Carb Loading for Endurance Athletes: The Complete Guide to Fuelling Your Best Race

Smart strategy or just an excuse to demolish a bread basket? Let's break down what actually works.

If you've ever trained for Comrades, Two Oceans, an Ironman, the Cape Town Cycle Tour, or any ultra, you've definitely heard someone say it:

"I'm carb loading."

Sometimes that means carefully planned meals designed to maximise performance. Other times? It means polishing off a tray of koeksisters two nights before race day and calling it "sports nutrition."

So what's the real deal?

Here's the thing: carbohydrate loading is one of the most researched and proven nutrition strategies in endurance sport. When done right, it can genuinely improve your performance, delay fatigue, and help you hold your pace when it matters most.

But it's also one of the most misunderstood.

Let's cut through the confusion. Here's the science behind carb loading, when it actually matters, and exactly how to nail it before your next big event.

Why Carbohydrates Matter for Endurance Performance

Your body stores carbohydrates as glycogen — mainly in your muscles and liver.

Think of glycogen as your body's high-octane fuel tank.

During endurance exercise (especially at moderate to high intensities), your body relies heavily on this glycogen for energy. The harder you push, the faster you burn through it.

The catch? Your glycogen stores are limited.

Most athletes can only store enough glycogen for roughly 90 minutes to 2 hours of hard effort before levels start dropping significantly. That's when things get uncomfortable:

• Pace drops off a cliff
• Power output tanks
• Legs feel like lead
• Concentration disappears
• You "hit the wall" (and it hits back)

Carb loading works by increasing the glycogen stored in your muscles before the event — essentially giving you a bigger fuel reserve to draw from when you need it most.

Does Carb Loading Actually Improve Performance?

Yes — and the research backs it up.

Studies consistently show that proper carbohydrate loading can improve endurance performance, particularly in events lasting longer than 90 minutes.

The proven benefits include:

• Delayed fatigue
• Faster time trial performances
• Higher sustained power and pace
• Stronger finishing kicks
• Lower perceived effort (it feels easier)

For endurance athletes, glycogen availability is one of the biggest factors determining how well you perform.

Here's an important mindset shift: carb loading won't magically make you fitter overnight. What it does do is allow you to fully use the fitness you've already built. All those early morning training sessions on the roads around your neighbourhood? Carb loading helps you cash in on them.

When Do You Actually Need to Carb Load?

This is where a lot of athletes get it wrong.

Not every training session or race requires carb loading.

Carb loading is most beneficial for:

• Comrades Marathon
• Two Oceans Ultra Marathon
• Ironman and 70.3 events
• Stage races
• Cape Town Cycle Tour and other long-distance cycling events
• HYROX Doubles and Pro divisions
• Any endurance session over 2 hours

It's probably unnecessary for:

• Your local parkrun
• A 45-minute gym session
• Easy recovery rides
• Short interval sessions
• Most events under 60–90 minutes

If your event is relatively short and your normal diet already includes decent carbohydrates, aggressive carb loading won't give you much extra benefit.

So no — Tuesday night pizza "because you have a 10K on Saturday" isn't exactly scientifically essential. (Though we won't judge.)

The Biggest Carb Loading Mistake Athletes Make

Most people hear "carb loading" and think:

"Eat as much food as humanly possible."

That's not the goal.

The aim is to increase your carbohydrate intake specifically — not just calories or whatever sounds good.

Here's the problem with massive high-fat "cheat meals": fat slows digestion and fills you up before you've actually consumed enough carbs. The result?

• Less glycogen storage
• More digestive discomfort
• Feeling sluggish on race morning

So while that doughnut definitely contains carbs... it's also loaded with fat.

One or two are absolutely fine. Half a dozen "for performance reasons"? Probably not optimal fuelling.

How to Carb Load Properly: A Step-by-Step Guide

Good news: modern carb loading is much simpler than the old-school methods. You don't need depletion workouts or extreme low-carb phases beforehand.

The Sweet Spot: 2–3 Days Before Race Day

Aim for approximately:

8–12g of carbohydrate per kg of body weight, per day

Yes, that's a lot. Which is exactly why choosing the right carbohydrate sources matters.

Best Foods for Carb Loading

Focus on foods that are:

• High in carbohydrates
• Lower in fibre
• Lower in fat
• Easy to digest

Top carb loading foods:

• White rice
• Pasta
• Potatoes (without heavy toppings)
• White bread and rolls
• Oats and porridge
• Pancakes (easy on the butter)
• Fruit juice
• Bananas and other ripe fruit
• Mielie meal/pap
• Sports drinks
• Energy bars
• Low-fibre cereals

Carb loading favourites that work well:

• Rice/pap/pasta (without heavy gravy or fatty sauces)
• White bread/Provita/crackers with jam or honey
• Futurelife/Pronutro or other cereals
• Ripe bananas, mangoes, naartjies, and other fruit

Pro tip: As you get closer to race day, slightly reduce very high-fibre foods to minimise bloating and stomach issues. Your gut will thank you — especially if you're toeing the line at Comrades.

What About Weight Gain During Carb Loading?

Many athletes panic when the scale creeps up before race day.

Relax — this is completely normal and actually a good sign.

Every gram of glycogen stored pulls around 3 grams of water into the muscle with it. So if you gain 1–2 kg during your carb load, that typically means your glycogen stores are properly topped up — not that you've suddenly gained body fat.

Feeling a bit "full" or slightly heavier before a long endurance event? That's your fuel tank doing exactly what it should.

Carb Loading Doesn't Replace Race-Day Fuelling

This is another common misconception worth clearing up.

Carb loading maximises your starting fuel stores. It doesn't eliminate the need to fuel during the race.

Once you're moving, you're still burning through glycogen rapidly. That's why your race-day nutrition plan still matters:

• Energy gels
• Carbohydrate drinks
• Bars and chews
• Electrolytes
• Regular fluid intake

Think of carb loading as starting the race with a full tank. But you still need to top up along the way — whether that's between Pietermaritzburg and Durban, or around the peninsula.

5 Practical Carb Loading Tips That Actually Work

1. Don't leave it until the night before

One massive pasta dinner isn't true carb loading. Spread it across 2–3 days for the best results.

2. Reduce your training volume

Your body stores glycogen most effectively when training load decreases slightly. This is why tapering and carb loading go hand-in-hand.

3. Practise before your goal race

Never try an aggressive carb load for the first time before the race that matters most. Test it during a long training run or a less important event first.

4. Stick to familiar foods

Race week is absolutely not the time to experiment with new "healthy" recipes your gut has never encountered. Keep it simple and predictable — foods you know work for you.

5. Use liquid carbs strategically

Sports drinks and carbohydrate mixes make it much easier to hit high targets without feeling stuffed. They're especially useful when solid food feels like too much.

The Bottom Line: Is Carb Loading Worth It?

For longer endurance events? Absolutely.

It's one of the few nutrition strategies with decades of solid research consistently showing real performance benefits.

But here's the key: effective carb loading is strategic, not chaotic.

It's not about eating everything in sight. It's about intentionally increasing carbohydrate availability so your body can perform at its absolute best.

So yes:

✅ Extra rice before Comrades? Smart move.

✅ Structured carb intake before an Ironman? Essential.

❌ Six koeksisters because "the carbs will help"? Probably not elite-level sports nutrition.

Fuel smart. Race strong. And let the treats play a supporting role — not the entire race plan.