Waist-to-Height Ratio Beats BMI for Finding Obesity, Study Says

Calculating waist-to-height ratio offers a more accurate picture of a person’s risk of obesity than body mass index (BMI), according to a new study from the United Kingdom.

The study, published in the journal PLoS ONE, seeks to cover a more complete picture of obesity by examining whole-body fat percentage and visceral adipose tissue, or VAT mass, which is the fat stored in the adomen. Recent evidence has shown that excess fat stored in this area raises greater cardiovascular risk than fat stored in other areas of the body.

Michelle Swainson, PhD, and her co-authors collected measurements from 40 women and 41 men using a total body dual energy X-ray absorptiometry (DXA) scanner, which offers a more accurate way to gather information on body composition and fat. From there, they calculated 5 predictors of whole-body fat and VAT, each of which could be done in minutes in a physician’s office to gauge obesity.

They found that 36.5% more adults could be classified as obese using the whole body data rather than the BMI measurements. The other predictors they tested were waist circumference, waist-to-hip, waist-to-height, and waist-to-height^0.5. Waist-to-height was the most accurate. The calculation measures waist circumference divided by height, using cut points of 0.53 for men and 0.54 for women for whole body obesity, and 0.59 for abdominal obesity in both genders.

BMI has been used for years as a screening tool for obesity, but it has its critics—notably that many people who are not unhealthy are classified as obese, and many who have unhealthy levels of visceral fat are missed. In fact, many guidelines based on BMI now adjust downward the benchmarks for overweight in Asian populations.

The waist-to-hip ratio has been recommended by some, but it has been found to be a poor predictor of fitness.

“Our waist-to-height cut points align broadly to current guidelines that adults and children should keep their waist circumference to less than half their height,” Swainson said in a statement. She said the study showed that this measure is more accurate and very efficient and simple for physicians to use in primary care practices, since DXA scans are not available.

“Even in a small sample of adults, our results provide further evidence that alternative measures are fundamental to the more accurate identification of obesity, therefore ensuring that individuals are referred to the most suitable therapeutic approach to reduce risk of obesity-related conditions,” she said.