Different races require different types and amounts of training as well as varying nutritional requirements. To run a marathon you need to put in months of training. You also need to develop a nutrition plan that fuels your workouts, allows you to store muscle glycogen, and provides you with adequate fuel and hydration throughout the race.
Running the 5K doesn't require months of training or a finely-tuned nutrition plan that longer races do. But it does require that you eat the appropriate nutrients to support your training. It also requires getting enough vitamins and minerals from your foods to support a healthy immune system and prevent illness that could keep you sidelined.
Also, having a plan for proper pre- and post-race nutrition will help you avoid unwanted GI issues during the run and keep you from gaining weight.
Healthy Everyday Training Diet
Glucose fuels the brain and muscles, and runners need strong bodies and brainpower to perform.
How to get glucose: Carbohydrates break down into glucose faster than fats and proteins can be converted. If you're looking for quick energy, carbohydrates are the way to go. But contrary to popular belief, a runner's diet doesn't need to be made up entirely of breads, pasta and cereal. Aim for 50 to 65 percent of your daily intake to come from quality carbohydrate sources like whole grains (brown rice, whole wheat bread, quinoa), low-fat dairy products, fruits and vegetables (with a dose of the starchy ones like sweet potatoes). Round out your meals with a source of lean protein and some healthy fats like olive oil, avocado, or nuts and seeds. This is very basic, but a good training diet doesn't need to be complicated.
What to Eat on Race Day
The slightly more complicated aspect of a 5K training diet is choosing what to eat race-day morning. Your daily diet plays the biggest role in determining how well you're able to train, recover, and stay healthy. But the meal(s) you choose to eat (or not eat) before a race is the most important one. If your race is early in the morning, your dinner should serve as your main meal. This meal should be rich in carbohydrates, moderate in protein, and low in fat. You'll want to avoid foods high in fat or fiber because these can make digestion tough and lead to GI distress the next day.
Many runners make the mistake of thinking they need to "carbo-load" on plates full of pasta and breadsticks the night before a race. Carbohydrate loading is a scientific process that involves decreasing training and increasing carbohydrate intake in the days before an event. When done correctly, it can allow an athlete to maximize their muscle glycogen stores, which is the fuel used in longer races, to avoid "hitting the wall." Research has shown that this technique is only useful for athletes competing in events lasting 90 minutes or longer, which is rarely the case with a 5K.