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The Advantages and Disadvantages of Intermittent Fasting

Living Well

Fasting has become one of the most common ways to feel healthier: is it effective? Here we analyse and discuss different impacts and possible ways of fasting.

In 2016, Yoshinori Ohsumi won a Nobel Prize for the discovery and investigation of the process called “autophagy”: from that moment on, there has been an intense interest in the benefits of fasting for the body.

This amazing “cellular autophagy” is a regenerative mechanism by which the body’s cells, under certain circumstances, are able to recycle their own content, allowing them to get rid of invading toxins, pathogens, viruses and bacteria. One of the existing ways to bring about the activation of this mechanism is fasting. Put very simply: since the organism is forced to adapt to a lack of food, the cells start consuming their own waste substances and converting them into energy (autophagosomes, double-membrane vesicles, encapsulate these components or waste products and release them into lysosomes, cellular organelles that contain digestive enzymes, where they are destroyed).

Recent scientific studies demonstrate the multiple benefits of intermittent periods of caloric restriction or fasting. Indeed, beyond the cellular recycling that occurs with the autophagy process and that allows the body to regenerate and heal itself, numerous other benefits have been observed, among which the following stand out.

Although fasting should be undertaken under medical supervision, here we research, analyse and discuss different impacts and possible ways of fasting. This article is not recommended:

– For persons under 18 years of age.

– For persons suffering from eating disorders (anorexia, bulimia, etc.).

– For persons dealing with cortisol problems, diabetes or hypoglycaemia.

– For persons who are pregnant or breast-feeding.


Fasting leads to an increase in the hormone adiponectin, whose function is to promote fat oxidation, reduce triglycerides and improve insulin sensitivity. Ghrelin levels are regulated. Ghrelin is a hormone generated in the stomach, responsible for producing the feeling of hunger; in addition to that function, it is also involved in the secretion of growth hormone.

About six hours after starting a fast, there is a spike in ghrelin that produces a feeling of hunger and the desire to eat. Once this peak is overcome with continued fasting, the ghrelin released into the bloodstream stimulates growth hormone secretion. This leads to increased basal metabolism (i.e., the amount of energy used by the body at rest) by up to 12%. Also, during the period of dietary restriction, the body draws energy from its lipid stores.


Growth hormone secreted by the pituitary gland is basically responsible for controlling metabolism and producing blood cells for the immune system, increasing the body’s defences. It also preserves and increases muscle mass and decreases fat mass, stimulates the production of collagen and increases bone mineral density. Furthermore, it improves athletic performance and muscle strength; slows down the aging process and cognitive decline.


A decrease in blood sugar and insulin – in the first few hours of fasting – enhances the body’s ability to become sensitive to insulin and improve resistance to it (very beneficial for people with type II diabetes or prediabetics). Additionally, fasting:

– Increases our body’s ability to secrete adrenaline, noradrenaline, dopamine and T4 and T3 hormones that are involved in brain function, memory, and our emotional and mood state.

– Improves cardiovascular health thanks to the reduction of cholesterol and triglycerides (up to 25% and 30%, respectively), that occurs during fasting.

– Improves the intestinal microbiota, which leads to an increase in bile acids that act as regulators of blood pressure.

– Reduces inflammation. Remember that multiple diseases occur as a result of systemic inflammation of the body produced mostly by an inadequate diet.

All this evidence means that the benefits of intermittent fasting, an ancient method of self-healing, are becoming more and more accepted by the medical and scientific community, helping to overcome the traditional Western medical prescription of five meals a day.


In addition to these metabolic and systemic improvements, the practice of intermittent fasting produces clear mental and emotional benefits for those who practice it:

– There is an improvement in concentration, in the ability to maintain attention and focus, and in the quality of sleep.

– It reduces anxiety associated with eating.

– It increases the ability to listen to one’s body and to be more conscious in choosing the foods with which to break the fast. This connection with one’s body leads to the desire to love it, nurture it, and care for it by giving it the nutrients it needs and avoiding processed and unhealthy foods.

– It produces a sense of self-control and personal mastery when choosing when to eat and when not, helping to manage compulsive attitudes towards food and other elements.

– It fosters a sensation of lightness and agility.

– It allows for optimized use of time, by not having to be aware of preparing and eating many meals and selecting better quality.


– 12-hour fast: Everyone, even those who do not choose to practice intermittent fasting, would note an improvement in their health and well-being if a 12-hour break was observed between the last meal of the day and the first of the next day. This is the minimum period that the body needs to cleanse itself, regenerate itself and carry out the metabolic functions necessary for optimal health.

– 16-hour fast: It is the most recommended and ideal fast for women due to their hormonal profile. In this type of fast, you do not eat any food for 16 hours and choose to eat during the remaining 8 hours of the day. The classic example is finishing dinner at 8:00 p.m. and not eating any food until 12:00 noon the next day. It is easy to adapt to a daily routine and to carry out. Weight loss is constant with this type of fast.

– 18-hour fast: This type of fast is the one that brings the most benefits to men due to its metabolic requirements. As an example, dinner would end at 7:00 p.m. and the first meal would be eaten at 1:00 p.m. the next day.

– 20-hour fast. Food is consumed for a period of 4 hours each day. Typically, you choose to have a single daily meal in which you include all the macronutrients (fats, proteins and carbohydrates) that the body requires.

– 5-2 Diet: This plan consists of eating food normally (always opting for a healthy and balanced diet) for 5 days a week, and for the remaining two days restricting intake to approximately 500 calories, which can be consumed in a single meal or spread throughout the day (only fruits, vegetables and soups or broths, for example).

– Diet on alternate days: One day you opt for a normal diet and the next day you restrict your intake to 500 calories a day, and so on.

– Stop eating anything one day a week. Eat normally throughout the week and choose a day when you will only drink water, teas, and infusions.

– Fasts from 7 to 14 days: This type of fasting requires medical supervision.


– Water (it is allowed to add a few drops or a splash of lemon or mint leaves, ginger root slices or turmeric)


– Infusions and herbal teas (sometimes also coffee)

– The use of sweeteners is not allowed since it has been shown that they produce a response in the production of insulin, thus counteracting the benefits of fasting.

– The consumption of MCT (medium chain triglycerides) oil does not break the fast since for its digestion the body does not require enzymes and bile acids. Taking a tablespoon of this oil can help you to cope with the hours of fasting, especially for those who are just beginning to practice it, providing energy and cancelling the possible feeling of hunger. However, the ideal is to not consume anything, to take full advantage of fasting and the cell regeneration mechanisms it produces.


It is of utmost importance that, in the period of food consumption following the fast, a balanced diet is chosen that includes the correct amounts of macronutrients, vitamins and minerals. It is very unwise to break the fast with binge eating or processed foods devoid of nutrients, as they will do the body more harm than good.

A great way to stop the fast is with one of the Symbeeosis elixirs diluted in a glass of water, followed by a fruit and vegetable smoothie that can be alternated throughout the week. You can also choose a fistful of dried fruit. After half an hour or an hour, you can have the first meal of the day including fats, proteins, and slow-absorbing carbohydrates, preferably quinoa, oatmeal, brown rice, etc.