Carbohydrate (carb) loading is one of the big food topics in endurance sports. I see it a lot in groups that I am part of. I always see people posting pictures of what they ate the night before a race or ask questions about what is the best food for carb loading. There is a correct way to carb load that most people do not know about.
First, what is carb loading? It is used to fill the glycogen stores of the body of an endurance athlete for an event. It usually is performed 2-3 days before the event. The catch is that there needs to be a carb depletion phase 3-4 days before the loading phase takes place. This allows the body to work on limited carbs during the last week before a race so that when the loading phase takes place the body will, hopefully, store a little more glycogen than what the body normally stores. The body will only store enough glycogen for about 90 minutes of activity. The athlete needs to have started feeding the body carbohydrates in the event before the stores are empty. If not, this is what is called hitting the wall.
Why do we hit the wall? The energy source for the brain is carbohydrates in the form of glucose. If an endurance athlete is running for any time longer than 90 minutes the glycogen stores are empty. The body will try to maintain homeostasis (balance) so that the brain can have energy to continue working, but this will only last so long. About 20 to 30 minutes before the magic 90 minutes the athlete needs to intake some form of carbohydrates to keep the muscles and brain working correctly and then every 20 minutes or so until the athlete completes the event.
Back to carb loading. The athlete needs to start the depletion phase approximately 6 to 7 days before the event. This involves cutting back on carbohydrate intake to 50 to 55 percent of calorie intake. Remember to increase protein and fat intake to maintain the calories needed for energy. The body will use fat for energy since that last week before the event the athlete usually is into taper madness. Taper is cutting back on intensity and major long runs before an event. There is still running involved during he taper, but it is just to maintain the gains of training.
After the depletion phase the athlete should increase the amount of carbohydrates back up to 60 to 70 percent of the calorie intake. This happens the 3 days before the event so that the glycogen stores can be filled to capacity. A lot of athletes do not eat any big meals past lunch the day before the event. I suggest play with the timing of your carbohydrate intake to see how your body reacts. Again, remember to decrease the calorie intake of protein and fat to compensate for the increased carbohydrates.
And there you have it. Carb loading 101.