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The Stages of Fasting:
What Happens To Your Body When You Fast?

Mary-Lou will be able to discuss this with you, assess your suggested pace, and guide, support and track your responses with you.


While fasting is nothing new, it is experiencing a resurgence in popularity as many discover its potential health benefits. If you are planning your first fast or looking for ways to improve your next one, there are a few things you should do to prepare. The first step is learning about the different stages of fasting. This knowledge helps you mentally and physically prepare for what happens to your body when you fast.

Summary of Benefits by the Stages

Benefits of Fasting Timeline (5 Day)


Intermittent fasting is one o the most powerful ways to reduce inflammation, boost immunity and enhance tissue healing. Here is a timeline I put together to show the physiological benefits of fasting.


4 - 8 hours: Blood sugar falls. All food has left the stomach. Insulin is no longer produced.


12 hours: Food consumed has been burned. The digestive system goes to sleep. Body begins healing process. Human Growth Hormone (HGH) begins to increase.


14 hours: Body has converted to using stored fat as energy/start producing ketones. HGH starts to increase dramatically.


16 hours: Body is ramping up fat burning. 


18 hours: Intermittent fasting from 16 to 18 hours has been shown to boost HGH levels by 50 - 100%.


24 hours: Autophagy begins! The body empties glycogen stores (a stored form of glucose, derived from carbohydrates, found in body tissue - predominantly in muscle tissue). Additionally, men,, who had fasted for 24 hours, had a 2000% increase in circulating HGH. Women who were tested had a 1 300% increase in HGH.


36 hours: Autophagy increases by 300%! Additionally, fasting up to 36 hours has been shown to boost Brain-Derived NeuroTrophic Factor (BDNF) levels by up to 400%. The shock of fasting leads the brain to create new cells! As neurons are coaxed to grow, the brain becomes more resistant to the effects of protein plaques that underlie cases of Alzheimer’s, or the damage inflicted by Parkinson’s.


48 hours (2 days): Immune system reset and regeneration. Increased reduction in inflammatory response. Autophagy increases 30% more. Rise in stem cells! - this is directly correlated with repairing immune system defect. DNA is reset (fasting turns off bad genes like obesity gene, allergy, etc). Microbiome is reset. Gastrointestinal tract is reset. 


72 hours (3 days): Ketones continue to rise. Hormones are optimised. The body raises up the stem cells and knocks down the overreaction of autoimmunity. Increased energy. Microbiome continues to reset. Note: You may start to feel colder than normal because as your hormone levels go down, your cells become more sensitive to the hormones. For example, fasting lowers T3 thyroid hormone to spare your muscle. So we feel cold! Although T3 lowers, the body is more sensitive to smaller amounts of hormones. It is able to utilise the hormones available.


96 hours (4 days): Continued autophagy and new stem cell growth. The continued drop in glucose and rise in ketones. Continued hormone optimisation. Increased levels of energy and better brain functioning. An overall sense of wellbeing. Decreased cravings, hunger, and irritability. Cortisol increases glucose. Some ways to combat this? Don’t over-train, increase your intentional prayer/meditation, or focus towards healing.


120 hours (5 days): Stem cell production in high gear today (on day 6 when you feed the stem cells the body will heal and create white blood cells!). Ketones may begin to drop, and glucose may slightly raise. Massive HGH rise (goes up every day, but the highest surge is on day 5), and puts you in a fat-burning mode for the next 36 hours to replace the glucose.

Benefits: Start Something New

With careful planning and thought, fasting can be an incredible springboard into a healthier lifestyle. One suggestion is to make plans before you even start your fast. Write down what you're hoping to get out of it and what you want to accomplish. If done correctly, the end of a fast is the perfect time to begin a dramatically healthier diet and lifestyle.


Additional Fasting Tips

Bowel movements and bad breath are two subjects that most people usually avoid discussing, but when fasting, you need to be aware of both.


During stages one and two of the fast, your body will still be expelling toxins and damaged cells every time you go to the bathroom. Using an intestinal cleansing product will help more thoroughly cleanse and detoxify your body.


Bad breath will be a concern throughout every stage of a fast. Slightly offensive breath is completely natural and part of the detoxing processes.


The stages of fasting:

The stages of fasting outlined below are based on a water fast, a traditional fast in which you abstain from any food and only drink water for 12-48 hours or longer. Personal experiences can vary depending on the type of fast, age, or health of the individual, but these should give you a general idea of what to expect when you fast.


Stage 1: Day 1-2

Stage one lasts for the first couple of days of the fast or about 12-48 hours from your last meal. Usually, it is a good idea to put some planning and preparation into how and when you will start a fast. Try selecting a start day and time and then make preparations in your schedule for the duration of your fast.


How You Feel: Hungry

This stage is when your body transitions into fasting mode and, for many people, it’s the most challenging part of their fast. This stage is where you start to feel the hunger pangs as you skip your regular mealtime routine. Most first time fasters start to feel a reduction in their energy levels. These effects can induce a negative mood or irritability for most fasters. It’s wise to prepare yourself for the possibility of being short on patience during this stage.


