Your first marathon is a week away. The long runs are done, training is winding down, and suddenly a lot revolves around food. At your running group, someone swears by a big plate of pasta the evening before, while a fellow runner talks about several days of bread, rice and sports drinks. Which of this is true? This article explains what carb loading is, from what competition duration it is worthwhile and how it is done today without the former depletion phase. You will also find a sample day for a body weight of 70 kilograms, typical mistakes and the most important rules for the last few hours before the start.
What carb loading is and why glycogen matters
The body stores carbohydrates as glycogen, a water-soluble polysaccharide. The main stores are in the liver and the muscles. Liver glycogen mainly keeps the blood sugar level stable, while muscle glycogen serves as an energy reserve for the muscle itself. In total, the body has only a few hundred grams of such carbohydrate reserves, and they are used up during longer competitions. Once the stores are empty, performance drops significantly. You can find the basics of this nutrient in the article on carbohydrates as friend or foe.
Carb loading, literally loading the muscles with carbohydrates, comes in at exactly this point. The term refers to adjustments in training and nutrition intended to achieve the highest possible storage of muscle glycogen, above all before endurance competitions. In the best case, the glycogen stores in the muscles can roughly be doubled in this way. Because they are filled beyond their usual level, this is called supercompensation.
Who benefits from carb loading
The decisive factor is the duration of the exercise. From a competition duration of about one and a half hours, carb loading can bring advantages. Typical examples are cycling races, long-distance running, triathlon, cross-country skiing or long-distance swimming, in other words sports in which the exertion uses up a lot of muscle glycogen. With the additional reserves, optimal performance can be maintained for longer or a given distance can be covered faster. Whether the effort is worthwhile for a half marathon, for example, therefore depends mainly on how long you are out on the course. In shorter competitions, normal carbohydrate reserves are sufficient, and an advantage from carb loading is then unlikely.
Team sports with a match every two to three days are a special case. Carb loading in the true sense is hardly feasible there. However, a high-carbohydrate diet based on the same principles helps to refill the stores as fully as possible again and again. And what about women? Most studies on glycogen storage were carried out with men, but carb loading basically works for women too.
Formerly the Swedish diet, today just a loading phase
The classic method
The technique was developed in Sweden at the end of the 1960s, which is why the classic version is also known as the "Swedish diet". First comes a depletion phase of three to four days with at least two hard training sessions and a low-carbohydrate diet. This is followed by a loading phase, also lasting three to four days, without training but with a high-carbohydrate diet. In this way, the usual glycogen stores could be roughly doubled.
The approach today
Later research showed that the depletion phase is not necessary at all. The loading phase alone is enough to fill the muscle glycogen stores to the maximum. In practice, this means: for two to four days, you reduce training significantly and eat a high-carbohydrate diet, with 10 to 12 grams of carbohydrate per kilogram of body weight per day. If the stores are already normally filled, muscle glycogen can even reach peak levels within a single loading day. Holding back in training is important: carb loading only works on a rest day or with low-intensity training.
What a loading day looks like
Many people underestimate how much 10 grams per kilogram is. For a body weight of 70 kilograms, that works out at 700 grams of carbohydrate a day, plus about 135 grams of protein and 90 grams of fat. The energy requirement is 15,500 to 18,000 kilojoules, or around 3,700 to 4,300 kilocalories. A sample day:
- 3 bowls of low-fibre breakfast cereal with 1½ cups of reduced-fat milk, 1 banana and 2.5 dl orange juice
- Toast with honey and 5 dl sports drink
- 2 large sandwiches with various fillings, a pot of low-fat fruit yogurt (200 g) and 4 dl soft drink or fruit juice
- Fruit ice cream with banana and honey and a cereal bar
- 2 plates of pasta with sauce, 3 slices of garlic bread and 2 glasses of recovery drink
- Toast with ham and 5 dl sports drink
Behind this selection are rules that apply to any carb loading:
- Snacks: Three main meals alone are not enough to manage the amount.
- Drink your carbohydrates: You will hardly reach the required amount from solid food alone. Fruit juices, sports drinks or soft drinks instead of water help.
- Low in fat and protein: Butter, cheese, oils, meat, eggs and fish only sparingly as a small side, otherwise the volume becomes too large.
- Little fibre: White bread, white rice, jam or honey instead of large amounts of wholegrain products, fruit and vegetables. Eating a lot of fibre risks an upset stomach.
- Eat what you know: only foods that you know and tolerate well.
The simplified version with a carb loader
If you do not want to put together special menus, stick to your usual high-carbohydrate diet with 5 to 7 grams per kilogram and take in an additional 3 to 5 grams per kilogram via a carb loader. This is a drink with about 200 to 250 grams of carbohydrate per litre, three to four times as much as a standard sports drink. Its main source is maltodextrin, a polysaccharide made up of glucose. It is best to spread the amount over the day, for example in servings of 2 to 4 dl after the main meals or as a snack.
Typical carb loading mistakes
- Too much training: Some people can hardly hold back shortly before a competition. Without a rest day or easy training, however, the stores will not be refilled.
- Too little carbohydrate: The amount needed is often underestimated. A pasta meal the evening before is good, but at most one part of carb loading. A carbohydrate plan or a sports nutrition professional can help.
