Intermittent fasting: how to do it and what are the benefits?

The term rose around 2013 and, since then, intermittent fasting (JI) has gained the attention of the population, the medical community and researchers in the health field.

Fasting was an adaptive necessity of human ancestors. Due to the difficulty of obtaining food, either by hunting or harvesting, communities were subjected to long periods of fasting. Those who defend the style of eating points out that societies have evolved and developed very well, which would demonstrate the functionality of fasting.

But we don’t have to go back so many years to find the habit of fasting, since the prolonged space between meals is still common to certain religious communities, such as Buddhism and Islam. However, in this case, food is linked to spiritual traditions and practices.

Although there are not many scientific studies in the area, research has pointed out weight loss and well-being as benefits of intermittent fasting. For this reason, food change has been adapted and has been gaining more space among people who seek to lose weight or have a better quality of life.

It is important to remember that the practice must be monitored by a specialized professional .

What is intermittent?

Intermittent fasting can be defined as a dietary practice that alternates between periods of fasting and food intake.

When the main goal is to reduce fat, the diet aims to decrease caloric intake and encourage the body to use fat stores as an energy source.

For this, the calories are totally or partially restricted, depending on the adopted dietary pattern. That is, the diet can consist of reduced calorie intake (about 500 kcal per day) or periods of up to 36 hours without any food intake, except water and non-calorie drinks.

The diet also became popular among public figures, such as singers and celebrities. In 2017, actress Deborah Secco declared to be adept in fasting periods to improve the quality of life and, mainly, lose weight. Getting up to 23 hours without eating, the actress has nutritional monitoring and the weight loss occurred in a supervised manner, ensuring the maintenance of her health.

How does fasting work?

The body’s weight loss logic is simple: you need to spend more energy than you consume. Naturally, the body needs a certain amount of calories to perform its functions, such as maintaining breathing, circulation and performing muscle contractions. This means that a caloric portion of what is ingested is already depleted of biological functions, also called the basal metabolic rate.

When the pace of life is not able to deplete the calories ingested, they accumulate in the tissues, resulting in weight gain. Thus, weight loss must occur by increasing physical activities (which generates greater caloric expenditure) or by reducing food intake (which reduces calorie consumption).

The first aspect of intermittent fasting is to favor a reduction in food intake. This is because the periods of abstaining from food are prolonged. Over the course of a month, for example, meals will be much smaller.

Studies in favor of adopting the routine indicate that only this factor can already trigger weight loss, but that it is not only the lowest caloric intake that results in weight loss, as the fasting period encourages the body to burn fat cells (which are energy stocks) to obtain energy. This causes the fat cells to be reduced and cause weight loss.

Much of the diet is made up of carbohydrates . Right after food intake, the body starts to produce insulin, which helps in energy storage and glycemic regulation.

In this process, the carbohydrate is transformed into glucose by the liver, while the pancreas secretes insulin, responsible for transporting glucose into the cells.

Glucose is stored in the liver (hepatic glycogen) and in the muscles (muscle glycogen) for later use. Hepatic glycogen is used as a source of glucose maintenance between meals, avoiding hypoglycemia. Muscle glycogen is an energy reserve to be used by other tissues, including the muscle itself.

The liver’s glycogen is the primary energy source. If it runs out, the body needs to resort to muscle storage.

When fasting, the sources of glycogen are not replenished, but the body continues to carry out the energy burn to perform its functions.

Therefore, fasting favors caloric reduction and affects fat burning to maintain its functions.

Fasting sugar

The Society for Nutrition and Metabology indicates that, in general, carbohydrates should represent between 50% and 60% of the daily intake for a balanced diet. The nutrient is found in grains, cereals and pasta (complex carbohydrates), in vegetables, and also in the form of sugars (such as fructose and sucrose).

All sugar is a carbohydrate that, after metabolized, turns into glucose. Some researches argue that the withdrawal of sugar from the diet is not, in itself, responsible for weight loss, and the weight reduction is the result of the lower caloric intake.

