Few nutrients have been as publicly prosecuted as carbohydrates. They’ve been blamed for weight gain, energy crashes, inflammation and apparently everything short of bad weather. But the reality is a bit less dramatic. Truth is, carbohydrates are the body’s preferred fuel source—and for anyone who trains with any regularity, getting them right is an important nutritional decision to make.
For more on the food myths that have been quietly undermining fitness goals, this piece on muscle-building lies about food is worth a read.
What Are Carbohydrates?
Carbohydrates are one of the three primary macronutrients and they serve as the body’s most readily available source of energy. When consumed, they are broken down into glucose, which is used immediately for fuel, stored in the muscles and liver as glycogen for later use, or converted to fat when consumed in excess of what the body needs. They are found in a wide range of foods from wholegrains, fruits and vegetables to refined foods like bread, pasta and sugar.
Are Carbohydrates Important for Fitness?
The question for active people isn’t really whether carbohydrates matter. It’s how much, when and from what sources. Glycogen, the form carbohydrates take once stored in the muscles and liver, is what the body draws on during moderate to high-intensity exercise. How well those stores are maintained has a direct bearing on training quality and recovery.
Here’s a way to think of it: skipping carbohydrates when you train regularly is a bit like cutting the budget on the department that’s keeping the whole operation running.
How Carbs Fuel Your Workouts
Carbs power specific physiological processes that determine how well you train.
- Glycogen availability drives performance. During moderate to high-intensity exercise, the body runs predominantly on muscle glycogen. When stores are adequate, output is higher and fatigue sets in later.
- Blood glucose supports sustained effort. Carbohydrates consumed before or during training maintain blood glucose levels. This is what keeps the brain and working muscles supplied with energy throughout the session.
- Glycogen replenishment accelerates recovery. Post-workout carbohydrates restore depleted muscle glycogen, reducing recovery time and preparing the body for the next training session.
- Carbs spare muscle protein. When carbohydrate availability is sufficient, the body is less likely to break down muscle protein for energy, which matters both during training and during periods of caloric restriction.
Simple vs Complex Carbohydrates: What’s the Difference?
Simple carbohydrates are made up of one or two sugar molecules and are digested quickly, producing a rapid rise in blood glucose. They’re found naturally in fruit and dairy, and in less useful forms in processed foods, sweets and sugary drinks.
Complex carbohydrates contain longer chains of sugar molecules, digest more slowly and provide a more sustained release of energy. Found in wholegrains, legumes and starchy vegetables, this makes them the better default choice for most meals.
Simple carbohydrates are not universally superior, but in the window before and during training, their speed of digestion is an asset. Complex carbohydrates, on the other hand, serve the rest of the day better, as they provide the sustained energy release that keeps blood glucose stable between meals and training sessions.
How Much Carbohydrates Do You Need?
General guidelines recommend 3 to 5 grams of carbohydrate per kilogram of bodyweight per day for moderately active individuals, rising to as much as 8 grams for those training at high volume or intensity. For those who are not as active, requirements sit lower and personal factors mean any figure should be treated as a starting point and adjusted from there. The more useful approach is to start with a moderate intake, monitor training performance and recovery, and adjust from there.
Factors That Influence Requirements
Carbohydrate needs are not fixed and several variables shift the requirement meaningfully in either direction.
- Training intensity. Higher-intensity training relies more heavily on glycogen, increasing carbohydrate requirements relative to lower-intensity or steady-state activity.
- Training volume. More sessions per week or longer sessions deplete glycogen stores more significantly, which increases total daily carbohydrate needs.
- Body composition goals. Someone in a caloric surplus for muscle building has different carbohydrate needs from someone in a deficit for fat loss, even if training volume is identical.
- Training timing. People who train early in the morning in a fasted state have different pre- and post-workout carbohydrate priorities from those training in the afternoon after several meals.
- Individual metabolism. Insulin sensitivity, metabolic rate and body composition all influence how efficiently carbohydrates are used and stored. This means two people on identical programmes may have meaningfully different needs.
- Sport or activity type. Endurance athletes have higher carbohydrate needs than strength athletes, whose training is shorter and more explosive in nature.
Carbs for Muscle Building and Bulking
If you’re in a building phase, this is not the time to be cautious with carbohydrates. Prioritise complex sources like oats, rice and sweet potato across your main meals to keep glycogen stores consistently topped up, and add a faster-digesting carbohydrate alongside protein in the post-workout window to take advantage of the insulin response that supports muscle repair.
