Skipping Breakfast Before Exercise Creates a More Negative 24-hour Energy Balance: A Randomized Controlled Trial in Healthy Physically Active Young Men

Abstract

Background: At rest, breakfast omission lowers daily energy intake, but also lowers energy expenditure, attenuating any effect on energy balance. The effect of breakfast omission, on energy balance when exercise is prescribed, is unclear. Objective: The aim was to assess the effect of pre-exercise breakfast omission versus consumption on 24-h energy balance. Methods: Twelve healthy physically active young men (age 23 ± 3 years, body mass index 23.6 ± 2.0 kg·m-2) completed three trials in a randomized order (seperated >1 week): a breakfast of oats and milk (431 kcal; 65 g CHO, 11 g FAT, 19 g PRO) followed by rest (BR); breakfast before exercise (BE; 60 min cycling at 50% peak power output); and overnight-fasting before exercise (FE). The 24-h energy intake was calculated from breakfast, and an ad libitum lunch, snacks and dinner. Indirect calorimetry with heart-rate-accelerometry were used for substrate utilization and 24-h energy expenditure. A [6,6-2H2]-glucose infusion was used to investigate tissue-specific carbohydrate utilization. Results: Energy balance (24 h) was -400 kcal (normalized 95 % confidence intervals: -230 to -571 kcal) with exercise and breakfast ommision (FE), and this was significantly lower than the rest trial (BR; 492 [332 to 652] kcal) and also the exercise but with prior breakfast consumption (BE; 7 [-153 to 177] kcal; both P