Author(s): HAYASHI, N., LIN, C., YAMADA, M., ISHIKAWA, A., SAKAMAKI-SUNAGA, M., GOTO, K., Institution: NIPPON SPORT SCIENCE UNIVERSITY, Country: JAPAN, Abstract-ID: 1480

INTRODUCTION:
Low energy availability (LEA) occurs when there is an imbalance between energy intake and energy expenditure. Carbohydrate (CHO) intake in a state of LEA may decrease by 20-60% (Mountjoy et al., 2023), which can lead to alteration of CHO availability in the body. The different CHO availability may affect beta-hydroxybutyrate (BHB) concentration and glucose metabolism during endurance exercise in short-term LEA status (i.e., adaptable LEA). Therefore, the present study investigated the effect of different CHO intakes on BHB concentration and glucose metabolism in a state of adaptable LEA.
METHODS:
Nineteen active men and women are allocated to LEA with a higher CHO (HCHO, 70%CHO; 4.9 ± 0.5g/kg CHO) intake group [n = 9 (4 women, 5 men); Age, 23 ± 3 yrs; VO2peak 47.4 ± 5.2 ml/kg/min] or LEA with a lower CHO (LCHO, 35%CHO, 2.3g/kg CHO) intake group [n = 10 (6 women, 4 men); 23 ± 2 yrs; VO2peak 48.5 ± 6.6 ml/kg/min] during a 3-day endurance training. Then, participants consumed the prescribed diet (20 kcal/FFM with higher or lower CHO diet) during the 3-day training. Before and after the intervention (pre, post), they conducted a 60-minute treadmill running at 70%VO2peak, and blood samples were collected before (at rest), immediately, 1 hour, and 3 hours after the completion of the exercise. Respiratory samples were collected before exercise (at rest) and during exercise at 25-30 minutes and 55-60 minutes.
RESULTS:
Serum BHB concentrations significantly increased 3 hours after exercise both pre- (p = 0.000) and post-intervention (p = 0.000). Serum BHB concentration was significantly higher post-intervention than pre-intervention (p = 0.000); however, no difference was observed between the HCHO and LCHO groups. Post-intervention presented a significantly lower blood glucose concentration when compared to pre-intervention (p = 0.015). The LCHO group showed significantly lower RER at rest (p = 0.020) and during exercise at 25-30 minutes (p = 0.000) and 55-60 minutes (p = 0.000). The HCHO group presented a significantly lower respiratory exchange ratio (RER) during exercise at 55-60 minutes (p = 0.000). The LCHO group tended to decrease in CHO oxidation post-intervention than pre-intervention (p = 0.051); however, the HCHO group did not reveal a significant difference between pre-and post-intervention. Fat oxidation at rest and during exercise at 25-30 minutes and 55-60 minutes significantly increased post-intervention than pre-intervention (p = 0.027, p = 0.000, p = 0.000, respectively); however, no significant difference was observed between the groups.
CONCLUSION:
The different CHO intakes did not affect BHB increases and glucose metabolism when in a state of LEA. Therefore, lower CHO intake in adaptable LEA may not further impair glucose metabolism and/or cause acute further training adaptation.