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What Are The Stages Of Intermittent Fasting

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How You Feel: Less Hungry And More Energetic

5 Stages of Intermittent Fasting | Jason Fung

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 dont 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.

Fasting Stage #: Protein Conservation

The fifth stage of fasting is the protein conservation phase. After about a week of fasting, the body meets its energy needs almost exclusively from fat reserves.

While minimal amounts of protein are needed for gluconeogenesis, the brain has also switched predominantly to fat energy consumption .

In this stage of fasting, hunger has genuinely disappeared. Consequently, ghrelin, the hunger hormone, is also at a low.

For this reason, the world record for fasting is 382 days, as the body is now feeding only on its body fat .

Contrary to popular belief, muscles do not atrophy at all during prolonged periods of fasting.

In the phase of protein conservation, the release of growth hormones is already enormously high. As a result, it protects muscle and bone mass from degeneration during fasting .

Hence, this fasting stage lives up to its name.

The human growth hormone stimulates muscle growth and repair .

For this reason, intermittent fasting is no stranger to bodybuilders. Occasionally not eating for long periods can help build muscle instead of breaking it down.

Fasting, for example, can also speed up the healing process of wounds and more severe injuries .

Since growth hormones are so effective, their use in competitions is even considered doping.

How Does Intermittent Fasting Work

There are several different ways to do intermittent fasting, but they are all based on choosing regular time periods to eat and fast. For instance, you might try eating only during an eight-hour period each day and fast for the remainder. Or you might choose to eat only one meal a day two days a week. There are many different intermittent fasting schedules.

Mattson says that after hours without food, the body exhausts its sugar stores and starts burning fat. He refers to this as metabolic switching.

Intermittent fasting contrasts with the normal eating pattern for most Americans, who eat throughout their waking hours, Mattson says. If someone is eating three meals a day, plus snacks, and theyre not exercising, then every time they eat, theyre running on those calories and not burning their fat stores.

Intermittent fasting works by prolonging the period when your body has burned through the calories consumed during your last meal and begins burning fat.

Read Also: What Foods Can You Eat When You Are Intermittent Fasting

Stage Two: Early Fasting State

Once your body is finished with the digestive process, about 3-4 hours after eating, your body transitions into the early fasting state, which approximately lasts until 16 to 18-hours after eating.

During this state, your body:

  • Your blood sugar and insulin levels begin to decrease.
  • Begins to convert the stored glycogen into glucose to use as energy.
  • Searches for alternative sources of fuel, from fat cells, once it uses up the glycogen stores. This is where the burning fat for fuel reference comes from.
  • Your body also converts amino acids, the building blocks of proteins, into energy.

During this state, your body converts glycogen, amino acids, and fatty acids received from the foods you ate earlier and converts them into energy for fuel as needed.

Of course, the better you fuel your body, the more efficient it can be at this conversion process.

This is one of the most important and beneficial stages for the average person who would like to experience the benefits of intermittent fasting without major disrupting in lifestyle.

Some of the benefits that happen during this stage include building and repairing cells, increase of basal metabolic state, hormone regulation, and more.

Stages Of Fasting Summary

Intermittent Fasting: The Complete Guide You Need

Heres a quick summary about the stages of fasting:

  • Fed State : insulin levels increase and the body starts storing excess glucose as glycogen.
  • Postabsorptive Stage : insulin starts dropping and your body breaks down glycogen into glucose for energy.
  • Gluconeogenic Stage : glycogen stores have been depleted, consequently, your body makes glucose from the break down of amino acids.
  • Ketogenic Stage : your body starts entering ketosis, a state where fatty acids and ketones meet most of your energy needs. At this point, the break down of amino acids starts decreasing.
  • Protein Conservation Stage : the body releases high amounts of human growth hormone and norepinephrine to maintain lean tissue and muscle mass.

If you loved this article about the stages of fasting, what happens when you fast and are ready to start your weight loss journey, the Custom Keto Diet plan is the place to start!

This plan helps men and women lose fat without starving themselves or giving up their favorite foods.

Don’t Miss: How Do You Lose Weight With Intermittent Fasting

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 bodys natural defenses use fat stores to store toxic metals and other toxins so they cant 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.

Clinical Studies Of Cr

Intermittent fasting is known to mimic the effects of caloric restriction. Clinical research of CR includes two landmark, twenty-year studies of monkeys, one by the University of Wisconsin, the other by the National Institute on Aging. Each study attempted to establish a link between longevity and caloric restriction. The Wisconsin study showed a positive effect on health and survival, whereas the NIH study showed no significant impact on life span. However, there was a reduction in age-related conditions, such as cancer, heart disease, and diabetes.

