Introduction Endurance athletes with high training loads and weight focus have increased risk of low energy and carbohydrate (CHO) availability. This is the first study aiming to investigate the timing of CHO intake in relation to training load in athletes with symptoms of relative energy deficiency in sport (RED-S).

Materials and Methods Female endurance athletes (n=12) (25.9 ± 4.4) years, BMI 20.9 ± 2.1), with symptoms of RED-S (Low Energy Availability in Females Questionnaire total score 11.9 ± 2.9) without disordered eating behavior, performed a 7-day weighed dietary and training registration (heart rate monitors, online training logs). CHO intake was analyzed for key (high intensity/>120 min) and easy training sessions (all other sessions >30 min) as well as hard (including >1 key session) and light training days (all other days). Mean difference, 95% confidence intervals (CI) not including 0, and a paired student t-test were used to determine differences between CHO intake and international sport nutrition recommendations.

Results None of the participants met the recommended daily CHO intake [CI -1.7 (-2.4 to -0.9)], or CHO intake immediate after [CI -0.7 (-0.9 to -0.5)], between [CI -1.2 (-2.0 to -0.4)] or during [CI -15.2 (-29.1 to -1.3)] key training sessions. CHO recommendations were more difficult to fulfill during hard compared to light training days (p=0.014).

Conclusion Female endurance athletes with symptoms of RED-S have difficulties matching CHO intake in relation to training load according to the recommendations. Hence, to prevent RED-S focus on optimizing CHO intake is needed.