Your body’s main source of energy is glucose, which is stored as glycogen in the muscles (for immediate use) and liver (as backup), says study co-author Javier Gonzalez, Ph.D., senior lecturer of human physiology at the University of Bath in England. Your brain may be able to sense when your secondary supply is low and in turn, tell your body to slow down.
Fructose helps maintain those reserves by stimulating the liver to take up more glucose. Eat both sugar sources during and after your first race and you’ll collect enough so you can go your fastest the next day, too.
If your first run lasts more than 80 minutes, eat at least 30 grams of carbs per hour throughout (in addition to the other nutrients you need, such as sodium), Gonzalez says. If your second event is a half marathon or longer, aim to eat the rest of your carbs for the day in the first four hours post-race. He recommends 1.2 grams per kilogram of body weight (71 grams for a 130-lb woman or 98 for a 180-lb man) every hour.
The bottom line:
Get your glucose-fructose combo from sources with equal amounts of each sugar type such as bananas (which have 27 grams of carbs each), grapefruit (26 grams each), honey (17 grams per tablespoon), dates (18 grams each), and Honey Stinger products.