If a reduction in age-related disease is not sufficient motivation for intermittent fasting and CR, perhaps the photo below will provide additional inspiration. The monkey on the left followed a CR regimen while the one on the right was fed a normal diet at regular intervals.

Research now proves that intermittent fasting not only mimics the effects of calorie restriction but seems to confer additional health benefits, to a greater extent, than can be attributed to CR alone.

Also Check: Does Prayer And Fasting Really Work

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 its metabolized for energy. This process promotes a healthy heart, and for some, improves cholesterol levels by boosting HDL levels.

Stage Three: 24 Hours

Stages of Fasting TIMELINE + BENEFITS! (Intermittent Fasting to Extended Fasting)

After about 24 hours of fasting, your body starts to do something really interesting: repair itself. This is a process called autophagy, which is when your cells start to get rid of any components that are old, damaged, or functioning poorly.

Autophagy is incredibly important for your health and has been shown to reduce inflammation, kill cancer cells, and clear out the misfolded proteins that are thought to cause Alzheimers. As autophagy declines naturally with age, its thought that fasting-induced autophagy can be a way to reduce the effects of aging. And, indeed, studies have shown that fasting is connected to living a longer life.

Target these Stage Three benefits with ADF , Eat-Stop-Eat fasting, or 5:2 fasting. Read a comparison.

Recommended Reading: What Kind Of Fasting Is There

Fasting And The Keto Diet

You can also combine fasting with a ketogenic diet.

Several of the benefits of intermittent fasting come from your body being in ketosis a state in which you burn fat as your main energy source.

By eating a ketogenic diet, you can get your body into ketosis before you start fasting. A keto diet suppresses hunger and improves your health on its own. Pairing it with fasting provides even more health benefits.

You can start a keto diet today with a quick trip to the grocery store.

Intermittent Fasting Can Help Weight Loss

IF makes intuitive sense. The food we eat is broken down by enzymes in our gut and eventually ends up as molecules in our bloodstream. Carbohydrates, particularly sugars and refined grains , are quickly broken down into sugar, which our cells use for energy. If our cells dont use it all, we store it in our fat cells as, well, fat. But sugar can only enter our cells with insulin, a hormone made in the pancreas. Insulin brings sugar into the fat cells and keeps it there.

Between meals, as long as we dont snack, our insulin levels will go down and our fat cells can then release their stored sugar, to be used as energy. We lose weight if we let our insulin levels go down. The entire idea of IF is to allow the insulin levels to go down far enough and for long enough that we burn off our fat.

Also Check: Can Intermittent Fasting Help With Weight Loss

Health Information You Can Trust

We pride ourselves on being your source for the best, scientifically-accurate advice for healthy living.

This article contains references to scientific journals and peer-reviewed research. The numbers in brackets correspond with the list of references at the end of the article.

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Additionally, the Reviewed and Approved seal signifies that our scientific board of experts has double-checked this article for accuracy. You can feel confident in knowing that the information within this article is sound.


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.

The stages of fasting outlined below are based off 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.

The Stages of Fasting- In-depth Interview with Dr. Goldhamer & Dr. Group

Length: 93 minutes

The Stages Of Fasting: An Overview

Intermittent Fasting and Time Restricted Feeding Benefit ...

In this section, youll find a short summary of each fasting stage, along with some basic definitions that will help you understand the rest of the article.

Ive divided fasting into five stages .

  • Stage 0: Eating
  • Stage 3: Ketosis
  • Stage 4: Rejuvenation
  • Stage 5: Rebuilding

Stage 1 starts as soon as you finish eating.

First, it takes a few hours to digest your food. Then it takes another 12-24 hours to use up the glucose stored in your liver. Stored glucose is known as glycogen.

If youre not familiar with how glycogen works, this short video explains the basics:

Stage 2 starts when you run out of liver glycogen, and your body starts switching over to use fat as your primary energy source.

How does your body know to start burning fat?

Because the hormone called insulin goes down.

Insulin goes up whenever you eat, and its main job is to store energy, including body fat. But when insulin goes down, that process reverses and you burn more body fat.

Heres a summary image that well revisit later:

In Stage 3 , youve transitioned to full fat-burning mode, and your liver is turning some of the fat into ketones.

