Train your gut: how to practise race-day fuelling

Your stomach is trainable. The long runs that build your legs can also teach your gut to absorb more carbohydrate and fluid at race effort, which is why most race-day bloating traces back to a plan that was never rehearsed, not to the gel itself. This guide sets out a 6–8 week progression, shows how to practise at race pace, pairs each gel with water, and lists what to log so the plan improves every week.

Why the gut needs training

Absorbing carbohydrate on the move is a skill, and the gut adapts to what it is regularly asked to do. Give it 60 g an hour at marathon pace a few times and it gets quicker at moving that sugar from stomach to blood. Ask for it for the first time on race morning and it objects. Marathon guidance is 60–90 g of carbohydrate an hour, taken every 20–30 minutes, and the only comfortable route there is to build up in training.

Start 6–8 weeks before race day

If you are new to fuelling, or your target is a step up from what you take now, start gut training at least 6–8 weeks out. Long runs are the sessions that matter: they expose the gut to several gels in a row and include stretches near race effort. Easy or recovery runs under 60 minutes do not need in-run fuel if you have eaten earlier in the day; take 20–30 g of carbohydrate, one gel, 5–15 minutes before you start and save the higher targets for the sessions where rehearsal counts. Set your own target with the fuel calculator first, so you know where the progression is heading.

A weekly progression

Progression matters more than perfection. If the target feels high, start at what feels manageable and add roughly 10 g an hour each week. Here is the worked example for a runner on 30 g an hour with a target of 75 g. An Original Energy Gel carries 21–23 g of carbohydrate; a Liquid Energy Gel carries 24 g.

Week	Target	Gel schedule on the long run	Roughly delivers
1	30 g/h	One gel every 40 minutes	32–35 g/h
2	40 g/h	One gel every 30 minutes	42–46 g/h
3	50 g/h	One gel every 25 minutes	50–55 g/h
4	60 g/h	One gel every 20 minutes	63–69 g/h
5	70 g/h	One Liquid Energy Gel every 20 minutes	72 g/h
6	75 g/h	Liquid Energy Gel every 20 minutes plus a mouthful of carbohydrate drink between gels	75 g/h
7–8	Hold	Repeat the target schedule on the last two long runs, at race pace	75 g/h

Three rules govern the jumps:

• Symptoms mean hold, not quit. If you get bloating, fullness or nausea, stay at the same intake for another week, or keep the grams and vary the source: alternate Original with Liquid Energy Gel, or move some carbohydrate into a drink.
• Persistent symptoms mean step back. If a second week at the same level still causes trouble, drop to the previous step and reassess.
• Fine-tune in 5 g steps. Close to the target, jumps of about 5 g an hour on long runs find the exact level your gut accepts.

Keep the empty packets in a pocket and count them at home. "Three gels in two hours" is the plan; the wrappers say what happened, and the gap between the two belongs in your log.

Practise at race pace

A stomach that is happy at easy pace is not necessarily happy at marathon pace. Harder running sends more blood to the legs and less to the gut, so a gel that went down fine on a Sunday jog can sit like a stone at threshold. Take some of each long run's gels during the race-pace segments.

• Take the first gel on schedule, not on hunger. Waiting until you feel flat means you are already behind. Set a watch alert for every 20–30 minutes and follow it.
• Use the gel you will race on. Same flavour, caffeine and format. If your race runs beyond 90 minutes or 16 km, that usually means Roctane Energy Gel, with its extra electrolytes and amino acids, so practise with it rather than switching on race day.
• Practise the handling. Opening a packet with sweaty hands at 4:30 per km is its own skill, and so is carrying six of them.
• Rehearse race morning once. Your usual pre-long-run meal, with time to digest and no fibre or protein close to the start, tried before a key long run rather than for the first time in race week.

Pair every gel with water

Carbohydrate is absorbed best with fluid alongside it, so whenever you take a gel, drink. A gel on a dry stomach sits heavier. Starting dehydrated also raises the risk of GI distress and undermines the fuelling you are practising, so hydration begins before the first step.

When	How much	Why it matters for gut training
Through the day	Sip fluids with light electrolytes	Arrive at the session topped up
1–2 hours before	200–350 ml (7–12 oz)	Lowers the chance of GI trouble; adjust for body size, sweat rate and weather
With each gel	A few good sips	Helps the carbohydrate leave the stomach
Per hour, beyond 60 minutes	450–900 ml (16–30 oz), with electrolytes	Sip every 10–15 minutes; a sloshing stomach means you are over the range
After	Carbohydrate, protein and electrolytes within 30 minutes, then keep drinking	Tomorrow's session starts hydrated

Practise with the water set-up the race will give you. If that is aid stations, learn where they fall from the course notes, time gels to land just before a water point, and rehearse the gel-then-cup sequence at pace. If you carry a bottle, train with it.

Heat changes the equation. A humid pre-dawn start in Mumbai or Chennai, or a 32 °C long run in Hyderabad, pushes sweat losses up and makes the gut less tolerant of everything. Do some gut-training runs in the conditions you expect on race day, drink towards the top of the range, and expect to sit a step lower on the ladder until you adapt.

What to log

Gut training only works if you can compare weeks, and memory is unreliable about how a long run felt once the shower is done. Six lines per session in a phone note is enough:

1. The session: distance, duration, and how much was at race pace.
2. The fuel: target grams an hour, the planned schedule, and what the wrapper count says you actually took, with flavour and caffeine.
3. The fluid: millilitres an hour, water or electrolytes, before and during.
4. Conditions: temperature, humidity and start time.
5. Gut score: 0 for nothing, 1 for mild fullness, 2 for bloating or nausea that affected pace, 3 for having to stop.
6. Energy in the last 30 minutes: steady, fading or flat.

Then apply the rules: advance a step only if the week's long run scored 0 or 1, and step back after two sessions at 2 in a row. Over a few weeks the log also shows what the table cannot predict, such as a day when 40 g felt like 70 because you started dehydrated.

Race week: nothing new

By race week the experiment is over. Run the plan the log says works: the same gels, interval and water. Carbohydrate-load for the 2–3 days before at 8–10 g per kg of body weight, cutting fat and fibre, eat your usual pre-long-run meal with time to digest, and start hydrated. If the weather forces a change, change the drink, not the gel schedule.

FAQ

How long does it take to train the gut?

Allow at least 6–8 weeks. Each long run buys a little more tolerance, but a 30 g to 75 g jump needs the full window plus a week or two at the target.

I feel sick on gels. Should I push through?

No. Hold at the current intake for another week, or keep the grams and change the source. If symptoms persist, step back one level. Persistent nausea is information, not a test of character.

Should I practise with the exact gel I will race on?

Yes. Flavour, caffeine and format all affect how a gel sits over three or four hours. If your race is longer than 90 minutes or 16 km, that is usually Roctane Energy Gel, so make it your long-run gel from the start of the block. Roctane vs Original explains the differences.

Next steps

• Set your carbohydrate and fluid targets with the fuel calculator, then start the ladder.
• Turn the practised plan into a race plan: marathon gel strategy.
• Match fuel to the week's workload with fuelling for training load.

These statements have not been evaluated by a regulatory authority. This product is not intended to diagnose, treat, cure or prevent any disease.