Carbs and Exercise - The Power of Carbs in Fueling Fitness

If you’re an athlete, improving performance is likely top of mind. And what you eat plays a foundational role in how well you perform.

Carbohydrates are the body’s most efficient fuel source during exercise, yet they are often misunderstood and unfairly labeled as “bad.” In reality, carbohydrates are essential for health and performance, especially for athletes with higher energy demands.

In this article, we’ll break down the science behind carbs and exercise and explain when and how to use carbohydrates to fuel your workouts more effectively.

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 the primary source of fuel for energy production. ^[1]The mitochondria are our cells' energy centers; thus, fueling them is a priority.

There are two types of carbs: simple and complex. These labels describe how the carbohydrates are structured and how quickly the body breaks them down for energy. Both types play important roles and should be included regularly in a balanced diet, both for long-term health and athletic performance.

Simple carbs

These carbohydrates break down quickly, making them an ideal fuel source during exercise or when consumed 30 to 90 minutes before a workout^[2].

Examples of simple carbs include:

• Fruit
• Milk
• Energy chews, gels, drinks

Complex carbs

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

Complex carbs are:

• 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.

In general, higher-intensity and longer-duration exercise increases carbohydrate requirements, though there are some nuances to that rule. This is important to know because if you’re doing the type of exercise that uses more carbs, you’ll want to make sure to top off your glycogen stores.^[5]

Low-intensity exercise

Low-intensity exercise, such as walking, slow jogging, and yoga, primarily uses fat rather than carbs. Your body will pull its 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 such as running, fast cycling, and heavy weight lifting, glycogen stores and blood glucose are primarily used 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 activities lasting more than two hours, even at a lower intensity, your body will still rely on stored carbohydrates whenever possible. When glycogen stores become depleted, the body shifts toward using fat for energy.

If carbohydrates are not adequately replenished, this shift can lead to reduced energy, declining performance, and, over time, increased muscle breakdown.

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 your workout lasts less than 60 minutes, you likely won't need additional carbohydrates during exercise. But for sessions longer than an hour, or when training in challenging conditions such as extreme heat, cold, or humidity, consuming 30 to 60 grams of carbohydrates per hour is generally recommended.

Choose carbs from soft fruit, gels, chews, or liquids, 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

Timing your carbohydrate intake before exercise also matters. A general guideline is to eat a full, carbohydrate-rich meal three to four hours before your workout, a higher carbohydrate snack about two hours before, and a small, easy-to-digest snack providing about 30 grams of carbohydrates about 30 minutes prior to exercise.^[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: Two rice cakes with a thin spread of peanut butter and a drizzle of honey or a few sliced bananas.
• Apple with almond butter: A medium apple with one 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 support your mitochondria for optimized performance.

Endurance training increases the size and number of mitochondria, helping your muscles use energy more efficiently. Over time, this means less reliance on glycogen and glucose and more sustained energy, stamina, and endurance. ^[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 and stimulate a mitochondrial recycling process called mitophagy.^[11] Learn more about Mitopure, its benefits, and how it may complement your fitness routine.

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