Stages of Fasting: 5 Stages of Intermittent Fasting Made Simple

Stages of Fasting: 5 Stages of Intermittent Fasting Made Simple


When you fast, your body goes through different stages of fasting, that have specific effects on your body and overall health. Understanding these stages can help you make informed decisions about your fasting routine and its potential benefits.

Are you ready to navigate the stages of fasting like a pro? I’m here to walk you through each stage so that you can gain clarity with this detailed, step by step guide, and make the best decision for your unique body and situation.

Key Takeaways

  • Fasting is a process of not eating for a set time. Your body changes during fasting, using stored fat and fixing cell damage.
  • Fasting has various benefits, including weight loss, improved insulin sensitivity, enhanced growth hormone levels, autophagy, and immune system support.
  • There are five stages of fasting: fed state (0-3 hours), early fasting stage (3-18 hours), fasting state (18-48 hours), long-term fasting state (over 48 hours), and finally the breaking your fast stage.
  • During each stage, different things happen in your body. From using food as energy to burning fats, healing old cells to fighting diseases – it’s like hitting the reset button on your body.
  • Always take care while exercising on an empty stomach and know how to safely break your fast. Listen to what your body needs!

Table of Contents

Understanding Fasting

Fasting is not eating for a set time. People have fasted for thousands of years. It’s part of many religions and ways of life. Today, doctors study fasting to see how it helps our health.

There are different kinds of fasting. Some people engage in periods of not consuming food. This practice is referred to as intermittent fasting. Your body changes when you fast. In the first stage, your body uses up food from your last meal. Later stages kick in as hours pass without more food coming in.

In each stage, certain things happen in your body, like using stored fat for energy or fixing cell damage.

With some practice and care, anyone can get good at fasting and enjoy its perks—like less belly fat and better blood sugar levels! I’ll guide you through these steps so that you know what happens during each stage of fasting!

The Process of Fasting – Ketosis, Autophagy, And Other Health Benefits

This wonderful journey of fasting isn’t as complicated as it seems; let’s break down the process starting from when you eat, known as the ‘fed state’, which lasts up to three hours.

Then we transition into ‘early fasting’ mode, a period that stretches between 3 to 18 hours without food intake. The next step is what we call ‘fasting state’ where your body goes into serious fat-burning mode for about 18 to 48 hours.

Lastly, beyond these two days (48+hours), we enter an impressive stage called the long-term fasting state – here’s where amazing biological transformations take place!

glass of child water with lemon close-up

Herbal teas and infused water can provide hydration without breaking your fast.

Fed State (0-3 Hours)

In the fed state, your body uses food as energy. This state lasts from zero to three hours after eating. Your blood sugar level goes up during this time. To keep a balance, your body sends out insulin.

Insulin is key in this process. It helps control how much sugar is in your blood and keeps it all stable. The body prefers to use carbs (like bread or potatoes) for energy at this point of time because they’re simple to break down into glucose, which is a kind of sugar that gives you fuel.

Ghrelin and leptin play major roles too! These hormones work together to tell you when you are hungry or full.

Early Fasting State (3-18 Hours)

In the early fasting state, your body starts working differently. From three to eighteen hours after you last ate, it looks for other sources of energy since food isn’t coming in. At this point, stored glycogen in the liver begins to get used up first.

Your body uses this stored sugar for fuel which leads to a drop in weight – but mostly it’s just water that you’re losing at this stage! More changes happen too. The hormones glucagon, epinephrine (adrenaline), growth hormone, and cortisol all jump into action during fasting.

The cool part is they help kick start fat burning since the easy-to-use glycogen stores are depleted.

Fasting State (18-48 Hours)

In this stage of fasting, your body starts using stored fats and proteins for energy. This process is known as ketosis. It means your body begins to lean on fat instead of sugar for its main power source.

Your cells also start a cleanup during this time. They take out the bad parts and put in new ones, also known as autophagy. It’s important not to rush into long-term fasting from here, without a doctor’s advice.

Long-term Fasting State (48+ Hours)

In a long-term fasting state, your body relies on saved fats for fuel. This starts after 48 hours of not eating. Your body gets into ketosis at this stage. Ketosis is when the body uses fat instead of sugar for energy.

Stored proteins also contribute to satisfy energy needs during this time span. Long-term fasting can help drop blood sugar levels, weight and blood pressure too. It may reduce belly fat and boost feelings of well-being as an added bonus.

However, it’s key to consume protein right after so you don’t lose muscle mass while fasting.

What Happens to Your Body During The Different Stages Of Fasting?

