The Effect of Exercise Intervention on Insulin Resistance in Non-alcoholic Fatty Liver Disease (NAFLD)

Inclusion Criteria: * Sedentary, non smoking, male subjects, * Alcohol consumption men \<21 units/week, * BMI 27-35. (Lean individuals do not suffer from NAFLD, so are not suitable for this study. Conversely, we are restricted to a maximum BMI of 35 due to the size limitations of the MR scanner.) * A clinical diagnosis of NAFLD based upon the following criteria: i) exclusion of other causes of liver disease i.e. negative Hepatitis B and C serology, a negative auto-immune profile and normal caeruloplasmin concentrations, ii) Ultrasound appearances suggestive of a fatty, echo-bright liver with no evidence of cirrhosis (in some cases, the diagnosis will have been confirmed histologically after liver biopsy. * Being willing to engage and motivated to follow an exercise program. Exclusion Criteria: * Prescription of corticosteroids, amiodarone, tamoxifen, methotrexate (drugs known to cause secondary steatohepatitis) or fibrates. Statin is Ok as long as the patients are on stable therapy for a while, if changed then the patient will be excluded. * Alcohol consumption for men 21 units/week. * A contraindication to exercise (such as unstable ischaemic heart disease), * Type 2 diabetes (type 2 diabetes patients are excluded so that we are examining the involvement of insulin resistance at a reversible stage before β-cell failure has occurred). * Patients who are on medications that will interact with GTN (glyceryl trinitrate) will be excluded from the GTN dilatation (endothelial independent NO mediated function) aspect of the study. * Individuals who suffer from claustrophobia and have metal implants will be excluded from the MRI aspect of the study. * Patients who smoke will also be excluded from the study. * Total cholesterol \>7