Body Mass Index May Underestimate U.S. Obesity
A New York University School of Medicine study claims that Body Mass Index (BMI), the traditional method used to measure obesity, may underestimate the number of Americans who actually qualify as obese. Nirav Shah and Eric Braverman, “Measuring Adiposity in Patients: The Utility of Body Mass Index (BMI), Percent Body Fat, and Leptin,” PLoS One, April 2, 2012. The researchers used BMI and a test called Dual- Energy X-Ray Absorptiometry (DXA), which provides simultaneous measurements of muscle, bone mass and body fat while measuring levels of leptin, a protein that regulates metabolism, on a cross section of 1,394 patients.
According to the study, 48 percent of the women and 25 percent of the men were misclassified as non-obese based on BMI but were considered obese based on DXA testing. The researchers concluded that people who have lost a lot of muscle mass as they age, many of whom are women, are particularly affected by the discrepancy because BMI does not directly measure body fat, only estimates it. As Braverman told a news source, “BMI is the least accurate test in medicine. It’s been around since 1832 and hasn’t changed. People are being told their BMI is [a healthy] 24, when their body fat is actually at 34 percent, which is obese.” See U.S. News & World Report, April 3, 2012.
