Diet, Weight Loss, and Liver Health in Nonalcoholic Fatty Liver Disease: Pathophysiology, Evidence, and Practice

Fatty liver accumulation results from an imbalance between lipid deposition and removal, driven by the hepatic synthesis of triglycerides and de novo lipogenesis. The habitual diet plays a relevant role in the pathogenesis of nonalcoholic fatty liver disease (NAFLD), and both risky (e.g., fructose) and protective foods (Mediterranean diet) have been described, but the contribution of excess calories remains pivotal. Accordingly, weight loss is the most effective way to promote liver fat removal. Several controlled studies have confirmed that an intense approach to lifestyle changes, carried on along the lines of cognitive-behavior treatment, is able to attain the desired 7%-10% weight loss, associated with reduced liver fat, nonalcoholic steatohepatitis (NASH) remission, and also reduction of fibrosis. Even larger effects are reported after bariatric surgery-induced weight loss in NAFLD, where 80% of subjects achieve NASH resolution at 1-year follow-up. These results provide solid data to evaluate the safety and effectiveness of the pharmacological treatment of NASH. The battle against metabolic diseases, largely fueled by increased liver fat, needs a comprehensive approach to be successful in an obesiogenic environment. In this review, we will discuss the role of hepatic lipid metabolism, genetic background, diet, and physical activity on fatty liver. They are the basis for a lifestyle approach to NAFLD treatment.