- Carb loading as a free pass: Eating everything indiscriminately means taking in a lot of fat, which leaves too little room for carbohydrates and can even lead to an increase in body fat.
And the scales? Carb loading does in fact add around 1 to 2 kilograms. This extra weight consists of the additional glycogen and the water stored in the muscles along with it. After the sporting performance, it is gone again.
The last hours before the start
On competition day, nutrition has two goals: filling the energy stores one last time and avoiding digestive problems. For a marathon or triathlon, refilling the stores the day before is the main focus, and the meals before the start are the fine-tuning. Because intensity and stress are usually higher in competition than in training, the same food is more likely to upset your stomach. Fat, protein and fibre prolong digestion, liquid meals are digested faster than solid ones, and large portions more slowly than small ones. Easily digestible carbohydrates such as pasta, white rice, corn, potatoes or white bread with at most a small side are therefore well suited.
The closer to the start, the smaller the portion
- 3 to 5 hours before: last normal-sized, easily digestible main meal, for example pasta with a low-fat sauce.
- 1 to 3 hours before: if needed, an easily digestible snack such as a sandwich.
- Less than 1 hour before: only small bites or liquids such as a sports drink or gel.
The guideline is 1 to 4 grams of carbohydrate per kilogram of body weight in the 1 to 4 hours before the activity. If you have an early start, it is best to get up at least three to four hours beforehand. If you are very nervous, liquid meal replacements are an alternative when solid food is not tolerated.
Carbohydrates shortly before the start do no harm
The worry persists that carbohydrates in the last hour would make blood sugar crash after the start, known as rebound hypoglycaemia. The rumour goes back to a study that was not very realistic, and almost all later studies found no effect or even a positive effect on performance. Blood sugar normalises after about 10 to 15 minutes of exercise, in other words during the warm-up. Foods with a low glycaemic index, which raise blood sugar comparatively little, also bring no proven advantage before the start. Many of them, such as lentils or wholegrain products, are also hard to digest.
Drinking before the start
Do not start with a fluid deficit. Your urine should be clear to pale yellow. Drinking about half a litre an hour before the start leaves enough time to excrete any excess water.
During the competition: topping up carbohydrates
If a competition lasts longer than 45 minutes, taking in carbohydrates during exercise makes sense, because the glycogen stores are then being used up. The amount depends on the duration at competition intensity:
- 45 to 75 minutes: a small amount of glucose
- 60 to 120 minutes: 30 to 60 grams of glucose per hour
- 120 to 180 minutes: 60 to 90 grams per hour, glucose supplemented with fructose
- Over 180 minutes: up to 90 grams per hour, glucose and fructose
Fructose is needed because glucose absorption is limited to around 60 grams per hour. During a competition, only eat and drink what you have tested beforehand. The article on electrolytes and sports drinks explains what matters when choosing a drink. Besides water and carbohydrates, caffeine, incidentally, is one of the few substances that can have a positive effect on performance during exercise.
Course tip from update Akademie: If you want to prepare athletes for competitions, you need more than a meal plan. The Sporternährungscoach (sports nutrition coach) course covers energy balance, nutrients and hydration as well as nutrition before, during and after exercise, including carb loading, complemented by muscle building, fat loss and prohibited substances. The workshop Ernährung vor und während dem Wettkampf (nutrition before and during competition) is a compact introduction.
Frequently asked questions about carb loading
How long does a race need to be for carb loading to be worth it?
Carb loading is worthwhile for endurance competitions lasting about one and a half hours or more, for example cycling races, long-distance running, triathlon, cross-country skiing or long-distance swimming. In these events, muscle glycogen is heavily used, and additional reserves can help to maintain performance for longer. In shorter competitions, the body's normal carbohydrate reserves are sufficient.
How long before a competition should you start carb loading?
Today, the loading phase lasts two to four days. During this time, training is reduced significantly and you eat 10 to 12 grams of carbohydrate per kilogram of body weight per day, which for 70 kilograms means around 700 grams or more. A preceding depletion phase with hard training sessions and a low-carbohydrate diet, as the classic Swedish diet required, is not necessary.
Do you gain weight from carb loading?
Yes, by around 1 to 2 kilograms. This weight consists of the additional glycogen and the water stored in the muscles together with the glycogen. It is temporary and gone again after the competition. More body fat is a greater risk if carb loading serves as an excuse to eat a lot of fatty food. The rule is therefore: high in carbohydrates, but low in fat.
What should you eat before a competition?
The last normal-sized main meal belongs three to five hours before the start and consists of easily digestible carbohydrates such as pasta, white rice, potatoes or white bread with little fat. One to three hours beforehand, a snack such as a sandwich is possible if needed. In the last hour, only small bites or liquids such as a sports drink or gel follow.
Conclusion
Carb loading is more than a pasta evening. It is a planned process over two to four days: cut back training significantly, eat and drink 10 to 12 grams of carbohydrate per kilogram of body weight, and keep fat and fibre low. It pays off for endurance competitions lasting about one and a half hours or more. The temporary weight gain is part of it. On competition day, tolerance and timing then count: the last larger meal three to five hours before the start, after that only small items and liquids. And for every phase: only eat and drink what you know and tolerate well.
