There are two degrees of calorie restriction for emergency and extreme conditions. At the first, a state of compensated energy deficiency occurs with a short-term decrease in body weight and its subsequent stabilization.
The degree of restriction of calorie intake for emergency and extreme conditions, the boundaries of the allowable reduction in calorie intake.
The caloric content of such a diet decreases by approximately 25% from the usual. In this case, it is necessary to take into account the possibility of compensating for caloric deficiency by reducing body weight, reducing basic metabolism and other adaptive reactions of the body. Such food rations are intended to be used over a relatively long period of time..
for these diets, which will be called “minimal” in the future, are set by the intensity limit of normally occurring biochemical reactions on the use of nutrient reserves of the human body and the inertia of these processes.
It was found that in a state of low activity (3000 kcal / day), the minimum caloric value at which you can maintain a nitrogen balance for healthy men is 1000 kcal, that is, the caloric deficit should not exceed 2000 kcal / day. At a load corresponding to 3500 kcal / day, such a limit for a sub-calorie diet was about 1500 kcal. Therefore, in this case, the calorie deficit did not exceed 2000 kcal.
To safely perform a moderate load, the minimum diet should have at least 120–130 g of protein. An attempt to reduce its amount (to 80, 60 and 30 g) led to a sharp endogenous caloric deficit. This is explained by the fact that with low-protein diets, only part of the energy released during the oxidation of food goes to external work.
It is mainly used for internal restructuring of biochemical processes, for example, because of the need to utilize tissue and recreate new functional proteins. So, with isocaloric diets out of a thousand calories delivered by a daily low-calorie diet, metabolism is spent on separate days at 80 g of protein 580 kcal / day.
With 60 and 30 g of protein in the diet, almost all the energy received from food (948 and 1184 kcal, respectively) is consumed for these purposes, that is, with a protein deficiency, the human body is energetically in a state of complete hunger.
Based on materials from the book Physiological Foundations of Human Life under Extreme Conditions.
V. S. Novikov, S. I. Soroko.