GET $10, GIVE $10
Give your friends $10 off on their first order of $50+ and get $10 in points for each successful referral.
Get $10 Now

Keto Diet Basics

About Fasting & How to Use Fasting to Get into Ketosis

Published on: June 25, 2018

About Fasting & How to Use Fasting to Get into Ketosis

Restricting carbs is one way to get into ketosis. Another way is through fasting. However, there is a right and a there is a wrong way to fast for the sake of ketosis. Knowing the difference prevents potentially dangerous complications and will lead you to success in no time.
But how exactly do you do that? By following our tips of course. In this article, we explain how keto dieters use fasting to get into ketosis. We also explain what fasting is, what other benefits you get, and what makes it better than calorie restriction.

What Is Fasting?

Fasting is willingly abstaining from food and/or drink. It has been a part of cultural and religious practices for millennia across the globe. Nowadays, when talking about fasting, what most people are referring to is fasting as a dietary practice.
There are many different fasting methods, but the four most popular ones include:
  • Dry Fasting – This is an extreme type of fast where you go without both food and water for a couple of hours to a day. It has religious roots but some people use it for health purposes.
  • Water Fasting – Unlike dry fasting, water fasting allows for non-caloric liquids. It's much safer than dry fasting. The length of water fasting ranges from 8 hours to up to 3 days.
  • Partial Fasting – This type involves limiting or excluding certain foods. Most cleansing and mono diets are partial fasts.
  • Intermittent fasting– Currently the most popular method, intermittent fasting involves not eating for a period of time followed by eating within "feeding windows." It's a fasting method most commonly used in keto.
The goal of fasting is to reduce calorie intake. Keto dieters also use fasting to get into ketosis. Fasting also provides a range of health benefits. Most of these benefits come from eating fewer calories and include weight loss, greater longevity, and reduced oxidative stress. [1].

Fasting and Ketosis

Fasting to get into ketosis is quite popular among ketoers. It takes anywhere between 24 hours and 3 days for your body to enter ketosis when fasted. However, complete fasting is unnecessary and can even be dangerous for people with diabetes and chronic kidney diseases.
One study compared the timing of ketosis during fasting and on a keto diet [2]. The study concluded that both keto and fasting led to ketosis within a similar time frame – around 17-48 hours. That means that you don't really need fasting to get into ketosis, but it is helpful.
What many keto-ers do is use fasting alongside a keto diet. This enhances the diet’s efficiency and provides added health benefits. You'll enter ketosis sooner when combined with a fast. Fasting while on keto also reduces your risk of complications like hypoglycemia and severe electrolyte imbalances.
The most popular fasting method among keto dieters is intermittent fasting. Intermittent fasting is also gaining momentum in wellness and science communities. That's not surprising given how easy, convenient, and helpful it is.

Intermittent Fasting on Keto

Intermittent fasting (IF) shortens the time it takes to enter ketosis by a couple of hours and up to a day. This is important for keto dieters who want to shorten their keto flu. Besides that, the sooner you enter ketosis, the sooner you'll also reap its many benefits like increased energy and weight loss.
Another great thing about IF on keto is that you can tweak it to suit your needs. Here are some different IF approaches for you to consider:
  • Meal Skippin

Skip one or two meals in a day and eat the next meal as you usually would. Most people prefer skipping breakfast while others skip dinner.

  • Whole Day Fasts

Some dieters choose one day of the week to fast. When fasting for 24 hours or more, make sure to drink electrolyte-rich fluids to avoid dehydration and fatigue. Keto-ers suggest that it's best to choose days when you're busy for whole day fasts to keep your mind away from food.

  • Time-Restricted Feeding

You fast for a time period and eat within limited number of hours each day. Fasting and eating time frames are often referred to as fasting and eating windows. Dieters create these fasting/eating windows to suit their needs and refer to them by numbers such as 16/8 or 20/4.

Whichever way you choose to fast will for health and ketosis. It's really up to you to decide. Try to follow a fasting method that you are most comfortable with as this will ensure you're being consistent.

How Fasting Leads to Ketosis

When you fast, blood glucose and insulin levels fall. This stimulates the release of fat-burning hormones such as glucagon and adrenaline. These further stimulate the breakdown of fats called triglyceride stores in your fat tissue. Finally, when triglycerides reach your liver, they're used to generate energy or to make ketones. When ketone levels reach up to 7–8 mmol/L, you are officially in ketosis [3].
The ketogenic diet is an alternative to fasting. It also causes drops in glucose and insulin due to a low carb intake. But unlike fasting, you are allowed to eat high-fat foods and some amount of protein. These macronutrients don't impact blood glucose as much as carbs.
Another difference between keto and fasting is in the source of fat used to make ketones. When you fast, the only fat source available are your fat stores. On keto, that source also comes from the high-fat food you are eating. Whether or not keto will cause weight loss like fasting depends on the number of calories coming from your fat intake.

Is Fasting Better Than Reducing Calories?

Fasting is one way to reduce calories but is it better than, say, low-calorie diets? The short answer is yes. A 2016 systematic review found that fasting leads to greater weight loss than very-low-calorie diets [4]. Fasting is also easier to follow and spares muscle mass.
A growing body of research shows that calorie restriction, with or without fasting, provides benefits beyond weight loss [5]. These benefits include:
  • Diabetes Control

Fasting lowers blood glucose and balances out insulin production – both important when managing diabetes. Some studies also show that fasting improves insulin sensitivity in those with type II diabetes [6].