When you enter a fasting state, your body undergoes several changes to adapt to the absence of food. Insulin levels decrease, which allows your body to access stored fat for energy.

Additionally, growth hormone levels increase, promoting fat burning and muscle preservation. Your body also begins to regulate blood sugar levels more efficiently, reducing the risk of insulin resistance and type 2 diabetes.

As you enter a fasting state, your body goes through significant changes. During meal-time, your body is in cellular growth mode and after about 18 hours of fasting, it enters into ketosis.

This state activates the process known as autophagy which involves your cells breaking down and metabolizing broken proteins that build up inside cells over time. A longer fast may even prompt an increase in growth hormone and boost stem cell production – helping with immune function improvement.

It’s like hitting the reset button on your body.

Ketosis During Fasting

Ketosis is a key part of fasting. Your body begins to use stored fat for fuel when you fast for long periods. This happens most often after 16 hours without food. It’s why many people lose weight while fasting.

Active ketosis takes place between 18 and 36 hours of not eating. During this time, your body works hard to clean itself up. It gets rid of cells that are old or sickly in a tidy way known as autophagy.

This process helps keep us healthy as we age.

Autophagy And Growth Hormone Increase

During fasting, your body does a deep clean. It begins a process called autophagy after about 24 hours. This means it scrubs out old and damaged cells to make room for fresh ones. Besides, fasting helps hike up growth hormone levels in the body too! These hormones are vital as they keep muscle strong while cutting down fat tissue build-up.

So, fasting not only helps you feel light but also supports keeping your muscles solid and robust.

Stem Cells And Immune Function Improvement

Fasting for over two days is great for your body! It helps restart the immune system and pump up its work. That means fewer colds and flu, plus less swelling in your joints. Also, fasting gets more fresh cells ready to whip any viruses out of action.

You could say that fasting turns you into an ageless wonder woman with a younger feeling body! Not bad at all for a small break from food, right?

The Detailed Stages of Fasting Explained

In this segment, I’ll delve deep into the specifics of each fasting stage from the pre-fasting state to long-term fasting. We explore what goes on in your body during these times and major cues to note.

clock sitting atop a blue table

As you become more comfortable with fasting, gradually increase the duration of your fasting periods.

Stage 0 Or Pre-fasting State (0-8 Hours): Anabolic Growth Phase & Healing

In Stage 0 or the pre-fasting state, you experience an amazing growth phase. It’s a special part of fasting that starts as soon as you finish your last bite and lasts for about eight hours.

During this time, what you body does is use the nutrients from your last meal to get energy. Any left-over stuff it doesn’t need right away gets stored carefully as glycogen or fat.

This stage focuses on helping you grow and heal in many ways! What you ate during your last meal can even change how long this happens and how strong its effects are.

Stage 1 (8-12 Hours): Falling Blood Sugar Levels & Glycogen Stores

In Stage 1, usually around 8 to 12 hours after you eat, your body uses up all the food in your belly. Now it needs other ways to keep going. The sugar levels in your blood start to fall during this time.

This drop makes your body break down stored fuel and nutrients for energy instead of using meals you ate recently. This important change helps pave the way into the next stages of fasting where more significant health benefits are found.

Stage 2 (12-18 Hours): Partial To Full Ketosis & Fat Burning

In stage 2, your body starts to change. It begins between 12 and 18 hours into the fast. Your body moves from using sugar for power to using fat. This is known as ketosis or being “in ketosis”.

It’s a good thing because it helps you burn fat and lose weight.

This stage comes with some big helpers in the form of hormones. Glucagon, growth hormone, epinephrine, and cortisol step up to make sure everything goes smoothly. These hormones work together to help you burn off stored fat faster during this time.

Stage 3 (24-54 Hours): Autophagy, Growth Hormone, Reduced Insulin Levels

Stage 3 of fasting starts from hour 24 and runs up to 54 hours. This is a key time for your cells. At this point, they start to clean up and fix themselves – a process known as autophagy.

And there’s help on the way too! Your body ups its growth hormone levels now. These hormones patch up muscle wear-and-tear so things can run smoothly again.

Meanwhile, less insulin in your blood flows around because you’re not eating during fasting. That’s good news if you have diabetes or struggle with insulin resistance. With low insulin around, it gets easier for fat stored within your body to break down fully into energy – a state called ketosis.

These changes could make it simpler for you to maintain healthier body fats overall. Keeping an eye out here might just do the trick if high insulin levels or excess weight has ever given you sleepless nights before.

