When it comes to fasting there are two types of people: those who imagine it as an excellent strategy for losing weight, stay fit and well; and those who imagine it as self-inflicted torture to protest in prison, risking death.
Bhe, it's not this, or at least not only this.
Behind fasting, and intermittent fasting, there is so much to say, much that has been said and much that has not been understood, but then, Luckily, there is science!
Today we talk about intermittent fasting, a practice that became fashionable years ago and is still popular among celebrities, incluso Chris Pratt, the man who whispers to velociraptors.
This practice consists of fasting for several hours a day and instead eating in a short space of time. For example in practice 16:8 the fasting phase lasts 16 ore, while for 8 hours you can eat as much as you want. Or another option is to have only one meal a day and fast the rest of the time.
Those who follow this diet often report rapid weight loss with various beneficial effects, as a detox (from no-better-identified toxins), piú energy, a lot of self-control over appetite and positive effects on mood.
But scientific data does not help fans of intermitting fasting. Rather, some suggest that this practice can even lead to death [1]! (So so soooo!)
Let's try to see together now how intermittent fasting works and how much it helps or worsens our health.
First question: Intermittent fasting really burns fat?
This can be easily measured with a special machine that measures how much fat our body burns per minute by analyzing our breathing. When we burn fat in fact, we use oxygen and produce carbon dioxide. Then, the more CO2 is emitted, the more fat we are consuming.
In some studies using this technique, you see how the fat consumption afterwards 24 hours of fasting increases by approximately 20% [2].
So yes, It is true: The intermittent fasting diet burns fat. In media, after a few months, they can be lost from 3 in 7 kg [3].
But where's the trick?
Second question: how come we lose weight with intermittent fasting?
Weight loss depends on many factors: the diet, habits, lifestyle (sedentary or not), the diet, physical activity; I already mentioned the diet?
Here it is, what you eat makes a big difference in the results of intermitting fasting. For example, let's imagine doing intermittent fasting 16:8. What will we eat in the 8 hours of freedom? Baked pasta with sausage, steak with roast potatoes browned in colonnata lard, side dish with burrata and fried ice cream and pastiera for dessert? Fame, eh?
Perhaps, the secret to the success of intermittent fasting is that, when do we start, you no longer eat the same quantities of food you were used to before.
Then, to keep it simple: we lose weight because we eat less [4,5].
A study, conducted by researchers at the University of Alabama, helps us answer this question. In this case we have two groups of people: group A fasting and group B eating normally. But for 5 weeks both A and B must eat the same calories; the only difference is that participants in group A have to eat them in 8 hours and fasting for the others 16 [5]. Result: no one lost weight, neither in group A nor in group B. Conclusion: no, the fasting of 16 hours does not miraculously make you lose weight [6,7,8].
Third question: fasting can prolong life?
There are many who support the idea that intermittent fasting, or even one done in a prolonged manner, may they be the elixir of life that everyone has been waiting for.
But in reality it's not really like that. In this case it is science itself that proves itself wrong.
Here the protagonist in action is autophagy, that is, the process in which the cells of our body begin to eat themselves to eliminate defective parts and at the same time use them to produce new resources [8,9]. Try to imagine cells as green incinerators that decide to reuse waste or old materials to produce energy instead of accumulating rubbish.
Many studies have shown how fasting increases autophagy, thus “cleaning” our organism. This seems like excellent news that seems to wink at supporters of the detoxifying effect of fasting. Ma (a big BUT) here we find the catch. All of these studies were performed on worms (Caenorhabditis elegans), midges (Drosophila melanogaster) and mice (Mouse muscle). In these cases it was also observed as a certain gene, linked to autophagy, it is expressed more and works more in a fasting state. But the way to ascertain the results is to sacrifice the animal and study the tissues. It goes without saying that the same thing cannot be done on humans and therefore there is no data contemplating the effect of fasting on autophagy on humans.
And the exact same thing goes for studies on the effect of fasting on life expectancy: We do not know nor can we know today whether this diet will make us live longer [11,12,13].
Final question: Fasting yes, or fasting no?