The factors that most associate simple sugar and weight gain, according to some nutritionists, are the high caloric index, the accelerated metabolism (tending to satiate less and for less time), in addition to the low nutritional values ​​(source of empty calories).

Therefore, hunger returns more quickly and high levels of insulin can interfere with weight loss, which are the causes of high weight.

There are studies that defend that maintaining the same caloric intake in diets with and without sugar consumption, would bring the same results for weight loss. The difference, then, is in the quality of the food.

In summary, eliminating sugar from food can accentuate weight loss because, by depriving the body of the refined substance (a simple carbohydrate source), insulin spikes are reduced, followed by rapid energy expenditure.

Fasting insulin

When metabolizing nutrients, especially simple carbohydrates (quickly absorbed), the body releases insulin to prevent blood glucose from becoming high. The hormone transports glucose into liver and muscle cells. The excess glycogen is stored in the form of fat (adipose tissue).

Therefore, the most relevant hormone during the energy storage process is insulin.

The higher the glycemic index of the food, the greater the peak of blood sugar and, therefore, the greater the release of the hormone. Thus, after a few hours of a peak of insulin, the body will feel the need to eat again to prevent the blood glucose from continuing to fall.

In addition, the substance also acts to protect fat stores due to the release of the enzyme Lipoprotein Lipase (LPL), which makes it difficult to obtain energy from adipose sources. Therefore, the greater the insulin secretion, the more difficult it is to eliminate fat.

However, when fasting, there are metabolic changes in the body. Studies have shown changes in the production of HGH (growth hormone) and stabilization of insulin secretion.

When should it be done?

Intermittent fasting is not configured as a restrictive diet modality , but as the construction of a dietary pattern that is determined according to the characteristics of each person. Thus, it composes a functional and personalized diet.

There are no specific cases in which intermittent fasting needs to be adopted. In general, people looking for alternatives to food, want to improve health and lose weight resort to practice.

The benefits

Practitioners of intermittent fasting point out certain health benefits, such as better control of blood glucose and cholesterol levels, hormonal regulation, cardiac strengthening and increased immune system.

Diet-friendly studies by neuroscientists further suggest that fasting can:

  • Delay aging;
  • Promote weight loss by burning fat cells;
  • Reduce blood pressure;
  • Accentuate the palate due to the sensitivity of the taste buds;
  • Reduce inflammation;
  • Accelerate cell repair;
  • Promote satiety (after the organism is adapted);
  • Decrease insulin resistance.

However, it is important to note that some benefits are not consensus among researchers and not all studies are favorable to the adoption of a dietary pattern.

Understand some of the other benefits associated with JI:

Hormonal stabilization

Fasting can favor a drop in blood insulin levels and an increase in growth hormone (HGH). These two changes, in general, can be quite beneficial to the body, favoring the burning of fat, reducing insulin peaks and giving greater satiety.

In addition, HGH provides the opportunity to gain lean mass , ideal for maintaining a fast metabolism, since higher percentages of muscles need to metabolize more calories in order to obtain energy.

Reducing the risk of type 2 diabetes

Recent studies carried out at the University of Southern California have found that the risks of type 2 diabetes are reduced when between 2 and 5 days of fasting monthly. The condition occurs because by lowering insulin levels, there is a delay in cell growth and production, minimizing the risks of resistance to the hormone.

Metabolic regulation

Published by the Annual Review of Nutrition, research suggests that adopting a pattern that restricts food intake may result in beneficial changes in gut bacteria, favoring nutrient absorption and food metabolism.

According to the researchers, fasting (mainly by adopting abstention methods at night), could minimize the risks of chronic vascular diseases and obesity due to the stabilization of the metabolism.

The performance of clinical examinations in those who adhere to the diet also indicates the reduction of inflammation markers (levels that indicate altered inflammatory or immunological activity), improving resistance to chronic diseases, such as obesity, diabetes and metabolic syndrome.

