Nonalcoholic fatty liver disease (NAFLD) is a liver condition characterized by excessive fat accumulation in hepatocytes, often leading to inflammation and liver damage (nonalcoholic steatohepatitis, NASH). It is closely linked to insulin resistance, obesity, and metabolic syndrome, affecting 10-40% of adults globally and being the most common liver disease in children and adolescents in developed countries. NAFLD is associated with serious complications such as hepatocellular carcinoma and cardiovascular disease. While no effective medical treatments exist to reverse NAFLD, lifestyle changes, dietary adjustments, and bariatric surgery are commonly used. Diagnosis typically relies on liver biopsy, though non-invasive methods are being developed to replace or complement it. NAFLD is characterized by fat accumulation in hepatocytes (steatosis), which can progress to NASH with inflammation and fibrosis. The disease is influenced by genetic and epigenetic factors, with variations in the PNPLA3 gene and other genetic variants playing a role in disease progression. Epigenetic changes, such as DNA methylation, also contribute to NAFLD development and progression. Non-coding RNAs, including miR-122, are involved in lipid metabolism and liver fibrosis. NAFLD is diagnosed through exclusion of other liver diseases and by assessing metabolic syndrome components. Blood tests, ultrasound, and MRI are used to detect steatosis, while non-invasive biomarkers like the NAFLD Fibrosis Score (NFS) and FibroTest help assess fibrosis. Elastography techniques, such as transient elastography and ultrasound-based elastography, are used to measure liver stiffness and detect fibrosis. However, these methods have limitations in detecting early fibrosis. NAFLD in children and adolescents is also prevalent, with obesity and metabolic syndrome being key risk factors. Genetic and epigenetic factors, along with environmental influences, contribute to disease progression. Non-invasive diagnostic tools are being validated to improve early detection and management of NAFLD. Despite advances, effective treatments remain limited, and the disease's complexity requires further research into its mechanisms and potential therapeutic strategies.Nonalcoholic fatty liver disease (NAFLD) is a liver condition characterized by excessive fat accumulation in hepatocytes, often leading to inflammation and liver damage (nonalcoholic steatohepatitis, NASH). It is closely linked to insulin resistance, obesity, and metabolic syndrome, affecting 10-40% of adults globally and being the most common liver disease in children and adolescents in developed countries. NAFLD is associated with serious complications such as hepatocellular carcinoma and cardiovascular disease. While no effective medical treatments exist to reverse NAFLD, lifestyle changes, dietary adjustments, and bariatric surgery are commonly used. Diagnosis typically relies on liver biopsy, though non-invasive methods are being developed to replace or complement it. NAFLD is characterized by fat accumulation in hepatocytes (steatosis), which can progress to NASH with inflammation and fibrosis. The disease is influenced by genetic and epigenetic factors, with variations in the PNPLA3 gene and other genetic variants playing a role in disease progression. Epigenetic changes, such as DNA methylation, also contribute to NAFLD development and progression. Non-coding RNAs, including miR-122, are involved in lipid metabolism and liver fibrosis. NAFLD is diagnosed through exclusion of other liver diseases and by assessing metabolic syndrome components. Blood tests, ultrasound, and MRI are used to detect steatosis, while non-invasive biomarkers like the NAFLD Fibrosis Score (NFS) and FibroTest help assess fibrosis. Elastography techniques, such as transient elastography and ultrasound-based elastography, are used to measure liver stiffness and detect fibrosis. However, these methods have limitations in detecting early fibrosis. NAFLD in children and adolescents is also prevalent, with obesity and metabolic syndrome being key risk factors. Genetic and epigenetic factors, along with environmental influences, contribute to disease progression. Non-invasive diagnostic tools are being validated to improve early detection and management of NAFLD. Despite advances, effective treatments remain limited, and the disease's complexity requires further research into its mechanisms and potential therapeutic strategies.