Quick Fix To Improve Metabolic Flexibility

Stéphane Aubé

Articles, Nutrition & Supplementation

0 min
Quick Fix To Improve Metabolic Flexibility

Quick Fix To Improve Metabolic Flexibility

We all know someone who seems to eat almost whatever he/she wants and keep his/her waistline as if he/she was following a strict diet (somewhere deep inside us, we feel a certain hatred towards these people, even if it’s our best friend).

On the extreme opposite, we also know people who can’t smell a donut without putting a pound or two on the scale (hope it’s not you, but if that is the case, make sure to read the entire article, this can really help you get out if this situation).

Many will reject this condition on the fate that nature holds for us, the genetic factor. While it is true that some people are blessed with genetic advantage that others don’t have, humanity has not condemned you to remain in this situation for the rest of your life.

The main factor that influences the direction of your body composition is called metabolic flexibility. Of course, this factor may be naturally advantaged by nature, but it is not necessarily a question of destiny. If we look at some numbers, 32% of your metabolic flexibility can be predicted by genetics. That means that the remaining 68% can be improved by your actions. You control the major part of the response you get from your diet and your training.

What Is Metabolic Flexibility?

First, it’s important to understand what metabolic flexibility is. To keep it brief, metabolic flexibility is the ability to switch from one fuel source to another and respond to different nutritional intake and energy demands. For different reasons (a good example would be to switch from a high carbs diet to a low carbs diet), a fuel source can become discontinued, pushing the body to search for another source.

A good metabolic flexibility will make it easier to switch from lipids to carbohydrates and transition between both energy sources. Going from carbohydrate fueling to fat-burning quickly allows an individual to feed himself in a more varied way and to mix the macros while improving his body composition.

Metabolic flexibility can also describe the ability to adjust to energy intake. Let’s say that you are travelling and that the schedule does not allow you to eat every 2-3 hours. An individual with good metabolic flexibility will be able to use stored energy to meet these demands. Otherwise, drop-in energy would be felt, fatigue, feeling of unbearable hunger, etc. … would rise until you can eat.

People with good metabolic flexibility will quickly adapt to different diet strategies, alter their caloric intake, macros and food choices without being too negatively affected by the changes. Their body will also be more efficient at using fat for fuel and carbs and proteins for muscle growth and recovery. These people will be able to change their body composition quickly.

What Are Our Main Fuel Sources?

There are three main fuel sources our body can convert into energy. The fact that some people respond better to some dietary strategies is a good indicator that they can convert some type of food into energy better than another.

Proteins can be one fuel source, although it is very limited unless you are under extreme conditions and on a very low caloric intake, relying on a protein-only diet. The fact that you are training hard and consuming higher amount of proteins can already protect you from proteins oxidation. Remember that our organism is made to survive, so you really have to dig deep to rely on proteins to fuel your body. But if you are someone who really can’t burn fat for fuel, this condition is really not ideal as amino acids will be converted into glucose via a pathway called gluconeogenesis.

Carbohydrates, also called glycogen once in the muscle and liver, is a favorable fuel source for high-intensity exercise like weight training and or high-intensity cardio. That feeling when your muscles are full and pumped is related to carbohydrates consumption.

Lipids is another fuel source and is usually the one we want to burn the most time. When you are resting, sleeping, walking, etc., this should be the main source that drives your daily activities and bodily functions. Even low intensity cardio for example, should rely on fat burning to respond to the low energy demand. If you have low metabolic flexibility, this pathway becomes inefficient and you frequently feel hunger throughout the day since you can not access your stored energy reserve. So, your only way to get energy is to eat and burn calories from the meal eaten previously. The downside of this situation is that fat loss becomes extremely difficult, slow or even non-existent.

How Metabolic Flexibility Can Improve Your Physique

Basically, metabolic flexibility is closely related to insulin sensitivity. Someone with good metabolic flexibility will be good at nutrient partitioning. The food consumed will serves as muscle growth and recovery rather than fat storage. This situation can help an individual to gain muscle mass quicker and to gain fat slower in the process. More of the nutrients eaten will be used to fuel muscles during workouts, allowing more intensity, more volume and more performances, resulting in more growth and better recovery.

