The latest ‘fashionable’ attack in the war on obesity is GI – the Glycemic Index! As usual, it’s nothing new, but a more modern, simpler, user-friendly way of explaining the benefits of slow-release carbohydrates rather than rapidly absorbed ones.
Carbohydrates (sugars and starches) are absorbed from food into the bloodstream at different rates depending on the food’s composition and the carbohydrates chemical form. Some carbohydrates, particularly sugars, enter the blood rapidly, glucose being the fastest, resulting in a rapid rise and high peak to blood sugar levels. Quickly up can also mean quickly down and these peaks and troughs are thought by nutritionists to put a strain on the body’s metabolism, giving risks of disease, such as diabetes and heart disease.
These fluctuations can also promote feelings of hunger (the munchies!) leading to further over-eating. So, eating a more complex, unrefined carbohydrate type diet will place less strain on the body, releasing sugars into the blood over longer periods, up to six hours, much as nature intended. But there is still some confusion over which carbohydrate source is better and which is worse, as like all things, myth, old-wive’s-tales and non-science all lead to confusion.
Enter the GI – a number, relative to pure Glucose (100), by which each food can be graded. High is bad, low is good, but watch out for foods that contain high fat (eg chocolate). They have a low GI due to the masking effect of fat on the sugar, but are high in calories. What is more suprisiing though is some of the foods that have relatively high GIs. Baked potatoes, for example have a high value of 98, caused by the effects of cooking, and the particular properties of potato starch granules that are easily and therefore quickly broken down during digestion.
Racing cyclists should choose their carbohydrate-rich food according to their specific needs at specific times. Before training and competition, where you usually eat 2-4 hours before the event, you should eat foods with low- to medium Glycemic Index. These will produce a slower blood sugar rise making the carbohydrate available more slowly. This is why pasta is the more established choice.
During a normal event (2 to 3 hours), the body needs fuel that is made available rapidly, and is easily eaten during the effort of cycling. Glucose and allied products such as maltodextrins (most energy drinks) are most popular. Where events last longer, medium GI foods, such as bananas, are useful particularly as they come in their own wrapper.
After the race or intense training, the body is physiologically better able to re-fuel the muscle glycogen tanks, and research has shown that eating food high in GI immediately after exercise is the best way to re-fuel. Carbohydrate drinks, again, are one of the best ways to achieve this, immediately after strenuous exercise, particularly if you find it difficult to eat solids. Jelly babies and energy bars also work well! Continue to take in carbohydrate every half hour or so up until you have the next meal.