⚠️ Affiliate Disclosure
This article contains affiliate links. As an Amazon Associate, we may earn from qualifying purchases at no additional cost to you.

New Release

The Half Marathon Training Plan

Get the complete 14-week schedule, reference charts, and training log in paperback.

Order on Amazon →

---

fueling long runs is the single biggest difference between finishing strong and hitting the wall.

If you’ve ever felt amazing on a long run… and then, out of nowhere, everything collapses—heavy legs, brain fog, emotional crash, walking when you planned to run—that isn’t a motivation problem.

It’s physiology.

Runners call it bonking, and it’s one of the most predictable (and preventable) failure points in half marathon training. In this guide, you’ll learn exactly how to fuel long runs with the right carbs, timing, and gut training so you can finish long runs strong—without guessing.

---

---

Quick Answer: The Bonk Fix (Save This)

If your long run is 90 minutes or longer, fueling is not optional.

Simple long-run fueling rules:

• Start fueling early: 20–30 minutes in (not when you feel tired)
• Keep fueling consistently: every 20–30 minutes
• Aim for 30–60g carbs/hour (advanced runners may tolerate more)
• Practice it in training: don’t wait for race day

We’ll break down the “why” below, and then give you a simple plan you can follow for any long run.

---

What “Bonking” Actually Is

Bonking is acute glycogen depletion—you run low on your body’s fast-access carbohydrate stores.

Here’s the key idea most runners miss:

Your aerobic system can burn fat for fuel, but fat alone can’t support half marathon pace when training gets serious. Carbs are the high-octane fuel that keeps your pace stable.

When glycogen drops too low:

• pace falls off a cliff
• effort spikes
• coordination and form degrade
• perceived exertion skyrockets
• mental toughness feels “gone”

That’s why bonking feels sudden. It’s not gradual fatigue—it’s a fuel system failure.

---

Why Water (and Even Electrolytes) Don’t Prevent a Bonk

This matters, because it’s a common mistake:

• Electrolytes help hydration and neuromuscular firing
• Carbs provide energy

Electrolytes can reduce cramping risk and improve fluid balance, but they do not replace energy.

So if you’re 90 minutes into a long run, drinking water (or electrolytes) without carbs is like trying to keep a car moving by topping off windshield wiper fluid.

✅ Want the electrolyte side done correctly?

• Best electrolytes guide: https://halfmarathontrainingplan.com/recovery-nutrition/best-electrolytes-for-runners/
• Magnesium guide (sleep/recovery): https://halfmarathontrainingplan.com/recovery-nutrition/best-magnesium-for-runners/

---

The Biggest Mistake: Fueling Too Late

Most runners wait until they feel tired, hungry, or “low.”

By then, you’re already behind.

A smarter approach is preventative fueling:

• You don’t wait for a flat tire to inflate your tires
• You don’t wait for your phone to die to charge it
• You don’t wait for the bonk to begin fueling

Fuel early so you never get close to empty.

---

How Many Carbs Do You Need Per Hour?

A simple, safe guideline for most half marathon trainees:

• 30–60g carbs per hour for long runs
• start at the low end and build tolerance

Where runners get stuck is not the number—it’s how to actually execute it without stomach issues. That’s where gut training comes in.

---

Gut Training: Why Gels Upset Your Stomach (At First)

If gels feel gross or cause GI distress, don’t assume you “can’t do gels.”

Most runners simply haven’t trained their gut yet.

Your gut is trainable, like your legs:

• consistency improves tolerance
• practice improves absorption
• race day becomes routine

This is why you should start fueling practice early in the training plan, not on race week.

---

The Fuel Type That Works Best: Glucose + Fructose

Here’s a high-level concept that helps you choose smarter fuel:

Many runners do better with fuels that combine glucose + fructose, because they can use multiple absorption pathways, reducing bottlenecks and improving delivery.

Translation:

• smoother energy
• less gut overload (for many runners)
• better tolerance at higher carb intakes

You don’t need to obsess over chemistry, but you do want to test a few options and find what your stomach likes.

---

The Practical Fueling Plan (By Run Length)

Runs under 60 minutes

• Fuel: no
• Water: optional
• Goal: just run

Runs 60–90 minutes

• Fuel: optional
• If you’re training hard, doing hills, or running hot: consider one gel
• Goal: begin practicing the routine

Runs 90–120 minutes+

• Fuel: mandatory
• Start: 20–30 minutes
• Then: every 20–30 minutes
• Goal: finish strong, not survive

---

The “Bonk-Proof Long Run Checklist”

Use this checklist before your long run:

• ✅ Ate carbs earlier in the day (don’t start depleted)
• ✅ First gel ready before you start
• ✅ Fuel timer set (phone or watch alert)
• ✅ Tested gels in training before race day
• ✅ Hydration plan matches weather + sweat rate

---

Common Questions Runners Ask

“Do I need gels for a half marathon?”

If you’re running 90 minutes or longer, fueling is strongly recommended. Even if you can finish without it, fueling often improves performance, reduces suffering, and helps you recover faster.

“What if gels upset my stomach?”

That’s usually a training issue, not a permanent limitation. Start with smaller doses, slower pace, and practice consistently.

“Can I just use real food?”

Yes—bananas, chews, gummies, carb drinks, and homemade options can work. The key is still the same: carbs per hour + timing + practice.

---

Cross-Link: Consistency Beats Motivation (This Matters Here)

One of the biggest long-run mistakes is trying to “make up” for a bad fueling day by going harder the next run.

Don’t.

If you had a rough long run:

• adjust your fueling plan
• test again
• stay consistent

Here’s the mindset framework that keeps runners improving week after week:
https://halfmarathontrainingplan.com/mindset-motivation/consistency-in-running-training/

---

Runner Tip of the Week

Never try something new on race day.
Long runs are your fueling laboratory. The race is the demonstration.

---

Want a Full Plan (Built-In Fueling + Recovery)?

And if you want the full framework built directly into a training plan, it’s laid out step-by-step in the Half Marathon Training Plan book: