Intermittent fasting, the complete guide

[Article updated on 10/11/2023]

If for some people staying in shape has become a fundamental point in terms of their well-being, they do not hesitate to try all kinds of activities or diets in order to stay slim. There are many sports and diets to lose weight, but the question is: are they really effective? Today, to clarify certain ideas, discover through this complete guide everything you need to know about intermittent fasting: principle, effects, methods to adopt, advantages…

Before reading on

I’m not an expert in this field, but I am passionate about nutrition and health.

The articles you’ll find on my site are the result of in-depth research that I’d like to share with you. However, I would like to stress that I am not a health professional and that my advice should in no way replace that of a qualified physician. I’m here to guide you, but it’s important that you consult a professional for specific questions or medical concerns. Your well-being is important. So be sure to consult the appropriate experts and take the best possible care of yourself.

For those who prefer the video format, I have prepared a short 5-minute video for you which summarizes this article and everything you need to know about the main types of intermittent fasting. It’s right here (for those who prefer to read, you just have to scroll a little :):

Introduction to intermittent fasting, a healthy solution to lose weight?

Also called intermittent fasting or intermittent fasting, intermittent fasting is a particular slimming diet which consists of successive phases of eating and phases of fasting, fasting boiling down to abstinence from food and reduction of intake. in water. According to certain studies carried out by specialists, this diet has positive effects on the brain and the body, and contributes to greater life expectancy.

One of the latest trends in fitness and health, this diet allows you to effectively lose weight, but also to adopt a healthy lifestyle and have better health. It is thus based on cycles of eating and fasting, and not on foods to favor or avoid. Intermittent fasting comes in different methods, some of which involve fasting for 16 hours straight and others for 24 hours or even twice a week.

Since his existence, man has known fasting, in one way or another. In reality, this is in some cases due to lack of food to eat or religious tradition. When you think about it, in the past, our ancestors did not have large areas at their disposal and even fewer refrigerators to stock up on. In these cases, the human body adapts to the situation and can continue to function without having to consume food, even over long periods of time.

Moreover, humans fast 6 to 10 hours each night and this is a natural mechanism. Food deprivation can thus be prolonged in various ways: eat a lower-calorie meal once every two days, fast for at least 24 hours once a week, skip one meal every day or eat to your full content for 5 days and eat little the remaining two days.

In short, intermittent fasting is an effective and healthy cyclical eating pattern. Its principle is to alternate periods of fasting and periods of eating according to a precise plan.

Man already fasts 6 to 10 hours while sleeping
Man already fasts 6 to 10 hours while sleeping

How to put intermittent fasting into practice?

Known for several years now, this type of diet is carried out using distinct approaches. These all share one thing in common: that of dividing the day or week into a cycle of fasting and meals. So far, there are 6 intermittent fasting procedures.

You can read the rest of the article, or discover the 6 methods of intermittent fasting in video:

#1 – The 5:2 fast: deprive yourself of food two days a week

As its name might suggest, the 5:2 diet is a diet based on eating normally for 5 days then reducing calorie intake for the remaining 2 days. This diet is therefore a weekly cycle. To lose weight without going through slimming tablets or some natural appetite suppressants not always effective, and above all enjoy the benefits of this diet, know that the number of calories recommended for a meal is set at 250 for women and 300 for men.

#2 – Intermittent fasting 16/8 or fasting

How to do 16/8 fasting? This dietary ritual consists of depriving yourself of food for 16 hours then eating for the following 8 hours. Unlike the 5:2 fast, this one is held on a daily cycle. To put this diet into practice, you can for example skip breakfast then eat at midday and have dinner around 8 p.m. You can also have a small snack between the two meals, if you wish.

According to studies undertaken on this method, it seems that women are more willing to tolerate a 13 or 14 hour fast. For people who have a morning appetite, this diet could pose some problems. But over time, the body will gradually be able to adapt.

As part of this diet, it is essential to opt for healthy foods and non-calorie drinks, such as black coffee or water. Otherwise, fasting will not provide the desired effect, in this case losing a few pounds. In fact, you are advised to eat foods rich in carbohydrates when you are engaged in physical activity and to consume good fats when you are not physically active.

The advantage of this fast is that the duration of meal deprivation is relatively short. This type of intermittent fasting is in fact more easily assimilated by the body than other methods.

#3 – Fasting every other day

This other type of diet is based on fasting every other day. If you are just starting a weight loss diet, don’t choose this one. It certainly brings many health benefits, and this has also been proven by studies. But it requires adapting to a fairly drastic pace, which involves sleeping on an empty stomach at night.

