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A diet for runners should derive most of its calories - 55 to 60 per cent - from carbohydrates. Carbs are a good source of glucose, the form of sugar that your brain, nerves and muscles needs to function properly. The majority of glucose is stored as glycogen in your muscles and liver. When you deplete your stores, your muscles and brain run out of fuel, leaving you feeling physically and mentally fatigued.

To prevent bonking - hitting the wall - during a run, everyday meals and snacks should emphasize such carbohydrate-rich foods as pasta, rice, whole-grain breads and cereals, legumes, fruits and low-fat dairy products. The following nutrition strategies will help you feel your best during a run, and recover faster afterward:

Eat beforehand

For runs 60 minutes or less you can rely on your glycogen stores to get you through - providing, of course, your daily meals and snacks contain carbohydrates. If you're running longer, eat a carbohydrate-rich snack at least 45 minutes before to supply glucose to your bloodstream. Pre-run snacks include fig bars, whole-grain cereal bars, energy bars, dried fruit, yogurt and berries, smoothies, even a small bowl of cereal with milk. These snacks are easily digested and won't leave you feeling full. Foods high in protein, fat or fibre take longer to empty from your stomach and are likely to cause digestive upset while running.

Load the carbs

If you're gearing up for a half or a full marathon, you'll need to top off your muscle glycogen stores the night before a long run and, for many long-distance runners, several nights before. Focus your evening meal on carbs such as pasta, rice, bread, thick-crust pizza and potatoes rather than protein-rich foods like meat. But don't overdo it. Consuming huge portions can lead to digestive issues - and unwanted bathroom stops - during your long run. Experiment well before race day to determine what works best for you. Eat a low-fat, high-carb snack before bed such as yogurt and fruit or toast with jam.

Take fuel along

If you're running longer than 75 minutes, you'll need to refuel on the run. Consume 30 to 60 grams of carbohydrate per hour of running, using a combination of sports drinks and energy bars, dried fruit, gummy bears or energy gels. Energy gels are packets of concentrated fruit-flavoured carbs. Use one to two gels for every hour of running (the harder you run, the more you'll need), starting 45 to 60 minutes into a long run. Chase gels, energy bars and dried fruit with plenty of water to avoid stomach cramps and indigestion.

Stay hydrated

Water is fine for runs of less than an hour. But if you're out longer, hydrate with a sports drink that replenishes water and electrolytes lost through sweat and carbohydrates burned by your muscles. In general, aim to drink 150 to 375 ml (5 to 12 ounces) of fluid every 15 to 20 minutes.

Refuel afterward

After your run, eat a recovery snack within 30 to 60 minutes, the window of glycogen recovery. Research shows that a combination of carbohydrate and protein (in a 3-to-1 ratio) is best for speeding glycogen replacement. Try low-fat chocolate milk, a blender smoothie made with milk and banana, an energy bar with fruit, half a bagel and yogurt, or half a tuna sandwich and an orange. These post-run snacks also replace potassium that you lose in sweat. Rehydrate with water, sports drinks and/or juice.

Boost your iron

This mineral helps power your run by making hemoglobin, the pigment that carries oxygen to working muscles. Without enough iron, your aerobic capacity is reduced and you'll fatigue early. Runners are thought to be vulnerable to low iron stores since it's lost through sweat and a small amount may also be lost through footstrike (the action of your foot hitting the ground), which can damage red blood cells in the feet.

Female runners who have higher daily iron needs due to menstruation have an even greater risk of deficiency. Iron-rich foods include beef, dark turkey meat, oysters, tuna, halibut, ready-to-eat breakfast cereals, legumes, cooked spinach, raisins and prune juice. To ensure you're getting enough, consider taking a multivitamin and mineral. Look for a product that contains 5 to 10 milligrams of iron (for men and postmenopausal women) or 10 to 18 milligrams of iron (premenopausal women).

Leslie Beck, a Toronto-based dietitian at the Medcan Clinic, is on CTV's Canada AM every Wednesday. Her website is .

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