D02 Novel associations between within-day energy balance (WDEB) and relative energy deficiency in sport (RED-S) in recreationally active women

Abstract

Relative energy deficiency in sport (RED-S) is a syndrome whereby physiological process are downregulated to regain energy balance under conditions of low energy availability (LEA). There is a growing body of research investigating the diverse health and performance complications in relation to energy availability calculated over 24-h. However this may conceal energy deficient periods in the day, which could contribute to RED-S symptoms. There is a handful of research suggesting such periods of deficiency are associated with changes in body composition, and menstrual and endocrine dysfunction, however many RED-S symptoms are yet to be explored in this area. This study therefore aimed to explore within-day energy balance (WDEB) in relation to a variety of, yet to be investigated, RED-S consequences in recreationally active women. Following ethical approval from the Manchester Metropolitan University Ethics Committee, 16 women (age, 27 ± 6 years, stature, 1.67 ± 0.05 m, and mass, 63.5 ± 8.2 kg) engaging in 4-6-h per week moderate-vigorous physical activity were recruited via social media, word of mouth, and posters. Seven-day food and training diaries alongside accelerometery and heart rate were used to estimate 24-h energy availability and hourly WDEB. The largest within-day energy surplus and deficit, the number of hours spent in a surplus and deficit, and the maximum number of consecutive hours in each, were calculated daily and averaged across the 7-days. Quantitative ultrasound of bone, haematocrit, haemoglobin, total cholesterol, maximum voluntary contraction of the knee during flexion and extension, V̇O₂peak and lactate profile were all assessed. Gastrointestinal health was assessed via questionnaire. Correlational analysis between WDEB variables and RED-S symptoms was done accounting for 24-h energy availability. Of all 16 participants, 87.5% did not have adequate energy availability (<45 kcal∙kgFFM∙day^-1); 12.5% had low energy availability (<30 kcal∙kgFFM∙day^-1), and 75% had subclinical energy availability (30-45 kcal∙kgFFM∙day^-1), typically associated with weight loss. Gastrointestinal dysfunction was negatively correlated with within-day energy surpluses (r₁₃ = −0.479, P = 0.035) and positively correlated with within-day energy deficit variables (r₁₃ = 0.499 to 0.534, P ≤ 0.029). These correlations were maintained after also accounting for anxiety. Haemoglobin levels were negatively correlated with within-day energy deficit variables (r₁₃ = −0.477 to −0.490, P ≤ 0.036). Radius and tibia, T- and Z-scores were positively correlated with energy surplus values (r₁₃ = 0.593 & 0.681, P = 0.004 & 0.013, respectively). To conclude, this was the first study to show WDEB to be associated with gastrointestinal, haematological, and bone health, illustrating that WDEB in relation to RED-S warrants further research as it may have health and performance implications that are overlooked when assessing LEA alone.