No difference in fat oxidation, postexercise energy expenditure or energy intake following ingestion of a protein-based breakfast compared to carbohydrate breakfast.

This study investigated the effects of manipulating the macronutrient content of breakfast—protein (PRO), carbohydrate (CHO), or noncaloric (NON-CAL)—prior to moderate-intensity exercise on exercise energy expenditure, substrate oxidation, and postexercise energy intake in active young men. Results showed that fat oxidation during exercise was highest in the fasted (NON-CAL) condition, with similar fat oxidation between PRO and CHO breakfasts, and no significant differences in postexercise energy intake or appetite-related hormones across trials. Pre-exercise protein intake did not enhance fat oxidation, increase excess postexercise oxygen consumption (EPOC), or reduce subsequent energy intake compared to carbohydrate or fasting. These findings suggest that, under the conditions studied, altering breakfast macronutrient composition before exercise does not significantly impact energy balance or appetite regulation in healthy active males.