【Revealed by the Latest Research🔬】What Is the NEJM Fasting Paper? 5 Health Benefits Shown by a Medical Journal and How the Metabolic Switch Works

“Is fasting really good for your health? Is there any scientific evidence for it?”

I imagine a lot of people have that question.

In fact, the effects of fasting (intermittent fasting) have been scientifically proven by many top research institutions, including one of the most authoritative medical journals in the world, “The New England Journal of Medicine (NEJM)”.

In this article, I’ll explain the health benefits of fasting in plain terms, based on the latest research data.

I’ll also cover how to read research data correctly, how to start fasting based on the research, and things to keep in mind before you begin.

The World-Renowned Medical Journal NEJM Featured Fasting! What Did the Research Say?

What Kind of Medical Journal Is the NEJM?

To put it in cooking terms, it’s like a restaurant where only the dishes that skilled chefs have tasted and declared “the real deal” make it onto the menu.

That’s why what appears in the NEJM is said to get particular attention even among doctors and researchers.

The Impact the NEJM’s Fasting Paper Had on the World

In 2019, a paper published in the NEJM by Dr. Rafael de Cabo of the U.S. National Institute on Aging and Dr. Mark Mattson (Johns Hopkins University), “Effects of Intermittent Fasting on Health, Aging, and Disease,”
made a huge impact on the medical and health industries.

As a comprehensive review, this paper showed that intermittent fasting improves multiple health markers, including weight management, blood sugar control, brain function, and inflammation.

A review is a paper that gathers and organizes many previously published studies to show what can be said overall.

A single study’s result might be a coincidence, but a conclusion drawn from looking across many studies can be considered more trustworthy.

The NEJM is one of the world’s foremost medical journals, that has published many papers by Nobel Prize winners.

The fact that the effects of fasting were published there was an event that showed the world that fasting is not a “folk remedy” but a “scientifically backed health practice.”

Fasting Research Is Drawing Attention in Japan, Too

In Japan, too, research institutions such as the University of Tokyo and Keio University are studying the relationship between fasting and health, and
the work of Yoshinori Ohsumi, who won the Nobel Prize in Physiology or Medicine for discovering autophagy (the cell’s self-eating process), has further raised scientific interest in fasting.

Autophagy is a mechanism that’s activated during fasting, and it has been shown that it may promote the recycling of aged cells and lower the risk of disease.

The fact that the work of a researcher familiar to Japanese people is involved is probably one of the reasons fasting is getting attention.

My Own Experience as the Author, Matsu

I started fasting right around the time the NEJM paper was making headlines.

What first got me going was thinking, “If there’s this much scientific evidence, I’ll give it a try.”

When I actually started, I was able to feel the effects described in the paper in my own body, for real.

The 5 Major Health Benefits of Fasting Proven by Research

An Overview of the 5 Benefits

Here are five representative health benefits of fasting that have been revealed by multiple studies, including the NEJM.

All of these benefits are supported by peer-reviewed (checked by experts) academic papers.

I myself lost 15 kg (about 33 lb) in 3 months of continued fasting, and my blood test numbers improved too.

Being able to feel in my own body what science has proven gave me a huge boost of confidence.

Benefits 1 and 2: Why Your Weight and Blood Sugar Come into Balance More Easily

Insulin, which is released every time you eat, brings blood sugar into your cells and at the same time stores excess energy as fat.

When the time without eating gets longer, insulin is released less, and your body switches toward taking out and using the fat it has stored.

HbA1c (hemoglobin A1c) is a number that shows your average blood sugar over roughly the past 1 to 2 months, and it’s commonly used in health checkups.

If fasting blood sugar is “a snapshot of your blood sugar that day,” HbA1c is like “a report card on your blood sugar over the past while.”

Benefits 3, 4, and 5: Effects on the Brain, Inflammation, and Cells

BDNF is a substance that grows and protects nerve cells in the brain; you could call it a kind of “fertilizer for the brain.”

CRP is a substance that increases when inflammation is happening in the body, and it’s used in blood tests as a guide to how much inflammation there is.

Chronic inflammation is a state where a small fire keeps smoldering inside your body, and it’s said to cause all sorts of health problems without you noticing.

Fasting calms this “smoldering,” and autophagy cleans up old parts inside your cells, which together make it easier for your body’s overall condition to come into balance.

I also go into detail about the relationship between fasting and the brain in “【Backed by Research】Helping Your Brain Stay Young! How Fasting Energizes Your Brain【BDNF】.”

The Scientific Mechanisms That Make Fasting Effective

“Metabolic Switching” Holds the Key

The biggest reason fasting is good for your health lies in a mechanism called “metabolic switching”.

It may sound a bit complicated, but the mechanism itself is simple.

Normally, your body uses glucose (sugar) as its main source of energy.

But when fasting depletes the glycogen in your liver, your body breaks down fat to make ketone bodies and starts using them for energy.

Glycogen is like a “sugar savings account” that can be stored in your liver and muscles.

Just as a hybrid car switches between gasoline and electricity as it runs, your body switches between two fuels, “sugar” and “fat,” depending on the situation.

Ketone bodies are a highly efficient energy source for the brain, and they’re said to lead to better focus, memory, and emotional stability.

Lower Insulin Levels Change Your Body

When the time without eating continues, the insulin concentration in your blood drops significantly.

That’s because with no food coming in, insulin, whose job is to lower blood sugar, has nothing to do.

When insulin is low, fatty acids are more easily released from fat cells, and fat burning moves forward.

Improved insulin sensitivity is also thought to help prevent type 2 diabetes.

Insulin sensitivity refers to how “responsive” your body is, meaning it can properly deliver blood sugar to your cells even with a small amount of insulin.

