May 28

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Keto Intermittent Fasting [The Definitive Guide 2020]

By Jeremy Stone

May 28, 2020

intermittent fasting, keto intermittent fasting

The major benefit of combining keto and intermittent fasting is increasing the amount of time your body is in ketosis.

Keto intermittent fasting helps your body to increase fat burning and in turn, may increase weight loss.

There are many resources available about intermittent fasting that offer general advice. You may have heard of terms like 16/8 intermittent fasting, or 5:2 diet.

These resources are a great start, but combining keto and intermittent fasting is normally limited to a paragraph here and there.

We really wanted to get specific on keto intermittent fasting.

As such we’ve created the definitive guide to keto intermittent fasting for 2020.

Our aim is to make this guide the most in depth resource available on combining the keto diet and intermittent fasting, leaving no question unanswered.

Let’s dive right in…

Can You Do Keto and Intermittent Fasting Together?

keto diet and intermittent fasting

Absolutely. Combining the keto diet and intermittent fasting is a very effective method of staying in ketosis and increasing weight loss.

Intermittent fasting is recommended when following the ketogenic diet.

Why? Because your body needs to burn through the carbs you have consumed (which are converted into glucose in your body), before starting to burn fats for energy.

If you have a period of time where you don’t consume any food at all, your body is likely to move through burning glucose into burning fats, or as more commonly known, ketosis. Fat burning helps to lose weight faster.

The other benefit of using fat for fuel is decreased hunger levels. When eating good quality fats on the ketogenic diet, this helps to keep you fuller for longer. This means that you naturally won’t want to eat as often.

In theory, keto intermittent fasting, should be easy.

Top Tip: Make sure you are fully adapted to the keto diet before introducing intermittent fasting. It will be much easier to not break your fast, fast for longer and remain in ketosis.

Types of Fasting

how to start fasting for weight loss

You’ve probably heard of intermittent fasting plans such as 16/8 method, 5:2 fasting diet plan and eat stop eat, just to name a few.

But, what do all these numbers mean? What is the best type of intermittent fasting for the keto diet? Is there such a thing as keto intermittent fasting?

Let’s take a look first at the different types of intermittent fasting…

16/8 Fasting

The 16/8 fasting method is probably the easiest type of fasting to stick to.

This is where you eat during an 8 hour window, and fast for the next 16 hours.

This type of fasting can be quite flexible, which is what makes it appealing.

For example, if you’re the type of person that can’t live without breakfast, then, eat breakfast. This will be the beginning of your 8 hour eating window.

If you ate breakfast at 8am, you could eat a light snack during the day, and dinner at 4pm. This would conclude your 8 hour eating period.

You would then fast for the next 16 hours.

Another scenario here is if you are the type of person who never eats breakfast, start your eating schedule at morning tea or lunch instead.

For example, first meal at 11am, light keto friendly snacks throughout the day and dinner at 7pm. You would then fast until 11am the next day, and repeat the process.

This is a great way to get started with keto intermittent fasting.

12 Hour Fast

12 hour fasting is a variation on the 16/8 fasting method, where you eat during a 12 hour period and fast for the following 12 hours.

If you are just getting started with keto intermittent fasting, this is a good way to ease yourself in.

As your body (and mind) gets used to going for longer periods of time without food, you can extend your fasting period.

18 Hour Fast

Just like we have described above, the 18 hour fast is another method of fasting. This is where you eat during a 6 hour window, and fast for the following 18 hours.

If you have worked your way up to 16 hour fasting and are finding this easy, or have had a stall with your weight loss, you may want to push yourself a little further to try an 18 hour fast.

If you’re getting started with keto intermittent fasting however, we don’t recommend you start with an 18 hour fast.

What is important to remember is that the ketogenic diet is a lifestyle, as is keto intermittent fasting.

Making changes to your diet and lifestyle is hard enough in the beginning, so if you’ve never fasted before, start with a smaller window.

You don’t need to take an all or nothing approach to the keto diet or intermittent fasting. If you make it too hard on yourself in the beginning, what would be the likeliness of you maintaining this lifestyle long term? Go easy on yourself.

