Postexercise fat intake repletes intramyocellular lipids but no faster in trained than in sedentary subjects

1 Nestlé Research Center, Nestec Ltd., CH-1000 Lausanne 26, Switzerland; 2 Department of Anatomy, University of Bern, 3 Department of Clinical Research (Magnetic Resonance Spectroscopy and Methodology), University of Bern and Inselspital of Bern, and 4 Division of Endocrinology and Diabetology, Inselspital of Bern, CH-3010 Bern, Switzerland The hypotheses that postexercise replenishment of intramyocellular lipids (IMCL) is enhanced by endurance training and that it depends on fat intake were tested. Trained and untrained subjects exercised on a treadmill for 2 h at 50% peak oxygen consumption, reducing IMCL by 26-22%. During recovery, they were fed 55% (high fat) or 15% (low fat) lipid energy diets. Muscle substrate stores were estimated by 1 H (IMCL)- and 13 C (glycogen)-magnetic resonance spectroscopy in tibialis anterior muscle before and after exercise. Resting IMCL content was 71% higher in trained than untrained subjects and correlated significantly with glycogen content. Both correlated positively with indexes of insulin sensitivity. After 30 h on the high-fat diet, IMCL concentration was 30-45% higher than preexercise, whereas it remained 5-17% lower on the low-fat diet. Training status had no significant influence on IMCL replenishment. Glycogen was restored within a day with both diets. We conclude that fat intake postexercise strongly promotes IMCL repletion independently of training status. Furthermore, replenishment of IMCL can be completed within a day when fat intake is sufficient. muscle; triacylglycerol; glycogen; insulin sensitivity; proton magnetic resonance spectroscopy