Metabolically healthy obesity and development of chronic kidney disease: A cohort study

Background: The risk for chronic kidney disease (CKD) among obese persons without obesity-related metabolic abnormalities, called metabolically healthy obesity, is largely unexplored. Objective: To investigate the risk for incident CKD across categories of body mass index in a large cohort of metabolically healthy men and women. Design: Prospective cohort study. Setting: Kangbuk Samsung Health Study, Kangbuk Samsung Hospital, Seoul, South Korea. Participants: 62 249 metabolically healthy, young and middleaged men and women without CKD or proteinuria at baseline. Measurements: Metabolic health was defined as a homeostasis model assessment of insulin resistance less than 2.5 and absence of any component of the metabolic syndrome. Underweight, normal weight, overweight, and obesity were defined as a body mass index less than 18.5 kg/m², 18.5 to 22.9 kg/m², 23 to 24.9 kg/m², and 25 kg/m² or greater, respectively. The outcome was incident CKD, defined as an estimated glomerular filtration rate less than 60 mL/min/1.73 m². Results: During 369 088 person-years of follow-up, 906 incident CKD cases were identified. The multivariable-adjusted differences in 5-year cumulative incidence of CKD in underweight, overweight, and obese participants compared with normalweight participants were-4.0 (95% CI,-7.8 to-0.3), 3.5 (CI, 0.9 to 6.1), and 6.7 (CI, 3.0 to 10.4) cases per 1000 persons, respectively. These associations were consistently seen in all clinically relevant subgroups. Limitation: Chronic kidney disease was identified by a single measurement at each visit. Conclusion: Overweight and obesity are associated with an increased incidence of CKD in metabolically healthy young and middle-aged participants. These findings show that metabolically healthy obesity is not a harmless condition and that the obese phenotype, regardless of metabolic abnormalities, can adversely affect renal function.