The 5:2 Diet

The 5:2 diet is based on eating a normal diet 5 days a week, and limiting calorie intake to 500 calories for women and 600 calories for men on 2 days per week.

This should not be 2 consecutive days per week. Leave at least a one day gap between days.

To adapt the 5:2 diet for keto, you could eat a standard ketogenic diet for the 5 days. On the two calorie restricted days, you would also need to ensure you also continued with carb restrictions.

For example, men should consume 600 calories or less AND less than 20 grams of net carbs on the restricted days.

Eat Stop Eat Fasting

The eat stop eat method of fasting is rather advanced. Using this fasting method, you eat one meal only during a 24 hour period. For example, if you eat lunch on Tuesday, your next meal would be lunch on Wednesday.

This type of fasting is certainly a shock to the body and not recommended as a starting point.

Build up to the eat stop eat fasting method over time, by using other fasting techniques with shorter fasting periods until you are used to fasting.

The Warrior Diet

The Warrior Diet is based on a 20/4 fasting method. That is, you eat during a 4 hour feeding period. Then fast for the next 20 hours.

As the name suggests, the Warrior Diet is also about limiting what food is eaten during the 4 hour period. This diet suggests eating some fruits and vegetables only.

The problem with the Warrior Diet for keto is it lacks the fat needed for ketosis and hunger control.

What is 23/1 Intermittent Fasting Keto?

The 23/1 fasting method is much the same as the eat stop eat method. You eat during one hour of a day, then fast for the next 23 hours.

When you build up to a fasting method like the 23/1 fast, make sure the meal you do eat is full of high quality fats and nutrients to help keep you full for as long as possible into the fast.

It is important to keep well hydrated during a fast. Drinking fluids also helps to keep hunger at bay. We’ll discuss more about what you can drink during intermittent fasting shortly…

OMAD Keto

OMAD (one meal a day) keto is very similar to the 23/1 intermittent fasting above, or the eat stop eat fasting method.

As the name suggests, you eat one keto meal a day, whilst fasting for the rest.

This is a popular fasting technique for those who have been on the keto diet for longer periods of time, or are experienced with keto intermittent fasting.

This is definitely not a technique you want to start with if you have never fasted before.

Is Intermittent Fasting Safe?

Intermittent fasting is generally regarded as safe for most people, whether following the ketogenic diet or not.

There are certain people who should not fast. Children under 18 years, pregnant women and diabetics (particularly insulin dependent) are not recommended for fasting.

Furthermore, any person with any other health or medical condition, including mental health conditions should consult their health practitioner before fasting. This includes any history of eating disorders.

How Long Should You Intermittent Fast on Keto?

low carb and intermittent fasting

Like our answer to the question below on how much weight you could lose with keto intermittent fasting, how long you choose to add intermittent fasting into your keto diet is up to you.

There is no literature that we were able to find that said you must not fast for more than a certain number of weeks or months.

Fasting is something that has been practiced across many cultures for many centuries, even before Christ.

Our opinion on keto intermittent fasting is to use common sense. Ask yourself questions like these:

  • How are you feeling with keto intermittent fasting?
  • Have you been able to increase your fasting periods?
  • Are you still losing weight?
  • How are your vitamin and nutrient levels?
  • Do I feel I can keep going with the keto diet and intermittent fasting?

Each person is unique and will handle dietary and lifestyle changes differently. Do what feels comfortable to you. If in doubt, seek medical advice.

How Much Weight Can You Lose with Keto Intermittent Fasting?

how to start intermittent fasting

There is no hard and fast rule when it comes to weight loss on the keto diet and intermittent fasting.

The amount of weight you can lose and how quickly you lose the weight will depend on how much weight you have to lose in the first place.

If you are new to the ketogenic diet, your initial weight loss will be water loss. This is generally up to 10 pounds of weight loss and happens in the first one to two weeks on the keto diet.

By the end of the first month on the keto diet you should consistently be in nutritional ketosis and your weight loss is likely to be less than you experienced in the first two weeks.

Maintaining a ketogenic diet over the coming months should see approximate weight loss of 2 pounds per week. This is an average amount only and could be more or could be less.

