Acute Nutritional Ketosis in VLCAD Deficiency

Inclusion Criteria: \- Confirmed VLCADD by genetic profiling Exclusion Criteria: * contraindications for MRI studies (assessed by standardised questionnaire as previously used in METC 08-267/K; see UMCG section F METC documents) * inability to perform bicycle exercise. * recent episode of rhabdomyolysis, or treatment for acute renal failure in the past 2 months. * intercurrent illness which may influence exercise tolerance (anaemia, musculoskeletal injury, or other undiagnosed illness under investigation). * known coronary artery disease, positive history for angina, or changes on ECG suggestive of previous ischaemia without a negative stress test. * insulin-dependent diabetes mellitus. * loss of, or an inability to give informed consent. * pregnancy or current breastfeeding, or females not taking the oral contraceptive pill (this is due to the variability in hormonal patterns and substrate levels with different parts of the menstrual cycle). * any other cause which in the opinion of the investigators, may affect the volunteers ability to participate in the study.