Il digiuno: tipologie, fisiologia e benefici

Hello friends of the web, in today's video we begin to deal with a topic that is very fashionable and that is fasting. In recent years there has been an explosion of interest, publications and books divulgative on fasting and you know that I don't really like to go back to fashion also because we have already talked in the past about fasting, intermittent fasting and times of meals. On the other hand, however, I am concerned that many people, bombarded with information perhaps too simplified and superficial that come from various parts, may misunderstand the basics of the matter and then start doing dangerous things. So today and in the next four videos we will try to put some order in this jungle and to deal in a more organic and in-depth way with the theme of not what to eat but how much and when. And here I immediately anticipate my first concern as a nutritionist that is that in all these approaches that we will discuss we will deal a lot with times, ways, hours of fasting but not so much with what to eat in the periods of food intake, indeed some present it as an advantage of the type you can eat everything you want as long as you eat it in that period. Here, if this is how we understand it, I tell you right away that we are not really there. In food, the thing is always more important than the how and the when. If we only care about when to fast and when to eat, this in itself is not enough and it does not tell us anything about the quality of our diet and the difference between a balanced diet and a capricious diet will always be made by what we eat at the moment we eat. I can have an architected fast in the best of ways, but if then when I eat I eat disgusting things, I will not take advantage of it. Ok, so let's always remember that what we eat is much more important than when we eat it. I say this because I say a jungle, because in reality the term fasting is extremely vague and different people mean different things both on the reasons why they do it and above all on the ways. For this reason it is very important to try to clarify yourself well right away. Different reasons, I said, because for some fasting is simply a demagogic practice to do only if you want to lose weight, for others instead it is a detoxifying purpose and should be done cyclically, for others still for therapeutic reasons so to do only if there is a specific need, for others instead it is simply a lifestyle that should always be followed anyway to stay healthy. And this only to stay in the field of health, then as you know there are those who fast for religious or political reasons, of protest, etc. And so already in the purposes you see there is a nice difference, but above all the differences even more relevant come in the ways and here essentially we have to decide on what we mean by fasting. In the literal sense of the term, fasting simply indicates the period of interval between two meals. In many languages, the word to indicate breakfast describes precisely this concept of interruption of nocturnal fasting, breakfast in English, that is, literally breaking the fast, in Spanish breakfast, déjeuner in French. Here, if for breakfast we mean this, then we all fast, even Mr. Cicciobomba in the half hour that runs between the snack with the craft and the Nutella and the aperitif with the pizzas and the Wurstel, but in that half hour he made a fast. From a nutritional point of view, however, it makes sense to talk about fasting only if the abstinence from food is such as to induce a specific metabolic event that we will see better later, that is, when the glycemia is maintained more by the gluconeogenesis than by the reserves of glycogen. And this happens on average after 16 hours from the last meal, so for any abstinence from food that does not last at least 16 hours, it makes no sense to talk about true fasting. For example, the most popular type of so-called intermittent fasting, 16-8, that is, 16 hours without eating and then 8 hours in which to place meals, is not a real fast, it is just a restriction of the daily window in which food is introduced, whose main effect is to keep insulin low for many hours and it can do very well, it is simply not a fast. Another confusion is that between fasting and calorie restriction, the two things are often associated but do not necessarily coincide, for example if I do a single meal a day, that is a real intermittent fast because it exceeds 16 hours since I fast for almost 24, but if in that single meal I introduce all 2000 calories of the normal caloric need, there is no calorie restriction, so it is a fast, but not a calorie restriction, vice versa if I do one of those protocols very unhappily called fasting mime, during which for some days I introduce 400 or even 200 calories a day, that is a strong calorie restriction but it is not a fast because it is not a complete abstinence from food and what I eat very little prevents the activation of the physiological mechanisms of fasting and it is something that again can have many positive effects, but it