Different Stages Of Intermittent Fasting That You Must Know

Different Stages Of Intermittent Fasting That You Must Know


Intermittent fasting is the talk of the town. As people find it more doable and more beneficial, they are embracing this age old technique with the whole heart. 

Intermittent Fasting has been a part of Indian culture since many centuries. 

Vedic or spiritual fasting has been mentioned in the “Karma Kanda” in one of the vedas called Yajurveda. 

It says that if we give more space in between meals to our body, it digests the meal properly giving way to better metabolism. 

Ramadan is a type of intermittent fasting that is followed by muslims globally every year during the month of Ramadan. It includes changes from normal eating patterns to nocturnal eating.

Worldwide different religions follow fasting methods in different seasons of the year.

Here is a brief understanding about what are the different methods and what happens during different stages of Intermittent Fasting.

Methods of Intermittent fasting


The 8 / 16 Method : 

This method is quite popular as it involves 8 hours of feeding window and 16 hours of fasting. 

The 6 / 18 Method:

Once you are an expert and have experience of fasting, you can take on the 6 hours of eating window and 18 hours of fasting.

The 4 /20 Method:

This is an advanced method of fasting where you have 4 hours of eating window and 20 hours of fasting.

When the body goes through extended hours of fasting, it has some benefits like reduction of insulin levels, depletion of glycogen levels and fat burn. 

Let us take a look at different stages of intermittent fasting.

What are the different stages of Intermittent Fasting?


Feeding Stage (0-4 hours)


Feeding stage is the time just after you have had your meal.

If you have stopped eating your food by around 6 pm in the evening, then the feeding stage starts right afterwards. 

This first stage lasts for 4 hours after you have stopped eating. After a good meal, a lot of glucose is available to the body during this phase.

Body uses this exogenous glucose for functioning. 

Postabsorptive Stage ( 4-16 hours)


When the food has been ingested, digested, absorbed and stored, the body is in a postabsorptive stage.

If you sleep at 9 pm after having your food by 6 pm. At around 9 am in the morning, your body is already in the postabsorptive stage. 

In this stage,  the body relies on energy that it has absorbed from the food. 

Gluconeogenesis ( 16-30 hours) 


The main function of Gluconeogenesis is to produce glucose from non carbohydrate sources such as Amino Acids or Glycerols etc.

This stage starts after you have completed 16 hours of fasting and lasts upto 30 hours. 

It is said that after more than 14 hours of starvation, 54% glucose comes from Gluconeogenesis and the contribution increases to 64% at around 22 hours.

 It goes up to 84% after 42 hours of fasting.

During this time autophagy kicks in wherein the body activates the intracellular recycling system. When fasting starves the cells, autophagy helps to digest some cell components providing necessary energy for survival. 

It is important to note that the concept of Autophagy has received The Nobel prize in 2016.

Ketosis  ( 30-48  hours) 


After several hours of fasting, the body slips into the stage of intermittent fasting called Ketosis. It is often when the body does not have enough carbohydrate to burn to get enough energy.

It starts burning fats already available and starts making Ketones which can be used as fuel. 

Protein Conservation ( >48 hours)


In this stage a high level of growth hormone starts maintaining muscle mass or lean tissue. 

The energy requirement for metabolism is entirely fulfilled by the use of Ketones. This stage occurs after 48 hours of fasting. This type of fasting should only be performed by people who are familiar to the practice of intermittent fasting. 


Commonly asked questions


What is the fat burning stage of fasting?


The third stage of fasting, Gluconeogenesis, is called the fat burning stage. This occurs approximately 16 hours after eating. It is said that the fat burning stage will be maximum during the fourth stage, Ketosis. Keto diet pattern has originated from the work Ketosis. 


How long does it take for intermittent fasting to work?


Intermittent fasting is a lifestyle change and it is better not to expect quick results.You can notice significant changes in your body in about 10 days after your first fast. The body clock will reset in a day or two after you start fasting. 


How much weight can you lose in a month with intermittent fasting? 


Depending on what is your intake and given that it does not exceed your daily caloric requirement, one might lose upto 3 kgs with intermittent fasting when coupled with appropriate exercise. 


What are the anabolic stages of fasting?


When the body is in the fed stage, it is in the anabolic stage. This is a stage that lasts upto 4-5 hours after eating. In the anabolic state, insulin levels are high and the body draws energy from ingested carbohydrates.


What are the catabolic stages of fasting?


Catabolic state of fasting occurs 8-12 hours after eating. Blood sugar levels start lowering and the body starts reaching for alternate sources of energy i.e fat.


What is the best way to break a fast after intermittent fasting?


It is always better to break the fast with a fruit or dry fruit. Eating normally during your feeding window is necessary when you are doing intermittent fasting. Large meals often lead to bloating and feeling tired. It is always better to resume normal food eating patterns.


What are the different apps to map the stages of Intermittent Fasting?


There are many apps which help track different phases of fasting namely

  • Zero app
  • Fastic App
  • Window
  • Fastient
  • InFasting




Intermittent fasting is a lifestyle change with many benefits along with setting your bodily systems right. It helps reset circadian rhythm and aids weight loss. 





Snehal Joshi

Snehal is a Certified Nutrition Coach by National Academy of Sports Medicine. She is writing about her persuits of Nutrition Science since last 4 years.

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