When Does Autophagy Start? Basics and How to Trigger It

author avatar Dr. Eric Berg 06/01/2024

Autophagy can be triggered by prolonged fasting and is a survival mechanism that recycles old and damaged cell components. But when does autophagy start?

Though autophagy constantly occurs, the process is magnified within 16 to 48 hours of starting a fast. 

Discover the profound health benefits of autophagy and how to induce cellular renewal and recycling processes. 

Human cell rendering

What is autophagy?

Autophagy, which translates from Greek into “self-eating,” refers to the body’s ability to remove and recycle damaged proteins and cellular organelles. 

Damaged and misfolded proteins can lead to compromised cell function and death. These toxic proteins can form due to genetic mutations, environmental toxins, oxidative stress, or age-related changes in cellular processes. 

Healthy cells are required for the body to produce energy, regenerate itself, and obtain nutrients from food. Impaired cell function and cell death can lead to chronic diseases, including neurodegenerative disorders and heart diseases, and can trigger tumor growth. 

Autophagy also helps destroy and remove potentially harmful pathogens such as bacteria, fungi, mold, and viruses. These microbes can cause various infectious diseases, allergies, and breathing difficulties. 

Additionally, autophagy is a survival mechanism designed to sustain periods of starvation by allowing the body to use damaged cellular components as a fuel source. 

How autophagy works

Autophagy is triggered when cells enter survival mode through extended fasting. 

Reduced calorie intake deprives the body of fuel sources and nutrients needed to function. This forces cells to break down and recycle damaged or unnecessary components to generate energy.

Sequestration is the first step in autophagy, characterized by the formation of a structure surrounding defective cell parts known as an autophagosome. 

When an autophagosome encloses a damaged cell, an organelle called a lysosome releases enzymes to degrade dysfunctional cellular components into usable amino acids. 

These amino acids can then be turned into adenosine triphosphate (ATP), the body’s primary energy currency.

While autophagy typically stimulates cellular renewal, it can also cause apoptosis, which refers to the programmed cell death of dysfunctional cells. This has been linked to anti-aging effects and may lower the risk of certain cancers.

Watch the video below to learn how to trigger autophagy. 

12 Ways to Trigger Autophagy

Benefits of autophagy

Triggering autophagy can have various health benefits, including brain cell renewal and a lower risk of age-related neurodegeneration. 

A study published in the Journal of Molecular Biology found that autophagy dysfunction can contribute to and speed up the progression of neurodegenerative diseases. 

This is linked to autophagy’s role in clearing the buildup of toxic protein aggregates in the central nervous system associated with the development of Alzheimer’s and Parkinson’s Disease.  

This natural process is also associated with improved cognition, enhanced memory, and reduced brain fog.

Research published in Advances in Experimental Medicine and Biology found that autophagy is essential for healthy brain neurons and that poor autophagy pathways can worsen neurodegeneration and memory problems.

Additionally, autophagy can help regulate inflammatory responses and boost immunity by destroying pathogens, microbes, parasites, and viruses. 

Autophagy may also help protect against cancer. Cancer cells typically display mitochondrial gene mutations, which can trigger abnormal cell growth and cancer. Because autophagy destroys damaged mitochondria, it may help lower the risk of developing tumor cells. 

Clock with healthy food

How long does it take to start autophagy?

Though more research is needed to determine precisely when autophagy begins in humans, animal studies show that water fasting enhances autophagy within 24 hours and increases with prolonged fasting.

A study published in Autophagy found that autophagosome formation began at 24 hours and peaked at 48 hours of fasting in animals. 

However, it may be possible for autophagy to start sooner. At around 16 to 18 hours of food restriction, the body depletes blood sugar and glycogen stores and begins producing ketones.

Ketones are metabolic by-products of fat breakdown and have been shown to stimulate autophagy. Increasing concentrations of ketones in the body may shorten the duration required for autophagy to occur.

Ketone blood test

Signs of autophagy

When cells don’t receive enough glucose to use for energy, the liver starts to break down fats which releases large amounts of ketones bodies. Ketones are a group of organic acids and a highly efficient fuel source for the body.

A study published in Neurochemical Research found that ketones can stimulate autophagy induction. 

This explains why the presence of ketones is a primary sign of autophagy, and ketone testing using blood, urine, or breath can help determine their levels accurately.

Bad breath is also a common sign of autophagy, especially for those following a ketogenic diet. Limiting carbohydrates and sugar can quickly deplete glycogen stores, which triggers the production of ketones and, subsequently, autophagy.  

Additionally, a reduced appetite can indicate your body has entered autophagy. Fasting and a low-carb diet stimulate the release of ketones, which have appetite-suppressing properties. 

