Intermittent fasting - an overview
More and more often we come across the terms interval fasting, intermittent fasting or IF for short in the media. Eating not according to calories, but according to the clock. What is intermittent fasting, how does it work and who should rather not do it?
What is Intermittent Fasting?
The linguistic origin of the dietary form also known as intermittent fasting is Latin: intermittere means to interrupt or suspend. Intermittent fasting alternates between normal food intake and fasting in a constant rhythm. In contrast to a therapeutic fasting cure, intermittent fasting is to be applied on a long-term basis.
How does Intermittent Fasting work?
The meal breaks in intermittent fasting have a dual function: on the one hand, no calories are consumed, and on the other hand, hormone balance is positively influenced to better access fat reserves. Especially in combination with exercise, intermittent fasting improves insulin sensitivity. Overweight people in particular benefit from this, because they often have insulin resistance. When the cells respond to insulin secretion again, the blood sugar level settles at a normal level, the secretion of insulin is reduced and fat burning is stimulated. In addition, the release of the body's own growth hormone HGH is increased by intermittent fasting, which supports the burning of fat and the building of muscle mass.
The doctor Petra Bracht does not call intermittent fasting a diet, but a "daily clean-up". She explains: "After about twelve to 14 hours of fasting, the process of autophagy begins in the body. Cleansing, healing and regeneration processes take place, the body begins to recycle and burns visceral fat cells." [1]
Different methods
Intermittent fasting can be carried out according to different concepts, whereby fasting is carried out either by the hour or by the day.
Method 16:8
With this concept, you divide the day into a 16-hour fasting period and an 8-hour eating period. Depending on your preferences or your daily routine, you forgo breakfast or dinner. For example, you can start your day at 8am with a hearty breakfast, have a hot meal at noon and a third meal in the afternoon. Your fasting time begins at 4 pm. During this time you are only allowed to have calorie-free drinks. Or have your first meal at noon and start fasting after dinner.
Method 5:2
With this concept, the fasting period takes place on a daily basis: Two days a week you eat a maximum of a quarter of your normal calorie intake, i.e. about 500 to 800 kilocalories. On the other five days you can eat whatever you want. You can schedule the fasting days however you like, either directly after each other or spread out over the week. Fixed days, for example Tuesdays and Thursdays, make it easier for you to stick to it.
Method Eat-Stop-Eat
One or two days a week you fast for 24 hours, the other days you can eat whatever you want. Between the maximum of two fasting days per week, there should be at least two days of eating. The advantage of this form of fasting is that you can eat every day if you plan your fasting times carefully. For example, if you start a 24-hour fast after breakfast, you can start eating again the next day with a late breakfast.
Before the start
Before you start, you should consider which method suits your habits best in the long term. Do you prefer to fast by the hour or by the day? Are you better off skipping breakfast or dinner? Which days of the week are best for fasting?
Meal times
During meal times you can eat what you want and how much you want. However, if your goal is to lose weight, you should eat moderately and healthily and take breaks of several hours between meals. Foods rich in fibre and protein will keep you full for a long time and help you to get through the fasting period. Especially at the last meal before fasting, you should really eat your fill.
Fasting times
During the fasting periods, only calorie-free drinks are allowed, such as water, tea, black coffee or even a thin broth. For a little variety, the water may be flavoured with a slice of lemon or orange or some lemon juice. Sugary drinks and alcohol are not allowed.
The situation is different with the 5:2 method: here, about a quarter of the usual energy intake is allowed during the two fasting days, i.e. about 500 to 800 kilocalories. Meals should be composed of lots of vegetables, whole grain products and protein-rich foods and should avoid quickly digestible carbohydrates such as white bread, pasta or sugar.
Between meals
Several hours between meals give the body time to break down fat. Without carbohydrates, the blood sugar level remains low and prevents a renewed release of insulin. On the other hand, even a small biscuit raises your blood sugar level again, the body releases insulin and stops the breakdown of fat.
Possible side effects
It is a great advantage of Intermittent Fasting that normal food is eaten during the meal period and the body is sufficiently supplied with vitamins and minerals. Therefore, no drastic side effects are to be expected.
At the beginning of intermittent fasting you may feel tired and fatigued, but this often disappears after a short period of adjustment. If the diet is extremely one-sided and unhealthy, nausea, headaches and bad breath may occur.
Effects on the body
After 14 hours of fasting, autophagy starts in our cells. In this process, also known as cell cleansing, cells break down and utilise their own components. Outdated and defective building material is digested, the body cleanses itself of old burdens. This vital process is stimulated by fasting.
Other effects of intermittent fasting, such as the inhibition of inflammatory processes, the reduction of cholesterol levels, the lowering of blood pressure, the prevention of various diseases and a higher life expectancy have so far only been proven by studies on laboratory animals. These are not readily transferable to humans.
Who is Intermittent Fasting not suitable for?
Intermittent fasting is good for most people; after a usually short period of acclimatisation, they feel fit and healthy. However, those who suffer from pre-existing conditions such as low blood pressure, metabolic disorders, chronic diseases or cancer should definitely consult their doctor beforehand. Intermittent fasting is not suitable during pregnancy and breastfeeding, in cases of eating disorders or underweight.
Unlike most other diets, intermittent fasting only temporarily deprives the body of calories. It does not adapt to the deficiency and the basal metabolic rate remains high. If you stop interval fasting and don't feast, you have a good chance of maintaining your weight.
Basically, there is no time limit. However, there are natural limits to weight loss. You should also make sure that your body is always sufficiently supplied with nutrients. Especially if you want to lose a lot of weight, you should start under professional guidance.
As a beginner to intermittent fasting, the fasting period may seem interminable and your stomach may growl. A warm cup of tea or a hot shower will often help, but sometimes a walk is enough to distract you.
Exercise can be used to support any diet, including Intermittent Fasting. During the first few days you should take your training slowly, as you may not be as fit as you are used to. And make sure you eat your main meal after training.
Basically, the times can be shifted. However, it is easier to keep the phases relatively constant as the body adapts to the rhythm and you can also plan better. However, with the 16:8 method, many people adjust the eating window to the changed rhythm at the weekend.
Conclusion
During interval fasting, a constant rhythm is alternated between normal food intake and fasting. Depending on the method, the fasting period is several hours daily or several days weekly. Chronically ill people should talk to their doctor before interval fasting. Intermittent fasting is not suitable for pregnant and breastfeeding women or people suffering from an eating disorder.
