What Is Autophagy? Explaining The Bodily Processes Behind Fasting

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Among the many health benefits of fasting, aside from weight loss, perhaps the one that drives most people to try intermittent fasting diets is autophagy.

Autophagy is essentially the process of the cellular cleanup in which old and damaged cells and cellular components are removed and destroyed.

Fasting is thought to promote and increase the rate and extent of autophagy, which is thought to be part of the reason why intermittent fasting diets have been linked to decreased inflammation, decreased risk of certain diseases, improved brain function and health, and increased longevity.

But when does autophagy start when fasting? Is 16 hours fasting enough for autophagy? How can you increase this process with intermittent fasting?

In this article, we will explore how autophagy works, how long it takes it to really kick in when fasting, and how to boost this process through fasting.

We will cover: 

  • What Is Autophagy?
  • What Are the Benefits of Autophagy?
  • How Does Autophagy Work?
  • What Causes Autophagy?
  • How to Increase Autophagy

Let’s jump in!

An alarm clock on a plate.

What Is Autophagy?

Autophagy is the natural physiological cleanup process by which the body is able to break down and reuse old cellular components and decayed and damaged cellular matter.

It combines two Greek words—autos, which means “self” and phagomai, which means “eat.” Together, the term translates to mean “self-devouring.”

This natural cleanup process helps your cells operate more efficiently and can decrease inflammation and disease risk. For example, autophagy can remove damaged proteins and nucleic acids (DNA and RNA), which will allow the cell to function better and may prevent mutations or inflammatory reactions.

Besides just removing this cellular debris or “litter,” it is actually a recycling process. 

Rather than fully scrapping the damaged or old components, the body is able to recycle and make use of any salvageable components, repurposing or reusing them to reassemble new cellular components that are usable.

The components that are fully damaged, unnecessary, or too old are discarded and removed from the body.

It is likened to a quality control process in which the body actually takes an audit of viable versus damaged cellular components and removes the “junk“ from the cell that is hindering performance.

By removing and recycling these components, the cleanup process allows the cell to function more optimally, getting rid of aspects that are taking up space, slowing performance, and potentially increasing inflammation or causing other forms of dysfunction.

Cells showing autophagy.

What Are the Benefits of Autophagy?

Autophagy is a necessary cellular process, and without it, cells would not function properly and would be at an increased risk of damage and disease.

In fact, research has found that problems with performing this essential bodily process are linked to neurodegenerative diseases, certain cancers, liver problems, and decreased longevity. 

If you picture your kitchen as a giant cell with various appliances—such as the coffee maker, refrigerator, microwave, oven, and electric tea kettle—autophagy would be equated to fixing or replacing appliances as they break down.

For example, if your refrigerator stopped working, you not only lose the necessary functions that a refrigerator performs, such as keeping your food cold enough to prevent bacterial growth, but you will also have a large, useless appliance taking up space in your “cell.”

With autophagy, the broken refrigerator would be removed, any viable components would be saved and recycled, and the vacant space could then be used to accommodate a new refrigerator, restoring the proper functioning of not only the refrigerator itself but the kitchen as a “cell“ in its entirety.

If you didn’t remove the refrigerator and repair or replace it, your kitchen wouldn’t function as you need it to. Plus, you could get sick if you ate the food from the broken refrigerator.

In much the same way, autophagy is a vital cleanup process that ensures your cells function well and can thus decrease the risk of numerous diseases and disease states.

Autophagy begins to decrease as a person ages. This slowdown is thought to escalate the aging process and affect overall longevity. There can be a buildup of cellular junk components, which in turn, impedes the functioning of the cell and body as a whole.

A cell.

How Does Autophagy Work?

So, what exactly happens during this process?

Autophagy is facilitated by autophagy-related proteins (ATGs). These specialized proteins induce the formation of autophagosomes to form. 

Autophagosomes are structures that carry the damaged cell components to an organelle of the cell called a lysosome.

