Short-term Induced Low Energy Availability On Metabolic Rate And Mood States In Male Runners

Abstract

PURPOSE: To investigate the effect of an acute (4-day) period of low energy availability (EA) on resting metabolic rate (RMR) and mood states in trained male endurance runners. METHODS: 12 male endurance runners (mean (standard deviation); age: 25.8 (3.7) yrs; body mass index: 20.9 (2.0) kg/m2; fat free mass (FFM): 52.8 (5.5) kg) completed three 4-day conditions of controlled EA (15, 30, and 45 kcal/kg/FFM), in a randomised and crossover manner. In each condition, participants ran on a treadmill at 65% of VO2max until they achieved a daily exercise energy expenditure of 15 kcal/kg/FFM. Energy intake was adjusted to achieve the desired level of EA in each condition. RMR and mood states were measured after a 10-12 hour fast on the morning of Day 1 (pre) and Day 5 (post) of each condition. RMR was measured by indirect calorimetry (ventilated hood) and mood states were measured by the Brunel Mood Scale (BRUMS), that consists of six dimensions - fatigue, depression, vigor, anger, tension, and confusion. A two-way repeated measures ANOVA (condition × time) was used to examine differences in RMR. A two-way repeated measures MANOVA (condition × time) was used to examine the differences in BRUMS dimensions. RESULTS: For RMR, no significant interaction was found between condition and time (p = 0.329). For mood states, a significant interaction was found in fatigue scores (p = 0.035). Participants felt greater fatigue (tiredness) in the post measure in the 15 kcal/kg/ FFM condition, as compared to the other conditions (30 and 45 kcal/kg/ FFM). A main effect was found in vigor scores over time (p = 0.036). Participants generally felt more vigor (energy) at the pre than post measure irrespective of EA conditions. CONCLUSIONS: These findings indicate that RMR in male runners was not influenced by short-term LEA induced by restricted energy intake and exercise energy expenditure, suggesting that metabolism may not be affected by acute periods of LEA. Hence, RMR may not be a sensitive enough tool to detect the early stages of LEA. Short-term LEA did affect mood states (fatigue and vigor) in male runners. This suggests that LEA should be adjusted as soon as it is detected to prevent further impact on psychological state. It also suggests that a state of increased fatigue, and/or decreased vigor, could be an indicator or symptom of LEA, in male runners.