Carbohydrate loading is a legitimate method of increasing the amount of carbohydrates you consume, coupled with a decrease in activity level, several days before you compete in a high intensity endurance athletic event. It's less efficacious for shorter activities such as recreational biking, swimming, weight lifting and five or 10 km runs.
Function
Carbohydrates are the primary source of energy in the body and the first fuel to oxidize, meaning that it burns. The main carbohydrate unit is a sugar such as glucose. Longer carbohydrate molecules are made out of long sugar chains and must be broken down by the digestive system. When absorbed into the bloodstream and taken to the cells, glucose is converted into a usable form of energy. Carbohydrates are found in grains, dairy products, fruits, vegetables and legumes.
Stored Energy
Fat is energy dense and tends to be the method by which energy is stored in the body. It's worth 9 calories per gram vs. the 4 calories per gram in carbohydrates. However, a small amount of carbohydrates is stored in liver and muscles as a molecule known as glycogen. Most complex carbohydrates are made out of linear chains, but glycogen is instead composed of branched sugar chains.
Significance
Normally glycogen sources may be depleted after 90 minutes of intense activity, which can affect stamina and performance, but according to the Mayo Clinic, carbohydrate loading increases the levels of glycogen stored in the muscles by up to two times. Three to four days before an event, you should increase your carbohydrate intake to 70 percent of your daily calories. Fat intake should be cut a little to compensate, and you need to scale back your training to avoid the depletion of glycogen stores.
Sources
Even though you are loading up on carbohydrates, it is still a priority to eat a healthy, balanced diet. You should simply be consuming more carbohydrates than usual. Bagels, whole grain cereals and bread, salads, wheat crackers, brown rice, fig bars, granola bars, baked tortilla chips and all kinds of different fruits and vegetables are potential sources of carbohydrates. Juices and milk are possible drinks that can be added to the meal. Milk in particular contains a good ratio of carbohydrates to protein, including all of the essential amino acids.
Considerations
When carbohydrate loading was first devised, it was suggested that carbohydrates should be restricted a week before competition to make room for the loading. But according to Louise Burke, PhD, of the Australian Institute of Sport, a severe restriction may cause overwhelming fatigue, irritability and a reduction in performance . The Mayo Clinic suggests a reduction of 50 to 55 percent of total calories, which should be enough to deplete glycogen in conjunction with training.
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