Higher TyG Index Linked to 4.36-Fold Increased Odds of NAFLD in Large Meta-Analysis

This systematic review and meta-analysis evaluated the association between the triglyceride-glucose (TyG) index and related composite indices with non-alcoholic fatty liver disease (NAFLD) and related outcomes. The analysis included 212,618 participants from observational studies, both cross-sectional and cohort designs. The primary exposure was the TyG index and its composites: TyG-body mass index, TyG-waist circumference, and TyG-waist-to-height ratio. The primary outcome was NAFLD or steatosis, with secondary outcomes including liver fibrosis and nonalcoholic steatohepatitis (NASH).

For the primary outcome of NAFLD/steatosis, the meta-analysis reported a significant positive association. In continuous-scale analysis, higher TyG levels were associated with increased odds of NAFLD (OR 2.72, 95% CI 2.08-3.55). When comparing the highest versus lowest TyG categories, the odds ratio was 4.36 (95% CI 3.39-5.61). Composite indices also showed positive associations: TyG-body mass index (OR 1.04, 95% CI 1.03-1.05) and TyG-waist circumference (OR 1.01, 95% CI 1.01-1.01). These results indicate a consistent link between higher TyG-related indices and NAFLD.

Secondary outcomes of liver fibrosis and NASH were assessed but with limited evidence, as the review noted insufficient data for robust conclusions. Safety and tolerability were not reported, as this was an observational meta-analysis without intervention.

Compared to prior landmark studies, these findings align with previous research linking insulin resistance markers to NAFLD. However, the high heterogeneity (I²=85.7% and 92.8% for TyG analyses) suggests variability across studies, possibly due to differences in populations, definitions, or methodologies. The observational design precludes causal inference, and the authors caution against overinterpretation.

Key methodological limitations include the observational nature of included studies, high heterogeneity, and limited evidence for fibrosis and NASH. There is a need for standardized outcome definitions and clearer exposure parameterization. The certainty of evidence is moderate to low due to these factors.

Clinically, TyG-related indices may be useful for metabolic fatty liver risk stratification, but further validation is needed before routine use. These indices are inexpensive and readily available, potentially aiding in screening. However, clinicians should not assume clinical utility without prospective studies confirming predictive value.

Unanswered questions include whether TyG indices predict progression to NASH or fibrosis, their role in longitudinal risk assessment, and optimal cutoffs for clinical decision-making. Future research should focus on standardized protocols and prospective designs to establish causality.