If back-to-back meetings mean you'll have to skip a sit-down meal, grab a high-calorie bar with extra fiber and protein. It should contain 350 to 500 calories, nine grams of protein or more, and high-fiber carbohydrates, such as seeds, whole oats and dried fruit. You also want some healthy fat (from nuts, for example), which, says Christine Gerbstadt, M.D., R.D., a spokesperson for the Academy of Nutrition and Dietetics, "helps you absorb vitamins more effectively and keeps you feeling satisfied."
A Good Bar: Probar's Old School PB&J fills in for the lunchtime standby. It packs six grams of fiber, nine grams of protein, and other run-fueling nutrients, including 15 percent of your Daily Value (DV) for iron and seven percent for potassium to stave off muscle cramps.
More: 10 Tips to Eat Like a Pro Athlete
Post-Run Immunity Boost
The high mileage needed to train for a marathon or ultra makes you susceptible to colds and the flu. Good time to try an antioxidant-packed bar.
"The more intense your exercise is, the more you need antioxidants to help you recover," says Gidus. "There's good research suggesting that selenium, vitamin E, and other antioxidants help protect the immune system."
Nuts and dried fruits are rich in these antioxidants; cherries in particular contain phytochemicals, which help protect against cancer and heart disease and help reduce inflammation.
A Good Bar: After a run or as a snack, try Kind's Dark Chocolate Cherry Cashew Bar—it packs 50 percent of your DV for three key immune-boosting antioxidants: vitamins A, C, and E. Or eat Larabar's Uber Cherry Cobbler Bar, with cherries, almonds, and pecans.
More: How to Keep Your Immune System Strong
Long-Run Pain Relief
When mile 15 of your 22-miler has your body begging for ibuprofen, reach for a jolt of caffeine instead. A study published in 2009 in the International Journal of Sport Nutrition and Exercise Metabolism found that it reduces exercise-related pain during workouts.
(For instant relief, try these Topical Pain Relievers.)
Study participants who consumed caffeine prior to high-intensity cycling reported less quadriceps pain than those who did not consume it. Researchers believe that caffeine blocks the brain's receptors for adenosine, a chemical released in response to inflammation.
A Good Bar: Clif Bar's Cool Mint Chocolate pairs 50 milligrams of caffeine with the invigorating flavor of mint. Eat half a bar per hour of running, since it contains 10 grams of protein and five grams of fat, which could upset your stomach if eaten all at once.
More: Give Your Workout a Caffeine Kick