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Objective: To determine the association between survey-based self-reported problematic low energy availability indicators (LEA-I) and race performance and intra-event medical encounters during the Boston Marathon., Methods: 1030 runners who were registered for the 2022 Boston Marathon completed an electronic survey (1-4 weeks pre-race) assessing LEA-I, training and medical history. De-identified survey data were linked to event wearable timing chips and medical encounter records. LEA-I was defined as: an elevated Eating Disorder Examination Questionnaire score, elevated Low Energy Availability (LEA) in Females Questionnaire score, LEA in Males Questionnaire with a focus on gonadal dysfunction score and/or self-report of diagnosed eating disorder/disordered eating., Results: The prevalence of LEA-I was 232/546 (42.5%) in females and 85/484 (17.6%) in males. Athletes without LEA-I (non-LEA-I) achieved significantly better race times versus those with LEA-I (accounting for demographic and anthropomorphic data, training history and marathon experience), along with better division finishing place (DFP) mean outcomes (women's DFP: 948.9±57.6 versus 1377.4±82.9, p<0.001; men's DFP: 794.6±41.0 versus 1262.4±103.3, p<0.001). Compared with non-LEA-I athletes, LEA-I athletes had 1.99-fold (95% CI: 1.15 to 3.43) increased relative risk (RR) of an intra-event medical encounter of any severity level, and a 2.86-fold increased RR (95% CI:1.31 to 6.24) of a major medical encounter., Conclusion: This is the largest study to link LEA-I to intra-event athletic performance and medical encounters. LEA-I were associated with worse race performance and increased risk of intra-event medical encounters, supporting the negative performance and medical risks associated with problematic LEA-I in marathon athletes., Competing Interests: Competing interests: KEA is a deputy editor for BJSM, (© Author(s) (or their employer(s)) 2025. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ Group.)

Objective: This cross-sectional retrospective and prospective study implemented the 2023 International Olympic Committee Relative Energy Deficiency in Sport (REDs) Clinical Assessment Tool version 2 (CAT2) to determine the current severity of REDs (primary outcome) and future risk of bone stress injuries (BSI, exploratory outcome) in elite athletes., Methods: Female (n=143; 23.3±4.3 years) and male (n=70; 23.1±3.7 years) athletes (performance tier 3 (52%), tier 4 (36%), tier 5 (12%)) participated in a baseline CAT2 (with minor modifications) assessment, including a self-report questionnaire (menstrual function (females), BSI, Eating Disorder Examination Questionnaire (EDE-Q)), bone mineral density (BMD via DXA) and fasted blood analysis (triiodothyronine (T3), testosterone, cholesterol). Athletes were assigned a green, yellow, orange or red light via CAT2. The prospective risk of new self-report of physician-diagnosed BSI was assessed over a subsequent 6-24 months., Results: REDs prevalence was 55% green, 36% yellow, 5% orange and 4% red light. The CAT2 identified a greater prevalence of amenorrhoea and BSI and lower T3, testosterone and BMD (p<0.01) in red, orange and yellow (those with REDs) versus green light. ORs for a prospective self-reported BSI (majority physician diagnosed) were greater in orange vs green (OR 7.71, 95% CI (1.26 to 39.83)), in females with severe amenorrhoea (OR 4.6 (95% CI 0.98 to 17.85)), in males with low sex drive (OR 16.0 (95% CI 4.79 to 1038.87)), and athletes with elevated EDE-Q global scores (OR 1.45 (95% CI 0.97 to 1.97))., Conclusion: The CAT2 has high validity in demonstrating current severity of REDs, with increased future risk of self-reported BSI in athletes with a more severe REDs traffic light category., Competing Interests: Competing interests: MM and KEA are deputy editors of the BJSM., (© Author(s) (or their employer(s)) 2025. No commercial re-use. See rights and permissions. Published by BMJ Group.)

