Temporal trends in normal weight central obesity and its associations with cardiometabolic risk among Chinese adults

Normal weight central obesity (NWCO), a distinct phenotype of obesity that is associated with a higher risk of cardiometabolic dysregulation, has received growing attention in the scientific literature. In this study, we aimed to report the prevalence of NWCO in the general Chinese adults and its secular trend from 1993 to 2011. The comorbid cardiometabolic risk of NWCO was also explored. Data from the China Health and Nutrition Survey (CHNS) 1993–2011 were obtained. NWCO was defined as the combination of a BMI of 18.5–23.9 kg/m(2) and 1) a waist circumference (WC) of >85 cm in males or >80 cm in females (NWCO by WC); 2) a waist to height ratio (WHtR) of ≥0.5 (NWCO by WHtR); 3) a waist to hip ratio (WHR) of ≥0.9 in males or ≥0.85 in females (NWCO by WHR). We assessed the trend of NWCO prevalence with the generalized estimating equation method. The demographic, socioeconomic, geographic, behavioural and cardiometabolic predictors of NWCO were explored with multivariable logistic regression. From 1993 to 2011, the age-standardized prevalence of NWCO by WC increased from 6.65% (95% CI: 6.09–7.26) to 13.24% (95% CI: 12.58–13.93), and that of NWCO by WHtR and NWCO by WHR rose from 13.18% (95% CI: 12.41–13.98) to 17.06% (95% CI: 16.35–17.79) and from 16.14% (95% CI: 15.3–17.01) to 19.04% (95% CI: 18.25–19.85) respectively. The associated cardiometabolic factors of NWCO (by WC, WHtR and WHR) were hypertension, diabetes, insulin resistance, decreased insulin sensitivity, low high-density lipoprotein and elevated triglyceride. Moreover, NWCO by WC and NWCO by WHtR were associated with a decreased risk of impaired insulin secretion, and NWCO by WC was additionally linked to elevated total cholesterol. The prevalence of NWCO in the general Chinese adults increased significantly from 1993 to 2011. Effective strategies are needed to combat this epidemic and reduce its deleterious health outcomes.