About two thirds of all the adults in the United States are overweight and about a third are obese. Many experts believe that the standard measurement to determine obesity, the body mass index, is flawed as it doesn't differentiate between fat and muscle. Researchers from City College of New York have developed a new measure of obesity that beats the BMI in predicting a person's risk of early death.

"One criticism leveled at BMI is that it doesn't distinguish muscle and fat mass, so that it doesn’t tell you if you have too much fat," said Dr. Nir Krakauer, assistant professor of civil engineering in CCNY’s Grove School of Engineering, and co-author of the study.

In other words, if you are a man standing 6 feet tall and follow a healthy diet and in a habit of regular exercise then, although you might weigh as much as your couch potato neighbor who eats all day, you are not obese. This is because you have more muscle than fat in your body. However, BMI reading for you and your neighbor will be the same because muscle weighs more than fat.

Professor Krakauer and his co-author, Jesse Krakauer – a physician who happens to be his father – set out to correct this flaw. To account for this factor, the researchers added another index in the BMI- the body shape. They call their new measurement scale as A Body Shape Index or ABSI, according to a news release. 

They say that as the ABSI increases, the risk of dying from obesity also increases. "We were able to demonstrate that those that have a high ABSI showed high rate of death over a five-year period," said Krakauer.

In the study, researchers analyzed medical records of more than 14,000 people who participated in a national health survey. They found that very high ABSI almost doubled the risk of early death in obese people compared to average risk while a low ABSI predicted a less than average risk.

Though, the new system predicted early death risk in people across gender, age and in some races like Caucasians and Blacks, it could not predict early death risk in people with Mexican ancestry.

Researchers included waist circumference as an indicator of high obesity, larger the waist size, higher the obesity level.

As a civil engineer, Krakauer's interests lie in on how climate change and human activities affect the Earth's water and carbon cycles. He turned his attention to medical data, because analysis in both fields involves extracting patterns from huge data sets. These patterns help test hypotheses about what is going on in a system. 

"My dad had been doing body composition work for a long time, but there was always the problem of a lack of evidence for how useful (body composition) was for quantifying risk. My experience with looking at large data sets helped in evaluating hypotheses," Krakauer said.

The study is published in the journal PLOS ONE.