Do You Have to Fast on Keto?

Do You Have to Fast on Keto?

By Chris Irvin, M.S.

The ketogenic diet was first discovered for its ability to mimic fasting.  In the early 1920’s, researchers found that a low carb diet led to ketone production similar to fasting.  Since fasting had been used as a treatment for epilepsy since 500 B.C., doctors speculated that a very low carb diet, which they termed “ketogenic”, could be used in the treatment of epilepsy with added benefits of being able to sustain longer than fasting and greater nutrient intake for growing children.

While early doctors were looking to use keto instead of fasting, more recently we have found that pairing the two can lead to robust health improvements.  Let’s look at the similarities between these two diet strategies to see why combining the two can be a great strategy. 

Similarities Between Keto and Fasting

Keto and fasting both lead to lower blood sugar, lower insulin, and greater ketone prodution, which is where the majority of the benefit from these two strategies comes from. 

Fasting naturally lowers blood sugar by lack of food intake.  During a fast you burn through your last meal and eventually start to dip into stored body fat for energy which leads to ketone production.  On keto, you are achieving this same thing but by way of carbohydrate restriction. The lack of carbs on a ketogenic diet allows blood sugar and insulin to lower and ketone production to occur. Essentially, if you zoom in you find that fasting and keto both produce similar metabolic changes in the body. 

Benefits of Combining Fasting and Keto

Besides the individual health benefits keto and fasting can provide, combining the two offers its own unique list of benefits. 

Greater ketone production: Combining keto and fasting can lead to greater ketone prodution.  Research has found that the brain will take ketones in for energy in proportion to their availability in the blood.  In other words, increasing our blood ketone levels means more energy to our brain.

Sustained ketosis: There are benefits to staying in a state of ketosis for prolonged periods of time.  Following a fast with a ketogenic diet keeps your body in a state of ketosis during the feeding window.  This state of ketosis can be maintained until carbs are introduced back into the diet.

Easier fasting: Fasting has a lot of health benefits but it can be a challanging strategy for some.  Especially those eating a higher carb diet.  Keto naturally keeps blood sugar stable and hunger levels in check.  This makes for much easier and more enjoyable fasting.

Blood sugar: Spiking blood sugar is not necessarily a bad thing, unless you have impaired metabolic health.  Those suffering from prediabetes, diabetes, and obesity could benefit from limiting blood sugar spikes as often as possible which combining fasting and keto is a great strategy for. 

Do You Have to Fast on Keto?

Just because you can fast on keto and it can provide a lot of benefits doesn’t necessarily mean you should.  Nutrition is personalized and we need to consider our current situation, health goals, and what works best for our bodies.  

If you are new to keto, combining fasting and keto may be too challenging at first.  As you become keto-adapted, fasting becomes much easier and most keto dieters naturally transition to combining the two.  

If your goal is to gain weight, fasting and keto may not be a good fit.  The lack of calories consumed due to a restricted feeding window and lack of hunger would make it hard to gain weight.

Tips for Fasting on Keto

If you do choose to combine fasting and keto, here are a few tips to make your experience better: 

Drink water: Both fasting and keto lead to our bodies releasing more water thus making us more prone to dehydration.  Combining the two will only make this worse so be sure to stay hydrated during both your fasting and feeding windows.

Supplement with electrolytes: Similar to water, our bodies also lose eletrolytes during fasting and low carb diets. Replenish sodium, magnesium, and potassium to avoid keto flu symptoms and keep your body functioning optimally. 

Post-Fast Protein: Have your first meal after a fast be high in protein.  This is a great way to ease your body back to eating and to create a positive nitrogen balance for muscle maintanence/growth. 

Nutrient dense feeding window: What you eat during your feeding window determines how you are going to feel during your fasting.  Pack your feeding window with nutrient dense whole foods to make sure your body has what it needs to thrive during the fast.

Add exercise: If fat burning is your goal, adding in exerise with these two diet strategies is a great way to further ramp up the fat burning process.

Wrap Up

Fasting and keto are great individual diet strategies that can be combined to produce even more robust health results.  If you are new to keto, you may want to focus on getting adapted to the diet first.  If not eating breakfast comes naturally to you, then lean in and try combining fasting and keto for better and faster health improvements.