The Relationships Between Diet Quality Index, Appendicular Skeletal Muscle Mass, and Metabolic Syndrome in a Population with Metabolic Dysfunction-Associated Steatotic Liver Disease: A Single Center from the Yucatan Peninsula

Background/Objectives: Metabolic dysfunction-associated steatotic liver disease (MASLD) is an increasingly prevalent disease closely linked to dietary habits and body composition, particularly reflected in lean mass and markers such as appendicular skeletal muscle mass (ASM). Low ASM can subsequently trigger metabolic abnormalities such as metabolic syndrome (MetS). This study aimed to evaluate the relationships between the diet quality index, ASM, and MetS in individuals with MASLD from the Yucatan Peninsula. Methods: A cross-sectional study was conducted in subjects with a MASLD diagnosis. Diet quality index, anthropometric and biochemical parameters were evaluated. Body composition analysis was utilized to estimate ASM. Correlations between ASM and anthropometric/biochemical parameters were analyzed. Furthermore, comparative analyses were performed between groups stratified by the presence of MetS and low ASM. Results: Fifty subjects were included in the study. Participants exhibited a significantly low diet quality index (57.6 ± 9.78 vs. 100, p < 0.001), alongside a high prevalence of both low ASM and MetS. ASM was positively correlated with BW, WC, and protein mass (p < 0.001), as well as with creatinine and ALT (p < 0.05), and negatively correlated with body fat percentage and TG (p < 0.05). Subjects with low ASM showed significant differences in BW, waist circumference, protein mass, and energy intake compared to those with normal ASM (p < 0.05). Individuals with MetS had higher glucose and blood pressure compared to non-MetS (p < 0.05). Additionally, among patients with MASLD and MetS, those with low ASM exhibited higher glucose and systolic blood pressure compared to those with normal ASM (p < 0.05). Conclusions: Our study demonstrates that adults with MASLD from the Yucatan Peninsula exhibited suboptimal diet quality according to the DQI-I, with a high prevalence of low ASM and MetS. These findings highlight the potential role of the muscle–liver axis in metabolic dysfunction in MASLD.