In the quadriceps femoris muscle of obese women the glycogen concentration was significantly lower than in the control group, while protein and DNA values showed no significant differences. After 37 days of intermittent fasting, which consisted of repeated 5-day fasts alternating with 3-day intervals on 500 KCal/day with 60 g protein, in a group of 21 obese women a significant decline of the hexokinase activity in skeletal muscle was found. Other enzymes: triosophosphate dehydrogenase, lactate dehydrogenase, glycerol-3-phosphate dehydrogenase, citrate synthase, malate dehydrogenase and hydroxyacyl-CoA dehydrogenase showed no significant changes. There was a significant fall in concentration of DNA and and glycogen, but the protein concentration did not change.