Reduction of cardiac risks

Although most studies that point to heart benefits are based on animal testing, there is evidence that intermittent fasting can improve cardiac conditions as well.

Due to the decrease in LDL cholesterol (bad cholesterol), the risk of heart disease, such as stroke, myocardial infarction and plaque formation in the artery walls (atheroma) is reduced.

Cancer prevention

Researchers in obstetrics (Chicago), gerontology (Los Angeles) and nutrition (France) have conducted research that can correlate intermittent fasting with cancer- preventing factors . The results are mainly the result of tests on animals, but case studies on humans (carried out with small groups) demonstrate similar responses.

In addition, the adoption of the diet by patients undergoing chemotherapy is potentially beneficial, and may minimize the side effects of the treatment.

Decrease in neurological diseases

Analyzes developed with rats suggest that intermittent fasting can delay the onset of Alzheimer’s disease. By staying for a few hours without eating daily, the progression of the disease can be minimized, improving symptoms in 90% of the cases analyzed.

Studies published by the University of Kentucky, USA, may indicate that Parkinson’s and Huntington’s disease, which are neurodegenerative diseases, also show improvement when fasting.

Finally, studies indicate that, along with improvements in health, the fasting routine can assist in longevity, delaying aging.

Slimming

Practitioners of intermittent fasting experience a significant loss of fat mass in short periods of time. On average, 3 months are needed to check for noticeable changes in measurements, especially waist circumference.

A sum of changes in the body affects weight reduction, which may vary according to the dietary routine adopted and the physiological characteristics of each person.

Even if there are no major changes in the menu, prolonged periods without eating favor the restriction of daily meals. Thus, the less calories are ingested, the greater the body’s need to seek other energy sources (using the body’s fat stores).

Due to the change in hormonal behavior (increased growth hormone and reduced insulin release), metabolic rates are high, causing the body to spend more calories in the same activities.

When well balanced, the diet maintains the levels of lean mass , providing a healthy weight loss and without damage to health.

However, some studies unfavorable to the diet suggest that fasting would have the same weight loss results as other calorie-restricted diets. That is, it would not be the fasting period that slims, but the reduction in calorie intake.

Mental benefits

In addition to the effects on the body, the practice of fasting can bring emotional benefits. For example, some diets suggest fractional feeding, eating between 5 and 6 small meals a day.

People who are more satiated may also find it difficult to eat frequent meals, with stuffiness and difficulty with digestion. Thus, increasing the time between each feeding can be an alternative that will bring more comfort.

The increase in self – esteem , body satisfaction and well-being are reported by those who started intermittent fasting seeking to reduce measures. Consequently, mental health is affected and reflects on other aspects of life, such as good mood and sociability.

8 results of intermittent fasting

Research reviews favorable to intermittent fasting and testimonials from supporters point to very favorable results. Although there is no scientific proof of all the benefits, many of them may be associated with the adoption of a more balanced diet, healthier living habits, in addition to maintaining a routine.

  • Slows aging;
  • Eliminates bloating, gases and swelling;
  • It can optimize hypertrophy (gain in muscle mass);
  • Stabilizes weight and avoids concertina effect;
  • Decreases mood swings;
  • Favors concentration;
  • Speeds up metabolism;
  • Improves immunity;

Those who resorted to fasting to lose weight report that it is possible to eliminate significant amounts of weight in a few months, increase lean mass and better define muscles. Many reports indicate that the benefits extend for months and body changes do not stagnate over time.

How to fast: step by step

In general, the practice involves total abstention from 8 to 24 hours. But there are several ways to perform intermittent fasting and they can be tested and adapted to meet the needs of each person.

Blackout periods are usually pre-stipulated according to gender. For example, women can adopt a 14-hour fast, while men can extend it to 16 hours. But there are variations in resistance depending on body composition (more fat or more lean mass), age or physical activity.