has nothing to do with fasting, more than fasting mime, I would call those diets mime carestia or mime hunting joke gone wrong, that period when our ancestors were on a strict diet and ate only what little they could find around, some roots, some bugs, some insects, so a strong calorie restriction, but not a fast. The real fasts are basically of three types, first of all the intermittent fasts, in which periods of food intake, periods of prolonged abstinence for more than 16 hours are continuously alternating, for example consuming a single meal a day is a form of intermittent fasting very popular and are fasts of almost 24 hours, or the alternate days fast, so once or twice a week I fast all day and these are fasts of about 36 hours, because for example if I do the last meal at dinner, let's say at 20, then the day after I skip all meals and I don't eat until the breakfast of the day after, still at 8, 36 hours have passed of complete abstinence from food. The second type instead are the occasional fasts, also of the duration of 24-36 hours, but done not in a cyclical way, but occasionally, once in a while, for example a complete fast a day before a week of detoxifying spring diet. The third type are the so-called therapeutic fasts, prolonged over 36 hours, generally for a week, but also for longer periods. The main difference is that if an occasional fast can be practiced by anyone in autonomy, a therapeutic fast should be done only under supervision, at least the first time, because as we will see it requires a little extra caution. You will surely have already heard the maxim according to which the human body can survive three months without eating but only three days without drinking, in general it is remembered when we talk about the importance of water. Today, however, let's keep in mind the first part, without eating for three months, so any concern that fasting for 1, 2, 3 or even 4 weeks is incompatible with life is unfounded. As long as we have water to drink, our body can perfectly sustain even very prolonged fasts. Besides, who does not know the famous fasters for political or protest reasons who have completely given up food for weeks in a row. So when the lady comes to me and says but fasting a whole day, but in the sense of just water, but you don't die? No, ma'am, in your health conditions you don't die fasting a day, fasting a week and not even fasting a month. But if fasting a month is something that can only be done in a clinic or under constant supervision, fasting one or two days is something that almost anyone can do quietly at home. Humans have always abstained from food for more or less prolonged periods in the Paleolithic simply because hunting and gathering did not always end well and in subsequent eras because those periods of such important fasting for our health and regeneration of our body had been transformed into religious precepts that today have been softened and converted mostly into symbolic practices even for those few who still follow them, but until a few decades ago they were very rigid rules for many Catholics, for example Lent was a period of strong calorie restriction and the last week before Easter was even a complete fast with only water, so they did a whole week of fasting every year and coincidentally in conjunction with the period in which we recommend to do a detox that is more or less at the beginning of spring. So in short, fasting has always been an absolutely normal practice for humans and it is only a few decades ago that it has completely disappeared from the radar. In nature fasting is also instinctive in some circumstances for example animals fast spontaneously when they are not well, it is a mechanism that the body uses to focus on healing and harness the therapeutic benefits of fasting because digestion is energetically very demanding and steals a lot of resources from where at that moment the body would like to concentrate its energies on something else. In reality we too often are not hungry when we are sick and if we force ourselves to eat it is only because we still have in our ears the worries of our mother when we were little who told us you have to eat something, you can't fast, you haven't eaten anything since yesterday, whatever you want, I'll make you a pasta in broth, a milk with biscuits, the truth is that it would be better to listen to our body and fast until our appetite returns on its own. Ok, so in summary we have these three practices that in many cases may coincide but not necessarily because they indicate different things. One is the calorie restriction, that is to introduce less calories, one is the time restricted eating, that is the restriction of the daily window of food intake and one is the real fasting that in turn is distinguished between intermittent fasting, occasional fasting or therapeutic fasting. Well, we will talk about all these things one at a time in the following videos of this series. Today, instead, let's lay the foundations, that is, let's try to understand the physiological bases that will then help us better understand