New Obesity Index Proposed, But Further Work Needed

[Guest guest]

US researchers have developed a new index of adiposity that they say is a

more accurate measure of body fat than the traditionally used body-mass

index (BMI); the latter is calculated by dividing weight by height [1].

Using measurements of hip circumference and height, the new body adiposity

index (BAI) can be used to reflect percentage of body fat for adult men and

women of differing ethnicities, without numerical correction or assessment

of weight, say *Dr N Bergman* (University of Southern California,

Los Angeles) and colleagues in their paper published online March 3, 2011 in

*Obesity*.

However, they note that further work will be needed to extend and confirm

their findings--tested in Mexican Americans and African Americans--to whites

and other ethnic groups and to assess the role of the new index in children.

And " 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. "

*Height and Hip Size Most Strongly Relate to Percentage Adiposity *

" We were interested in determining whether we could find an index of body

adiposity that at least in some ways may be better than the BMI, which has

been around since the 1840s " and is not a very accurate measure of adiposity

in individual patients, Bergman explained to* heartwire *. BMI is

particularly inaccurate in people with elevated lean body mass, such as

athletes, and in children, and it cannot be generalized among different

ethnic groups, he and his colleagues note.

Bergman et al are not the first to propose an alternative to BMI. Waist

circumference is widely thought to be a better indicator of cardiovascular

risk than BMI, although some studies have shown them to be equally

predictive. Other examples include the waist-to-hip ratio (WHR) and the

waist-to-hip-to-height index, which have both been forwarded as potentially

better measures of obesity than BMI. But critics have said that it is

difficult and time-consuming to get very accurate measurements of waist and

hip circumference and height and that BMI has remained popular because it is

simple and fast.

In their study, Bergman and colleagues used a large database, *BetaGene*,

which consisted of relatives of Mexican Americans with gestational diabetes,

to determine whether there might be a better index. They chose the Mexican

American population because of its prevalence in Los Angeles, observing,

" Most of the world population is nonwhite. "

" We looked at which variables most strongly related to percent adiposity,

and they were height and hip size. Because these variables were

uncorrelated, we proposed a new index, the BAI, based upon these measures

alone, " Bergman explains.

*BAI Will Be Easy to Calculate*

" We showed that the BAI, calculated as (hip circumference/height1.5)–18, was

a good predictor of percent fat and worked for men and women, " he

continues. The BAI also yielded the percentage of fat itself, rather than

just a correlate (or index) of it, which is what the BMI does, he notes. The

BAI was validated against the " gold standard " of dual-energy X-ray

absorption (DEXA).

" It will be very easy for a physician or a nurse practitioner to work out

this index for individual patients, using a calculator, a computer program,

or an iPhone app, " Bergman says.

The researchers then went on to corroborate their findings in another

population, the *Triglyceride and Cardiovascular Risk in African

Americans*(TARA) study, and found that the behavior of the BAI was

quite similar

between the blacks in that population and the Hispanics in BetaGene.

" Thus, we believe that we have presented evidence of accuracy at least in

two ethnic populations, and further work on the generalizability of BAI to

other groups is under way, " they state. It will also be important to see

whether the index can reliably forecast percentage of adiposity in children

and predict risk of cardiovascular disease, they note.

medscape.com

--

Ortiz, MS, RD

*The FRUGAL Dietitian* <http://www.thefrugaldietitian.com>

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