I explain how blood sugar changes with 16-hour fasting in “【The Latest Intermittent Fasting Research】Does 16-Hour Fasting Lower Blood Sugar? Why It Can Rise and How to Prevent Blood Sugar Spikes.”

Cellular Self-Repair Through Autophagy

About 16 hours after a fast begins, autophagy is activated inside your cells.

Autophagy is a mechanism by which cells break down and reuse old proteins and poorly functioning mitochondria.

Mitochondria are like “power plants” inside your cells that produce energy.

This rejuvenates cells and is said to possibly lower the risk of cancer and neurodegenerative diseases (such as Alzheimer’s).

Actually, I feel I’ve been catching fewer colds since I started fasting.

It may be that my immune function is getting into better shape.

For the relationship between diet and dementia prevention, also see “Too Much Sugar Doubles Your Dementia Risk!? A Diet for Preventing Alzheimer’s.”

Key Points for Reading Fasting Research Data Correctly

Research Has “Levels of Reliability,” Too

Even when people say “research has shown,” how reliable it is varies greatly depending on how the research was done.

Let’s sort out the commonly used types of research along with a rough guide to their reliability.

In an RCT, dividing participants randomly reduces biases such as age and lifestyle habits, making it easier to compare the effects of the methods themselves.

On the other hand, even if animal experiments produce good results, the same effects won’t necessarily appear in humans.

Check “Who, and for How Long”

When looking at research results, who the study focused on is also an important point.

For example, the results of a study on people with obesity won’t necessarily apply as-is to people who are thin.

Also, whether effects seen in a study lasting a few weeks will continue in the same way when you keep it up for years needs to be confirmed separately.

When you see a headline like “Fasting improves XX!” in the news or on social media, it’s reassuring to get into the habit of checking who the original study looked at and for how long.

“It Works” and “It Suits Everyone” Are Two Different Things

Even if research shows an effect on average, not everyone will get the same effect.

Depending on your constitution, chronic conditions, age, and daily rhythm, the method that suits you and the fasting time that works best differ from person to person.

It’s important to take research results as a guide that “it’s worth trying to see whether it suits you,” and to adopt fasting while listening to your body.

I also introduce comparative data on fasting and calorie restriction in “【Fasting vs. Calorie Restriction】Which Makes It Easier to Lose Weight Effectively? A Thorough Comparison with Scientific Data.”

How to Start Fasting Based on the Research, and What to Watch Out For

Types of Fasting Commonly Used in Research

Fasting research uses several set methods.

Of these, 16:8 fasting is an easy method to fit into daily life, since your sleeping hours can count toward your fasting time.

Beginners Should Start at 12 Hours and Build Up Gradually

If you jump straight into 16 hours, the hunger and fatigue can feel tough.

Start by leaving 12 hours between dinner and the next morning, and once you get used to it, gradually extend it to 14 hours and then 16 hours.

During your fast, stay hydrated by drinking calorie-free beverages like water, tea, or black coffee frequently.

Starting on a day when you have time to spare, like a day off, makes it easier to calmly observe the changes in your body.

In the first few days while your body is adjusting, you’re likely to feel hungry, but in most cases it gradually settles down.

What You Eat During Your Eating Window Matters, Too

To make the most of fasting, what you eat during your eating window is also important.

Center your meals on protein (meat, fish, eggs, soy products), vegetables, mushrooms, seaweed, and so on, and go easy on processed foods and sweet drinks.

Be careful, because if you gobble down sweets or sweet pastries for your first meal after a fast, your blood sugar will spike.

I explain the basics of how to fast in detail in “【The Complete Beginner’s Guide】What Is Intermittent Fasting? Types, Benefits, How to Do It, and Why You Might Not Be Losing Weight, Explained Simply.”

People Who Should Avoid Fasting

Research has shown that fasting has many benefits, but it isn’t right for everyone.

If any of these apply to you, don’t start fasting on your own judgment; be sure to consult a doctor.

In particular, if you take blood-sugar-lowering medication, you need to be careful, because fasting may cause your blood sugar to drop too low.

Common Discomforts When You First Start

When you first start fasting, you may experience hunger, headaches, fatigue, or irritability.

This is thought to be because your body isn’t yet used to switching from “sugar-burning mode” to “fat-burning-too mode.”

Discomfort is more likely when you’re short on fluids or minerals, so drink water or tea frequently, and replenish minerals with vegetables and seaweed during your eating window.

If dizziness, heart palpitations, or strong fatigue continue, don’t push yourself; stop fasting.

Don’t Put Too Much Faith in “Proven by Research”

Fasting isn’t a treatment for curing disease; it’s simply one lifestyle habit that supports your health.

If you’re being treated for a chronic condition, don’t stop your medication or treatment on your own judgment because you’re fasting.

Making good use of research results while checking in with how your body feels and continuing without strain is the surest path.

Frequently Asked Questions About the Health Benefits of Fasting and the Latest Research, Including the NEJM

Get a Healthy Body and Brain Starting Today with the Fasting Science Has Proven

The health benefits of fasting have been proven by the world’s top medical journals, starting with the NEJM.

It’s not just a trendy diet; it’s a scientifically backed health habit.

Metabolic switching, improved insulin sensitivity, and activated autophagy: these mechanisms combine to bring wide-ranging health improvements, including to your weight, blood sugar, brain function, and cell rejuvenation.

That said, research results aren’t a promise that “it works the same for everyone,” so adopt fasting while keeping an eye on how your body feels.

There’s no need to overthink it.

Simply starting with a 12-hour fast, then, once you’re used to it, extending to 16-hour fasting, “not eating from dinner until lunch the next day,” is enough for you to start feeling these effects.

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