Understanding the Stages of Intermittent Fasting

Intermittent fasting is a simple concept, yet the more you read about it, the more it seems like there is more to it than just fasting and eating during certain windows.

Each fasting “stage” is responsible for sending different sends signals to your body. To keep things simple, I will break it down by hours after you eat your last meal.

In today’s post, I want to explain what the stages of intermittent fasting are and how each works with your body so you can achieve your health goals!

First, you should consult a licensed medical physician before you jump into intermittent fasting. IF isn’t for everyone, and therefore, it’s something to discuss with a licensed professional. 

The purpose of this post is to give you a simplified version of the stages of intermittent fasting so you can better understand how it works, not to provide any professional/medical advice.

What are the Stages of Intermittent Fasting 

When you abstain from eating foods for 12, 14, or 16 and up to 24 hours during your fasting period, your body naturally moves through the different stages as it shifts from the fed-fast cycle. These stages send a variety of signals to your metabolism and hormone levels.

You probably already know that women’s bodies can be a bit more complex, often due to hormonal cycles we naturally experience throughout the month. As you can imagine, understanding the stages of intermittent fasting can be very beneficial for achieving your goals.

If you’re new to Intermittent Fasting and are looking for a comprehensive how-to eBook specifically written for women, check out the Intermittent Fasting eBook for Women here.

Stage One: Fed State (0-4 hours after eating)

Here’s how Intermittent Fasting works. The first stage in intermittent fasting is referred to as the “fed” stage. In this stage, your body focuses on digesting the last meal eaten and absorbing all the nutrients from food.

At this point, your body doesn’t “know” you’re intermittent fasting. It’s doing what it normally does after eating.

During this state, your body:

• Absorbs nutrients from the foods you ate in your previous meal; this is why the quality of foods matter during intermittent fasting.
• Increases blood sugar levels and releases insulin (based on the types of foods consumed).
• Extra glucose (sugar) is stored in the liver and in your muscles as glycogen (stored carbohydrates). 
• Your body reserves this glycogen for a future source of energy. 
• Hormones shift, including ghrelin, the hunger-stimulating hormone, which increases after you eat, and leptin, the appetite-suppressing hormone (these two work together).

Stage Two: Early Fasting State (4-16 hours after last meal)

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 (sugar) 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.

If you’re experiencing energy dips during intermittent fasting and are wondering what can you eat or drink while intermittent fasting, check out this post.

Stage Three: Glucogenesis & Fasting State (16-30 hours)

Complicated word but simple to explain: in this stage your body shifts from using sugar for energy to fat for fuel.

Once your body realizes “no more food is on the way,” it fully enters a fasting state that can last between 18 hours to 2 days. 

In this state your body:

• Begins to make ketone bodies, a compound your body makes when it begins to turn fat into fuel.
• Your body begins to transition into ketosis, where it uses fat for fuel.

This is the state that many who follow a ketogenic diet and incorporate intermittent fasting seek, where their bodies go into “ketosis,” a state in which your body converts fat into fuel.

It is not necessary to practice keto while intermittent fasting. You can read this post: How to Practice Intermittent Fasting without Keto to learn more.

Stage Four: Starvation State (Long-term fasting)

Approximately after 48 hours of fasting, your body begins to enter a long-term fasting state.

During this period, insulin levels decrease, ketone levels increase, and protein breakdown is reduced to conserve muscle.

It is not recommended to go into long-term fasting without medical supervision. 

Specifically, if you’re a female, you can disrupt your body’s natural hormone processes and metabolic states like slow down your metabolism, thyroid disruption, mood swings, sleep cycles, and more. 

If you want to practice intermittent fasting safely and want a step-by-step guide to begin, I’ve got the thing for you.