the advantages and disadvantages of all the various practices mentioned above. We must examine the physiology of fasting, that is, what happens in our body from the moment we stop eating and then in the following hours or days, depending on how much we prolong that fast. Let's start with the meal, the last meal before a fast. After eating, as always, glycemia and insulin increase. Under the action of insulin, glucose is pushed into the cells and what is in excess, compared to what is needed, is used first of all to replenish the glycogen reserves, which are however limited, so once you fill them, everything that grows is converted into reserve fat. After digestion and absorption between 6 and 16 hours after the end of the meal, the post-absorption phase begins, in which glycemia and insulinemia begin to decrease and their decline, beyond a certain level, induces the stimulation of hunger. If this stimulus is ignored, glycemia continues to decrease, but since it is vital for the body to keep it constant, it begins under the push of the glucagon hormone to reach the glycogen reserves in the liver to release glucose to be sent back to the blood in order to keep the levels of glucose constant. But the glycogen reserves, as we said, are limited and end early. If we continue not to eat as the glycogen reserves are emptied, the body begins to resort, in ever greater measure, to an alternative strategy to produce the glucose it needs to maintain glycemia, that is gluconeogenesis, that is, to produce new glucose starting from proteins or more precisely from some amino acids called gluconeogenic, that is, that can be converted into glucose. Now the question here is always, after how many hours of fasting does the glycogen end and do we start using proteins to maintain glycemia? Well, before all the glycogen completely ends, unless we start doing vigorous aerobic activity, in which case we finish it in a couple of hours, but normally before using it the last drop, 24 or even 36 hours pass. But our body does not reason in tannic compartments, tac, the glycogen is over, tac, I switch to proteins. It is precisely because maintaining stable glycemia is so important that it begins to worry about it well before and to activate the alternative way of gluconeogenesis, a bit like if you had a bank account, all of a sudden you have no more income, so to live you have to start giving fund to your savings. It is not that you wait for the balance to reach zero and then you say, ah well, now maybe I have to start worrying. No, as you see your balance going down more and more, you start to activate yourself first, to reduce expenses, to look for alternative income, to ask for a loan, etc. And so the body does that when it begins to see the reserves of its precious glycogen decrease dangerously and that nothing is coming from food to replenish it, it says, wait a minute, that in the meantime a little glucose I start doing it myself before things get bad. So already after 5-6 hours of fasting it begins to activate to do a little gluconeogenesis in the liver and if we continue not to eat, it does more and more, while the glucose that comes from the reserve is always less and less, until, increasing the first, decreasing the second, we reach a point where glycemia is kept more stable by the glucose produced by the proteins than by the one coming from the glycogen reserves in the liver. And at this point, as we said at the beginning, on average you reach around the sixteenth hour of fasting, some call it metabolic switch. I don't like it very much because it gives the idea that you suddenly go from one mode to another, a bit like pressing a switch, when instead, as we have seen, it is a gradual process. But the idea of ​​the switch is that you go from a situation in which the glycemia was mainly supported by the glycogen reserves, to one in which it is mainly supported by the gluconeogenesis. From then on, the glycogen continues to provide less and less glucose until, after 24-36 hours of fasting, all the glycogen reserves are completely zeroed and all the glucose to maintain the glycemia comes from the proteins. If our fasting continues, the gluconeogenesis continues to increase for the first two days when it starts to go down a bit again and then it stops at a more or less constant level. Why that small decline? Because in the meantime it has taken over another typical metabolic mechanism of fasting, which is ketosis. And here we have to take a little step back. When the body realizes that the glycogen is running out and that to maintain the glycemia it must use the proteins to make glucose, it activates at the same time also to save as much as possible that glucose. Think again about your bank account. The gluconeogenesis from the proteins would be a bit like selling some of your precious object to get money to reinvigorate your bank account. What languages! But at the same time also try to reduce the expenses a bit so that what you get lasts longer. And so the body does, which instead of using glucose as an energy source, begins to use more and more