The effects of low energy availability (LEA) on metabolism, bone, reproductive markers, and mood states in endurance runners

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Type
Thesis
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Author
Sim, Alexiaa
Supervisor
Burns, Stephen Francis
Abstract
Low energy availability (LEA) occurs when there is insufficient dietary energy intake to account for energy needed for exercise and to sustain daily physiological functions. LEA tends to manifest more in physically active populations (i.e., athletes), and when unaddressed can lead to undesirable health and performance outcomes. Literature suggests that individual involved in endurance running are prone to LEA due to the high training demands that are not matched by concomitant high energy intake. However, the reported prevalence of LEA in endurance runners is widespread, ranging from 6%-92%, partly because of the variety of methods that can identify LEA. Furthermore, these methods are mostly validated in females, even though existing studies have used them in both sexes. The common methods are the Low Energy Availability in Females Questionnaire (LEAF-Q), measured Energy Availability (EA) of ≤ 30 kcal/kg Fat Free Mass (FFM)/ day, and a Resting Metabolic Rate (RMR) ratio ≤ 0.90. Therefore, the main aims of the thesis were: (i) to examine the prevalence of LEA risk and its association(s) with related risk factors in endurance runners in Singapore (Study 1); (ii) compare the methods of LEA risk identification (LEAF-Q, measured EA, RMRratio) and determine which have stronger association(s) with LEA risk factors and markers (Study 2); and (iii) investigate the short-term effects of LEA on associated risk markers (metabolism, bone, reproductive, and psychological) in male endurance runners (Study 3). Findings from this thesis can potentially inform practitioners and/or researchers of how to better detect LEA early. They could also improve guidance for athletes on how to better attain optimal EA via dietary energy intake to account for their exercise energy expenditure and daily physiological functions.

Study 1 included 126 endurance runners (47 females, 79 males) who completed an online questionnaire that included self-reported items related to participants’ characteristics: height and weight, exercise/ training frequency and intensity, and questionnaires on disordered eating, exercise addiction, LEA, and the Male Athlete Triad. Study 2 was conducted as a cross-sectional study design which involved 20 male and 20 female endurance runners from Study 1. The participants completed several measurements in the laboratory – RMR, blood markers (metabolism, bone turnover, and reproductive), and a maximal oxygen uptake test (V̇ O2max) test. The participants were classified as at-risk of LEA and not-at-risk of LEA based on the LEAF-Q, self-reported three-day food diary and exercise log (measured EA), and RMRratio. Study 3 was an experimental study that used a randomised, repeated measures study design with three conditions of controlled EA (15, 30, 45 kcal/kgFFM/day) on 12 male endurance runners. Each EA condition lasted for a period of four days, through a controlled DEI (prescribed meal plans) and EEE (standardised exercise protocol).

The findings from this thesis showed that a substantial proportion (18-50%) of endurance runners at LEA risk, with more males at risk than females. The prominent risk factors associated with LEA risk were disordered eating (measured by SCOFF questionnaire, and Brief Eating Disorder in Athletes Questionnaire), and exercise addiction (Exercise Addiction Inventory), suggesting that LEA can possibly be managed by targeting these factors. Secondly, the existing methods to identify LEA risk do not clearly differentiate between at risk and not at risk, as there were few significant differences in biomarkers between the two groups. Therefore, future studies need to refine and (re)validate the cut-offs in both sexes to improve the sensitivity of LEA identification. Lastly, short term LEA at 15kcal/kgFFM/day decreased testosterone and increased fatigue in male runners. These signs have the potential to be used as early markers of LEA in male runners. Endurance runners and individuals who play a role in athletes’ health and performance, including coaches, clinicians, etc, can apply this thesis’ findings to better understand how LEA can be identified, prevented, and managed, by measuring markers such as testosterone and mood states, and monitoring risk factors such as disordered eating on a regular (annual) basis.

Keywords
Date Issued
2023
Call Number
QP176 Sim