Ketosis vs Intermittent Fasting

Ketosis and intermittent fasting are topics that often fall into the same types of conversations. That being said, they do have differences that can lead you to wonder if one’s better than the other or how both can fit into your life. We can help you there!

We’ll be comparing ketosis vs. intermittent fasting — starting with a summary of each, then seeing what they have in common and how they differ.

What is Ketosis?

In short, ketosis is the process where the body burns ketone bodies for energy. With a regular type, the body’s primary source of energy is glucose, which comes from eating carbohydrates like bread, sugars, grains, fruit, or beans and legumes.

The carbohydrates from these foods are either used as glucose by the body immediately or stored as glycogen to be used later. However, if the body has a low supply of glucose, it must turn to something else for fuel. In the case of ketosis, that’s fat.

A ketogenic diet, which is high-fat, moderate-protein, and very-low-carb, will cause the body to break down fat instead of carbs for energy. When this happens, the follow ketone bodies are formed:

There are many benefits of putting the body into a state of ketosis, the most popular being weight loss, which we’ll examine first.

Ketosis Weight Loss Benefits

Ketosis helps weight/fat loss for the following reasons:

weight loss in ketosis

Other health benefits of ketosis include:

  • Studies show ketosis can help regulate hormones [1] that affect weight gain, such as cholecystokinin (or CCK), which can reduce appetite by stimulating the digestion of fat and protein and reducing emptying of the stomach. Ketosis can help raise levels of CCK when you lose weight too, at a time when CCK levels can be lower.
  • A reduction in risk factors for heart disease and improved triglycerides and cholesterol [2].
  • Elimination of diseases like type II diabetes [3] that are related to blood sugar.
  • Prevention of seizures in those with epilepsy, especially children.
  • Less inflammation [4] of the skin.

What is Intermittent Fasting?

Intermittent fasting involves only eating within a certain window of time, usually between 6-8 hours each day. You’re still eating like you would during any day, but only in between that set time span. Intermittent fasting itself doesn’t involve any specific diet, but rather a dieting pattern.

For most people, this means skipping breakfast and beginning eating later in the day, for example, between 12pm and 8pm.

We’re used to being told to always eat breakfast and to eat smaller meals all throughout the day if you want to be healthy and at a healthy weight. However, we’re not learning this might not be that case and that intermittent fasting actually has many benefits.

Fasting is nothing new when it comes to the body and being human. Our ancestors didn’t have easy and immediate access to food like we do today, so their bodies went through regular periods of fasting until they could find their next source of food.

Intermittent Fasting Weight Loss Benefits

Like with a ketogenic diet, fasting depletes your body of readily available glucose and stored glycogen, causing it to turn to your fat stores for energy.

Plus, only eating within a certain period of time, even if you’re still trying to eat the same amount of food, is bound to decrease the overall caloric intake for most people. This makes it a handy tool for weight loss while also giving your body a break from digesting constantly.

Other Benefits of Intermittent Fasting

Another benefit of intermittent fasting is that it can just simplify things. You’re spending less time preparing and stressing about meals, for one. You also have more opportunities to be efficient at work because you’re only having to stop 2-3 times at most to eat.

Intermittent fasting might even have protective properties against diseases like Alzheimer’s [5], improve short- and long-term memory [6], and increases the protein known as brain-derived neurotrophic factor (BDNF), which protects the brain against damage and death of cells.

You can read more about details about the benefits of fasting here.

Ketosis Vs Intermittent Fasting

Now, let’s cover some of the main reasons ketosis and intermittent fasting are the same and also how they differ from one another:

Ketosis vs Intermittent Fasting: Similarities

Basically, ketosis is a result of intermittent fasting. When you fast, it shifts your body into a metabolic state of nutritional ketosis — which could be why ketosis and intermittent fasting have many of the same benefits.

Just like with the ketogenic diet, intermittent fasting involves periods of “starving” the body of something, whether it be all food or just carbs. Also, getting into ketosis generally happens much quicker when fasting.

Ketosis vs Intermittent Fasting: Differences

One involves eating food and the other doesn’t (at least, not for certain periods of time). You can be eat throughout the day and still stay in ketosis on the ketogenic diet, while intermittent fasting involves refraining from food completely for certain periods of time

Also, ketosis is the goal of the ketogenic diet, while intermittent fasting itself is not a diet — and just because you practice it doesn’t mean your goal is necessarily to get into ketosis. Some people simply do intermittent fasting to eat less calories over the course of a day or avoid eating late at night. On the flip side of that, someone might do the ketogenic diet for more than just the weight loss benefits.

Take Home Message

When you look at ketosis vs intermittent fasting, you’ll see that that one can be a great complement to the other. Both also have tremendous benefits for health and weight loss, and that likely has a lot to do with the fasting that results in ketosis.

