Objective: The aim of the present study was to evaluate the effect of duration on the interaction between training and a fat-rich or a carbohydrate-rich diet on endurance performance.
Methods: Fifteen untrained males were randomly assigned to consume a fat-rich (T-FAT) or a carbohydrate-rich diet (T-CHO) while following an endurance training program. Endurance performance at 80% of pretraining VO2max was measured before, after 2 wk, and after 4 wk.
Results: Time to exhaustion, when exercising at the same absolute workload, was similar in T-FAT and T-CHO at all tests and was significantly increased by 166% and 150% in T-FAT and T-CHO, respectively, after 4 wk. Maximal oxygen uptake increased by 9% in both groups (P < 0.05). After 4 wk, RER was significantly lower during exercise in T-FAT both compared with the initial test and with T-CHO, while no changes appeared in T-CHO.
Conclusions: The present findings showed that endurance performance was enhanced similarly after both 2 and 4 wk of adaptation to training and a fat-rich or a carbohydrate-rich diet.