01The fuel of your muscles
Carbohydrates are the main engine of your body while running. As soon as you start exercising, your body first uses the glycogen stores in your muscles and liver. That glycogen is converted into glucose — the fastest and most efficient source of energy you can use during exercise. That's why workouts in which you start "full" often feel so much lighter and smoother.
If you have consumed too few carbohydrates, your glycogen stores will run out more quickly. Your blood sugar levels drop, your stride feels heavy, and your pace plummets. That recognizable moment is often called “the man with the hammer” among runners: you can no longer accelerate, even if you want to. It's not a lack of motivation, but simply a lack of available fuel.
During an easy endurance run, your body can use more fats — which is slow but efficient. But as soon as the intensity increases, for example during a tempo run, hill training, or interval, your body switches almost completely to carbohydrates. Fats simply cannot be converted quickly enough for this type of effort.
Eating enough carbohydrates before and after your training not only helps you perform better, but also to recover well and replenish your glycogen stores.
02Before, during, and after training
Before running
During running
After running
A good carbohydrate strategy is all about timing. Your body mainly burns glycogen (stored carbohydrates) while running, and the better you manage that supply, the more constant your energy and pace will remain. The approach differs before, during, and after training — especially for longer distances or intense sessions.
Before running
The goal is to optimally fill your glycogen stores and gently prepare your body for exercise.
2–3 hours before running. Eat a meal with slow carbohydrates that slowly give you energy. Think of oatmeal, whole wheat pasta, brown rice, or a bread meal. Combine this with some protein for stability (yogurt, chicken, tofu), but keep fat and fiber limited to avoid stomach upset. 30–60 minutes before departure. Choose light, fast carbohydrates that do not burden your stomach. Examples: a banana, a honey sandwich, a sports waffle, or sports drink. This gives your blood glucose a small boost, making you a more comfortable start. Coffee. Can help with focus and alertness, but test it first on training days, not competition days.
while running
For workouts longer than 75–90 minutes (or for intense sessions such as long tempo runs), it pays to replenish fuel along the way. This prevents a dip, keeps your heart rate more stable, and postpones fatigue.
30–60 grams of carbohydrates per hour. This is the guideline for most runners. You can get this through gels (20–25 g), sports drinks, energy bars, or a combination of these. Always test what works during training. Every brand of gel tastes and falls differently. What works on paper, your stomach does not always have to accept. Small sips, regularly. Large doses at once increase the risk of stomach complaints, while small doses keep your energy levels stable.
After running
Recovery starts as soon as you stop running. Your body wants to replenish glycogen, repair muscles, and reduce inflammation. Eating soon after your run helps most if you'll train hard again within about a day; otherwise, what you eat over the whole day is what counts.
Carbs + proteins in 3:1 ratio. You replenish energy and give your muscles building materials to recover. Good examples are cottage cheese or yogurt with fruit and a little muesli, chocolate milk, a smoothie with banana, milk or yogurt, and some oatmeal, or a recovery drink with carbohydrates and protein. Follow-up meal within 1–2 hours. A complete meal with carbohydrates, proteins, and some healthy fats helps your body fully refuel. Don't forget hydration. Drink to thirst and replace fluids gradually. Electrolytes mainly make sense after prolonged exercise or heavy sweating.
This approach supports every phase of your training — from starting energy to steady pace and rapid recovery. This way you get more out of your sessions and arrive fitter for the next training every week.
03How much do you need?
Your carbohydrate needs depend greatly on the intensity and duration of your training. The faster or longer you run, the more glycogen your muscles use — and the more important it becomes to maintain those stores. The diagram below will help you make a realistic estimate:
Rest day. 3–5 g carbohydrates per kg body weight. Your body requires less fuel, but still enough to support recovery and normal daily functions. Light training (easy run, short run). 5–7 g/kg. Enough to replenish glycogen and keep energy levels stable without overeating. Heavy or long training (interval, tempo, long duration). 7–10 g/kg. These are the days when you feel the difference: eating well beforehand means higher quality, less fatigue, and better recovery.
For a 70 kg runner, that means 490–700 grams of carbohydrates on intense training days — more than many people expect. It shows how important nutrition is for performance and recovery.
04Carbohydrates and fat burning: contradictory?
It seems like eating carbohydrates and stimulating fat burning are mutually exclusive, but in reality they reinforce each other when you time it right.
During gentle endurance running (zone 1–2), your body uses relatively many fats as an energy source. A moderate carbohydrate intake can help: you learn to use fats more efficiently without having to increase your intensity.
But as soon as your pace increases — think tempo runs, hills, intervals, or races — your body runs almost entirely on carbs. Fat burning simply cannot provide energy fast enough for higher speeds.
Therefore, the idea that “fewer carbs is better for fat burning” is only partly true:
For easy endurance running. Lower intensity = relatively more fat burning. For intensive training. Carbohydrates are indispensable to deliver quality. For recovery. Carbohydrates accelerate glycogen replenishment and support muscle repair.
A chronic carbohydrate deficiency:
reduces training quality, delays recovery, increases injury risk, reduces motivation and pleasure.
So the key is balance: Use gentle workouts to train your fat burning, but support your heavy sessions and total weekly load with sufficient carbohydrates. This way you build up both endurance and speed, without sacrificing recovery or health.
