Understanding nutritional interventions and physical exercise in non-alcoholic fatty liver disease.

Non-alcoholic fatty liver disease (NAFLD) is the most common liver disease in adults and its prevalence is rising around the world. This pathology is characterized by accumulation of liver fat, which exceeds 5% of liver weight in absence of alcohol consumption, viral infection or other hepatic etiology. Since NAFLD has been associated with obesity, insulin resistance, diabetes or alteration of lipid profiles, it is considered as the liver manifestation of metabolic syndrome. Pathogenic mechanisms of NAFLD have not been clearly elucidated, but different events such as lipid accumulation, insulin resistance, oxidative and endoplasmic reticulum stress, mitochondrial dysfunction and inflammation are involved. Modifications in lifestyle constitute the first line for the management of NAFLD. Nutritional interventions include low fat and carbohydrate diet with higher polyunsaturated fatty acids ingestion. Moreover, supplementation with antioxidant and cytoprotective agents could be useful to decrease oxidative stress, inflammation and fibrosis. Physical activity enables to reduce the expression of lipogenic genes, fat accumulation, or insulin resistance and improves cardiorespiratory fitness. Benefits have been found following both aerobic exercise and resistance training, and remain even after exercise cessation. However, more studies are required to analyze the molecular and cellular mechanisms involved in nutritional and physical intervention, and to define the volume of activity required and its association with weight loss. In this paper, we offer an updated overview of the mechanisms implicated in the progression of NAFLD, and analyze the beneficial effects of nutritional interventions and physical exercise in the prevention and treatment of this condition.