fats, of which instead the reserves are much wider and abundant. Almost all the cells of our body, when glucose runs out, can resort to fatty acids as an energy source, with limitations though. For example, our muscles can get energy from fats, but only to support an aerobic activity. If we instead make an anaerobic effort, then we must of course use sugars, which are the only ones from which you can get a little ATP even in the absence of oxygen. An aerobic activity is, for example, a sprint or even just a run or do the stairs if you are out of training. In short, if you have a big breath, your muscles are not receiving enough oxygen. Here, but apart from that situation, for the rest, the muscles go quietly with the fats. There are other cells, however, that just don't want to know, they are not only able to get energy from fats and go only to glucose. And these are, for example, the brain, in general the cells of our nervous system, some blood cells such as the red blood cells and others such as the renal amygdala. These cells will always need a little glucose, but even in this case, the body can do something to reduce it to a minimum, and that is to convert the fats, of which we have always said in abundance, into a particular category of acids, which are the ketones or ketone bodies. And from these ketone bodies, even the brain is able to get at least part of its energy. So we see that fats are able to make both muscle cells function, although in aerobics, and in this case they can be burned directly via beta-oxidation, and the brain, at least in part, via ketone bodies. So as the fast progresses, our cells use less and less glucose and more and more fats. Here too, it is not tac-tac, although the term metabolic switch is often used, or it is said that it goes from a sugar burn mode to a fat burn mode, in reality nothing of all this happens, it is always a gradual change. The shift towards fats begins already in the first phases of fasting, but it takes over only after about 48 hours and reaches its maximum after about 4 days of fasting, when it settles on a concentration of ketone bodies in the blood that is about 70 times higher than normal levels. At that point, all the cells that can produce less glucose do it, and about 90% of the total energy consumption is covered by lipids. Those who can use fats use fats directly, those who cannot use ketones. Only in part, however, as we have said, some cells will always need a little glucose, and this is why that remaining 10% of the total energy consumption will always have to be covered by sugars, especially for the use of the brain. From the fourth day of fasting onwards, the energy consumption of the brain is assessed on 75% by ketones and 25% by glucose, and this is why glycemia must always be maintained constant, and that is why, however, during the entire fasting period, even if it is a month and a half, that amount of glucose from gluconeogenesis will always be necessary. However, in the meantime, another useful thing is also verified since the reserve fats begin to be burned at full speed to obtain energy and ketones, a lot of glycerol is also released, that molecule that keeps together the three fatty acids in the three glycerides, and all this glycerol that advances can also be converted into glucose to contribute to maintaining glycemia. In short, it is verified that situation dreamed of by those who do ketogenic, hyperlipidic or hyperproteic diets, that is, to maintain glycemia using glycerol, which in their case is almost never verified unless it is completely marginal, but with prolonged fasting, yes, because there it really begins to advance a lot of glycerol, not from the fats we eat, but from those we mobilize. And so what happens? That if the phase of intense gluconeogenesis between the sixteenth and fortieth hour of fasting is supported especially by proteins, from the third day of fasting onwards and then at full speed from the fourth to the fifth, an important quota of glucose is made with the glycerol of the fats, therefore saving the need to destroy proteins. We have entered what in English is called protein conservation phase, the phase of protein conservation, and that is why after that break, then one can go on fasting even for a month with all in all modest effects on the lean mass, and this fact is important to remember because the main difference between intermittent fasting and therapeutic fasting is that intermittent fasting makes the whole mechanism restart every time, so it leaves us almost always in that phase in which we need to destroy a lot of proteins to maintain glycemia, it brings us back there every time, then we eat and then again there. Vice versa, a prolonged fast passes that initial phase only once and then enters the next stage in which it can save proteins using glycerol, which it will never be able to do if not in a completely marginal way, neither an intermittent fast nor a ketogenic diet, that is, in which almost carbohydrates are zeroed out, but for the rest we normally eat fats or proteins, and so by doing so we induce