When to eat when exercising?

When to eat when exercising?

Written by: Aviva Rappaport , Jan 2022

Why fuel for exercise

Nutrition is an essential part of exercise performance. In addition to improved performance, fueling before and after physical activity can decrease the time it takes to recover (Rodriguez et al.). While it is important to be well hydrated and nourished, remember that you don’t need to stick to a rigid workout or nutrition schedule to get the most out of your physical activity (American Heart Association, 2015)!

Does fueling for exercise depend on the type of exercise?

Yes, and there are many different types of exercise! 

Aerobic exercise: Is exercise involving large muscle groups with an increased heart rate. Aerobic exercise can use fat, carbohydrates or protein as the energy source. 

  • Examples: running or cycling at a steady pace

  • Anaerobic exercise: Is similar to aerobic exercise, but the energy is used quickly and immediately which must come from glucose. It involves short, fast and intense exercise.

    • Examples: High-intensity interval training, sprint running or swimming events, weightlifting

    What is the difference between aerobic and anaerobic exercise?  Aerobic exercise means “with oxygen” where anaerobic means “without oxygen”. Aerobic exercises can become anaerobic. If you are running and you increase the intensity by beginning to sprint for 15 seconds, this can become anaerobic. 

    What should you eat before exercising?

    Eating before exercising can ensure you have enough energy for your workout. Some research suggests that eating before a workout helps to improve exercise performance (Ellis, 2020).  Everyone is different, but it is generally best to eat between 1 and 4 hours before exercising. The timing depends on how your body tolerates food and how quickly you digest it. It is important to consume carbohydrates with protein, and to hydrate with water prior to exercise (Mohr, 2019). 

    Eating foods that are high in fat such as doughnuts, pizza, and fried foods can impact your exercise performance. When these foods are consumed 2-3 hours before exercise, they can cause blood to flow to the digestive track and away from the muscles. 

    What you eat before you begin exercising depends on how long you plan to exercise for and what you had to eat previously. Low-intensity exercise such as walking for ~60 minutes doesn’t require eating in advance. Moderate exercise for more than 1 hour could benefit from eating in advance. For this type of exercise choose food high in simple carbohydrates and low in fibre so they are easier to digest. Fibre is digested slowly and may produce gas or bloating. If you’re looking to learn more about fibre, check out this past blog post to learn more!  Keep in mind that liquids are more easily digested than solids. If you’re planning to exercise in 30 minutes or less consider choosing a drink with carbohydrates (Academy of Nutrition and Dietetics, 2022a). 

    Carbohydrates are the main energy source in the body (during exercise and at rest). When we eat carbs, they are broken down into glucose. Glucose (sugar) is converted to a form of energy called glycogen which is stored in the body. During our workouts, we take glycogen and convert it back to glucose for our body to use. If we don’t have enough glycogen stores in the body, during a workout we will begin to break down protein to fuel or bodies leading to loss of muscle mass and fatigue. If you are interested in seeing how this looks visually, check out the figure below! 

    1) Photo by JÉSHOOTS from Pexels and 2) Image by Hey Rabbit from Noun Project

    Pre-exercise snack ideas (Academy of Nutrition and Dietetics, 2022a)

    • Granola or cereal bar
    • Low-fat yogurt with fruit
    • Oatmeal
    • Toast and a hard-boiled egg
    • Handful of nuts and dried fruit with more dried fruit than nuts
    • Bean Bark (Academy of Nutrition and Dietetics, 2022a)

    Should I eat during exercise?

    Whether you need to eat during exercise can depend on the individual length and intensity of the activity. For mild to moderate exercise or exercise less than 1 hour listen to your hunger cues to determine when and how much to eat (Government of Canada, 2021). If you are working out at a moderate to high intensity for more than 1 hour, the recommendation is to eat 30-60 g of carbohydrate per hour. When training for an endurance event such as a marathon or long distance cycling carbohydrates can help performance (Academy of Nutrition and Dietetics, 2022b). 

    During-exercise snack ideas (Academy of Nutrition and Dietetics, 2022b). 

    • Sport drinks or diluted fruit juice
    • Carbohydrate gels
    • Energy bars
    • Gummy candies
    • Banana
    • Plain mini bagel

    Remember to think about the temperature and how much you sweat. For low intensity activity in hot or humid conditions, consider having 5-9 g of carbohydrate per 1 cup of water. For high intensity exercise consider 14-18 g of carbohydrate per 1 cup of water. Including 100-200 mg of sodium and 30-60 mg of potassium per cup of water are important too in hot/humid conditions (Academy of Nutrition and Dietetics, 2022a)!

