Metabolically healthy obesity, transition to unhealthy phenotypes and type 2 diabetes in 0.5 million Chinese adults: The China Kadoorie Biobank

Objectives: To prospectively assess the association of metabolic health status and its transition with incident diabetes risk across body mass index (BMI) categories. Design: Cohort study based on the China Kadoorie Biobank (CKB) Methods: The CKB study enrolled 512,715 adults aged 30-79 years from 10 diverse areas in China during 2004-2008. After exclusion, 432,763 participants were cross-classified by BMI categories and the metabolic status during followed-up for incident diabetes disease. The changes in BMI and metabolic health status were defined from baseline to the second resurvey. Results: Type 2 diabetes risk is higher for metabolically healthy obese (MHO) subjects than metabolically healthy normal weight (MHN) individuals (HR: 3.97, 95% CI: 3.64-3.66), and it is highest for those affected by metabolically healthy obese (MUO) (HR: 6.47, 95% CI: 6.17-6.79). About 15.26% of participants with MHN converted to metabolically healthy overweight or obesity (MHOO), whereas 48.40% of MHOO remained unconverted throughout the follow-up. In obese or overweight people, the conversion from metabolically healthy to unhealthy might increase the chances of developing diabetes as compared to those with a stable metabolic healthy state (HR: 3.70, 95% CI: 2.99-4.59), while those with persistent metabolic disorders are most likely to have diabetes (HR: 8.32, 95% CI: 7.08-9.78). Conclusions: Metabolic healthy is a transient state, and individuals converted from metabolically healthy status to unhealthy phenotypes across all BMI categories might raise the risk of diabetes.