Method 16: 8 or Leangains

Attributed to physical trainer Martain Berkhan, the routine is better suited for practitioners of intense physical activities, aiming at muscle strengthening and fat reduction.

In this modality, the practitioner has two meals a day, with a space of 8 or 10 hours between each one. Thus, a 16-hour fast for men or 14 hours for women is added.

Generally, water, coffee, unsweetened tea and chewing gums are well accepted during the fasting period, as they help with hydration and cheat hunger, which can be a difficult factor to overcome in the first weeks.

It is a well accepted method among practitioners as it does not require many hours of fasting.

Considering an average of 8 hours of sleep, practitioners add 4 hours without eating before bed and 4 hours after waking up, completing 16 hours without food intake. The practitioners, on the other hand, add 2 hours before and after sleeping, adding up to 14 hours of fasting.

The main tip of the fans is to maintain consistent schedules, preventing the body from undergoing frequent hormonal changes, causing difficulty in adapting.

In this modality of fasting, there is no limit on meals, as long as the period stipulated by the food window is respected. But food groups gain more weight and consist of intensifying protein intake and regulating fats and carbohydrates.

On days when physical activity is practiced, it is indicated that the consumption of carbohydrates is greater than the intake of fats. On days without intense activity, it is recommended that the amount of good fats be greater than carbohydrates.

Proteins should be consumed in relatively high amounts every day. This means intensifying protein foods, but without exceeding the recommended maximum limits.

Method 6: 1

During 1 day of the week, 24 hours of complete fasting are performed. Among the famous fans, Coldplay singer Chris Martin follows the routine and fast with total food restriction, drinking only water.

Although some studies indicate that the adoption of a weekly fasting day can bring benefits to the body (cardiac, glycemic and neurological), others point out that weight loss can cause the loss of muscle mass. Therefore, it is necessary to monitor the body’s constitution (ratio of fat to lean mass).

Method 5: 2

2 days are chosen during the week to drastically reduce caloric intake (on average, 500 calories). During the days of restriction, the practitioner should prefer foods rich in water and fiber, which help in hydration and satiety.

For the rest of the days, the diet remains based on healthy and more natural choices. You can maintain a menu with greater restrictions for food groups or not, depending on the objectives of the fast. For example, opt for the complete elimination of sweets or just use refined sugar for brown sugar and stevia.

Among the studies published by the University of Manchester, they point out that this method can bring good results to brain functions and DNA repair. The indication is not to make too many severe restrictions. By consuming all foods in moderation, an understanding of satiety is created and you avoid feeling hungry.

Method 1: 1

It is known by other denominations, like “Fast of the alternative day” or “UpDayDownDay”. The standard consists of 1 day of normal food and 1 day of food reduction. Unlike full fasting, days are based on fairly moderate energy intake.

On average, up to 500 calories are accepted on fasting days, with no banned foods. The practitioner can have fractional meals throughout the day (for example, lunch and dinner of 250 calories each) or eat only once.

Metabolic balance

The method indicates a fast of 5 hours between each meal. The pattern is easier to follow as it does not imply very long periods without eating.

Attributed to the German doctor Wolf Funfack, the diet aims to stabilize the rates of metabolism, avoiding hormonal changes and resulting in complete improvements (weight loss and health improvement).

Complete fasting or eat-stop-eat method

In this method created by Brad Pilon, it is stipulated 1 or 2 days a week to perform a complete 24-hour fast. When choosing 2 days, it is important that they are not consecutive. You can opt for fasting on Mondays and Fridays, for example. Thus, there is a space of 3 and 2 days between each abstention, consecutively.

Non-calorie drinks, such as water, coffee and unsweetened tea, are well accepted during restrictive days. The others tend to maintain a regular and balanced diet, with an indication for reinforcing fiber intake, opting for a varied and nutritious diet.

In general, there are no banned foods during the feeding period, not even refined sugar, sweets and pasta. The idea is to ingest moderately what one feels like.

