Optimizing the Beneficial Health Effects of Exercise for Diabetes: Focus on the Liver!

Inclusion Criteria: 1. All subjects: * Male sex * Age 40-70 years * BMI 27-35 kg/m2 * Stable dietary habits * Sedentary: No participation in any kind of sports for at least 2 years. 2. For diabetic patients only: * Must be on sulphonylurea or metformin therapy for at least 6 months with constant dose for at least 2 months, or on a dietary treatment for at least 6 months * Well-controlled diabetes: fasting plasma glucose concentration ≥ 7.0 mmol/l and \< 10.0 mmol/l at the time of screening. 3. For subjects with non-alcoholic fatty liver disease: * Liver fat content ≥ 5,56%, based on the formula of Kotronen et al. and confirmed with MRS. * Fasting plasma glucose concentration must be \< 7.0 mmol/l 4. For control subjects: * Liver fat content \< 5,56%, based on the formula of Kotronen et al. and confirmed with MRS. * Normoglycemic according to the WHO criteria (OGTT) Exclusion Criteria: 1. All subjects: * Female sex * Unstable body weight (weight gain or loss \> 3 kg in the past three months) * Participation in an intensive weight-loss program or in vigorous exercise program during the last year before the start of the study. * Active cardiovascular disease. (This will be determined by questionnaires and by screening on medication. Furthermore, all subjects will undergo a physical examination by a medical doctor). * Chronic renal dysfunction (creatinine \> 2 increased (normal values: 64-104 µmol/l)) * Use of Thiazolidines (glitazone/rosiglitazone/pioglitazone/troglitazone) * Systolic blood pressure \> 160 mmHg or diastolic blood pressure \> 100 mmHg * Haemoglobin \< 7.5 mmol/l (anaemia) * Blood donor * Use of medication known to interfere with glucose homeostasis (i.e. corticosteroids), except for diabetic patients. * Use of anti-thrombotic medication * Claustrophobia and contra-indications for MRI * Abuse of alcohol(\> 3 units (1unit = 10 gram ethanol) per day) * Abuse of drugs * Participation in another biomedical study within 1 month before the first screening visit 2. For diabetics: * Severe diabetes which requires application of insulin or patients with diabetes-related complications 3. For controls: * Liver disease or liver dysfunction (ALAT \> 2.5 x increased)