Non alcoholic steatohepatitis (NASH), a chronic liver disease characterized by insulin resistance, accumulation of hepatic fat and hepatocellular necroinflammation, has been recognized as a leading cause of (cryptogenic) liver cirrhosis in developed countries. Given the rising prevalence of NASH and the associated socio-economic burden associated, novel therapeutic options are warranted. The incretin mimetic Exenatide (Byetta®) exhibits strong glucoregulatory activities through its multiple biological effects. In addition, exenatide treatment has been shown to improve lipid homeostasis and reduce body weight. Since the development of NASH has been tightly linked to the presence of obesity, hyperlipidaemia and diabetes, this study will examine, whether 24 weeks of treatment with exenatide will also result in improvements in liver function in patients with NASH.