What Are the 5 Stages of Fasting?

October 1, 2021


Fasting is the practice of abstaining from food and drinks for a period of time. Fasting basically boosts our metabolism, reduces inflammation, improves cognitive function, and improves overall health.

It also forces cells to engage in activities that aren't normally activated when a constant food supply is available. When fasting, the cells must rely on some other materials and processes to generate energy because the body is unable to obtain glucose as it normally does.

Consequently, the body starts the natural method of creating its own glucose, gluconeogenesis. The liver is the one that does the process of turning non-carbohydrate products such as fats, amino, and lactic acids into glucose energy. Since fasting causes our bodies to conserve resources, the basal metabolic rate improves, resulting in lower blood pressure and heart rate.  

Fasting is a practiced way to lose weight. It is a part of various religious practices as well. How long to see weight loss results with intermittent fasting – while you can experience some weight loss in as little as a week, significant weight loss will take around 10 weeks. Read the review to gain more information on the benefits of each fasting stage and choose the length of the fast which is best for you.

What Are the 5 Stages of Fasting?

It's not like all fasts have the same advantages. There are several fasting stages, whereas the advantages of fasting vary depending on how long you fast. The five major stages of fasting are the following:  

  • Stage 1 – Ketosis
  • Stage 2 – Autophagy
  • Stage 3 – Growth hormone
  • Stage 4 – Insulin reduction
  • Stage 5 – Immune cell rejuvenation

Stage 1: Ketosis

16–18 hours after starting a fast, the metabolic condition of ketosis occurs as the body starts to break down and burn fat. Ketone bodies form as a result of this condition. Once the body can't access glucose, brain cells, heart cells, and skeletal muscle cells use ketone bodies as an alternative energy source.

Ketone bodies, or simply ketones, are substances produced by the liver during gluconeogenesis, a process that creates glucose in times of fasting. It’s an alternative source of energy. The brain uses them as a major energy source during periods of fasting where glucose is not available.

Since ketones reduce appetite, your appetite will start to decline throughout the fasting period. Also, this stage is a great option if you're looking to slim down. Your body goes into a fat-burning phase, and because you haven't eaten anything in a long time, you rapidly start to burn off body fat.

Stage 2: Autophagy

The body enters the repair phase after a whole day of fasting. It starts repurposing old and damaged cells while also reducing inflammation. This is the ideal stage if you want anti-aging or anti-inflammatory effects. Your cells become more functional when your body is under moderate stress.

One of the things they do is trigger autophagy. During autophagy, the cells examine all of their internal components, replacing everything old, damaged, or not working properly with shiny new models. The old components will either be recycled or discarded. When referring to how long to fast for autophagy, it is recommended only twice a month.

Stage 3: Growth hormone

Following any type of fasting is not very beneficial as it causes a sturdy biological push, and hunger center and appetite hormones go into overdrive. This is a reaction that occurs when the body is deprived of food.

Humans always tend to reward themselves for any hard work they have done. For instance, after finishing the fasting period or after physical activity, they usually want to spoil themselves with various unhealthy foods and drinks on non-fasting days.

Stage 4: Insulin reduction

Even though fasting leads to lower insulin levels, it does not mean that it is 100% beneficial. For example, the insulin levels in the body reach their lowest point 54 hours after you start fasting.

It is considered a positive thing because it can reduce inflammation, improve insulin sensitivity, and reduce insulin resistance. However, lowering blood sugar levels can cause some negative effects, such as excessive thirst and hunger.

Stage 5: Immune cell rejuvenation

The body breaks down old immune cells and regenerates new ones 72 hours after starting a fast. In many cell populations, prolonged fasting lowers circulating insulin-like growth factor 1 (IGF-1) levels and protein kinase A (PKA) activity.


Fasting over longer periods of time can cause some unpleasant side effects, so it is not recommended if the primary purpose is losing weight. Some of the negative effects include headaches, constipation, crankiness, and lethargy. Fasting can cause the individual to overeat, which will end in low body energy and stomach problems. 

What Is the Fat-Burning Stage of Fasting?

Fat burning is actually a fasting stage that starts after 14–16 hours of fasting and increases between 16–24 hours of fasting. In this stage, you'll produce and use ketone bodies for energy since glycogen will be reduced. Fat cells in the body produce free fatty acids as a result of fat breakdown. PPAR-alpha (a liver fat metabolism regulator) is programmed, which ensures that those fatty acids are used during ketogenesis.

How Long Does It Take to Go Into Fasting Mode? 

Entering into fasting mode will take many hours after your last meal. The time varies from person to person, but 12 hours is a common estimate.

The fasting app enables you to track your progress as well as your fasting time. Time tracking is of great importance, especially because the data that you collect will assist you in ensuring that you are not putting your body in a dangerous position. The five stages of fasting can assist people in reducing the number of calories they eat.

Intermittent fasting is an effective way to boost your fitness. It's cheap, easy to do, and relatively safe for the majority of people. Each stage is distinct in terms of the body's primary source of energy and how it influences the metabolism and hormone levels. You determine the duration of your fast based on your health objectives.


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