Self-regulation of food intake

Main links of the functional nutrition system

Maintenance of energy and plastic balance in the body is ensured by two main pathways:

1. External link. It is the primary way of meeting metabolic needs under normal conditions. The external link represents a complex chain of behavioral and physiological reactions: formation of food motivation, selective appetite, food-seeking behavior, actual food intake, and the processes of its processing in the digestive tract.
2. Internal link. It is activated in situations of forced or voluntary refusal of food. It provides endogenous nutrition — maintaining an optimal pool of nutrients by utilizing the body's own tissue reserves. At the same time, there is a decrease in the level of metabolic processes, which is regulated by hormones of the pituitary gland, thyroid gland, pancreas, and other endocrine glands.

Mechanisms of endogenous nutrition

If food intake from the outside ceases, the body triggers two main survival mechanisms aimed at mobilizing internal resources.

1. Expenditure of nutrient depots ("Self-injections") This process, described by the physiologist V.N. Boldyrev, consists in the release of nutrients from tissues directly into the blood. Notably, this process is strictly timed to periods of the so-called "hunger motor activity" of the stomach. The circulation of substances occurs in a closed loop:

• Release of reserves from tissues into the bloodstream.
• Transition from the blood into the cavity of the digestive tract.
• Processing of the released substances by digestive juice enzymes.
• Reabsorption into the blood in an adequate, easily digestible form.

2. Redistribution of nutrients A mechanism studied by I.P. Razenkov, which consists in the strict redistribution of resources within the starving body. Nutrients are taken from organs less significant for basic survival (primarily striated skeletal muscle) and directed to the most significant consumers — the heart and brain. The transport pathway is similar: substances from the muscles enter the blood, undergo processing in the gastrointestinal tract, and return to the blood to nourish vital centers.

Exogenous nutrition and pathophysiology of overeating

Under normal conditions, the body functions through exogenous nutrition — the intake of food from the outside. The sensation of hunger begins to form already 3–4 hours after the last meal.

Here, the evolutionary principle of "preventive eating" comes into play. A person eats under the influence of hunger, despite the fact that there is no real deficit yet, and the available endogenous reserves would be more than enough for 20–30 days of autonomous operation.

With guaranteed and constant access to food, this principle becomes dangerous. Unjustified preventive eating leads to severe pathophysiological consequences:

• Development of overweight and obesity.
• A sharp increase in the prevalence and severity of cardiovascular diseases.
• A significant reduction in overall life expectancy.

Clinical application: therapeutic fasting

Knowledge of the mechanisms of the internal self-regulation link formed the basis of the therapeutic fasting method. It is based on the physiological ability of the body to alter (decrease) the intensity of metabolic processes in tissues, especially in the brain.

Such a decrease in metabolism has a pronounced normalizing effect on the course of many pathological processes. The method shows clinical efficacy in a number of conditions:

• Neurotic disorders and obsessive-compulsive states.
• Cardiac disorders and arterial hypertension.
• Ulcerative lesions of the gastrointestinal tract.
• Various "functional" disorders of body systems.

Individual variability in survival during starvation is high: from 5–10 to 60 days, but on average the safe reserve is 20–30 days, which makes short-term therapeutic fasting physiologically justified.

Briefly: answers to topical questions

Class and exam questions

What else to study on this topic

• Hormonal regulation during starvation: the role of the pituitary, thyroid, and pancreas
• Formation of food motivation and selective appetite
• Mechanisms of "hunger motor activity" of the stomach
• Reduction of metabolic processes in brain tissues during therapeutic fasting
• Food-seeking behavior as a component of the external link of self-regulation

Other topics in the «Hunger, appetite, and satiation» section

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