Intermittent Fasting: Definition & Explanations

Intermittierendes Fasten: Definition & Erklärungen

If you want to lose weight, you often change your diet - mostly reluctantly. As soon as the yo-yo effect kicks in, you're back to square one. With intermittent fasting, a form of nutrition has emerged that allows you to eat anything you like. Fasting is then carried out for a certain period of time (hours or days) and the body is thus stimulated to burn fat.

This glossary entry shows all the advantages and disadvantages and explains the diet in detail. Since there are different forms of intermittent fasting, there is a suitable method for every everyday form.

the essentials in brief

  • Intermittent fasting is not a diet - it is a form of nutrition. It can be maintained for weeks, months and even years, thus promoting the health of the body. It has been proven to have positive effects on weight loss, health and appetite suppression.
  • There are different forms of intermittent fasting: 2-day diet, 5:2 diet, alternate-day fasting and dinner-cancelling. In the last form, a single meal, dinner, is skipped. The other forms deal with phases of eating and phases of fasting.
  • The advantages of intermittent fasting are above all: time flexibility, low yo-yo effect, no strict regulations, better blood and cholesterol levels, flat stomach and appetite suppression.

Glossary entry: The term intermittent fasting explained in detail

In this part, all questions regarding the term intermittent fasting will be answered.

What is Intermittent Fasting?

Intermittent fasting, or IF for short, is a form of fasting that is said to have health-promoting effects on the metabolism (1). In this form, food is avoided for days or hours.

Why do you fast intermittently?

Many who use intermittent fasting want to lose weight - and without strict dieting. The difference between intermittent fasting and traditional dieting is that there are no rules as to what is and isn't allowed. Instead, more attention is paid to the times and phases in which food is consumed. This makes this method very attractive to many.

With intermittent fasting, nothing has to be sacrificed. Only the phases in which food is consumed are changed.

bread on a plate

With intermittent fasting, phases are defined exclusively for eating (Image source: congerdesign / Pixabay).

How does intermittent fasting work?

With intermittent fasting, you go without food for days or hours. There are different forms:

  • 2-Day Diet: This diet was originally intended for cancer patients (2). This should make it easier for you to lose weight. It was developed by a nutritionist and an oncologist. Within a week, only 650 kilocalories are consumed on two consecutive days. Food choices should be low-carb and high-protein. On the remaining five days, it is best to eat a Mediterranean diet.
  • 5:2 diet: This form of fasting is one of the most well-known. Eat normally five days a week. Above all, the motivation should remain and not fade away due to strict regulations. A quarter of the usual energy intake is consumed on the two fasting days. On these days you should mainly eat vegetables and whole grains as well as protein-rich foods. Adequate fluid intake is also a part of this (3).
  • Alternate day fasting: This form is also known as "eat-stop-eat". The form is based on the fact that only 25% of the usual energy intake is consumed on the fasting days. On the other days, however, there are no restrictions (4).
  • Dinner-cancelling: With this form of fasting, dinner is omitted two to three days a week. Instead, only water, tea and other calorie-free drinks are consumed in the evening. The meal break of around 14 hours before breakfast is said to help people lose weight and improve their sleep quality (5).

What are the advantages and disadvantages of intermittent fasting?

This table summarizes the pros and cons of intermittent fasting.

Who is intermittent fasting suitable for?

In principle, intermittent fasting is suitable for everyone. Our bodies are designed to go without food for long periods of time. However, it is much more important to know for whom intermittent fasting is not suitable.

People for whom intermittent fasting is not suitable:

  • children and young people
  • Individuals with malnutrition and malnutrition
  • Individuals with amenorrhea (absence of menstruation)
  • people with low blood pressure
  • people with chronic diseases
  • people with cancer
woman doing sports

Intermittent fasting is suitable for anyone who is physically fit. With previous illnesses, the method should first be discussed with a doctor (Image source: Irina L / Pixabay).

How long do you intermittent fast?

The difference to other forms of dieting is that intermittent fasting is a form of nutrition. That means you can practice this form over a longer period of time.

If a suitable form of fasting (2 days, 5:2, dinner-cancelling, etc.) has been found, it can even be used for a lifetime. It is best to start intermittent fasting slowly at first and then increase it from week to week.

