Gut Microbiota, Diet and Lipid Metabolism in Adolescents with NAFLD and Their Role in Preventive Strategies

Adolescence is a metabolically vulnerable period, during which rapid physiological maturation coincides with the dynamic remodelling of the gut microbiome. This narrative review summarises evidence from 2015 to 2025 to clarify how disturbances to the gut-liver axis driven by dysbiosis contribute to the development and progression of non-alcoholic fatty liver disease (NAFLD) in young people. Based on a systematic search of the databases PubMed, Scopus and Web of Science, we outline the basis of bidirectional communication between the gut and liver and emphasise how microbial imbalance alters the handling of lipids in the liver by enhancing de novo lipogenesis, impairing fatty acid oxidation and disrupting AMPK signalling and mitochondrial function. Consistent findings from clinical and experimental studies show that adolescents with NAFLD exhibit reduced microbial diversity, the enrichment of ethanol- and LPS-producing taxa, and altered short-chain fatty acid profiles. Each of these is associated with hepatic inflammation and metabolic reprogramming. Microbial molecules, including LPS, secondary bile acids and branched-chain amino acid metabolites, activate TLR4-NF-κB pathways, promote Kupffer cell activation and intensify oxidative stress. These mechanisms intersect with factors specific to adolescence, such as increased adiposity, hormonal shifts and diet-induced metabolic strain. Dietary patterns emerge as key modulators of these processes. Westernised diets promote dysbiosis and endotoxemia, whereas Mediterranean, fibre-rich and plant-based diets enhance SCFA production, strengthen epithelial integrity and modulate adiponectin-dependent hepatic metabolism. Micronutrient-sensitive epigenetic regulation, particularly that involving folate, choline and polyphenols, also plays a role in shaping lipid homeostasis and inflammatory tone. We also highlight emerging evidence that the activation of cytoprotective pathways, especially Nrf2, is dependent on lifestyle factors and links antioxidant-rich functional foods and physical activity to improved mitochondrial resilience and microbiome stability. We evaluate therapies targeting the microbiome, including probiotics, prebiotics, synbiotics and postbiotics, which reduce endotoxemia, restore microbial balance and complement dietary strategies. Thus, these findings emphasise the importance of age-specific, mechanistically informed interventions that integrate diet quality, microbial ecology, and the molecular pathways that govern metabolic health in adolescents with NAFLD.