conditions such as heart disease, diabetes, stroke, arthritis and even some cancers.