Carbo Loading – Does It Improve Performance?


Have you ever heard of Arthur Lydiard? If you’ve been running for many years, chances are you know who he is. But if not, he’s one of the best-known and admired running coaches the world has ever seen!

He had some unusual training methods, such as insisting his athletes ran 100 miles a week at the very minimum and incorporating running strength work. But, he coached multiple athletes to Olympic victories, so he must have been doing it right!

One of the things he used to do was make sure that his Olympic athletes had an extra spoon or two of honey in their coffee before a race. Why? He’d noticed that they performed better that way.

And so began carbo-loading. Does it improve performance? Lydiard’s results certainly indicate that it does.

Let’s explore this method in more detail.

What is Carbo-Loading?

As its name suggests, carbo-loading is increasing the amount of carbohydrates you ingest prior to training or racing.

It’s a strategic move intended to maximize the amount of glycogen stored in the muscles. When you’re running, your body uses muscle glycogen as fuel.

So, when you have more glycogen stored in your muscles, it’s like having more fuel in the tank. You can run faster, for longer, before becoming fatigued.

What is the Normal Range of Glycogen? How High is It After Carbo-Loading?

The normal glycogen levels in the body are 100 to 120 mmol/kg of net weight. Carbo loading can increase this to between 150 and 200 mmol/kg.

That may not seem like much. But it’s believed that this increase in glycogen can add as much as 3% improvement to your performance.

Again, although this seems like a small amount, it can mean an improvement of around 7 minutes for a marathon! It’s a significant difference when you consider it in those terms.

How Does It Work? When Should You Start Carbo-Loading?

You can’t just eat donuts and pasta the day before your race to get a carb high. Carbo-loading needs to be done properly in order to be truly effective.

Also, carbo-loading won’t necessarily be helpful for races that are shorter than 90 minutes. It’s best for longer races, where more substantial energy stores become a clear advantage.

When to Begin

You can’t build up enough glycogen in your muscles from just one meal, even if it is a large meal.

For best results, you should begin carbo-loading 48 to 72 hours before your race. That is 2 or 3 days beforehand.

How to Do It Properly

If you’re training seriously, you should be monitoring your daily calorie intake. You should also be taking note of how much of your intake is protein, how much is carbs, and how much is fats.

When carbo-loading, try to keep your calorie intake the same as usual. You don’t need to consume more calories than usual to increase your performance. It’s all about the content of those calories, not the quantity.

On the days in which you carbo-load, you should aim for 70 to 80% of your food intake to be carbohydrates. To get a fairly accurate number of carbs you should be eating, multiply your body weight (in pounds) by 4.

The total is how many grams of carbs you should be eating (4 grams per pound of body weight). For example, if you weigh 200 pounds, you should be eating 800 grams of carbs (which equates to about 3200 calories).

Why is Fat Burning in a Race Not As Effective as Glycogen?

Your body gets fuel from two sources within itself: fat and muscle glycogen. Both are burned during a race to give you the energy you need.

But glycogen burns much more easily than fat. The body has to work harder to burn fat. This means it defeats the point of providing you with energy, as it’s using more energy to convert fat to fuel!

Have you ever felt the three-quarter race “bonk”, where you run out of energy? That’s the point where your body runs out of glycogen and has to slow down as it switches to using fat for energy.

It’s a slower process to convert fat to usable energy. Glycogen is already in an easy-to-use form, which is why glycogen storage is a much more effective way to provide running energy.

Am I Overeating with Carbo-Loading?

Not if you do it the right way! Remember, your aim is to keep your calorie intake the same.

You’re just adjusting the macronutrients within your calories. Instead of splitting your calories, for example, into 40% protein, 40% carbs, 20% fat, you’ll be increasing that carbohydrate count.

Your adjusted intake will look more like 20% protein, 75% carbohydrates, and 5% fat. But your total calorie count should still be the same.

Carbo-loading should still be a strategic, carefully planned nutrition tool. It’s not simply about having a few cheat days!

Make sure not to fall into the overeating trap. If you pile on the calories for 3 days before race day, you’re only going to feel heavier and more uncomfortable – the opposite to what you want during the race!

How Many Carbohydrates Can the Body Store?

Carbs (or glycogen) are stored mainly in the muscles and the liver. Your muscles can hold about 400 grams, and the liver can take approximately 100 grams.

When your glycogen stores are full, you can run for longer without needing to fuel up with an energy bar or energy gel.

What Carbs Should I Consume? What Should I Avoid? What About Fibers?

Not all carbs are created equal. Carbo-loading doesn’t mean you can go wild with the apple Danishes and chocolate bars. Choosing high-quality carbohydrates sources is vital for optimal performance.

It’s a great idea to go for low-sugar, low-fiber foods during your carbo-loading period. Too much sugar (whether natural or processed) can cause digestive issues. Too much fiber, surprisingly, can also be hard on the stomach.

Avoid processed carbs like baked goods, as they’re often packed with sugar and don’t have much nutritional value in them.

It’s tempting to just load up on fruits. But they’re often high in natural sugar and fiber, which can cause tummy trouble if you aren’t used to eating large amounts of it.

Bananas are a great, vitamin-packed, low-fiber fruit option. You can reduce the fiber content of other fruits by peeling them, so there’s no need to give up on fruits entirely!

Pasta is another good choice. Make sure to stick to your calorie count! It can be easy to go overboard with pasta, without even realizing it.

