Nutrition during weight reduction.
In almost all sports disciplines, a player's physical fitness is directly influenced by both body weight and its composition, i.e.. body fat and lean body mass. In most cases, there is an inverse relationship between the percentage of fat in the body and the physical capacity of the body, and therefore players, with excess adipose tissue, it is recommended to reduce it to the recommended values (table 8.5). Lowering the fat content in the body quite often also applies to representatives of disciplines, in which there are weight categories and those, where, mainly for aesthetic reasons, a very low body weight is required, as is the case e.g.. in rhythmic gymnastics or figure skating.
Table 8.5. Recommended body fat values depending on gender and age.
Weight loss is a problem, which not only adult players come into contact with, but also young people practicing sports, and sometimes, unfortunately, also children. In young people, which are still growing and developing, when lowering the "weight" one should be very careful, because their body weight naturally increases, often without excessive fat gain. Therefore, losing weight, especially for young people, should always be preceded by body composition measurements, on the basis of which the percentage of body fat in the total body weight of a competitor can be determined. When there is no excess body fat in a competitor, weight reduction is not allowed. In such a case, slimming would take place at the expense of muscle tissue and would lead to a reduction in physical performance and health deterioration.. If, on the other hand, the amount of adipose tissue is excessive in relation to the physiological norm (table 8.5) then weight reduction is even advisable.
It should be remembered that the minimum amount of adipose tissue, below which you must not lose weight is 12% in women and 5-6% in men. These minimal amounts of adipose tissue provide an insulating layer, are essential for the protection of blood vessels, nervous tissue and internal organs and are necessary for the proper hormonal balance of the body.
There are several ways to reduce weight, not all of which are healthy and recommended, especially athletes. One of the unreasonable and, therefore, not recommended methods of losing weight include fasting for a few days and dehydration. During the fast, the consumption of food and fluids is drastically reduced. As a consequence of this procedure, there is a minimal reduction of body fat, and the loss of "weight" is mainly related to lean body mass and water (decrease in muscle mass), which has a negative effect on physical fitness.
A frequently used method of weight loss, Especially in disciplines where weight limits apply, dehydration by exercise or thermal stress (sauna) The result of this method is the loss of water from the body along with minerals and vitamins. Research results indicate, that the loss of body water above 2% total body mass leads to a clear disturbance of the water balance of the system and significantly reduces the physical efficiency of the body.
If there is a need to reduce body weight, the most appropriate way to lower it is to use a properly balanced reduced diet, in relation to the demand, caloric value. Such a method, it is indeed long-lasting, but gives the best results in terms of maximum fat loss and minimal lean body mass loss, which is a condition for maintaining good physical fitness and health. Weight loss in a young person practicing sports should be approx 1 kg / week (maximum 1,5 kg). The length of the weight loss period depends on this, how many kilograms a competitor must reduce body weight.
In weight loss diets for athletes, the amount of energy supplied is reduced by an average of 50% in relation to the demand, caution is taken not to limit the energy consumption below 2000 kcal per day for competitors and 1500 kcal per day for female players, because the basal metabolic rate is within limits 1400-1700 kcal per day. A lower energy level in the diet can use muscle tissue as its source. However, in certain situations, this applies to female and male competitors with a relatively low body weight and maintaining dietary restrictions for a long time (e.g.. in artistic gymnastics or figure skating) diets with a lower energy value are used, then it is recommended for the players from 1100-1400 kcal, for players and from 1600-1800 kcal of energy per day.