Effect of gender on fuel utilization during exercise at different intensities in untrained Thai individuals

Research in Western populations has demonstrated a gender effect on substrate metabolism during exercise. Women have been shown to use more lipid and less carbohydrate as energy sources during endurance exercise, compared with their male counterparts. Nutritional status influences fuel utilization during exercise. Thai men and women routinely ingest a greater proportion of their dietary energy as carbohydrate than Caucasian individuals and thus may respond differently to exercise. Therefore, this study aimed to investigate the effects of gender on fuel utilization at different exercise intensities in untrained Thai individuals. Sixteen healthy sedentary men and 16 women participated in this study. All participants cycled at a target workload equivalent to 25, 65 and 85% maximum oxygen consumption continuously for 15, 10 and 10 min, respectively. Expired gas samples were collected for 30 min at rest and for the final 5 min of each exercise intensity. Actual relative exercise intensities were 32 +/- 1.7, 64 +/- 1.8, 84 +/- 1.7% maximum oxygen consumption, respectively, and there was no significant difference between genders. Carbohydrate oxidation rate was higher than fat oxidation rate at every exercise intensity in both genders. In untrained Thai individuals, gender did not affect fuel utilization during sub-maximal exercise. The higher utilization of carbohydrate than fat at rest and during exercise in Thai individuals than seen previously in other populations may be due to the Thai's habitual higher dietary carbohydrate intake.