Training Your Gut For Athletic Performance

Dana Eshelman, MS, RDN, CSSD, METS I

The term “training your gut” describes a way to reduce the gastrointestinal (GI) stress that often occurs during training or race day. If you are an endurance athlete, chances are you have experienced this exercise-induced GI stress such as cramping, nausea, diarrhea, and/or vomiting.

Let’s take a step back and think about the physiology of digestion. Digestion normally occurs at rest when there is adequate blood flow to the gut allowing for absorption of nutrients and secretion of digestive enzymes. Exercise causes stress on the body and a shift in blood flow away from the gut causing changes in GI motility, absorption of nutrients, and secretion of enzymes that aid in digestion. This causes malabsorption and leads to a poor appetite, thus the athlete does not take in adequate hydration or fuel.

Unfortunately, under fueling and dehydration can cause additional GI distress and GI distress may be exacerbated by the intake of fuel and fluids during exercise. So, how does one tolerate more hydration and more fuel to support performance and prevent GI dysfunction? You train your gut!

What does “train your gut” mean?

There is a significant amount of research supporting the consumption of carbohydrates during exercise to maintain intensity and delay the onset time of exhaustion, especially at higher intensity. New research shows the gut is highly adaptable and can accommodate changes in your fueling through gene expression induced by sugar consumption. The evidence indicates there is a two to three week period of increasing carbohydrate intake during exercise to allow for adequate fueling and improved GI tolerance.

If you have had a poor experience (or many missed attempts) at fueling during exercise, you are not the odd one out. This is common. As the research shows, the body is adaptable and by practicing a fueling and hydration plan, you can improve your carbohydrate tolerance overtime. As with any nutrition plan, it is important to have a rehearsal of your fueling technique before race day. Your hydration plan is also of significant importance as this can help control GI distress and dehydration may exacerbate stress on the gut.

Proper Fueling + Training Your Gut The Academy of Nutrition and Dietetics recommends 30-60 grams of carbohydrate per hour of exercise and up to 90 grams of carbohydrate for endurance events lasting longer than three hours. If you are someone that trains fasted, or not eating anything pre-workout, starting off consuming 30-60 grams of carbohydrate before or during a workout may seem overwhelming and will likely cause GI distress. Here are some fueling techniques to train your gut:

	Start Here	Making Progress	Goal Nutrition + Hydration Pre workout
Pre workout 1-4 g/kg carbs in the 1-4 hours before exercise	1⁄2 piece of fruit + 1 T nut butter + 12- 16 ounces water OR 1⁄2 slice toast + 1 jam + 1 T nut butter + 12- 16 ounces water 12-15 grams carbs	​1 piece of fruit + 1 T nut butter + 12- 16 ounces water OR 1 slice toast + 1 T honey + 1 T nut butter + 12- 16 ounces water 25- 30 grams carbs	1 piece of fruit + 1 T nut butter + 1 T honey + 1 slice toast + 12- 16 ounces water 50-60 grams carbs
​During workout 30-60 g carb/ hour of exercise lasting longer than 1 hour	1-2 sports gummies OR 1⁄2 scoop drink mix in 32 ounces water 7-10 grams carbs	3 sports gummies OR 1 scoop drink mix in 32 ounces water 20- 25 grams carbs	6 sports gummies OR 2 scoops drink mix in 32 ounces water OR 3 sports gummies + 1 scoop drink mix in 32 ounces water 45-60 grams carbs

In the pre-workout phase you want to focus on adequate carbohydrate and low to moderate fiber, fat and protein foods. Carbohydrates are important for adequately fueling your muscles and topping off your energy stores, especially in workouts lasting longer than an hour. Fiber, fat and protein will slow down digestion, which we want to avoid pre-workout. These components should be consumed in meals and snacks throughout the day.

Pre-workout examples to work toward with 1- 4 hours before:

• 1 banana + 1 T nut butter (25 grams carb)

• 1⁄2 c oats + 1⁄4 c dried fruit (55 grams carb)

• 1 pita pocket + 2 T hummus (26 grams carb)

• Small sweet potato + 1/4 c greek yogurt (20 grams carb)

• Bob’s oat bar (28 grams carb)

• 1 c honey bunches of oats + almond milk (47 grams carb)

• Dave’s Bread + 1 banana + 1 tsp honey (54 grams carb)

Pre-workout examples to work toward with 15- 45 minutes before:

• 1⁄4 c dried fruit (20 grams carb)

• 6 oz real fruit juice or sports drink (20-25 grams carb)

• 1 c fruit smoothie (20-25 grams carb)

• Honey packet (15 grams carb)

During your workouts longer than 1 hour examples to work toward: **remember staying hydrated decreases GI distress

• 1 scoop drink mix + 32 ounces water such as Skratch Hydration, Crank E- Fuel, or Tailwind (20-25 grams carb)

• 2 scoop drink mix + 32 ounces water (40-50 grams carb)

• 6 energy chews such as Honey Stinger, ProBar Bolt, or Skratch (~45 grams carb)

• 1 energy gel such as Untapped, Honey Stinger, Maurten, or GU (20-25 grams carb)

Implement It

The key to training your gut is time and practicing at your race intensity and climate when you can. Here is what you can do to get started:

1. Start with your pre workout snack, determine if that is enough or too much, adjust the timing of fueling and hydration, and continue to tweak based on energy, tolerance, and workout goals. For workouts longer than one hour (& my morning workout crew), add in hydration and fuel from the “Start Here” column above and decide if this is appropriate for your performance goals. My fueling guide goes into how to support your body based on the goals of your upcoming session.

2. Evaluate your current hydration and fueling plan in comparison with your goal nutrition needs for your race duration. For example, if you are racing 3+ hours, your goal carbohydrate intake will be 60-90 grams of carbs/ hour. Your fluid and sodium intake is individual based on your sweat rate and sodium losses. A great place to start is 16 to 20 ounces/ hour + 300-500 mg/ hour (1000 mg/liter). The Nix Biosensor is an at home wearable device that can be useful to track your individual fluid/ electrolyte needs (USE CODE: Dana15Off).

3. Begin practicing your strategy 8-12 weeks out from race day. Fuel and hydrate to comfort in week 1. Gradually increase your carbs per hour by 5-10 grams each week until you reach desired carb intake per hour in one to two sessions per week.

4. Fuel and hydrate early and often. You can start fueling 15 to 20 minutes into your session to train your gut.

   *keep in mind being dehydrated when taking in concentrated chews, gels, bars, and gus can increase incidence of gastrointestinal distress.

5. Keep a food/training log to monitor what products are working well/ what you are enjoying and what is not working well.

6. More is not necessarily better. Find a sweet spot for carbohydrate intake that feels great for you within the 30-60 g/hour for races under 3 hours and 60-90 gram intake for 3+ hour races.

Keep in mind, just like training, not all days are treated equally; your fuel and hydration needs will vary from day to day. Adequate training of the gut with both carbohydrate and hydration leads to a less dramatic decrease of blood flow to the intestines with increased exercise intensities, which is important in preventing GI symptoms.

If you are chronically experiencing GI distress with increasing training duration and intensity, you may consider consulting a sports dietitian (that's me!) to find your optimal fueling and hydration technique. Also, check out my self-paced course on navigating GI issues.