Comparing RMR-Derived Proxy Indicators and LEAF-Q for Detecting Low Energy Availability Risk in Mixed-Sport Female Athletes

Proxy indicators have been proposed as practical screening tools to assess low energy availability (LEA) risk among athletes. We evaluated the utility of the Low Energy Availability in Females Questionnaire (LEAF-Q), resting metabolic rate (RMR) ratio, and relative RMR (rRMR) in identifying LEA risk compared with estimated energy availability (EA). Twenty mixed-sport female athletes (24.8 ± 4.8 years) participated in this cross-sectional study. EA was estimated using four-day food and activity logs. LEAF-Q scores were obtained via questionnaires. RMR was measured via indirect calorimetry while predicted RMR was calculated using the 1980 Cunningham equation. RMR ratio was computed using measured RMR over predicted value, and rRMR computed using measured RMR over fat-free mass (FFM), as assessed by dual-energy X-ray absorptiometry. Participants were classified ‘at risk’ of LEA based on LEAF-Q score ≥8, RMR ratio <0.90, and rRMR <30 kcal/kg FFM/day. RMR-derived measures displayed high sensitivity (100%) and low specificity (44.4%), while LEAF-Q exhibited low sensitivity (27.3%) and moderate specificity (55.6%). EA was moderately correlated with RMR ratio (r = 0.47, p = 0.035) and strongly correlated with rRMR (r = 0.63, p = 0.003). RMR-based measures may be promising rapid screening tools for LEA risk in mixed-sport female athletes.