Optimal Cut-Offs of Body Mass Index and Waist Circumference to Identify Obesity in Chinese Type 2 Diabetic Patients

PURPOSE: The prevalence of general obesity (commonly defined by body mass index (BMI) in kg/m(2)) and abdominal obesity (commonly assessed by waist circumference (WC)) has increased rapidly in China. The aim of this study was to investigate the diagnostic accuracy of traditional cut-offs for BMI or WC to identify general or abdominal obesity in Chinese type 2 diabetic patients and propose optimal cut-offs. PATIENTS AND METHODS: BMI and WC were obtained from 1539 type 2 diabetic patients. Body fat percentage and visceral fat area measured by dual-energy x-ray absorptiometry were set as the gold standard to identify general and abdominal obesity. We assessed the diagnostic power of traditional cut-offs for BMI and WC to define obesity, and analyzed receive operating characteristic (ROC) curves to obtain the optimal cut-offs to identify obesity in Chinese type 2 diabetic patients. RESULTS: In Chinese type 2 diabetic patients, the optimal BMI was 25 kg/m(2) with the best trade-off between sensitivity and specificity (men: 74.6% (95% CI: 70.7–78.2%) and 65.1% (95% CI: 59.7–70.3%), AUC 0.78 (95% CI: 0.75–0.81), p<0.05; women: 65.8% (95% CI: 60.3–71.0%) and 80.3% (95% CI: 75.7–84.3%), AUC 0.80 (95% CI: 0.77–0.83), p<0.05) in both genders. The optimal WC was 93 cm in men and 90 cm in women with the best trade-off between sensitivity and specificity (men: 87.2% (95% CI: 84.3–89.8%) and 80.2% (95% CI: 74.9–84.8%), AUC 0.91 (95% CI: 0.88–0.92), p<0.05; women: 81.0% (95% CI: 76.9–84.6%) and 88.7% (95% CI: 83.9–92.4%), AUC 0.92 (95% CI: 0.90–0.94), p<0.05). CONCLUSION: For the Chinese patients with type 2 diabetes, the optimal cut-offs for BMI or WC to identify general or abdominal obesity need to be reconsidered.