Carbs and exercise - The power of carbs in fueling fitness

Carbs and exercise go hand-in-hand, especially at higher intensities. Learn when to consume carbohydrates during exercise and why you should.

Carbs for fitness
What to know
  • Carbohydrates are crucial for athletes and are the most efficient source to fuel the mitochondria, the body’s energy center of the cell

  • There are simple and complex carbs, where simple carbs provide quick energy and complex carbs provide longer-lasting energy

  • The body utilizes carbs and protein for energy at different amounts depending on the exercise intensity and duration

  • Daily carbohydrate needs for athletes range from 6-10 grams per kilogram of body weight per day to upwards of 10-12 grams per kilogram prior to competition

  • Other ways to optimize mitochondrial performance include endurance training and supplementing with Urolithin A, the primary ingredient in Mitopure®

You’re probably motivated to improve your performance if you're an athlete. Carbs are the most efficient fuel source utilized during exercise, but there is a common misconception that carbs are bad for you.

The truth is that many healthy carbs are needed in the diet, especially if you’re an athlete.

In this article, we’ll dive into the science of carbs and exercise and when you should consume carbs during workout sessions.

What are carbs?

Carbs, or carbohydrates, are one of the three macronutrients in our diet. The term “macro” in “macronutrients” means they have a large chemical structure. We also need these nutrients in large amounts. This is especially true if you are an athlete and want to maximize your nutrition for training.

Carbs should make up the bulk of your diet, as our mitochondria use them as their primary source of fuel for energy production. [1]The mitochondria are our body’s energy center of our cells; thus, fueling them is a priority.

There are two types of carbs for exercise — simple and complex. These terms refer to their chemical structure and whether they can be broken down simply or if it is more complicated. Both should be incorporated regularly into your diet.

Simple Carbs and sugars

Simple carbs

These are the types of carbohydrates during exercise you can have to refuel, and they can also be eaten 30-90 minutes before exercise[2].

  • Fruit
  • Milk
  • Energy chews, gels, drinks
Complex carbs

Complex carbs

Complex carbs are a slower-digesting, more sustainable energy source that is best to consume at least 2 hours before exercise.[3]

  • Pasta
  • Bread
  • Rice
  • Legumes
  • Starchy veggies - potatoes and squash

All carbs are converted into glucose or glycogen, the storage form of glucose in the liver and muscle tissue. This stored glucose is then reserved for later use, such as during exercise.[4]

A range of 6-10 grams of carbohydrate per kilogram of body weight is recommended for athletes per day.

Carbs and exercise

If you’re trying to make the most of your training, it’s essential to know how your body utilizes carbohydrates during different workouts. This can help ensure your mitochondria are properly fueled to have the best performance possible.

During all types of exercise, the body breaks down a combination of carbs and fat for energy. This is called substrate utilization. The percentage of substrate utilized, i.e., carbs and fats, depends on the intensity and duration of exercise.

A golden rule to live by - the higher the intensity and longer the duration, the more carbs you will generally need (with a few caveats). This is important to know because if you’re doing the type of exercise where you will be utilizing more carbs, you’ll especially want to top off your glycogen stores.[5]

Low-intensity exercise

Low-intensity exercise such as walking, slow jogging, and yoga utilize more fat than carbs. Your body will pull your body’s fat stores for energy, preserving your muscle and liver glycogen. This means these exercises don’t require as much carb intake before, during, and after because they’re not depleting your glycogen and, therefore, your energy stores.

High-intensity exercise

For high-intensity workouts of short or long duration up to 2 hours, such as running, fast cycling, and heavy weight lifting, glycogen stores and blood glucose are primarily utilized as quick-acting energy sources. This means your carb consumption will be even more important to fuel these more intense exercises.


Endurance exercise

If you are training for endurance of 2 hours or more, even at a lower intensity, your body will still try to utilize its stored carbs for fuel whenever possible. If you deplete all of your glycogen stores, your body will return to relying on body fat for energy.

This can lead to reduced energy, impaired performance, and eventually, muscle breakdown if you aren’t properly replenishing your carb stores.

How many carbs do you need?

Daily carbohydrate needs

Your daily carbohydrate needs can vary depending on your training schedule. Generally, a range of 6-10 grams of carbohydrate per kilogram of body weight is recommended for athletes per day.[6]

For a heavy training or endurance competition day, upwards of 10-12 grams of carbs per kilogram may be needed for 36-48 hours leading up to the event.[7]

Carbohydrates during exercise

If you are exercising for less than 60 minutes, you don’t really need to have any carbs during your workout. Consuming 30-60 grams of carbs during workout sessions every hour is recommended if exercising longer than an hour or under challenging conditions such as extreme cold, heat, or humidity.

Your carb intake during exercise may be in the form of a soft fruit, gel, chew, or liquid, depending on your preference.

Carbohydrates after exercise

While we more often think of protein in terms of post-exercise muscle recovery and joint health, replenishing carbohydrates also helps you further repair and rebuild muscle.[8]

After exercise, you should consume 1.0-1.5 grams of carbs per kilogram of body weight during the first half hour and every 2 hours for 4-6 hours to replenish liver and muscle glycogen stores.

