What Are The Stages Of Fasting?

stages of fasting

Intermittent fasting is more than just a weight loss strategy. While skipping meals is a reliably good way to burn your fat stores, the health benefits of intermittent fasting go far beyond simple weight loss. Fasting can promote mental clarity and mood, improve immune function, increase muscle growth, and much more. However, not all fasting provides the same benefits. There are multiple stages of fasting, and the benefits you get from fasting depend on the length of your fast.

Below we look at the five main stages of fasting, the specific benefits of each, and a brief look at how to incorporate fasting into your life.

1. Fed State (812 hours): Stable blood sugar

The eating state occurs a few hours after you eat. Your body is digesting food and absorbing important nutrients. During this particular stage, blood sugar levels rise as your insulin levels are adjusting to the digestion of carbohydrates and glucose.

For most people, the eating state lasts 3-4 hours after eating. You leave this state only after your body has completely digested all of your food. Other hormones, such as leptin and gastrin, will slowly decrease to prevent you from feeling hungry again after a meal.

Some of the symptoms/signs of this stage include:

  • Lower hunger levels
  • Increased energy
  • Bloated stomach

You can also have a look at some benefits and tips:


  • Balanced blood sugar
  • Higher energy levels
  • Fewer hunger pangs
  • More nutrients in the body


  • You should focus on eating healthy foods that promote weight loss.
  • Make sure to drink water before and after meals to aid the digestive system.
  • Consume foods containing protein, dietary fiber, and unsaturated fat.
  • Document your calorie intake to ensure you’re not eating too much.

Stage 2 Fasting (12-18 Hours): Ketosis, Fat Burning, and Mental Clarity

After 16 to 18 hours of fasting, you should be in a state of full ketosis. Your liver begins to convert your stored fat into ketone bodies – the fuel bundle that provides energy for your muscles, heart and brain.

This stage of fasting has several benefits:

Appetite Suppression

Ketone bodies suppress appetite, which means your hunger should actually start to subside during this fasting stage.

Paradoxically, as you fast longer, fasting starts to become easier. After the first stage of fasting, appetite generally decreases.

Fat Loss

The second stage of fasting is ideal if you want to lose weight. Your body completely switches to fat burning mode and since you don’t have any food in your system, you start burning body fat rapidly.

In addition, this stage of fasting reduces gastrin, the hormone that makes you want to eat a lot of food, and also stabilizes your insulin levels, which prevents food cravings.

These factors work together to prevent overeating. If you can engage in intermittent fasting for 16-18 hours a day, you’ll burn body fat and fill up quickly when you break your fast, making it easy to maintain a calorie deficit and lose weight.

Mental Clarity

During this stage of the fast, you may also enjoy a boost in brain-derived neurotrophic factor (BDNF), a protein your brain makes to protect existing brain cells.

BDNF is a protein your brain makes to protect existing brain cells. bDNF also encourages the growth of new brain pathways. It also enhances learning ability and improves mood.

In animal studies, both fasting and ketosis increase BDNF, and researchers speculate that they do the same for humans (although there are no reliable human studies yet).

3. Fasting state (24 hours): Autophagy

The third stage is when the magic really begins.

A process called autophagy occurs when your body begins to replace abnormal cells that are not functioning properly. Autophagy is important for your health because it improves your brain, reduces acute inflammation, and decreases the risk of heart disease.

During this time, you will also enter ketosis – a metabolic state in which fat is the primary fuel source. All glycogen stores are now gone, so your body has no choice but to burn stubborn fat and produce ketone bodies to keep you functioning.

The fasted state can last from 18 to 48 hours. The longer you fast, the more likely you are to remain in ketosis longer. It’s worth noting that it’s not safe to fast intermittently for too long, so keep that in mind before trying to reap the health benefits.

With that said, let’s now look at the signs and symptoms:

  • Headaches
  • Short-term fatigue
  • Muscle cramps
  • Reduced appetite
  • Increased ketone bodies
  • Bad breath
  • Sleep changes

Here are the benefits of fasting and some tips:


  • Better cognitive performance
  • Noticeable weight loss
  • Reduced blood pressure
  • More lean muscle mass
  • Decreased stored fat
  • Prevents chronic diseases


  • Drink more water while fasting to prevent dehydration.
  • Have more rest time to avoid making fatigue worse.
  • Give yourself distractions so you don’t think about eating food.
  • Keep track of the fasting period to ensure you’re not doing too much.
  • Consume calorie-free supplements that boost your energy levels.

Stage 4 Fasting (36-48 hours): Growth Hormone and Recovery

In Stage 4, you leave the realm of intermittent fasting and enter a longer fast.

As you undertake a multi-day fast, your growth hormone levels begin to shift, which provides you with a new set of benefits.

Muscle Growth and Repair

A study of healthy adults found that a 48-hour fast increased human growth hormone (HGH) production by 400%. It also increased the frequency of growth hormone bursts throughout the day.

HGH increases muscle mass and stimulates faster muscle repair. It can also speed up the healing process of wounds and more serious injuries. hGH is so effective that taking it externally is banned in professional sports and considered a stimulant.

It may seem counterintuitive, but going without it for two days now and then may actually help you gain muscle rather than lose it.

5. The refeed: Recovery

The refeed state is basically a time for you to recover from your fast. You can break the fast with soft foods such as bone broth, eggs, soups and smoothies. Getting enough nutrients is important to fuel your body again and give it the energy it needs to stay awake.

Always eat nutritious foods that won’t be too taxing on your stomach. Fasting for too long can make your intestines especially sensitive during the digestion process. Instead, consume light foods designed to restore nutrients while jumpstarting the processes in your body again.

Here are some signs or symptoms that you may be in this stage:

  • Greater energy levels
  • Better concentration
  • Regular bowel movements
  • Less hunger pangs
  • Improved moods
  • Longer sleeping schedules

You can also look at some benefits and helpful tips:


  • Stronger muscle function
  • No more old immune cells in your body
  • You’ll be increasingly insulin sensitive
  • The body stores more healthy nutrients


  • Extend your eating window to allow for more recovery time.
  • Make sure to consume normal food again for a few days.
  • Eat smaller portions of food and gradually increase the serving size.
  • Drink more water to maintain hydration levels.
  • Avoid eating processed foods that will ruin your weight loss.


Now you know the important stages of intermittent fasting. You can understand what your body is going through and the process of losing weight. Just remember to follow the tips because you want to stay as healthy as possible while navigating a long fast.

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