Long Run Fueling: How to Build a Race-Day Nutrition Plan That Actually Works

Most runners treat the long run as a fitness builder and nothing else.
That misses the point.

The long run isn’t just about endurance. It’s a fueling rehearsal. Your gut learns to tolerate carbohydrate at pace. You figure out timing. You find out what works before race day forces the question.

One study found non-elite marathoners consume just 21.7g carbs/hour on race day versus the recommended 60g+.

GI problems are widespread, too, with research showing 70-90% of distance runners experience stomach issues during races. Most of those problems trace back to a lack of practice.

Get this right in training, and race day becomes execution. Skip it, and you’re guessing when the stakes are highest.

Key Takeaways

– Long runs are fueling rehearsals, not just fitness builders. Use them to test timing, volume, and products before race day.
– Carbohydrate targets scale with intensity. Aim for 30-60g per hour in training long runs. For race efforts over 2.5 hours, target 60-120g per hour. The upper end applies mostly to elite or highly experienced runners.
– Your gut adapts to what you practice. Regular carbohydrate intake during training increases your tolerance over time.
– Race day is not the time to experiment. Every gel, drink, and timing window should be validated in training first. Don’t add anything new on race day.

Fuel for the Work Required

Not all long runs need the same fueling plan.

A 90-minute easy run and a 3-hour race effort place different demands on your carbohydrate stores.

At an easy pace, your body burns a larger share of fat for fuel. Stored carbohydrate can last 2-4 hours or more.

At marathon race pace, carbohydrate burns faster, and those stores run out sooner. For most runners at race intensity, it takes roughly 90-120 minutes before the tank hits empty.

That is why fueling during the run matters. Beyond that window, the carbohydrate you take in is the difference between holding pace and slowing down.

The principle is simple: fuel for the work required. Easy long runs need less. Race-pace efforts need more. Match your intake to the demand.

Training Long Runs: Building Your Fueling System

Before the Run

Eat a carbohydrate-rich meal 2-3 hours before your long run. Scale the portion to your timing:

– 1 hour out: about 1g per kg of body weight
– 2 hours out: about 2g per kg
– 3-4 hours out: about 3-4g per kg

If you run in the morning, this is especially important. Your liver burns through its carbohydrate stores overnight. A pre-run meal tops them back up.

Keep fat and fiber low to reduce stomach issues. Stick to easy-to-digest carbs: white toast, white rice, oatmeal, a banana, or a bagel with jam. Avoid high-fat, high-fiber, and dairy-heavy foods close to your run.

For runs over 90 minutes, a small carbohydrate top-up 30 minutes before starting adds an extra buffer.

During the Run

For runs under 60-90 minutes at an easy pace, water or one gel is usually enough.

Once runs go beyond 60-90 minutes, or include faster segments, fueling becomes important. Target 30-60g of carbohydrate per hour. Start within the first 30-45 minutes. Do not wait until you feel depleted.

For race-pace long runs where you are practicing your marathon fueling strategy, aim higher. Target 60-120g per hour, using a glucose-fructose blend. The 120g figure comes from research on elite runners. Most runners will land in the 60-90g range during these sessions.

This is where runners get tripped up. By the time you notice a drop in energy, your blood sugar has already fallen. Staying ahead beats trying to catch up.

Spread your intake across the run. SiS GO Isotonic Energy Gel works well here. It delivers a manageable carbohydrate dose per serving without needing extra water to get it down.

Use training runs to test different products, flavors, and timing intervals. Note what works and what causes problems.

Why Gut Training Matters

Your gut adapts when you train it.

When you regularly ingest carbohydrate during runs, your intestines get better at tolerating them. Without that practice, most runners can only handle about 60g per hour before stomach issues start. With consistent training and the right carbohydrate blend, that tolerance can rise to 90g per hour or beyond.

That tolerance matters on race day. The runners who can handle more can fuel more. The ones who fuel more tend to finish faster.

Practice carbohydrate intake during runs at least once per week, mimicking your planned race-day strategy. Treat it like a rehearsal, not a rescue.

Race Day: Executing the Plan

Before the Race

Race-day preparation starts 36-48 hours out. Target 8-12g of carbohydrate per kg of body weight per day during that loading window. For an 85kg runner, that is roughly 680-1020g of carbohydrate daily.

