['This study investigated the effect of fatty liver disease (FLD) on the risk of incident type 2 diabetes in a population with metabolically healthy obesity (MHO).', 'The study population comprised 34,258 Koreans without type 2 diabetes. Participants were stratified by BMI (cutoff value, 25.0 kg/m(2) ) and metabolic health state (using Wildman criteria). FLD was defined by the fatty liver index (FLI), a predictive algorithm to detect FLD. Subjects were classified into low and high FLI groups based on tertile.', 'At baseline, there were significant differences in FLI between four study groups. During a median follow-up of 36.5 months, 1.7% individuals developed type 2 diabetes. The risk of incident type 2 diabetes varied for the MHO group according to the level of FLI. The risk of type 2 diabetes in the MHO with low FLI was not significantly elevated compared with the metabolically healthy individuals without obesity (MHNO) with low FLI (multivariate-adjusted HR, 1.19 [95% CI 0.66-2.14]). However, the MHO with high FLI had an elevated risk of incident type 2 diabetes (multivariate-adjusted HR, 1.99 [95% CI 1.36-2.92]).'] Is fatty liver index a risk determinant of incident type 2 diabetes in a metabolically healthy population with obesity?