Ad Libitum Diet, Energy Availability, Body Composition And Performance In Females During A 6-day Ultramarathon

Ultramarathons (i.e., running >42.2 km) result in extremely high, acute, exercise energy expenditures (EEE). Adequate energy intake (EI) for optimal energy availability (EA) is vital for health and performance and is understudied in ultramarathon races. Understanding relationships between EI and EA with physiological and performance outcomes is critical for developing targeted nutrition strategies to optimize health and performance in female ultra-runners. PURPOSE: Characterize dietary intake and examine the relationships between EI and EA with body composition and total distance covered among females during a first-of-its-kind 6-day ultramarathon, producing several world records. METHODS: Professional and amateur female athletes consumed food and fluids ad libitum during a 6-day ultramarathon. Athlete dietary intake was recorded by nutrition experts and athlete support crews using gold-standard methods of weighing foods and beverages before and after consumption. EI and macronutrient intake were assessed via ESHA Food Processor Software. Fat mass index (FMI, kg/m2) and fat-free mass index (FFMI, kg/m2) was assessed via dual X-ray absorptiometry. Resting metabolic rate was assessed via indirect calorimetry. EA was calculated as EI-EEE/fat-free mass, where EEE was estimated as 1 kcal/kg/km ran, as established by Margaria et al. (JAP 1963). RESULTS: 4 professional and 6 amateur ultramarathoners participated (mean age: 38 ± 7 yrs; body mass index range: 18.8-48.3 kg/m2; FMI range: 2.0-22.1 kg/m2; FFMI range: 15.4-24.4 kg/m2). Distances covered over 6 days ranged from 181-902 km (464 ± 210 km). Mean EI ranged from 2915 to 6856 kcal/d (4188 ± 1169 kcal/d) with EA ranging from -19.1 to +48.9 kcal/kg/d (-3.2 ± 20.1 kcal/kg/d). 51 ± 12% of EI consisted of carbohydrates followed by fat (34 ± 9%) and protein (15 ± 4%). EI correlated with total distance covered (r = 0.766, p = 0.01), but not FFMI (r = 0.006, p = 0.987) or FMI (r = -0.248, p = 0.489). EA did not relate to total distance covered (r = -0.116, p = 0.751), FFMI (r = -0.006, p = 0.987) or FMI (r = -0.079, p = 0.829). CONCLUSIONS: EI - but not EA - was positively related to total distance covered; neither EI nor EA were related to body composition over a 6-day ultra. These findings highlight the importance of sufficient EI for supporting female ultramarathoners. Supported by: Part of the data presented was collected through a study supported by the MITACS (Mathematics of Information Technology and Complex Systems) Accelerate Program and funded by lululemon athletica inc.