Effect of elevated blood FFA levels on endurance performance after a single fat meal ingestion

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).

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.

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.

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.