Good nutrition should be part of your ongoing training, not something you only start to do in the weeks leading up to the race.
If you train frequently it is a good idea to eat adequate, high-carbohydrate meals on a daily basis is so that your body is always ready for a run or workout. But unless you're a high-mileage runner, your daily calorie needs aren't going to be dramatically higher than a non-runner's. As a rough guide you burn around 100 calories per mile you run.
Your diet should have a balance of carbs, fats and proteins - as a rough guide your daily meals should consist of:
60-70 percent of calories from carbohydrates (grains, pasta, bread, etc.) 20-30 percent of calories from fat sources (oils, avocados, nuts, etc.) 10-15 percent of calories from protein (fish, meat, chicken, beans, etc.)
In your training you should be experimenting with the foods and hydration that work best for you so you’re not trying to figure it out come race day. Also practise when you eat before a run, as this is almost as important as what you eat to optimize your training.
Training time For morning workouts a general rule of thumb is to eat about 0.5 g/ 0.02 oz of carbohydrate per pound of bodyweight up to one hour before a workout. For a 68 kg/ 150 lbs runner that would be 75 grams/ 2.64 oz, or 300 calories worth of carbohydrate.
Afternoon and evening workouts give you more time to fuel your body with good carbohydrates and adequate amounts of fluids. It is important on these days to start off with a good breakfast and continue on with a healthy lunch 3-4 hours before the workout.
Choose foods that are high in carbohydrate, moderate in protein, and low in fat. Fats and proteins delay gastric emptying. Focus on complex carbohydrates for a sustained source of energy, but avoid very high fibre foods.
Training intensities The body’s ability to digest a recent meal depends on the intensity of the workout. If the pace is generally easy and is something you could easily keep up for 30 or more minutes, then your body should still be able to digest a recent meal or snack and use it for fuel.
The more intense a workout is, the more blood flow will be shifted away from the stomach and to the muscles, decreasing the body’s ability to digest. Therefore, more planning needs to go into pre-workout meals before more intense sessions as compared to meals before easier runs.
Top tips > Eat adequate, high-carbohydrate meals on a daily basis so that your body is always ready for a run or workout.
> For longer runs (more than 60 minutes), choose slowly digested carbohydrates like yogurt, apples, bananas, and oatmeal. Also consider similar foods for fueling during the long run.
> Avoid sugary foods like soft drinks, candy, and sugary gels that can quickly spike the blood sugar and actually lead to hypoglycemia.
> The more calories you eat, the more time you need to give your body to digest, especially before intense workouts.
> Try a variety of foods and fuelling habits throughout your training plan to find what works best for you.
> Practise your fuel and hydration strategy - you shouldn’t try anything new on race day!