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Gut training means practising the food and drink you intend to use while running, before the event. Start with a manageable rehearsal, record what happened and repeat before changing the plan. The aim is a fuelling routine you can tolerate and carry out, not the highest carbohydrate number you can endure.
Choose the race problem you want to solve
A runner who forgets to eat has a different problem from a runner who feels sick after every gel. Write down the failure you are trying to prevent: missing feeds, difficulty opening packets, nausea, an overly sweet drink or not enough water access.
Choose a likely race format before buying several options. Will you carry a bottle, use a vest or rely on aid stations? What is actually available on course? Rehearsal works best when the practical setup resembles the event rather than a perfectly stocked treadmill session.
Our guide to carbohydrate during training covers the wider intake discussion. This article is about testing a chosen plan. You do not need to copy an elite runner's hourly target to start practising.
What the research shows, and what it does not
In a small randomised study, 25 endurance runners completed a demanding running and feeding test, then two weeks of repeated gut-challenge training. The carbohydrate-training groups reported improved gastrointestinal tolerance at the repeat test compared with their earlier test, with improvements greater than placebo. See Costa and colleagues: two-week gut-training trial.
That is evidence that tolerance can change. It is not proof that every runner needs the study intake, will adapt within exactly two weeks or should run through significant symptoms. The participants, feeding pattern and exercise challenge were specific.
The SDA and Ultra Sports Science Foundation gastrointestinal position statement considers several contributors to exercise-related gastrointestinal symptoms. Heat, exercise demands, food, drink and individual health can interact. A bad run does not establish that one ingredient caused it.
Set up a useful first rehearsal
Pick a lower-stakes training run with easy access to home or a toilet. Keep the pre-run meal familiar. Avoid combining a new breakfast, new shoes, a harder workout and a new fuel in the same experiment.
Record the exact food or product, flavour, serving amount and any caffeine. If using a drink, record powder and water separately and follow its preparation directions. Keep the packet or photograph the label so that the next rehearsal uses the same thing.
Choose a feeding pattern you can remember and carry out safely. Use a watch reminder if useful, but do not let an alarm override how you feel. You are gathering information, not passing a test.
Build the trial around an appropriate plan from your sports dietitian or established training routine. There is no universal weekly increase in this guide. Your event, current tolerance and total food intake matter more than a fixed ladder.
Use a log that separates amount from timing
| Record | Example note, not a prescribed plan |
|---|---|
| Before the run | Usual breakfast; finished two hours before; slept poorly |
| Conditions | Cool morning; easy route; 80 minutes planned |
| Food and drink | Exact label serving, water used, caffeine if present |
| Timing | When each portion was taken and where water was available |
| Symptoms | What happened, how strong it felt and when it began |
| Practical problems | Packet hard to open; bottle leaked; missed planned stop |
| Next trial | Repeat, or change one clearly identified variable |
Describe symptoms plainly. "Stomach bad" is less useful than "bloating started after the second drink and settled when I slowed down". Include whether symptoms continued afterwards. A simple personal comfort scale can help compare your own sessions, but it is not a diagnostic tool.
Write the notes soon after the run. Keep good trials too. If only difficult sessions make it into the log, you lose the evidence of what already works.
Change one thing, then repeat
If carrying and opening the fuel was the problem, solve that before changing its ingredients. Put it in a reachable pocket, practise opening it while stationary and check that the packaging suits wet hands. These are useful improvements with no nutritional guesswork.
If symptoms occurred, review the whole session: breakfast, amount, concentration, pace, heat and timing. A sports dietitian can help choose the next change. Do not automatically add salt, remove whole food groups or buy a premium powder because one run went badly.
When a routine feels comfortable, repeat it under comparable conditions. Then test the practical demands that matter for the race, such as your planned kit and pace, within your training programme. Comfort on an easy jog does not guarantee comfort in a hard event.
Keep an acceptable backup. If your preferred flavour is unavailable, the replacement deserves its own trial. "Same brand" is not enough when ingredients, caffeine or serving size differ.
Rehearse the actual course logistics
Map the expected aid stations against the moments you plan to eat or drink. A fuel that needs accompanying water is inconvenient if the next water point is far away. Check the manufacturer's directions rather than assuming all gels or powders are prepared the same way.
Practise what you can control: vest pockets, bottle refilling and counting portions. If the event changes its on-course product, revisit that part of the plan. Bring the details to your dietitian rather than making a large last-minute change.
For athletes subject to testing, nutrition tolerance and anti-doping checks are separate tasks. Our race-kit guide to tested electrolytes explains product and batch identification. A drink being handed out at an event does not establish its testing status.
When to stop experimenting
Persistent symptoms deserve assessment. Severe abdominal pain, blood in stools or repeated vomiting are reasons to stop and seek medical care, not push harder at gut training. Training discomfort should never be used to dismiss a new or worsening problem.
If several careful trials fail, take the log to a registered sports dietitian. It gives them concrete information and can save a cycle of buying and abandoning products. Do not treat a restrictive diet as the automatic next step.
One successful rehearsal is encouraging, not a guarantee. Keep the plan flexible enough for changed conditions and make the final race-day version simple enough to follow when tired.
Where NZ Supps fits
Use the intra-workout range to inspect actual carbohydrate content rather than assuming the category name means race fuel. The hydration range serves a different job when a product supplies minerals without meaningful carbohydrate. Start with what your plan needs; you may already have suitable food and a bottle at home.
Frequently asked questions
How long does gut training take?
There is no guaranteed timetable. A small study found changes after two weeks, but runners, products and race demands differ. Start early enough to repeat useful trials without rushing increases.
Do I need gels to train my gut?
No. Rehearse the suitable food or drink you intend to use. The format needs to fit the race and your tolerance, not a rule that runners must use gels.
Should I increase carbohydrate every week?
Not automatically. First establish that your current routine is tolerable and practical. Any increase should have a reason linked to the event, with individual guidance where needed.
Does nausea mean I chose the wrong carbohydrate?
Not necessarily. Pace, heat, meal timing, concentration and other factors can contribute. Record the context rather than blaming one ingredient after one run.
Can I practise only on easy runs?
Easy runs can be a sensible place to begin. They do not reproduce every race demand, so later rehearsal should reflect relevant conditions within your training programme.
What is the most useful thing to bring to a dietitian?
Bring the exact labels and a few session logs, including successful sessions. Record amounts, preparation, timing and symptoms so the discussion starts with something more useful than a product name.
