Food Gut

Intermittent Fasting

Is there an optimal daily feeding pattern?


What Is A Feeding Window?

Time-restricted eating is all the rage in health communities and discussion groups, and for good reason: It offers benefits that go beyond the diet.

Time-restricted eating (which involves intermittent fasting and feeding windows) involves intentionally eating at specific times, and avoiding eating the rest of the time.


Rule #1

Eat only during the “window” of time.

Ex: You may eat from 9 AM to 5 PM.


Rule #2

Fast (don’t eat) outside the window.

Ex: Don’t eat after 5 pm until the next morning at 9 am.

There Are Many Variations

There are all sorts of odd methods, (such as “one meal per day” or “36 hour fast/12 hour binge”). The more extreme the approach, the larger the amount of risk.

However, the most popular approach is an 8-hour feeding window. All calories for the day are eaten between 9am and 5pm.

There are some variations to the 8-hour window, but 9AM-5PM is the safest, most effective option for most people.

Intermittent Fasting is eating within a window of time — and fasting the rest of the day.

This is often referred to as:
“Time-Restricted Eating.”


The Benefits Of Time-Restricted Eating

There are definitely some interesting effects when eating this way.

Keep these important questions in mind concerning time-restricted eating:

  • Are these benefits available to everyone?
  • Are they sustainable in the long-run?
  • Further, is time-restricted eating the only way to achieve these benefits?

Let’s look at some of the benefits.

#1 — You can lose weight

  • You’ll probably eat fewer calories. It’s difficult to eat as many calories in a short time span.
  • Going hours and hours without eating causes your body to burn through its glycogen stores and burn fat for fuel.

#2 — It can be convenient

  • Your whole day “opens up” when you don’t need to stop and eat.

#3 — Fasting Can Temporarily Benefit Gut Health

  • Microbes living in your gut largely determine gut health.
  • In poor gut health, bad microbes are fed at every meal.
  • When fasting, bad microbes are not fed — which means virtually zero endotoxin is released (by the bad microbes) for many hours of the day. This can represent a powerful relief from “systemic endotoxicity” caused by poor gut health for much of the day.

#4 — It can increase autophagy

  • Autophagy — When the body cleans up old, junk proteins inside cells.
  • Occurs when food is not being digested — beginning after about 12 hours of fasting.

#5 — You can avoid circadian mistakes

  • Eating is a signal to the brain that it is daytime.
  • Daytime eating tells the brain “It is daytime.
  • Therefore, eating at night confuses the brain’s clock, dysregulating the circadian rhythm.

#6 — Can improve NADH to NAD+ ratio

  • A higher NAD+ ratio (to NADH) is associated with better longevity and metabolism.
  • This research is in its infancy.


What Does The Science Say?

The science is actually quite scant about intermittent fasting. Not many studies performed on the subject of time-restricted eating. This may be surprising, given how much media attention this approach has enjoyed.

There is a 2018 study that demonstrated that time-restricted eating improved the following markers in prediabetic men, even though none of them lost weight:

  • insulin sensitivity
  • blood pressure
  • oxidative stress
  • appetite

The 6-hour feeding window these men followed was 8am to 2pm.


Time-Restricted Eating Options

Here are some examples of different popular approaches. Let’s start with the smallest of “feeding windows.”

2-Hour Feeding Window

This is essentially: “One Meal A Day” (OMAD). It’s quite popular and incredibly difficult to follow, long-term.

4-Hour Feeding Window

8-Hour Feeding Window

The 8-hour feeding window is extremely popular, though still somewhat extreme.

Two Common Options
  • 9am-5pm
  • 12pm-8pm

12-Hour Feeding Window

A much more relaxed, sustainable, feeding window.


Who Benefits From Time Restricted Eating?

The folks who stand to benefit the most from intermittent fasting are those struggling with:

  • Poor gut health (though the results might be temporary)
  • Control calories
  • Needing to “change things up”
  • Having a plan to follow
  • Sleep problems
  • Weight problems
  • Fatigue problems


The Risks Of Time-Restricted Eating


It can extremely difficult to consume enough calories for an entire day in a short window of time.

Over time, undereating can harm thyroid function, harm immunity, cause nutrient deficiency, interfere with sleep, and wreck hormone production.

In time-restricted eating, it’s imperative that basic caloric requirements are met, long-term.

Appetite Suppression

The appetite has been shown to be reduced in time-restricted eating.

This is often celebrated as a major benefit, but it can be a danger, too.

Throughout the health world, there are many undernourished dieters, following many restrictive dietary plans, who also notice a diminished appetite.

A diminishing appetite can be seen as a real problem for health, a sign that the body is shutting down and going into “starvation mode.” This is a real concern when inadequate calories are being consumed each day.

