When it comes to building muscle, protein is usually the nutrient that gets all the attention. Protein shakes, high-protein snacks, and “protein-packed” meals dominate the fitness industry, leading many people to believe that protein alone is the key to muscle growth and recovery.
While protein is absolutely essential for repairing and building muscle tissue, carbohydrates play an equally important role in helping your body maximise muscle growth, exercise performance, and recovery. In fact, cutting carbohydrates too low can actually reduce your ability to build muscle and get the results you want from your training.
If you are spending hours in the gym but not seeing the progress you expected, your carbohydrate intake may be one of the missing pieces.
Carbohydrates: Your Body’s Preferred Fuel Source
Carbohydrates are the body’s primary source of energy, especially during high-intensity exercise such as resistance training, weightlifting, sprinting, and circuit-style workouts. When you eat carbohydrates, your body breaks them down into glucose, which is then stored in your muscles and liver as glycogen.
Glycogen acts as a readily available fuel source during exercise. The harder and more intensely you train, the more your body relies on glycogen to perform at its best.
When carbohydrate intake is too low, glycogen stores become depleted. This can leave you feeling fatigued, weaker during workouts, and slower to recover afterwards. Over time, consistently low glycogen levels may negatively impact muscle growth and performance.
The Relationship Between Carbohydrates and Protein
One of the lesser-known roles of carbohydrates is their ability to support how your body uses protein.
Research has shown that low glycogen stores can increase nitrogen losses from the body. Nitrogen is a key component of amino acids, which are the building blocks of protein. When nitrogen losses increase, your body becomes less efficient at maintaining the ideal environment for muscle repair and growth.
This means that even if you are eating enough protein, inadequate carbohydrate intake may still compromise muscle recovery and development.
Carbohydrates also help to “spare” protein. When your body has enough carbohydrate available for energy, protein can be used for its primary purpose — building and repairing muscle tissue — rather than being broken down for fuel.
Why Low-Carb Diets Can Affect Gym Performance
Low-carbohydrate diets have become increasingly popular for weight loss and general health. While some people may benefit from reducing highly processed carbohydrates, excessively restricting carbohydrate intake is usually not ideal for individuals engaging in regular resistance training or high-intensity exercise.
Research suggests that low glycogen availability can particularly affect type II muscle fibres, also known as fast-twitch muscle fibres. These fibres are responsible for explosive movements such as heavy lifting, jumping, sprinting, and power-based exercise.
Fast-twitch muscle fibres rely heavily on glycogen for fuel. When glycogen stores are low, these fibres cannot perform optimally, which may lead to:
- Reduced training intensity
- Poorer strength output
- Earlier fatigue during workouts
- Reduced power and endurance
- Slower recovery between sessions
Over time, this can limit muscle-building potential and make it harder to progressively improve performance in the gym.
Carbohydrates and Recovery
The role of carbohydrates does not stop once your workout ends. Post-workout nutrition is important for recovery, and carbohydrates play a major role in this process.
After exercise, your muscles are more efficient at taking up glucose to replenish glycogen stores. Consuming carbohydrates after training can help:
- Restore muscle glycogen levels
- Reduce feelings of fatigue
- Support recovery between workouts
- Improve energy levels
- Assist immune system function
Intense exercise can temporarily suppress aspects of the immune system, particularly when training volume is high. Adequate carbohydrate intake may help reduce this effect and support overall recovery.
Pairing carbohydrates with a source of protein after exercise can be particularly beneficial for muscle repair and replenishment.
How Much Carbohydrate Do You Need?
Carbohydrate needs vary depending on factors such as training intensity, body size, exercise goals, and overall activity levels.
For many active individuals, a general guideline is approximately 4–7g of carbohydrate per kilogram of body weight per day. Athletes or individuals completing very high training loads may require more.
Rather than consuming most carbohydrates in one sitting, spreading intake evenly throughout the day can help maintain energy levels, support recovery, and improve overall performance.
Choosing high-fibre, minimally processed carbohydrate sources most of the time can also support gut health, heart health, and long-term wellbeing.
Example of a Balanced Day of Carbohydrate Intake
Breakfast
2 slices wholegrain toast topped with 2 poached eggs and 40g cheddar cheese, served with sautéed spinach and tomato
Morning Snack
Carrot, celery, and capsicum sticks with 30g peanut butter
Lunch
Wholegrain crackers topped with avocado and sauerkraut
Afternoon Snack
200g yoghurt with fresh fruit
Dinner
1 cup quinoa served with 100g grilled salmon and Asian vegetables
Take Home Message
Protein may be the nutrient most associated with muscle growth, but carbohydrates are equally important for fuelling training, supporting recovery, preserving muscle tissue, and helping you perform at your best.
Completely removing or severely restricting carbohydrates can negatively affect energy levels, gym performance, recovery, and muscle development — particularly for those engaging in regular resistance training or high-intensity exercise.
Instead of fearing carbohydrates, focus on choosing quality carbohydrate sources and incorporating them strategically throughout the day to support your health and fitness goals.
Need Support with Sports Nutrition?
Whether your goal is building muscle, improving sports performance, increasing energy, or creating a sustainable approach to nutrition, personalised advice can make a significant difference.
At Feed Your Future Dietetics, we provide evidence-based nutrition support tailored to your individual goals, lifestyle, and training demands. With over 10 years of experience and voted one of the best dietitians in Canberra in 2025, we are passionate about helping clients achieve long-term, realistic results.
To learn more or book an appointment, visit Feed Your Future Dietetics today.