People with poor metabolic flexibility will usually gain fat quickly because they can’t use nutrients as fuel to perform and grow. This process can quickly lead to insulin resistance which can create other problems and have a snowball effect over time. This is one of the reasons why most people who come to me with a high body fat are usually put under a strenuous fat loss phase first, even if their goal is to gain mass.

I always try to put the body in a good position before trying to add mass. Otherwise, gaining mass is like driving a car in the mud, the further you go, the more shit you accumulate. Eventually, the car simply does not move forward anymore, and you find yourself caught in a situation without issue. The only way to get out is to go back.

On the other hand, those who seek fat loss will be in a better place to use fat stores for fuel. They will burn more fat at rest, more fat when working out, and will also feel better during the process. If you have ever competed in a fitness contest, remember that feeling when you are 2-3 weeks out and feeling like shit. Each workout feels like a mountain to climb and every morning cardio is like a zombie walk. This is because your fat stores are practically empty, so there is not enough fuel to drive your engine.

People with poor metabolic flexibility can quickly feel like this when starting a fat loss phase because they just can’t access this stored energy. A kind of vicious circle is created because they will succumb to hunger and / or lack of energy and will cheat on their diet to fulfill this energy need. The process will be repeated overtime and will lead to nothing but demotivation.

Place Yourself In A Winning Situation

The best condition in which you can place yourself is to allow your body to react quickly to fed and fasting conditions.

Someone with a good metabolic flexibility will quickly tap into stored energy, which is body fat. So, the individual will be able to resume low intensity activities without the feeling of reduced energy. It is also a good place to lose fat efficiently.

To test your metabolic flexibility, try fasting when you wake up and see how much time it takes before your feeling of hunger becomes unbearable, or other side effects like headaches, nausea and fatigue appear. If you can’t do more than 3-4 hours, then there really is a problem and you should address this before anything else. I have athletes that can run a high calorie diet and then just cut out food for a whole day and they will feel energized from this. Some even double their cardio time to put this situation to profit.

On the other hand, fed conditions will raise insulin levels. You have to know that whatever you are eating, there is always a release of insulin to some degree. So, in a fed state, your body switches from fat metabolism to carbohydrates metabolism.

This condition is also called ‘’storing mode’’ because this is a situation where insulin will be used as transporter and will drive nutrients to the cellular level. Individuals who are lean will usually get great benefits as they are able to store their carbs into the muscle cells and can quickly come back to fat metabolism. They can fill muscle glycogen and still lose fat without impairing their body fat level.

To know if you are in this condition, eat your first meal of the day with high GI foods. A good example would be to eat pancakes with syrup. Don’t add fat and or proteins that can slow down digestion. Just eat a high carbohydrate meal and see how you feel after it. If you feel like you want to go back to sleep, or drowsy, then maybe your metabolic flexibility needs to be improved.

Now you are asking yourself ‘’Yeah this is great information, but what can I do if this is my case’’?

Ok hold on and stay with me. Here’s the good news, you can get out of this situation by using some strategies to force your body to tap into stored body fat and improve insulin sensitivity.

How To Improve Metabolic Flexibility

Several methods exist and can be great depending on the individual and the goal, different strokes for different folks. Here’s a couple of methods that can help improve metabolic flexibility, one or more methods can be used at the same time.

Mitochondrial Biogenesis

Mitochondria are responsible for ATP production. This is the engine for our cells’ functions. The importance of their functions is vital to us. Improving their functions makes us more efficient at burning energy. But we can also create more mitochondria, a process called mitochondria biogenesis. Allowing for a greater number of these cells makes the process of burning fat and producing energy way better.

One of the best ways to do this is by incorporating HIIT (high intensity interval training) cardio. Not only is this good for cardiovascular health, HIIT cardio will put the body into EPOC (excessive post oxygen consumption) mode and push the body to create more mitochondria cells to supply the body with enough oxygen following the session.

Try adding 3-4 sessions a week. Something as short as 6 to 7 high intensity intervals can do the trick. Here’s a short protocol:

Week 1

3 x HIIT / week – 5 rounds of 15 seconds all-out effort and 45 seconds moderate effort

Week 2

3 x HIIT / week – 6 rounds of 15 seconds all-out effort and 45 seconds moderate effort

Week 3

4 HIIT / week – 7 rounds of 15 seconds all-out effort and 45 seconds moderate effort

Week 4, 5 and 6

Repeat the same process by pushing the all-out effort of 15 seconds to 20 seconds and reducing the moderate effort to 40 seconds.

