Fueling for Training and Race Day

Fueling for Training and Race Day

Fueling your body is an integral part of training for and running a marathon. With so many resources stating contradictory information it is difficult to navigate what exactly we should be eating. The nutrition information below will help to guide you in taking steps to better your diet. Please keep in mind that your diet is everything you consume on a day to day basis, and I am not referring to it in the sense of something you go on to lose or gain weight.  All of the nutrition information below comes from courses in my undergraduate studies, personal research, and speaking with certified nutrition professionals. Please keep in mind that the recommendations below are not a prescription and I highly recommend that you consider working with a certified nutrition professional to create an individualized nutrition plan for you.

Everyday Diet

Fueling your body for optimal performance on race day starts with your everyday diet. If you are eating out for most of your meals, or eat a lot of junk food, can you expect your body to perform to the best of its ability? Probably not. Your body needs a variety of nutrient dense foods to function properly and keep you fueled during training and on race day. To learn more about what types of fruits, vegetables, protein, fats and carbohydrates are healthiest, as well as how much of each food group you should eat, check out:


Choose My Plate is a wonderful resource to learn about portion sizes, recipes and menus, how to eat healthy on a budget, and examples of what types of fruits, vegetables, grains, protein foods, dairy and oils are the healthiest options. Not only is this a great resource for you, but for your family as well! Keep in mind that Choose My Plate is not designed for athletes; you will more than likely need to consume more than the recommended daily amounts listed on the website due to the energy demands of your body. You should consult with a registered dietitian to determine your most optimal diet. The RRCA recommends a low fat (20-25% of the calories in your diet should come from fat), moderate to high carbohydrate (50-65% of your diet), and moderate protein (15-25% of your diet) diet for optimal performance.


Carbs are the gas in the tank, they provide fuel to muscles and help prevent mental fatigue. Put simply, carbohydrates are starches and sugars, and are our body’s quickest source of fuel. Carbohydrates are stored in your liver and muscles in the form of glycogen. These glycogen reserves are utilized to stabilize blood sugar and allow muscles to function optimally.

  • Carbohydrates should make up 50-65% of your daily diet. This will allow your body to store an adequate amount of energy for a 2 hour run at moderate intensity.
  • For longer runs more carbohydrates are needed and should be replenished during those runs.
  • You can replenish these glycogen stores by eating GU, energy bars, and other fuels during your training runs.


Proteins are complex molecules that are found in our bodies in the form of muscle, bone, cartilage, skin, and many other tissues. Protein is needed for muscle regeneration, cell function, mental energy, and can help decrease hunger that arises during longer training efforts. Protein takes longer for your body to break down so be careful you do not over consume it before a run.

  • The ISSN recommends that endurance athletes need 1.0 to 1.6 grams per kilogram a day (or .45 to .72 grams per pound).
  • When endurance training volume is high and intense more protein is required. During lower volume training (such as during base training) fewer grams of protein are needed.
  • When exercising longer than 2-3 hours make sure to consume a source of protein during your run.


Fat provides fatty acids that line every cell in your body. In order to use carbohydrates and fats, we need healthy foods rich in fat for optimal cell function, hormone balance, and energy production. Do not restrict your fat intake, but choose healthier sources of fat.

  • Fats should make up 20-25% of your daily diet.
  • Fats are necessary to keep you full, maintain a healthy heart, and they add flavor.
  • They help sustain prolonged exercise at lower intensities.

Timing - Before, During, & After Exercise


  • Shorter weekday workouts -- Eat 30-60 minutes before
  • Longer weekend workouts or competition -- Eat 2-3 hours before
    • Don’t worry about waking up before the long run to carbo load - eat well the night before and then snack 30-45 minutes before running.
  • Choose a meal or snack that is low in fat and contains complex carbohydrates and a little protein.
  • Remember to eat familiar foods that you know you can tolerate and won’t upset your stomach.
  • Practice what you will eat for your race during training.


  • For runs up to 120 minutes, it is recommended to consume 30 to 60 grams of carbs per hour of exercise.
  • For runs over 120 minutes, aim for 60 to 90 grams of carbs per hour.
  • Start taking gels at 75 minutes on race day - depending on your body size a slurp of gel every 2-3 miles (15-30 minutes) will help stave off glycogen depletion.
  • Examples of about 30 grams of carbohydrate
    • 1 banana
    • 10 pretzels
    • 2 Fig Newton’s
    • ½ PB&J sandwich
    • ¼ bagel
  • Energy Gels
    • One gel has 22 to 29 grams of carbs, along with electrolytes. Take these with water to speed delivery of the energy to your system.


  • What you eat after your workout will affect how your muscles recover.
  • Eat a snack or meal with carbohydrates and protein within 30 minutes of completing your workout, and then again within 2 hours.

Where Gu Is

GU is not provided at every aid station, so plan accordingly. Below is a list of which aid stations provide GU

  • Bandera mile 8
  • Garcia mile 13.4
  • Twin Falls mile 15.9
  • Cedar Falls mile 21
  • Edgewick 1 mile 23
  • Edgewick 2 mile 24.5


Water delivers nutrients to working muscles and helps regulate body temperature. Both dehydration and overhydration (hyponatremia) have serious consequences including death.

  • Symptoms of dehydration: weight loss, lethargy, dizziness, nausea, vomiting, dry mouth/ lips
  • Symptoms of hyponatremia: weight gain, headache, nausea, lethargy, confusion/disoriented

It is recommended to drink:

  • Your body weight x 0.55 = ounces of water you should drink daily

Drinking enough water will help you to feel better and have more energy during your runs and throughout the day.

Before Exercise

  • Drink 10-16 oz of fluid every 1-2 hours before exercise and then another 4-8 oz right before you start. This is a recommendation and you should listen to your body and how it responds to different amounts of water before exercise.

During Exercise

  • Follow a schedule (don’t rely on thirst): drink 4-8 oz of water or a sports drink every 15-20 minutes.
  • Drink early and drink often (dehydration can lead to stomach cramps and diarrhea). However, if you are feeling waterlogged do not force yourself to drink more.
  • Throughout your training, practice what you will do come race day, including how you will carry fluids with you.
  • Use your body weight before and after you exercise to gauge your hydration level - this will help you to avoid dehydration and hyponatremia.

After Exercise

  • Drink 24 oz of water or sports drink for every pound of body weight lost during exercise.

Take Away

To perform at your best you need to do the following on a daily basis

  • Base your diet on whole grains, fruits, veggies, low fat dairy, lean meats, and small amounts of healthy fats like nuts, avocados, flax seed, and olive oil. Avoid packaged and processed food. As a rule of thumb try grocery shopping on the perimeter of the grocery store this is where the healthiest foods are, and avoid the inner isles.
  • Drink plenty of water (body weight x 0.55 = ounces of water you should drink as an exerciser).
  • Eat the correct portion sizes so that you can attain or maintain a healthy body fat percent for your sport.
  • Time your meals so that the calories you eat will be effective at fueling your training and recovery.
  • Practice what you will do on race day - nothing new!

~Sierra, The Tunnel Marathons Trainer


Disclaimer: Please keep in mind that I am not a registered dietitian and do not have a nutrition certification. The information in this article is based on education I received in my undergraduate studies, research I have done, and interviews with Certified Nutrition Professionals. The recommendations written in this article are not a prescription and all dietary changes that you make should be discussed with a certified nutrition professional.