If you are not new to the nutrition space, you’ve likely heard of two nutritional concepts before:

  1. the keto diet
  2. intermittent fasting

What’s becoming increasingly popular, however, is people putting these two diets together and fasting while on keto.

Is this a good idea?

It would seem to be a wise decision since one of the key highlights of the keto diet is the ultimate appetite control it brings – which is clearly perfect for any intermittent fasting protocol.

But there are some drawbacks to fasting – some dangers if you will, that you do need to be aware of.

This shouldn’t turn you off from fasting entirely, but it definitely does need to be addressed if you are going to go forward with it while doing the keto diet in the future.

Let’s go over what you need to know.

What Is Fasting?

Most of us know what fasting is – going without food – but there are many ways to fast while on a diet plan.

Obviously you cannot fast indefinitely, as your body does need food in order to survive. But you can structure your diet to include periods of fasting within the eating windows you allow yourself.

You may use an intermittent fasting approach where you fast every day for 12-16 hours depending on your preference. On this model, you’ll stop eating after breakfast and then break the fast at lunch or just after.

Or, you may fast every other day, fasting for an entire 24 hour period. This is often referred to as Eat Stop Eat fasting so you eat for 24 hours, fast for the next 24 hours and so on.

Some people may only fast for one or two days a week and leave it at that, while others prefer doing it throughout the whole week.

Benefits Of Fasting

What benefits come with fasting?

There are many reasons why people choose to carry this out. Some of these include:

  • Enhanced glucose sensitivity [1].

Fasting can help your body become more responsive to carbohydrates, thus keeping you leaner in the long run and preventing diabetes.

If you plan to use the targeted keto diet, where you do eat carbs once per day prior to your workout sessions, this will help ensure your body handles those carbs as best as possible.

  • Reduced cholesterol levels.

Which can help promote better overall heart health and lower your risk factor for heart disease. [2]

  • Improved mental focus and clarity.

When you fast for an extended period of time, your body releases endorphins that can increase your focus and alertness, making you more productive throughout the day. [3]

  • Enhanced levels of growth hormone.

Which help keep you leaner, assist with maintaining muscle mass, and may help to blunt the process of aging. [4]

  • Improved energy levels.

Many people on intermittent fasting protocols report having a seemingly endless amount of energy. You would think it would be the opposite with no food coming in, but that isn’t the case.

  • Maximum appetite suppression.

Once your body adapts to fasting, you won’t be experiencing much hunger.

So as you can see, there is quite the line-up of benefits to be had.

Many people go on intermittent fasting as a means of saving time as well. If you aren’t having to stop and eat food multiple times per day, this frees up time to be productive. Since you’ll be fasting for the majority of the day (morning until early afternoon), this allows you to relax and enjoy heartier meals in the evening.

Especially if you are dieting, you might find it easier to plan out meals if you have larger meals, say 600-700 meals and eat just two or three a day versus having tiny meals of 300 calories each but eating six times per day.

The Dangers When Fasting On Keto

Now that we’ve covered the benefits of fasting while on keto, it’s time to talk about the drawbacks.

There are some precautions you do need to take. By making yourself aware of them, you can ensure that you proceed to do the intermittent fasting diet safely.

  • You could be at risk of an electrolyte imbalance.

When you are fasting, if you are not taking in any fluids either, you may find that you start to feel light headed or dizzy. This can be due to a lack of sodium and/or potassium coming in, which are two key electrolytes that keep your body regulated. Dry fasting is not for the inexperienced and it’s a smarter move to allow fluids and include non-calorie electrolyte replacement beverages when necessary

  • Your blood sugar levels may drop.

If you are someone who is diabetic or even prediabetic and needs to watch your blood sugar levels carefully, you may want to consider bypassing an intermittent fasting protocol. Keeping a steady food intake of protein, healthy fats, and some vegetables on the keto approach will help ensure you don’t suffer from any potential blood glucose issues.

  • If you are someone who has had eat disorder issues in the past, it may not be a good idea to try intermittent fasting.

Even if you are recovered from your eating disorder, it may trigger eating disorder-like behaviours, which are not going to be healthy in the long run.

  • Weight loss may come about too quickly.

While this may seem like a good thing, keep in mind if you lose weight too rapidly, you’ll probably lose a good deal of muscle mass and your health may be in jeopardy. This can come if people do not increase the size of the meals they do eat and thus, begin taking in an exceptionally low calorie intake.

The good news is that if you are healthy individual who has a good relationship with food and you plan your intermittent fasting keto diet wisely, you should have no problems.

Who Should & Shouldn’t Fast

So who should and shouldn’t fast?

Mostly everyone can fast with the exception of a few people. These include children, pregnant women, those trying to become pregnant (fasting may interfere with your fertility levels), as well as anyone who is suffer from diabetes or an eating disorder.

So if you are looking to try something new with your keto diet, give fasting some consideration. You may find that you like your keto diet even more when you add this to your day.


[1] Halberg, Nils, et al. “Effect of intermittent fasting and refeeding on insulin action in healthy men.” Journal of applied physiology 99.6 (2005): 2128-2136

[2] Klempel, Monica C., et al. “Intermittent fasting combined with calorie restriction is effective for weight loss and cardio-protection in obese women.” Nutrition journal 11.1 (2012): 98

[3] Li, Liaoliao, Zhi Wang, and Zhiyi Zuo. “Chronic intermittent fasting improves cognitive functions and brain structures in mice.” PloS one 8.6 (2013): e66069

[4] QUABBE, HANS-JÖRGEN, ERICH SCHILLING, and HANS HELGE. “Pattern of growth hormone secretion during a 24-hour fast in normal adults.” The Journal of Clinical Endocrinology & Metabolism 26.10 (1966): 1173-1177