ECSS Paris 2023: CP-PN08
INTRODUCTION: Relative Energy Deficiency in Sport (RED-S) represents a critical risk for endurance athletes, particularly during intensive stage racing. High training demands and limited opportunities for adequate energy intake may create an energy imbalance. This study investigated whether elite female cyclists experience an energy deficit during a Grand Tour (GT) and examined how energy availability relates to their dietary strategies and physiological adaptations. METHODS: Ten elite female cyclists (26.4±4.0 years, BMI 20.3±0.8 kg/m², FTP 4.9±0.4 W/kg) from a World Tour team participated in this quasi-experimental study. Dietary intake, training and racing data were collected before (PRE) and during the Giro Donne (n=3) or Tour de France Femmes (n=7). Energy expenditure was calculated from training data and basal metabolic rate (mean 1325.6±49.9 kcal/day). PRE–POST differences were analysed using linear mixed-effects models. RESULTS: During the GT, Training Stress Score was significantly higher (236.8±40.7 vs 91.3±21.6, p<0.001), raising active energy expenditure to 2755.4±706.6 kcal/day (mean-diff 1532.5, p<0.001) and total daily energy expenditure to 4687.4±653.9 kcal/day. Although cyclists substantially increased energy intake to 4211.0±747.8 kcal/day (mean-diff 1287.8, p<0.001), primarily through increased sugar (512.3±89.6 vs 259.6±35.6 g, p<0.001) and starch (219.1±43.4 vs 171.3±35.3 g, p=0.009), this did not compensate for total expenditure (p<0.001), leaving a systematic energy deficit of on average 476.4±440.2 kcal/day. Protein (151.1±15.8 vs 144.0±24.8 g, p=0.347) and fibre (30.0±4.8 vs 31.6±5.9 g, p=0.508) remained stable, whereas fat intake decreased (64.1±3.2 vs 57.0±5.7 g, p=0.001). CONCLUSION: Elite female cyclists adopt a high-carbohydrate dietary strategy during Grand Tours but experience a persistent energy deficit of on average 476 kcal/day despite maximising practical energy intake. This mismatch between energy expenditure and intake reflects a state of relative energy deficiency that may increase susceptibility to fatigue, impaired recovery, immunosuppression and long-term health consequences. These findings highlight the practical challenges of meeting energy demands during stage racing and support the need for individualised strategies, including optimised pre- and post-stage nutrition, to minimise RED-S risk. Future research should explore whether this energy gap correlates with performance outcomes, hormonal markers of RED-S or recovery metrics during a GT.
Read CV Malin LeysenECSS Paris 2023: CP-PN08
INTRODUCTION: Ramadan fasting, observed annually by close to 2 billion Muslims worldwide, requires abstinence from eating and drinking from dawn to sunset for a whole lunar month. This form of religious diurnal intermittent dry fasting creates distinct metabolic and physiological challenges, particularly regarding fluid homeostasis. While physical activity during Ramadan has been studied, relationships between objectively measured daily activity and homeostatic regulation of hunger, thirst, and hydration remain inadequately characterized. METHODS: In the spring of 2021–2023 (March-May), 287 Ramadan-observing Muslim participants and 76 culturally and ethnically matched controls residing in Israel participated in the study (mean age 26±7 years, 59% female). At five time points (one week pre-Ramadan, Ramadan weeks 1 and 4, and weeks 1 and 4 post-Ramadan), the participants reported physical activity frequency (no. of 30-min. sessions per week). A subset of 230 participants (63.4%) using wearable devices reported average daily step counts (mean 10,450±5,481 steps/day; range 1,000-25,000). Mixed linear models examined associations between both activity measures and hunger, thirst, absolute hydration (L/day), relative hydration (mL/kg/day), and appetite timing, adjusting for age, gender, and BMI. RESULTS: Self-reported activity showed no associations with homeostatic outcomes in Muslims but predicted higher hydration in controls (absolute: F=6.63, p=0.011; relative: F=4.87, p=0.029). Objectively measured step counts predicted hydration in both Muslims (relative: F=16.69, p<0.001; absolute: F=16.97, p<0.001) and controls (p<0.05), with each additional 1,000 steps associated with ~1.4% higher relative hydration in Muslims. Step counts showed no consistent associations with hunger, thirst, or appetite timing. An exception emerged at Ramadan week 1, where Ramadan-observing Muslims with higher step counts reported lower hunger (p=0.028). In the controls, higher self-reported physical activity was associated with higher hunger at Ramadan week 4 (p=0.035). CONCLUSION: Objective activity measurement revealed selective homeostatic associations during Ramadan. Daily step counts consistently predicted fluid regulation in both groups yet showed minimal association with subjective sensations (hunger, thirst, appetite timing). This dissociation suggests physical activity influences fluid and appetite homeostasis through distinct regulatory pathways, prioritizing fluid balance maintenance during fasting. An exception occurred during early fasting adaptation (week 1), when Muslims with higher step counts reported lower hunger (p=0.028), a fasting-specific pattern not observed in controls, who showed higher hunger with increased self-reported physical activity at week 4 (p=0.035). The failure of self-reported activity to capture step-count effects underscores the need for objective behavioural measurement in Ramadan research.
Read CV Chen FleischmannECSS Paris 2023: CP-PN08