discoveries magazine

Weight and Measures

Man on scale

Ivan Canu

The body mass index (BMI) has long been the standard for determining healthy weight, but the scales may have shifted now that investigators in the Cedars-Sinai Sports Spectacular Diabetes and Obesity Wellness and Research Center have developed a more accurate method.

Called the relative fat mass (RFM) index, the new technique replaces BMI’s division of weight by height with a new calculation that uses only height and waist circumference. This rectifies BMI’s inability to distinguish among lean mass (bone and muscle) and excess fat—as well as its failure to account for the fact that women generally have more body fat than men.

The researchers settled on RFM after comparing more than 300 possible formulas using a database of 12,000 adults who had participated in a health and nutrition survey. Their findings were published in Scientific Reports.

The RFM results corresponded most closely with the accuracy of a high-tech body scan called DXA, widely considered one of the most accurate methods of measuring body tissue, bone, muscle, and fat.

With just a measuring tape, anyone can determine their RFM: Measure your height and then your waist. For the latter, place the tape measure at the top of your hip bone, then reach it around. For men, use the calculation 64 – (20 x height/waist circumference). Future studies are required to determine what RFM ranges are associated with certain disease conditions.