2. Fat oxidation study: After the 3 months observation period subjects will meet in the lab at 9.00 a.m. Two catheters will be inserted in arm veins, one in the cubital vein for stable isotope infusion and one in the distal cephalic vein for blood sampling. The subjects will receive a primed, constant rate infusion of [U-13C]-palmitate (0.0026 mg kg-1 min-1, primed by a 0.085 mg kg-1 NaH13CO3 bolus, NB! non-radioactive and non-dangerous tracers). Two hours after the start of the isotope infusion, subjects will cycle to exhaustion or for maximum 60 min. at a workload of 50-60% of VO2max as previously determined. Heart rate and the level of perceived exertion (Borg Scale) will be monitored every other minute during exercise. Blood and expired gases for isotope measurements will be collected at 10 min intervals at rest and during exercise. Expired air will be collected in a 15 L Douglas bag, and 10 ml air samples from the bags will be injected into vacutainer tubes for analyses of 13CO2 enrichment. Blood samples for acyl carnitines will be collected after 30 and 60 min. of exercise or at exhaustion, and three hours after exercise. Enzyme activity of CPT II and VLCAD will be measured on leucocytes. The above-described test will be executed both before and after each treatment period.