The metabolism slows and slows to adapt to the lack of fuel — while the dieter raves about his/her lack of appetite and cravings.

This can be a dangerous sign, and a major reason I do not recommend most time-restricted diets.

People may have serious gut health problems that are indirectly addressed by eating less and fasting — but is undernourishment the only answer?

In the study above, the subjects were only followed for 5 weeks — a very short time to fully understand the long-term implications of a dietary practice.

Poor Sleep

Undernourishment can be very bad for sleep.

So can eating too late in the day, which can slow the metabolism and confuse the circadian rhythm.

On the other hand, beginning a fast too early in the evening can leave one quite hungry and unable to fall asleep at night. For many people, even a supper as early as 5pm can cause sleep to suffer — especially if a caloric deficit is occurring.

The body’s solution to extremely long fasts (and undereating) is for the metabolism to slow, which is not a good solution for long-term health.

Added Stress

While some enjoy having “rules to follow,” strict rules can add a lot of unnecessary stress for some people. Therefore, this approach may not be for everyone.

If you want to improve your insulin sensitivity, lose weight, sleep better, and curb your appetite, there are more logical and sustainable options. Extreme time-restricted eating is not the only choice.

No Proper Meal Times

The body doesn’t work very well when it grazes for much of the day, for several reasons: it’s bad for gut health and it ignores circadian rhythms controlling the digestive, endocrine, and adrenal systems.

For those longer feeding windows (such as a 12-hour feeding window), you shouldn’t “graze all day.” You should eat designated meals.

On the surface, feeding windows offer a step toward structure. Sometimes, that structure isn’t attainable, helpful, or even all that clear to begin with.

Underfeeding Almost Always Causes Overeating Later

It can be very difficult to eat enough calories while intermittent fasting.

In fact, a potent criticism maintains that many benefits from intermittent fasting are largely due to simply eating fewer calories.

Unfortunately, eating less is not a long-term strategy — especially if you’re undereating and not meeting your daily caloric requirements.

Undereating will always result in a rebound — days and even weeks of overeating to make up the difference. This becomes truer the sicker we are.

On any diet that fails to supply adequate calories two things are guaranteed to happen: a rebound (where weight lost is quickly regained) and a slowing of the metabolism.

Now, all of this can be avoided if you meet your daily caloric requirements. Again, that’s very difficult to do for many people.

“Skipping Breakfast”

Skipping breakfast is extremely common with an 8-hour window.

It usually results in a 12-8 feeding time: Lunch & dinner. (This typically includes lots of afternoon snacking, too).

While this isn’t a huge deal for most average people who just need to control caloric intake, it is still far from optimal. There’s actually a good bit of research suggesting that eating earlier in the day is better for all sorts of health metrics: weight, circadian rhythm, inflammation, and more.


The Best Way To Time Your Meals

The best meal timing for health is tried and true, old as the hills and, well, perhaps a bit boring.

But it works — in any situation, no matter your health goals or challenges.

Three Meals Per Day

To take advantage of the health benefits of time-restricted eating, look no further than our immediate ancestors: Our grandparents.

When did their generation eat? Oftentimes, their schedule looked something like this:

A traditional “three square meals” is actually close to a 12-hour window.

Eat Dinner As Early As You Like

The best feature of eating three square meals: You can nudge dinner earlier — creating a larger fasting window, overnite — while still sustainably achieving high-performance throughout the day. How? Simply finish dinner by 5PM or 6PM instead of 7PM.


3 Meals Is A Very, Very Solid Method

Benefits Of “Three Meals” Per Day

You Eat Early

Take advantage of the metabolism-boosting effects of a solid, early breakfast.

You Eat Often

The metabolism doesn’t slow due to extremely long fasting periods.

You Eat Enough

You aren’t trying to squeeze an entire day’s food into a small window, just so you don’t fall short on calories.

It’s Sustainable

You can eat this way the rest of your life. No gimmicks, it just works.

Eating shortly after waking is best for your metabolism and your circadian rhythm.

Eating dinner at 6:30PM is perfect for sleep.

  • You’ll have plenty of time for digestion to begin before bedtime.

No approach solves as many problems as well as “3 meals” (and its “12-hour feeding window”).



Experimentation is usually a good thing. Especially if you need “something different,” feeding windows can be a great way to change things up.

The main risk with diet experimentation is that you’ll learn bad habits, and keep them after the experiment is over. A major bad habit? Orthorexia — and it’s as common as air in health groups, these days.

For the long term, don’t forget that eating “three meals a day” — at proper timing — does the following:

  • Represents a solid “feeding window”
  • Enables good sleep
  • Promotes strong metabolism
  • Allows for a “fasting” period (both at night and in between meals — when you don’t snack)
Learn More:

Let’s Feel Better.

Discussion. Community. Thoughtful ideas. 6/mo.

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