Anthropometric Method for Determining “Masked Obesity” in the Young Japanese Female Population

A specific kind of obesity that occurs in young women who appear thin but who have relatively greater percentage of body fat than is normal for their weight is called “masked obesity.” The definition of masked obesity is nutritionally and anthropometrically clear: body mass index (BMI) <25 kg/m2 and percentage of body fat (%BF) ≥30%. However, this definition allowed obesity to be underestimated. Thus, we determined that when mathematically analyzing the relationship between BMI and %BF, the equation %BF=aBMIb could be applied, where a (i.e., %BF/BMIb), converted by logarithmic function, is defined as an index for masked obesity (MOI). The MOI equation (a) was thus %BF/BMI2.12. We measured the height, weight, and %BF of 8,068 young women from all over Japan. The percentage of subjects with masked obesity above the defined criteria (BMI <25 kg/m2 and %BF ≥30%) was 7.4%. The mean MOI was 0.0444 in the masked obesity group and we determined additional cases of masked obesity if the MOI was greater than 0.0444. The percentage of additional masked obesity cases within the standard scale was 10.4%, and thus, the percentage of masked obesity was 17.8% in the young Japanese women tested.