Body mass index (BMI) is a widely used indicator of obesity, but a new study suggests it may not be the best predictor of whether your weight raises your risk of death.
Researchers at The City College of New York developed a new obesity measurement tool called A Body Shape Index (ABSI) that combines BMI and waist circumference.
Waist circumference is a measure used to determine the amount of belly fat a person has. Abdominal fat has been linked to a number of health conditions, including high cholesterol, insulin resistance and high blood pressure.
The researchers measured ABSI in more than 14,100 American adults who participated in the National Health and Nutrition Examination Survey (NHANES) between 1999 and 2004. They found that a high ABSI, indicative of a large amount of belly fat, significantly increased the risk of premature death. A high BMI also predicted the risk of an early death, but to a lesser degree than ABSI.
"If BMI measures body size or 'bigness', ABSI can be thought of as measuring a component of body shape, or 'roundness,'" Nir Krakauer, an assistant professor of civil engineering and a study co-author, told ABC News via email.
Krakauer said his research suggests that ABSI is a reliable metric, but other studies need to confirm the findings before it can be used clinically.
"I expect that formulating recommendations based on ABSI instead of waist circumference as a health indicator will make them more useful, because ABSI adjusts the waist circumference for height and weight to quantify body shape," he said. "High ABSI may identify people who have unhealthy body shapes despite having weight and waist circumference within the normal range, and such people may benefit from diet and lifestyle changes."
Nutrition experts not involved in the ABSI research said this new tool has a lot of potential because of its inclusion of waist circumference.
"We always knew that BMI didn't indicate body indicate body composition. That was always its weakness," said Keith Ayoob, an associate professor of pediatrics at the Albert Einstein College of Medicine in New York. "Waist circumference, without BMI, ties in pretty well with mortality and predicts hazards."
But regardless of how reliable ABSI may prove to be, BMI is still very useful as an overall measure of body fat.
"We're not moving away from BMI," Ayoob said. "It's a general tool that's very easy to figure out. It's too simple to give up."
The authors wrote that it's too soon to tell whether reducing ABSI could lower mortality risk, but Ayoob said losing belly fat is a good way to start.
"Abdominal fat is linked to numerous health problems, so the key is not just losing weight, but decreasing waist circumference," he said.