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Fasting or time-restricted eating is all about not eating, or at least reducing some or all food, drink, or both, for a period of time. In more recent years fasting has become scientifically recognized for its excellent health benefits. There are a growing number of studies confirming this is a legitimate means of managing weight and preventing disease.  Now scientists are reporting that fasting can also significantly improve our gut health.

The link between a healthy gut and longevity

More than 70% of your immune system is directly related to your gastrointestinal tract.  Issues with gut health, as well as our corresponding ability to correctly absorb nutrients, affect everything in our bodies.

Indeed, about 90% of what we eat is assimilated into the small intestine. Without good gut function, we will feel unwell, have brain fog,  experience bloating, and even be constipated. We will put on weight or struggle to lose weight, sleep badly, and get sick more often.

Importantly, our gut health has a direct impact on what diseases we will get. It’s such a powerful influence on our body, that it’s often referred to as the second brain.

As Frank Lipman, MD explains,

“The gut is known as “the second brain” because, woven into the gut, two thin layers of more than 100 million nerve cells that line the walls of your gastrointestinal tract. This “brain in your gut” helps manage your digestion, mood, health and even the way you think.”

fasting and belly fat


Striving for a healthier microbiome

In a 2018 study, published in PubMed, the study authors cited Hippocrates’ theory that all diseases begin in the gut.

While some may argue against such a sweeping view, others are more open to considering just how important our gut biome is. Indeed, how we manage the microbiome is becoming a pivotal area of scientific focus. Many chronic metabolic conditions are said to be caused or influenced by chronic gut inflammation.

“The Hippocratic quote “all disease begins in the gut” seems to be true, over 2,000 years later, for diverse pathological conditions. Our knowledge of the pivotal role of the intestinal barrier and gut microbiota in health and disease has been majorly developed and currently constitutes a scientific field of intense research.”  – National Library of Medicine

How and why?

According to Healthline, “the term “gut microbiome” refers to the microorganisms living in your intestines. Each person has about 200 different species of bacteria, viruses, and fungi in their digestive tract.

Some microorganisms are harmful to our health, but many are incredibly beneficial and even necessary for a healthy body.”

Researchers say that having a large variety of bacteria in the gut may help reduce the risk of diseases like diabetes, inflammatory bowel disease, and psoriatic arthritis.

We also need a higher level of diversity of gut bacteria to enjoy good health.  So having too much of the wrong bacteria can be as bad as too little.

What happens when our gut health is poor?

Healthline reports that one of the outcomes of poor gut health is inflammation.

“Undesirable bacterial products called endotoxins can sometimes leak through your gut lining and enter the bloodstream. Your immune system then recognizes these foreign molecules and attacks them. This gives rise to chronic inflammation.” – Healthline

Leptin resistance

In turn, diet-induced inflammation can trigger insulin and leptin resistance. This, says HealthLine, is when leptin resistance occurs. “When your body does not respond to the hormone leptin. Furthermore, leptin resistance is now believed to be the leading driver of fat gain in humans. Leptin resistance in turn is instrumental in driving factors for type 2 diabetes and obesity. It’s also believed to cause fatty liver disease.”

Good gut health is vital to life

Zach Bush MD, is an internationally recognized educator and thought leader. He believes that as human beings our neurologic capacity begins with our connection to the microbiome.

“It is, in its entirety, vital to life and the reason why we are here today. Without the microbiome, life on Earth would not exist.” Zach Bush MD

Bush explains that at its most basic definition, micro means small. And biome means living creatures — essentially all the living microbes on and inside the human body.

gut health | Lonngevity LIVE


Importance of fungi and bacteria

He says human cells are not at the foundation of the human microbiome, but rather they are the fungi and bacteria that are. It is estimated that we have 50 to 70 trillion human cells. This pales in comparison to the 1.4 quadrillion bacteria and 10 quadrillion fungi inside our bodies.

It’s what fuels our development, immunity, and nutrition, enabling our production of energy, micronutrients, and regenerative pathways. Within every organ system throughout our whole body, it’s this unique niche of bacteria, fungi, and yeast that nurtures our human cells.

“Our gut microbiome changes quickly over our first year or two, shaped by microbes in breast milk, the environment, and other factors. It then stabilizes by the time we are about three years old.”

“But our environment, our long-term diet, stress and the drugs we take, such as antibiotics, continue to play a role as we age, meaning our microbiome can change throughout our life.” – Zach Bush MD

Science links fasting to better gut health

The starting point is to check in on your gut health. If you are diagnosed with a gut health problem, then you’ll need to make lifestyle adaptions. Medical specialists have a variety of means to test the state of your microbiome.

Here is a summary of the key habits to develop for a healthier microbiome, but not limited to:

  • Follow a healthy, primarily plant-based diet, rich in foods that are gut-friendly,
  • Cut down on your sugar intake and food high in sugar,
  • Reduce or eliminate the use of antibiotics and other medication that interferes with your gut biome,
  • Ensure you get enough proven prebiotics and probiotics, either from food, or supplementation. But only if you need them. Remember a good gut is a balance and over-supplementation can be detrimental. Always consult a professional before you commit to a supplementation especially if you have any underlying medical conditions.
  • Do regular  exercise,
  • Limit your exposure to other negative lifestyle factors, such as lack of sleep and stress and,
  • Practice Time-restricted eating, or fasting.

