Background: Metabolic dysfunction-associated steatotic liver disease (MALSD) is defined as the excessive accumulation of triglycerides in the liver in the presence of at least one cardiometabolic risk factor and liver biopsy remains the diagnostic gold standard. This study aimed to evaluate the diagnostic performance of adiposity and metabolism related indices for the non-invasive detection of MASLD and the metabolic dysfunction-associated steatohepatitis (MASH). Methods: A cross-sectional study was conducted in 161 Mexican adults undergoing laparoscopic cholecystectomy, during which liver biopsies were obtained for histological evaluation. Indices such as the Hepatic Steatosis Index (HSI), the Triglyceride–Glucose index (TyG), TyG-BMI (TyG adjusted for body mass index), and TyG-WC (TyG adjusted for waist circumference), among others, were calculated. Results: Of the 161 participants, 66 were diagnosed with MASLD, and 50 of them had histological evidence of MASH. All adiposity and metabolic indices evaluated were significantly higher in MASLD patients compared with controls. Logistic regression identified HSI, TyG, TyG-BMI, and TyG-WC as independently associated with MASLD and MASH, with TyG showing the strongest association. Correlation analyses demonstrated that TyG-BMI and TyG-WC were most strongly associated with histological features of MASH. Receiver operating characteristic curve analyses showed that TyG-WC had the highest diagnostic accuracy for MASLD (AUC 0.721, 95% CI 0.641–0.802) and MASH (AUC 0.735, 95% CI 0.648–0.823), while TyG-BMI displayed high sensitivity (0.758 for MASLD; 0.780 for MASH). Conclusions: Triglyceride–glucose-based indices, particularly TyG-WC and TyG-BMI, showed the highest diagnostic performance for detecting MASLD and MASH, suggesting that these indices may serve as practical, non-invasive tools for identifying individuals at risk.

(1) Background: Evidence regarding Non-Alcoholic Fatty Liver Disease (NAFLD) diagnosis is limited in the context of patients with gallstone disease (GD). This study aimed to assess the predictive potential of conventional clinical and biochemical variables as combined models for diagnosing NAFLD in patients with GD. (2) Methods: A cross-sectional study including 239 patients with GD and NAFLD diagnosed by ultrasonography who underwent laparoscopic cholecystectomy and liver biopsy was conducted. Previous clinical indices were also determined. Predictive models for the presence of NAFLD stratified by biological sex were obtained through binary logistic regression and sensitivity analyses were performed. (3) Results: For women, the model included total cholesterol (TC), age and alanine aminotransferase (ALT) and showed an area under receiver operating characteristic curve (AUC) of 0.727 (p < 0.001), sensitivity of 0.831 and a specificity of 0.517. For men, the model included TC, body mass index (BMI) and aspartate aminotransferase (AST), had an AUC of 0.898 (p < 0.001), sensitivity of 0.917 and specificity of 0.818. In both sexes, the diagnostic performance of the designed equations was superior to the previous indices. (4) Conclusions: These models have the potential to offer valuable guidance to healthcare providers in clinical decision-making, enabling them to achieve optimal outcomes for each patient.