Triathlon nutrition research shows wide variation in what athletes consume before and during racing. Across studies from 2001 to 2024, carbohydrate intake often fell short of cited targets, fluid and sodium intake varied by event and discipline, and substantial energy deficits were recorded in ultra-endurance competition.
Contents
- Pre-race carbohydrate intake
- Carbohydrate intake during racing
- Fluid intake and hydration
- Sodium and electrolytes
- Energy balance and macronutrients
- Performance and gastrointestinal outcomes
Pre-race carbohydrate intake
A 2024 competition sample of 50 endurance athletes competing for at least 2.5 hours found that mean carbohydrate intake during the 24 hours before competition was 6.5 ± 2.2 g/kg. That was below the 10–12 g/kg loading guideline cited in the study. Intake ranged from 2.9 to 11.9 g/kg, while absolute carbohydrate intake ranged from 185 to 678 g. The mean absolute amount was 395 ± 134 g.
Only 5 of the 50 athletes, or 10%, reached 10–12 g/kg in the 24-hour period. The sample therefore provides a useful picture of the gap between a commonly cited loading target and reported practice. These figures describe the 2024 competition sample; they are not a prevalence estimate for all triathletes.
Professional athletes consumed 439 ± 122 g of pre-race carbohydrate, compared with 334 ± 130 g among amateurs. Relative intake averaged 7.2 ± 2.0 g/kg for professionals and 5.6 ± 2.0 g/kg for amateurs. By sex, male athletes reported 457 ± 143 g and female athletes 373 ± 126 g. Relative intake was 6.4 ± 2.2 g/kg for males and 6.5 ± 2.2 g/kg for females.
The pre-event meal supplied 91 ± 37 g of carbohydrate, equivalent to 1.5 ± 0.6 g/kg. Forty of the 50 athletes, or 80%, met the study’s 1–4 g/kg pre-event meal guideline. The same study reported the following measurements in its 2024 sample:
| Measure | Result |
|---|---|
| Mean 24-hour carbohydrate intake | 6.5 ± 2.2 g/kg |
| Athletes reaching 10–12 g/kg | 5 of 50 (10%) |
| Mean absolute carbohydrate intake | 395 ± 134 g |
| Mean pre-event meal carbohydrate | 1.5 ± 0.6 g/kg |
| Athletes meeting the meal guideline | 40 of 50 (80%) |
Source: A broken link: Knowledge of carbohydrate requirements do not predict carbohydrate intake around competition in endurance athletes (2024 competition sample). The source title and study findings are retained as reported; the older or study-specific observations should not be treated as independently verified beyond that report.
Carbohydrate intake during racing
Race-day carbohydrate intake differed sharply by event and study population. In 11 male ultra-endurance triathletes during a 2014 ultra-endurance triathlon race, total carbohydrate intake averaged 926.6 ± 177.5 g, or 6.2 ± 1.3 g/kg. The average intake rate was 84 ± 18 g/h, and carbohydrate supplied 89.9% ± 3.5% of race energy intake.
Solid carbohydrate supplied 697.2 ± 147.2 g in that race, compared with 229.4 ± 67.0 g from carbohydrate-containing fluids. Cycling contributed 583.5 ± 176.3 g and running 349.0 ± 73.3 g. Intake rates were 84 ± 30 g/h during cycling and 78 ± 18 g/h during running. Carbohydrate contributed 83.2% ± 5.6% of cycling-stage energy and 96.6% ± 3.8% of running-stage energy.
The 2024 sample of 50 endurance athletes reported a much lower mean in-competition intake of 289 ± 226 g total, equivalent to 52 ± 21 g/h. Eighteen athletes, or 36%, reached the study’s 60–90 g/h guideline. Reported intake ranged from 0 to 154 g/h. These results come from a different sample and should not be directly combined with the ultra-endurance race totals.
An older Ironman study of 59 athletes reported carbohydrate intake of 0.96 ± 0.40 g/kg/h during the 2001 Ironman triathlon. Finish time correlated −0.59 with carbohydrate intake in g/kg/h, with a reported likely range of −0.74 to −0.39. When modeled separately, a 0.40 g/kg/h increase in carbohydrate intake was associated with a 6.0% reduction in predicted finish time. This is an association from the 2001 study, not proof that changing intake alone produces the modeled result.
Source: Energy Balance of Triathletes during an Ultra-Endurance Event (2014 ultra-endurance triathlon race); A broken link: Knowledge of carbohydrate requirements do not predict carbohydrate intake around competition in endurance athletes (2024 competition sample); Nutritional Intake Predicts Performance in an Ironman Triathlon (2001 Ironman triathlon).
Fluid intake and hydration
The 2014 ultra-endurance study recorded 4,188.2 ± 1,836.9 mL of total race fluid intake among its 11 triathletes. Mean fluid intake was 366.6 ± 146.9 mL/h. Cycling accounted for 2,530.9 ± 1,255.9 mL and running for 1,657.3 ± 717.4 mL. Intake rates were 361.6 ± 171.8 mL/h during cycling and 394.5 ± 183.2 mL/h during running.
Among 32 triathletes in the 2022 Vi Half Gasteiz triathlon, mean fluid intake was 422.40 ± 175.51 mL/h. The study reported that this was below its cited 450–750 mL/h ultra-distance reference range. Because the event was middle-distance, the comparison is a study-specific reference rather than a universal requirement.