Carb timing before exercise

It’s also important to time your carb intake correctly before exercise. A general guideline is to eat a full, carbohydrate-rich meal 3-4 hours before exercise, a higher carbohydrate snack 2 hours before, and about 30 grams of a smaller, easy-to-digest snack 30 minutes before.[9]

A few ideas for pre-workout snacks with 30 grams of carbs:

  • Greek yogurt and berries: try a small serving (about ¼ cup) of plain Greek yogurt with mixed berries
  • Rice cakes with peanut butter: 2 rice cakes with a thin spread of peanut butter and a drizzle of honey or a few sliced bananas.
  • Apple with almond butter: 1 medium apple with 1 tablespoon of almond butter sprinkled with cinnamon

Fuel Your mitochondria for optimal performance

In addition to the almighty carb, there are other simple ways to fuel your mitochondria for optimized performance.

Endurance training sessions can increase mitochondrial size and number, which results in less muscle glycogen and glucose utilization. This means over time, you’ll eventually be able to go for longer with more energy and stamina.[10]

Urolithin A, the principal ingredient in Mitopure®, offers another way to help your mitochondria. It is clinically proven to improve markers of mitochondrial health, such as muscle strength and endurance. Learn more about Mitopure®, its benefits, and how it may complement your fitness routine.

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Melissa Mitri, MS, RD

Dietitian-Nutritionist, and Health Content Writer

Dr. Emily Werner

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Dr. Emily Werner


  1. Pizzorno J. Mitochondria-Fundamental to Life and Health. Integr Med (Encinitas). 2014 Apr;13(2):8-15. PMID: 26770084; PMCID: PMC4684129.

  2. Holesh JE, Aslam S, Martin A. Physiology, Carbohydrates. [Updated 2023 May 12]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-. Available from:

  3. Ferretti F, Mariani M. Simple vs. Complex Carbohydrate Dietary Patterns and the Global Overweight and Obesity Pandemic. Int J Environ Res Public Health. 2017 Oct 4;14(10):1174. doi: 10.3390/ijerph14101174. PMID: 28976929; PMCID: PMC5664675.

  4. Hearris MA, Hammond KM, Fell JM, Morton JP. Regulation of Muscle Glycogen Metabolism during Exercise: Implications for Endurance Performance and Training Adaptations. Nutrients. 2018 Mar 2;10(3):298. doi: 10.3390/nu10030298. PMID: 29498691; PMCID: PMC5872716.

  5. Mul JD, Stanford KI, Hirshman MF, Goodyear LJ. Exercise and Regulation of Carbohydrate Metabolism. Prog Mol Biol Transl Sci. 2015;135:17-37. doi: 10.1016/bs.pmbts.2015.07.020. Epub 2015 Aug 20. PMID: 26477909; PMCID: PMC4727532.

  6. Hassapidou MCarbohydrate requirements of elite athletesBritish Journal of Sports Medicine 2011;45:e2.

  7. Podlogar T, Wallis GA. New Horizons in Carbohydrate Research and Application for Endurance Athletes. Sports Med. 2022 Dec;52(Suppl 1):5-23. doi: 10.1007/s40279-022-01757-1. Epub 2022 Sep 29. PMID: 36173597; PMCID: PMC9734239.

  8. Margolis LM, Allen JT, Hatch-McChesney A, Pasiakos SM. Coingestion of Carbohydrate and Protein on Muscle Glycogen Synthesis after Exercise: A Meta-analysis. Med Sci Sports Exerc. 2021 Feb 1;53(2):384-393. doi: 10.1249/MSS.0000000000002476. PMID: 32826640; PMCID: PMC7803445.

  9. Kerksick CM, Arent S, Schoenfeld BJ, Stout JR, Campbell B, Wilborn CD, Taylor L, Kalman D, Smith-Ryan AE, Kreider RB, Willoughby D, Arciero PJ, VanDusseldorp TA, Ormsbee MJ, Wildman R, Greenwood M, Ziegenfuss TN, Aragon AA, Antonio J. International society of sports nutrition position stand: nutrient timing. J Int Soc Sports Nutr. 2017 Aug 29;14:33. doi: 10.1186/s12970-017-0189-4. PMID: 28919842; PMCID: PMC5596471.

  10. Fujimoto T, Kemppainen J, Kalliokoski KK, Nuutila P, Ito M, Knuuti J. Skeletal muscle glucose uptake response to exercise in trained and untrained men. Med Sci Sports Exerc. 2003 May;35(5):777-83. doi: 10.1249/01.MSS.0000065070.49295.C0. PMID: 12750587.


The information in this article is for informational purposes only and should not be taken as medical advice. Always consult with your medical doctor for personalized medical advice.

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Melissa Mitri, MS, RD

Dietitian-Nutritionist, and Health Content Writer

Dr. Emily Werner

Reviewed by

Dr. Emily Werner


Knowledge is power
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These statements have not been evaluated by the Food and Drug Administration. This product is not intended to diagnose, treat, cure or prevent any disease. References: *Nutrition studies: 500mg Mitopure® have been shown to (1) induce gene expression related to mitochondria function and metabolism and (2) increase the strength of the hamstring leg muscle in measures of knee extension and flexion in overweight 40-65 year olds. Data from two randomized double-blind placebo-controlled human clinical trials. **Nutrition NOURISH Study: 500mg Mitopure® have been shown to deliver at least 6 times higher Urolithin A plasma levels over 24 hours (area under the curve) than 8 ounces (240ml) of pomegranate juice in a randomized human clinical trial.

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