Experts are starting to agree that body mass index (BMI), which determines a person’s risk of weight-related health problems, might not be the best method. A new study, published in the journal PLoS ONE, provides new evidence that another method, which takes into account body shape, might be more accurate.

Measuring for BMI has been the most common and convenient way to measure body fat for a long time now. But because it measures body fat through a calculation of height and weight, it doesn’t account for where the weight is concentrated. Athletes, for example, could weigh more from muscle mass and their BMI would be higher because of it. Dr. Nir Krakauer, an assistant professor of civil engineering at the City University of New York’s Grove School of Engineering knew this. He developed a new index, called a body shape index (ABSI), which he found predicted mortality better in a 2012 study.

ABSI also uses height and weight to measure body fat, but along with those two factors, it takes into account waist circumference. It’s well known that there’s brown and white fat in the body. Brown fat is the “good,” and helps insulate the body. But as we age, it turns into white fat, which stores energy and can lead to obesity — white fat tends to reside in the abdomen. Therefore, by measuring waist circumference, too, ABSI is able to account for a person’s body shape.

Krakauer also co-authored the current study, which is a follow-up to the 2012 one. It looked at data from 7,011 adults over 18 years old who had participated in Great Britain’s first Health and Lifestyle Survey during the mid-1980s and then a follow-up survey seven years later. Then, in 2009, they checked data on those surveyed through the National Health Service, looking for death and cancer rates. In all, they found that 2,203 people from the sample had died. When they compared these deaths to the ABSI data taken from the surveys, they found that risk factors for death increased by 1.13 for each standard deviation increase — variation from the average — in ABSI, according to a press release.

The findings are important because they align with the findings from the 2012 study, which looked at the same thing, but among American adults. ABSI was better at predicting death than both BMI and waist-to-height ratio, another body fat measurement that associates expanded waists with lower life expectancies. But despite the findings, the researchers concluded that they need to conduct more tests in order to ensure that adding a waist circumference measure is accurate — some people who change their lifestyles can lose their waists without losing the pounds, they said.

 

Source: Krakauer N, Krakauer J. Dynamic Association of Mortality Hazard with Body Shape. PLoS ONE. 2014.