Fasting for a whole day is difficult

Neurobiological and psychological effects of fasting

Prof. Dr. rer. nat., Dr. habil. med. Gerald Huether, Göttingen

Man is a social being and his brain is specially adapted to the requirements of social coexistence.

Almost everything we do with this organ, what we perceive, how we evaluate these perceptions, what we feel and think and, last but not least, how we act, is not innate, but is determined by the socially determined set of conditions in which we grow into it. The experiences made in this way play a decisive role in structuring the interconnections created in the brain, which are initially very open. The most lasting experiences that we as humans can have and that are anchored particularly deep in our brain are experiences that help us to make the fear and the associated stress reaction controllable: through the acquisition of knowledge and competence, through the achievement of psychosocial security, through striving for power and influence, or through the power of faith. We rate one of these strategies as successful if it helps us to restore harmony between us and the world around us. Only then do we feel "calmed down", that is, the alarming confusion in our head (the arousal in associative and limbic brain regions) finally comes to rest.

Neural network

Information processing in the central nervous system is understood today as a simultaneous serial and parallel process of activating multifocal, closely interconnected neural networks. Each of these networks has structurally defined interconnections with other networks. Every change in the activation state of a certain network triggered by external stimuli or internal processing mechanisms is transferred to other networks. If no suitable reaction can be triggered to eliminate the disorder that has arisen in this way, the excitation develops as an unspecific activation and ultimately also reaches limbic brain regions responsible for the emotional reactions (stress and fear).

This process can be stopped in different ways: by activating a behavioral reaction that turns off the "trouble spot" (see above), by taking pills that inhibit the transmission of excitation (sedatives, e.g. alcohol or benzodiazepines) or by stimulating one globally effective transmitter system (e.g. through increased intake of carbohydrates or fat, but also through fasting). The activity of the local networks operating in different areas of the CNS is namely controlled and coordinated by "supra-regional" systems with far-reaching projections. The serotonergic system is a particularly effective, globalizing and harmonizing transmitter system that acts on the activities generated in spatially separated, regional networks of the brain. The processes of its nerve cells located in the midbrain move like a giant "projection tree" into all areas of the brain and normally release their messenger substance serotonin (3-5 times / second) at their ends (the serotonergic presynapses) throughout the day Influences nerve cells: In this way, the serotonergic system has a globally active "harmonization effect" that is constantly present on the information processes taking place in the CNS. Only during dream sleep does the activity of this serotonergic system cease. It can be strengthened by psychotropic drugs and certain drugs (serotonin reuptake inhibitors, ecstasy) and by nutritive manipulations: short-term (postprandial) through the consumption of high-carbohydrate and / or fatty foods (or luxury foods), longer-term through food restriction ( Fast).

Fasting, Serotonin and Psyche

From animal experiments it has been known for a long time that there is an increased availability of tryptophan in the brain and therefore an increased serotonin synthesis and release by serotonergic presynapses even with short-term food abstinence. Even more interesting is a second effect on the serotonergic system, which only occurs after a few days (18): Food restriction reduces the number of serotonin transporters in the nerve endings of serotonergic neurons. If rats are fed only half the amount of food they normally eat each day, this restrictive diet (which is associated with a 10-20% weight loss) leads to a marked decrease in the density of serotonin transporters in the cortex after one week. After 14 days of food restriction, this effect is even more pronounced. Due to the reduced serotonin transporter density in the cortex, there is a permanently reduced efficiency of the resumption of the released transmitter. The increased concentration and longer residence time of serotonin in the extracellular space enables a longer lasting and more far-reaching interaction of this transmitter and neuromodulator with one of its numerous receptors on downstream neuronal or glial cells. The extracellular concentration of serotonin and thus the duration and the radius of the transmitter effect is increased to an even greater extent than by the selective reuptake inhibitors due to the additionally increased serotonin synthesis and release with a restrictive diet.

The tension-relieving effect of fasting

The psychological effects of fasting are as impressive as they are well known. (...) In many cultures fasting is used to achieve transcendental states of consciousness in the context of religious or spiritual acts. Even religious customs such as our pre-Easter fasting period or Islamic Ramadan seem to be based on the empirical experience of these biological effects. Fasting was also used for healing purposes by various medical schools. As early as the fourth century BC At the time of Hippocrates, fasting began to be used as a therapy for physical and mental illnesses. Today it is increasingly used in holistic medicine, e.g. B. in fasting clinics applied. After two or three days of fasting, i.e. when the downregulation of the density of serotonin transporters can also be observed in experimental animals, (...) (most people) experience a clear stabilization of mood, which is sometimes even accompanied by euphoria and feelings of transcendence.

Is Fasting Addicting?

But just as the consumption of carbohydrates and fat for the purpose of coping with anxiety can be addictive, the discovery of the zero diet as a strategy for coping with anxiety is also addictive. When vulnerable people are exposed to long-term, difficult-to-control stress, the risk is particularly great that they will discover the psychological effects of fasting as a way of coping with anxiety. The permanent downregulation of the serotonin transporter that occurs with prolonged food restriction, the resulting stimulation of serotonergic activity and its subjectively experienced psychological effects thus offer a possible explanation for the development of eating disorders. People who find the mood-stabilizing effects of fasting to be particularly positive can easily get into a vicious circle that is very difficult to break. Since the downregulation of the serotonin transporter is more easily triggered by food restriction in adolescents than in older people and since the ideal image of "beautiful = slim" people in particular motivates young women to fast, the high prevalence of eating disorders in this segment of the population is hardly surprising.

Starving Versus Fasting: A Small But Crucial Difference

Only those who voluntarily forego food will fast. All others either do not eat anything because they stop feeding due to metabolic or hormonal changes and do not feel hungry (e.g. people with illness, animals in hibernation or during certain phases of the reproductive cycle), or they are hungry.

Hunger is a very dominant feeling and - if it cannot be satisfied - triggers violent displeasure, which is associated with corresponding changes in the central nervous processing mechanisms (focused attention, increased aggressiveness, motor restlessness, etc.) and an activation of the neuroendocrine stress reaction. Much of what can be measured in terms of changes in a starving rat can also be transferred to a starving person; Both go through a similar sequence of metabolic and hormonal adaptations to the nutritional deficiency situation, and in both cases stress-sensitive systems are activated in the brain (initially increased catecholamine release, which can ultimately lead to catecholamine depletion). In both cases there is a stimulation of the hypothalamo- hypophyseo-adrenocortical system, which leads to an increased formation and release of corticotropin-releasing hormone (CRH) from ACTH and ß-endorphin (which is a "by-product" during the processing of ACTH Proopiomelanocortin arises) and is finally accompanied by cortisol (or in the rat by corticosterone). As signal substances, all of these substances trigger a whole series of other reactions in the CNS. The list of these stress-related neurobiological and neuroendocrine effects as well as the behavioral and psychological effects of starvation could go on and on.

The decisive factor, however, is that this whole cascade is not only not triggered, but rather effectively suppressed if one does not starve, but fast - voluntarily, without fear and without stress. This makes the individual assessment crucial for the neurobiological and neuroendocrine effects triggered by restricted food intake and their effects on the psyche and the body.

Source: UGB conference "Fasten aktuell", May 6-8, 1999

The Association for Independent Health Advice trains competent fasting leaders and has developed a special concept for fasting courses.
You can find training and further education for fasting leaders here

Do you want to fast yourself? You can find qualified fasting leaders in the Healthy Eating Network.

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