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Nonalcoholic fatty liver disease (NAFLD) has been identified as one of the most prevalent chronic liver disease in adults and children populations. NAFLD is usually associated with the metabolic syndrome (MS), which is chiefly related to insulin resistance and its consequences. Insulin resistance has a crucial role in the pathogenesis of hepatic steatosis and potentially nonalcoholic steatohepatitis (NASH). Because of the contemporary epidemics of MS and obesity, the burden of NAFLD is also expected to rise. Unhealthy diets, such as the so-called western diet, are enriched in fructose, trans-fatty acids and saturated fat and seem to be associated with the development of NAFLD. In human studies, certain dietary sugars, particularly fructose, are used as a substrate for lipogenesis leading to hepatic fatty infiltration, inflammation, and possibly fibrosis. Other investigations have shown that fat consumption especially cholesterol and trans/saturated fatty acids are also steatogenic and seem to increase visceral adiposity. The identification of specific dietary components that favor the development of NASH could be important for the management of this disorder. This review focuses on the effects of different dietary approaches to prevent and treat NAFLD emphasizing the macronutrients and energy composition.

Nonalcoholic fatty liver disease (NAFLD) is currently recognized as one of the most common causes of chronic liver disease. It involves a spectrum of conditions that include pure steatosis without inflammation, steatohepatitis, fibrosis and cirrhosis. The key factor in the pathophysiology of NAFLD is insulin resistance that determines lipid accumulation in the hepatocytes and, thus, oxidative stress, which is followed by inflammatory response. However, NAFLD pathogenesis is still largely unknown and has been extensively investigated. Although life style modification with the aim of losing weight has been advocated to treat this disorder, its effectiveness is limited; additionally, there is no specific pharmacologic treatment until nowadays. Recent evidence suggests that the gut microbiota may play a role in the development of insulin resistance, hepatic steatosis, necroinflammation and fibrosis. Differences in gut microbiota between NAFLD patients and lean individuals as well as presence of small intestinal bacterial overgrowth in NAFLD subjects have been demonstrated. Furthermore, some data indicate that the immunoregulatory effects of probiotics may be beneficial in NAFLD treatment as they modulate the intestinal microbiota; improve epithelial barrier function and strengthen the intestinal wall decreasing its permeability; reduce bacterial translocation and endotoxemia; improve intestinal inflammation; and reduce oxidative and inflammatory liver damage. In this article, we review the clinical trials on the use of probiotics in the treatment of NAFLD and discuss the effects of these agents and their efficacy as an emerging therapeutic resource to treat NAFLD patients.