#4 – 24-hour deprivation

This method consists of eating nothing for a period of 24 hours, once or twice a week, then eating normally on the remaining days. In particular, you can start your fast on Monday morning at 8 a.m. and end it the next day at the same time.

During this form of intermittent fasting, you of course have the option of drinking water as well as any other low-calorie beverage. However, you cannot eat solid food.

If you have adopted this diet to lose weight, the number of calories consumed daily must be the same every day. So, if you took 250 calories today, you should take an equivalent amount the next day.

Furthermore, there is no rule imposing the foods to favor when you are outside of the fasting period. In other words, you can perfectly enjoy a slice of cream pie without feeling guilty. You can also postpone your fast if, for example, you have to attend a family dinner.

Fasting for a whole day can be difficult for some people. But with willpower and habit, you will quickly get used to it.

#5 – The Warrior Diet

During this type of diet, you are recommended to consume plenty of raw vegetables and fruits, but also soup and non-fatty proteins, during the day. At the end of the day, you have a good 4 hours to enjoy a hearty meal.

When you finish your fast, make sure to eat good fats as well as foods rich in protein afterwards. If after that you are not yet full, add more carbohydrates. With the warrior’s feast, the principle is in fact to eat food in small quantities throughout the day and then eat to satiation to end the fast.

Among the intermittent fasting techniques, this diet is undoubtedly the most restrictive, because it requires knowing how to control yourself even if you are extremely hungry.

Favor dried fruits
Favor dried fruits

#6 – Spontaneous intermittent fasting

This form of intermittent fasting is probably the least restrictive. And for good reason, you don’t have to stick to a specific plan. You can actually practice it at any time, when you feel the need.

Even if you follow your own pace, you enjoy the benefits that fasting can provide. In short, the human body is perfectly capable of supporting long periods of fasting. However, you need to make sure you eat healthy foods when you need to eat.

The multiple effects of intermittent fasting

There are many effects resulting from intermittent fasting. Although they are mostly positive, there are still some undesirable effects. Regardless, when done at a regular pace and correctly, fasting provides several health benefits.


With intermittent fasting, you can absolutely lose weight. When you eat little food and burn a lot of calories, the pounds will undoubtedly decrease. For this type of diet, as you will have noticed above, several solutions are possible: limit the quantity of food while practicing a sporting activity, resort to fat burners as the PhenQ, … But the simplest is of course reducing the number of meals.

It seems trite or absurd, but the more you reduce the number of your meals in a day, the fewer calories you consume. And this, without you having to make great efforts or play sports.

With intermittent fasting, calorie intake drops by an average of 30%, which equates to 1 kilo less per week.

Obviously, intermittent fasting helps you lose weight, since you eat less
Obviously, intermittent fasting helps you lose weight, since you eat less

Less insulin produced

Why do we mention insulin when we talk about diet? Because insulin plays a significant role in weight gain. This hormone is responsible for storage. When you are overweight, insulin production is greater and the body tends to resist it.

To lose weight effectively and reduce food storage, it is essential that insulin levels drop. If you do not eat for hours in a row, insulin production declines instantly, but also lastingly.

Thus, the body gradually gets used to functioning with a low amount of insulin. This is when you gain muscle mass while having less storage. At the same time, the feeling of fullness is faster.

Less risk of diabetes

When a person has diabetes, their lifestyle and especially their diet must be monitored very closely. The main problem is having too much sugar in the blood and not enough insulin to build it up. If fasting improves insulin sensitivity, this helps prevent diabetes.

Improved circadian rhythm

The circadian rhythm triggers the secretion of hormones at a specific time of the day, which makes you get up in the morning, feel hungry at lunchtime and fall asleep in the evening. In certain subjects, this rhythm is disrupted. Hunger may still be present and at night you may suffer from insomnia.

By practicing alternate fasting, this rhythm can improve. By setting meal times and reducing the eating period, the body adopts a new organization. As the days go by, you get into this habit and then you come to the point where your circadian rhythm is completely restructured. You are only hungry at lunchtime, you sleep better while in the morning, you are full of energy.

Increased production of growth hormone

With age, it becomes complicated to produce growth hormone or fitness hormone. This is one of the reasons why it is difficult to lose weight as you age. Thanks to this hormone, it is easier to gain muscle mass.

To increase the amount of this hormone, you can engage in physical exercise, which will at the same time allow you to stay in shape. But fasting is simpler and less restrictive. The production of growth hormone is in fact greater when you do not eat. According to some studies, in 24 hours, in men it increases by 2000% and in women by 1300%. And in addition to helping to stay in shape, this hormone delays the aging process.