Warrior fasting

It takes about 20 hours of fasting and the feeding phase lasts an average of 4 hours.

This type, initiated by Ori Hofmekler, seeks to alter the metabolic process, dividing the day into two food cycles. However, unlike the 16: 8 method, in which fasting comprises the sleep period, in this case, feeding occurs before bedtime, fasting during the day.

The diet is especially indicated for practitioners of intense physical activities, such as weight training , seeking to optimize muscle gains (hypertrophy or definition) and fat reduction.

Supporters point out that night meals are meant to stimulate the parasympathetic nervous system, promoting relaxation, accelerating long-term metabolism and preventing insulin spikes.

The practitioner must perform the training or physical activity at night and, up to 1 hour after the end, eat vegetables and fruits in small quantities. In up to 1 ½ hours, you should eat proteins of high biological value, that is, lean and that are well absorbed by the body.

After 30 minutes of protein intake, the practitioner should feed on a carbohydrate source, preferring whole foods with a high nutritional value. After another 2 hours, food is free, the last meal before starting the fasting cycle.

For example:

  1. A bodybuilding workout ends at 7 pm;
  2. At 8:30 pm a small portion of broccoli, carrot or apple is eaten;
  3. At 9:00 pm a small portion of grilled chicken, tuna or white cheese is eaten;
  4. At 11 pm a free meal is held, ending the food cycle.

36-hour fast

The method attributed to physical trainers John Romaniello and Dan Go is a “coma-stop-coma” unfolding.

The standard is more rigid than the others and is not suitable for all practitioners of intermittent fasting. The long period of abstaining from food can be harmful if carried out without progressive adaptation (starting with shorter periods of fasting and gradually increasing).

Food abstention is usually done on 1 day of the week and fluid intake without calories is accepted. On other days, food is free, giving priority to sources of fiber and vitamins .

Menu suggestions

16: 8 or 1: 1 method

Breakfast (12h):

  • 1 boiled egg;
  • 1 whole fruit;
  • 1 serving of whole grain cereal (bread or oats).

Lunch (15h):

  • 1 chicken breast fillet,  1 portion of sauteed vegetables,  1 portion of brown rice.

or

  • 1 cup (tea) of skimmed milk with coffee,  1/2 French bread without crumbs,  1 tablespoon of light cream cheese and  1 thin slice of ricotta;

Dinner (21h):

  • 1 serving of tuna,  1 serving of vegetables, winged with green leaves and  1 serving of quinoa or chia.

or

  • 2 tablespoons of brown rice ;, 1 medium boiled potato,  1 chicken steak and  1 peach.

Method 5: 2

On day 1, the 1st meal should have 200 calories:

  • 1 glass of skimmed milk;
  • 1 slice of wholemeal bread;
  • 1 spoon (coffee) of butter.

The 2nd meal must contain 350 calories:

  • Chicken sautéed with vegetables;
  • 1 tangerine.

On day 2, the 1st meal, with 200 calories, can be:

  • 1 sliced ​​apple;
  • 1 manga;
  • 1 boiled egg.

The 2nd meal of day 2 must contain 350 calories:

  • Tuna salad;
  • 1 serving of sauteed vegetables.

Foods to put together the menu

  • Proteins : fish (salmon, tuna, tilapia, sole), lean meat (duckling, filet mignon, ham), chicken breast, eggs, white cheese;
  • Carbohydrates : brown rice, cooked quinoa, cooked sweet potatoes, parsley potatoes, cooked chickpeas, whole grain bread, oats;
  • Liquids : water, unsweetened tea, unsweetened coffee, unsweetened lemon juice.

Adaptation phases

The adoption of intermittent fasting involves physical and mental adaptation. The time to get completely accustomed to the diet is variable, which can be quickly accepted by the body or even not be well tolerated. In this case, it is necessary to reformulate eating practices with the help of a doctor or nutritionist.