ketosis, but for gluconeogenesis we must use mainly amino acids. With the prolonged fast, instead, from the third day onwards we move on to the protein conservation phase, which, attention, does not mean that from the third day of fasting onwards we no longer need proteins, we do not need them for energy purposes, to make glucose, but we always need them for their structural and functional roles, for the protein synthesis of essential enzymes, for the maintenance of tissues dedicated to vital functions, etc., and so the body will always need a little protein, which, not coming from the diet, since we fast, not coming from the reserves, since we do not have any, and not being able to be made from fats or sugars, because let us always remember that we can convert proteins into fats or sugars, but we cannot do the opposite, that is, convert fats or sugars into proteins, well, what option is left to our body? It will have to recover them where they already are and recycle them, that is, take them from where they are less useful to use them where they are more useful, and this process is called autolysis or autophagy, and in fact it is one of the therapeutic values ​​of fasting. Not receiving anything from the diet, the body must recover proteins for its more urgent structural and regulatory needs, in reality not only proteins but also minerals and other molecules, and therefore it must necessarily perform a kind of recycling, taking them from other cells and tissues that are disassembled to recover what is needed. This forces the body to make a kind of inventory and repurge, in order to prioritize and dismantle what is less needed. In the first place, we use protein waste, enzymes and other non-functional proteins, we dismantle old tissues and damaged or defective or precancerous cells that will be replaced, as well as we dismantle the enzymes that are not immediately necessary, for example those of digestion, since we do not eat so much, and those not priority, for example those due to reproduction and at least initially to the immune system, and then obviously also the protein of the muscle, which is the main protein reserve of the body, 70% of the body's proteins are in the muscles, starting from those necessary muscle proteins to the more intense activities that nowadays are not possible to perform. During this process, old and damaged cells are destroyed, tumoral cells, and at the same time a deep detoxification is performed with the elimination of toxins, viruses and bacteria. Inevitably, however, the weight of the organs decreases, and this is why, after the fasting period, a regenerative counter-push begins, mediated by the growth hormone and the initiation of division and proliferation of the stamina cells, so in the very short time after the fasting period, the tissues of the lean mass recover the original weight by building new cells. At the end of the whole process, the body is therefore renewed, strengthened, cleaned and regenerated, and this is in extreme synthesis, the autophagy mechanism for which the Japanese scientist Yoshinori Oshumi made a great contribution, which is why he won the Nobel Prize in 2016. What is born from fasting is actually just an example of autophagy, more generally, this same biological process is born from the cells every time they are exposed to a significant stress. They focus on the most essential vital functions and recycle everything they can to recover proteins and minerals to be directed on such functions. Fasting works in this case just like that stress that starts the process. Instead, with a constant diet, without ever fasting, this reset process never activates and the cells always focus only on the protein synthesis. However, autophagy is not born, neither with caloric restriction, nor with intermittent fasting. Even there, the cells do all the protein synthesis they want because they always have new amino acids that come from food, so they don't need to go and recycle them. Let's see now what happens to weight during fasting. First of all, the digestive tract empties and only from this you lose one or two kilos, while the tissues quickly release the excess water, the so-called water retention, so you pee a lot and you lose another couple of kilos of water. In short, you start immediately in the first two days with a good emptying and a good squeezing. Then it starts to burn fat and oxidation fibers and ketogenesis begin to clog the reserves of adipose tissue, especially visceral fat and partly also subcutaneous fat, so from the second or third day you start to lose weight even from there and this time it is lost weight as fat. As an additional bonus, some lipids are also taken from the fat deposits in the arteries, cleaning them a bit. As for the lean mass, we have seen that even there a loss of weight is verified, first for the first phases of gluconeogenesis sustained by proteins and then by the initiation of cellular autophagy. And this is a frequent concern because losing lean mass is something that always arouses a bit of anxiety. Again, however, our body has found a