Sources cited:

  1. Chearskul, S., E. Delbridge, A. Shulkes, J. Proietto, and A. Kriketos. “Effect of Weight Loss and Ketosis on Postprandial Cholecystokinin and Free Fatty Acid Concentrations.” The American Journal of Clinical Nutrition 87.5 (2008): 1238-248. Web. 19 May 2017.
  2. Paoli, A., A. Rubini, J. S. Volek, and K. A. Grimaldi. “Beyond Weight Loss: A Review of the Therapeutic Uses of Very-low-carbohydrate (ketogenic) Diets.” European Journal of Clinical Nutrition 67.8 (2013): 789-96. Web. 19 May 2017.
  3. Dashti, Hussein M., Thazhumpal C. Mathew, Mousa Khadada, Mahdi Al-Mousawi, Husain Talib, Sami K. Asfar, Abdulla I. Behbahani, and Naji S. Al-Zaid. “Beneficial Effects of Ketogenic Diet in Obese Diabetic Subjects.” Molecular and Cellular Biochemistry 302.1-2 (2007): 249-56. Web. 19 May 2017.
  4. Paoli, A., K. Grimaldi, L. Toniolo, M. Canato, A. Bianco, and A. Fratter. “Nutrition and Acne: Therapeutic Potential of Ketogenic Diets.” Skin Pharmacology and Physiology 25.3 (2012): 111-17. Web. 19 May 2017.
  5. Wolfe, Devin M. et al. “Autophagy Failure in Alzheimer’s Disease and the Role of Defective Lysosomal Acidification.” The European journal of neuroscience 37.12 (2013): 1949–1961. PMC. Web. 30 Jan. 2017
  6. Brandhorst, Sebastian et al. “A Periodic Diet That Mimics Fasting Promotes Multi-System Regeneration, Enhanced Cognitive Performance and Healthspan.” Cell metabolism 22.1 (2015): 86–99. PMC. Web. 25 Jan. 2017.

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Responses (23)

  1. Okay so what if you followed the intermittent fasting ‘example’ schedule of eating 12-8pm (or any 8 hr window) and the diet you followed during that time period was Ketogenic, so combining both methods?

  2. I’m a diabetic and today my glucose level is 245. I’m wondering if I can still go into ketosis with my blood sugar at 245. I am weaning off my insulin in hopes of reversing my diabetes through either a ketogenic diet or intermittent fasting. Your help is appreciated.

  3. So when does ketosis really begin, do you know? I have done countless hours of research on this, and I find sources that say ketosis begins after 6 to 8 hours of fasting, and other sources say it begins after three days of fasting for men. That is a huge discrepancy. Does anyone have any real idea?

  4. I have been following the ketogenic lifestyle for 9 months and have begun Intermittent fasting 23/1 for two weeks. Surprisingly I do not feel hungry and feel compelled to see if I can fast further to 48 hours and see what happens. My glucose level is 54 and my ketones are just 1.1.

    I am drinking water and chaga tea only. Will I be breaking the fast if I take e-lyte sport electrolyte concentrate to replenish my electrolytes?

  5. It’s very individual, you have to see for yourself. It all depends on how much glycogen do you have stored in your body.

  6. Not to sound too ignorant after reading all this but if I’m trying to adhere to a ketogenic diet then fasting should get me there quicker, correct? Once you are in ketosis for a long period you no longer need to fast? Is the 16/8 only for fasting or do many on a ketogenic diet still adhere to this type of schedule?

  7. Hey Sam, no ignorance at all! All questions welcome :). It all depends on your goals here and how you feel. Many people find that they are less hungry when following a ketogenic lifestyle and being in ketosis so they end up fasting without even thinking about it. For example, I “fat fast” during the week by only having coffee with mct powder in the morning and then lunch around 2 p.m.. On weekends I like to enjoy brunch so I don’t usually fast then. It all depends on what works for your lifestyle and what your goals are!

  8. Sorry Christine it might be just me but to me this sounds like you have an eating disorder and need help.

  9. I have just started intermediate fasting, 16/8, for a week now and I feel great. I am curious if I can implement a ketones supplement (like the Perfect Keto) into this, and if so, is it something I would add into the 8 hour eating time or can/should it be used during the fasting time?

  10. Josh, you can definitely implement the ketone supplement to help you during or fast or as another source of fuel during your eating window.

  11. I wonder, can I be ketonic when on a 6 hours eatingwindow while eating some carbs( 2 p of fruit) in this window?

  12. That is the beauty of keto diet. This let’s you know that you have converted over to a fat burner

  13. Sugar of any amount would break the fast. So far only water, some herbal teas and black coffee are the only things known to not break a fast. Products such as bullet proof coffee are keto diet friendly, but definitely not fasting friendly.

  14. Bone broth contains calories and will cause a digestive reaction, which would break the fast. However water, black coffee and most tea (nothing added) would be fine.

  15. Your body will fully switch to “fasting” ketosis after about 72 hours of no food. The same can be said of the lower level ketosis that is obtained via the keto diet as long as you are keeping the carbs under 20 grams a day during those three days and using exercise to burn off excess glucose stores. What you read about online in terms of 6 to 8 hours after eating is talking about the body the fact that digestion, depending on what and how much you eat, takes about 8 to 12 hours. After digestion is finished the body will begin the process of ketosis and after 72 hours glucose levels will continue to drop while ketone levels will rise. So in short, to be fully in a state of ketosis will take about 72 hours, maybe less or more depending on each person’s ability to switch. Keto adapted individuals can make the switch more easily than those who are not.

  16. I’ve been eating within a 4-5 window for the past two months and not only have I lost about 15 pounds without really needing it but I have really noticed a huge difference in body composition, I’m much leaner and toned then I have been before at the same weight. I don’t have many restrictions for my diet except no processed foods and low sugar. During my fast I only drink water, flat and sparkling with no flavor and black coffee. I honestly love eating this way, it’s so easy and I’m saving myself some money on food.

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