A 2012 Ironman field study of 15 male triathletes recorded 8.6 ± 4.4 L of fluid during the race, averaging 0.79 ± 0.43 L/h. The 59-athlete 2001 Ironman study reported water intake of 12 ± 5 mL/kg/h. In that study, finish time correlated −0.45 with water intake in mL/kg/h, with a reported likely range of −0.63 to −0.22.
Hydration outcomes also vary by analysis. A meta-analysis of six full-Ironman hydration studies found a pooled post-race dehydration effect of SMD 0.494, with a 95% confidence interval of 0.220–0.767 and p = 0.001. The analysis included studies available through June 2016, so its scope does not represent later research.
Sources: Energy Balance of Triathletes during an Ultra-Endurance Event; [Are the Dietary–Nutritional Recommendations Met? Analysis of Intake in Endurance Competitions](https://www.mdpi.com/2072- nutrition-3.4.1/16/2/189); ad libitum fluid intake leads to no leg swelling in male Ironman triathletes – an observational field study; Nutritional Intake Predicts Performance in an Ironman Triathlon; Hydration Status After an Ironman Triathlon: A Meta-Analysis.
Sodium and electrolytes
Total sodium intake in the 11-triathlete 2014 ultra-endurance study was 2,152.2 ± 1,124.2 mg. Sodium from fluids averaged 485.2 ± 307.5 mg during cycling and 232.0 ± 208.5 mg during running. Sodium from food averaged 1,135.9 ± 953.9 mg during cycling and 299.1 ± 369.3 mg during running.
The 32-triathlete 2022 Vi Half Gasteiz sample consumed 269.95 ± 188.26 mg of sodium per hour. The study reported that this was below its cited 300–600 mg/h ACSM reference range. Again, this comparison reflects the study’s selected reference range and the measured middle-distance sample.
In the 15-athlete 2012 Ironman field study, total sodium intake was 4.1 ± 1.6 g, averaging 378 ± 151 mg/h. The same sample consumed 3.7 ± 4.1 g of potassium, or 330 ± 220 mg/h. The large spread shown by the standard deviations indicates substantial individual variation in electrolyte intake.
Energy balance and macronutrients
The 2014 ultra-endurance study estimated energy expenditure at 11,009 ± 664 kcal. Mean race energy intake was 3,643 ± 1,219 kcal, producing an estimated energy deficit of 7,365 ± 1,286 kcal, or 66.9% ± 11.7%. Solid food supplied 2,812 ± 1,150 kcal, while fluids supplied 831 ± 668 kcal. Cycling accounted for 65.63% of race energy intake and running for 34.4%.
Race protein intake in that study averaged 45.4 ± 12.0 g, equal to 0.3 ± 0.1 g/kg and 3.8% ± 1.6% of energy intake. Fat intake averaged 76.8 ± 20.4 g, or 0.5 ± 0.1 g/kg and 6.3% ± 2.4% of energy intake. These values describe intake during the race and should not be interpreted as an athlete’s full-day macronutrient pattern.
Body mass fell 5.7% ± 1.9% after the ultra-endurance race. Total body water fell 8.4% ± 2.9%, extracellular water 10.8% ± 3.7%, and intracellular water 6.8% ± 2.9%.
The 2001 Ironman study reported event-energy composition of 94% ± 7% from carbohydrate, 3% ± 5% from fat, and 2% ± 3% from protein. Those percentages come from that study’s race intake report and are not a general macronutrient prescription.
Performance and gastrointestinal outcomes
In the 2014 ultra-endurance study, carbohydrate intake in g/min correlated −0.71 with cycling time and 0.70 with cycling speed. Carbohydrate intake and extracellular-water loss together explained 60% of final race-time variance, reported as R² = 0.60. These are relationships within the study and do not establish that nutrition alone determined performance.
The 2022 middle-distance sample illustrates the practical limits athletes may encounter while racing. Gastrointestinal discomfort was reported in 61.9% of cases. Mean energy intake was 192.17 kcal/h, mean carbohydrate intake was 43.67 g/h, and mean caffeine intake was 15.53 mg/h.
Race duration and intake were also documented in a 2015 half-Ironman study of 15 athletes. Mean race duration was 320 ± 37 minutes: 42.1 ± 8.3 minutes swimming, 158 ± 16 minutes cycling, and 112 ± 18 minutes running. Athletes ingested 1,730 ± 546 mL of fluid and 832 ± 355 kcal. Their race intake included 192 ± 82 g carbohydrate, 1.8 ± 0.9 g fat, and 0.1 ± 0.1 g protein.
Body mass in that half-Ironman sample declined from 74.1 ± 7.5 kg before racing to 71.8 ± 7.1 kg afterward, a change of −3.1% ± 1.2%. In the 15-athlete 2012 Ironman field study, finish times averaged 669.1 ± 79.0 minutes.
Sources: Energy Balance of Triathletes during an Ultra-Endurance Event; Are the Dietary–Nutritional Recommendations Met? Analysis of Intake in Endurance Competitions; Changes in Serum Free Amino Acids and Muscle Fatigue Experienced during a Half-Ironman Triathlon; ad libitum fluid intake leads to no leg swelling in male Ironman triathletes – an observational field study.