Like the mitochondria, which is another organelle, a lysosome is a specialized component in the cell. However, whereas the mitochondria help create usable energy called ATP, a lysosome digests or breaks down other broken or junk cell parts.

The lysosomes are the part of the cell that ultimately carries out autophagy.

They devour and destroy the damaged cell parts and then release the reusable bits back out into the cell so that the cell can use the raw materials to make new usable parts.

People sprinting on a track.

What Causes Autophagy?

Autophagy occurs naturally and at all times in the body but on a relatively slow and minimal scale.

It occurs mainly when the cells of your body are damaged in some way or become deprived of nutrients or oxygen. This is largely why fasting can promote it, as can vigorous exercise.

Fasting stresses the body because there is a lack of resources coming in. Because of this, the body has to conserve all the resources it has since none are coming in.

Essentially, it recycles and repurposes what the body has on hand, which is key in times when new materials don’t seem readily available.

Moreover, the stress induced by not getting a steady supply of energy and resources can decrease the performance of the cells. 

Therefore, by implementing this cleaning process, the cells can try to optimize performance and get rid of the debris that’s junking up the works.

Plus, the cell can essentially eat itself to survive when it can’t eat other fuel sources. This is ultimately the survival mechanism and primary function of autophagy; the fact that it helps the cells function more efficiently is really the bonus.

A notebook with the words intermittent fasting and an alarm clock.

How to Increase Autophagy 

Although autophagy will occur naturally, you can do things to induce it.

Fasting is the primary way to increase it. Fasting deprives your body of nutrients, so this stress requires the body to conserve its resources and repurpose what it has.

You can either accomplish this through intermittent fasting, in which you don’t consume any food for a given period of time, or even through caloric restriction, in which you’re just not giving your body enough energy and nutrients for your needs.

With that said, most studies with fasting have investigated the effects of total caloric restriction—no eating.

According to the Cleveland Clinic, the keto diet, or other high-fat, low-carb diets, as well as certain types of high-intensity exercise can also trigger autophagy.

A notebook with the word keto diet on it, a measuring tape and a fork.

As with intermittent fasting when no calories are coming in, when following the keto diet, the body is starved of a ready access to glucose, causing the body to shift into a state of ketosis. This has been shown to upregulate the rate of autophagy.

As for intermittent fasting, people often wonder how long you have to fast to jumpstart this process. And, when you fast, when does autophagy start?

Many people follow the 16/8 intermittent fasting diet, but is 16 hours fasting enough for autophagy?

Although evidence from research studies has been mixed, this may be anywhere from 18 to 36 hours or more, particularly if you are looking for significant autophagy to occur. 

With that said, some evidence suggests that shorter fasts will stress the body and probably escalate the process to some degree, but most studies have found that it really begins after 24 to 48 hours of fasting. 

An alarm clock on a plate and the word, fasting.

However, the research in this area is still relatively limited.

In sum, autophagy is the process of cellular cleanup in which viable cell components and proteins are recycled, while damaged and misfolded proteins, such as those linked to neurodegenerative diseases like Alzheimer’s, are destroyed, helping protect your body from such diseases and other sources of oxidative damage and premature aging.

Fasting is one of the best ways to increase the process, although other stresses to the body, such as overall caloric restriction, low-carb diets like the keto diet, and high-intensity exercise may also help support it as well.

However, before taking on prolonged fasts or switching to the keto diet, speak with your doctor to ensure these dietary approaches are safe and healthy for you.

For all of our sources on intermittent fasting, check out our database of guides here.

A person holding a mug with one hand and flexing with the other arm.
Photo of author
Amber Sayer is a Fitness, Nutrition, and Wellness Writer and Editor, as well as a NASM-Certified Nutrition Coach and UESCA-certified running, endurance nutrition, and triathlon coach. She holds two Masters Degrees—one in Exercise Science and one in Prosthetics and Orthotics. As a Certified Personal Trainer and running coach for 12 years, Amber enjoys staying active and helping others do so as well. In her free time, she likes running, cycling, cooking, and tackling any type of puzzle.

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