Vegetables are wonderful carbohydrate sources that are low in calories. Peel them to reduce fiber content, but you can eat a mound of veggies without making much of a dent in your calorie intake.

Be mindful of things like oil and butter when cooking. They’re high-fat ingredients and can cut into your calorie count, as well as sitting heavy in your gut.

Will I Gain Weight with Carbo Loading?

Your weight on the scale may increase when you’re carbo-loading. Don’t worry! If you’re staying within your calorie count, this won’t be fat. The extra pounds on the scale are water weight.

It can be a shock to step on the scale and get a weight that’s up to 4 pounds more than usual! It’s perfectly normal to retain water when you’re carbo-loading. Carbs like keeping water close by. So for every gram of carbs your muscle stores, it hangs onto an extra +/-3 grams of water.

Although this can be rather dreadful to see on the scale, it actually means your body is stocking up on hydration as well as glycogen. So not only will your muscle glycogen be fueling your body through the race, but the extra water you have stored will keep you better hydrated throughout the run.

When you’re finished your run, your weight should be closer to normal again. As you go back to your regular eating habits after the race, you’ll find that the number on the scale gets back down to your regular weight again.

So What Carb Meals are Recommended?

Not sure how to get started carbo-loading? Here are example meals we recommend eating in the few days before your big race.


As my doctor once told me, breakfast is king! Starting your day off right is important to see you through the rest of it. Here are a few suggestions:

  • Oatmeal with milk, honey, and cinnamon
  • Scrambled egg with toast
  • Poached eggs with a bagel
  • Plain, unsweetened yogurt with peeled fruit


We recommend having bigger breakfasts and dinners and going light on lunch. Try:

  • A sandwich (with a healthy filling, like salad, roast beef, or thinly sliced cheese)
  • Baked potatoes without the skin
  • A large salad, with vegetables like broccoli and cauliflower


It’s a good idea to have a larger dinner (be mindful of calories, as always), a few hours before you go to bed. Consider:

  • Pasta with a light, tomato-based sauce
  • Rice with vegetables and gravy
  • Tortillas with grilled vegetables and meat of your choice (go lighter on the meat and heavier on the veggies)


If you do get nibbly between meals, try to choose a lower-calorie, healthy snack that will take the edge off. Avoid sugary, empty-calorie snacks if you can! Go for:

  • Energy bars or protein bars
  • Healthy crackers
  • Raw veggies and healthy dip
  • Peeled fruit (NOT dried fruit!)
  • Yogurt


Don’t forget that what you drink adds to your calories and plays a large part in the quality of your nutrition. Store-bought fruit juice is not recommended, as it’s loaded with sugar and contains very little nutrition. Choose:

  • Freshly-squeezed fruit juice
  • Carbonated water (zero-calorie, leaving more calories for food)
  • Smoothies
  • Tea and coffee (with cream and sugar, or honey)

On Race Day

On the day of your race, timing is important. You want to have a high-carb meal about 3 hours before the starting gun fires. Something like a bagel with jam or a sports drink and oats. This will start you off strong!

While you’re running, aim to take a gel, chew, or sip of a sports drink every 30 to 45 minutes. This will help keep your muscle glycogen stores from being depleted too quickly.

Avoiding Mistakes

Like any training or performance-improving technique, it can be easy to make small mistakes that lessen the effectiveness of the technique. Carbo-loading is no different! Here are some of the most common mistakes so you can be aware of them and avoid them from the start.

Save It For Long Runs

Carbo-loading is most effective for runs in which you’ll be on the road for 90 minutes or more. Anything less than that, and your muscle glycogen stores won’t need to use everything you’ve stored.

Half-marathons, marathons, and ultra-marathons are the ideal times to carbo-load.

Don’t Over Do It On the Morning of the Race

One of the most common errors is piling on the carbs the night before, or on the morning of the race. Unfortunately, all you’ll be doing is making yourself heavier!

This is not enough time to build up your muscle glycogen stores effectively. You need 2 to 3 days before the race to build up your energy stores. If you’ve missed that window, a high-carb, high-volume meal the night before or in the morning is NOT going to give you that boost you need.

Don’t Eat Too Much Fiber

Fruits and vegetables are rich in fiber. If you’re not used to eating much fiber, overloading your system with high-fiber foods can lead to digestive issues. Of course, the last thing we want on race day is to have a niggly tummy.

Avoid brown rice, whole-grain bread and pasta, and unpeeled fruits and veggies. An easy way to reduce your fiber intake is simply to peel the fruits and vegetables you’re going to be eating.

Here’s a great list of low-fiber foods you can make use of during your carbo-loading days!

Don’t Overeat

Carbo loading does NOT mean a free-for-all cheat. It’s essential to stick to your calorie count.

Overeating doesn’t mean you’re adding extra glycogen to your muscles. You can reach full glycogen capacity by sticking to your calories – any overloading won’t add extra energy, just extra weight.

Balance Your Meals

Fruits and vegetables are important during carbo-loading. Don’t just pile on the pasta! Remember, veggies and fruits contain vitamins, minerals, and antioxidants.

You want to be as healthy as possible when you set foot on the road. That means nourishing your body with the best quality carbs possible!

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Shanna is a writer who runs... And cycles, jumps rope, and lifts weights. She lives in beautiful South Africa and enjoys sharing her knowledge and experience with other avid athletes.