By depriving your body of food for several hours, intermittent fasting aims to purify your body and lighten it by a few pounds. What are the benefits? Are there any health risks? How to get started? Raphaël Gruman, nutritionist, explains.
What is intermittent fasting?
For millennia, for spiritual or religious reasons, men have deprived themselves of food for atoning purposes. Today, this practice, which has become fashionable, is done with a concern for well-being and health. "The purpose of intermittent fasting is to purify your body of junk food, its excesses, and the toxins generated by pausing the emunctorial organs, which are the liver, kidneys, and skin," explains Raphaël Gruman, nutritionist.
The principle is to deprive yourself of food for 12 to 16 hours maximum, which is like skipping a meal. "During this fast, the body uses glucose circulating in the blood or liver to continue to function well," says Raphaël Gruman. If it extends beyond 3 days, it comes to draw from the reserves of lipids and proteins, mainly the muscles. The key is a renewal of the body, but also weight loss and a way to fight against certain diseases.
How does it work?
Also called 'fasting' in English, the principle of intermittent fasting is to stop eating for 12 to 16 hours straight. "For example, we have dinner, but we skip breakfast the next morning, to eat again only at lunch, says our expert. But it is up to everyone to adapt it according to their convenience. Thus, if you have intense activity during the day or breakfast is your favorite meal, you can perfectly deprive yourself of dinner. Fasting is then organized as follows: breakfast, lunch, and snack. Food intake stops around 5 p.m., only to resume around 7-8 a.m. The next morning. If solid food is removed, it is important to maintain good hydration, i.e. The consumption of 1.5 to 2 liters of liquid (water, tea, herbal tea, broth ...).
How long does it last?
There is no strict duration. "As part of weight loss, I recommend to my patients an intermittent fasting of a full week," says Raphaël Gruman. On the other hand, if it is in view of digestive well-being, a fast of one to two days a week is more than enough.
Who is it for?
Only to healthy adults. This eating habit is also not recommended for pregnant and breastfeeding women, children, and adolescents because it could lead to stunted growth, and for the elderly that it can weaken even more.
What foods are allowed?
On the meals of the day not fasted, all foods are allowed: cereals and legumes, meat, fish and eggs, dairy products, fruits and vegetables, and even pastries and confectionery.
On the other hand, on the fasted meal, only water, broths, and herbal teas are allowed.
What foods are prohibited?
On the two or three main meals, if intermittent fasting aims at weight loss, sweets, pastries, confectionery ... Are to be avoided.
During the fast meal, solid feeding is prohibited. "Coffee is also not recommended because it requires digestion work in the liver," says Raphaël Gruman.
Is intermittent fasting easy to follow?
Yes, if it is done in a short phase. When hunger is felt, it can be compensated by the absorption of liquid: by filling the stomach, they cut the urge to eat. Keeping your mind busy also allows you to turn away from your hunger.
Finally, by going to bed early, fasting for the evening meal is easier. "In addition, without receiving food, the body adapts: it transforms fat reserves into ketone bodies, substances that replace glucose," explains our expert. The latter brings a certain satiety, makes it euphoric, and no longer encourages the body to demand food.
What are the health benefits?
By relieving the body of toxins that clutter it, intermittent fasting makes it possible to correct states of fatigue: sleep improves from the 1st day and tone returns after the 3rd. The complexion also clarifies and the skin is healthier. "It allows a weight loss of the order of 1 kg per week, as part of a fast followed over a full week," says the nutritionist.
Fasting would also reduce pain, stiffness, and NSAID consumption in people with rheumatoid arthritis1. This eating method would also improve concentration, according to a study published in the International Journal of Obesity2 by promoting the renewal of neurons in the brain.
Is it dangerous for health?
Performed for too long and without medical supervision, fasting could cause deleterious effects on the body. In the first place, dizziness and headaches. If it continues, it can cause muscle wasting and deficiencies in macronutrients including protein, as well as minerals, such as iron, and cause anemia.
It can also be harmful to the heart: some heart problems, especially arrhythmias are a contraindication to overly restrictive diets. This risk exists, especially when the restriction lasts too long because it weakens the heart muscle, according to the High Authority of Health3. Consult your doctor and cardiologist before you start.
What are the effects in the case of cancer?
On the anti-cancer effects, opinions are still divided. Many animal studies have already shown that starvation before chemotherapy can preserve healthy cells while making cancer cells more vulnerable to treatment. In 2017, the Inca looked into the issue and issued an opinion that "the overall analysis of available scientific knowledge, in particular clinical knowledge, does not allow to conclude on the interest of these regimes in cancer prevention or during treatments. In cancer patients, the loss of weight and muscle mass observed in clinical studies suggests a risk of worsening undernutrition and sarcopenia, two pejorative prognostic factors recognized during treatments.
But a study published in June 2020 in the famous journal Nature revives the debate5: carried out on 129 breast cancer patients, it shows that those who had been deprived of food for three days before and three days after their chemotherapy session had responded better to this treatment than those who had continued to eat normally.
"Fasting can be an ally in the fight against cancer," says Raphaël Gruman. However, because this disease and its treatments can also lead to malnutrition causing a deterioration in the general condition, if the patient wishes to follow it, he must imperatively be supervised by a health professional.
Benefits of intermittent fasting
- If it is followed over a long time because food intake is spread over two or even three meals, this eating pattern is not unbalanced and does not cause deficiencies or fatigue;
- It is a health ally: it improves the digestive system, sleep, and skin quality, brings a boost of tone, relieves pain in case of rheumatoid arthritis, and ensures the proper functioning of the brain;
- It allows you to lose weight, about 1Kg per week;
- It is compatible with special diets such as vegetarian, vegan, gluten-free, lactose-free, salt-free, kosher and halal;
- It may be short-lived.
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