Role and amount of carbohydrates in athletes diets

Author: Sergey Yezhov - sports medicine physician.
2017-01-12

Carbohydrates play a primary role in ensuring the bioenergetic processes of a training body, typically comprising 60 to 70% of the total energy intake from food for athletes. Considering the significance of carbohydrates, sports dietitians recommend that professional athletes increase their total carbohydrate consumption to 10 grams per kilogram of body weight per day. This is particularly important during periods of high-intensity training or competition preparation.

This intake should include both monosaccharides (glucose, fructose) and more complex carbohydrates (fiber and starch). The ratio of simple to complex carbohydrates in an athlete’s diet may vary depending on the nature of physical exertion and the ultimate goals of the training cycle. During strength training (high-intensity but short-duration exercises, such as gym workouts), the diet should primarily contain simple sugars in easily digestible forms. Fruits, fruit juices, jelly, and sweets are suitable for this purpose.

In the diet of athletes engaged in cyclic activities of variable or moderate intensity (team sports, swimming, running), alongside simple sugars, high-molecular-weight carbohydrate forms should also be present. This is necessary to consistently maintain blood sugar levels during extended sports sessions.

The significant role of carbohydrates in the diets of individuals training is also linked to replenishing glycogen stores in the liver and muscles. This depot serves as a reserve of energy for the body, both during aerobic and glycolytic types of training. According to American authors, to optimally maintain glycogen levels in muscle tissue, carbohydrate intake should be no less than 1200 kcal per day for a low-carbohydrate diet and 2300 kcal per day for a high-carbohydrate diet.

However, excessive carbohydrate intake at the expense of reduced protein and fat consumption can negatively affect not only athletic performance but also the health of the trainee. Increased sugar consumption puts stress on the pancreas, which produces insulin. This leads to constant overload and exhaustion of its function.

Additionally, regular spikes in insulin levels can cause a decrease in the sensitivity of cell receptors to this hormone, potentially leading to the development of diabetes. When glycogen stores are saturated, excess carbohydrates begin to convert and accumulate as fat tissue.

Furthermore, if the physical load is significantly separated from meals (more than 3 hours), the muscles, having quickly depleted their glycogen stores, may experience hypoglycemia. Therefore, athletes involved in cyclic activities are advised to have additional snacks between breakfast, lunch, and dinner in the form of fruits, carbohydrate drinks, and sweets. This will help make sugar intake throughout the day more even, avoiding insulin spikes.

As mentioned earlier, carbohydrates from food are converted into glycogen, which is stored in muscle tissue and the liver and serves as a backup energy source for the body. To fully restore the body after intense physical activity, it is necessary to replenish glycogen stores in the liver and muscles. The synthesis of glycogen is a relatively slow process, at only 5% per hour. Complete restoration to baseline levels can take around 20 hours and requires a substantial carbohydrate intake.

Many researchers note an increase in the utilization of carbohydrates and amino acids during the so-called protein-carbohydrate window (the first 2 hours after training). At this time, glycogen resynthesis increases to 7-8% per hour. Ukrainian scientists (Levin, Nour, 1996) developed rational nutrition schemes for athletes to create an additional reserve of glycogen. The essence of the methodology lies in reducing the proportion of carbohydrates in the athlete's diet combined with high-intensity training. This causes depletion of glycogen stores in the body. The subsequent period of carbohydrate loading allows for the accumulation of glycogen stores above baseline levels. This phenomenon has been termed supercompensation by the authors.

The essence of it is as follows.

1. Initially, two extremely high-intensity workouts are conducted to deplete muscle glycogen.

2. Then, three workouts are performed in the athlete's normal mode but against a background of a low-carbohydrate diet.

3. Over the next three days, the intensity of training is reduced against a high-carbohydrate diet (up to 90% carbohydrates of daily caloric intake).

A modified, gentler method of carbohydrate loading can be used. This glycogen synthesis stimulation plan consists of conducting workouts with an intensity level of 70-75% of the maximum, while reducing the duration from 90 to 40 minutes over three days. During this time, carbohydrate content in the diet reaches 50%, or about 350 g per day. In the following two days, the duration of training loads is reduced to 20 minutes, and the carbohydrate intake increases to 70% or 500-600 g per day. After this, a rest day follows, right before the sports events.

Basic rules for carbohydrate consumption by athletes:

1. High-carbohydrate products are best consumed in small portions throughout the day.

2. Protein-carbohydrate mixes, such as Gainers (gainers), should be taken one to two hours before training sessions. This will help raise blood sugar levels and stock up on essential amino acids needed for muscle work.

3. Consume an energy drink containing 8-10% carbohydrates throughout the training, at a rate of 0.5-1.0 liters for each hour of activity. This increases the body's performance during training by 30-35% and slows down the breakdown of amino acids as fuel for working muscles.

4. Take protein-carbohydrate mixes of a complex nature immediately after training to replenish glycogen stores in the body.

PS: Based on the book by S.A. Oleynik "Sports Pharmacology and Dietetics."