May 11, 2012 -- BMI's days as a top way to measure body fat and associated health risks may be numbered.
New research presented at the 19th European Congress on Obesity in Lyon, France, suggests that the better way to know where you stand concerning health risks related to your amount of body fat is your waist-to-height ratio.
BMI, or body mass index, is based on height and weight. It can help determine if a person is underweight, normal weight, overweight, or obese, but it has its limitations. For example, BMI doesn't consider muscle mass, so a very muscular person's BMI might incorrectly indicate obesity. You also need a calculator to determine your BMI. All you typically need is a tape measure to find out your waist-to-height ratio.
Researchers reviewed 31 studies of more than 300,000 men and women. They found that waist-to-height ratio was more accurate than BMI and than waist circumference alone at predicting certain health risks associated with being overweight or obese, such as high blood pressure, diabetes, and heart disease.
In a related report presented at the same conference, researchers from the Cass Business School of City University in London, England, reported that a 30-year-old nonsmoking man would have a reduced life expectancy by as much as 14% if his waist circumference is more than half of his height.
"Keeping your waist circumference to less than half your height can help increase life expectancy for every person in the world," says researcher Margaret Ashwell, PhD, of Ashwell Associates, in Hertfordshire, England.
Calling waist-to-height ratio a "one-size-fits-all approach," Ashwell says that it should replace BMI and waist circumference alone as a way to assess body fat and health risks everywhere.
The findings are music to one expert's ears. Pamela Peeke, MD, MPH, is a WebMD lifestyle expert and the founder of the Peeke Performance Center in Rockville, Md.
"Buh-bye BMI," she says. "I have been saying this forever."
"Take out your tape measure, and really pay attention to your waist and waist-to-height ratio," she says. "This is the way to go, and it puts you in touch with your body." The best way to measure your waist is to place the tape measure at belly button level, she says.
Scott Kahan, MD, MPH, agrees that BMI may be on its way out. He is the director of the National Center for Weight and Wellness in Washington, D.C.
The new study suggests that waist-to-height ratio is better than BMI. "The really good news is that it is real cheap and relatively easy to measure height and waist circumference."
But, he says, more research is needed to show us how to act on this information.