Objectives: To determine the association between surrogates of low energy availability (EA) and proposed health and performance outcomes of Relative Energy Deficiency in Sport (REDs) in a clinical sample of adolescent and young adult male athletes., Methods: Male athletes ages 15-30 years presenting to a sports medicine clinic at two tertiary care centres were invited to complete a survey about athlete health and well-being. Participants were divided into low EA and adequate EA groups based on survey responses. The associations between low EA and REDs outcomes were evaluated using χ 2 tests and ORs were calculated using binomial logistic regression (significance: p<0.05)., Results: Low EA was associated with increased frequency of self-reported immunological, metabolic, psychological, cardiovascular and gastrointestinal dysfunction; reduced endurance performance, response to training, judgement, coordination and muscle strength; and increased irritability and depression. Low EA athletes were more likely to have self-reported cardiovascular dysfunction (OR 2.87, 95% CI 1.56 to 5.26) and psychological illness (OR 3.23, 95% CI 1.91 to 5.41), decreased training response (OR 2.64, 95% CI 1.38 to 5.03) and endurance performance (OR 2.26, 95% CI 1.13 to 4.52) and were less likely to have self-reported gonadal dysfunction (OR 0.49, 95% CI 0.30 to 0.81), than adequate EA athletes (p<0.05)., Conclusions: Low EA surrogates are associated with many adverse health outcomes and performance effects of REDs in male athletes. More prospective REDs research in males is needed to improve various aspects of REDs screening in young male athletes., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2025. Re-use permitted under CC BY-NC. No commercial re-use. See rights and permissions. Published by BMJ Group.)

The 2023 International Olympic Committee (IOC) consensus statement on Relative Energy Deficiency in Sport (REDs) notes that exposure to low energy availability (LEA) exists on a continuum between adaptable and problematic LEA, with a range of potential effects on both health and performance. However, there is variability in the outcomes of LEA exposure between and among individuals as well as the specific manifestations of REDs. We outline a framework for a 'systems biology' examination of the effect of LEA on individual body systems, with the eventual goal of creating an integrated map of body system interactions. We provide a template that systematically identifies characteristics of LEA exposure (eg, magnitude, duration, origin) and a variety of moderating factors (eg, medical history, diet and training characteristics) that could exacerbate or attenuate the type and severity of impairments to health and performance faced by an individual athlete. The REDs Physiological Model may assist the diagnosis of underlying causes of problems associated with LEA, with a personalised and nuanced treatment plan promoting compliance and treatment efficacy. It could also be used in the strategic prevention of REDs by drawing attention to scenarios of LEA in which impairments of health and performance are most likely, based on knowledge of the characteristics of the LEA exposure or moderating factors that may increase the risk of harmful outcomes. We challenge researchers and practitioners to create a unifying and dynamic physiological model for each body system that can be continuously updated and mapped as knowledge is gained., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2023. No commercial re-use. See rights and permissions. Published by BMJ.)

Overall athlete health is a stated priority by the International Olympic Committee (IOC), yet it can be difficult for athletes to safely balance nutritional needs, training load, recovery, social interactions, expectations and other demands. The effect of energy intake and, especially, low energy availability (LEA) on athlete mental health, is understudied. In this narrative review, we examine research that has included psychological factors and mental health variables when investigating the effect of LEA, dieting/restrictive eating and Relative Energy Deficiency in Sport (REDs), since the 2018 IOC consensus statement on REDs. Based on currently available data, early psychological indicators associated with problematic LEA are mood changes, fatigue and psychological conflict. More severe mental health outcomes associated with REDs are reduced well-being, elevated anxiety, depressive symptoms and eating disorders. We propose a psychological model that helps structure how possible risk factors (eg, body dissatisfaction, environmental demands or increased training load) and moderating (eg, gender, sport) and/or potential mediating (eg, social climate, self-esteem) factors are associated with LEA and ultimately REDs. The current scientific literature underscores the importance of including mental health factors when screening for REDs and for developing a clinical approach to address the psychological sequelae of REDs once diagnosed. An interdisciplinary perspective is recommended. Lastly, and importantly, the athlete perspective urges clinicians to not underestimate the drive for success and denial of health consequences that athletes demonstrate when pursuing their sport goals., Competing Interests: Competing interests: MM is a deputy editor of the BJSM and a member of the BJSM IPHP Editorial Board., (© Author(s) (or their employer(s)) 2023. No commercial re-use. See rights and permissions. Published by BMJ.)