Stage 4 (72+ Hours): Stem Cells, Immune Function, Reduced Inflammation

In stage 4, lasting more than 72 hours, brilliant things happen to your body. Your stem cells start to wake up! These special cells can turn into any type of cell in the body. They help mend and rebuild worn-out tissue.

This is crucial for keeping you strong as you age. Plus, your immune system gets a big boost too! Fasting has the power to reset your immune cells and pump out new ones. Less inflammation and aging can be the result of this stage.

Exercising And Fasting State: What You Need To Know

Working out on an empty stomach can have benefits. It may help your body burn fat more soon. Also, it could help build muscle faster. It seems strange, but a well-timed fast can make exercise better.

Still, you must do it right and know what your body needs.

Taking care of yourself is key when fasting and working-out at the same time. Dehydration is a big risk, so drinking water is important! Listen to your body if you ever feel dizzy or weak during workouts while fasting.

If this happens too much, then stop fasting until things get back to normal for you personally.

How To Safely Break A Fast Or Extended Fast

slicing green vegetables on natural wood board, surrounded by ceramic plates with vegetables

When breaking your fast, choose nutrient-dense foods to nourish your body.

Breaking your fast in a safe way is important. Here are steps you can follow:

  1. Talk to a doctor first. Guidance from them is very helpful.
  2. Start slow. Going back to normal eating right away may not be good for your body.
  3. Begin with light meals. You could start with liquids like soup or juice.
  4. Increase the size and type of food slowly as time goes on.
  5. Take note of how you feel while eating.
  6. Stop eating if you feel sick or full too soon.
  7. High-sugar foods are not a good idea after fasting.
  8. Look for healthy foods like fruits, vegetables, and lean meats when you eat again.

When To Stop Fasting: Signs To Watch For

Fasting safely matters a lot. Watch for these signs to know when you need to stop fasting:

  1. You feel dizzy, weak or shaky: This could mean your blood sugar is too low. It’s time to eat.
  2. Your heartbeat is fast: A fast heart rate can be a sign that your body needs food now.
  3. You have a headache that will not go away: This might be due to low blood sugar.
  4. You can’t focus or think clearly: A lack of food can affect your brain function.
  5. You get too hungry: Hunger is normal at first, but if it gets worse, it’s time to eat.
  6. Your mood changes a lot: If you feel upset or on edge, this could be because your body needs food.
  7. You feel sick or unwell: Listen to what your body tells you.

Frequently Asked Questions About The 5 Stages Of Fasting

Let’s tackle some common questions about fasting, the different stages of intermittent fasting, and the benefit of fasting you are rewarded with. There’s so much more to discover – let’s dive into these questions together.

What Does A 72-hour Fast Do To Your Body?

A 72-hour fast changes your body in many ways. Your blood sugar, weight, and pressure go down. You may lose belly fat too. This long fast can make you feel better. The change starts when you stop eating.

First, your body uses stored glycogen for energy during the early fasting state (3-18 hours). This leads to water weight loss. Next, between 18 to 48 hours of not eating, ketosis starts happening in your body which means that it is using stored fats and proteins for energy instead of getting it from food.

Autophagy also happens within this period where damaged cells are cleaned out and replaced with new ones by your own system making you healthier inside out!

Do keep track not only of what changes happen but how they make you feel at every step so that next time you plan a fasting period, it follows what works best on your specific needs and preferences while optimizing its health benefits.

What Is The Ketosis Stage Of Fasting?

The ketosis stage of fasting kicks in after 18 to 36 hours. This is a time when your body burns stored fat for energy. You see, as you don’t eat, your body has to look within itself for fuel.

It starts with using up all the sugar on hand then it goes to the next best thing – fat.

This process makes things called ketones. Your body uses these instead of sugars for power. And good news, ladies, ketosis helps tackle hefty issues like obesity and heart disease which can peek around the corner as we age beautifully into our fifties and beyond! So if you fast more than 16 hours consecutively, you allow yourself a golden pass into this healthy zone.

How Long Do You Have To Fast To See Benefits?

To see the good things fasting can do, you have to fast for at least 16 hours. This length of time helps your body move into a state called ketosis. With ketosis, the body uses fat for energy instead of sugar.

You feel less hungry and think more clearly in this state. Other changes take longer to happen but they are worth waiting for! Long-term fasting drops your blood sugar, weight, and blood pressure over time.

It also cuts down belly fat and makes you feel better overall. Keep in mind that each person’s body is unique so effects may be slower or faster depending on different bodies.

How Does Fasting Affect Insulin Levels?

