065 - Protein or Carbs Before Training? It Might Not Matter
The pre-training meal debate has been a staple in every tactical locker room and gym floor: Should you eat protein before morning PT? Do carbs fuel better output? Is fasted cardio the only way to shred fat? In high-demand environments where performance and physique both matter, even small shifts in meal timing can feel critical. This study strips the emotion out and gives us straight data on what happens to fat oxidation, calorie burn, and appetite depending on what you eat, or don’t eat, before training.
Whether you're programming early-morning conditioning or optimizing body comp during deployment prep, here’s what the science says about breakfast and the burn.
What They Found:
This randomized crossover study examined 11 active males who completed treadmill workouts after consuming one of three breakfasts: protein (whey), carbohydrate (maltodextrin), or non-caloric (fasted).
Researchers assessed energy expenditure, fat oxidation, hunger, and total daily caloric intake.
Key findings:
Fat oxidation was highest in the fasted (non-caloric) condition.
Protein and carbohydrate breakfasts resulted in similar fat oxidation and energy intake.
No significant differences were found in post-exercise energy intake, appetite hormone response, or daily caloric consumption between any condition.
The addition of protein pre-exercise did not meaningfully increase energy expenditure or suppress hunger compared to carbohydrate or fasted trials.
What This Means:
For tactical populations where energy efficiency, body composition, and recovery matter, this study suggests that the macronutrient composition of a small pre-exercise breakfast may not significantly affect fat oxidation or energy intake throughout the day. In short: fasted cardio still burns more fat during exercise, but adding protein or carbs before a session won’t dramatically blunt this or change how much you eat later.
Tactical Implications:
Fasted Training Still Wins for Fat Oxidation: For those prioritizing body fat reduction, early sessions without food may be slightly more effective.
Meal Composition Doesn’t Drastically Alter Intake: A small protein or carb meal before training won’t sabotage caloric deficits or encourage overeating later.
Operator Preference Matters: Since performance perception wasn’t measured, those who feel sluggish fasted might still prefer a light breakfast without trade-offs.
No Added Benefit from Protein Pre-Workout: Whey didn’t boost post-exercise metabolism or reduce food intake, contradicting some supplement marketing claims.
Questions To Consider:
Are your early-morning training sessions fueled by habit or strategy?
How might fasted cardio impact your operational readiness or mood throughout the day?
If body comp is your priority, are you optimizing both training and meal timing?
Could simply skipping a small pre-workout snack help maintain a leaner profile?
Are your clients or athletes falsely assuming protein shakes will reduce hunger or intake?
Hillman AR, Cullums L, Peairs A, Miller SA. No difference in fat oxidation, postexercise energy expenditure or energy intake following ingestion of a protein-based breakfast compared to carbohydrate breakfast. Nutr Health. 2025;31(2):729-738. doi:10.1177/02601060241241359