Status: 17.04.2024 13:40 | from North German Broadcasting logo

Lose weight and maintain your weight – intermittent fasting is supposed to make this easier. Longer breaks are taken between meals. How do the 16:8, 5:2 and 1:1 methods differ, and who are they suitable for?

Intermittent fasting is the most important new trend in nutritional medicine. According to research results to date, the method can help people lose weight healthily and maintain their body weight. Apparently, interval fasting can even protect against diabetes (type 2). The effects of diet on health and the aging process are currently the subject of many studies. In Reviews have found many positive metabolic effects of short-term fasting as well as good tolerability.

Is intermittent fasting deadly?

In March 2024, a discussion about negative effects arose: According to a A study from Shanghai based on US health data found that intermittent fasting almost doubles the risk of dying from cardiovascular disease. However, the study that made the headlines did not actually look at planned intermittent fasting: it included data from people who ate their meals within less than eight hours on two randomly selected days, for whatever reason – shift work, previous illness or other. This study therefore has little significance with regard to the question of how intermittent fasting affects health or the risk of death. There are no long-term studies among people on intermittent fasting as part of a conscious diet.

Be careful with pre-existing conditions

Although intermittent fasting has been proven to be beneficial for many people, some people should still exercise caution. It is important to consult your doctor before starting.

  • low blood pressure
  • Metabolic diseases
  • chronic diseases
  • Cancer
  • old age.

Intermittent fasting is generally not suitable:

  • during pregnancy and breastfeeding
  • for eating disorders such as anorexia, bulimia, binge eating
  • underweight
  • for migraines.

What methods are there for intermittent fasting?

Fasting means abstaining from certain foods, drinks and stimulants, either for a short or longer period of time. With interval fasting, you can choose between different variants:

  • 16:8-Method: There are 16 hours between the last meal of the previous day and the first meal of the day. Two meals are eaten in the eight hours in which you are allowed to eat.
  • 5:2-Method: Eat normally on five days a week and very little on two days.
  • 1:1-Method: (Alternating fasting or alternate day fasting): With this method, you eat normally one day and then only consume about 25 percent of your usual amount of energy the next day. This way, you alternate between “normal” days and fasting days.

Further information

Nutrition doctor Dr. Matthias Riedl. © NDR Photo: Moritz Schwarz

36 mins

You asked, the nutritionist answers! Dr. Matthias Riedl answers questions from the nutritionist community about interval fasting, oat diets, losing weight, pre- and probiotics and healthy oils. 36 min

Why short-term fasting is so effective

Clock with 24-hour division and the inscription "Lent" - "Mealtime". © NDR
Do not eat anything for 16 hours and only eat two meals within eight hours: Intermittent fasting gives the body plenty of time to burn fat.

Since the Stone Age, the human metabolism has been set up for fasting phases. When there was plenty, our ancestors ate without restraint, but in times of scarcity, the stomach remained empty for several hours or days. The human body survives long periods of hunger by storing energy reserves in various organs and tissues and mobilizing them again when needed. However, it also reduces energy consumption – and after a few days begins to break down protein in the muscles.

The crucial difference between intermittent fasting and longer fasting regimes or crash diets: the metabolism is not slowed down and muscle mass is not broken down. This is very important because it avoids the dreaded yo-yo effect.

Fasting also leads to beneficial biochemical changes in the body, such as improved sugar and fat metabolism: substances are released that can reduce inflammation.

Studies: Positive effect on body weight

Scientific Studies on mice have shown that animals that only eat during a certain time window stay slim and live longer than their counterparts who have access to food around the clock – and that with the same number of calories. One explanation: a break from eating for at least 14 hours sets off a kind of cleaning process in our cells, known as autophagy. Damaged cell parts are covered by a membrane and digested. This recycling program makes aged cells fully functional again and could even slow down the aging process.

Fasting according to the 5:2 method

A popular form of intermittent fasting is the 5:2 diet: on five days a week you can eat as usual without counting calories. On two days, food intake is reduced to 500 to 800 calories for women and 600 to 850 calories for men. You should also drink plenty of calorie-free drinks. Quickly digestible carbohydrates such as white bread, pasta, potatoes and sugar should be avoided completely on fasting days. This way the body learns to live off its reserves. The 5:2 method is about as effective as a permanent calorie reduction as a weight loss aid, but is easier to maintain.

