What to Eat Before Each Type of Run
The type of run is the most important consideration when trying to decide whether to eat or not before a run. It's through hard training sessions that we acquire the physical adaptations and skills that make us stronger, faster and enduring runners. Therefore, you want to give your body every possible advantage to work at its peak during these hard training sessions. One way to do that is by providing your body with pre-exercise fuel and adequate hydration.
In general, for harder workouts or runs lasting longer than 60 minutes, it's a good idea to have eaten a meal within the past 3 to 4 hours or a smaller snack within the past 1 to 2 hours.
Muscle glycogen stores can provide about 1,400 to 1,800 calories worth of fuel, if fully loaded. This will equate to about 90 minutes of moderate- to high-intensity steady state running and about 60 minutes of high-intensity speed work or interval training.
Having a pre-exercise snack can provide early fuel and delay the body's dependence on muscle glycogen. Keep in mind: The more intense a workout, the more blood will flow away from the stomach and to the working muscles, impairing digestion. This is why it's important to experiment with your body's tolerance of different foods. This will ensure you find which types of fuel work best with your digestion while still providing the optimal amount of energy.
Shorter recovery runs are generally low to moderate in intensity and burn an even mixture of carbohydrates and fats. The fuel demands of these types of runs don't necessarily require a pre-run meal. However, if the run is early in the morning, you may want to eat a small snack to refill your liver glycogen and stabilize your blood sugar.
How Timing Affects What to Eat Before a Run
This brings us to timing. Low blood sugar resulting from an overnight fast can cause some problems—even on easy runs. Blood glucose is our brain's only source of fuel. Without an adequate amount we may start to experience the following symptoms of hypoglycemia (low blood sugar): lightheadedness, blurred vision, difficulty concentrating and irritability. None of these symptoms set the table for a productive or enjoyable run. If you're an early morning runner, it might be worth your while to try a pre-run snack.