Middle-aged Japanese women are resistant to obesity-related metabolic abnormalities.

We attempted to determine sex differences in obesity-related metabolic abnormalities in a relatively large middle-aged Japanese population. The study population consisted of 2935 men and 1622 women who were 35 to 59 years old. Metabolic abnormalities were determined using the Japanese criteria for metabolic syndrome, and we evaluated the number of metabolic abnormalities discriminated by waist circumference. In men, the mean number of metabolic abnormalities increased as the waist circumference increased. In women, although the mean number of metabolic abnormalities increased as the waist circumference increased, the mean number was less than 1 even in those with a waist circumference of at least 95 cm. According to the receiver operating characteristic curve, the cutoff levels yielding the maximal sensitivity plus specificity for predicting the prevalence of one or more obesity-related metabolic abnormalities were 80 cm in men and 73 cm in women. However, the positive predictive value was as low as 28.8% in men and 7.1% in women, which may not be suitable for a screening test, especially in women. Middle-aged Japanese women seem to be resistant to obesity-induced metabolic abnormalities, and waist circumference would not effectively predict the existence of metabolic syndrome. In setting the cutoff points in guidelines, a greater emphasis should be placed on the absolute risk of having abnormalities or diseases.