Recently, body mass index (BMI), which has been widely considered an effective measure of body fat, has come under scrutiny. According to researchers from Weill-Cornell Medical College in New York, the data produced from BMI measures may grossly underestimate a person’s true fat mass.
The study, published in PloS One (2012; 7 , e33308), focused on dual-energy X-ray absorptiometry (DXA) scans
to determine measures of muscle mass, bone density and fat mass in 9,088 individuals. Researchers classified 64% of those individuals as obese. However, BMI measurements indicated that only 26% were obese. Subjects’ average age was 51.
The scientists determined that to maintain accuracy, a specific BMI cutoff point of 28 for adult males and 24 for adult females should be adhered to when BMI is the sole measure being used. “These new cut-points [increase] diagnostic sensitivity with small losses in specificity,” the authors confirmed.
“Our results demonstrate the prevalence of false-negative BMIs, increased misclassifications in women of advancing age, and the reliability of gender-specific revised BMI cutoffs,” the authors concluded. “BMI underestimates obesity prevalence, especially in women with high leptin levels (>30 nanograms
per milliliter). Clinicians can use leptin-revised levels to enhance the accuracy of BMI estimates of percentage body fat when
DXA is unavailable.”