March 4, 2011

New Obesity Scale Better Than BMI

A new way to measure obesity in people without the use of scales has been developed by US scientists.

Called Body Adiposity Index (BAI), the new measure relies on height and hip measurements, and offers a more flexible alternative to body mass index (BMI) -- a ratio of height and weight, the researchers said Thursday.

BMI has been used to measure obesity for the past two centuries, and is widely used by doctors and researchers. But such measurements are not without flaws, Richard Bergman of the University of Southern California, Los Angeles, and colleagues wrote in the journal Obesity.

BMI is calculated by dividing weight in kilograms by height in meters squared. A person who is 5 feet 5 inches tall would be considered overweight at 150 pounds, and obese at 180 pounds.

But those calculations do offer a lot of room for improvement.

For example, women and men with the same BMI might have very different levels of extra fat. BMI numbers cannot be generalized across different ethnic groups or used with athletes, have extra lean body mass.

The researchers came up with the new index using data from a Mexican-American population study. They confirmed the scale's accuracy using an advanced device called a dual-energy X-ray absorption or DEXA scanner. Their findings suggest BAI can be used across many different racial groups.

BAI can be easily calculated with a computer or a calculator by doctors and nurses. But the team says it still needs some fine tuning, and they still need to test it among whites and other ethnic groups, but they believe it has promise as a new weight measuring tool, especially in remote settings with limited resources and no access to reliable scales.

"After further validation, this measure can be proposed as a useful measure of percent fat, which is very easy to obtain. However, it remains to be seen if the BAI is a more useful predictor of health outcome, in both males and females, than other indexes of body adiposity, including the BMI itself," the team wrote.

One in ten adults worldwide are considered to be obese -- more than double the number in 1980. Diseases related to obesity account for nearly 10 percent of US medical spending, nearly $150 billion a year.


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