brilliant solution and there is nothing to be surprised about because long fasting periods have always been the absolute norm throughout the history of man, so it is absolutely normal that mechanisms have evolved to make us face them without too many problems and indeed trying to also draw some advantages. What happens therefore? That during fasting, the muscles decrease in volume for the autolysis of the internal proteins to the cells, but it does not decrease the number of muscle cells, in practice the cells shrink again and that's it, emptying a bit of proteins. Consequently, during fasting the muscle strength is reduced, which is not so useful because as long as you fast, the muscles do not even have glycogen to use, but there is no degeneration of the muscle cells. In this way, the muscle mass lost during fasting will be immediately regained immediately after, under the push of the growth hormone, when the diet and normal physical activity will resume. And this adjustment in the phase of skeletal muscle loss is in full swing from the fifth day on, that's why a longer fast has practically no additional effects on the lean mass. Paradoxically, however, a strong calorie restriction diet, if maintained for a long time, may have much more deleterious effects on the lean mass than a total fast, because in that case the mechanism of autolysis and muscle loss is not induced. What happens instead to metabolic activities? Obviously during fasting the metabolism slows down, the body goes into energy saving mode and cuts all non-essential energy expenses, the basal metabolism slows down, the replacement of some tissues' cells slows down, that of the digestive tract obviously, which is so useless at the moment, but also those of the skin and muscles, the protein synthesis is reduced to the most essential activities, in short, it can save everywhere, the body saves, libido and sexual desire in general decrease and alterations in the regularity of the menstrual cycle are also possible. Instead, mental lucidity increases and this is another very intelligent evolutionary adaptation of our body. If we hadn't developed it, we would have been extinct within two generations, because at the first unexpected feeding, if after one or two days of fasting we had already started to be less lucid and we didn't even have the strength to get up, we wouldn't have been able to survive. In fact, let's remember that our ancestors did not fast by choice, but by necessity, and if there is no food, that is just the time to have to think of strategies to get it, so it is crucial at that very moment to be particularly lucid and focused. Finally, let's take a look at what happens to our immune defenses. Fasting causes a weakening of the immune system, especially due to the autophagy of the immune cells themselves, that is, at a certain point the body begins to use those to recover proteins, because in its priority sequence at a certain point it gets there and says ok now where do I get the proteins? I get them from the oldest cells of the immune system. On the other hand, however, even in that case it simultaneously begins to activate the mechanisms to then refabricate them as soon as the fast ends, starting from the stamina cells that are found in the bone marrow of the blood, and then also those will all be new and flammable, so after the fast we will also have a regeneration of the immune system. Now, overall speaking, we have studies that have investigated the effects of fasting in the multi-animal model. In mice, in fact, exposure to regular periods of fasting results in greater longevity and lower incidence of diabetes, tumors and neurodegenerative diseases. In humans, on the other hand, we do not have clinical data on fasting and longevity because experimentally it is just impossible, you can't do a clinical trial like you do a placebo of fasting. Epidemiologically it is also something so little practiced that you can't find populations of tens of thousands of fasters to study. But in short, it has been a practice for millennia and biochemically we also have a fairly precise idea of ​​the physiology of metabolic changes and genes that are activated. First of all, by regenerating the organs of the digestive system, because evidently they are left in peace not working during fasting and therefore they have time to clean and regenerate, well fasting can be useful to solve many problems and disorders of digestion and in general of the gastrointestinal tract. Even chronic viral infections, often not even diagnosed but that weaken the tissues making them more susceptible to continuous bacterial infections that must then be treated with a continuous use of antibiotics, typical example of continuous tonsillitis, otitis, sinusitis or bronchitis, well these too are often solved with fasting. Then certainly in humans we have encouraging data on the effects of autophagy on obesity, diabetes, cardiovascular diseases, tumoral diseases and autoimmune diseases such as arthritis, rheumatoid arthritis, multiple sclerosis and also on a cognitive level we know that it