If you run outdoors, it can be a peaceful exercising in the solitude of the early morning hours. Plus, you get it out of the way before you have time to think of a reason not to do it. But, what about fuel for the run? Should you eat before running or is it best to run on an empty stomach?
Some runners choose to not to eat for fear they'll get an upset stomach. This is a legitimate concern and it's probably not smart to eat a full meal before doing strenuous exercise; but after an overnight fast your body's glycogen stores are going to be pretty low which can make exercise difficult. If you're prone to hypoglycemia, not eating before running could be dangerous.
The other argument some runners use for running on an empty stomach is they'll burn more fat this way. It's true that when the body is low on glycogen it turns to other sources for fuel; but during vigorous exercise the body is more likely to turn to muscle when there's no more glycogen. Loss of muscle mass isn't what most people want. On the other hand, if you're walking or jogging at a slow, steady pace, you will probably burn more fat if you don't eat before exercise.
If you'll be doing a slow jog and won't be out for more than forty minutes, it may be okay not to eat before running - as long as you aren't prone to hypoglycemia. If you intend to run harder or longer, eat a small meal or snack before hitting the road.
What foods are best to eat before running? You'll need carbs to boost glycogen stores if you want to maximize your performance. Studies have shown that a half gram of carbohydrates per pound of body weight eaten sixty minutes before exercise works well for runners. Adding more carbs doesn't seem to give additional performance benefits.
The best foods to eat before running are ones rich in complex, high fiber carbs such as whole grain cereal or whole grain bread. Old-fashioned oatmeal is a good choice since it's filling and has carbohydrates that won't trigger a rapid rise and fall in blood sugar. Another good pre-run snack is a peanut butter and jelly sandwich or whole grain crackers with peanut butter. Some people have problems with high fiber carbs because of gaseousness. If this is a problem for you, consider drinking a sports shake or a smoothie with fruit and yogurt. To avoid stomach upset, eat at least an hour before running.
The bottom line? Have something to eat before running, you'll improve your performance and make your run a more pleasant experience.