Running Nutrition for Long Runs: Gels, Fueling Schedules, and Race Day Strategy

Somewhere around mile 16 of a long run, you hit a wall. Your legs feel like concrete, your brain gets foggy, and every step requires conscious effort. This is bonking, and it is almost always preventable with proper mid-run nutrition. Learning what to eat during long runs, when to eat it, and how to avoid stomach issues is a skill that separates prepared runners from suffering ones.

When Do You Need to Fuel During Running?

You need to consume carbohydrates during any run lasting longer than 60 minutes to maintain performance and prevent glycogen depletion. For runs under 60 minutes, your existing glycogen stores are sufficient and mid-run fueling is unnecessary.

Your body stores approximately 1,500-2,000 calories of glycogen in your muscles and liver. At marathon pace, you burn through roughly 80-100 grams of carbohydrates per hour, depending on your size and intensity. Without replenishment, those stores run out after approximately 90-120 minutes, which is exactly when most marathon runners hit the dreaded wall.

The math is straightforward. If you burn 80 grams per hour and your stores last about 2 hours, then any run approaching or exceeding that duration requires external fuel. The goal of mid-run nutrition is not to replace everything you burn, which is physiologically impossible, but to supplement your stores enough to delay depletion and maintain performance.

Why Does Your Body Need Mid-Run Fuel?

Bonking is the sudden, severe fatigue that occurs when your body’s glycogen stores are depleted and your brain can no longer access sufficient glucose for normal function. It is not just tired legs. Bonking affects cognition, coordination, and mood because your brain depends on glucose.

When glycogen runs low, your body shifts to burning fat as a primary fuel source. Fat provides abundant energy but at a much slower rate than carbohydrates. This metabolic shift forces you to slow down dramatically, often by 30-60 seconds per mile or more. Mental focus deteriorates, perceived effort skyrockets, and what was a controlled race becomes a survival march.

Mid-run fueling works by providing a steady stream of exogenous carbohydrates, carbs from outside your body, that your muscles and brain can use alongside your diminishing glycogen stores. This extends the time before depletion and keeps your pace sustainable.

The recommended intake during exercise is 30-60 grams of carbohydrates per hour for efforts between 1-2.5 hours, and up to 90 grams per hour for ultra-endurance efforts beyond 2.5 hours (when using multiple carbohydrate sources like glucose and fructose together).

What Types of Running Fuel Are Available?

The market offers many options for mid-run nutrition. Each has distinct advantages and trade-offs.

Fuel Type	Calories Per Serving	Carbs (g)	Pros	Cons
Energy gels (GU, Maurten, SiS)	90-110	20-25	Compact, precise dosing, fast absorption	Texture can be unpleasant, requires water
Chews/gummies (Clif Bloks, GU Chews)	100-120	24-30	Easier to eat in portions, better taste	Require chewing while running, sticky
Sports drinks (Gatorade, Skratch)	80-140 per 16 oz	20-36	Hydration and fuel combined, easy to consume	Heavy to carry, diluted carb concentration
Real food (dates, pretzels, PB&J)	Varies	Varies	Familiar, palatable, cheap	Harder to carry, slower digestion
Maple syrup packets	100	26	Natural, single-ingredient, fast absorbing	Sticky, limited availability
Energy drink mixes (Maurten, Tailwind)	100-200 per serving	25-50	Customizable concentration, dual fuel+hydration	Requires mixing, taste may fatigue

Energy gels are the most popular choice for racing because they are compact, deliver a precise amount of carbohydrates, and absorb quickly. Most gels contain 20-25 grams of carbs per packet, which means you need approximately 2-3 gels per hour to meet the 30-60 grams per hour target.

Maurten gels deserve mention for using hydrogel technology that encapsulates carbohydrates in a gel matrix, reducing the osmolality and potentially decreasing stomach issues. They have become the dominant choice among elite marathoners.

Real food works well for training runs and ultramarathons where the pace is slower and digestion is less of a concern. Dates, pretzels, banana slices, and small PB&J sandwiches are all proven options. Some ultrarunners fuel entirely on real food and perform exceptionally.

How Should You Schedule Fueling by Distance?

Timing and quantity depend on how long you will be running. The following table provides a framework that works for most runners at moderate to fast paces.

Run Duration	Distance Equivalent	Total Gels (Approx.)	Fueling Schedule	Total Carbs
60-90 min	8-12 miles	1-2 gels	First gel at 30-40 min, second at 60-70 min	25-50 g
90-120 min	12-16 miles	2-3 gels	Every 30-40 min starting at min 30	50-75 g
Half marathon	13.1 miles	2-3 gels	Mile 4, mile 8, mile 11	50-75 g
Marathon	26.2 miles	5-7 gels	Every 4-5 miles starting at mile 3-4	125-175 g
Ultra (50K+)	31+ miles	8+ gels or equivalent	Every 30-45 min, mix gels with real food	200+ g

A critical principle is to start fueling early. Many runners wait until they feel depleted to take their first gel, but by that point it is too late. It takes 15-20 minutes for ingested carbohydrates to reach your bloodstream. Starting at 30-45 minutes into the run ensures a steady supply before you need it.