Start or phase 1

In general, changes in body and disposition are quickly noticed when adopting the diet. Reports and studies indicate that it takes the brain between 4 and 6 months to fully understand dietary changes.

This is the average time for blood glucose and cholesterol tests to show improvement, physical disposition is elevated and mood stabilized. In addition, weight is usually reduced more quickly, taking an average of 3 months to drop. The weight loss process can last for many months, with reduced circumferences and BMI .

Initially, the biggest difficulties reported are food choice and emotional detachment from food. Experts who defend the practice suggest that the change be gradual, without restricting too much food or the amount eaten in the first months.

Making healthy changes ensures that the body adapts in a healthy way to the diet, avoiding sudden changes in the absorption of nutrients. For this reason, it is recommended that, at the beginning of the diet, more fruits and vegetables are included in the diet, gradually changing industrialized foods .

Studies show that after 6 months, the body has already adapted to fasting, stabilized hormonal and nutritional levels, and emotional attachment to eating is drastically reduced.

Continuation or phase 2

There is not exactly a limitation between the phases of intermittent fasting. What happens is the adaptation of the body and mind to eating practices. In phase 2, physiological changes are already stabilized, weight loss may continue to occur and mood swings no longer occur.

If there is a desire to increase fasting spaces or change the eating pattern, this is the most suitable period. It is noteworthy that not everyone adapts to intermittent fasting. When there is great difficulty in maintaining periods of fasting, very severe nutritional changes or emotional distress, the practice should not be continued.

What can you ingest?

Hydration

Drinking water during intermittent fasting does not alter the functioning of the diet. However, as there are several ways to fast, fluid intake will depend on the type adopted.

Intermittent fasting can be performed in a very restrictive manner, in which water is only allowed during feeding times (food windows), or in a semi-restrictive manner, in which water and other liquids with a low energy content (calories) are released.

Options include unsweetened coffee and tea, water and, exceptionally in cases of malaise, pure fruit juice.

Supplementation

Some people adopt supplementation with multivitamins and amino acids while fasting. However, there are those who prefer to keep the basis of natural food, avoiding or dispensing with everything that is produced industrially.

food

It is not enough to practice fasting, it is necessary to adapt the diet so that the body is properly nourished. Meeting dietary needs by eating functional, natural and vitamin-rich foods is ideal for the body to better enjoy the diet.

Although there is nothing forbidden, choosing alternatives is a good option. For example, swap refined sugar on a daily basis for natural sweeteners (fructose and stevia), leaving sweets to eat when you want to eat a dessert.

The gradual exchanges of food, especially industrialized ones, make adaptation easier. Among the suggestions to be included in the menu, it is recommended:

  • Regulatory foods, such as vegetables, fruits and vegetables;
  • Energy sources, such as whole carbohydrates;
  • Builders, like lean proteins;
  • Fiber sources, such as vegetables and legumes;
  • Sources of essential fats, such as fish, nuts and seeds.

What to eat after fasting?

In general, it is best to break your fast with a balanced and light meal. Salads, vegetables and fruits are good options for resuming food intake, but it is necessary to look for protein sources and complex carbohydrates (which are slowly digested and have high nutritional value).

Some favorable food options for food windows:

  • Integral rice;
  • Thermogenic spices (pepper, cinnamon, ginger, turmeric);
  • Whole grain bread;
  • Chickpea;
  • Fruits in general;
  • Vegetables
  • Wholegrain noodles;
  • Sweet potato;
  • Fish;
  • Grilled white meat;
  • Vegetable broths and soups;
  • Eggs;
  • Dairy products (yogurts, cheeses, milk);
  • Vegetables (lettuce, broccoli, cabbage);
  • Vegetables (zucchini, eggplant, cauliflower, carrot).

Benefits

Planning intermittent fasting under specialized guidance, adapting the dietary windows and the restriction time to individual needs, can bring about changes that, sometimes, take longer in other diets.

Supporters report that some benefits to the body are quickly perceived, such as physical and mental disposition. In addition, glycemic control and insulin stabilization also occur with changing habits.

