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The Complete Guide to Intermittent Fasting 16/8


Intermittent fasting is an effective fasting method with research-backed health benefits, including healthy weight loss, better cognitive function, and lower inflammation. It has become a popular tool for improving overall health and reaching nutrition and fitness goals. The most well-known, approachable, and sustainable method is intermittent fasting 16/8.


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What Is Intermittent Fasting 16/8?

intermittent fasting 16/8

Intermittent fasting (IF), also known as time-restricted feeding, means eating within a specific daily window of time (feeding period) and fasting outside of that window (fasting period).

There are several different types of intermittent fasting, but the 16/8 method is the most popular because it’s the easiest.

Doing an 16/8 intermittent fast means that you fast for 16 hours and eat only within an eight-hour window throughout the day, such as from noon to 8 p.m.

The easiest approach is to skip breakfast and have your first meal later in the day. For example, if you finish dinner by 8 p.m., you wouldn’t eat again until midday the next day.

Keep in mind 16/8 intermittent fasting is only one approach. The windows can vary based on what works for you. While some people might only eat within the same eight hours a day, others might only eat within a six-hour window (18/6) or four-hour window (20/4).

How the 16/8 Intermittent Fasting Diet Works

Like exercise, restricting calories is a helpful metabolic stressor. Eating within a certain time frame pushes your body in a different metabolic direction than if you were eating all the time.

Intermittent fasting can cause autophagy, which is a crucial defense mechanism against malignancy, infection, and neurodegenerative diseases. It’s basically your body’s way of cleaning out cells that aren’t performing at their best.

Research finds short-term fasting is an effective way of starting neuronal autophagy (cleaning up brain cells that aren’t doing well), therefore protecting your brain against neurodegenerative diseases[*].

Intermittent fasting also triggers a beneficial metabolic reaction that includes[*]:

  • A decrease in inflammatory markers
  • Reduced blood glucose levels and insulin
  • An increase in the neurotrophin BDNF

These are powerful changes that can lead to several health improvements.

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Health Benefits of 16/8 Intermittent Fasting

Adopting this eating style may seem difficult if you’ve never tried it before, but once you get used to it, it’s easy to follow. Plus, the research-backed benefits make it an excellent tool to improve your health.

Intermittent fasting 16/8 has been researched for its ability to improve multiple aspects of your health.


#1: Fat Loss

Intermittent fasting can help both healthy and overweight adults lose weight and body fat effectively. Human intervention trials have consistently found IF significantly reduces weight[*] as your body is in a fat-burning mode more often.

In almost any type of fasting, losing weight is a natural byproduct because you’re consuming fewer calories.

#2: Improved Cognitive Function

Another perk of intermittent fasting is that it can improve brain function, boost focus, and get rid of brain fog.

Studies find that restricting calories moderately can[*][*]:

  • Protect the brain by reducing oxidative damage to cellular proteins, lipids, and nucleic acids
  • Elevate levels of BDNF, an important neurotrophin that is needed for synaptic plasticity

#3: Lower Inflammation

IF is also great for your brain and might help you think clearer. Intermittent fasting, or restricting calories, also lowers markers of inflammation, which in turn aids cognitive function and protects your brain health[*].

#4: Lower Blood Pressure

Research finds intermittent fasting can help reduce blood pressure. According to a recent study, people that restricted eating habits to a smaller period of time lost weight from a lower calorie intake, which then helped them lower their blood pressure[*].

#5: Blood Sugar Control

Intermittent fasting is also an excellent tool for blood sugar regulation. Research has found that IF reduces blood sugar, insulin, and improves insulin sensitivity[*].

#6: Better Metabolic Health

Due to the different beneficial effects of intermittent fasting on health markers, it supports overall metabolic health.

Research finds intermittent fasting can improve metabolic profiles and reduce the risk of obesity and obesity-related conditions such as non-alcoholic fatty liver disease, and chronic diseases such as diabetes and cancer[*].


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#7: Longevity

The positive effects IF can have on your metabolic health, inflammatory markers, and blood sugar levels may contribute to a longer lifespan and healthy aging.

