What is Intermittent Fasting? How is it done?

What is Intermittent Fasting?

There are many types of food fasting: dry fasting, water fasting, intermittent or partial fasting…

Intermittent fasting is the deprivation of food for certain periods of time . Its purpose is to cleanse the body and remove accumulated toxins so that you feel better both in your body and in your head.  

This is why intermittent fasting is popular today because of its ”  detox effect  on the body . It is also applied by people who want to lose weight because it will have shown some effectiveness in losing weight. But do we really know what effect intermittent fasting has on our health and well-being? An expert answers us.    

Does intermittent fasting make you lose weight? What other benefits are there?

“Yes,” replies dietitian nutritionist Ysabelle Levasseur. “Intermittent fasting may aid weight loss , but it also has other therapeutic goals.” People who unwittingly skip breakfast and wait until lunch engage in intermittent fasting daily. 

benefits of intermittent fasting

“Some patients experience the following effects,” says Ysabelle Levasseur.

  • Improves overall health  ; 
  • It allows you to concentrate more ; 
  • Provides better digestion  ;
  • Gives more energy  ;
  • It can lower  high blood pressure ; 
  •  It allows  you to lose fat mass and slim your waist . 

Intermittent fasting: what are the risks? What contraindications?

Intermittent fasting has both advantages and disadvantages.

The harms of intermittent fasting

  • It causes headaches because there is a change in metabolism that forces the body to produce energy from those stored in the liver;  
  • Limit social life
  • Exacerbating some diseases ( cancer , Covid-19 etc.); 
  • Resume already existing eating disorders . 

Who should not fast?

Fasting is not a trivial practice. Therefore, it is not suitable for everyone.

Here are the people who should not fast:

  • People who are being treated for diabetes , including insulin  ;   
  • People who are overly stressed because it’s not the right time; 
  • People suffering from an acute illness;
  • People who have to take medicine at certain times (it is difficult to fast in the morning without breakfast).  

Does intermittent fasting make you lose weight permanently?

So variable! It all depends on each individual and their metabolism.

Some people lose weight quickly in 15 days to 3 weeks, but as soon as they return to a ‘normal’ life, they regain it quickly, or even more, explains the dietitian.

How to maintain weight loss?

Nothing magical! “Weight loss can only continue if the person eats according to their needs, tries to eat the most variety of vegetables possible , namely vegetables ,” explains Ysabelle Levasseur. “Not forgetting the practice of regular physical activity”.  

What is the most effective intermittent fasting for weight loss?

It’s impossible to say! Why ? “Because to date, no studies have examined all fasts and their effects on weight,  ” warns the dietitian.

As a matter of fact, studies on fasting were carried out in isolation, on small samples of less than 100 people. Therefore, they cannot be transferred to the entire population. “Especially since the authors of these studies always concluded that observed fasting practice is beneficial! ‘, says Ysabelle Levasseur.

Attention women!

“A single study compiled 71 studies on fasting, regardless of the types of fasting followed. He pointed out that the results obtained differ according to gender. “The results show that long-term fasting can cause excess weight and insulin resistance, especially in women.”

On the other hand, in humans, the results will be beneficial. “Yes. Men, on the other hand, saw their weight, fat mass decreased and their cardiovascular health improved,” explains the dietitian.    

How to do intermittent fasting: different methods

A caveat before we talk about the different types of intermittent fasting. Dry fasting puts a person’s life at risk very quickly. It should only be followed under medical verification and observation.  

For intermittent fasting, it is important to respect the time without eating and only eat within the allotted time slot . 

  • What does it consist of? “  Meals are taken in an 8-hour timeframe, followed by a 16-hour  fasting phase,” the dietitian says.  
  • How is it done? Either skip dinner or breakfast. “In the event that dinner is removed, we eat one last meal around 5pm and eat again around 9pm the next morning,” the dietitian explains. If we do not have breakfast, we fast until noon and eat dinner around 8 pm.  
  • What does it consist of?  “We only eat every other day for a 12-hour span,” says Ysabelle Levasseur  ; 
  • How is it done?  “In practice, we eat from 8 am to 8 pm , then fast for 36 hours straight , the next night, the next day, and then another night. We only eat at 8 am the next day, ”explains the dietitian.  
  • What does it consist of?  We eat in 20/4 rhythm, that is, 4 hours of food and then 20 hours of hunger, explains the dietitian;  
  • How is it done?  ”  We have dinner at 2 pm and dinner at 6 pm. Then we fast until 2 pm the next night and the next day, then you can eat again.”

Intermittent fasting: what to eat? What foods are chosen?

 Ysabelle Levasseur says , “ Foods rich in protein (meat, fish, eggs, legumes, cheese, etc.) and lipids (oils, oilseeds) should be preferred instead of carbohydrates .” As a beverage, we prefer water. Herbal tea, tea and coffee are allowed if they are not sweetened. And we avoid caffeine in the evening (not after 5pm) because it can interfere with your sleep”.      

A sample menu for fasting 16/8

  • Morning  : Drink water, herbal tea, tea or coffee (without sugar) until the first meal to avoid the feeling of hunger when you wake up;
  • The first meal at noon  : “We pay attention to the fact that carbohydrates are low,” advises the dietitian.
  • Proteins and vitamins are combined. Which gives: fatty fish + green vegetables + walnut oil + goat cheese + herbs and spices;
  • Snack  : 1 handful of oil seeds  + 1 fresh fruit;
  • Dinner (8pm)  : “It is rich in protein and comes with vegetables ,” the dietitian advises. Pepper omelet + tomato salad with olive oil and herbs + 1 yogurt. 

Two breakfasts for the day after fasting

  • 1 or 2 organic or blue-white heart eggs;
  • 3 to 4 slices of bacon or ham;
  • 1 tablespoon of olive/rapeseed oil mixture;
  • 200 g mushrooms/ zucchini /tomatoes;
  • Parsley.


  • 2 organic or blue-white heart eggs;
  • 1 handful of fresh spinach  /pumpkin + 1 tablespoon of olive/rapeseed oil mix;
  • 1 large tomato;
  • 30 g of feta cheese or pekorino;
  • Salt and pepper.

How long can you fast?

 “It should be done when you have time in front of you so that you can rest, especially in the first days,” the dietitian advises. The minimum time depends on what you are looking for. It varies between 15 days and 2 months. It is important to adapt to the situation,” he said.

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