For a marathon, a common and effective schedule is to take a gel at miles 4, 8, 12, 16, 20, and 23. This provides roughly one gel every 4 miles, or every 30-40 minutes for a 3:30 to 4:00 marathon. Faster runners may need slightly fewer gels since their time on course is shorter.

How Do You Practice Nutrition During Training?

The number one rule of race day nutrition is never try anything new on race day. Every gel, chew, drink, and food item you plan to use in a race must be tested during training first.

Your gut is trainable. Runners who regularly practice fueling during long runs experience fewer GI issues than those who only fuel on race day. The gut adapts to processing food during exercise by increasing blood flow to the digestive system and improving the efficiency of carbohydrate absorption.

Start by introducing one gel during a long run and see how your stomach handles it. Over subsequent weeks, add more fueling until you are practicing your full race day schedule during your longest training runs. This process takes 4-8 weeks, so build it into your training plan well before race day.

Use your long runs to test specific products. If a race provides a particular brand of gel or sports drink at aid stations, train with that brand. If you plan to carry your own fuel, practice running with whatever carrying system you will use.

PaceBoard tracks all of your training sessions, so you can review which long runs went well and which ones involved a fade in pace or elevated heart rate. Cross-referencing your fueling strategy with your performance data helps you dial in what works.

How Do You Prevent Stomach Issues While Running?

GI distress is the most common reason runners avoid mid-run fueling, and it creates a vicious cycle: they do not practice fueling because it causes issues, and it causes issues because they do not practice.

Several strategies reliably reduce stomach problems during running.

Train your gut. Regular practice with mid-run nutrition increases your gut’s tolerance. Start with small amounts and gradually increase over weeks. Research shows that athletes who practice fueling have significantly fewer GI issues than those who do not.

Avoid fiber and fat in the hours before running. High-fiber and high-fat foods slow digestion and increase the volume of food sitting in your gut during a run. Stick to simple, low-fiber carbohydrates for your pre-run meal.

Start fueling early and in small amounts. Taking half a gel every 20 minutes is gentler on your stomach than taking a full gel every 40 minutes, even though the total intake is similar. Smaller, more frequent doses maintain steadier blood sugar and reduce GI stress.

Stay hydrated. Dehydration reduces blood flow to your gut, which impairs digestion and increases nausea. Always drink water alongside gels. Most gels are designed to be consumed with 4-8 ounces of water.

Avoid high-fructose fuels if you are sensitive. Some runners experience bloating and diarrhea from high-fructose gels. Gels that use maltodextrin or a glucose-fructose blend (at a 2:1 ratio) tend to be better tolerated.

Slow down when you eat. Taking a gel at race pace while breathing hard is a recipe for choking and nausea. Many experienced runners slightly reduce pace for 15-30 seconds while consuming a gel, then resume their target pace.

What Should Your Race Day Fueling Plan Look Like?

A race day fueling plan removes decision-making from the equation. You know exactly what you will eat, when you will eat it, and where you will get it.

Here is a template for a marathon fueling plan:

Night before: High-carb dinner (pasta, rice, or bread-based meal) with moderate protein. Drink extra water and consider adding electrolytes.

Race morning (3 hours before): Familiar pre-race meal of 400-600 calories, primarily carbohydrates. Coffee if you are a regular caffeine user.

30 minutes before start: Small bite if desired. 4-8 ounces of water or sports drink.

During the race:

• Mile 3-4: First gel with water
• Mile 8: Second gel with water
• Mile 12: Third gel with water (or sports drink from aid station)
• Mile 16: Fourth gel with water
• Mile 20: Fifth gel with water
• Mile 23: Sixth gel with water (optional, some runners skip this one)

At every aid station: Sip water, take the sports drink if it is a brand you have trained with, skip it if not.

Write your fueling plan on your arm, tape it to your gel flask, or program reminders. In the mental fog of the late miles, you will be grateful for a plan that does not require thinking.

PaceBoard can help you practice your pacing strategy during training long runs so that on race day, your pace is dialed in and you can focus on executing your nutrition plan alongside it.

What About Fueling for Shorter Races?

The 5K does not require mid-race fuel. The 10K does not either for most runners. But the half marathon sits in a gray zone where fueling makes a meaningful difference.

For half marathons, 2-3 gels taken at roughly miles 4, 8, and 11 provide enough supplemental carbohydrate to maintain pace through the finish. Faster runners who finish under 75 minutes may get by with 1-2 gels, while those running over 2 hours should fuel more aggressively.

Even for 10K races, the pre-race meal is critical. Glycogen stores should be topped off so that the race does not dip into reserves that affect your energy levels for the rest of the day.

Putting It All Together

Mid-run nutrition is a skill, not an afterthought. Start fueling early, aim for 30-60 grams of carbohydrates per hour during long efforts, practice everything in training, and have a concrete plan for race day. The runners who fuel well do not just finish stronger. They enjoy the experience more, recover faster, and build confidence for the next challenge.