Compared with other types of diet, intermittent fasting has advantages, especially in the way of reconciling food and routine:

  • Ease of adaptation (it is not necessary to schedule many meals);
  • It does not follow a rigid or ready menu (it can be adaptable);
  • Various restriction modalities (alternate hours or days);
  • Provides healthier food choices;
  • In general, it can be followed for long periods, being a lifestyle;
  • Prizes for the most natural food.

Disadvantages

As with any dietary pattern, intermittent fasting has unfavorable points that deserve attention before adopting the routine. Some people can solve the disadvantages just by adapting the diet to their own needs, however, it is not always well tolerated by everyone. Negative points include:

  • Difficulty in maintaining long periods without eating food;
  • Anxiety caused by difficulty adapting;
  • Dizziness and weakness at the beginning of the diet;
  • Inability to combine physical activities;

At the beginning of the diet, binge eating at the first meal after fasting can occur, especially severe hunger or anxiety caused by not adapting to fasting.

In these cases, the next meal tends to be hypercaloric, with high levels of fat, carbohydrates or marked by an exaggerated intake of any type of food (even healthy ones), which leads to an imbalance in the body.

Above all, any diet or food change carried out without monitoring or indication by a health professional can bring dangers to the body.

As intermittent fasting still divides experts’ opinions, especially because there are not many studies on the consequences and results, immediate physiological changes need to be evaluated and measured, preventing future harm.

Health risks

Studies show a decrease in testosterone levels and changes in triiodothyronine, a thyroid regulating hormone, causing hormonal decompensation. Fees can be reinstated with the use of medications, should the need arise.

Due to the long period of fasting, the gastric wall may become irritated, aggravating stomach pains or developing gastritis .

Experts also point to the occurrence of occasional or recurrent binge eating episodes. Compulsion can manifest itself in the first meal after fasting, configuring itself as punctual episodes that tend to disappear when the diet is discontinued or, in more severe cases, evolve to a clinical picture of eating disorder, requiring psychological monitoring.

Contraindications

Few studies have been carried out on the subject and the long-term consequences are still relatively unknown. Despite presenting improvements in quality of life and weight loss, intermittent fasting can bring health risks and should not be practiced by:

Children and adolescents

Until the beginning of adulthood, the body is still developing and needs adequate sources of nutrients. Research on intermittent fasting does not demonstrate benefits for children and adolescents, who may suffer from nutritional deficiencies, anemia and developmental delay.

Pregnant and lactating women

During pregnancy, nutritional reinforcement is highly recommended to ensure the mother’s health and the baby’s good development. Long periods without eating can increase the risk of   hypoglycemia , fainting, dizziness and drops in blood pressure. In pregnant women, fasting can directly interfere with the baby’s pregnancy, resulting in formation and development problems.

During lactation, it is essential to maintain a balanced diet with nutrients. Breast milk is responsible for the child’s nutrition and immunological formation, being directly enriched by the mother’s food.

People with chronic diseases

Especially patients with diabetes and reactive hypoglycemia (frequent attacks of low blood sugar) should avoid intermittent fasting. In these cases, dietary regularity is essential to avoid health risks, stabilize blood glucose and prevent complications.

Chronic diseases or the use of medications that cause blood sugar levels to fall are also risk factors, and any type of restrictive diet without the express indication of the doctor or nutritionist is contraindicated.

Cases of eating disorders and anxiety

Patients who have already suffered from eating or psychological disorders represent risk groups. The disorders most susceptible to fasting are:

  • Bulimia;
  • Anorexia;
  • Food compulsion;
  • Generalized anxiety;
  • Depression.

Eating disorders are treated and controlled, but healing is hardly talked about. Therefore, the chances of relapse or worsening are quite high when the patient undergoes restrictive diets.

The adoption of long periods of fasting can also trigger emotional changes, intensify anxiety peaks and cause mood changes. For this reason, people undergoing psychological treatment are also discouraged from following the diet.