  • Muscle Strength

When combined with exercise, fasting preserves muscle strength as you age. Most people lose muscle mass as they grow older, and this is called sarcopenia. Fasting can help preserve your muscles through autophagy.

  • Heart Disease Prevention

Maintaining normal weight and restricting your intake of certain foods helps keep your cardiovascular system healthy. Fasting also reduces inflammation which is essential for heart and cardiovascular system health.

  • Cancer Prevention

Autophagy through fasting can also reduce your risk of cancer. That's because autophagy removes damaged cell proteins and other parts, replacing them with new, healthy components.

  • Overcoming Depression

There's also evidence that fasting is a natural antidepressant [7]. Fasting increases endorphin production. Endorphins are your brain's natural opioids, and like opioids, endorphins lead to feelings of euphoria. Ketones also protect the brain against oxidative stress and improve mitochondrial functioning, which can positively impact your mental health.

  • Mental Acuity

You'll often hear how keto diets boost mental acuity. The same goes true with fasting. The reason why you develop a sharp mind on both is duet to greater ketone levels in the brain.

  • Healthy Aging
Humans are built for periods without food. What's more, our bodies even thrive on occasional calorie restriction. That's because fasting gives our bodies time to rejuvenate through something called autophagy. It's your body's recycling system that research shows is upregulated when you fast [8]. Autophagy helps create new cells and increases longevity.

How to Use Fasting to Get into Ketosis

You can use one of the three fasting methods to get into ketosis that we mentioned earlier. Whichever one you choose, combine it with your usual keto diet for best results. Restricting carbs combined with fasting to get into ketosis will get you there quicker. Here's how to use fasting to get into ketosis:

Go in Head-First

Skip breakfast or even lunch and dinner and let your next meal be keto-based. Scrambled eggs with keto bread or an avocado dip are great for breaking your fast. This method will quickly deplete your glycogen stores. Glycogen is your body's sugar store and is found in the muscles and liver. It takes only 8-24 hours for these stores to completely run out when you fast.

Start With a Keto Breakfast

Alternatively, you could start with a keto breakfast such as almond flour muffins or bacon and eggs and skip your next meals. This way, you'll still be depriving your body of carbs and enhancing ketosis through subsequent meal skipping. It's an easier approach for most dieters and allows your body to produce ketones gradually.

Choose a Day

Start your week with keto meals and pick a day dedicated to fasting. It normally takes 1-3 days to get into ketosis. If you eat keto for the first three days, chances are you'll already be in ketosis. Instead, fast on the second or third day of your keto diet. This will help you avoid the keto flu through greater ketone production and utilization.

Water Fast

Dry fasting on keto is not suitable. That's because when you dry fast, you can't replenish your electrolytes. Electrolytes are compounds like potassium, magnesium, and sodium that conduct electrical signals between cells. Without them, you can develop lethargy, abnormal heart rhythms and other complications.

Use MCT Oil

MCT is short for medium-chain triglycerides. These are special types of fats that your body easily absorbs and uses for instant ketone production. MCT oil is the concentrated form of these triglycerides. Taking it before you start fasting helps reach ketosis earlier.

Word of Precaution

Fasting is safe for most people. But like all chances to your diet, problems can happen. Here are things you need to consider when fasting on a keto diet:


Even if you drink your fluids, fasting can leave you dehydrated. That's because once your glycogen stores get depleted, you lose water along with that glycogen. Another reason is the loss of water-retaining electrolytes like sodium. To prevent dehydration while fasting, always drink electrolyte-rich drinks, without sugar of course.


People at risk of hypoglycemia (diabetics) need to be careful about fasting. It's a good idea to combine daily fasting with keto diet, as in the case of intermittent fasting. Gradual reduction in carbs is also better than suddenly cutting down on carbs to 30 grams per day. This will allow your body to adjust, preventing hypoglycemic episodes.

Low Blood Pressure

Water fasting, in particular, increases the risk of orthostatic hypotension [9]. It's a fancy way of referring to a sudden drop in blood pressure when you stand up. This can leave you dizzy, lightheaded, and even cause fainting. Don't water fast for more than 12 hours to ovoid drops in blood pressure.
Also, those with gout, diabetes, kidney problems, and peptic ulcers need to be careful with fasting. It's best to go on short fasts and avoid water fasting if you suffer any chronic condition.


Fasting and the ketogenic diet lead to the same outcome – ketosis. However, keto dieters like to combine these two dietary approaches for faster ketosis and added health benefits. When combined with a keto diet, you can expect to enter ketosis a day or two earlier. You also reduce your risk of certain diseases and boost longevity.
The best way to fast on keto is intermittently. This method is proven to be safe and effective. The feeding and fasting windows in intermittent fasting are easy to adjust to meet your needs and lifestyle. But we suggest going for shorter fasting periods followed by longer feeding windows for safety.
Also, make sure to drink plenty of fluids and take your electrolytes when you fast. The keto diet has quite the diuretic effect in itself. This effect becomes even stronger when you fast. Losing water and electrolytes can aggravate the keto flu and even lead to complications like sudden drops in blood pressure.
We hope the tips and bits of knowledge given here helps you get though your keto fasts successfully. To learn more about fasting on keto, you can also read our articles here. Also, visit our FAQs section for more information.

Join Over 200,000 Fans

Sign up for the Kiss My Keto mailing list to get free keto resources, recipes, and strategies from the largest keto brand in the world.