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Innovation

Better than BMI? A new way to measure body fat

Using hip circumference and height, scientists introduce a new way to measure percent body fat that can account for different ethnicities. They call it the Body Adiposity Index (BAI).
Written by Janet Fang, Contributor

Scientists introduce a new way to measure percent body fat – called the Body Adiposity Index (BAI) – that can account for different ethnicities.

With obesity as a risk factor for diseases like type 2 diabetes, hypertension, and some cancers, ways to better target fat-loss efforts rely on a better way to measure fat.

Simpler ways like skin-fold thickness (used embarrassingly during my junior high PE class) are notoriously inaccurate. The best way to quantify body fat are underwater weighing and dual-energy X-ray absorption (DXA). Computed tomography (CT) scans and magnetic resonance imaging (MRI) can best assess body fat distribution.

But short of these expensive technologies or inaccurate methods, we only have the more familiar Body Mass Index (BMI), which has been used since the 19th century to measure body fat using weight and height. (Calculate yours.)

But BMI doesn’t reflect ‘true adiposity’ – or the state of being obese (adipose tissue is fatty tissue). Nor can BMI be generalized across genders or ethnic groups.

So Richard Bergman of the University of Southern California and colleagues sought an alternative index, one that measures percent adiposity directly for adult men and women of different ethnicities, without requiring special equations to ‘normalize’ everybody and correct for differences.

They turned to data from "BetaGene," a study on 1,733 Mexican Americans. And just to be sure, they then validated their results using the "TARA" study on 223 African Americans.

The goal was to find traits that most strongly correlated with DXA percent fat measurements (the gold standard). They looked at sex, age, height, weight, BMI, and waist and hip circumferences.

Turns out, hip circumference and height correlated best with percent fat. Specifically,

BAI = [hip circumference (cm)]/[[height (cm)]^1.5]-18

One of the surprising results in this analysis was that percent adiposity could be well estimated without a mechanical or electronic assessment of body weight. Thus, the authors say, even in remote environments where only the simplest and least expensive tools are available (a tape measure), a reliable estimate of adiposity may be obtained.

But what if you have disproportionately small non-child birthing hips? It will be important to examine the application of this method in widely diverse populations, the authors say.

The study was published in Obesity today.

Image: Adipose (or fatty) tissue via wiki

This post was originally published on Smartplanet.com

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