People in good shape get to eat better stuff:

"Studies show that higher-fat diets make more sense for fit people than low-fat diets," says nutritionist Liz Applegate, Ph.D., author of Encyclopedia of Sports & Fitness Nutrition. "In one study, endurance athletes ran up to 24 percent longer before they fatigued when they ate a diet that was above 30 percent fat compared to one that was below 20 percent," she says.

Keep pedaling!