Even though human trials are still needed to measure IF’s impact on longevity, multiple animal studies show calorie restriction results in an increased lifespan[*].

Another way intermittent fasting can improve your health is by facilitating ketosis.

How to Do Intermittent Fasting 16/8

intermittent fasting 16/8

To do intermittent fasting correctly and reap all the health benefits, here’s what to do:

  • Pick your fasting window: Choose what the hours of fasting will be. The easiest approach is to have an early dinner and skip your morning breakfast. For example, eating only from 1 p.m. to 9 p.m.
  • Have healthy meals during your eating window: A bad diet during your eating window can offset the metabolic benefits of intermittent fasting, so stick to nutritious whole foods. Here’s a list of the best keto-friendly foods to eat.
  • Eat fatty, satisfying meals: While you don’t need to be keto to try intermittent fasting, eating fatty foods will make it a lot easier and sustainable. Keto foods are healthy and satisfying, so you won’t be hungry during your fasting window. Practice smart snacking and you’ll do great.

Intermittent Fasting and Ketosis

One of the best things about fasting is that it can help you get into ketosis faster.

The two are related for a few reasons:

  1. For your body to get into ketosis, you must be fasting in some sense — either by not eating any food at all or by keeping carbs extremely low. When you’re in ketosis, it means your body is breaking down fat for energy.
  2. Intermittent fasting helps deplete your glucose stores at a faster rate, which speeds up the process of running on fat.
  3. Many people who start a ketogenic diet begin by fasting to enter ketosis more quickly.

So, is intermittent fasting 16/8 guaranteed to get you into ketosis? No, but it can help get you there if you do it along with a keto diet.

Intermittent Fasting 16/8 and the Keto Diet

intermittent fasting 16/8

There are three compelling reasons to combine intermittent fasting with a keto diet.

#1: Intermittent Fasting Is Not Enough to Keep You in Ketosis

The 16/8 fasting window may not be enough to get you into or keep you in ketosis. Even if you do end up in ketosis, if you continue to eat a diet with even a moderate amount of carbs it’ll probably kick you out of ketosis each time.

This can result in unpleasant side effects such as the keto flu and being overly hungry each time you start fasting again.

#2: The Keto Diet Makes Fasting Easier

Eating a ketogenic diet allows your body to become keto adapted (running on fat and not depending mainly on glucose).

This makes intermittent fasting much more comfortable because there’s no switching between glucose and ketones, thus eliminating the feeling of needing to eat every few hours.

#3: The Ketogenic Diet Keeps You Satisfied

Another great perk of the keto diet is its high level of satiety.

Not only does ketosis itself tend to stifle hunger, but the high level of healthy fat in the keto diet also makes it much easier to stay satisfied in a fasted state and eliminates those intense feelings of hunger and cravings throughout the day.

This is perfect for someone doing intermittent fasting.

How to Get Into Ketosis Using the 16/8 Method

While 16/8 intermittent fasting itself is not the only way to get into ketosis, it’s a good start.

To get into ketosis, the best way is to combine a healthy ketogenic diet with intermittent fasting. Taking exogenous ketones can also help with the transition period and reduce side effects.

Concerns About 16/8 Fasting

Intermittent fasting, especially the 16/8 approach, is completely safe and beneficial. Contrary to common belief, moderate calorie restriction is a healthy practice that improves your metabolic health.

However, if you’re using it to get into ketosis, it might not be enough to get you there. If your fasting goal is to enter ketosis, you also need to follow a keto diet.

The Bottom Line on Intermittent Fasting 16/8

intermittent fasting 16/8

Intermittent fasting is a safe and powerful tool for improving your health. To recap:


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  • The 16/8 intermittent fasting approach means you fast for 16 hours and eat only in an eight-hour window.
  • Fasting triggers autophagy, which is needed for healthy metabolism.
  • IF has plenty of research-backed health benefits including better brain function, lower blood sugar levels, and lower inflammation.
  • Fasting can be a great way to get into ketosis, but it’s not the only way.
  • If you want to use fasting for ketosis, it’s ideal if you do it while following a keto diet.


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