Preexercise meal composition alters plasma large neutral amino acid responses during exercise and recovery

This study was designed to determine the effect of ingesting three preexercise meals on energy metabolism during exercise and recovery and to relate metabolic perturbations to subjective and objective measurements associated with central fatigue. Twelve subjects consumed isoenergetic meals consisting of oat, wheat, or corn cereals 90 min before cycling. A fasting trial served as the control. Blood samples and cognitive function, perceived hunger, and sleepiness measurements were obtained before and after feeding and during recovery when self-selected food intake was also measured. After meal ingestion, plasma insulin was lower for oat than for wheat or corn whereas the ratio of tryptophan to large neutral amino acids (LNAAs) for corn was less than for all others. During exercise, the tryptophan-LNAA ratio increased from preexercise values for the fasting and wheat trials, but exercise performance was unaffected. During recovery, tryptophan:LNAA increased from postexercise values in fasting trials. Also, hunger and fatigue ratings were greater in fasted subjects, but self-selected food intake measured at the end of the recovery period was not different among groups. We conclude that preexercise meal consumption affected tryptophan:LNAA before, during, and after exercise, but these changes were not sufficient to alter physical and cognitive performance.