This study involves a multidisciplinary approach that will address the metabolic mechanisms responsible for Non-alcoholic Fatty Liver Disease (NAFLD) in humans. Nonalcoholic fatty liver disease (NAFLD) has become an important public health problem in many industrialized countries because of its high prevalence, potential progression to severe liver disease, and association with cardiometabolic abnormalities, including diabetes, the metabolic syndrome, dilated cardiomyopathy, and coronary heart disease. Although obesity is an important risk factor for NAFLD many obese persons have minimal or no steatosis. The mechanism responsible for the pathogenesis of steatosis is not known, but must involve one or more of the following: