Whole foods and variety are all that you need to create a healthy diet designed to meet your training and race-day nutrition needs.
The crux? Learning how much to eat—and what foods suit you best—while you're training. Eating before a training session can cause problems for some runners. Not only can nerves affect appetite and digestion, but also the intensity of the exercise can present challenges for digestion and different demands for fuel too.
There are a couple of factors to consider when determining what to eat and when.
First, a runner's diet is typically based around carbohydrates. An adequate amount of protein and fat is still needed for a balanced nutrition plan.
Carbohydrates should come from healthier sources like whole grains, fruits and dairy rather than refined grains like chips, cookies, sugary soft drinks, sports bars and gels. Whole grains are a great source of fiber and are also rich in antioxidants. They have many health-protective properties in addition to being an excellent source of fuel. The same goes for fruits and vegetables. Eating a wide array of different colored foods ensures that you will get a mixture of important vitamins, minerals and other nutrients.
Secondly, consider the intensity of the run. If you're going for an easy recovery run lasting less than 60 minutes, it may not be necessary to fuel before your run. However, if you typically run first thing in the morning, you may often feel sluggish or light headed. This is likely because you have low blood sugar. While you're sleeping, your liver glycogen becomes depleted overnight causing you to wake with low blood sugar.
If carbohydrates are not eaten to bring that blood sugar up, you may experience symptoms of lightheadedness or fatigue. These symptoms can be worsened as exercise brings that blood sugar even lower. Having something as simple as a piece of toast or glass of juice in the morning should be enough to prevent the crash.