Intermittent fasting can help you lose weight. But not only. What are its other health benefits? Which fast to choose? How to practice it? What to eat during a fast. The answers of the dietician-nutritionist.

Intermittent fasting: should you go for this slimming method?

What is intermittent fasting?

Intermittent fasting is the fact of voluntarily depriving oneself of food during certain time slots. Its purpose is to cleanse the body, to free it from accumulated toxins in order to feel better in one's body but also in one's mind.

Fasting is an ancient practice. Lent, Yom Kippur... are fasts.

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

Yes," answers Ysabelle Levasseur, dietician-nutritionist. Intermittent fasting can help you lose weight, but it also has other therapeutic objectives.

Without knowing it, people who do not eat breakfast in the morning, and wait until lunch to eat are doing intermittent fasting daily.

The benefits of intermittent fasting

"Some patients experience the following effects," says Ysabelle Levasseur.

- It improves overall health.

- It allows you to be more concentrated.

- It allows you to digest better.

- It gives you more energy.

- It can reduce high blood pressure.

- It helps to lose body fat and reduce waistline.

Intermittent fasting: what are the risks? What contraindications?

Intermittent fasting has its advantages, but also its disadvantages.

The disadvantages of intermittent fasting

It can :

- cause headaches because there is a change in metabolism, which forces the body to produce energy from what is stored in the liver.

- limit social life.

- aggravate certain diseases (cancer, Covid-19...).

- maintain eating disorders, already present.

Who should not fast?

Fasting is not a harmless practice. It is therefore not suitable for everyone.

The following people should not fast:

  •     children;

  •     people under diabetic treatment including insulin;

  •     people who are under extreme stress because it is not the right time;

  •     people with an acute illness;

  •     people who have to take a medication at certain times (in the morning at breakfast, difficult if fasting without breakfast).

Does intermittent fasting allow me to lose weight permanently?

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

    Some people lose weight quickly in 15 days to 3 weeks, but put it back on quickly, or even more, as soon as they return to a 'normal' life, explains the dietician.

How to maintain weight loss?

There is no magic! Weight loss can only last if the person eats according to his or her needs, by trying to eat as much variety as possible, while enjoying the food," explains Ysabelle Levasseur. Without forgetting also the practice of a regular physical activity".

What is the most effective intermittent fasting?

It is impossible to say! Because there is no study to date that has studied all the fasts and their effects on weight in order to draw conclusions," warns the dietician.

Indeed, the studies carried out on fasting have been isolated, on small samples of less than 100 people. They are therefore not transposable to the whole population. "Especially since the authors of these studies always conclude that fasting is beneficial," says Ysabelle Levasseur.

Be careful with women!

"Only one study compiled 71 studies on fasting, without distinguishing the types of fasting followed. It underlined that the results obtained differed according to the sex, specifies the dietician. In women, in particular, the results show that, in the long term, fasting can induce overweight and insulin resistance.

On the other hand, in men, the results would be beneficial. "Yes, men have seen their weight, their fat mass decrease and their cardiovascular health improve," says the dietician.

The different methods of intermittent fasting

Before we talk about the different intermittent fasting options, a word of warning. Dry fasting puts a person's vital prognosis at risk very quickly. It should only be followed under medical supervision and validation.

For intermittent fasts, it is important to respect the period without eating and to eat only in the dedicated time slot.

The 16/8 fast

"This is generally the one we start with," says Ysabelle Levasseur.

  •     What does it consist of? "The meals are taken in a time slot of 8 hours, then there is a fasting phase of 16 hours," says the dietician.

  •     If you skip dinner, you have a last meal around 5 p.m. and eat again around 9 a.m. the next morning," explains the dietician. If you skip breakfast, you fast until noon and have dinner around 8 p.m."

Fasting 36/12

"This fast is to be practiced if you can stand fasting", warns Ysabelle Levasseur.

  •     What does it consist of? "We eat only one day out of two over a 12-hour period," says Ysabelle Levasseur.

  •     How do you do it? "In practice, we eat from 8 a.m. to 8 p.m., then we fast for 36 hours continuously, either the following night, the following day and then another night. We only eat again the day after at 8 am", explains the dietician.

The 20/4 fast

"It is built on the same principle as the 16/8 fast", says Ysabelle Levasseur.

  •     What does it consist of? We eat at a 20/4 rhythm, that is to say 4 hours to eat followed by 20 hours of fasting, explains the dietician.

  •     How does it work? "We eat at 2pm and have dinner at 6pm. Then we fast the following night and the next day until 2 p.m., when we can eat again." 

Which foods should be chosen for fasting?

Preference should be given to protein-rich foods (meat, fish, eggs, legumes, cheese, etc.) and lipids (oils, oilseeds) rather than carbohydrates," advises Ysabelle Levasseur. As for drinks, we opt for water. Herbal tea, tea and coffee are allowed if they are not sweetened. And we avoid caffeine in the evening (not after 5 p.m.) because it can prevent us from sleeping. 

An example of a menu for the 16/8 fast

  •     In the morning: when you wake up, drink water, herbal tea, tea or coffee (unsweetened) until your first meal to avoid feelings of hunger.
  •     First meal at noon: "Make sure it is low in carbohydrates," advises the dietician.
  •     We combine proteins and vitamins. This gives: fatty fish + green vegetables + nut oil + goat cheese + herbs and spices.
  •     Afternoon snack: 1 handful of oilseeds + 1 fresh fruit.
  •     Dinner (8:00 p.m.): "It is rich in protein and accompanied by vegetables," advises the dietician. Bell pepper omelet + tomato salad with olive oil and herbs + 1 yogurt.

Two breakfasts for the day after the fast

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


  •     2 organic or blue-white eggs
  •     1 handful of fresh spinach/zucchini + 1 tablespoon of olive oil/colza blend
  •     1 large tomato
  •     30 g feta or pecorino cheese
  •     salt and pepper

How long can you fast?

    The 16/8 fast is the only one that, socially, can become a way of eating daily, warns Ysabelle Levasseur.

And the others? "They are to be done when you have time to rest, especially the first days, advises the dietician. The minimum time depends on what you are looking for. It varies from 15 days to 2 months. It is important to adapt to each case.

Good fasting, and be careful!