The thermic effect of carbohydrate and fat intake before, during, and after graded exercise

Abstract

The thermic effect of meals consisting of predominantly carbohydrate (CHO) or fat (FAT) followed by a graded exercise test was compared to a no meal (NOM) trial in 7 women. Oxygen consumption (VO 2) increased similarly during the 45 min period following both meals (21%-CHO, 23%-FAT), however, total energy expenditure was greatest following CHO due to an increased respiratory exchange ratio (R). No differences between trials in VO 2 or energy expenditure were noted during submaximal or maximal work loads. Following exercise VO 2 decreased to postprandial, pre-exercise levels within approximately 30 min. Oxygen consumption remained elevated 13% in both meal trials at 3h post-meal (2h post-exercise), however, energy expenditure was greater in CHO during the final hour of recovery. It was concluded that CHO and FAT induce similar increases in VO2, however, energy expenditure is slightly greater in CHO due to greater caloric cost of carbohydrate versus fat oxidation. There was no evidence of a diet plus exercise potentiation of VO 2.