Is BMI As Measure Of Obesity About To Change?
Currently we measure obesity using a formula that gives us a person’s body mass index or BMI. It is derived by taking body weight and dividing it by the square of a person’s height. We use BMI charts regularly in our practice as an opportunity to discuss overweight and obesity in our patients. But there are flaws in using this method of calculating body fat and if Richard Bergman, professor of medicine at the University of Southern California in LA, had his way, we would be using a different method to calculate an individual’s percent of body fat.
The drawbacks to using the current method is that muscle mass weighs more than fat so a muscular person may come up on the charts as obese. In addition, since men have more muscle mass than women, the charts are not always accurate for them. In the elderly, BMI can underestimate body fat because of muscle wasting. BMI is not that useful in estimating body fat across ethnicity and gender. Now granted, in some ways defining obesity is not that difficult – like pornography, you know it when you see it but the question is what parameter can be used to best quantify fat content?
Professor Bergman and his team have come up with an equation based on hip circumference and height that they feel best correlates with percentage of body fat which they called Body Adiposity Index (BAI). The interesting difference in their equation is that weight is not taken into account in the equation.
So far the index has been validated in the African American populations as well as Mexican Americans. It has not been confirmed in Caucasians. Bergman’s results were published in the journal Obesity and you can also read more about BAI at this link.