top of page

What happens in the body during fasting? Autophagy, Intermittent Fasting & Fasting Metabolism

Autophagy, Intermittent Fasting & Fasting Metabolism - explained simply and briefly

bunte Zellen

Our body is a small masterpiece and works within itself like a fine Swiss clockwork. But what happens while we are not eating? Why do we not starve?

(Why we don't starve while fasting - I'll explain another time ;-))

First of all, a short explanation about our metabolism:

Metabolism is understood as all biochemical reactions taking place in the body.

It performs organism functions, breaks down substances and maintains body substances.

Metabolic processes include:

  • Breathing -> oxygen supply

  • Supply of nutrients

  • Utilization & production of waste products incl. their excretion

In catabolism the metabolic product is used for energy production and in anabolism it is used for energy consumption and building up of body substances.

What is autophagy?

Autophagy quite simply translated is your body's recycling system.

It represents the cell cleansing process during a food break.

It can be compared to a garbage disposal or a cleaning crew, which collects and recycles the cell garbage in your body. This means that your cells are freed from tired or sick cellular waste.

However, the process of autophagy occurs only after a certain time without food.

Cell cleansing takes place from about 12-14 hours.

Intermittent overnight fasting can help achieve autophagy. This means that if you have an early dinner or a late breakfast (only if you are a late breakfast person), you can easily reach the cell cleansing phase thanks to the sleeping time.

Fasting metabolism

We start the fasting period according to the Buchinger method with glaubern. By emptying the gastrointestinal tract, our body registers that something is happening and changes from energy program 1 - nutrition from the outside - to program 2 - nutrition from the inside. Our body jumps from our normal metabolism to the fasting metabolism.

Energy production takes place during fasting through glucose. Our body always needs an appropriate concentration of glucose to maintain our vital functions. Glucose is relevant for our brain, nerve cells, kidney marrow and red blood cells, among others.

During our fasting days, the following things happen in the fasting metabolism - explained very simply and briefly:

1) During the first 24 hours, glycogen stores are emptied from the liver and muscles.

2) From about the 2nd day, the excess proteins are converted to glucose (=energy for us) by glyconeogenesis.

3) And after that (from about day 3) the fats from your fat depots are converted:

- Glycerol into glucose

- Fatty acids into ketone bodies

This way our body feeds itself and we have enough energy for all our activities and our brain enough food to function even during fasting.

A quick side fact:

Just because excess protein is broken down, we don't lose muscle mass in fasting! Only from fasting day 20-30 would protein breakdown and loss of muscle mass occur. But such a long fasting should be done only in a fasting clinic and with medical guidance. Also, it is not necessary to fast so long, a fasting period of 5-10 days is perfectly sufficient.

However, we only enter the fasting metabolism during "real" fasting. During intermittent fasting, autophagy comes into effect, but we do not enter fasting metabolism.

Intermittent fasting

Intermittent fasting is a nice way to give our body some rest. Autophagy, the cell cleansing process, kicks in after just 12-14 hours. So if we calculate an early dinner and bedtime, this can already provide enough hours to easily do something good for our body.

The important thing is that the interval phase without food must fit you, your body and into your daily routine. Longer food breaks are also stress for our body and therefore not suitable for everyone. Especially women with hormonal problems should be careful.

Food breaks are good for your body

Give your body breaks - food breaks - and it will thank you! Try small intervals of 13-15 hours and see how you feel. Or dare to do a small fasting period of 5-8 days - but make sure you have good relief days before and even better build-up days after; or let me accompany you:

Recent Posts

See All


bottom of page