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Carbohydrate Loading: Definition, Examples, and Benefits

What is Carbohydrate Loading?

Carb loading is a nutritional strategy that aims to optimize athletic performance for endurance athletes, such as runners and cyclists. It maximizes glycogen storage in the muscles and liver, ensuring athletes have enough fuel to maintain a certain intensity level for an extended period. Carbohydrate loading is generally recommended for endurance races lasting longer than 90 minutes.

Examples of Carbohydrate Loading

Carbohydrate loading boils down to temporarily increasing carb intake while decreasing physical activity. Let’s review some examples of carb loading:

1. Classic 6-Day Loading

This is a popular approach to carb loading that works like so:

  • Days 0-3: Get only 15% of calories from carbs and work out as usual.
  • Day 4: Get 70% of calories from carbs and do a lighter session.
  • Days 5-6: Get 70% of calories from carbs and don’t do any exercise.

The idea is that depleting glycogen stores initially allows the body to store more glycogen once carb intake increases.

For instance, let’s say your athlete eats 3,500 calories daily. It would look like this:

  • Days 0-3: 3,500 * 0.15 = 525 calories (131 grams of carbs)
  • Days 4-6: 3,500 * 0.70 = 2,450 calories (612 grams of carbs)

2. Modified 3-Day Loading

This is a more straightforward approach lasting only three days.

Start with a demanding workout session in the morning of the first day and get around 70% of total calories from carbs for the remainder of the three days. Don’t work out again for the rest of the carb-loading phase.

3. 1-Day Loading

The one-day carb load is the simplest but may not have the same impact as a modified three-day or a classic six-day load. 

The goal here is to provide a glycogen ‘bump’ and temporarily improve performance, which could be helpful for sessions lasting 90 minutes or less (e.g., a tough gym workout).

To do this, avoid exercising for the day and consume approximately 4.5 grams of carbs per pound of body weight. Here’s what Bussau et al. wrote about this protocol in a study:

“..combining physical inactivity with a high intake of carbohydrate enables trained athletes to attain maximal muscle glycogen contents within only 24 h.”

For example, an athlete weighing 180 lbs must eat 810 grams of carbs.

The Benefits of Carb Loading

1. Improved Performance

When done correctly, carb loading maximizes muscle glycogen stores, providing the body with all the fuel it needs during physical activity.

2. Delayed Fatigue

While not necessarily true in all cases, a proper carb load can allow athletes to perform better for a longer period before getting tired. This is because glycogen depletion is associated with muscle fatigue.

3. Potentially Improved Muscle Recovery

In addition to supporting performance and delaying fatigue, carb loading can positively impact muscle recovery. Higher glycogen levels support muscle protein synthesis and reduce the risk of excessive breakdown during and after physical activity.


1. Who should consider carbohydrate loading?

Carb loading is ideal for endurance athletes who often need to be physically active at a certain intensity for extended periods (90+ minutes).

2. When should you start carb loading before an event?

Starting a carb-loading phase around three to five days before an event is usually best, as it gives athletes enough time to recover from previous physical activity and top up their glycogen stores.

3. What are the best foods for carb loading?

Low-fiber whole foods like potatoes, rice, pasta, and bread are excellent options. Junk foods like ice cream, cookies, and candy bars can also provide fast-digesting carbs, but it’s generally best to avoid them, as they are full of fats and don’t have the same nutritional value as whole foods.

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