In the past decade, the study of relationships among nutrition, exercise and the effects on health and athletic performance, has substantially increased. The 2014 introduction of Relative Energy Deficiency in Sport (REDs) prompted sports scientists and clinicians to investigate these relationships in more populations and with more outcomes than had been previously pursued in mostly white, adolescent or young adult, female athletes. Much of the existing physiology and concepts, however, are either based on or extrapolated from limited studies, and the comparison of studies is hindered by the lack of standardised protocols. In this review, we have evaluated and outlined current best practice methodologies to study REDs in an attempt to guide future research.This includes an agreement on the definition of key terms, a summary of study designs with appropriate applications, descriptions of best practices for blood collection and assessment and a description of methods used to assess specific REDs sequelae, stratified as either Preferred , Used and Recommended or Potential Researchers can use the compiled information herein when planning studies to more consistently select the proper tools to investigate their domain of interest. Thus, the goal of this review is to standardise REDs research methods to strengthen future studies and improve REDs prevention, diagnosis and care., Competing Interests: Competing interests: KEA is a Deputy Editor of the BJSM and an Associate Editor of the BJSM IPHP. MM is a Deputy Editor of the BJSM and a member of the BJSM IPHP Editorial Board. EV is an Associate Editor of the BJSM, an Associate Editor of the BJSM IPHP and Editor in Chief of BMJ Open Sports and Exercise Medicine., (© Author(s) (or their employer(s)) 2023. No commercial re-use. See rights and permissions. Published by BMJ.)

Relative Energy Deficiency in Sport (REDs) is common among female and male athletes representing various sports at different performance levels, and the underlying cause is problematic low energy availability (LEA). It is essential to prevent problematic LEA to decrease the risk of serious health and performance consequences. This narrative review addresses REDs primary, secondary and tertiary prevention strategies and recommends best practice prevention guidelines targeting the athlete health and performance team, athlete entourage (eg, coaches, parents, managers) and sport organisations. Primary prevention of REDs seeks to minimise exposure to and reduce behaviours associated with problematic LEA. Some of the important strategies are educational initiatives and de-emphasising body weight and leanness, particularly in young and subelite athletes. Secondary prevention encourages the early identification and management of REDs signs or symptoms to facilitate early treatment to prevent development of more serious REDs outcomes. Recommended strategies for identifying athletes at risk are self-reported screening instruments, individual health interviews and/or objective assessment of REDs markers. Tertiary prevention (clinical treatment) seeks to limit short-term and long-term severe health consequences of REDs. The cornerstone of tertiary prevention is identifying the source of and treating problematic LEA. Best practice guidelines to prevent REDs and related consequences include a multipronged approach targeting the athlete health and performance team, the athlete entourage and sport organisations, who all need to ensure a supportive and safe sporting environment, have sufficient REDs knowledge and remain observant for the early signs and symptoms of REDs., Competing Interests: Competing interests: MLM is a deputy editor of the BJSM and a member of the BJSM IPHP editorial board. KEA is a deputy editor of the BJSM and an associate editor of the BJSM IPHP., (© Author(s) (or their employer(s)) 2023. No commercial re-use. See rights and permissions. Published by BMJ.)

Relative Energy Deficiency in Sport (REDs) was first introduced in 2014 by the International Olympic Committee's expert writing panel, identifying a syndrome of deleterious health and performance outcomes experienced by female and male athletes exposed to low energy availability (LEA; inadequate energy intake in relation to exercise energy expenditure). Since the 2018 REDs consensus, there have been >170 original research publications advancing the field of REDs science, including emerging data demonstrating the growing role of low carbohydrate availability, further evidence of the interplay between mental health and REDs and more data elucidating the impact of LEA in males. Our knowledge of REDs signs and symptoms has resulted in updated Health and Performance Conceptual Models and the development of a novel Physiological Model. This Physiological Model is designed to demonstrate the complexity of either problematic or adaptable LEA exposure, coupled with individual moderating factors, leading to changes in health and performance outcomes. Guidelines for safe and effective body composition assessment to help prevent REDs are also outlined. A new REDs Clinical Assessment Tool-Version 2 is introduced to facilitate the detection and clinical diagnosis of REDs based on accumulated severity and risk stratification, with associated training and competition recommendations. Prevention and treatment principles of REDs are presented to encourage best practices for sports organisations and clinicians. Finally, methodological best practices for REDs research are outlined to stimulate future high-quality research to address important knowledge gaps., Competing Interests: Competing interests: MM is a Deputy Editor of the BJSM and a member of the BJSM IPHP Editorial Board. KEA is a Deputy Editor of the BJSM and an Associate Editor of the BJSM IPHP. EV is an Associate Editor of the BJSM, an Associate Editor of the BJSM IPHP and Editor in Chief of BMJ Open Sports and Exercise Medicine. RB is the IOC Medical and Scientific Director. LE is the IOC Head of Science Activities and an Editor of BJSM IPHP. UE is an IOC member and the Chair of the IOC Medical and Scientific Commission., (© Author(s) (or their employer(s)) 2023. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: The assessment of body composition (BC) in sport raises concern for athlete health, especially where an overfocus on being lighter or leaner increases the risk of Relative Energy Deficiency in Sport (REDs) and disordered eating., Methods: We undertook a critical review of the effect of BC on performance (29 longitudinal, prospective or intervention studies) and explored current practice related to BC considerations via a follow-up to a 2013 internationally distributed survey., Results: The review found that a higher level of body fat was negatively associated with endurance performance, while a gain in muscle mass resulted in performance benefits across sports. BC did not contribute to early talent identification, and no unique cut-off to signify a performance advantage for BC was identified. BC appears to be one of an array of variables impacting performance, and its influence should not be overstated. The survey (125 practitioners, 61 sports and 26 countries) showed subtle changes in BC considerations over time, such as an increased role for sport dietitian/nutrition practitioners as BC measurers (2013: 54%, 2022: 78%); less emphasis on reporting of body fat percentage (2013: 68%, 2022: 46%) and reduced frequency of BC assessment if ≥every fourth week (2013: 18%, 2022: 5%). Respondents remained concerned about a problematic focus on BC (2013: 69%, 2022: 78%). To address these findings, we provide detailed recommendations for BC considerations, including an overview of preferable BC methodology., Conclusions: The 'best practice' guidelines stress the importance of a multidisciplinary athlete health and performance team, and the treatment of BC data as confidential medical information. The guidelines provide a health focus around BC, aiming to reduce the associated burden of disordered eating, problematic low energy availability and REDs., Competing Interests: Competing interests: Margo Mountjoy is a Deputy Editor of the BJSM and a member of the BJSM IPHP Editorial Board., (© Author(s) (or their employer(s)) 2023. No commercial re-use. See rights and permissions. Published by BMJ.)

