Below is an instruction from Human. Write a response.
    ### Instruction:
    What causes Nonalcoholic steatohepatitis ?
    ### Response:
    What causes nonalcoholic steatohepatitis? The underlying cause of NASH remains unclear. It most often occurs in persons who are middle-aged and overweight or obese. Many patients with NASH have elevated blood lipids, such as cholesterol and triglycerides, and many have diabetes or prediabetes.
    