What To Eat Before You Run | Training Your Gut To Take In Fuel

Updated: Sep 25

By Holley Samuel MEd, RD, LD, CPT

Fueling for runs is one of the most significant things a runner can do to get the most out of their training session. Fueling properly helps prevent injury by providing the body with adequate energy to complete the workout safely and repair muscles.

Going into a run or training session without eating anything may lead to increased fat oxidation (burning fat for energy over carbohydrates), leading to muscle breakdown and decreased performance during training. Lack of carbohydrates amplifies hunger cues later in the day, increases the risk of energy crashes, and potentially a host of other health concerns.

If an athlete continues to train undernourished, also referred to as chronic underfueling, it can lead to a condition called relative energy deficiency in sport RED-S (What is RED-S?), which significantly affects all body systems. This can turn a health-promoting running habit into an unhealthy and potentially dangerous situation.

If eating before you run is new or if a runner experiences gastrointestinal distress during runs when they eat before training, here are a couple of suggestions to try:

  • Aim for low fiber, easy to digest carbohydrates

  • Avoid fat and high amounts of protein or fiber pre-run

  • Stay hydrated with electrolytes and fluids (Summer Hydration Tips)

  • Start small, with 15-20g of carbohydrate for a few runs, and then increase that dose by 10-15g (see examples below)

Training Your Gut To Take In Fuel

The gut has to be trained just like muscles to become more efficient in taking on fuel pre-run. Some runners have more sensitive digestive tracts than others and may have to be more intentional and mindful during this process. Once runners gain confidence including pre-run fuel, they can start to aim for recommended carbohydrate amounts depending on the duration and intensity of their activity.

Pre-run Fuel For Training Up To An Hour (30 - 60 minutes)

Generally speaking, runners should aim for about 30-60g of carbohydrates pre-exercise for activities for up to an hour. Examples of these amounts may include:

  • 1 large banana

  • 4 graham cracker rectangles

  • 2-3 dates

  • 12oz juice

  • 12-16oz sports drink like Gatorade Endurance, Tailwind, Maurten, UCAN, or Skratch Labs

  • 1 cereal or granola bar (look for low fiber, fat, and protein options)

  • 1 cup cereal

  • 2 applesauce pouches

  • 1 gel

  • 1 serving gummy candies

  • 1 piece of toast with 1 TB jam

  • Stroopwaffel

  • 1-2 serving pretzels, goldfish, crackers

Pre-run Fuel For Training More Than An Hour (60 - 90 minutes)

For activities longer than an hour, runners should aim for about 60-90g carbohydrate pre-run, with some runners needing even more depending on their individual needs, and for durations over 2 hours in length.

Runners may also need more time to digest this amount of carbohydrates, depending on their individual gut transit times. If runners do have more time (over 2 hours) to digest this larger amount of food, they may also include a small amount of protein and fiber. Examples may include:

  • 1 bagel with 1 TB peanut butter and 1 tsp honey

  • 1 PB&J sandwich

  • 1 cup oatmeal with 1 banana

  • 3 pancakes with ¼ cup maple syrup

  • 4 graham cracker rectangles + 1 serving sports drink

  • 1 granola bar + 2 applesauce pouches

  • Sandwich or wrap with 1-2 cups of fruit on the side

  • Quinoa salad with roasted potatoes

It may be beneficial for runners to write down what they eat pre-run on their training plans or in a food diary to track what foods work well for them or any symptoms that arise. They can adjust what they are eating if needed and continue experimenting with various foods.

Fueling Early Morning Runs When You're Short On Time

Early morning runners who don’t have time to digest a lot of food pre-run may benefit from choosing liquid forms of carbohydrates. Take a gel or some chews with some water during the first mile of the run to fuel, or consider having a carbohydrate-rich bedtime snack to top off glycogen (stored carbohydrate) stores the night before to help.

Pre-run fueling doesn’t have to be complicated- runners need to gradually introduce pre-run fuel and find what works best for them.

"How to properly fuel your weekend long run.” by Holley Samuel MEd, RD, LD, CPT