PURPOSE: This study was designed to examine the effect of elevated blood free fatty acid (FFA) levels on carbohydrate (CHO) oxidation and cycling performance after ingesting a single fat meal (FM).
METHODS: Four hours before cycling exercise, nine trained males consumed either a FM (4711 kJ; 30% CHO, 61% fat, and 9% protein) or control meal (CM) (4877 kJ; 58% CHO, 31% fat, and 11% protein). The intensity of exercise employed was 67% of the maximal oxygen consumption (VO2max) for the first 120 min of exercise, followed by an increase to 78% VO2max.
RESULTS: The FM ingestion significantly (P < 0.05 and P < 0.01) elevated serum FFA levels above those resulting from CM ingestion almost throughout the entire exercise. A significantly (P < 0.05 and P < 0.01) lower respiratory exchange ratio in the FM versus the CM trials was observed during the first hour of exercise. This was accompanied by a significantly greater amount of fat oxidized at 20 (P < 0.01) and 60 min (P < 0.05) of FM trials and a significantly smaller amount of CHO oxidized at 20 min (P < 0.05) of FM trials. However, endurance time and work production did not differ between the FM (141 +/- 8 min, 134333 +/- 6049 kg x m (SEM)) and CM (138 +/- 5 min, 131450 +/- 4737 kg x m) trials. Also, there were no significant differences in oxygen consumption, heart rate, and perceived exertion or in glucose, lactate, and triglyceride levels in the blood.
CONCLUSIONS: These results suggest that the elevated blood FFA levels after a single FM ingestion reduce CHO oxidation early in exercise, but this decrease in CHO oxidation would not be adequate enough to contribute to an increased endurance.