improves memory, prevents cognitive decline and reduces the risk of neurodegenerative diseases such as alzheimer's or parkinson's. Why all these nice things? Well, in part, these are direct actions due to calm, glycemic, detoxification, cell repair and autophagy, in part of indirect and immediate benefits simply from weight control and from avoiding an excessive diet. What we certainly know about fasting is that 1. it helps to lose weight and in particular visceral fat, 2. it lowers glycemia because it needs less glucose and increases insulin sensitivity for a set of reasons including the temporary absence of glycemic peaks but also the restoration of cellular functionality linked to autolysis. Insulin-resistant cells are among those damaged and replaced by new insulin-sensitive cells and this is often resolutive in pre-diabetic people. With diabetes it takes more caution but it is also very useful. 3. we know that it lowers blood pressure or rather normalizes it, that is, it tends to lower it a lot in those who have it high and only slightly in those who already have it normal or low. 4. it reduces the levels of chronic inflammation and this for the combined effect of the reduction of abdominal adiposity, visceral fat, you know if there are a few pre-inflammatory ones, and the autophagy of damaged old immune cells that are more inflammatory than young and healthy ones. Then 5. for the same reason as we said before, it strengthens the immune system even if it weakens it during fasting. And finally 6. indirectly it also helps to lower cholesterol and triglycerides levels in the blood. As for tumor protection, which is also one of the key topics that are discussed when talking about fasting, then at the level of protective mechanisms we can identify at least 5. 1. as always we have autophagy and here it is above all the pre-tumor cells that are recognized more easily as damaged by the body and therefore to be demolished among the first. 2. as for the already tumoral cells, these feed mainly on sugars to grow quickly and from this point of view being in ketosis can be something that slows down the proliferation because we remove the sugars. 3. the cells that grow faster, including those with tumors, needing more energy, are the ones that feel more of a fasting that makes them hungry. 4. the cells that are not sensitive to the signals of the body, such as the tumoral cells that have acquired the ability to grow even in the presence of arrest signals sent by the body and the surrounding tissues, well these cells are further disadvantaged because they are also insensitive to the hormonal signals of energy savings that the body sends during fasting. 5. in the absence of this arrest signal in progress, they continue to consume as in times of abundance and therefore find themselves first of the others with the bowl in hand. 6. and then to finish 5, during fasting the levels of IGF-1 and other growth factors are lowered and this is also a protective factor even if it must be said that after fasting it is then a counter-push of growth hormones so if it were not for the combined effect of autophagy, the two pushes here in themselves would be compensated. In poor words, we can say that fasting is a stress that results in a type of regeneration and renewal of the body, a deep cleansing and a reprogramming of the metabolism of its cells. We can say that fasting is one of the many applications of the principle of hormesis, those positive stresses to which the body responds by trying to restore homeostasis, that is, the balance of things, but in doing so, in responding to this solicitation, to this stimulation, to this alteration of the balance, the body strengthens, strengthens and in this case regenerates. No, hormesis is when the exposure to a little stress trains the body to deal with more important stress. Ok, and this is what we needed to know about the physiology of fasting. Today we have seen only what happens in our body during fasting. From the next video onwards we will begin to ask ourselves if there are actually reasons to do it even if we are well. Should we all do it or only those who have some specific need? Is it worth it? Can it have benefits? We understood it, but what about risks? Because we have seen that it is still a stress for our body and therefore requires particular caution. And above all, what type of fasting is better? Intermittent, occasional, therapeutic? What are the differences between them? Is a fast better or a calorie restriction? Or is a time-restricted eating sufficient, that is, a simple restriction of the window of food intake during the day? To answer these and other questions I give you an appointment for the next episodes. For today, however, I stop here at www.spaziosfera.com, this is the site where you can find further content and you can send your questions. You are also welcome on the Instagram, Facebook and Instagram channels of Spaziosfera. And at this point there is still one thing to remember and it is this, a quiet life, a happy mind and a moderate diet. All clear? Very food. Thank you.