The 24-hour fast once a week can be a sweet spot between daily intermittent fasts and prolonged fasts. It doesn’t demand daily consistency, but nor does it require much preparation and conditioning for most people.

The greatest benefits of fasting are linked to physiological changes that occur when your body depletes the energy it receives from food as well as the energy stored in muscle and liver tissue as glycogen.

Your body can store around 2000 calories as glycogen, and it takes an average of 24 hours to deplete this stored energy. [1] During this period your body shifts from and ‘anabolic’ phase of converting nutrients from food into body tissue, into a ‘catabolic’ phase where your body breaks down glycogen along with body fat into energy molecules.

The catabolic phase is when your metabolism becomes ketogenic, and the process of cellular renewal called autophagy is engaged. Both of these physiological modes are linked to various health benefits which we’ll explore in this article.

Summary of the Benefits of a 24 Hour Fast Once a Week

The 24-hour fast is often called “Eat Stop Eat” approach and entails abstaining from eating for 24 hours once or twice a week.

It was developed by nutritional researcher Brad Pilon based on data from his studies at the University of Guelph. [2]  You can read about his specific findings in the book, “Eat Stop Eat.”

Essentially, what Pilon and others have discovered is that the 24-hour fast may be an optimal approach to unlocking the benefits of intermittent fasting, even when only practiced once a week.

diagram showing effects of 24 hour fast

Source: Phillips, M.C.L. Fasting as a Therapy in Neurological Disease. Nutrients 2019, 11, 2501

During the 24-hour fast your body triggers deep, regenerative processes that have been shown to [3] [4]

  • Reduce heart disease risk factors
  • Reduce stored body fat
  • Support blood sugar regulation and insulin sensitivity
  • improve levels of triglycerides and cholesterol
  • Stimulates autophagy, which protects against various infections and diseases
  • stimulate the production of beneficial hormones HGH and BDNF
  • reduce cancer risk

Now let’s take a deeper look at how a 24-hour fast once a week can produce these benefits.

diagram of intermittent fasting benefits
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1. Reduced Body Fat

During a 24-hour fast, insulin drops and norephedrine increases, triggering your body to oxidize fatty acids into energy molecules called ketones. [5] [6]

This process retains lean muscle mass while reducing body fat. [7]

During the 24-hour fast your metabolic rate may rise by 14%. At this rate, your body will be burning calories while resting, thereby increasing your fat-burning and potential weight loss. [8] [9]

Studies have found that intermittent fasting promotes up to a  9.9% loss of body weight. [10]

2. Autophagy (Cellular Repair and Renewal)

The word autophagy means self-eating and refers to a process where intracellular debris and old cell parts called organelles are recycled into new cell parts.

This process of cellular renewal has been shown to protect the body from various diseases, viruses, and infectious bacteria. [11] [12] [13] [14] [15]

As you can imagine, not entering autophagy renders your body more susceptible to infection and diseases, including diabetes, neurological disorders, and even cancer.

Studies show that autophagy occurs after fasting for at least 16-18 hours and increases beyond that, making the 24 hours an effective autophagy-inducing method. [16] [17] [18]

By undertaking a 24-hour fast once a week, you are gifting your body with the numerous downstream benefits of autophagy, including

diagram of autophagy on 24 hour fast

Source: Nature

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3. Intestinal Stem Cell Production

Our intestines are the first line of defense against food-borne pathogens and toxins. Especially those that most people unknowingly consume on a daily basis, like excess fiber, sugar, and naturally occurring plant toxins and antinutrients.

All of these factors can cause gaps in your intestinal cells, allowing antigens to enter your bloodstream and get deposited throughout the body. This condition, known as intestinal permeability, can lead to chronic inflammatory disorders. [27]

MIT researcher Dr. David Sabatini found that the 24-hour fast “provided evidence that fasting induces a metabolic switch in the intestinal stem cells, from utilizing carbohydrates to burning fat.” And that this switch “enhanced [cell] function significantly.”

In Sabatini’s study, he found that a 24-hour fast stimulated stem cell production to the degree that it reversed age-related loss of stem cell function, increased energy, cellular protection, and various markers of youthfulness. [28]

4. Improved Insulin Sensitivity

One of the key benefits of a 24-hour fast once a week is improving insulin sensitivity.

Some of the common diseases associated with insulin resistance include heart disease, type 2 diabetes, PCOS, cognitive decline, and memory loss. [29]

A 2022 review of numerous studies found that fasting improves insulin resistance to such a significant degree that it may be a valuable treatment for many chronic diseases linked to insulin resistance. [30] [31]

Additionally, improving insulin sensitivity has been shown to promote

  • Clearer skin
  • less water retention
  • Reduced diabetic symptoms
  • Reduced risk of heart disease
  • Cognitive and neurological protection
  • Resolution of PCOS

5. Increased HGH (Human Growth Hormone)

The 24 hour fast once a week can promote the production of HGH (human growth hormone)

A classic study of 200 participants doing a 24-hour fast found that this period can increase HGH by a factor of 20 in men and 13 in women. [32]

Higher levels of HGH (human growth hormone) in your blood are associated with improved memory, increased muscle mass, less water retention, and a reduction in the stress hormone cortisol. [33]

6. 24-Hour Fast for Increased BDNF

Leading neuropsychiatrist John J. Ratey popularized BDNF by deeming it “Miracle-Gro for the brain.”

BDNF-1, is the acronym for brain-derived neurotrophic factor–a hormone that helps generate brain cells.

It’s viewed as a benefit of fasting for 24 hours once a week because studies have found that Increased serum levels of BDNF are associated with better learning and the development of new neural pathways.

Low levels of BDNF are associated with Parkinson’s, Alzheimer’s, and other neurodegenerative disorders. [34]

Studies how found that IF can increase BDNF, which may account for reduced depression, anxiety, and neurodegenerative diseases in animal subjects. [35]

7. Reduce Inflammation by Fasting for 24 Hours Once a Week

Chronic inflammation is the root of the deadliest diseases on earth, including heart disease, stroke, respiratory diseases, cancer, obesity, and diabetes. [36] [37] [38] Together, these inflammatory diseases kill 3 out of 5 people worldwide.

If you’re a U.S. citizen, there’s a 60% chance that you have at least one inflammatory condition. [39]

Fasting for 24 hours once a week activates three anti-inflammatory mechanisms.

  1. Stem cell stimulation that regenerates your intestinal barrier, protecting against leaky gut
  2. Promoting the process of autophagy that removes inflammatory antigens, bacteria, and viruses.
  3. Reducing inflammatory white blood cells called monocytes [40]

Not surprisingly, studies have found that fasting is an effective treatment for rheumatoid arthritis, Sjogren’s, MS, and other inflammatory conditions. [41]

diagram of the effects of fasting on inflammation

Source: Cell Metabolism. VOLUME 18, ISSUE 6, P844-859, DECEMBER 03, 2013

Benefits of a 24 Fast Once a Week: The Takeaway

There are numerous powerful benefits of a 24 hour fast once a week. This fasting duration activates deep autophagy and ketosis, improves insulin sensitivity, and promotes the production of beneficial hormones HGH and BDFN-1.

Together these processes provide powerful benefits that protect the body from inflammatory diseases, viral and bacterial infections, and support cognitive health, longevity, heart health, and weight loss.

Practicing a 24-hour fast once a week may be a convenient approach for people who struggle with daily intermittent fasts while making it easy to stay nutritionally replete.

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