The stats are disturbing. Based on body mass index (BMI)—the standard measure used to define obesity—72 percent of African-American men and 80 percent of African-American women older than 20 are overweight or obese, according to the Office of Minority Health.

But a recent study says that those findings may be exaggerated. Researchers from the University of Houston and Baylor University in Texas found that BMI may overestimate the obesity problem among African Americans and underestimate it among Asian and Latino women and adults of Indian descent. Why? Because current BMI measurements—a combination of one's height and weight—are solely based on older studies of white adults.

“It doesn't account for other factors that differ between the races and genders,” says Molly Bray, PhD, one of the study's researchers. “For example, black women genetically have larger bones than white and Asian women. The BMI scale does not take that into consideration.”

By using a low-dose X-ray method called DXA—which estimates lean mass, fat mass and bone density—researchers discovered that the BMI formula considers some African-American men and women obese when in reality they aren't.

This is not the first study to attack the BMI's inherent bias. And given BMI limitations, those accusations carry some weight. The primary problem with BMI is that, on average, people of different races carry a different percentage of body fat and may have larger bones and denser muscles. BMI does not account for these factors. The result? People in certain groups may be inaccurately labeled as obese. This includes muscular types who weigh more.

But there are other issues with BMI: Having a higher measurement does not necessarily mean that you are unhealthy, and those with a lower BMI may have a high percentage of body fat.

So why not just use DXA measurements? Bray admits that DXA equipment is more accurate and inclusive—the problem is that it's also very expensive. “Even if your doctor had the equipment in his or her office, your insurance would not cover the cost,” she says.

Until DXA technology becomes affordable to all, however, the important thing is that the BMI standard should be revised so docs can quickly assess obesity risk for people, say Bray and her colleagues. “We just want to stress that there are genetic differences among people that need to be taken into account [when measuring BMI],” Bray says. “But we don't want to give the message that being sedentary and living an unhealthy lifestyle are not dangerous.”

For blacks, the bottom line is that the high rates we suffer from heart disease, diabetes and chronic illness—all related to obesity—cannot be discounted. Although we don't have to be a size 3 to be in good health, we must make it a priority to become active, eat more nutritious foods and improve our health and fitness literacy.