Worried about eating the right food before a bike race or hard workout? Scientists at the University of Hull in England recently dialed in the perfect performance meal. They studied the effects of certain foods on the glycemic index to determine which would prove most beneficial when eaten pre-performance. (Learn how and what to eat on rides of every length.)
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The glycemic index (GI) is a scale of how carbohydrates in food affect our blood sugar, or glucose, levels. The glycemic index is based on the idea that not all sugars and carbohydrates are equal. For example, a cookie and an apple can plausibly contain the same number of calories and grams of carbohydrates. But, a food high on the glycemic index like a cookie can cause a blood sugar spike and crash (leading you to an early bonk), while a lower GI food like an apple provides sustained energy and even blood sugar levels.
For the study, researchers compared the results of 40 km time trials ridden by cyclists eating high or low GI foods. Forty-five minutes before the test, the cyclists ate cornflakes with low-fat milk (GI of 72) or branflakes with low-fat milk (GI of 30). The low-GI group finished the time trial with performances on average three minutes faster than the high-GI group.
The stark performance advantage from the low-glycemic foods, explain the scientists, results because lower GI foods lead to greater carbohydrate availability and usage during exercise. In other words, the athletes' food was more effective at providing fuel, and that the fuel burned more efficiently. While the low GI group was chugging away, the high-GI cyclists had to rely more on their fat reserves, which are harder for the body to burn than readily available carbohydrates, for energy. (Here's what happens to your stomach when you ride.)
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If you're interested in maintaining your blood sugar levels for better performane, you can visit the University of Sydney's Glycemic Index Database and search for your favorite foods to find their GI scores. A GI score of 55 is considered the line between high and low GI. For simple pre-race foods, try apples, oranges, and dates. Among fruit, these have the lowest GI, with scores around 40.
Matt Allyn is the features director for Bicycling and Runner's World magazines. He's run nine marathons and come heartbreakingly close to BQing three times. In addition to running and cycling, he's also covered beer for more than a decade and is a certified beer judge.
