Metabolic impact of protein feeding prior to moderate-intensity treadmill exercise in a fasted state: a pilot study

Abstract

BackgroundAugmenting fat oxidation is a primary goal of fitness enthusiasts and individuals desiring to improve their body composition. Performing aerobic exercise while fasted continues to be a popular strategy to achieve this outcome, yet little research has examined how nutritional manipulations influence energy expenditure and/or fat oxidation during and after exercise. Initial research has indicated that pre-exercise protein feeding may facilitate fat oxidation while minimizing protein degradation during exercise, but more research is needed to determine if the source of protein further influences such outcomes.MethodsEleven healthy, college-aged males (23.5 ± 2.1 years, 86.0 ± 15.6 kg, 184 ± 10.3 cm, 19.7 ± 4.4%fat) completed four testing sessions in a randomized, counter-balanced, crossover fashion after observing an 8–10 h fast. During each visit, baseline substrate oxidation and resting energy expenditure (REE) were assessed via indirect calorimetry. Participants ingested isovolumetric, solutions containing 25 g of whey protein isolate (WPI), 25 g of casein protein (CAS), 25 g of maltodextrin (MAL), or non-caloric control (CON). After 30 min, participants performed 30 min of treadmill exercise at 55–60% heart rate reserve. Substrate oxidation and energy expenditure were re-assessed during exercise and 15 min after exercise.ResultsDelta scores comparing the change in REE were normalized to body mass and a significant group x time interaction (p = 0.002) was found. Post-hoc comparisons indicated the within-group changes in REE following consumption of WPI (3.41 ± 1.63 kcal/kg) and CAS (3.39 ± 0.82 kcal/kg) were significantly greater (p < 0.05) than following consumption of MAL (1.57 ± 0.99 kcal/kg) and tended to be greater than the non-caloric control group (2.00 ± 1.91 kcal/kg, p = 0.055 vs. WPI and p = 0.061 vs. CAS). Respiratory exchange ratio following consumption of WPI and CAS significantly decreased during the post exercise period while no change was observed for the other groups. Fat oxidation during exercise was calculated and increased in all groups throughout exercise. CAS was found to oxidize significantly more fat (p < 0.05) than WPI during minutes 10–15 (CAS: 2.28 ± 0.38 g; WPI: 1.7 ± 0.60 g) and 25–30 (CAS: 3.03 ± 0.55 g; WPI: 2.24 ± 0.50 g) of the exercise bout.ConclusionsProtein consumption before fasted moderate-intensity treadmill exercise significantly increased post-exercise energy expenditure compared to maltodextrin ingestion and tended to be greater than control. Post-exercise fat oxidation was improved following protein ingestion. Throughout exercise, fasting (control) did not yield more fat oxidation versus carbohydrate or protein, while casein protein allowed for more fat oxidation than whey. These results indicate rates of energy expenditure and fat oxidation can be modulated after CAS protein consumption prior to moderate-intensity cardiovascular exercise and that fasting did not lead to more fat oxidation during or after exercise.

Effects of Bang® Keto Coffee Energy Drink on Metabolism and Exercise Performance in Resistance-Trained Adults: A Randomized, Double-blind, Placebo-controlled, Crossover Study

“…Importantly, EE in the energy drink condition was found to be approximately 0.77 kcal·min − 1 higher than placebo during the post-beverage time period, and approximately 0.37 kcal·min − 1 higher than placebo during the post-exercise time period. These results align with the findings of previous studies which reported significant elevations in EE following consumption of caffeine-containing energy drinks [ 11 – 13 ] as well as those which administered supplemental protein prior to exercise [ 15 – 17 ]. Several physiological mechanisms are responsible for these results.…”

“…A variety of investigations have demonstrated that the consumption of caffeine-containing energy drinks may acutely increase metabolic rate [11][12][13], which could potentially result in preferential changes in body composition over time with prolonged use [14]. Similar short-term metabolic effects have also been noted following the acute consumption of supplemental protein prior to an exercise session [15][16][17]. For example, Wingfield and colleagues [16] examined the metabolic impact of supplemental protein ingestion prior to aerobic exercise, high-intensity interval training, and resistance training.…”

“…Compared to a calorie-matched carbohydrate condition, protein ingestion resulted in greater energy expenditure and a lower respiratory exchange ratio, suggesting increased fat oxidation and/or decreased exogenous carbohydrate oxidation, during the hour following exercise. Similarly, Gieske et al [15] demonstrated that participants who consumed whey protein or casein protein prior to 30 min of moderate-intensity treadmill exercise had significantly greater within-group changes in energy expenditure following exercise compared to those who consumed a calorie-matched carbohydrate solution or a non-caloric control. Taken together, these results suggest that caffeine-containing products may provide beneficial metabolic effects, particularly when consumed in conjunction with other dietary agents such as additional protein.…”

Pre-Exercise Carbohydrate or Protein Ingestion Influences Substrate Oxidation but Not Performance or Hunger Compared with Cycling in the Fasted State

“…In line with our findings, others have reported a protein-rich pre-exercise meal increased fat oxidation during moderate-intensity exercise compared with a CHO-rich meal [ 34 ], and there were no differences in fat oxidation when consuming whey protein before and during steady-state cycling compared with a placebo (fasted) trial [ 7 ]. Similar levels of fat oxidation between fasted and protein-fed exercise have also been reported during cycling between 58%–86% VO 2max [ 10 ], running at 55%–60% heart rate reserve [ 9 ], and cycling at ~50% VO 2max in a glycogen-depleted state [ 8 ]. A primary reason endurance athletes perform fasted-state training is a desire to increase fat oxidation during exercise [ 6 ], and our findings provide further evidence supporting the use of both pre-exercise protein ingestion and fasted-state training to increase fat oxidation during low-intensity exercise compared with a CHO-rich breakfast, which likely impairs fat oxidation.…”

“…Therefore, pre-exercise protein ingestion may be an alternative to performing fasted-state training that could reduce hunger while maintaining high levels of fat oxidation. Additional research is needed to better understand differences in substrate oxidation between CHO-fed, protein-fed, and fasted-state training, as previous studies using pre-exercise protein ingestion have either not had a CHO control group [ 7 , 8 ], performed extended exercise at a single intensity [ 7 , 8 , 9 ], or provided very large (>1000 kcal) pre-exercise meals [ 10 , 11 ].…”