Study: BMI Linked to Fat Percentage

N E W   Y O R K, Aug. 28 -- First, they told us to weigh ourselves on scales.

Then, fitness experts said we should start calculating our “body mass index,” or a ratio of weight to height, to better measure our chunkiness quotient.

And now, just when you thought you had the math down, some physicians say a new measure, called body fat percentage, is a better indicator of health risks that may be associated with your flab.

Fat Better Than BMI For Health Risk

Shape-Up America, a non-profit organization started by former Surgeon General C. Everett Koop in 1994 to educate the public about healthy weight, is starting a campaign to promote the use of body fat percentage as a new marker for obesity risk. Their campaign coincides with the publication of a research article about the relationship of fat percentage to BMI in the Journal of Clinical Nutrition.

To calculate BMI, you multiply your weight in pounds by 703, then divide that number by your height in inches squared. For a person who weighs 149 pounds and is 5 feet 5 inches tall, his weight calculation, 104,747, divided by his height number, 4,225, gives a BMI of 24.8, a value associated with minimal health risk.

An increased BMI, however, is associated with an increased risk for heart disease, stroke, type-2 diabetes and several cancers, research has shown. In 1998, the World Health Organization and the National Institutes of Health declared BMI as the standard for obesity risk assessment.

But according to Shape Up America and study author Steven B. Heymsfield, deputy director of the Obesity Research Center at New York’s St. Lukes-Roosevelt Hospital, a BMI can misclassify someone’s health risk one out of four times, while fat percentage is a more direct measurement of your risk for disease.

Not All BMIs Are Equal

BMI does not, for example, take into consideration the differences in weight between lean muscle mass and body fat. Someone can have a high BMI, but his or her fat percentage could be low. Heymsfield says athletes, firefighters and members of the military often fail BMI and are deemed “overfat,” but actually are in excellent health and have a very low percentage of body fat.