OBJECTIVE:Obesity is one of the most common risk factors for cardiometabolic diseases in Australia and worldwide. Recent studies show that people with normal body mass index (BMI) but with central obesity are at increased risk of morbidity and mortality from cardiometabolic diseases. This risk has not been explained well. The aim of this study was to examine the magnitude, correlates and effects of normal BMI central obesity in the Australian adult population. STUDY DESIGN:Longitudinal study with data linkage. METHODS:We used the Baker Biobank, which contains sociodemographic, behavioural, clinical and mortality data. Data were collected between 2000 and 2011 from 6530 adults who were between 18 and 69 years of age. Biobank data were linked to the National Death Index. A matrix of BMI and waist-to-height ratio (WHtR) and waist-to-hip ratio (WHR) were used to create adiposity categories. For analysis, we used descriptive statistics, logistic regression and cox regression models. RESULTS:The overall prevalence of normal BMI central obesity was 13.4% by WHtR and 14.4% by WHR. Gender, age, BMI and physical activity were associated with normal BMI central obesity. Higher odds of multimorbidity and increased hazards of all-cause and cardiovascular mortality were associated with WHR. CONCLUSION:WHtR and WHR, when each used with BMI, provided similar estimates of prevalence of normal BMI central obesity. However, WHR is a better predictor of all-cause and cardiovascular mortality.