Only about a quarter of women at the IRONMAN Worlds hit carb loading targets

Why they ran it

Preparing for an endurance competition involves psychological, logistical and sociocultural factors, and the authors write that these are rarely captured by studies that only measure what athletes ate.

They set out to investigate the pre race nutrition practices of female endurance athletes using an extended behavioural framework that adds behavioural execution to intention, so that the gap between what an athlete plans and what an athlete actually does could be described rather than assumed.

Drawn from the paper's abstract and stated aims.

Twenty seven female triathletes at the 2024 IRONMAN World Championships completed questionnaires, kept 48 hour food diaries, and sat for semi structured interviews before and after the race. Dietary analysis was possible for 23 of them.

Only 26 percent, 6 of 23, reached the 8 to 12 grams per kilogram of body mass per day carbohydrate loading guideline. Mean intake across the group was 6.4 grams per kilogram.

Higher carbohydrate intake correlated with faster finish times, r equals minus 0.50. Fibre intake was strongly associated with the severity of gastrointestinal symptoms, r equals 0.85.

The interviews found that adherence was shaped by perceived behavioural control, travel logistics, emotional regulation and athlete identity. The authors write that athletes often under achieve carbohydrate loading targets despite awareness of them.

The numbers

Met the 8 to 12 g/kg carbohydrate loading guideline	6 of 23, 26%
Mean carbohydrate intake	6.4 +/- 2.1 g/kg body mass
Carbohydrate intake vs finish time	r=-0.50, p=0.035
Fibre intake vs GI symptom severity	r=0.85, p<0.001
Athletes interviewed	27, before and after the race

Why this might happen

Shown in this study The study measured this step directly.

This is the rare study in this issue that measured the mechanism directly, because the mechanism is behavioural and the authors interviewed people about it.

What separated intention from execution was perceived behavioural control, travel logistics, emotional regulation and athlete identity around eating. Knowledge was not the missing piece. The athletes largely knew the targets and did not reach them.

Drawn from the paper's qualitative arm.

What this does not show

It does not show that carbohydrate caused the faster finishes. This is a correlation across 23 athletes at one event. Faster athletes may simply tolerate more carbohydrate, or be better resourced, or both. The arrow could point either way.
It does not show that fibre causes gut distress in general. The association covers fibre eaten in the 48 hours before an IRONMAN. It says nothing about habitual fibre intake outside race week, and the two are different questions.
Twenty three athletes at one championship. The quantitative arm is small and drawn from a single event with an unusually selected field. The findings are directional.
No intervention was tested. The study identifies barriers and names them carefully. It did not try to remove any of them, so whether addressing them would change intake is untested here.

Where this leaves us

The gap between the loading protocol on paper and the loading protocol in a hotel room the night before a race is large, and it is not made of ignorance. In this field the average intake was closer to a normal athletic day than to a loading day, which puts the shortfall on the one variable the meta analysis says predicts the glycogen overshoot.

Twenty seven female triathletes at one IRONMAN World Championship, twenty three of them with usable diet records.

A trial that removes the named barriers, by controlling food access and planning, and then measures whether intake moves. The authors identify what is in the way; nobody has yet tried moving it.

Caveats worth holding

Correlational throughout. Causation cannot be inferred in either direction.
Twenty three athletes for the quantitative arm, at a single championship event with a highly selected field.
Food diaries are self reported and under reporting is common, so the true intakes may differ from the recorded ones in either direction.
The fibre and gastrointestinal symptom finding is specific to the 48 hours before an IRONMAN and should not be read as a general statement about fibre.