(P16-043-23) The Effects of Vigorous Intensity Exercise and Dietary Manipulation on Substrate Oxidation in the Postprandial Period

Objectives: To define the effects of vigorous-intensity exercise and refeeding on oxygen consumption and substrate oxidation in the postprandial period.

Methods: Healthy male participants (n=9, age: 27 ± 5 BMI: 22.8 ± 1.7 kg/m²) completed a graded exercise test to determine VO₂max and provided a fasting blood sample to evaluate blood lipids and glucose. Participants returned on 4 occasions that included 3 exercise sessions and 1 non-exercise control session (CON). Each testing day, participant’s initial resting respiratory gasses and substrate oxidation were measured for a period of 30 minutes with the final 20 minutes used for analyses. On exercise testing days, participants ran at 75-85% VO₂max until 600kcals were expended. Immediately after exercise, participants consumed a 600kcal replacement meal consisting of either carbohydrate (EXCHO), fat (EXFAT) or consumed no replacement meal (EX). At 1h post-exercise, or after initial resting measurement during the CON condition, participants were provided a standardized high-fat test meal designed to provide 1.1 gram of fat per kilogram of bodyweight. At 2h post-high-fat test meal, oxygen consumption and substrate oxidation were measured again. Dependent variables were assessed using Repeated Measures ANOVAs with Bonferroni follow-up. Alpha was set at 0.05 (SPSS v. 27).

Results: There were no significant differences in resting oxygen consumption (p=0.65) or RER (p=0.84) for any condition. Postprandial VO₂ (ml/kg/min) was significantly different between conditions (F(3, 24)=5.69, p=0.004, η²=0.42). EXFAT VO₂ (4.51 ± 0.33) was significantly increased compared to CON VO₂ (4.12 ± 0.37; p=0.025) with no significant differences between other group means. There was a significant difference in postprandial RER between conditions (F(3, 24)=29.26, p< 0.001, η²=0.785). RER was significantly greater in EXCHO (0.87 ± 0.04) compared to CON (0.81 ± 0.05; p=0.004), EX (0.78 ± 0.04; p=0.02), and EXFAT (0.76 ± 0.02; p< 0.001). Additionally, CON was significantly greater than EXFAT (p = 0.04).

Conclusions: Replacing energy expenditure following high-intensity exercise in the form of a carbohydrate beverage increased postprandial RER, while replacing calories with a high-fat beverage resulted in increased VO₂.

Funding Sources: Funding was provided by Lipscomb University.