Background: Relative Energy Deficiency in Sport (REDs) describes various health and performance complications of problematic low energy availability (LEA). Sex and sport-specific aetiology and risk factors, in addition to the degree of LEA resulting in REDs remain to be adequately described. Objectives: The PhD project consists of three peer reviewed research articles which aimed to 1) Evaluate associations of disordered eating, compulsive exercise and muscle dysmorphia with symptoms of REDs in Icelandic athletes, 2) Compare dietary intake, nutrition status and REDs symptoms in females with different patterns of energy availability and carbohydrate intake and 3) Evaluate associations of the number of LEA days (EA <25 kcal/kg FFM/day) with physiological measures and body image concerns in males. Methods: This cross-sectional investigation was conducted in two parts. First sub-elite and elite athletes from the age of 15 years old were asked to respond to an online questionnaire consisting of the Low Energy Availability in Females Questionnaire (LEAF-Q) or Low Energy Aavailability in Males Questionnaire (LEAM-Q) and demographic questions. A total of 122 female and 90 male respondents were eligible and received invitations to the measurement phase. Thereof, 87 (60 females, 27 males) started the measurements. Body composition was assessed via Dual Energy X-Ray Absorptiometry (DXA) and resting metabolic rate (RMR) with indirect calorimetry. Venous blood samples were collected for evaluation of hormonal and nutrition status. The athletes were asked to log their weighed food intake and training over seven consecutive days via a photo assisted mobile application. Three brief questionnaires were administered as part of the measurement phase: the Eating Disorder Examination - Questionnaire Short (EDE-QS), Exercise Addiction Inventory (EAI), and Muscle Dysmorphic Disorder Inventory (MDDI). Results: Responses to the initial questionnaire indicated that symptoms such as impaired recovery, energy levels and bodily pains are common among Icelandic athletes. Of all athletes included in the measurement phase, 8% (11% of females) exceeded the EDE-QS, 19% the EAI, and 13% the MDDI cut-off. Females considered at risk of REDs according to LEAF-Q scored higher on EDE-QS, EAI and MDDI in addition to having lower Z score for whole body bone mineral density and lower absolute RMR compared to those not at risk. No associations were found between testosterone levels and symptoms of REDs in males, but high MDDI scores were associated with impaired sleep and symptoms such as physical pain and fatigue. Positive associations were also observed between testosterone and iron status. Females with patterns of LEA and low carbohydrate intakes (LEA + LCHO) presented more risk factors and symptoms of REDs compared to the three comparison groups. The LEA + LCHO group displayed more symptoms of disordered eating, had lowest relative intake of all macronutrients, and evaluated their energy levels and recovery worse compared to the group with sufficient to optimal EA and carbohydrate intake (SEA + SCHO). Nutrition status did not differ significantly between groups but a half of the LEA + LCHO group had insufficient to deficient Vitamin D status (<50 nmol/L) compared to none of the SEA + SCHO participants. In males, the number of LEA days was inversely associated with mean total intakes of energy, carbohydrates and iron, and positively with exercise energy expenditure. The number of LEA days was not associated with physiological outcomes and scores on EDE-QS, EAI and MDDI in males. Conclusion: Many Icelandic athletes report symptoms that may indicate REDs, although available screening tools likely overestimate the true prevalence. Disordered eating behaviours, multifactorial body image issues and low or restricted carbohydrate intakes were associated with increased risk of REDs in females especially. Mismatches between training demands and dietary intakes were common, and more work is required to understand potential sex-specific (short to long term) effects of LEA exposures.
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