Carb -loading is a practice used by some athletes to gain a supposed boost in performance The idea is to load the liver and muscles with glycogen before an endurance event.
Three to four days before an event the athlete deplete’s themselves of carbohydrates reducing their intake to less than 20% carbohydrate, eating mostly fats and protein. The day before the event they resume a high carbohydrate diet which in theory fills the hungry muscles and liver with glycogen.
Changing the diet from 60/70 % carbohydrate to suddenly less than 20% is extremely unhealthy, with nothing but fat and protein in the system the athlete runs on empty and becomes extremely irritable. Water retention in the loading period may also be an issue since for every gram of carbohydrate taken in one or two grams of water is retained so your body will suddenly lose water due to the reduction in carbohydrates then suddenly gain a significant amount causing stress to the body. In susceptible individuals angina pain can also be experienced as a result of eating excessive carbohydrates. In the initial period if your body has no carbohydrates or sufficient fats to fuel the body it will then start to break down the muscles to use protein as its fuel.
Putting too much fat into your system before an event can have consequences, the effects of excessive fat in bloodstream can be felt for up to 60 hours, the athlete would be at a disadvantage with a sluggish oxygen delivery system regardless how much fuel stored in liver.
The biggest change in the week before an event is in your training, tapering and resting/easy two days before and not changing your food. You need not eat extra calories this week, the reduction in training, if you stick to your normal diet will give you 600 to 1000 calories per day extra. This energy that is normally expended during training will now be used to fuel your muscles. Choose low-fat meals in the days before, ensuring you have your normal calorie intake from carbohydrates rather than fat. Choose your carbohydrates wisely, taking your carbohydrates as fruit or fruit juice you could end up with diarrhea, eating too many white bread products such as bread and pasta may clog your system. Learning the right balance takes time and you should practice in training as well as at event time.
If you eat correctly this week with the same calories but with less exercise and more calories from carbohydrates than fats you will put on weight due to water retention, however this should only be a couple of pounds and easily lost when you start your normal training regime and shows that you have sufficeint energy stores for your event.