The Role of Diet in the Management of Non-Alcoholic Fatty Liver Disease: A Systematic Review of Dietary Interventions and Liver Function Improvement

Background: Non-alcoholic fatty liver disease (NAFLD) is an increasing worldwide epidemic disease associated with obesity, insulin resistance, and sedentary life. Due to the lack of any approved intervention in the pharmacologic treatment, dietary intervention still remains a fundamental aspect of NAFLD management. Nevertheless, it has been debated about the relative effectiveness of different dietary approaches. Objective: The objective of this systematic review and meta-analysis was to determine the impact of various dietary interventions namely; low-carbohydrate diets, time restricted eating, ketogenic diets, and anti-inflammatory dietary patterns on hepatic steatosis, liver enzymes, and metabolic outcomes in patients and models of NAFLD. Methodology: The search was done using PubMed, Scopus, and Web of Science with the inclusion of original studies published between 2023 and 2024. There were five recent studies (two clinical cohort studies, one transcriptomic analysis, and two animal model experiments). Dietary intervention trials or observational studies with quantifiable liver-related or metabolic outcome were used as inclusion criteria. Main results scrutinized are alanine aminotransferase (ALT), aspartate aminotransferase (AST), hepatic fat concentration, inflammatory factors, and metabolism indices. There was heterogeneity in the models as well as the reporting of the outcomes hence, results were synthesized narratively. Results: In animal models, very low-carbohydrate, high-protein diet decreased the levels of hepatic triglycerides by 45 percent and inflammatory cytokines were also significantly decreased (p < 0.01). The decrease in serum ALT and AST as a result of Ramadan fasting was very high at 38 and 34, respectively (p <0.001). A ketogenic diet showed temporal decreases in hepatic lipid accumulation, and the maximum effect was achieved at two weeks. In the human investigations, 1-unit increment in the Dietary Inflammatory Index (DII) denoted 25.4 percent increment in the likelihood of NAFLD (OR = 1.254, 95% CI: 1.1781.334; p < 0.001). Yet, transcriptomic profiling showed that there was also a DDR of hepatic DNA present even when diet was not used in the treatment of metabolic steatohepatitis. Conclusion: Nutritional therapy dietary restriction of carbohydrates, ketogenic diets, and anti-inflammatory dietary patterns are also uniformly effective in liver biochemistry and histology in NAFLD, both in humans and animal models. But molecular damage which persists in later stages indicates the importance of early and maintained changes in the diet. These results justify the incorporation of organised nutritional interventions into the management of NAFLD, but further large human studies are needed.