1Department of Internal Medicine I, University Hospital Regensburg, Regensburg, Germany.
Alcoholic liver disease (ALD) and nonalcoholic fatty liver disease (NAFLD) are the most frequent chronic liver disorders, and their advanced forms - alcoholic steatohepatitis and nonalcoholic steatohepatitis - are the most frequent conditions leading to liver cirrhosis and hepatocellular carcinoma worldwide. NAFLD is considered as the hepatic manifestation of the metabolic syndrome. With the pandemic rise of obesity, the incidence of NAFLD is also further increasing, and considering the life style in modern societies, there is a significant overlap of (risk factors causing) NAFLD and (alcohol consumption predisposing for) ALD at least in Western countries. Epidemiological studies propose a causative link between chronic alcohol consumption and progressive liver disease in obese individuals. Furthermore, experimental studies indicate combined pathological effects of alcohol and obesity or fatty acid levels, respectively, on hepatocellular lipid accumulation and injury as well as hepatic inflammation, fibrosis and cancerogenesis. Notably, these combined pathological effects are in part additive but partly even synergistic. And importantly, alcohol does already exhibit synergistic pathological effects with obesity at moderate doses. This indicates significant differences in the dose threshold for hepatotoxic alcohol effects in lean and obese subjects and herewith also has important implications for recommendations for 'safe' alcohol consumption. The purpose of this brief review is to update the knowledge on the combined effects of alcohol and obesity on the development and progression of liver disease. Undoubtedly, alcohol and the metabolic syndrome appear as a dangerous mix, and there are important interactive effects of either condition with regard to crucial triggers of liver injury.