When and how does intermittent fasting work?

Initially, weight loss may seem very high as the liver's stores of sugar begin to run out. However, the initial weight loss is just water (7). However, if intermittent fasting is practiced for a longer period of time, then the body burns more visceral belly fat (8).

After about 12 - 14 hours, the process of autophagy begins in the body. Cleansing, healing and regeneration processes take place. Our body begins to recycle itself. This burns visceral fat. This also quickly ensures a flat stomach - which maintains motivation and discipline.

How healthy is intermittent fasting?

So far, based on the available data and analyzes of the studies, there has been talk of a positive effect on health (9). Due to the different forms of intermittent fasting and the variable study population, there are not enough clinical study results.

In addition to the positive effect on health, intermittent fasting has the same effect on weight loss. The forms of fasting seem to have a positive effect on the low reduction in fat-free mass in particular. Negative side effects have not yet been scientifically proven.

2 teas next to each other

Along with water, herbal teas are healthy liquids to consume while intermittent fasting (Image source: congerdesign/Pixabay).

What can I eat and drink while intermittent fasting?

Even if there are no strict regulations about what to eat and drink, a healthy diet is essential. The table therefore lists all healthy and unhealthy foods and liquids for the fasting period. These guarantee a successful intermittent fasting.

Eat unsuitable food Drink Improper drinking
hummus Meat Water, tap water, thin vegetable broth alcohol
Lentils, Vegetable Food unhealthy fats Herbal Tea, Ginger Tea, Black Tea, Green Tea, White Tea, Rooibos Tea, Chamomile Tea, Black Coffee (in moderation) sweetened teas
nuts, berries, papaya Sugar non-caloric drinks, diet cola calorie drinks


Intermittent fasting is not a form of dieting, it is a form of nutrition. It is not primarily the diet that is changed, but much more the period in which food is eaten.

Intermittent fasting forms typically include periods of eating and fasting. If e.g. If, for example, the 5:2 variant is chosen, then two days of the week are fasted and five days are eaten normally.

Some studies show the positive effects of intermittent fasting on health, weight loss and appetite suppression. This form of nutrition is currently in vogue and, in contrast to other forms, can be practiced for a lifetime.


  1. German Society for Nutrition (2018): Therapeutic fasting, base fasting, interval fasting - an overview. In: DGEinfo, 2018 (2).
  2. Harvie, M. & Howell, T. (2014): The 2-Day Diet: Reduce 2 Days, Eat Normal for 5 Days - Lose Weight Guaranteed. Munich: Goldmann Verlag.
  3. Mosley M & Spencer M (2015) The FastDiet - Revised & Updated: Lose Weight, Stay Healthy, and Live Longer with the Simple Secret of Intermittent Fasting. New York City, USA: Simon and Schuster.
  4. Varady, KA (2011): Intermittent versus daily calorie restriction: which diet regimen is more effective for weight loss? In: Obes Rev 12.
  5. Wirth, S., Ott, J., Renezeder, K., Eppel, W., Huber, JC & Frigo, P. (2009): The influence of dinner canceling on nocturnal hypothermia. In: Obstetrics and Gynecology.
  6. Ravussin E, Beyl RA, Poggiogalle E, Hsia DS & Peterson CM (2019): Early Time-Restricted Feeding Reduces Appetite and Increases Fat Oxidation But Does Not Affect Energy Expenditure in Humans. In: Obesity, 27.
  7. Brunnabend, A. (2020): E. v. Hirschhausen: Consultation hours: Tips for intermittent fasting - this is how you keep going!
  8. Schübel R, Nattenmüller J, Sookthai D, Nonnenmacher T, Graf ME, Riedl L, Schlett CL, von Stackelberg O, Johnson T, Nabers D, Kirsten , R., Kratz, M., Kauczor, HU., Ulrich, CU, Kaaks, R. & Kühn, T. (2018): Effects of intermittent and continuous calorie restriction on body weight and metabolism over 50 wk: a randomized controlled trial. In: The American Journal of Clinical Nutrition, 108 (5).
  9. Stocker, R., Reber, E., Aeberhard, C., Bally, L., Schütz, P. & Stanga, Z. (2019): Fasting - effects on body and psyche. In: Praxis, 108 (9).
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