Fueling for Marathon Training Sessions

How to Fuel Easy Runs, Tempo, Threshold, and Long Runs

Most runners only think about fueling on race day.
That’s usually too late.

Fueling is not just about avoiding the wall in a marathon. It is a training tool. 

When done well, it supports session quality, recovery, and consistency across the entire training block. 

When done poorly, it quietly limits performance long before race day arrives. The key principle is simple:

Fuel for the work required.

Carbohydrate intake should scale with session intensity and duration, not with one-size-fits-all rules. 

Below is a practical, session-by-session guide to fueling marathon training, including when fuel is not needed and when it is essential.

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Runs Under 60 Minutes

Easy Runs and Short Tempo Sessions

During the run, usually no fuel is needed.

If you ate within the last 3 to 4 hours, or the previous day was well-fueled, you typically do not need carbohydrates during runs under 60 minutes.

For most runners, water only is enough.

Pre-run: pick the option that fits your week

Option 1: Fasted (water only)
This can work if:

• Your last meal was 3 to 4 hours ago, or you fueled well the day before
• Weekly training volume is moderate
• You consistently feel good running this way

If your easy runs start to feel flat, or you notice persistent hunger later in the day, that is a signal that this strategy may be costing you more than it is helping.

Option 2: Light Carbohydrates (best default if you like eating before runs)

Aim for 25 to 50g of carbohydrate two to three hours before running.

Simple options include:

• Banana and toast
• Small bowl of oatmeal with honey
• Bagel or low-fiber cereal

Keep choices low fiber and low fat to reduce stomach issues

Quick note for high-volume runners
If you run high mileage, train twice per day, or feel chronically under-recovered, eating before even short runs is usually the better option.

This supports recovery and helps prevent a gradual energy deficit from building across the week.

When a gel can still make sense

If your goal is practicing race fueling and gut tolerance, or if you are a high-volume runner who struggles to eat enough across the day, taking a gel during short runs can still be useful.

This applies even when you do not technically “need” fuel for the session. A simple option is SiS GO Isotonic Gel. It is quick, easy to take at a pace, and does not require large volumes of fluid.

Gut-training practice

• Take 1 gel at 30 to 40 minutes
• Treat it like a rehearsal, not a rescue

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Runs Lasting 60 to 90 Minutes

Easy Runs and Tempo Work
This range is where runners get confused because the answer changes based on intensity.

Pre-run (recommended):

Eat 50 to 75g carbohydrate 1.5 to 2 hours before the session:

• Bagel + sports drink
• Toast with jam + juice
• Oatmeal + banana

Choose low-fiber, easy-to-digest carbs

During the run: depend on pace, not duration

Easy pace:
You can often go water only, even up to 90 minutes.

Tempo or marathon-pace work:
As intensity rises, carbohydrate demand rises. Fuel becomes more valuable.

A practical rule:

• Under 75 minutes: optional
• 75 to 90 minutes: aim for 30 to 60g carbs per hour

Simple execution:

• 2 SiS GO Isotonic Gels across the session (≈45g carbs)
• 1 SiS BETA Fuel Gel mid-session (≈40g carbs)

Start earlier than you think. Waiting until you feel low is usually too late to keep the intensity smooth.

Why this matters

Tempo runs are not just “a little harder.” They are often close enough to marathon pace that fueling practice becomes highly relevant. This is where your gut learns whether it can tolerate carbs when breathing is heavy and pace is honest.

Threshold Sessions

Sustained Hard Efforts Under 90 Minutes

Threshold sessions are quality sessions. If you under-fuel them, you are not building toughness. You are just lowering the ceiling of the workout.

Pre-run (recommended):

Aim for 50 to 75g carbohydrate 1.5 to 2 hours before:

• Bagel with jam
• Toast + banana
• Oatmeal + honey

This protects intensity and makes it more likely that you hit the actual training target.

During: optional for performance, useful for practice

If the total session time is under 90 minutes, most runners can complete the session with little in-run fuel.

But if your marathon race pace is close to threshold intensity, this is one of the best places to practice fueling under pressure.

Practical practice:

• 1 BETA FUEL or 1 SiS GO Isotonic Gel gel at around 30-40 minutes
• Or small, frequent sips of a carbohydrate drink

If you want something easy to take quickly, SiS GO Isotonic Gel is a straightforward choice. If you are building toward higher race-day intakes, this is also a good time to start introducing SiS BETA FUEL gradually in training.

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Long Runs

90 Minutes and Beyond

This is where fueling becomes the difference between a long run that builds durability and a long run that becomes an avoidable struggle.

Pre-long run: do not show up half-full

The day before:
Aim for 4 to 8g carbs per kg of body weight, spread across meals. This is not a huge “carb load.” It is simply making sure you arrive fueled.

Morning of the long run (2 to 3 hours before):
Aim for 75 to 150g carbohydrate, using low-fiber carbs that digest well.

During the long run, start early

The most common long-run fueling mistake is waiting until you feel depleted.

Start fueling at 20 to 40 minutes, even if you feel good.

Carbohydrate targets for long-term type

Use these as starting points and adjust based on comfort and tolerance.

• 90–120 min (easy): 30–60 g/hr
• 120–150 min: 50–90 g/hr
• 150–180 min: 60–90 g/hr
• Race-pace or 3+ hrs: 60–120 g/hr (trained)

If your long run includes marathon pace segments, treat it like a rehearsal. Fuel like you plan to fuel on race day.

Where BETA FUEL fits

When you start pushing toward higher intake ranges, “more gels” is not always the most comfortable solution. This is where SiS BETA FUEL becomes useful because it is designed for higher carbohydrate delivery and easier absorption at race-relevant intensities.

A simple strategy is:

• Standard long run: GO gels or carb drink to hit 30 to 60g per hour
• Race simulation: Beta Fuel-based plan to support 60 to 120g per hour

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Weekly Strategy

Fuel the Week, Not Just the Run

The biggest fueling mistake is not “under-fueling one run.”

It is slowly building a weekly deficit because hard days get treated the same as easy days.

Instead, match your daily carbohydrate intake to the session demand:

• Hard workouts and long runs: higher carbohydrate availability
• Easy and recovery days: lower, but not zero, especially if volume is high

You do not need perfection. You need alignment.

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The Practical Fueling Cheat Sheet

Under 60 minutes

• Before: optional 25 to 50g carbs
• During: water only
• Optional: 1 GO gel for gut practice

60 to 90 minutes

• Before: 50 to 75g carbs
• During: easy pace, water only is okay, consider taking 30 to 60g per hour

Threshold

• Before: 50 to 75g carbs (important)
• During: optional, but great for race fueling rehearsal

Long run 90 minutes plus

• Before: 75 to 150g carbs
• During: start at 20 to 40 minutes
• Aim for 30 to 120g per hour, depending on duration and pace
• Use BETA Fuel when practicing higher intakes

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KEY TAKEAWAYS

• Not all runs need fuel, but the ones that matter most often do.
• Pre-fueling is the easiest win for tempo and threshold sessions.
• Long runs should be fueled early and consistently, not reactively.
• Practice race fueling in training, including at harder intensities.
• SiS GO Isotonic Gels are a simple, fast option for execution.
• SiS BETA Fuel is a strong tool when you start targeting higher carb intakes.
  

Fueling is not a reward for running long.
It is part of the work.