Please keep in mind you are an individual. Slower weight loss is also attributed to a slower metabolism. Age could be a contributing factor here also.

We recommend waiting until your body has adapted to nutritional ketosis before adding in intermittent fasting. Wait until you achieve that slow, consistent weight loss.

Alternatively, if you have been losing weight with the keto diet and hit a plateau or stall, keto intermittent fasting can be the kick start back into weight loss your body needs.

Intermittent Fasting Tips

intermittent fasting timeline

Here are our top 6 tips to succeed with keto intermittent fasting:

Stick to the Keto Diet First

Get comfortable with the ketogenic diet and get your body used to being in ketosis before you add in intermittent fasting.

intermittent fasting meal ideas

If you have ever heard of the keto flu (not really a flu, just a carbohydrate/sugar withdrawal) it can make you feel pretty lousy at times.

You can feel fatigued, headachy and irritable – just like you would feel if you actually had the flu.

Make sure your body has adapted to the keto lifestyle, as adding in intermittent fasting will be another shock to the system.

Which leads us to our next point…

Start Slowly with Keto Intermittent Fasting

Don’t start by trying to complete a 24 hour fast.

A great analogy here is to think like a marathon runner. A marathon runner will train shorter distances first, then build up to longer distances. In short, they will run a half marathon before a full marathon.

fasting to induce ketosis

The same can be said for introducing yourself to keto intermittent fasting.

Start by fasting one meal only. You don’t even need to put a time frame on it if you don’t want to. Try eating dinner a little earlier one evening, and seeing if you can go an extra hour of two in the morning before eating.

Take keto intermittent fasting slowly and build up over time. This will give your body time to adjust.

Drink Water During Keto Intermittent Fasting

water intermittent fasting

It is incredibly important to remain hydrated every day. Just because you are not consuming food during keto intermittent fasting, doesn’t mean you shouldn’t drink fluids.

Water is essential to maintain health and avoid dehydration. Water can also help to keep hunger pangs at bay and help to flush any toxins out of your body.

Coffee is also very beneficial during keto intermittent fasting. You may have heard of keto coffee bombs or bulletproof coffee?

These types of high fat coffees are incredibly popular when fasting in conjunction with the keto diet. This doesn’t mean however, you can hop down to your local cafe to replace food with a creamy caramel latte.

Coffee on the keto diet should be black and free from sugar or syrups. We’ll cover what drinks you can have when keto intermittent fasting a little later in this post, including how to make a bulletproof coffee.

Fasting and Working Out

We are never going to tell you not to exercise, but, if you are new to keto intermittent fasting, take your workout a little easier to begin with.

exercise during fasting

Try switching up your routine and going for a walk outdoors (somewhere where you are not tempted by cafes and ice creams of course!).

Practice yoga, meditation and stretching exercises, rather than that high cardio workout you would normally do.

We suggest this for beginners with keto intermittent fasting so you don’t overwork your body and end up exhausted. You want to make the transition into keto intermittent fasting as easy as possible.

Add in a Keto Supplement

We are big fans of keto supplements to help support ketosis and regular users of both exogenous ketones and MCT oil to support the ketogenic lifestyle.

onnit total human
Onnit Total Human Day & Night Supplements

There are also multivitamins designed for the ketogenic lifestyle which are great support during keto intermittent fasting, when you are not taking in nutrients from whole foods.

Having said that, keto supplements should never be a replacement for nutrients obtained via whole foods on the keto diet.

It is important that you eat quality foods on your non fasting days to keep your body filled with the essential vitamins and minerals it needs.

Which brings us to our last point…

Don’t Feast After the Famine

You might be tempted to eat a large meal after fasting. Don’t do this.

what to eat after a fast

Eating too much protein, or too many calories can hinder your weight loss goals on the keto diet. Don’t be tempted to over indulge in fat bombs or more food than you would normally consume.

You may also find that you aren’t able to eat the same volume of food that you could prior to intermittent fasting. That is ok.

