One-third of the US population has non-alcoholic fatty liver disease (NAFLD) due to obesity and ~8 million of these individuals have a progressive form of the disease, non-alcoholic steatohepatitis (NASH). Currently, there are no noninvasive ways to determine which individuals with NAFLD will develop NASH. This is of medical importance since NASH can be a prelude to the development of end-stage liver disease.