How Many Carbs Before a Workout Should You Eat for Endurance Training?

The way the training goes usually comes down to one basic thing: what you eat before the workout. Athletes spend hours planning training blocks - but pre-workout meals somehow get left to chance. You may snatch a banana on the way out. You may skip breakfast entirely. Or you eat a pasta dinner so heavy it's still with you at sunrise.

Carbohydrates are your muscles' go-to energy source during endurance exercise. Get your carb intake right, and you keep your stamina and pace steady. So, how many carbs do you need before a workout?

Why Carbohydrates Are The Foundation of Endurance Performance

When you run, cycle, swim, or row at moderate to high intensity, your body mainly burns glycogen, the carbs stored in your muscles and liver. Fat burns too, but it’s too slow to meet the demands of sustained, intense effort. Glycogen burns fast and efficiently. That’s the whole point.

But the problem is that your glycogen stores are limited. Even trained athletes might have enough for only 90 to 120 minutes of vigorous exercise. Once it runs out, so does your energy. Fatigue creeps in early. You slow down. Decision-making becomes foggy. That crash has a name - "bonking," or "hitting the wall" - and it's mostly avoidable if you plan your fueling.

When you eat carbohydrates before a workout, you spike your blood sugar and refill those glycogen stores. It's not about eating more - it's about eating strategically.

How Many Carbs Should You Eat Before a Workout?

There's a simple rule to follow: aim for 1 to 4 grams of carbohydrate per kilogram of body weight, consumed in the 1 to 4 hours before your session. Base how much you need on how long and hard the workout will be. Here's what that looks like in practice:

• Workouts under 60 minutes: No need to go overboard. A light snack with 15-30 grams of carbs - like a banana or some oatmeal - does the job for most people.

• Sessions lasting 60 to 90 minutes: A decent pre-workout meal is advisable. Aim for 30-60 grams of carbs, plus add some protein. This supports muscles and holds off fatigue.

• Sessions of 90 minutes or more: This is where you really need carbs beforehand. Shoot for 60-100 grams or more, making sure you eat early enough to digest it.

Take a 70 kg (154lbs) athlete preparing for a two-hour training. They should eat 70-140 grams of carbs beforehand, which is more food than you might expect and requires planning, not just being thrown together at the last minute.

Keep in mind, everyone's different. Body mass, training experience, how fast your metabolism runs, and just how tough your workout is all affect your needs. Think of the guidelines as a starting point, then adjust them as you go based on how your body feels.

Timing Is Everything - When to Eat Your Carbs

3 to 4 hours before training is the ideal window for a full pre-workout meal. At this point, your digestive system has time to process complex carbohydrates (brown rice, sweet potato, oats, whole grain bread), some protein, and low-fat foods. That sets the foundation for your glycogen.

If you're eating 1 to 2 hours before the session, keep it lighter, easier to digest, and lower in fiber. A bowl of plain oatmeal, white rice, or fruit with yogurt works well here. Your body has less time to process, so you want quick energy without weighing yourself down.

If there’s only 30-60 minutes left, stick to fast carbs: a banana, a handful of dates, a rice cake. They'll get into your bloodstream quickly and clear out fast. Avoid lots of fiber, heavy fats, or ultra-processed foods in that window to avoid GI distress.

The simple rule says: the closer you are to training, the simpler your carbs should be.

Best Carb Choices for Endurance Athletes

Not all carbs are equal, and context matters. If you're eating 3 to 4 hours before training, go for complex, whole-food options: oats, sweet potatoes, brown rice, quinoa, or whole-grain bread. These release energy slowly and help hold your blood sugar steady for the workout ahead.

As you get closer to exercise (1 to 2 hours before), switch to lower-fiber sources: white rice, plain pasta, white bread, and super-ripe bananas. Pair with a moderate portion of lean protein - chicken, fish, eggs, or Greek yogurt - so you're supporting your muscles without bogging down digestion.

Skip high-fat foods and large servings of raw veggies right before exercising. Fat slows down how quickly your stomach empties. Too much fiber right before you move can draw water into your gut, leading to cramps.

This is where meal prep services like Ideal Nutrition can help. We offer balanced, ready-made pre-workout meals so you don’t need to calculate every gram or calorie (we do this for you!). A well-constructed pre-workout meal is ready when you need it.

Pre-Workout Carb Mistakes to Avoid

Some athletes skip carbs entirely for fat adaptation. That can work for easy, low-intensity days. But if you're pushing hard, fat just can't cover for glycogen at high intensity.

Eating too much right before your workout is just as bad. A heavy meal 30 minutes out often leads to cramps or nausea. Save bigger meals for earlier.

Relying on gels or sports drinks alone is fine while you're training or racing, but in the hours before exercise, actual food builds a better base for glycogen.

Fueling differently in training versus competition is a mistake that surprises many athletes. Race day is not the time to introduce a new pre-workout meal. Whatever you plan to eat before a key event should be practiced in training first. 

Conclusion

To sum up, aim for 1-4 grams of carbs per kg of body weight in the 1-4 hours before your session starts. Scale the duration of your workout. Select the type of carbs to be used at the right time window. Most importantly, don't make it too difficult on yourself so that fueling becomes a habit and not an afterthought. Don't chase perfection. Practice being ready more often than not - athletes who get it right most of the time will always outlast those who get it right sometimes.