Relative energy deficiency in sport: a cross-sectional study of nutritional, biochemical and hormonal profiles in Czech female endurance athletes at risk of low energy availability

Introduction Regular physical activity is associated with substantial health benefits, provided the body has sufficient energy sources. However, a long-term low-calorie intake can cause the syndrome of Relative Energy Deficiency in Sport (RED-S) with a significant health threat to athletes. Therefore, the objective of the current study was to evaluate markers of RED-S in a cohort of female athletes. Methods The study was carried out in a cohort of female endurance athletes ( n = 23) and healthy female control subjects ( n = 21) recruited from a total of 42 athletes and 45 controls who underwent the Low Energy Availability in Females Questionnaire (LEAF-Q) survey. Anthropometric, nutritional, and laboratory analyses were performed on study subjects. Results A higher LEAF-Q score signifying low energy availability (LEA) was observed in athletes compared to controls (8 vs. 5, p < 0.005). Menstrual problems were significantly more common in athletes, with 33.3% of athletes having amenorrhea ( p < 0.001). Compared to control women with LEAF-Q < 8, energy expenditure was higher ( p < 0.001) in athletes with LEAF-Q ≥ 8, and athletes had a negative energy balance (90%) with a very low value of energy availability (24.3 kcal/kg FFM/day). Athletes with a LEAF-Q score ≥8 had lower serum concentrations of estradiol ( p < 0.001), progesterone ( p < 0.001), leptin ( p < 0.001), white blood cells ( p < 0.005) and phosphorus ( p < 0.005). Furthermore, they had significantly higher concentrations of hepcidin ( p < 0.05) and free T3 ( p < 0.05). Discussion LEA is prevalent in female endurance athletes, and its diagnosis deserves a multifactorial approach with anthropometric and nutritional analyses, and the use of a wider range of laboratory markers.