Author(s): YANG, Y., WANG, Y., CHEN, Y., Institution: NATIONAL TAIWAN NORMAL UNIVERSITY, Country: TAIWAN, Abstract-ID: 1397

INTRODUCTION:
Carbohydrate availability (e.g., muscle and/or liver glycogen) in the human body might play a role in regulating subsequent energy intake. Compared to fed-state exercise, fasted exercise may significantly reduce endogenous glycogen stores, and it may potentially affect appetite and macronutrient choices. Up-to-date, most studies have only used a single ad libitum lunch to assess eating behaviour, and it is still unclear whether food preferences, choices, and dietary behavior in free-living may be affected.
METHODS:
Twenty-four (12 females) healthy and physically active participants (age: 24 ± 4 yr; BMI: 21.3 ± 1.7 kg/m²; V̇O2max: 47 ± 6 ml/kg/min) were recruited, and performed a 60-minute running exercise at 60% V̇O2max in a randomized, counterbalanced order either after an overnight fasting (Fasted-Ex) or consuming breakfast (5.8 kcal/kg, Fed-Ex). Subjective appetite sensation (i.e., hunger, fullness, prospective food consumption and desire to eat) was regularly measured during trials (baseline, 30, 60, 120, 150 and 180 min), and food preference (i.e., fat and taste’s explicit liking, explicit wanting, implicit wanting, and relative preference) was assessed at baseline and 180 min using computerized visual test (i.e., Leeds Food Preference Questionnaire). Free-living eating behavior (total energy intake and macronutrient consumption) was recorded using a weighed food diary for the remainder of the day.
RESULTS:
No difference was observed for exercise intensity between Fasted-Ex and Fed-Ex (60 ± 2% vs. 61 ± 3% V̇O2max, p = 0.058). Compared to Fed-Ex, fat oxidation was higher during Fasted-Ex (27 ± 6 vs. 19 ± 5 g, p < 0.001), and carbohydrate oxidation was lower (62 ± 22 vs. 85 ± 26 g, p < 0.001). Subjective appetite (∆tAUC0-180: Fasted-Ex minus Fed-Ex) was greater in Fasted-Ex than in Fed-Ex (hunger: 2156, p = 0.002; fullness: -1791, p < 0.001; prospective food consumption: 1925, p < 0.001; desire to eat: 2242, p < 0.001). There were no differences in food preferences immediately after exercise or dietary behaviors (first meal and total intake) in the free-living conditions. Moreover, total daily energy, carbohydrate, and protein intake were lower in Fasted-Ex (1697 ± 685 kcal; 215 ± 100 g; 70 ± 27 g) compared to Fed-Ex (2340 ± 664 kcal; 293 ± 95 g; 100 ± 36 g, all p < 0.001).
CONCLUSION:
While fasted-exercise increases subjective appetite, it does not acutely alter food preferences or eating behavior in free-living conditions in physically active adults. Total energy intake remains lower over a 24-hour period in the Fasted-Ex due to breakfast omission.