Everything You Need to Know About Metabolic Conditioning

A Complete Guide to Metabolic Flexibility

Simply put, metabolic flexibility is the body’s ability to switch between different fuel sources and produce energy under various conditions.

A more scientific definition is the capacity for skeletal muscle to acutely shift its reliance between lipids and glucose during fasting or in response to insulin, such as postprandial conditions.

Your body generates energy through two main methods; burning up stored carbohydrates or fats.

What determines how metabolically flexible you are is how easily your body can switch back and forth between using stored fats or carbs for energy without running into energy crises.

If you have low functioning or inefficient mitochondria (energy sources in your cells), your body will utilize only stored carbs and not stored fats.

Mitochondria inefficiency can be caused by eating too much-processed foods, having a high carbohydrate diet, not including enough antioxidant foods, among other factors.

In this article, you will learn everything you need to know about metabolic flexibility, from how to gauge your metabolic flexibility to how to improve it.


A Complete Guide to Metabolic Flexibility

The following are signs that may indicate that you are metabolically flexible;


Getting hungry throughout the day and getting massive sugar/carb cravings may mean your body has a hard time tapping into stored fat in the absence of carbohydrates.

If you notice that you stay full and have mental clarity for the better part of your day, you may be metabolically flexible even without having eaten.


If you always need to eat carbs before fitness training, there is a high chance you aren’t metabolically flexible.

This means that your body relies on one fuel source when there are many other sources it could use apart from carbs.

A metabolically flexible body would burn fat at high intensities such as High-Intensity Interval Training (HIIT) or sprinting as opposed to a body with a carb-dependent metabolism.


A less-known indicator of metabolic flexibility is the ability to tolerate various ingredients and food sources, especially danger foods like nightshade, lectins, nuts, beans, eggs, gluten and fish.

Of course, this doesn’t apply if you have an autoimmune condition or food allergies because then there isn’t much you can do about your food intolerance.


Not everyone can have a smooth fasting experience with no hurdles.

While some people can easily adapt to going for hours without food, others get lightheaded, hungry and tired if they so much as skip a single meal.

If you have high metabolic flexibility, your body should find it easy to switch from burning carbs to burning fat for energy without you having to experience any of the above-mentioned side effects.


Insulin resistance happens when you eat carbs, and your cells fail to open up to receive the fuel resulting from burning them up.

A carb-rich diet can cause insulin resistance because regular insulin surges affect desensitizing cells.

When your muscles and organs become less sensitive to insulin, your body presumes that there isn’t enough insulin available, thereby increasing insulin production.

Increased insulin production reduces the body’s ability to burn fat for fuel which encourages metabolic inflexibility.

This is why type 2 diabetes is linked to metabolic inflexibility, according to research.

This situation can be remedied by reducing the number of carbs in your diet, which will, in turn, reduce the risk of cell desensitization.

When your cells are sensitive to insulin, they will readily receive the fuel produced from carbs, allowing your body to burn fat for energy, enhancing your metabolic flexibility.


Ketosis is a physiological state in which your body switches to alternative fuel sources when the availability of glucose in the blood is low. It happens when you are fasting or when you lower your carbohydrate intake.

Ketosis is the body’s natural metabolic alternative designed to keep us alive when we go for long periods of time without food.

You can easily achieve ketosis through a ketogenic diet. A ketogenic diet is a diet that restricts carb intake and increases fat intake.

When you are on a ketogenic diet, your body primarily burns fat for fuel and, in the process, produces compounds known as ketones.

Ketones allow your cells, even those heavily dependent on glucose for fuel, e.g. brain and nerve cells, to be metabolically flexible.

The longer you stay on a ketogenic diet, the more your cells get used to using alternative fuel sources in the absence of glucose/carbs.


There are a couple of ways through which you can enhance the ability of your body to switch between different fuel sources, including;


Aside from helping with weight loss, intermittent fasting can boost your metabolism flexibility. This it does by training your body to use alternative sources of fuel for energy in the absence of carbs.

Periods of fasting can also shift your body’s Resting Metabolic Rate (RMR), making your body burn more fat, research suggests.

The changes in your eating periods that are brought about by intermittent fasting are likely to improve your flexibility without compromising your body’s ability to use stored carbohydrates for energy.


Doing low-intensity exercises such as cardio during fasting can help enhance your flexibility.

A 2000 study found that low-intensity cardio exercises such as cycling can improve your fat oxidation percentage.

Additionally, there’s a certain theory that you can make your body more metabolically flexible by doing cardio while fasting.

When you begin fasting, your body uses the glycogen in your body first before tapping into the fat deposits.

Doing cardio exercises when there’s little to no glycogen available in your body forces it to tap heavily into your fat reserves.

Over time, your body will get used to switching between using carbs and fat as fuel sources even after you are done with fasting.


Foods rich in omega-3 fats such as fish can improve mitochondrial function by removing the excess linoleic acid in the mitochondrial membranes.

Improving mitochondrial efficiency, in turn, improves the body’s ability to switch between different fuel sources.

Polyphenol-rich foods with antioxidant properties such as dark chocolate and berries also affect increasing insulin sensitivity.

You can also enhance your body’s flexibility by eating magnesium-rich foods.

Magnesium deficiency increases mitochondrial oxidative stress which inhibits the functioning of mitochondria. It has also been linked to insulin resistance.


When your body is in ketosis, it gets used to burning both dietary and stored fat for energy.

With time, your body’s ability to switch between burning fat and carbs for energy will improve even after you go back to eating carbs regularly.

However, before you start a ketogenic diet, you should be aware of certain symptoms you’re likely to experience during the first few weeks such as fatigue, irritability, hunger, headaches and body aches (aka the ‘keto-flu’).

These symptoms will be no fun but you’ll thank yourself later when you come out of your ketogenic diet with high energy, minimum cravings, elevated mood and minimum to zero cravings.


While it is not compulsory to be metabolically flexible, it will most certainly improve your body’s functioning by keeping your insulin in check.

It can also contribute to weight loss if you are looking to shed some fat.

Hopefully, this article has furnished you with knowledge on everything you need to know about metabolic flexibility.

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