The ketogenic diet and intermittent fasting is all about quality over quantity. Eat healthy fats, moderate protein and low carb like you would on your non fasting days and you will be fine.

What Can You Drink During Intermittent Fasting Keto?

what to drink intermittent fasting

Water is the absolute healthiest choice to drink during keto intermittent fasting.

You can however, drink tea, coffee, sparkling water, herbal teas and other low carb drinks during intermittent fasting.

It is really important to continue drinking fluids whilst intermittent fasting. You can easily become dehydrated if not careful.

What to Drink During Shorter Fasts

Shorter fasts, up to 16 hours, you should stick with drinking plain water, carbonated water, black tea, herbal teas and coffee.

Make sure that you do not add any milks or sugars to the drinks you are consuming. Also check any herbal teas to ensure there are no added sugars or sweeteners.

What to Drink During Longer Fasts

For fasts that last above 16-18 hours, try adding in bone both as a drink.

bone broth intermittent fasting

Any time that you consume calories during your fast will cause a slight spike in insulin levels. This will happen with consuming bone broth.

The benefit of bone broth however, is the added boost of minerals, electrolytes and amino acids.

Drinking bone broth during keto intermittent fasting will allow you to fast for longer periods of time.

MCT Oil During Fasting

MCT Oil is often added to coffee during keto intermittint fasting.

Our in depth blog post on how to use MCT Oil while intermittent fasting covers everything you need to know.

Avoid Alcohol

Whilst you can have alcohol on the keto diet, we do not recommend drinking alcohol during a fast.

Alcohol is dehydrating to the body. You are already prone to dehydration during keto intermittent fasting as you are not absorbing water from food.

Can I Drink Bulletproof Coffee While Fasting?

Technically, bulletproof coffee will break a fast. This is because of the calories in the butter, ghee, coconut oil and MCT oil (or whichever combination of those you use in your coffee).

MCT Oil however, is a popular choice to add to coffee whilst keto intermittent fasting to add extra fat to your diet. This helps to fuel your body and brain and help you remain in ketosis.

MCT Oil is converted into ketones by the body and healthy fats such as butter and ghee don’t cause insulin spikes.

Therefore, you should still remain in ketosis and continue to lose weight, even if you drink bulletproof coffee whilst intermittent fasting.

A standard bulletproof coffee recipe is:

  • One cup of black coffee
  • One tablespoon of ghee or unsalted butter (don’t be tempted to use salted butter here – tastes awful)
  • One tablespoon of MCT Oil or coconut oil (C8 MCT Oil is our preferred choice)

You will need an emulsion blender to mix the fats and water/coffee together. The result is a creamy, unsweetened coffee.

For more tips on making bulletproof coffee, take a look at our post on keto coffee bombs.

What to Eat While Fasting

what to eat while fasting

During the feeding period, you should try and stick to the ketogenic diet as much as possible. Use fat for fuel and try not to be tempted to consume excess carbs.

Some resources say you can eat anything you want during your feeding window, as long as you stick to the fasting period.

Two different keto intermittent fasting books we have read recommend eating potatoes. A third book recommended legumes, and even provided a recipe.

Since when do you eat any kind of potato, or legumes on the keto diet?

If your desired outcome of keto intermittent fasting is weight loss, why stuff yourself full of carbs and fat during the eating period?

Your body will have to burn through the carbs, before burning through the fat.

Imagine how much more fat burning your body could achieve during a fast if you stuck to a standard ketogenic diet during your eating periods.

Final Thoughts

Keto intermittent fasting is an effective method of achieving ketosis and assisting with weight loss.

It is important to make healthy keto friendly food choices during your eating window. Eating with high fat foods for keto is important to be able to sustain long periods of fasting.

You should listen to your body when intermittent fasting and get to know what is right for you.

If you are struggling with hunger, drink water first before breaking your fast. Also, ask yourself… am I really hungry? Could this be psychological? Often it is, until you get used to fasting.

Weight loss should be a slow process. After all, you didn’t gain 50 pounds overnight. Don’t expect to lose it overnight either.

If at any stage you feel unwell or in pain be sure to stop fasting and seek medical attention.

Jeremy Stone

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