Carbs When Cutting and Losing Body Fat
When cutting, the instinct is to slash carbohydrates as far as possible, but the right approach is less clear-cut than that. Our advice is to keep complex carbohydrates in the meals closest to your training sessions, where they’ll be used rather than stored, and pull back more in the sedentary parts of the day. This protects training quality and muscle mass while still creating the deficit needed for fat loss.
Carbs: Pre- and Post-Workout
Pre-workout, aim for a meal containing complex carbohydrates one to three hours before training, something like oats, rice or wholegrain bread alongside a protein source. If time is short, a banana or a small amount of a faster-digesting carbohydrate 30 minutes out will do the job. Post-workout, pair carbohydrates with protein within the first hour to restore glycogen and support muscle repair. The specifics matter less than the habit of doing it consistently.
Best Sources of Carbohydrates for Fitness
Not all carbohydrate sources serve fitness goals equally. The following are among the most useful sources to build a diet around.
- Wholegrains (oats, brown rice, quinoa, wholegrain bread): Slow-digesting and rich in fibre, these provide sustained energy and support consistent blood glucose levels across the day.
- Starchy vegetables (sweet potato, regular potato, corn): Nutrient-dense and versatile, these are among the most useful carbohydrate sources for athletes and active individuals.
- Legumes (lentils, chickpeas, black beans): A dual source of carbohydrate and plant-based protein, legumes digest slowly and support satiety alongside energy provision.
- Fruit (bananas, berries, oranges, dates): Natural sugars paired with fibre, vitamins and antioxidants make fruit a strong choice, with faster-digesting options like bananas and dates being particularly useful around training.
- Dairy (milk, yoghurt): A source of carbohydrate, protein and calcium that works well as part of a pre- or post-workout meal.
- Sports nutrition products (gels, bars, isotonic drinks): Useful in specific training contexts where rapid carbohydrate delivery is the priority. However, do note that they should not be seen as substitutes for whole food sources across the rest of the day.
Do You Need to Avoid Sugar and Refined Carbohydrates?
The short answer is no, but context matters. Sugar and refined carbohydrates are not inherently harmful in the quantities most active people consume them, and demonising them entirely can produce more dietary anxiety than better results.
It is healthier to distinguish between refined carbohydrates and faster-digesting whole food sources that happen to contain natural sugars. A banana or a serving of fruit around training delivers carbohydrates together with fibre, vitamins and minerals. Thus, where it makes sense to be more mindful is with refined carbohydrates and added sugars, which deliver glucose without much else alongside it. Whole food sources like fruit are a different conversation entirely.
Common Carb Mistakes That Could Be Hurting Your Fitness Progress
Not Eating Enough Carbs to Support Training
Training on chronically low carbohydrate intake is like trying to drive a long distance on an empty tank and being surprised when the car stops. Glycogen depletion reduces training output, accelerates fatigue and impairs recovery. It limits progress regardless of how consistent the programme is.
Eating Most of Your Carbs Without Considering Training Demands
Consuming carbohydrates without any consideration of when and how the body needs them is a missed opportunity. Concentrating intake around training, especially in the pre- and post-workout windows, produces better performance and recovery outcomes than distributing carbohydrates randomly across the day.
Cutting Carbs Too Aggressively
A moderate carbohydrate reduction can support fat loss without compromising training. An aggressive cut tends to take performance with it, which reduces the training stimulus needed to preserve muscle.
Wondering whether you can build muscle and lose fat at the same time? We’ve looked into it.
Assuming All Carbs Are Unhealthy
Classifying carbohydrates as a category as unhealthy ignores the significant nutritional difference between oats and a bag of sweets. Whole food carbohydrate sources are among the most nutrient-dense foods available. The quality of the source should be kept in mind.
Ignoring Portion Sizes
Carbs consumed in excess of what the body can use or store as glycogen are converted to fat, which is where the association between carbs and weight gain comes from. Portion awareness, notably around less active periods of the day, is what keeps carbohydrate intake working for body composition.
Focusing on Carbs While Overlooking Total Calories and Protein
Carbohydrate intake doesn’t exist in isolation. Total caloric intake and adequate protein are the two variables that have the greatest influence on body composition, and obsessing over carbohydrate content while neglecting either of those tends to produce frustrating results regardless of how carefully the carbs are managed.
Carbs Contribute to Your Fitness Goal
Carbohydrates are not the enemy of a good physique or a high-performing body. Used well, they are one of the more powerful tools available for improving training output, supporting recovery and reaching body composition goals more efficiently. The key is understanding how much you need, when to consume them and which sources to prioritise—and then building those habits consistently.
At FITLUC, our personal training trials include nutritional guidance tailored to your training goals, whether that’s building muscle, losing fat or improving performance. If you’d like support getting your nutrition working alongside your training rather than in spite of it, get in touch to find out what’s included.
