One of the questions I'm asked most is how one should fuel around a run - this includes pre-, during and post-run nutrition. The answer is not straightforward and unique based on weight, training intensity, and in some cases dietary restrictions. I have done my best here to provide a general guideline or starting point for fine-tuning what works for you. The amount of food and timing are key to optimal performance for all 3 intake periods (pre- during and post-run). As you can see in the chart below, the more time you have before exercise, the more you can eat. If it's been more than 4 hours since you last ate, you definitely need to take in some carbohydrate before starting exercise to maintain blood glucose levels.