BACKGROUND: The relationship between the triglyceride glucose (TyG) values and the development of diabetes in non-alcoholic fatty liver disease (NAFLD) patients is not yet well researched. This study aims to examine how the baseline TyG levels correlate with the incidence of new-onset diabetes in this specific cohort. METHODS: This cohort included 2,506 normoglycemic Japanese adults with NAFLD who underwent routine health check-ups at Murakami Memorial Hospital between 2004 and 2015. Several statistical approaches, including restricted cubic splines and two-piecewise linear regression, were utilized to assess the relation between the TyG levels and diabetes risk. RESULTS: Among the 2,506 participants (mean age: 44.78 ± 8.32 years
81.09% male), 203 individuals (8.10%) developed diabetes over the course of the 11-year follow-up period. A U-shaped relationship was observed between the levels of TyG and the onset of diabetes, with an inflection point identified at a TyG value of 7.82 (95% CI: 7.72-8.00). Below this threshold, each one-unit elevation in TyG values reduced the probability of diabetes by 93% (HR = 0.07, 95% CI: 0.01-0.32, P = 0.001). Conversely, above this threshold, each one-unit elevation increased the probability of diabetes by 70% (HR = 1.70, 95% CI: 1.19-2.44, P = 0.004). CONCLUSIONS: The findings validate a U-shaped association between TyG levels and new-onset diabetes in adults with NAFLD. Both low and high TyG levels increase diabetes probability in such a group.