In the racing/nutrition world, carbohydrate foods are given a “speed” glycemic rating of 1 to 100 depending on how quickly they affect blood sugar levels: fast, moderate, and slow.

Fast: Foods from 70–100 range
Try: Carrots, Potatoes, Honey, Cornflakes, Bread

Moderate: Foods in the 50s and 60s
Try: Shredded Wheat, Brown Rice, Muesli, and Sweet Potatoes

Slow: Foods in the under-40 range 
Try: bananas, most beans, low-fat dairy, peanuts, edamame 

But for fast effort, fast fuel is good, right? Not quite. Take a “fast” snack too soon, and your body compensates, blood sugar drops in a rebound effect, and you’re draggin’ your wagon. Eat too low on the scale for prolonged exertion and your body runs out of glycogen.