Further information

Two bowls of Hawaiian curry soup decorated with lemongrass. © NDR Photo: Claudia Timmann

Three dishes can be combined from these low-calorie recipes for a relief day. more

A plate of tomato-zucchini scrambled eggs is on a table. © NDR Photo: Claudia Timmann

How does 5:2 fasting work and what can a day with 800 kcal look like? Information and recipe recommendations at a glance. Download (84 KB)

Fasting according to the 16:8 method

If you don’t want to fast for whole days, you can incorporate longer meal breaks into your daily routine. With the 16:8 method, you skip either the morning or evening meal, so you go without food for 16 hours straight. For example, if you don’t eat anything after 5 p.m., you can eat breakfast again at 9 a.m. the next morning. This means your metabolism goes into a short fast every night. Even if you eat large portions at the two remaining meals, you automatically eat less than you would in three (or more) meals – overall, your calorie intake is reduced by an average of five to ten percent.

The potential to lose weight with this method has been scientifically proven. It can also help against diseases associated with obesity such as high blood pressure or type 2 diabetes. Another pleasant side effect: the body has less to do with digestion at night, which benefits the quality of sleep. If you can’t go 16 hours without food, you should start with 12 or 14 hours and then increase the nightly fasting break by 30-60 minutes per week. This way, the body gradually gets used to the rhythm.

VIDEO: Doc Andresen and Dr. Julia Fischer: How do I fast properly? (30 min)

Fasting according to the 1:1 method

The 1:1 diet – also known as alternating fasting, alternate day fasting or every other day fasting (EODF) – involves fasting every other day. This is a small challenge for the body. Anyone who wants to try it should always consult a doctor beforehand. With alternating fasting, it is also particularly important to ensure a balanced diet in order to provide the body with all the important nutrients.

What can you drink during intermittent fasting?

You can and should drink while fasting – but only calorie-free drinks such as water, thin vegetable broth, unsweetened tea or black coffee in moderation.

How many hours break between meals?

With all short-term fasting variants, it is important not to eat more often or significantly more than usual during the food intake phases. You should take breaks of at least four to five hours between meals. Because if you eat carbohydrates in between meals – whether biscuits, crispbread, fruit juice or milk – the body converts them into sugar. And this goes straight into the blood: the blood sugar level rises, the body releases insulin and stops the fat breakdown. The rapid insulin peak in the blood can lead to mild, short-term hypoglycemia and to cravings.

Intermittent fasting: The most important things at a glance

  • Avoid physical exertion while fasting until you have completely gotten used to the new rhythm.
  • Continue eating normally, no double portions.
  • To get and stay full, make sure you eat enough vegetables (fiber) and protein sources (dairy products, eggs, fish, meat, legumes, mushrooms or nuts) at every meal.
  • No snacks between meals! Drinks that contain calories, such as milky coffee or juice, are also snacks.
  • Calorie-free drinks such as water or unsweetened tea help to bridge hunger pangs during the meal-free period.
  • After your first meal, take a short walk or do a little exercise to aid digestion.

Experts on the topic

Recipes for relief days without milk and wheat

Fasting recipes without milk and wheat

Further information

A clock next to a healthy breakfast. © COLOURBOX Photo: azgek

Intermittent fasting can promote the self-cleaning of cells, strengthen the immune system and help with diseases such as fatty liver. more

A plate with clear broth next to carrots and chives. © picture-alliance/dpa/Stockfood Photo: FoodPhotography Eising

Longer periods of fasting help with weight loss or cell cleansing, but can also have undesirable effects. more

A glass of ginger tea stands on a wooden table, next to it is fresh ginger and a lemon. © Fotolia.com Photo: juefraphoto

Detoxify the body and find inner balance: For many, Lent is an opportunity to consciously abstain. more

A white plate with a fork, knife and an alarm clock © colourbox

6 mins

Intermittent fasting is an effective way to lose weight and maintain your weight. How do the 16:8, 5:2 and 1:1 methods differ? 6 Min

A weekly plan with two fasting days. © NDR Photo: Moritz Schwarz/Oliver Zydek

13 mins

Atrial fibrillation – at just 38 years old: Now restaurateur and singer Nicolas N. wants to do something about his high blood pressure. 13 min

This topic in the program:

NDR Television | The Nutrition Docs | 11.03.2024 21:00

NDR-Logo