Low G.I. foods are best before an event—approximately two hours before the big race. The meal will have left the stomach by then but continues to be digested in the small intestine for hours afterwards. The slow rate of carbohydrate digestion in low G.I. foods helps ensure that a steady stream of glucose is released into the bloodstream during the event. The extra glucose is available when needed towards the end of the exercise when muscle carbohydrate stores are running low. In this way, low G.I. foods increase endurance and prolong the time before exhaustion hits.

It’s also important to select low G.I. foods that do not cause gastrointestinal discomfort such as stomach cramps and flatulence. Some low G.I. foods such as legumes are high in fibre or indigestible sugars. However, not all low G.I. foods are fibrous and high residue The high amylose rices (Basmati and Doongara) and any form of white pasta are good examples of low G.I. foods that don’t contain much fibre. Instant noodles have a low G.L, too. Athletes who are too nervous to eat a solid meal, may prefer a liquid supplement such as Sustagen™ sport, which has a low G.I. (43).

Helen O’Connor, a dietitian who works with many of Australia’s Olympic athletes, teaches them how to manipulate the G.I. factor of their diet. Her pocket guide The G.L factor and Sports Nutrition provides menu plans and case studies and more hints for eating and competing. Her book The Taste of Fitness is packed with low G.L recipes for sports people.

The food industry is keenly interested in the G.I. factor, too, and it won’t be long before there are specially formulated low G.I. foods on the supermarket shelves specifically aimed at the serious sports person. The sports drinks that are enjoying much popularity at present have a high G.L, between 70 and 80. So they may not be an advantage before the event, but they are an invaluable aid during the event when blood sugar needs to be topped up, as well as after the event when glycogen stores need to be replenished.

The following table shows the serving sizes of low G.I. foods containing 50 grams or 75 grams of carbohydrate.

You will not win if your pre-event meal is jiggling around in your stomach (this will affect the jogger more than the cyclist). So test the timing and amount of low G.I. food during your training sessions. Then you’ll be ready for the big day. Don’t try it out for the first time on the day of the competition!

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