How to eat on a 5-hour ride without wrecking your stomach

A five-hour ride asks two things of you at once, and they pull in opposite directions. You need a great deal of fuel — several hundred grams of carbohydrate — and you need a gut that will still cooperate at hour four. Ask too much of the second and you lose the first, usually somewhere on a climb, memorably.

Gastrointestinal problems are not a fringe issue in endurance sport. Depending on the study and the event, somewhere between a third and two-thirds of endurance athletes report symptoms, and they are one of the more common reasons people abandon long events. The encouraging part is that most of it is predictable and largely preventable — it is a fuelling strategy problem far more often than it is a medical one.

Why it happens

Exercise-induced gut trouble is usually several mechanisms stacking rather than one cause. Understanding which ones apply to you is most of the fix.

How much carbohydrate, and in what form

The general guidance for rides of this length is around 60–90 g of carbohydrate per hour. The top of that range is only reachable with a mix of glucose and fructose, because glucose alone saturates its intestinal transporter at roughly 60 g/h. Combining the two uses a second transport route and lets total absorption go higher — which is why almost every modern product lists a glucose-to-fructose ratio somewhere on the packet.

Two honest caveats. First, 90 g/h is an upper figure for well-trained riders who have practised it, not a target for a first long ride; going straight there is one of the more reliable ways to make yourself ill. Second, the optimal intake genuinely varies between individuals, and a rider who thrives on 60 g/h is not doing it wrong.

Bottle concentration, which almost nobody checks

This is the most common self-inflicted error on long rides: mixing bottles strong so you carry fewer of them. Gastric emptying slows as carbohydrate concentration rises, and a strongly hypertonic drink can draw water into the intestine instead of contributing to hydration.

Approximate bands. Osmolality depends on the type of carbohydrate as well as the amount — maltodextrin contributes far less osmotic load per gram than glucose, which is exactly why it is in almost every drink mix.

The practical rule: use bottles for fluid and a base level of carbohydrate, and get the rest from food and gels taken with water. If you need 80 g in an hour, two-thirds of a bottle plus a bar is a much gentler way to get there than one very strong bottle.

An hour-by-hour shape

The fix list

• Train the gut. Tolerance for carbohydrate during exercise is adaptable — the intestinal transporters respond to being asked. Practise your race-day intake on long training rides for several weeks beforehand rather than discovering it on the day.
• Never trial anything new on a big ride. Not a gel flavour, not a new drink mix, not the branded product in the event goody bag.
• Go low-fibre for 24 hours before. Fibre is excellent nutrition and a poor pre-ride companion. This is a temporary tactic for one day, not a way to eat.
• Watch the fat. Fat slows gastric emptying more than anything else on the plate. A rich dinner the night before is felt at hour four.
• Drink to a schedule from the start. Once you are behind on fluid, absorption is already compromised and catching up is hard.
• Separate feeds from efforts. Eat on the flat and the descents. Above threshold, your gut has effectively been switched off.
• Consider a short low-FODMAP trial if you have ruled out the simpler causes. There is preliminary evidence that reducing fermentable carbohydrates in the days before exercise reduces symptoms in athletes prone to them — but the evidence is early, the diet is restrictive, and it is worth doing with a dietitian rather than from a web article.
• Be cautious with anti-inflammatories. Taking ibuprofen before or during long rides is common and is associated with increased intestinal injury. It is not a preventative.

Keeping a record

Gut problems feel random, and they usually are not. They correlate with intensity, heat, feed timing and what you ate the night before — but you will not spot the pattern from memory, because the rides that go badly are the ones you most want to forget. Write down what you took in, when, and how you felt, for a dozen long rides, and the culprit tends to identify itself.

It helps to know in advance how hard a ride is going to be, because intensity is the strongest predictor of trouble. If you are using Moveee, the Route Engine gives you the elevation profile and where the sustained climbs sit before you leave — which is really a feeding plan in disguise, since it tells you where the last comfortable place to eat is.

None of this is glamorous. But the rider who finishes a five-hour day still eating is, more often than not, the one who planned the first hour properly rather than the one with the strongest legs.