 A condition called non-alcoholic steatohepatitis is characterized by fat accumulation in the liver and associated inflammation. This condition is strongly associated with obesity, insulin resistance and type 2 diabetes. Diets high in saturated fat result in fatty liver, insulin resistance and liver injury in animal models. Dietary composition may contribute not only to hepatic fat accumulation and insulin resistance but may also promote inflammation leading to chronic liver disease in humans. This study will test the hypothesis that a diet high in fat and saturated fat contributes to liver fat accumulation, insulin resistance and inflammation by comparing the effects of a four-week, weight stable high fathigh saturated fat diet 55 calories from fat25 saturated fat with a four-week, weight stable low fatlow saturated fat diet 20 fat8 saturated fat in overweight and obese subjects. 