Fuelling and Testing Nutrition on Long Training Runs

Race-day fuelling advice always gives you a range, and you're left guessing where in that range your body actually sits — which is exactly what your long runs are for. For long runs over 75-90 minutes, aim for 30-60g of carbohydrate per hour, taken in 15g doses roughly every 20-25 minutes from the start of the run — not saved until you feel like you need it. That's a starting point to test, not a fixed prescription — below is the week-by-week schedule for locking it in, how gels, chews, real food and drink mix compare, and exactly what to do if GI distress hits mid-run.

Get this wrong and you won't find out in training — you'll find out at mile 10 of the actual race, when a product you've never really tested decides today's the day to fight back. The runners who cross the line with a settled gut aren't the lucky ones; they're the ones who treated every long run since week 4 as a rehearsal, not just a fitness session.

A Week-by-Week Testing Schedule Across Your Training Block

This is the single biggest gap in most fuelling advice, so here's the exact calendar I have athletes follow to lock in race nutrition before taper.

Comparing Fuel Sources: Gels, Chews, Real Food, and Drink Mix

Each fuel source trades off differently across GI tolerance, convenience, and cost. Gels are fast and convenient but carry moderate GI risk for sensitive stomachs, and they're the most expensive per gram of carb.

Chews release more slowly and are easier to titrate dose by dose, at a similar cost to gels. Real food — dates, pretzels, bananas — is the cheapest option and has the best GI tolerance for many runners, but it's the least convenient to carry and eat while moving. Drink mix combines fluid and carbs in one, but caps your total carb delivery at realistic drinking volumes.

One athlete I coached switched from gels to a real-food-and-chews combination in week 8 after repeated mild nausea, and completed race day with zero GI issues for the first time. The product wasn't the problem until it clearly was — and once it was, we didn't keep forcing it.

Timing Your Intake: Before, During, and After

For runs over 90 minutes, have a small carb snack 30-60 minutes beforehand if you're fasted. During the run, take your first dose at 20-25 minutes in, not at the first sign of fatigue. Afterward, aim for 1g of carb per kg of bodyweight within 30-45 minutes, for any run over 90 minutes.

Training Your Gut: How Tolerance Builds Over a Cycle

Gut carbohydrate absorption capacity is trainable. Repeated exposure to your target grams-per-hour dose over 6-8 weeks measurably improves tolerance — this is the actual mechanism behind "practice your fuelling," not just familiarity with a product's taste or texture.

Adjusting for Heat, Cold, and Altitude on Long Run Days

In heat, prioritise fluid and electrolyte intake over carb load if GI comfort is limited — dial carbs back to the low end of 30g/hour rather than forcing 60g in hot conditions. In cold, thirst cues are unreliable, so stick to your clock-based schedule rather than drinking to thirst.

At altitude, mild appetite suppression is common. Smaller, more frequent doses tend to sit better than large single doses when your appetite is already blunted.

Troubleshooting GI Distress Mid-Run and Correcting Course

Most fuelling content only covers prevention. Here's the in-the-moment decision tree for when something goes wrong anyway. Mild nausea or bloating: slow to a walk for 60-90 seconds, sip only, skip the next scheduled dose, and resume at the following interval.

Sharp cramping: stop taking anything for the rest of the session and finish on water only. If symptoms recur on the next long run with the same product, that product is ruled out — switch to a different type at your next test session. A product that causes GI distress once might just be a bad day. A product that causes it twice is ruled out permanently. I don't let athletes "give it one more try" close to race day.

Common Fueling Mistakes and How to Fix Them

Three mistakes show up again and again. Waiting until you feel low to eat — fix it with a clock-based schedule, not a feel-based one. Trying a brand-new product for the first time within 2 weeks of race day — fix it by locking your product choice down by week 10.

Under-fuelling long runs because "it's just training" — fix it by treating every long run over 90 minutes as a fuelling rehearsal, not just a fitness session. All three mistakes are avoidable with the same discipline: plan it, test it, don't improvise it on race morning.

Frequently Asked Questions

How many grams of carbs per hour should I aim for?

For long runs over 75-90 minutes, aim for 30-60g of carbohydrate per hour, taken in 15g doses roughly every 20-25 minutes from the start of the run. Treat this as a starting point to test, not a fixed prescription.

When should I take my first gel or fuel source?

At 20-25 minutes into the run, not at the first sign of fatigue. Waiting until you feel low means you're already behind on fuelling, and no dose fully catches you back up mid-run.

How many long runs do I need to lock in my fueling plan?

Plan for roughly 8-9 weeks of structured testing — weeks 4-6 for gut tolerance at conservative doses, weeks 7-9 to combine products at your target rate, and weeks 10-12 to rehearse the exact race-day product and timing with nothing new introduced after week 10.

Should I fuel easy long runs and race-pace long runs differently?

The dose and timing schedule stays the same either way, but race-pace segments are the more important test — gut tolerance under race effort and fatigue is what you're actually rehearsing for, and easy-run tolerance doesn't guarantee the same result under harder effort.

Can I actually train my gut to tolerate more carbs?

Yes. Gut carbohydrate absorption capacity is trainable — repeated exposure to your target grams-per-hour dose over 6-8 weeks measurably improves tolerance. That's the actual mechanism behind "practice your fuelling," not just familiarity with the product.

What should I eat before a long run, and how far in advance?

For runs over 90 minutes, have a small carb snack 30-60 minutes before starting if you're running fasted. This isn't your main fuelling strategy — it's just enough to avoid starting the run already low.

Do I need electrolytes on shorter long runs?

For runs under 90 minutes in mild conditions, plain water is usually enough. Once you're past 90 minutes, or running in heat, add electrolytes to your fluid or fuel source — sweat losses start to matter at that point regardless of pace.

What are the most common fueling mistakes?

Three stand out: waiting until you feel low to eat instead of following a clock-based schedule; trying a brand-new product for the first time within 2 weeks of race day instead of locking it in by week 10; and under-fuelling long runs because "it's just training," when every long run over 90 minutes is actually a fuelling rehearsal.

How should I adjust fueling for hot vs. cool weather?

In heat, prioritise fluid and electrolyte intake over carb load if GI comfort is limited — dial carbs back to the low end of 30g/hour rather than forcing 60g. In cold, thirst cues are unreliable, so stick to your clock-based schedule rather than drinking to thirst.

What should my recovery meal look like after a long run?

For runs over 90 minutes, aim for about 1g of carbohydrate per kilogram of bodyweight within 30-45 minutes of finishing. That window is when your body replenishes glycogen most efficiently, and it sets up your recovery for the next session.

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