Black folks have long been anti-body mass index (BMI) as a measurement of obesity because many of us too easily weigh in across the too-heavy threshold. Now a new statement from the American Heart Association (AHA) suggests our dismay at the over reliance on the flawed measuring tool does have merit. Waist size, the association says, can also play a crucial role in making an obesity diagnosis.
“BMI doesn’t tell the whole story,” said Goutham Rao, M.D., the statement’s lead author. “One has to look at a broader picture to figure out if an individual is obese and is at high risk for heart disease.”
Relying on BMI, a ratio of weight to height, alone could mean missed obesity diagnoses and treatments that are delayed or never started. Current AHA guidelines state that adults with a BMI of 30 or higher are considered obese and need treatment.
Blacks, Latinos and Asian Americans are at greater risk for heart disease, something BMI by itself doesn’t predict accurately for all races. For example, many Asian Americans are considered metabolically obese and suffer from obesity-related diseases even though their BMIs place them in the normal or overweight range. Conversely, many African-American athletes have BMIs that place them in the obese range (see the NBA’s Russell Westbrook). Most athletes have much more lean muscle mass than the average person, a fact that throws a wrench into the basic assumptions behind the BMI formula.
The new statement calls for adults of all races and ethnicities to have both their waist circumference, which measures visceral fat that wraps around internal organs, and BMI measured each year. Dr. Rao hopes measuring a person’s waist becomes as common as stepping on a scale.
According to the National Heart, Lung, and Blood Institute, women with a waist size greater than 35 inches and men with a waist larger than 40 inches are at higher risk for heart disease and type 2 diabetes. That’s even if their BMI falls into the normal-weight category.
“We need to think beyond BMI and increase awareness of the importance of waist circumference for the public and health-care providers,” said Laura L. Hayman, Ph.D., professor of nursing at the University of Massachusetts Boston, in a commentary about the statement. “One size does not fit all. The same cut[off] points don’t apply equally well to predicting disease in all populations. BMI alone, even with lower thresholds, is useful but not ideal.”