If you are new to carb loading, start closer to 6-8g per kg and build up over several training blocks.

This is not about eating to discomfort. It is about filling the tank before the start gun goes off.

On race morning, eat your pre-race meal 2-3 hours before the start. Stick to foods you tested in training. A small carbohydrate top-up 15-30 minutes before the start helps keep blood sugar steady.

During the Race

For race efforts over 2.5 hours, target 60-120g of carbohydrate per hour using a glucose-fructose blend.

The upper end of that range, 120g per hour, is mostly relevant for elite or highly experienced runners. Research funded by SiS found that elite marathon runners can effectively use up to 120g per hour. At the highest intake rates, those runners showed improved running economy. Most runners will perform well in the 60-90g range.

Why the blend? Your gut handles glucose and fructose through separate channels. When you combine both, the total delivery increases compared to glucose alone. More fuel reaches your muscles instead of sitting in your stomach.

SiS BETA Fuel Energy Gel delivers 40g of carbohydrate per serving in a 1:0.8 glucose-fructose ratio designed for this purpose. Two per hour puts you at 80g. Three per hour reaches the upper end of the range for elite-level fueling.

Pre-plan every fueling window. Know exactly which mile markers you will take gels. Pair gels with water, not a sports drink, to avoid overloading your gut with carbohydrate.

Why This Matters

Underfueling at race intensity is one of the most common causes of late-race fade.

Over 60% of non-elite marathon runners take in less than 40g per hour. That tracks with slower finishing times and higher rates of medical issues on the course.

Race pace burns through carbohydrate faster than training pace. The higher target compensates for that increased demand. The carbohydrate you take in during the race slows the rate at which your stored fuel depletes. That buys you more miles before the wall.

Common Fueling Mistakes

• Waiting too long to start fueling. By the time you feel low, you are already behind. Start early and stay consistent.
• Trying something new on race day. New gels, new timing, new volumes. Any untested variable is a stomach risk.
• Ignoring individual variation. Guidelines are starting points. Body weight, pace, temperature, and personal tolerance all shift optimal intake. Test in training.

The Practical Cheat Sheet

Carb-loading note: If you are new to loading, start at 6-8 g/kg/day and build up across training blocks.

For half marathons, the consensus range is 30-60g per hour. Runners finishing under 2 hours can aim for the lower end. Those closer to or past 2 hours benefit from 50-60g per hour. Begin fueling around 30-45 minutes into the race.

The Bottom Line

Race-day nutrition is not invented on the morning of the race.

It is built in training.

Use long runs to test your carbohydrate timing, volume, and products. Find what works. Then execute a proven plan when it counts.

References

Burke, L.M. et al. (2007). Carbohydrates and fat for training and recovery. Journal of Sports Sciences.
Costill, D.L. et al. (1971). Muscle glycogen utilization during prolonged exercise. Journal of Applied Physiology.
Cox, G.R. et al. (2010). Daily training with high carbohydrate availability increases exogenous carbohydrate oxidation during endurance cycling. Journal of Applied Physiology.
Currell, K. & Jeukendrup, A.E. (2008). Superior endurance performance with ingestion of multiple transportable carbohydrates. Medicine and Science in Sports and Exercise.
Gonzalez, J.T. et al. (University of Bath). Breakfast before exercise and carbohydrate metabolism.
Jentjens, R.L. et al. (2006). Oxidation of combined ingestion of glucose and fructose during exercise. Journal of Applied Physiology.
Jeukendrup, A.E. (2010). Training the gut for athletes. Sports Medicine.
Morton, J.P. et al. Carbohydrate feeding during marathon running: impact on running economy and fueling rates in elite runners. Research funded by Science in Sport (SiS).
Pfeiffer, B. et al. (2012). Nutritional intake and gastrointestinal problems during competitive endurance events. Medicine and Science in Sports and Exercise.
Romijn, J.A. et al. (1993). Regulation of endogenous fat and carbohydrate metabolism during exercise. American Journal of Physiology.
Thomas, D.T. et al. (2016). Position of the Academy of Nutrition and Dietetics, Dietitians of Canada, and the American College of Sports Medicine: Nutrition and athletic performance. Journal of the Academy of Nutrition and Dietetics.