Here’s What Happens When You Fast

Fasting Stage 1 | Fasting Stage 2 | Fasting Stage 3 | Fasting Stage 4 | Fasting Stage 5

Our body is like a machine, but a very complex one. And each individual has a unique combination of factors that affect their tendencies and responses to the same things. And so, when it comes to fasting, everyone responds a little differently.

How your body responds to fasting depends on how healthy you are, the genes you’ve inherited, your lifestyle, etc. But in general, there is an algorithm that every healthy metabolism moves through when poked and prodded by the fasting environment.

Let’s take a look at the timeline of predictable events – stages of fasting – as you slip into a routine of fasting from hours to days.

Fasting Stage 1 | The Fed State: 0 to 3 hours

This is the fasting stage when your body is still digesting food and absorbing nutrients. Glucose enters your bloodstream from the carbs that your body breaks down during this stage. Your pancreas will produce more insulin to move glucose into the cells, where they can be used for generating energy. Glucose is also used to synthesize proteins in your muscles.

After 3 hours of having your meal, the insulin and glucose in your bloodstream should return to your normal levels. This period of 0 to 3 hours into your fasting journey is called the anabolic phase.

During this time, your body has access to nutrients to burn, build muscle, or store. However, based on what you’ve eaten, your body can remain in a fed state for hours.

Fasting Stage 2 | The Post-Absorptive State/ Pre-Fasting Stage: 4 to 18 Hours

If your body has gone without eating for over four hours, it can go into a pre-fasting stage. At the end of this stage, the glycogen stores run out. Your body breaks down amino acids (proteins) and triglycerides (or fats).

Though it is great for weight-loss goals, your body also loses muscle and then fat. That is not what you want. Hence, it’s important to alternate between fed and early-fasting states, so you give your body a store of glycogen to burn continually. The 16:8 intermittent fasting route is the most common fasting routine that helps you lose weight the right way.

Fasting Stage 3 | The Fasting Stage: up to 2 Days

At this stage of fasting, your glycogen stores are depleted in this stage, and your body utilizes proteins and fats for energy.  In the hours that follow glycogen burning, your body produces ketones. Ketones are chemicals that your liver makes, converting fats for fuel. Here your body enters a state of ketosis.

These ketones become your body’s primary fuel at this point. But your brain can’t do without glucose altogether. There’s none in your blood, and your glycogen stores are all used up. What does your body do for glucose at this point? It turns to other making glucose, not from carbs but ketones, fats, and amino acids. It is the process of gluconeogenesis. In other words, the body can make sugar out of anything.

During gluconeogenesis, your body produces about 80 grams of glucose a day. That is just about what your brain needs to function. The rest of your body doesn’t need glucose when ketone bodies are available.

Decreased apatite, fatigue, weight loss, fruity-smelling breath, and a high level of ketone bodies in your body are some of the signs of ketosis.

What’s up with Ghrelin?

Let’s look at what the hunger hormone is going through now. Ghrelin plays several roles in digestion, including that of hunger manager. Deep into your fast, ghrelin starts to recede, and it tends to come and go in cycles. But overall, levels fall as you fast, which is why you feel less hungry three days into your fast.

You can not achieve ketosis with shorter windows of fasting. You need to follow 24 hours and more fasting with a zero-carb diet to enter ketosis.

Fasting Stage 4 | Prolonged Fasting Stage: Days 2 to 5

This happens; as you enter deeper into your stages of intermittent fasting, you’re not so hungry anymore. It is also known as the starvation stage.

Your insulin and glucose levels stay low, and you’re in ketosis. This promotes growth hormone secretion. Ghrelin, the hunger hormone, also increases the growth hormone secretion. Studies have revealed that growth hormone helps to preserve lean muscle mass and prevents fat accumulation.

Growth hormone and insulin fall in the bloodstream improves your immunity, longevity, neurogenesis, and metabolic health and reduces inflammation.

Fasting Stage 5 | Steady Ketosis: After 5 days of Fasting

As you enter into your fifth day of not eating, you’re in a steady state of ketosis, with significant drops in insulin and glucose. After 10 days, your body will be in growth hormone deficiency mode. People with growth hormone deficiencies tend to have lower diabetes, cancer, and overall mortality.

On the flip side, your beta-hydroxybutyrate (BHB) levels, a type of ketone body, will keep rising and eventually plateau at around 5 to 6 mm in 20 to 25 days of fasting. Your body doesn’t receive the signal to stop producing ketones and plateau with low insulin levels.

There is a risk of ketoacidosis, which is usually seen in people with diabetes, alcoholics, and the starving. You can smell the ketones in the breath of such individuals. To prevent this, if you’re planning to fast long term, you should consult a doctor before you do.

Final Thoughts

That wraps up the stages of fasting, which is a much-studied area with plenty of information around. If you want to enjoy the benefits of fasting, you have to research to understand your body’s needs and make an informed decision.

However, this is a general timeline. As we’ve said before, everyone responds slightly differently to fasting. It’s always a good idea to work with your physician and figure out the best way of fasting that you can adopt into your lifestyle for better health.

Fasting changes your basic concepts of food. You may feel eating 3 times a day is not essential, and the quality of your nutrients is more important than quantity. You learn to master your hunger and achieve a sense of serenity.

Do you feel ready to start your journey of fasting? Intermittent fasting is the safe and best way to start. You can sign up for a 21-day intermittent fasting challenge to experience the best health benefits. You will receive the fasting guide, daily tips, and meal plans, which will make this process easy for you. Click here to sign up.