Adam Barber
How to Carb-Load Correctly Without Feeling Bloated
Carbohydrate loading is often associated with the night-before-race pasta dinner, but effective carb loading involves more than one large meal. Done correctly, it can increase muscle and liver glycogen stores before prolonged exercise, helping ensure you have enough fuel when glycogen stores become a limiting factor.
Since OTE started in 2012, we've helped endurance athletes — from first marathons to Olympic start lines — get race-week fuelling right. The mistakes we see most often aren't about eating too little; they're about eating the wrong things in the final 48 hours.
What Is Carb Loading? The Science of Glycogen Storage
What is carb loading? In a nutshell, it’s a dietary strategy designed to maximise muscle and liver glycogen stores before prolonged exercise. Glycogen is the body's stored form of carbohydrate and an important fuel source for endurance activity.
Muscle glycogen is particularly important during prolonged exercise because stores gradually decline as the body uses carbohydrate for fuel. Increasing carbohydrate intake while reducing training allows the body to store more glycogen than usual. This process, known as glycogen supercompensation, helps increase glycogen availability before an event.
Carbohydrate loading can support endurance performance, particularly during events lasting around 90 minutes or longer. A high-carbohydrate diet, combined with reduced training and supplemented with energy gels or bars, can maximise glycogen stores and help maintain carbohydrate availability during prolonged endurance exercise.
How to Carb Load Correctly: Established Loading Protocols
Carb loading correctly means planning your carbohydrate intake around your event rather than simply eating more. For prolonged endurance events, established guidance generally recommends around 10 to 12 g of carbohydrate per kg of body weight per day during the final 36 to 48 hours.
Two main approaches are used:
|
Approach |
Duration |
Method |
|
Classic depletion-loading |
Around 6 days |
Reduced carbohydrate intake and training, followed by several days of high carbohydrate intake |
|
Non-depletion loading |
2 to 3 days |
High carbohydrate intake combined with reduced training, without deliberately depleting glycogen first |
Classic Six-Day Depletion-Loading Method
The classic protocol runs over about six days: three days of reduced carbohydrate intake alongside glycogen-depleting training, followed by three days of high carbohydrate intake and a training taper. The depletion phase drives a strong supercompensation response, but it's physically and mentally demanding, and the low-carbohydrate window can leave you feeling flat — which is why it tends to suit experienced athletes who've practised it.
Two- to Three-Day Non-Depletion Method
For many athletes, a 2- to 3-day approach is easier to plan and practise. Glycogen stores can be substantially increased through high carbohydrate intake and reduced training, without a preceding depletion phase — so most people can skip the depletion week. Whichever method you choose, practise it in training rather than the week of a race.
Getting the amount right is only half of it. How do you carb-load properly without feeling bloated? Start by spreading your carbohydrate intake across meals and snacks, choosing familiar foods and avoiding a sudden increase in portion sizes.
For a closer look at marathon nutrition, including pre-race meals, hydration and race-day fuelling, OTE's marathon nutrition guide covers the practical details.
