Thursday, March 10, 2011

Measures of Obesity

There are several measures of obesity. Each  has its own strengths and limitations. The gold standard is dual-energy X-ray absorption (DEXA). Body mass index (BMI) is calculated as mass (kg) per height2 (m2). 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 measures 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. 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. BAI, calculated as (hip circumference/height1.5)–18, is a good predictor of percent fat and works for men and women.  The BAI also yields the percentage of fat itself, rather than just a correlate (or index) of it, which is what the BMI does. Body fat percentage is estimated from three skinfold thicknesses (biceps, triceps, and subscapular).

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