Relative Energy Deficiency in Sport (REDs) has various different risk factors, numerous signs and symptoms and is heavily influenced by one's environment. Accordingly, there is no singular validated diagnostic test. This 2023 International Olympic Committee's REDs Clinical Assessment Tool-V.2 (IOC REDs CAT2) implements a three-step process of: (1) initial screening; (2) severity/risk stratification based on any identified REDs signs/symptoms (primary and secondary indicators) and (3) a physician-led final diagnosis and treatment plan developed with the athlete, coach and their entire health and performance team. The CAT2 also introduces a more clinically nuanced four-level traffic-light (green, yellow, orange and red) severity/risk stratification with associated sport participation guidelines. Various REDs primary and secondary indicators have been identified and 'weighted' in terms of scientific support, clinical severity/risk and methodological validity and usability, allowing for objective scoring of athletes based on the presence or absence of each indicator. Early draft versions of the CAT2 were developed with associated athlete-testing, feedback and refinement, followed by REDs expert validation via voting statements (ie, online questionnaire to assess agreement on each indicator). Physician and practitioner validity and usability assessments were also implemented. The aim of the IOC REDs CAT2 is to assist qualified clinical professionals in the early and accurate diagnosis of REDs, with an appropriate clinical severity and risk assessment, in order to protect athlete health and prevent prolonged and irreversible outcomes of REDs., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2023. No commercial re-use. See rights and permissions. Published by BMJ.)

Objective: The purpose of this study was to identify patterns of clustering of the 10 health consequences identified in the Relative Energy Deficiency in Sport (RED-S) framework among collegiate female Cross-Country runners. We also assessed risk characteristics associated with each cluster., Methods: This randomly sampled population included 211 current National Collegiate Athletics Association (NCAA) Division I (DI) female cross country runners who completed a quantitative survey. We used latent class analysis (LCA) to group athletes into mutually exclusive classes based on shared response patterns of RED-S consequences. We computed descriptive statistics to identify demographics, personal characteristics, disordered eating and emotional health characteristics associated with each class., Results: The average age of the sample was 21 years with mean body mass index 20.4 kg/m 2 . The LCA identified three unique classes of potential RED-S presentations: (1) low probability of RED-S consequences; (2) complex physical and psychological concerns with a higher burden of cardiovascular concern and (3) very high probability of anxiety with high burden of menstrual disturbance, bone injury and gastrointestinal concern. All classes were characterised by high levels of menstrual disturbance and distinguished by the number and burden of other potential RED-S consequences and in reported abuse history, emotional regulation and perfectionism., Conclusion: This study identified a high burden of menstrual disturbance in NCAA D1 cross country runners, and three unique presentations of RED-S consequences. Future research is warranted to better understand how early prevention and intervention strategies may mitigate RED-S consequences in distance runners., Competing Interests: Competing interests: None declared., (© Author(s) (or their employer(s)) 2023. No commercial re-use. See rights and permissions. Published by BMJ.)