Better than a BMI? New obesity scale proposed Reuters
March 9, 2011
CHICAGO (Reuters) – Scientists have developed a new way to
measure whether a person is too fat without having people step on
The new measure, called the Body Adiposity Index, or BAI, relies
on height and hip measurements, and it is meant to offer a more
flexible alternative to body mass index, or BMI, a ratio of
height and weight, U.S. researchers said on Thursday [March 3,
BMI has been used to measure body fat for the past 200 years, but
it is not without flaws, Richard Bergman of the University of
Southern California, Los Angeles, and colleagues wrote in the
While there are other, more complex ways to measure body fat
beyond simply stepping on a scale, BMI is widely used both by
researchers and doctors.
It is calculated by dividing weight in kilograms by height in
meters squared. A person who is 5 feet 5 inches tall is
classified as overweight at 150 pounds (68 kg) and obese at 180
pounds (82 kg).
But there is a lot of wiggle room in that calculation.
For example, women and men with the same BMI might have very
different levels of extra flab. BMI numbers cannot be generalized
across different ethnic groups or used with athletes, who have
extra lean body mass.
The team made the 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. Tests in a study of African Americans showed similar
findings, suggesting BAI can be used across different racial
BAI is a complex ratio of hip circumference to height that can be
calculated by doctors or nurses with a computer or calculator.
The team says BAI still needs some fine tuning, and they still
need to test it among whites and other ethnic groups, but they
think it has promise as new tool, especially in remote settings
with limited 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
Obesity has become a global epidemic, with more than half a
billion people, or one in 10 adults worldwide, considered to be
obese — more than double the number in 1980. Obesity-related
diseases account for nearly 10 percent of U.S. medical spending,
or an estimated $147 billion a year.