Insulin is a hormone responsible for regulating blood sugar levels. During fasting, insulin levels decrease, allowing the body to break down stored fat and use it as an energy source. Lower insulin levels also improve insulin sensitivity, making it easier for your cells to absorb glucose from the bloodstream. This can have long-term benefits for weight management and metabolic health.

What Happens To Your Blood Sugar Levels During Fasting?

During fasting, your blood sugar levels are tightly regulated by the body. As your glycogen stores become depleted, the liver produces glucose through a process called gluconeogenesis. This ensures that your brain and other vital organs have a steady supply of glucose, even in the absence of food. However, prolonged fasting or certain medical conditions can lead to a drop in blood sugar levels, which may require medical intervention.

How Does Fasting Affect Growth Hormone Levels?

Fasting triggers an increase in growth hormone levels, which can have several positive effects on the body. Growth hormone contributes to fat burning, muscle growth, and tissue repair. It also helps improve insulin sensitivity and supports the maintenance of lean muscle mass. Increased growth hormone levels during fasting can aid in weight loss and overall metabolic health.

What Are The Benefits Of Intermittent Fasting?

Intermittent fasting is a specific fasting method that involves alternating periods of eating and fasting. This approach offers numerous health benefits, including weight loss, improved cognitive function, reduced inflammation, and enhanced insulin sensitivity. Different types of intermittent fasting, such as the 16/8 method or eat-stop-eat fasting, allow for flexibility in choosing the fasting period that works best for your lifestyle.

How Long-term Fasting Benefits Your Body?

Long-term fasting, usually lasting more than 24 hours, can have profound effects on your body. Extended fasting promotes autophagy, allowing the body to remove damaged cells and stimulate cellular renewal. This improves immune function, reduces the risk of chronic diseases, and supports healthy aging. However, extended periods of fasting should be approached with caution and under proper guidance.

What Is The Recommended Fasting Period For Beginners?

For beginners, it is generally recommended to start with shorter fasting periods, such as 12 hours of fasting overnight. This allows your body to adapt gradually to fasting and can be easily incorporated into your daily routine. As you become more comfortable, you can gradually increase the fasting duration to reap more significant benefits.

little boy in large tie-dye shirt with water splashing all over him

Start with shorter fasting periods, such as overnight fasting for about 12 hours.

How Many Hours Of Fasting Are Required For Ketosis?

The exact number of hours required to enter ketosis may vary from person to person. Typically, it takes around 12 to 16 hours of fasting for your body to deplete glycogen stores and start producing ketones. However, it is important to note that individual response to fasting can differ, and factors such as metabolic rate and previous dietary habits can influence the time it takes to achieve ketosis.

When Should You Break Your Fast?

The decision of when to break your fast should be based on your individual needs and goals. It is generally advised to break your fast with a balanced meal consisting of protein, healthy fats, and carbohydrates. You can consider breaking your fast after the recommended fasting period for beginners, which is around 12 hours. However, it is essential to listen to your body and ensure that you consume a nutritious meal when you do decide to break your fast.

What Is The Best Way To Break A Prolonged Fast?

Breaking a prolonged fast should be done gradually and with caution. Start by introducing small amounts of easily digestible foods, such as fresh fruits or vegetables. Over the course of a few days, gradually increase your meal portions and include more complex foods, such as whole grains and lean proteins. This helps your digestive system readjust and prevents any discomfort or digestive issues.

How To Resume Eating After A Long Fasting Period?

After a long fasting period, it is important to ease back into a regular eating routine. Begin by consuming small, balanced meals at regular intervals throughout the day. Focus on nutrient-dense foods that provide a variety of essential vitamins and minerals. Pay attention to your body’s hunger and fullness cues and prioritize its needs during the refeeding phase.

What Are The Effects Of Breaking Your Fast Too Abruptly?

Breaking your fast too abruptly, especially after an extended period of fasting, can lead to digestive discomfort, bloating, and even electrolyte imbalances. It is important to reintroduce food gradually and choose nutrient-dense options to support your body’s nutritional needs. If you experience any adverse effects, it is advisable to consult with a healthcare professional.

What Are The Stages Of Fasting?

The stages of fasting are the different phases that your body goes through when you are not consuming any food. There are five stages of fasting, each with its own unique effects on your body.

How Long Does It Take To Enter The Fasting State?

The fasting state begins after approximately 12 hours of not eating. During this stage, your body starts to use stored glucose as an energy source instead of the glucose from your last meal.

What Happens To Your Body During The Early Fasting State?

