Beyond Ketosis: Metabolic Flexibility

While on a Kultured Wellness program, I recommend the ketogenic diet for most of our clients.

The main reasons for this include:

  • Starving out pathogens that are causing havoc in the gut  
  • Using ketosis as a pathway for autophagy and mitophagy (I’ll get back to that)

Ketones are a much cleaner fuel source than glucose and produce significantly less free radicals when they are burned as a fuel within the cell.  

Having said that, it is not recommended to stay in ketosis forever. Cycling in and out of ketosis is an optimal way to live, in fact, it is the way in which our bodies are designed to function. To cycle into and out of ketosis effectively, we need what we call Metabolic Flexibility, also called plasticity or adaptability.

Here are some reasons why ketogenic cycling is beneficial:

  • Coming out of ketosis allows for the consumption of higher carbohydrate vegetables, nuts, seeds and fruits that feed and diversify our microbiome
  • Consumption of higher carbohydrate foods at times allows for replenishment of muscle glycogen stores after physical exercise
  • ‘Use it or lose it’ - by switching into glycosis and back into ketosis, we maintain the bodies ability to switch between the two (we will learn later what the consequences are of having inflexible fuel preferences in the body)

Nutritional Ketosis - An Effective Practice for Establishing and Maintaining Metabolic Flexibility

The ability of our bodies to enter ketosis is a key survival trait. Imagine if we did not have access to any food (fuel for our cells) for a prolonged period (ie: fasting). Within a short period of time, our cells would starve and start dying off. Instead of this picture of doom, our resourceful bodies begin breaking down our fat stores into simple fatty acids (or in the case of nutritional ketosis - breaking down dietary fats).

This process is more energy efficient, we do not use as much energy burning fatty acids, and here, we can marvel at the wonder of our bodies, intuitively knowing we are in a period of limited resources (food) and entering into a state where we do not require as much energy to keep our underlying metabolic processes ticking over.

For those with good metabolic flexibility, you can wake up in ketosis after your overnight fast (unless you sleep eat), you can enter ketosis during prolonged exercise, and your body will remain efficient at using both fuels.

Finally, ketosis has been found to be comparable to glycosis in terms of normal physical function in the body and ketones are readily used by almost all cells within the body.

What is Metabolic Flexibility?

Simply put, it is your body's ability to switch between fuel sources, predominantly, carbohydrates and glucose, dietary fat and body fat stores.

Put another way, metabolic flexibility is the ability of the body to provide consistent energy supply to the body regardless of feast, famine, rest or activity. Research has shown that skeletal muscle in healthy, lean people is able to switch easily from using glucose to using fatty acids. Now, this obviously means better physical performance in sport and less fatigue from day to day. Now imagine it is your brain that struggles to switch from glucose to fat burning or your heart muscle. Imagine the impact of having no efficient way to fuel these vital organs?  

The ability of your body to store fats during a period of availability and break down fats during a period of fasting is key to keeping balance within your body. For those in nutritional ketosis, this means utilising fats during a period of low carbohydrate consumption, then using glucose when carbohydrates are consumed, then switching back again. Basically, it just means your body can provide your cells with a constant flow of fuel, no matter your diet, allowing for optimal function of the cells.

So I can switch between burning fatty acids and glucose… great! But how long should I spend in ketosis versus glucosis?

That is different for everyone and only you can answer that question based on your energy levels, your appetite, the time of year, how much you are moving your body etc…as a society, we eat far, far, too many carbohydrate-rich, energy-dense foods that generate a state of confusion for the body. This has been described as a process where various functions are turned off. Eg: proper use of fats in the body, proper function of your mitochondria, increased oxidative stress. It is described as a state of ‘metabolic indecision’ and the inability to switch between fuel sources (Smith 2018). Our bodies were not designed for constant supply of energy and we are on our knees holding the weight of modern food abundance.

‘The most common environmental condition in nature is the one where energy availability is scarce’ (Serrano 2016).

What happens when you're in Glucosis - the (super) simple version and why you don't want to be in it all the time

In response to glucose intake, your pancreas secretes insulin and the liver absorbs glucose for storage. Your fat cells receive the signal to stop breaking down fat and triglyceride formation is triggered. See! I said super simple. But there is a lot more to it. For instance, insulin and glucose are both inherently inflammatory and can damage blood vessels and tissues within the body by triggering the production of inflammatory compounds known as cytokines.

The process of metabolising a carbohydrate-rich meal provides energy to the body but is also is a protective process. We store fuel within our bodies in response to dietary glucose - tucking away energy for a day when we need it. The issue is, that day rarely comes as, in the west, we spend most of our lives in glucosis, popping fuel stores away for later. We then enter into a chronically inflamed state with disturbances to our appetite-regulating hormones. Eventually, our pancreas does a very scientific thing known as ‘blowing a fufu valve’ and diabetes follows shortly after. Just a little statistic for you - 280 people develop diabetes every day in Australia, and it is increasing faster than any other metabolic disease.

Think about that for a minute. Our modern lives, with a constant flow of energy-dense foods, leads to elevated insulin, insulin resistance, cholesterol abnormalities, and obesity. Would it seem reasonable that we evolved to have periods of abundance mixed with periods of scarcity, including a wide variety of fuel sources, including fats, and regular periods of fasting? We are able to and in fact, need to, be adaptable to a dynamic food environment. In this scenario, our bodies are trained to access energy efficiently and quickly, to appropriately store fuel when needed, break it down when needed and to engage in clean up processes like autophagy (where Pac-man like cells go around eating up and recycling bacteria, virus and cellular debris). One of these ways of eating is perfectly suited to a healthy human body, and one is dysfunctional.

Hallmark Characteristics of People with Low Metabolic Flexibility

Okay, ketosis is great. Why do I want to switch back and forth?

People with low metabolic flexibility will find it difficult to rapidly switch to using fatty acids as a source of energy. Switching into ketosis may be difficult and the cells of our body, not being efficient at using fats, is starved for energy for a period. This process is responsible for that feeling of fatigue or ‘keto flu’. With metabolic flexibility, you can switch to burning fats, back to glucose and back to fats easily.

  • Hitting the wall during exercise
  • Inability to skip a meal
  • The constant need for snacking
  • Fatigue

The above all indicate an inability to switch from glucose to fat burning. However, there are more significant consequences of metabolic inflexibility:

  • It is believed to be the key factor in the development of many metabolic diseases, diabetes, PCOS, cardiovascular disease and Alzheimer's to name a few.
  • Metabolic inflexibility is shown to also play a role in cancer, low-grade inflammation, and autoimmune disease.
  • People with metabolic inflexibility have limited ability to use fatty acids as an energy source after fasting. This means starvation for the cells, fatigue, mood disturbances.
  • A lack of fuel to the cells means impaired cellular function, use of nutrients, production of energy, clean up and detox within the cell - all impaired. (Cox 2016).

What can you do, day to day, to improve metabolic flexibility? Lots!  

  • Limiting your carbohydrate intake to reflect the levels we historically consumed
  • Use periods of fasting  
  • Movement (so important)
  • Use of ketogenic cycling to keep your insulin levels low, to keep your cells responsive to insulin and retain the ability to effectively and efficiently break down fats and use ketone bodies for energy.
  • Support your mitochondria, enjoy a nutrient-rich diet including:
    • Magnesium and other minerals and electrolytes
    • Polyphenol-rich foods
    • Omega 3 rich foods
    • Dietary fiber


📸 Jordan Pie