Under Consumed and Overestimated: Discrepancies in Race-Day Carbohydrate Intake Among Endurance Athletes

Despite well-established guidelines for carbohydrate (CHO) intake to support endurance performance, many athletes fail to meet these targets, and in-race intake is often estimated based on planned consumption rather than measured intake. We aimed to quantify actual CHO intake during endurance races and explore behavioral and psychological predictors. Sixty Tier 2 endurance athletes (38 marathoners and 22 cyclists) participated in two official races. Athletes' planned, perceived, and actual CHO intake 24 h before and during the race were assessed using food diary analysis, and pre- and post-race weighing of sports products containing CHO. Sleep behavior (ASBQ), pre-race anxiety (CSAI-2R), and gastrointestinal symptoms were also evaluated using validated questionnaires. Across the cohort, actual CHO intake (31.7 ± 23.5 g/hr) was lower than planned (38.0 ± 27.3 g/hr; p < 0.001). The absolute planned-actual gap was larger in cyclists (58.9 → 49.1 g/hr; Δ = 10.3 g/hr) than in marathoners (25.9 → 21.7 g/hr; Δ = 4.2 g/hr); proportionally, the shortfall was similar (∼16%-17%) in both groups. Cyclists planned substantially higher CHO intakes and achieved higher actual intakes than marathoners. Regression analysis showed that race type, better sleep behavior, and lower cognitive anxiety predicted higher actual intake (R² = 0.41, p < 0.05). Despite similar intentions, marathoners consumed less CHO than cyclists and overestimated their CHO intake, highlighting behavioral gaps. Sleep and psychological readiness played key roles in fueling success. Findings support the importance of measuring actual intake and considering individual behavioral factors to optimize endurance nutrition strategies.