Carbohydrates during long workouts: when food is needed during exercise
Gels, isotonic drinks, and bars on the course solve one problem — preventing fuel from running out where it is truly needed. The condition "truly" is key here: for a one-hour workout, your own reserves are more than enough, and everything eaten during this time only contributes to your daily caloric intake.
How much you have in reserve
Carbohydrates are stored as glycogen in the muscles and liver. The total reserve in an adult corresponds to approximately 1500–2000 kcal, and this is not an abstract figure: it is exactly what determines when you "run out of steam" during long-duration work.
At moderate intensity, the reserve lasts for about an hour and a half to two hours of continuous work. The higher the intensity, the faster it is consumed, because the proportion of carbohydrates in energy production increases.
Hence a simple dividing line: for up to an hour and a half, additional fuel does not solve anything; for longer, it starts to matter.
How much to eat during the event
| Duration of work | Carbohydrate guideline |
|---|---|
| Up to 60 minutes | Not required, water is sufficient |
| 60–90 minutes | Optional, up to 30 g per hour |
| 2–3 hours | About 30–60 g per hour |
| Longer than 3 hours | Up to 60–90 g per hour with a mixture of carbohydrate sources |
The top row requires explanation: the absorption of a single type of carbohydrate is limited by transporters in the intestine, so above approximately 60 g per hour, only a mixture makes sense—usually glucose and fructose, which follow different pathways. It is on this principle that sports gels and drinks are built.
In what form
- Drink. Covers fluid, carbohydrates, and sodium all at once. More on this in the article about water and electrolytes.
- Gel. Concentrated carbohydrates; requires drinking water, otherwise it is poorly tolerated.
- Regular food. Bananas, dates, crackers, white bread with honey—at low intensity, they work no worse than sports nutrition and are cheaper.
A general limitation is tolerance. The intestine works worse during exercise than at rest, and what is normally digested at the dinner table may not be digested in the fifth hour. Therefore, nutrition during an event must be tested during training, not on race day.
What this does not apply to
Regular gym workouts. A one-hour strength session does not deplete glycogen; carbohydrates are not needed during it, and extra calories are needed even less if the goal is weight loss. The mechanics are in the article about calorie deficit.
Weight loss. Nutrition during an event is about performance, not body composition. When working to lose weight, additional carbohydrates during a one-hour workout simply reduce the daily deficit.
Fasted training. These are possible and are discussed in the article about pre-workout nutrition, but the longer the work, the worse this combination works.
Carbohydrate loading
A technique from competitive practice: one to three days before a long event, the proportion of carbohydrates in the diet is increased to boost glycogen stores. It works for distances of approximately an hour and a half to two hours or more and makes no sense for shorter ones.
A side effect that scares the unprepared: weight increases by 1–2 kg due to water, because every gram of glycogen binds about three grams of water. This is not fat, and it goes away after a few days—the same mechanics as discussed in the article about calories in a kilogram of fat.
Practical scheme
- Up to 90 minutes — water, and that is enough.
- From two hours — 30–60 g of carbohydrates per hour, starting from the first hour, not when you start feeling tired.
- Choose the form and taste in advance during training.
- After long work — carbohydrates and protein in the coming hours; more details in the article about post-workout nutrition.
Frequently asked questions
- From what duration of training do you need to consume carbohydrates?
- From about an hour and a half of continuous activity. Before that, your own glycogen is sufficient: the total reserve corresponds to approximately 1500–2000 kcal, and at moderate intensity, it is enough for an hour and a half to two hours.
- How many carbohydrates should I take for the distance?
- About 30–60 g per hour for activities lasting two to three hours, and up to 60–90 g per hour for longer ones, if using a mix of sources. Exceeding 60 g per hour is only effective with a glucose-fructose blend, as they are absorbed through different pathways.
- Are gels necessary, or can I use regular food?
- At low intensity, a banana, dates, dry biscuits, or bread with honey work just as well and are cheaper. Gels are more convenient while running and require washing down with water. Any option should be tested during training, not on race day.
- Are carbohydrates needed during a regular gym workout?
- No. A one-hour strength session does not deplete glycogen stores, and extra calories reduce the daily deficit if the goal is weight loss. Nutrition during a race is about performance, not body composition.
- Why does weight increase after carbohydrate loading?
- Each gram of stored glycogen binds about three grams of water, so a gain of 1–2 kg is water, not fat. It disappears after a few days as the stores are used up.
Read next
- Water and electrolytes during training: when plain water is not enough — Plain water is enough for almost everyone, almost all the time.
- What to eat before a workout — The question "what to eat before a workout" is almost always actually a question of "how long before.
- What to eat after a workout and does the "anabolic window" exist — The rule that you must "eat protein within half an hour after a workout or it's all for nothing" is known to anyone who has ever stepped into a gym.
This article is for general information. It is not medical advice, a diagnosis, or a prescription for treatment or a diet, and it does not replace a consultation with your doctor. If you have a health condition, are pregnant, take medication, or follow a diet prescribed to you, decisions about food belong with your doctor.
Figures from regulations, guidelines and studies are given as they stood when this article was prepared and may since have changed; check them against the primary sources. This article is not advertising, an offer, or individual advice, and neither the author nor the site owner is responsible for decisions taken on the basis of it.