In the early fasting state, which typically occurs after 16 hours of fasting, your body starts to break down stored glycogen to release glucose for energy. This helps to maintain your blood sugar levels and keep your body functioning properly.

When Does Ketosis Occur During Fasting?

Ketosis occurs during the later stages of fasting, usually around 24-48 hours after your last meal. During ketosis, your body switches from using glucose as its primary energy source to using stored fats, leading to increased fat burning and weight loss.

What Is Autophagy And When Does It Occur?

Autophagy is a natural process in which your body breaks down and recycles old, damaged cells. It occurs during extended periods of fasting, typically after 24 hours or more, and has numerous health benefits, including promoting cellular rejuvenation and reducing the risk of chronic diseases.

How Long Do You Have To Fast To Experience The Benefits Of Intermittent Fasting?

To experience the benefits of intermittent fasting, such as improved insulin sensitivity and weight loss, it is recommended to fast for at least 18-24 hours. However, shorter fasting periods can still have some positive effects on your health.

What Happens After 72 Hours Of Fasting?

After 72 hours of fasting, your body enters a prolonged fasting state, where it starts to conserve energy and reduce metabolic rate. This stage helps in preserving muscle mass and increases the production of growth hormone, which can have anti-aging and regenerative effects.

Can I Go On A Long Fasting Regimen Without Fasting For 72 Hours?

Yes, you can still benefit from intermittent fasting even if you don’t fast for 72 hours straight. Alternating between periods of fasting and eating can still have various positive effects on your health, such as improved blood sugar control and weight management.

How Can Fasting Help With Weight Loss?

Fasting helps with weight loss by promoting a calorie deficit and triggering fat burning mechanisms in your body. When you are in a fasting state, your body uses stored fat as an energy source, leading to a reduction in body weight and fat mass.

What Is The Effect Of Fasting On Insulin Levels?

Fasting can have a significant impact on insulin levels. During fasting, insulin levels decrease, which allows your body to use stored glucose and fat for energy. This can improve insulin sensitivity in the long term and help prevent insulin resistance and type 2 diabetes.

What Are The 5 Stages Of Fasting?

The five stages of fasting include 1) your body burning stored glucose, 2) breaking down fat for energy once glucose stores are out, 3) entering a metabolic state called ketosis, 4) starting a process called autophagy where cells clean up, and 5)  re-feeding when you break your fast.

What Happens To My Body During A Long-term Fast?

During long-term fasting over 24 hours, insulin levels fall and body starts using fats for fuel causing blood glucose levels to drop. This is when early signs of ketosis occur which means that your body starts burning fat instead of carbs.

Which Types Of Intermittent Fasting Can I Try?

There’s time-restricted feeding like doing 16 hours of not eating then having meals within an 8-hour window; alternate-day fasting where you eat normally one day but don’t eat on the next; and the Eat-Stop-Eat method might involve no food at all two days in a week.

Does Fasting Also Affect Our Immune System?

Yes! It has been found that even short term periods without food could trigger a strong response against diseases from immune cells inside us as they feed off old bits lying around.

What Benefits Does Exercising While Following Intermittent Fasting Provide?

Exercising during intermittent fast triggers increase in growth hormones contributing towards healthier muscle mass and reduction in excess body fat providing overall fitness boost

Are There Any Things To Look After While Ending My Fast?

It’s important how we break our fasts as unsuitable meal choices or large meal sizes right off can cause stomach cramps so start slow with simple foods rich in healthy carbs or proteins.


Fasting isn’t just about abstaining from food; it’s a journey that involves intricate phases, each with its unique impact on your health and well-being. As your guide, I’ve illuminated the path through each stage, shedding light on the science and benefits behind every step.

From the initial stages where your body transitions from utilizing food as energy to the profound effects of ketosis, autophagy, and growth hormone activation, you’ve gained insights into the remarkable processes that unfold within you.

The wisdom of knowing when to break your fast safely and the considerations for exercising while fasting have been unveiled, empowering you with knowledge to embark on your fasting journey with confidence.

woman stretching following video instructions on laptop

Listen to your body and pay close attention to your body’s cues and signals.

Remember, your body is a marvel, capable of embracing these fasting stages to reset, rejuvenate, and revitalize itself. As you journey through each stage, take heed of your body’s signals and listen to its needs.

Take this newfound understanding and let it guide you towards a healthier, more energized version of yourself.


About the Author

Leveraging her 40+ years in health & fitness as well as the latest biohacking and longevity breakthroughs, Peak Performance Coach, Biggi Fraley, helps you remain healthy, fit, and active so that you can age gracefully, stay independent, and embark on exciting new chapters in life.