Keto and metabolic flexibility


We have already discussed why we consider keto the foundation of health. The reasons are insulin sensitivity, satiety, nutrients and much more.

But it all drills down to this key concept of metabolic flexibility. Whatever you do with your diet if you want to optimise your health you need to be able to utilise fuel efficiently and effectively.

Let’s dive into the magic world of keto metabolic flexibility, shall we?

The basics

Metabolic flexibility is the state where the body can use either carbs or fat fuel efficiently to avoid energy crashes, to maintain a lean body mass, be insulin sensitive and have a healthy body. 

This is unfortunately not where most people are. To be metabolically flexible this requires that you are able to use your own fat fuel. Yes you heard it right! Our fat is there to be used as a constant source of energy. To fuel us and keep us energetic so we don’t have to eat every 3 hours or have cravings and energy crashes!

If we eat a high-carb diet and 5 meals a day we will block the access to our fat stores. This is when the hormone insulin comes to play. Every time we eat we secrete insulin which is an energy storing hormone. If we constantly eat carbs we will constantly have high insulin and never go into fat burning mode. And we are not talking about weight loss here. 

The mechanism of burning fat is a fuelling mechanism. It is an energy system that we want to always be able to access. Imagine driving a hybrid car which never uses electricity. That doesn’t sound right does it?

Getting into this state is a lot easier through a ketogenic lifestyle. This is how our ancestors lived for many thousands of years.


  • Metabolic flexibility allows us to burn both carbs and fat for fuel.
  • If we eat constantly carbs we are never able to efficiently burn fat for fuel.
  • Keto (and fasting) will help you reach metabolic flexibility which is the foundation to health.

About metabolic flexibility

Of course there were times in history when people had access to foods high in carbohydrates. Especially in the spring and fall there was plenty of fruit that was definitely part of their diet.

And this exactly is the point of metabolic flexibility!

Our physiology is such that we can efficiently metabolise fatty foods and carbohydrates. The goal of ketogenesis is not to be exclusively in ketosis forever. On the contrary, if we understand our physiology, and our history, we will see that we want to be metabolically flexible. To do intermittent fasting, while when we eat to be mainly with a ketogenic diet, with periods when we will eat carbohydrates, mainly fruits, seasonally, locally and without treatment.


But in order to get such a diet and be full of energy we need to get rid of sugar (especially refined) and enable our body to function by using fat as a form of energy. This is the true metabolic flexibility that helps us stay healthy, at our ideal weight and away from disease and inflammation.

In this way we will 

  • Have normal insulin levels.
  • Not overload our liver with sugar (glucose).
  • Eat foods that fill us up.
  • Eat foods that have high nutritional value.
  • Have balanced hormones and we will not be hungry all the time.

The result of all the above will be the loss of unnecessary weight.

Of course this process takes time to become part of our lives. I have worked with people who took them even a year to be truly independent of the drug called sugar, and even more so to reach their ideal weight.

But the reward is unique. Energy all day! This is the most important criterion of metabolic flexibility and the reason to start ketogenic!


  • Keto will allow you to become metabolically flexible since burning fat for fuel is the first prerequisite.
  • Once you are adapted and can use efficiently fat our insulin levels will be normalised and you can use carbs again efficiently.
  • At this point (and depending on your age) you will be able to switch between fuel sources and have constant energy throughout the day! 

Why Keto is the way to go

Keto does not restrict carbs per say. It restricts high glycemic carbs. These are carbs that will spike our blood glucose levels a lot. When we eat potatoes, cookies or cakes the liver suddenly gets all this energy that it has to deal with. This is an emergency situation that the body deals with, with the help of insulin.

As Jason Fung has very nicely explained, we have two energy stores. The first one is a really small one and can only store glucose. That is our liver. The second one is a huge one and is our body fat. The body creates this energy repository for a purpose. To use it later on for difficult times when food is not available. But this process is regulated by insulin. Insulin is the gate keeper, when we have high levels of insulin circulating, even we haven’t eaten for hours, the body thinks we are still in a fat storage mode and we can never access our body fat.

This is a very common issue. A huge percentage of the population has high insulin. This is called insulin resistance. When we eat insulin should go up and come back down in 3-4 hours. Imagine now waking-up after 8 hours of sleep and still have high insulin! This is a disease state!

Keto is the easiest way to fix the issue and I have seen it with everyone I work with. Literature is also demonstrating that when we stop putting all this load on the body to deal with sugar we have many favourable outcomes. 

Keto –> Low insulin –> Metabolic Flexibility

This is the path for health!


  • Insulin is a fat storing hormone that manages distribution of carbs we eat.
  • When we eat too much carbs insulin does not work effectively which will lead to insulin resistance.
  • Keto addresses this issue and helps bring insulin down to normal levels.

Key Takeaway

  • Metabolic Flexibility is what we should be all looking for. 
  • Aim to be mostly a fat burner which will give you all the energy your body needs.

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