Abstract
ABSTRACT Background: Low energy availability (LEA) occurs as a result of an insufficient energy intake (EI) which can lead to several physiological and psychological consequences that are characteristic in Relative Energy Deficiency in Sport (REDs). Energy balance (EB) is usually assessed in 24hour(h)-blocks, but this approach has been criticized for neglecting fluctuations in EB within the day. Calculating EB in one-hour intervals and assessing the hourly distribution spent in different EB-zones, also known as Within-day Energy Balance (WDEB) has therefore been advocated to better identify large deficits and Within-day Energy Deficiency (WDED). Notably, there is lack of research in this field, but the WDEB-method can potentially contribute to a better understanding of EB and the possible causes of REDs. Objectives: The main objective of this study was to investigate the effect of a 16-week sports nutrition intervention on WDED for female endurance athletes at risk of REDs. It was also of interest to examine if the WDEB-method and the 24h-EB method generated similar interpretations of energy status, and to investigate the association between WDED and The Low Energy Availability in Females-Questionnaire (LEAF-Q) score. Methods: The FUEL (Food and Nutrition for Endurance athletes – a Learning program) intervention included 16 online lectures in sports nutrition and eight individual athlete- centered nutrition counseling over 16 weeks. Norwegian and Swedish (n=19) female endurance athletes with LEA (a LEAF-Q score > 8) and low risk of eating disorders (EDs) completed seven-day dietary and activity records at baseline (week 0) and post-intervention (week 17) which were used to calculate WDEB, WDED and 24h-EB. Results: There was a significant reduction in hours spent in a negative EB, and WDED was improved from baseline to post-intervention (hours in; EB< 0 kcal: 20.0h vs 5.0h, p = 0.006. EB< -300 kcal: 18.0h vs. 2.0h, p = 0.005. Largest single hour deficit (LSHD): -1686.1 kcal vs. -330.4 kcal, p = 0.002). 24h-EB was also improved (-327.7 kcal vs. 19.9 kcal, p = 0.008), and reductions in total energy expenditure (TEE) (2988 vs. 2846 kcal/day, p = 0.021), exercise energy expenditure (EEE) (1039 vs. 887 kcal/d) and excess post-exercise oxygen consumption (EPOC) (83 vs. 71 kcal/d) were observed from baseline to post-intervention. No significant association between WDED and the LEAF-Q score was found. Conclusion: A 16-week sports nutrition intervention including online lectures and individual nutritional guidance can improve WDED and 24h-EB among female endurance athletes in risk of REDs. The 24h-EB method and the WDEB-method generated the same interpretation of overall energy status, but the latter provided greater insight into daily fluctuations in EB and energy deficits.