Intermittent fasting plate concept

5 ways to trigger autophagy 

Autophagy can help protect against disease and support healthy cellular function while having profound anti-aging effects. 

Here are five ways to induce autophagy.

1. Practice intermittent fasting

Intermittent fasting and calorie restriction are the most effective ways to induce autophagy.

Fasting deprives the body of nutrients, forcing cells to recycle dysfunctional cellular components to survive and function. 

However, depending on metabolic health and glycogen stores, it may take between 16 and 48 hours of fasting before autophagosomes are produced.

Individuals practicing a low-carb ketogenic diet tend to enter autophagy sooner due to the reduced availability of glucose and glycogen. In contrast, those following a high-carb diet may only achieve autophagy after 24 to 48 hours into a fasting period.

2. Exercise regularly 

Exercise can trigger autophagy by quickly depleting glucose and glycogen stores, which pushes the body to use alternative fuel sources. 

HIIT exercises, resistance training, long walks, or jogs can increase autophagy markers, especially when paired with fasting.

“The amount of autophagy is related to the intensity and volume of exercise you do,” explains Dr. Berg. “A high-intensity resistance workout or low-intensity endurance exercise generates the most autophagy.”

An active lifestyle also enhances insulin sensitivity, which helps maintain steady blood sugar levels, making it easier to enter autophagy. 

Iced coffee with cream

3. Drink coffee

Research shows that drinking coffee can induce autophagy in liver, heart, and muscle cells for up to four hours after consumption. 

The study published in Cell Cycle found that “Although caffeine has been shown to induce autophagy, caffeine is apparently not required for coffee-induced autophagy. Rather, other coffee components that are not eliminated during the decaffeination process, presumably polyphenols, must be responsible for these effects.”

Polyphenols are plant compounds with antioxidant effects that may stimulate pathways linked to cellular regeneration and the removal of damaged or dysfunctional cell components. 

4. Try hot/cold contrast showers

Contrast showers involve alternating between hot and cold water. Extreme temperature changes can trigger mild stress and activate genes that stimulate autophagy.

Evidence published in iScience found that chronic cold exposure induced autophagy and maintained mitochondrial integrity and survival in animals. 

The researchers also suggest that autophagy is necessary for thermogenesis, the mechanism through which mammals generate heat and maintain body temperature.

5. Take coconut oil

Coconut oil contains medium-chain triglycerides (MCTs), which are fatty acids that have been shown to metabolize directly into ketones. 

Consistent availability of ketones can speed up autophagy and may be achieved by taking one to two tablespoons of coconut oil while fasting.

Discover more ways to trigger autophagy by receiving a downloadable guide that discusses 25 Ways to Activate Autophagy, delivered directly to your email inbox.

Cells and DNA rendering

Key takeaways

Autophagy is a biochemical process in which nutrient-deprived cells recycle damaged and dysfunctional components to produce energy for survival and cellular repair. 

This crucial cellular repair mechanism can be triggered by prolonged fasting, but when does autophagy start? 

The time autophagy begins can vary, but evidence suggests that autophagy can start after around 16 hours of caloric restriction and peaks between 24 and 48 hours of fasting. 


1. How long does it take to start autophagy?

There’s no proven timeframe for when autophagy starts in humans, as it depends on the individual's metabolism, activity levels, and nutritional status.

However, animal studies suggest that advanced autophagy occurs around 24 hours of fasting and increases with prolonged caloric restriction. 

2. How do you know when autophagy starts?

Autophagy is associated with various signs, including increased ketone levels, reduced appetite, and increased cognition. 

Bad breath can also signal autophagy as the body produces a type of ketone called acetone, which can lead to body odor and bad breath.

3. Can a 16-hour fast start autophagy?

Yes, inducing autophagy may be possible with a 16-hour fast, especially for those following a low-carb ketogenic diet. 

Depleting blood sugar and glycogen stores is key for activating autophagy, which explains why consuming a low-carb diet can help promote autophagy.

4. Is autophagy good for the body?

Yes, autophagy has profound health benefits. This natural process allows the body to recycle and repurpose cell components for energy and healthy tissue generation.

Autophagy plays an important role in reducing disease risk, strengthening the immune system, and slowing aging processes. 

5. Does coffee stop autophagy?

No, coffee won’t stop autophagy unless it contains ingredients that increase blood sugar levels, such as sugary creamer. 

In fact, it’s believed that certain polyphenols in coffee can stimulate cellular renewal and may trigger autophagy. 


  1. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7232022/ 

  2. https://pubmed.ncbi.nlm.nih.gov/32468455/

  3. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3106288/ 

  4. https://pubmed.ncbi.nlm.nih.gov/26303508/ 

  5. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4111762/ 

  6. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC8134067/

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