What Happens in Intermittent Fasting?
Intermittent Fasting is suitable for some people to lose weight healthily. Unlike a diet or fasting cure, this form of nutrition can be used permanently. Because it is not about deprivation – during the eating phases, which usually consist of two larger meals, there are no restrictions or prohibitions on certain foods.
Digestion during Fasting
Our food passes through the mouth and oesophagus into the stomach when we eat something. There, it is broken down further. The food is then passed on to the small intestine—the pancreas and gallbladder direct digestive juices into the first part of the small intestine, the duodenum.
The digestive juices have the task of neutralizing stomach acid, and they also break down proteins, fats, and sugar. Our body’s nutritional components pass through the small intestinal mucosa into the blood and lymph.
The liver then absorbs the nutrient-rich blood. The organ, which is also responsible for producing protein and cleaning the blood, stores the sugar. The body can store this stored sugar, called glycogen, for a short period (the reserves last for around twelve to 24 hours).
Fat, however, can be stored for a long time. Because glycogen is available more quickly, the body prefers to get its energy from it and only resorts to body fat when the glycogen stores are empty. This is where intermittent Fasting comes in.
The different forms of Intermittent Fasting
Intermittent Fasting can be done in different ways.
- 5:2 method: With the 5:2 method, you consume a maximum of 500 to 600 calories twice weekly. On the other days, you usually eat.
- 16:8 method: With the popular 16:8 method, you eat in an eight-hour window and avoid solid food for the remaining 16 hours.
- 24-hour Fasting: A very extreme form of Fasting is the 24-hour fast. Here, you fast for a whole day. After that, you eat usually again.
- 18:6 Fasting: The 18:6 method is another form of intermittent fasting. Here, you fast for 18 hours and restrict all calories for the remaining 6 hours of the day.
This option is an advanced variation and is particularly suitable for people who have reached a weight loss plateau with the less restrictive fasting methods or who want to increase the benefits of their fasting for cellular health.
Fasting for 18 hours: What happens in the body
Immediately after eating a meal or snack, blood sugar levels rise. In a healthy person, the body then releases the hormone insulin, which paves the way for sugar (glucose) from the blood into the cells.
This causes blood sugar levels to return to normal within one to two hours after eating. However, in some people, blood sugar levels do not return to the level before the meal. Excess glucose is then stored as fat in the liver and muscles. In addition, long-term sugar spikes increase the risk of developing diabetes.
The calorie restriction and longer breaks from eating during intermittent fasting can help the body return blood sugar and insulin levels to normal. In addition, fasting initiates a process called autophagy. This term is derived from the Greek words “auto” for self and “phagein” for eating and refers to a process by which the body removes damaged cells from the body.
Typically, the body draws its energy from the food it is given. However, if denied, it resorts to the body’s energy reserves, such as the glucose stores in the muscles and liver. After 12 hours of fasting, these are also exhausted. The body then begins to burn stored fat. This process is called ketosis (a metabolic process that starts when the body runs out of glucose as an energy source).
At the same time, after about 14 to 18 hours, the body begins to break down damaged cell structures, also known as autophagy. This natural cleaning mechanism replaces broken cell parts with new ones, reducing oxidative stress and inflammation.
Possible Effects of Intermittent Fasting
Because this form of fasting is relatively new, few studies have examined the effects of intermittent fasting to date. More detailed research is needed to determine whether the positive health effects are caused by fasting or other factors such as a more conscious diet or lower weight.
Some studies on humans and animals have shown positive effects of intermittent Fasting on health. For example, in a human study, blood sugar levels, insulin resistance, and liver fat content improved when the test subjects with type 2 diabetes ate only 2 large meals daily instead of 6 small ones.
In mice at high risk for type 2 diabetes, intermittent Fasting reduced the presence of fat cells in the pancreas.
