How Carbohydrates Fuel Your Exercise (And Why You Shouldn't Cut Them) - Cooperative Extension: Food & Health - University of Maine Cooperative Extension

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How Carbohydrates Fuel Your Exercise (And Why You Shouldn’t Cut Them)

September 24, 2026 Nutrition, Physical Activity, Spoonful

If you’re like me, then you might also struggle with what to eat before exercising. Not eating enough might not provide the energy your body needs, but eating too much might make you feel too full or uncomfortable. Finding that sweet spot can certainly be a challenge. What if I told you that what you eat might matter more than how much you eat?

There are many people who are skeptical about carbohydrates. Some individuals choose to cut carbohydrates entirely from their diet because of the worry of weight gain.
While limiting carbs can be beneficial for specific medical conditions, like managing blood sugar in diabetes, cutting out carbohydrates is not best practice for everyone. Let’s dive into why carbohydrates are important for exercise.

The Science Behind the Fuel

I love the chemistry and biology aspects of food and nutrition, so I’ll share some of the niche stuff I’ve learned over the course of my undergraduate degree.

Your body has glycogen stores, essentially compartments where carbohydrates (sugars) are held. There are four classes of macromolecules in your body, carbohydrates being one of them. Carbohydrates are the easiest macromolecule for your body to turn into energy.

During exercise:

Your muscles pull glucose (sugar) out of the bloodstream and use it as energy.
As blood sugar drops, your body automatically senses this and triggers glycogen stores to release more sugar into the bloodstream.
The system is entirely automatic and keeps your energy steady while you exercise – cool, right?

Why Should I Fuel Up for Exercise?

Fueling appropriately can set you up for success. Your fueling plan doesn’t need to be perfect, but being aware of energy sources that prepare you for exercise can get you a physical and mental step ahead.

The most common example I hear today regarding fueling before exercise is fueling your car with gas. When your car is low on gas, you take it to the gas station, fill it up with gas, and your car is ready to do work again. When your body is low on energy, you take yourself to a location with food, eat the appropriate fuel before exercise, and your body is ready to do more work. Just as your car needs gas for the engine to run, your body needs carbohydrates for quick and responsive energy production.

How Should I Fuel Up for Exercise?

Your body is able to turn carbohydrates into energy relatively quickly while providing an adequate amount of energy for your exercise session (International Society of Sports Nutrition Position Statement on Nutrient Timing). Carbohydrates initially exist as a ring structure, but through a series of reactions, these ring structures get broken down into short chains. These short chains promote the movement of electrons that eventually stimulate ATP (energy) production. There are two types of carbohydrates I would like to talk about: simple and complex.

Simple Carbohydrates

Simple carbohydrates digest quickly and provide a short burst of energy. “Simple” means they have either one or two sugar molecules. This class of carbohydrate can be most effective for energy production if consumed between 15 to 60 minutes before exercise. Some examples of simple carbohydrates include:

Applesauce
English muffin with peanut butter
Fruit snacks
Whole grain cereal

Complex Carbohydrates

Complex carbohydrates digest more slowly than simple carbohydrates, but provide a more sustained energy level. “Complex” means they have more than two sugar molecules. This class of carbohydrate is most effective for energy production if consumed 2 to 4 hours before exercise. Complex carbohydrates include:

Brown rice
Oatmeal
Whole wheat pasta
Whole wheat tortillas

Tasty Recipes To Fuel Your Exercise

As someone who prefers to exercise before work in the morning, fueling with complex carbohydrates 2 to 4 hours before exercise is not always an option. So, more often than not, I choose a few simple carbohydrate snacks 30 minutes before my training session. A few of my favorite UMaine Extension recipes for early morning workouts include:

Try these recipes to fuel you 15 to 30 minutes before exercise:

Try these recipes to fuel you 2 to 4 hours before exercise:

Carbohydrates aren’t something to fear or criticise, they are an essential macronutrient your body needs to function. By intentionally timing your carbohydrate intake, you can help fuel your exercise effectively!

Resources

Author

Ethan DeMerchant is a fourth-year Human Nutrition and Dietetics student at the University of Maine. Ethan has also been working with Cooperative Extension since May of last year.