Dietary Intake of Endurance Athletes During 12 Weeks of Self-Selected Training: An Observational Study

It is recommended that endurance athletes modulate their daily carbohydrate intake according to the demands of training, but there is limited evidence of how this is currently practiced by athletes during real-world, day-to-day training. The purpose of this observational study was to report the dietary intake of endurance athletes across a 12-week period with an emphasis on the relationship between training load and carbohydrate intake. Self-selected training and dietary intake were self-reported using a smartphone app by 46 endurance athletes (61% male) daily for 12 weeks, representing a total of 3,718 days of dietary assessments and 3,160 days of training. Fasted-state training was regularly performed by 65% of athletes and was more common in men (33.6% vs. 17.2% of training days, p = .023). Average daily carbohydrate intake for each athlete ranged from 1.2 to 7.2 g/kg (M = 3.9 ± 1.5). At the group level, significant correlations were found between mean daily carbohydrate intake and both percentage of training sessions performed in the fasted state (r = -.39, p = .008) and weekly training volume (r = .42, p = .004). Participant-level correlations between daily training load and carbohydrate intake ranged from -.42 to .83. Overall, athletes adjust daily carbohydrate intake based on exercise duration, but at the individual level, many athletes do not align carbohydrate intake with training load as recommended or do so with minimal adjustment.