About 30% of the general population suffers from Non-Alcoholic Fatty Liver Disease, and the incidence of more serious fatty liver disorders increases with obesity. This discusses the current understanding of development of liver disease and the clinical aspects of fatty liver disease by examining the current knowledge regarding the absorption, metabolism of fat in the liver. It summarizes the current knowledge regarding the involvement of oxidative stress, the metabolic effects inflammation, and the effect of nutrition in the disease development and progression.