What’s Happening With Your Body: Battery Save Mode

Several things happen at the cellular level that cause hunger and fatigue during this first stage. When you’re eating regularly, your body breaks down glucose to get the energy it needs to function properly. While you’re fasting, your body needs to produce sugar for energy, so it begins a process called gluconeogenesis. During gluconeogenesis, your liver converts non-carbohydrate materials like lactate, amino acids, and fats into glucose. As your body goes into “battery save mode,” your basal metabolic rate, or BMR, becomes more efficient and uses less energy. This power-saving process includes lowering your heart rate and blood pressure. At this stage, you may feel drained. However, if you stick it out for a little longer, some of that lost energy will return


Benefits: Mental Strength and Heart Health

Fasting these first few days can be difficult, but there are mental and physical benefits. Mentally, the act of fasting is an excellent way to exercise your willpower. Similar to the strength runners might feel after pushing their body to run that extra mile, people who choose to fast can feel strength as they fight through those natural urges to eat. Physically, there are incredible cleansing and heart health benefits taking place, too. As BMR lowers, fat in the blood starts to disappear as it’s metabolized for energy. This process promotes a healthy heart, and for some, improves cholesterol levels by boosting HDL levels


Stage 2: Day 3-7

Stage two starts around the end of day two and lasts until day seven. A lot of changes begin to happen at this stage, and you may start to notice changes in your physical appearance, as well as how you feel.


How You Feel: Less Hungry and More Energetic

By stage two, ketosis has begun. Ketosis is a critical phase of the fast where your body starts to burn stored fat as its primary power source. As the processes of ketosis are carried out inside your body, you might stop feeling hungry and tired. The practice of putting your body into ketosis has a growing movement behind it. It is ideal for weight loss, balancing blood sugar, and more. Best of all, you don’t even have to fast to put your body into ketosis. Eating the right foods at the right time can be enough to start this fat burning process. There are even vegan ketogenic diet plans available so you can still eat health-promoting foods to stay in ketosis.


What’s Happening With Your Body: Fat Burning Mode

When you consume a typical diet of carbohydrate-rich foods, your body breaks down sugars and starches into glucose. Glucose is the primary source of energy for the body. However, when you fast or go into ketosis glucose becomes limited, and your body must turn to fat stores for the energy it requires. Your body breaks fat down into glycerol and fatty acids. The liver synthesizes ketones using glycerol. The glycerol is broken down by the liver for additional glucose, and finally, those ketones are used by your brain, as glucose becomes less available


Benefits: Weight Loss and Cleansing

Burning fat has several benefits for your health — the first being weight loss. Ketosis is a predictable way to target fat stores that otherwise remain untouched even with a healthy lifestyle. Additionally, getting rid of that extra fat has a detoxifying effect on the body. Your body’s natural defenses use fat stores to store toxic metals and other toxins so they can’t wreak havoc on your system. However, during ketosis, these toxic metals and toxins are safely expelled from your body as fat reserves get used up.

This cleansing effect may temporarily alter some people's complexion or cause other signs of a healing crisis.


Stage 3: Day 8-15

Stage three typically falls between day 8 and 15. This stage includes dramatic improvements in mood and mental clarity and is the stage seasoned fasters look forward to the most.


How You Feel: Clear Minded

By the third stage a sort of “fasting high” begins. This boost happens when your body fully adjusts to fasting. While not everyone reaches this stage, those who do, report a dramatic improvement in how they feel. These improvements include an elevated mood, increased energy levels, and a type of clear-mindedness unique to fasting.


What’s Happening With Your Body: Healing Mode

During stage three, your body starts to enter into a “healing mode.” This healing process begins as your digestive system takes a rest from the common stressors and toxins it endures on a daily basis. As a result, your body has fewer free radicals entering the mix, and oxidative stress decreases.

On the flip side, fasting causes a stress that provides an added benefit. This is a kind of mild stress that is comparable to the stress caused by exercise, which ultimately makes you stronger and your immune system more resilient


Benefits: Healthy Aging

  • When the cumulative effects of this stage add up, they can be the catalyst for significant health improvements. Anytime you limit free radicals and oxidative stress you are encouraging healthy aging and positioning yourself for fewer health complications. While less researched, this healing process seems to improve health for some.


Stage 4: Day 16 and Beyond

Stage 4 occurs sometime around day 16 and continues through the duration of your fast. While there may be some changes moving beyond this juncture, there is a daily balance that starts to set in.


How You Feel: Balanced

If you make it to stage four, you are at a place most have never gone. This stage, while doable, should only be attempted under close supervision from a trusted healthcare professional. For those that do make it this far, there are not any drastic shifts that occur in how you feel. Instead, a steady balance seems to set in.


What’s Happening With Your Body: Healing Mode Extended

Stage four is the extension and completion of the healing and cleansing processes that began during the earlier stages. The longer you fast, the more time and opportunity your body has to heal and cleanse itself.


Benefits: Personal Goals and Growth

If you make it this far, the benefit becomes personal. Fasting, especially beyond the first seven days, takes steadfast dedication. What you get out of the fast in these later stages can be a culmination of all the earlier stages or an accomplishment of a personal health goal. For some, it is weight loss, for others, it is a strategy to heal a particular health complication.


Stage 5: Breaking the Fast

Stage five may come sooner or later, depending on your fasting goal. While we don’t assign a specific target day, you may want to make breaking your fast a planned event you can look forward to and celebrate when it's all done.


How You Feel: Accomplished

Whether you fasted for half a day or a full month, you should feel accomplished. Taking deliberate action to improve your health or testing your limits is something worth celebrating.


What’s Happening With Your Body: Easing Out of Fasting Mode

How you choose to end your fast is critical. Depending on how long you fast, you may need to ease your way back into eating solid food. Fruit juices, cooked vegetables, and broths can help acclimate your body and digestive system to eating as internal mechanisms come back online.


This article has been slightly modified but is mostly sourced, with thanks, from  


Please click on the link above,  should you wish to see the references and additional links to support information. 

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