The last point is the focus of this article. And while this is one of the less common health indicators for maintaining good gut health,  it is worthy of our attention. There are a growing number of newer studies that confirm fasting will improve gut health.

Studies show the link between fasting and your microbiome

For some time now, scientists investigating the gut health link to longevity have also studied the impact fasting may have on the microbiome.  Here are just a few.

Lower risk of cancer and inflammatory bowel disease

One study involving healthy men observing fasting periods has shown a positive link between good gut health and fasting. The men fasted for around 16 hours per day during the Islamic holy month of Ramadan. At the end of the month, the participants’ gut microbiomes had higher levels of Lachnospiraceae.  This is a beneficial bacteria that has been linked to a lower risk of cancer and inflammatory bowel disease, and improved heart health and mental health.

However, after they stopped daily fasting, the men’s gut microbiomes returned to their previous state.

The study researchers commented:

Intermittent fasting provokes substantial remodeling of the gut microbiome. The intermittent fasting–provoked upregulation of butyric acid–producing Lachnospiraceae provides an obvious possible mechanistic explanation for the health effects associated with intermittent fasting.”

Fasting promotes beneficial bacteria

In another study published by Cambridge University Press, a group of young men following the 16/8 approach saw a significant increase in their overall microbiome diversity.

They also had higher levels of specific beneficial bacteria called Prevotellaceae and Bacteroidetes, which are associated with reduced markers for obesity and better metabolic health. The researchers concluded,

“Therefore, Time Restricted Feeding  (TRF), could be a safe therapeutic remedy for the prevention of metabolic diseases related to dyslipidaemia and elevated liver function, as it regulates circadian rhythm associated with gut microbiome modulation.”

How fasting works on assisting gut health

Time-restricted eating involves eating all your day’s calories in a compressed “feeding window” of between four and 10 hours.

What are the time-restricted eating guidelines?

For example, you might eat only between the hours of 8 a.m. and 2 p.m., or only between noon and 8 p.m.

Emeran Mayer, MD, is a professor of medicine and founding director of the Goodman Luskin Microbiome Center at the University of California, Los Angeles. He is also the author of The Gut-Immune Connection, a book about the role the microbiome plays in immune functioning.

Mayer says that some gut bacteria produce molecules that switch off inflammation. Other bacteria support healthy gut-barrier functioning.

“There’s evidence that the action of the migrating motor complex may support the growth and positioning of these so-called “good” bacteria while reducing the presence of competing “bad” bacteria species.” Emeran Mayer, MD

When your tummy grumbles you’re helping to clean up your gut

Mayer believes time-restricted eating may be helpful to the microbiome. His theory is based on the concept of the migrating motor complex or MMC. MMC  is not widely talked about, yet, he says, it is highly efficient.

“You have the best cleansing regimen built right into your gut if you leave it empty for 12 to 14 hours.”

He says the best way to activate MMC is to avoid all calories between 8 p.m. and 10 a.m.

“The 14 hours without food intake would allow the MMC to kick in and not only cleanse your gut of any indigestible, un-absorbable food components. It will also help to reestablish the normal proximal-to-distal gradient of gut microbial density.” 

What is migrating motor complex or MMC?

You may be wondering what this migrating motor complex (MMC) is. Well, this is one of our body’s most important mechanisms for proper digestion. The mechanism refers to the periodic mobility pattern that occurs in the upper gastrointestinal (GI) tract,  during the fasting state.

More simply put, when your tummy rumbles, then you know you are in MMC mode.

Research in the journal Nature Reviews refers to the stomach rumbling caused by the  MMC.

“The MMC is a repeating cycle of powerful contractions that help push bits of food, bacteria, and other GI junk down toward your colon — sort of like a swallowing reflex that spans your entire gut.”

The housekeeper of the small intestine

By enabling our MMC, we let loose the “housekeeper” of the small intestine clean up. This may well be one of the most under-appreciated factors when it comes to the health of our digestive system.

Fasting and MMC

Along with pushing any left-over bits of food out of your stomach and upper GI tract, the migrating motor complex also appears to rebalance our gut’s bacteria populations. This enables more gut bacteria to go down into the large intestine, as opposed to higher up in the small intestine.

“The normal distribution of your gut microbiome should be heavily weighted toward the lower GI tract. The overgrowth of bacteria in the small intestines is associated with gut dysfunction.”

Therefore, the MMC may also play a role in the maintenance of normal gut microbial geography.

Less snacking, more fasting

In order to activate the MMC fully, you have to do less snacking and more fasting.  This obviously requires discipline and commitment because the MMC only goes to work on an empty stomach.

“The minute you take a bite of food, it shuts down.”  says Emeran Mayer MD

The bottom line

So if Mayer and other scientists are right, fasting may well off a simpler way to improve gut health.  It may well become a cornerstone longevity practice. And best of all,  it’s free!


Gisèle Wertheim Aymes

Gisèle Wertheim Aymes

Gisèle is the owner of the Longevity brand. She is a seasoned media professional and autodidactic. Her goal? Sharing the joy with others of living in good health, while living beyond 100, You can follow her @giselewaymes on Twitter and Instagram or read her Linked-In profile for full bio details.


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