Age‐Related Patterns of Relative Energy Deficiency in Sport (REDs) Symptoms and Key Performance Factors in Adolescent Biathletes

ABSTRACT Relative Energy Deficiency in Sport (REDs) impairs health and performance, but age‐related patterns in its emergence remain unclear. This study examines RED symptoms in adolescent biathletes at season‐start and their link to end‐of‐season performance. A national cross‐sectional study including prospective performance registration recruited biathletes to complete validated questionnaires, followed by clinical interviews if eating disorders (EDs) were indicated. Athletes ≥ 18 years were invited for physical laboratory assessments. End‐of‐season results were retrieved from open records. Analyses were performed by elastic net regression to identify the most stable predictors of performance, which were finally included in a linear regression model. Seventy‐two athletes (55% females) with mean (SD) age 17.8 (1.4) years, 13.3 (3.3) training hours/week, and representing median (min, max) tier 3.0 (2, 5) were included. Prevalence in symptoms of low energy availability (LEA) was 18%, REDs 32%, EDs 11% (20% among females), and of depression 15%. Among 28 athletes (43% female) completing laboratory assessments, 11% had low BMD and ≤ 25% had clinical metabolic markers. Symptoms of mental health issues and REDs were more common in females and the older age groups. Higher training volume and low RED severity positively predicted performance, whereas injury/illness‐related training absences, cholesterol, and body fat percentage negatively affected race results. RED symptoms are common in young biathletes. Illness/injury‐related training absences were frequent and linked to poorer end‐of‐season performance, underscoring the need for routine screening by health‐ and performance teams to detect and manage early symptoms of LEA, reduce RED risk, and prevent premature career termination.