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

Abstract

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.

Role of proton MR for the study of muscle lipid metabolism

“…However, it has also been found that high IMCL levels correlate with high insulin sensitivity if endurance-trained athletes are compared with healthy sedentary subjects (20). This paradox has been confirmed in biopsy studies (21) and initiated a study on the relation of anthropometric determinants, aerobic capacity, insulin sensitivity and IMCL levels in two different muscle groups (22).…”

“…Boesch et al (2) revealed a decrease of IMCL in one subject performing a mountain bike ride over 3 h at about 70% of VO 2max , for the first time using 1 H-MRS to demonstrate that IMCL are metabolized during this form of exercise. In the following years, numerous reports on reduced IMCL levels during exercise were published and reviewed (17,20,(34)(35)(36)(37)(38)(39)(40)(41)(42)(43)(44)(45)(46)(47)(48)(49). It became obvious that both exercise duration and intensity are important factors in determining the reduction of IMCL (39).…”

“…This observation led to many studies that investigated the effect of short-term diet on IMCL concentrations (17,20,36,(51)(52)(53)(54)(55). It could be shown that the amount of fat in the diet strongly influences the replenishment of IMCL (17).…”

“…Several publications have used 13 C-MR spectroscopy to observe muscular glycogen and 1 H-MRS for an evaluation of IMCL (20,36,37,65). This allows the evaluation of fat and carbohydrate metabolism during exercise and diet.…”

Sustained increase in dietary oleic acid oxidation following morning exercise

“…Furthermore, reports have shown that repletion of the muscle triacylglycerol stores following exercise is dependent on the macronutrient composition of the diet. 28 In particular, a high fat diet (55% fat) leads to complete recovery of previously depleted muscle triacylglycerol stores at 30 h postexercise, while a low fat diet (15% fat) does not. The diet provided in our study was a moderate 30% fat, and perhaps not high enough to quickly replenish any previously utilized muscle triacylglycerol.…”