Reduction in fat mass

Weight loss is beneficial, but is futile if you lose water and muscle at the same time. Fortunately, by fasting you essentially lose fat. This is particularly due to the hormones mentioned above. With more growth hormone and less insulin, you lose more fat and promote its use for energy.

Thanks to intermittent fasting, muscle mass is preserved while fat decreases. This contributes to weight loss, as the muscles absorb the fat mass.

Less depression and anxiety

The practice of fasting would help you to be more calm, serene and in good shape. This would help keep you in a good mood and avoid any form of anxiety, stress or depression. This would have to do with sleep and hormone production, points improved by intermittent fasting.

Fasting, in addition to helping to lose weight, would reduce anxiety
Fasting, in addition to helping to lose weight, would reduce anxiety

Greater life expectancy

Taking into account all the benefits mentioned above, it is not surprising that this way of eating promotes lifespan. This is because each point cited has a certain positive impact on health as a whole.

Basically, intermittent fasting can only be beneficial for your health and for losing weight. After many, many studies, it has been repeatedly shown that low calorie intake is good for your health. This is precisely the principle of fasting: eat little, for a short period of time and lose weight.

So what are the unwanted side effects?

The main side effect of this type of diet is hunger. Intermittent fasting can also make you feel weak and your brain functioning slower than on other days. It can also cause lack of sleep, dehydration or even irritability.

Don’t worry, because this phase is temporary. It may take some time for your body to adapt to this diet, but over time you will get used to it.

Still, if you have a medical history, it is strongly recommended that you consult your doctor before deciding to follow this type of diet. This is mainly valid if you suffer from diabetes, if your blood pressure is low, if you are on medication, if you are underweight. This diet should also be avoided if you are a woman and want to have a child, if you are pregnant or if you are breastfeeding.

In any case, there is nothing harmful about intermittent fasting. If you are in good shape and eat well in general, nothing can stop you from trying this way of eating.

How to start this diet?

Without realizing it, you may have already adopted intermittent fasting at some point in your life. Have you ever gone to bed at night with dinner and then not eaten anything until lunchtime the next day? If the answer is “yes”, it means that you have already followed the 4 p.m. fast.

All this to tell you that if you are at the beginning stage of this type of diet, you have nothing to worry about, since your body will easily adapt to the diet schedules. To get started, first try the 16/8 diet. If you feel comfortable during the fast, you can move on to the next level. You may choose to take a more drastic approach, such as fasting for 24 hours once or twice a week, or reduce calorie intake one or two days a week.

But the best way to start is to skip meals occasionally, when you’re not hungry or busy. In fact, it is not essential to follow a very specific plan to obtain the desired effects. So choose the method that best suits your lifestyle and schedule.

Frequently asked questions about intermittent fasting

Before starting this diet, many people ask themselves certain questions. Here are the most frequently asked questions regarding this type of diet.

It seems that breakfast is the most important meal of the day, would it be reasonable to skip it?

If you are very active, it is true that breakfast should not be neglected. However, if you eat properly the rest of the day, skipping this meal will do you no harm.

Are drinks allowed during the fast?

Certain drinks can be taken during the fasting period: water, tea, coffee and any other non-caloric drink. If you drink coffee, don’t add sugar. A little cream or milk won’t hurt you.

Taking tea can be considered during intermittent fasting
Taking tea can be considered during intermittent fasting

Are food supplements compatible with intermittent fasting?

Nothing stops you from taking some food supplements like those based on Hoodia Gordonii for example. However, during a fasting period, this may be unnecessary, as supplements work more effectively when you take them with meals.

Working while fasting, is it dangerous?

You are not in danger if you fast while you have to work. Physical exercises on an empty stomach are in principle not harmful. You just need to be careful not to try too hard.

Can children start intermittent fasting?

It is preferable not to adopt this diet in children. As he grows, he must eat at a constant pace and in a healthy manner, without skipping meals.

The final word

Intermittent fasting is not a mandatory diet. It is simply one of the many ways of eating that can contribute to good health. If you don’t want to lose weight, but just stay in shape, the main thing is to eat good food, take part in a sporting activity and prioritize sleeping time. However, fasting can be beneficial for you if you want to lose weight while staying in shape.

Also, this diet may be effective for some people and may not be effective for others. But it doesn’t cost you anything to try. If you are comfortable with young people, they can be a powerful weapon against weight gain.