Ketones are the alternative energy source your brain uses when you fast, or when you eat a very low carb diet.

After youve been fasting for a few days or so, some special rejuvenating processes start happening in your body. Thats stage 4, and well get into the specifics later on.

For the full story, read on.

Don’t Miss: What Is Considered Intermittent Fasting

Stages Of Intermittent Fasting: Whats Going On In Your Body

The stages of Intermittent Fasting describe the metabolic state your body goes through during the fasting and eating intervals.

Intermittent Fasting is perhaps best defined as a nutritional strategy, aimed at weight loss. The characteristics are the periods of fasting and feeding. It is not a diet, as we are used to, but finding an ideal time to eat. This puts your body through different metabolic states.

For several years, nutritionists were against this method because it posed several risks to the human body. Not everyone can use this strategy freely, ideally under the supervision of an expert.

However, with experience over time, they now realize that the benefits are remarkable and that it is worth implementing this nutritional plan. The metabolic impact of food alternation is obvious and beneficial if we know and make the most of each of its stages.

Watch this great explanation video about How Intermittent Fasting Affects Your Body and Brain

Weight Loss And Fat Loss

Eating during a set period can help people reduce the number of calories that they consume. It may also help boost metabolism.

  • neurodegenerative diseases

However, the research in this area remains limited.

A 2014 review reports that intermittent fasting shows promise as an alternative to traditional calorie restriction for type 2 diabetes risk reduction and weight loss in people who have overweight or obesity.

The researchers caution, however, that more research is necessary before they can reach reliable conclusions.

A 2018 study indicates that in addition to weight loss, an 8-hour eating window may help reduce blood pressure in adults with obesity.

Other studies report that intermittent fasting reduces fasting glucose by 36% in those with prediabetes, although it has no effect on healthy individuals. It may also decrease fasting insulin by 1157% after 3 to 24 weeks of intermittent fasting.

Time-restricted fasting, such as the 16:8 method, may also protect learning and memory and slow down diseases that affect the brain.

A 2017 annual review notes that animal research has indicated that this form of fasting reduces the risk of nonalcoholic fatty liver disease and cancer.

Read Also: What Food Can I Eat During Intermittent Fasting

Recommended Foods And Tips

While the 16:8 intermittent fasting plan does not specify which foods to eat and avoid, it is beneficial to focus on healthful eating and to limit or avoid junk foods. The consumption of too much unhealthful food may cause weight gain and contribute to disease.

A balanced diet focuses primarily on:

  • fruits and vegetables, which can be fresh, frozen, or canned
  • whole grains, including quinoa, brown rice, oats, and barley
  • lean protein sources, such as poultry, fish, beans, lentils, tofu, nuts, seeds, low fat cottage cheese, and eggs
  • healthful fats from fatty fish, olives, olive oil, coconuts, avocados, nuts, and seeds

Fruits, vegetables, and whole grains are high in fiber, so they can help keep a person feeling full and satisfied. Healthful fats and proteins can also contribute to satiety.

Beverages can play a role in satiety for those following the 16:8 intermittent fasting diet. Drinking water regularly throughout the day can help reduce calorie intake because people often mistake thirst for hunger.

The 16:8 diet plan permits the consumption of calorie-free drinks such as water and unsweetened tea and coffee during the 16-hour fasting window. It is important to consume fluids regularly to avoid dehydration.

Stages Of Fasting In The First 72

The 5 stages of Intermittent Fasting

With the recent skyrocketing popularity of intermittent fasting, the word fasting has stopped being associated exclusively with religion and protest and taken on a connection with an impressive list of health benefits including improved mood, increased energy, sharper focus, and even clearer skin.

So its no surprise that you might be curious about trying out fasting for yourself. But like the intelligent person you are, you first want to find out as much as you can about what fasting will do to your body and how itll make you feel.

Because knowledge is power, here is a detailed description of what happens during extended fasts, including the stages of fasting, what you can expect during them, and why.

Recommended Reading: How To Do Intermittent Fasting For Fat Loss

Intermittent Fasting: Surprising Update

Theres a ton of incredibly promising intermittent fasting research done on fat rats. They lose weight, their blood pressure, cholesterol, and blood sugars improve but theyre rats. Studies in humans, almost across the board, have shown that IF is safe and effective, but really no more effective than any other diet. In addition, many people find it difficult to fast.

But a growing body of research suggests that the timing of the fast is key, and can make IF a more realistic, sustainable, and effective approach for weight loss, as well as for diabetes prevention.

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