People with a BMI below 18

Despite low weight, sometimes being associated only with genetic conditions, who has a body mass index (BMI) below 18 should not undergo the practice of fasting, as there are risks of accentuating weight loss and causing damage to the body, as anemias and weakened immune systems.

In cases of anemia and migraine

When anemia is already diagnosed , intermittent fasting can aggravate the difficulty in absorbing nutrients, further weakening the body.

In addition, migraine and headache usually worsen when there are severe periods of fasting.

Common questions

Intermittent fasting slims?

There are some differences between health professionals. Unfavorable studies suggest that the body tends to adapt to periods of food restriction, reducing caloric expenditure to save energy.

In this case, food restriction can be seen as a warning signal to the organism, which considers fasting a critical period. As a survival mechanism, the body starts to store fat through metabolic adaptation, predicting that there will be other times of food shortage. Thus, in addition to parking the weight loss process, the body is more resistant to future diets.

Supporters of intermittent fasting, on the other hand, argue that there is frequent variation in caloric intake, which prevents the body from adapting, so fat burning remains active.

Can you practice physical activities while fasting?

Until the organism is relatively adapted to intermittent fasting (about 2 weeks), it is not recommended to combine physical activities. Even light or moderate exercise can be harmful after long periods without eating.

The most common complaints when performing fasting physical exertion are nausea, vomiting, pressure drop, hypoglycemia, headaches and dizziness . Over time, the practice of physical activities can be reconciled with fasting, but it is important to progress slowly, especially when the intervals between meals are long.

Some exercise practitioners report that fasting bodybuilding has good results for hypertrophy (increase in lean mass) and muscle definition. However, the practice is not a consensus among physical education professionals and coaches.

In addition, there are indications that fasting activities lead to weight loss by decreasing lean mass, which is denied by studies favorable to the diet.

Will I lose muscle mass while fasting?

There is research that suggests that long periods without food can lead to a decrease in lean mass, in which the body uses muscle tissues for energy.

However, studies in favor of intermittent fasting point out that the body burns only fat to make energy metabolism, not damaging hypertrophy or decreasing lean mass.

How to deal with hunger?

Maintaining hydration is essential for the proper functioning of the body. In addition, water helps to alleviate hunger and the desire to eat (which are different things, because hunger is physiological and the desire to eat is psychological). Other liquids can be added to the diet, such as coffees and teas, which greatly reduce the perception of hunger.

It is essential to moderate the first food after fasting, as this way the body avoids drastic changes in the receipt of food. Gradually, the body gets used to the reduction of food.

How should breaking the fast be?

The ideal is to opt for lighter and more functional foods, such as vegetables, fruits and lean proteins. Broths and soups are good options as they are light dishes. In addition to food, it is important to eat slowly and chew well to aid digestion.

Which foods give you more satiety?

Foods rich in fiber and protein help to stave off hunger for a longer time, due to longer digestion. Nutritionists suggest to include in the menu:

  • Pineapple;
  • Plums;
  • Oat;
  • Whole grains;
  • Broccoli;
  • Cress;
  • Fish and chicken;
  • White cheese.

What do comparative studies point to?

Still recent in the nutritional area, intermittent fasting divides the opinion of some professionals. Certain studies have pointed out the benefits for reducing body fat, decreasing abdominal circumference and improving metabolic rates, for example.

However, other research suggests that the benefits come from reducing the caloric intake caused by fasting. In other words, it would not be exactly the abstention from food that would bring benefits, but rather the healthier choices combined with the lower energy consumption.


Eating practices are part of a healthy routine and interfere with quality of life. Maintaining balance and moderation when choosing foods helps in the functioning of the body and mind.

Each person has different nutritional needs and restrictions, it is important to consider the subjectivity of each organism when composing a dietary routine. In addition to meeting biological needs, food should bring satisfaction and well-being.

Always consult a nutritionist!

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