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

Manipulation of macronutrient intake and exercise can alter overall energy consumption and potentially body composition. : The purpose of this study was to manipulate the macronutrient content of breakfast before exercise to investigate the impact on exercise energy expenditure and postexercise energy intake (EI). Twelve active men were recruited, 11 finished the study protocol (age: 28 ± 9 years; VOmax: 56 ± 5 ml·kg·min). In a randomized crossover design, each participant completed 4 trials, 3 consisting of a specific breakfast (protein, PRO; carbohydrate, CHO; noncaloric; NON-CAL) followed in 1 h by a 45 minutes moderate intensity treadmill exercise protocol. The fourth trial consisted of breakfast and no exercise (CON). An ad-libitum lunch and food for the rest of the day were provided and assessed for EI. Measures included resting metabolic rate pre- and postbreakfast along with oxygen uptake (VO) during and after exercise, along with hunger scales, and blood measures of glucose, insulin and plasma-PYY prebreakfast, pre-exercise, postexercise, and 60 minutes postexercise. Fat oxidation was highest during exercise in the NON-CAL (0.57 g·min) trial with similar levels of fat oxidation between PRO (0.50 g·min) and CHO trials (0.48 g·min). Hunger was not affected by PRO intake or exercise, nor was appetite hormones and glucose. EI at lunch and dinner was not significantly different between trials. Pre-exercise PRO intake did not modify fat oxidation during exercise, did not lead to a larger VO versus CHO, nor did it attenuate EI postexercise.