The risk of nonalcoholic fatty liver disease (NAFLD) among obese individuals without obesity-related metabolic abnormalities, a condition referred to as metabolically healthy obese (MHO), is largely unexplored. Therefore, we examined the association between body mass index (BMI) categories and the development of NAFLD in a large cohort of metabolically healthy men and women.
METHODS:A cohort study was conducted in 77,425 men and women free of NAFLD and metabolic abnormalities at baseline, who were followed-up annually or biennially for an average of 4.5 years. Being metabolically healthy was defi ned as not having any metabolic syndrome component and having a homeostasis model assessment of insulin resistance <2.5. The presence of fatty liver was determined using ultrasound.
RESULTS:During 348,193.5 person-years of follow-up, 10,340 participants developed NAFLD (incidence rate, 29.7 per 1,000 person-years). The multivariable adjusted hazard ratios (95% confi dence intervals) for incident NAFLD comparing overweight and obese with normal-weight participants were 2.15 (2.06-2.26) and 3.55 (3.37-3.74), respectively. In detailed dose-response analyses, increasing baseline BMI showed a strong and approximately linear relationship with the incidence of NAFLD, with no threshold at no risk. This association was present in both men and women, although it was stronger in women ( P for interaction <0.001), and it was evident in all clinically relevant subgroups evaluated, including participants with low infl ammation status.
CONCLUSIONS:In a large cohort of strictly defi ned metabolically healthy men and women, overweight and obesity were strongly and progressively associated with an increased incidence of NAFLD, suggesting that the obese phenotype per se , regardless of metabolic abnormalities, can increase the risk of NAFLD. Am J Gastroenterol 2016; 111:1133-1140 doi: 10.1038/ajg.2016 Specifi cally, it is unclear whether obesity is a risk factor for NALFD in subjects who do not have any of the metabolic abnormalities associated with excess adiposity, a group oft en described as metabolically healthy obese (MHO) ( 11,12 ). Th e health implications of . Only one study has evaluated the association of MHO with NAFLD ( 16 ). In this study, MHO subjects had an increased prevalence of NAFLD compared with metabolically healthy non-obese subjects, but the cross-sectional design of this study limited its ability to establish a temporal relation between obesity and NAFLD.No cohort study has evaluated the role of MHO as a determinant of incident NAFLD among subjects free of NAFLD at baseline. Th erefore, we examined the association between body mass index (BMI) categories and the development of NAFLD in a large cohort of metabolically healthy men and women who participated in a health screening examination program.
METHODS
Study populationTh e Kangbuk Samsung Health Study is a cohort study of men and women 18 years of age or older who underwent a comprehensive annual or biennial health examination at the clinics of the Kangbuk Samsu...