    Unsure of what 5-9 g of carbohydrate looks like or what 100-200 mg of sodium would be? Check out this previous blog article on how to read food labels to learn more!

    What should you eat after exercising?

    After exercising your body needs to replenish the nutrients and fluid lost. When you exercise longer than 90 minutes and you plan to train hard again the same day, it is important to have a snack that is high in carbohydrate and protein. 

    Protein helps to repair and grow muscles (Academy of Nutrition and Dietetics, 2022c). While carbohydrates help us restore the glycogen that we used in our workout. This is especially important if you are training everyday or even multiple times per day. 

    Post-exercise snack ideas (Academy of Nutrition and Dietetics, 2022c). 

  • Low-fat chocolate milk 
  • Smoothie with berries, banana, soy beverage or low-fat milk
  • Greek yogurt with Bean Bark
  • Turkey sandwich on whole grain bread
  • Low-fat yogurt with berries

  • Be aware of food and drinks which are marketed as performance enhancing. These products are often high in sugar, sodium, and saturated fat (Government of Canada, 2021). 

    To summarize, nutrition is an important component to exercise performance. Carbohydrates are the primary source of energy during exercise. Going into exercise without adequate carbohydrate can lead to muscle fatigue and muscle breakdown (which is not what we want with exercise). Having a pre-exercise snack with water before exercise and/or recovering with a meal or snack with water after exercise can help prevent this. 



    Academy of Nutrition and Dietetics. (2022a). Fueling Ice Hockey Players. https://www-nutritioncaremanual-org.proxy3.library.mcgill.ca/client_ed.cfm?ncm_client_ed_id=389

    Academy of Nutrition and Dietetics. (2022b). Fueling Track and Field Athletes. https://www-nutritioncaremanual-org.proxy3.library.mcgill.ca/client_ed.cfm?ncm_client_ed_id=395

    Academy of Nutrition and Dietetics. (2022c). Nutrition For Strength Athletes. https://www-nutritioncaremanual-org.proxy3.library.mcgill.ca/client_ed.cfm?ncm_client_ed_id=399

    Academy of Nutrition and Dietetics. (2022a). How much carbohydrate do I need before Exercise. Academy of Nutrition and Dietetics. https://www-nutritioncaremanual-org.proxy3.library.mcgill.ca/topic.cfm?ncm_category_id=25&lv1=274893&lv2=255684&lv3=272512&ncm_toc_id=272512&ncm_heading=Resources

    Academy of Nutrition and Dietetics. (2022b). Should I Eat During Exercise? Academy of Nutrition and Dietetics. https://www-nutritioncaremanual-org.proxy3.library.mcgill.ca/topic.cfm?ncm_category_id=25&lv1=274893&lv2=255684&lv3=272513&ncm_toc_id=272513&ncm_heading=Resources

    Academy of Nutrition and Dietetics. (2022c). What Should I Eat for Recovery After Exercise? https://www-nutritioncaremanual-org.proxy3.library.mcgill.ca/topic.cfm?ncm_category_id=25&lv1=274893&lv2=255684&lv3=272514&ncm_toc_id=272514&ncm_heading=Resources

    American Heart Association. (2015). Food as Fuel Before, During, and After Workouts. https://www.heart.org/en/healthy-living/healthy-eating/eat-smart/nutrition-basics/food-as-fuel-before-during-and-after-workouts

    Ellis, E. (2020). How to Fuel Your Workout. https://www.eatright.org/fitness/exercise/exercise-nutrition/how-to-fuel-your-workout

    Government of Canada. (2021). Physical activity and healthy eating. Canada’s food guide. https://food-guide.canada.ca/en/tips-for-healthy-eating/physical-activity-healthy-eating/

    Mohr, C., R. (2019). Timing Your Pre- and Post-Workout Nutrition. Academy of Nutrition and Dietetics. https://www.eatright.org/fitness/exercise/exercise-nutrition/timing-your-pre-and-post-workout-nutrition

    Rodriguez, N. R., Di Marco, N. M., & Langley, S. American College of Sports Medicine position stand. Nutrition and athletic performance. (1530-0315 (Electronic)). 

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