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Understanding intermittent fasting

nouveautés, dans la bio, nutrition 04 January 2021

Praised by some, rejected by others, intermittent fasting offers a gentler method of fasting, alternating a phase of complete fasting and another of food intake on the same day or week. A restriction that can have positive effects, provided it is closely monitored.

What is intermittent fasting ?

Traditional fasting may be total, in which only water is allowed, or partial, with food intake limited to fruit and vegetable juice. In both cases, it extends over periods of several days and must be strictly supervised by health professionals; otherwise, it may cause discomfort, deficiency or inflammation, as well as muscle loss. Intermittent fasting, on the other hand, consists of alternating phases of fasting and food intake over much shorter periods of time. The most common example thus involves an eight-hour dietary intake period during the day, with fasting for the remaining sixteen hours. 

The different types of intermittent fasting

The most common intermittent fasts involve long food intake phases of fourteen to sixteen hours. They are popular for their simplicity and compatibility with an almost normal daily rhythm. There are, however, intermittent fasting patterns limiting food intake to six or even four hours a day, generally between 1 pm and 5 or 7 pm, which are more difficult to apply and maintain over time.

  • Intermittent fasting 8/16: food intake is possible without any particular restriction for eight hours, followed by sixteen hours of fasting. Followers generally choose to skip breakfast, delay it, or more rarely, bring dinner time forward. If breakfast is taken at 10 am, dinner must be finished by 6 pm.
  • Intermittent fasting 10/14: the food intake phase is extended to a period of ten hours. The principle remains the same, but the hours are more flexible. If breakfast is taken at 10 am, dinner can be finished at 8 pm.


Weekly intermittent fasting

By extension, other intermittent fasting methods operate on a weekly basis. Whereas daily fasting alternates fasting and food intake over a day, weekly fasting alternates restriction and freedom to eat over a week. Halfway between fasting and dieting, it is based on a calorie deficit, similar to traditional weight loss diets. As such, it is much more controversial, particularly in France, and should be approached with caution, on medical advice.

  • Intermittent fasting 5/2: the method consists of alternating five days of normal food intake with two days of dietary restrictions. During these two freely set but consecutive days, intake must be limited to 500 calories per day for women and 600 for men.
  • Intermittent fasting 1/2, or ‘alternate day fasting’: like the previous one, the balance is over the week rather than over a day. Very popular in the United States, the principle consists of alternating a day of normal food intake and a day of fasting with 500 calories.


Which method of intermittent fasting is best for you ?

It all depends on your pace of life! The main thing is to choose a method tailored to each person's habits, as each type of fasting requires more or less strict discipline. 

  • Those who love dining with family or friends therefore largely favour fasting 16/8 or 10/14, which allows you to have dinner by skipping or postponing breakfast. 
  • Fasting 1/2 is less compatible with daily life, unless you organise your social life according to the days of restriction. 
  • The 5/2 version, on the other hand, is suitable for those who are prepared to follow a strict diet for two days in a row, most often at the weekend, for more freedom during the week.


Fasting and food freedom

Intermittent fasting alternates between normal food intake and fasting or restriction. But be careful - the lack of restrictions during ‘normal’ periods does not mean a total lack of monitoring! To maintain the benefits of the method, food intake must remain balanced and without excess, even without any particular dietary restrictions.

Why practise intermittent fasting ?

The principle of daily intermittent fasting derives from the natural physiological rhythm of fasting during the night. By lengthening this phase, the body has more time to absorb and process the food ingested. Conversely, by reducing the period of food intake, the amounts ingested are, in the vast majority of cases, spontaneously reduced.

One of the main consequences of intermittent fasting is therefore weight loss, although it is not a diet in the true sense of the word. The daily method, which is popular among its followers for its simplicity, is for many people a way to regain a healthier relationship with food by abandoning calorie counting. By giving the body time to eliminate food before eating again, it allows you to regain feelings of hunger and fullness, and therefore a more intuitive food intake. Intermittent fasting also helps to detoxify the body. 

Precautions to take before fasting

Are you thinking of trying intermittent fasting? Whenever possible, consult a specialist beforehand to assess the situation and set up a tailor-made programme with no risk to health. Otherwise, start gently and listen to your body. 

Before adopting a strict time schedule, push breakfast back by one hour and then push dinner forward by one hour if you usually eat it late. Don't forget to drink water, especially during the fasting phase. Do not compensate for the fasting phases with higher calorie intake during the day. 

In any case, monitor your sensations and take your time - your body also has to get used to the change. And even if weight loss often results, don't think of intermittent fasting as a diet, at the risk of expecting too much too quickly and losing many benefits. To be useful and lasting, the rhythm must seem almost natural, with no tension or discomfort. If periods of fasting or restriction lead to stress, feelings of discomfort or increased hunger the rest of the time, and thus an increase in food intake, the method chosen is not suitable.

When should intermittent fasting be avoided ?

Intermittent fasting is not suitable for pregnant or breastfeeding women, for elite athletes, or for people with health problems or eating disorders. If you have any doubts, talk to your doctor or a food professional before making any changes.