Acetylcarnitine plays an important role in fat metabolism. A long TE proton magnetic resonance spectroscopy was applied for detection of skeletal muscle acetylcarnitine during the day in fasting and postprandial conditions at whole body 7T MRsystem in the vastus lateralis muscle. Our observation points towards big variations of acetylcarnitine in postprandial state and no significant changes in acetylcarnitine concentrations during the fasting. Moreover, excellent repeatability of the acetylcarnitine 1H MRS based measurement was estimated during three different days in three weeks. Our data emphasize the need for strict standardization of dietary conditions and time point for the measurement of acetylcarnitine.