We read with interest the study by Xu et al. [1]. In their observational study of 7567 Chinese participants, they compare the ability of different indices of obesity (BMI, waist circumference, waist-hip ratio and waist-to-height ratio) to discriminate between individuals with and without previously undiagnosed Type 2 diabetes. The authors conclude that the waist-to-height ratio seems to be the best indicator for undiagnosed Type 2 diabetes. We have three comments on this study-the first is related to the diagnosis of diabetes, the second to potential sex differences and the third to the general assumption of a 'one-size fits all' indicator for Type 2 diabetes. This article is protected by copyright. All rights reserved.