It is not possible to draw certain conclusions today because research is still exploring the world of nutrition. But some things are known and have been confirmed in many studies. The human body has evolved over millennia to withstand many adversities, including that of hunger and famine.
The civilized world as we know it today is very recent in human history. This is why our organism has adapted to survive less rare events. We have not yet evolved to overeating, For this reason, diseases and disabilities due to obesity and diabetes are increasingly common. they have been obtained through modifications capable of preventing the insulin molecules from joining together, we are very well suited to fighting hunger. When we are hungry, particular endogenous responses are activated to survive: hormones such as ghrelin enter the circulation and trigger a series of reactions in the brain that change our physiological state. The activity of some organs increases and our brain uses all its energy to look for food, for example, even the view changes. When our ancestors were facing a famine (let's call it involuntary non-intermittent fasting) they had to resist somehow, and their bodies had adapted to finding resources elsewhere (see autophagy) to reduce the energy wasted in other activities, to accumulate fats in order to then use them as resources, to burn proteins in the absence of sugars and so on [14,15,16].
On the other side however, we are not suited to safeguard ourselves from a situation in which we manage too many calories. For example, we do not have an efficient cholesterol removal system, which we know is one of the main causes of coronary problems; lose omental fat (beer belly) it's very difficult; we have no endogenous defense mechanism against obesity.
Considering this evolutionary factor, it becomes very clear why fasting has positive effects on the body: what we actually do is go back to minimal nutrition and not ingest too many calories, fats and sugars.
Furthermore, fasting is not a risk-free practice. The possibility of losing too much weight, feeling tired and disoriented and having no energy, it is very high and should not be underestimated. Senza abbastanza energie e zuccheri, il nostro cervello entra in una sorta di “low energy mode” e alcune attività potrebbero essere piú rischiose, come guidare ad esempio.
Un altro rischio è la formazione di calcoli alla cistifellea, molto molto dolorosi, che possono anche portare alla rimozione dell’organo [17] .
In conclusion, non conta per quante ore mangiate e digiunate al giorno, ma conta invece la qualità e l’apporto calorico della vostra dieta. Invece che chiamarlo digiuno potremmo semplicemente chiamarla dieta sana e minimale.
Una nota positiva sul digiuno però va aggiunta: forse aiuta a combattere il cancro.
In a study by Professor Valter Longo of the University of California it was demonstrated how fasting weakens tumor cells making other therapies (like chemotherapy) more effective. This happens because cancer cells are special cells that grow very quickly and to do so they need a lot of sugars. Thanks to fasting, available sugars decrease and the environment in which these cells wallow sooner, changes and becomes inhospitable; just enough to weaken the tumor.
Valter Longo studied this effect in mice, after these treatments, they successfully defeated the tumor [18].
But now these studies have been extended to humans and the results are very promising [19,20].
Questa ricerca è ancora in corso e non ci sono abbastanza dati certi per dire che il digiuno aiuta a curare il cancro, ma ci sono buone prospettive e molte speranze.
References:
[2] E’ stato visto come il ciclo del glicerolo aumenta tra le 18 e le 24 ore di digiuno fino a 3 volte in piu dopo 3 giorni di digiuno paragonato a solo una notte (8 ore) di digiuno.https://www.semanticscholar.org/paper/Adaptive-reciprocity-of-lipid-and-glucose-in-human-Soeters-Soeters/547958d6729fbcee77a305757a1717844a995fa8?p2df]
[3]https://onlinelibrary.wiley.com/doi/full/10.1002/oby.23614
[4] https://www.annualreviews.org/content/journals/10.1146/annurev-nutr-071816-064634
[6] https://pubmed.ncbi.nlm.nih.gov/35194176/
[7]https://pubmed.ncbi.nlm.nih.gov/35194176/
[9]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2990190/
[10]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8488577/
[11] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3652890/
[13] https://link.springer.com/chapter/10.1007/978-3-319-42118-6_12
[16]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6412136/
[17]https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6412136/
[18]https://www.pnas.org/doi/10.1073/pnas.0708100105
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