Improve the all-out effort up to 30 seconds and resting phase to 30 seconds.

In a couple of weeks, you should already feel more fit but also more metabolically flexible.

Use Nutrient Timing

Nutrient timing is a way to organize and plan food intake based on your activity level at different times. For example, after a hard workout, our body is more insulin sensitive and is better at partitioning carbohydrates in a good way. It is a good way to take advantage of certain anabolic hormones, namely insulin.

A good way to apply this strategy is to plan your diet menu according to your workout time. Let’s say you work out at 4:00 PM. All the meals prior to the workout would consist of proteins and fat in a way to minimize insulin production. I’d even encourage you to train without any carbs prior to the workout. While maybe not optimal for high volume training, it can really force your body to use fat as fuel. Once the workout is done, drop out fat and consume your daily carbohydrates in the subsequent meals.

Macronutrients Cycle

Stop favoring one macro over the other. Long runs of high carbs diet or super low carbs diet will not help metabolic flexibility because over time, the body loses some of the required enzymes to break down the food source that has been dropped out of the diet.

Much like a carb cycle, cycling macronutrients is a good way to improve and keep metabolic flexibility over time. Even when gaining muscle, this should be a regular practice to overcome any impairments in metabolic flexibility.

For example, workout days can contain more carbs and off days less carbs or no carbs. You can also play with the volume of your workout. For example, higher volume days could contain more carbs and lower fat while moderate volume can contain less carbs and moderate fat. Off days could be higher in dietary fat and no carbs. Lower proteins on high carbs day if you want to control calories.

There are so many ways to define your plan to manage calories. By switching from one macro dominance to another, your body will adjust to different energy intake and will adapt overtime.


Of all the methods I know, fasting is still the greatest one to improve metabolic flexibility. Try incorporating small windows of fasting, even 12-14 hours can be beneficial to start. Work your way to longer windows of fasting period over time. Start with one day, then when you become more comfortable with this strategy, push for longer periods or add more periods of fasting in the week.

Not only has fasting has been shown to improve health in many ways, it can quickly fix metabolic inflexibility issues. Also, fasting will create a calorie deficit in itself, so it becomes a calorie cycling strategy at the same time, hitting two stones with one shot.

Fasted Morning Cardio

Upon waking, get yourself out of the bed for a walk. Using low to moderate intensity will allow you to use your stored fat as fuel. Just keep your heart beat between 110 and 120 bpm, no more. This can be efficient at slowly losing fat and improving metabolic flexibility. Once fed, a lot of people can just no longer tap into their body fat. Start with 30 minutes 3 to 4 times per week and see where it leads you.


Curcumin has been shown to reduce a compound released from your fat cells call IL-6. This compound has the ability to impair your fat burning process after a meal when metabolic flexibility is at it’s worst. Curcumin has been shown to reduce IL-6 efficiently and should be consumed every day at 1000mg spread through your meals.

Alternating Anaerobic Work And Aerobic Work

Switching for different types of workouts in a week can really help your body become more metabolically flexible. Forcing your body to rely on different energy pathways is another quick fix that can help in a relatively short period of time.

The body relies on three major pathways:

1.ATP – Intense activity of 0 to 10 seconds

Think about high intensity and max speed work like Olympic weight lifting, powerlifting, etc.

2.Glycolic / anaerobic – 10 to 120 seconds in duration

Higher repetition work and sustained energy like bodybuilding, sprints and MetCon are good examples.

3.Oxydative / aerobic – 120 sec and more (cardio and endurance workout)

Cardio work is a good example because of the low intensity but sustained and constant work for longer periods of time. Endurance work and very high repetition sets can also lead to this pathway being used.

The message here is simple: try incorporating different pathways of work into your workout, force your body to adapt to other kinds of energy demanding exercises. Playing with reps and sets, adding some metabolic circuits, strongman exercises and prowler/sled are also good ways to reach different pathways of energy.

The same way as always eating the same kind of macros can lower metabolic flexibility, always doing the same kind of workout can also impair your ability to use energy while working out.

How Much Time Can It Take To Reverse This Condition?

Of course, different individuals will respond more or less quickly. But all these strategies combined, metabolic inflexibility can be quickly fixed. You need to understand that losing fat will always lead to better insulin sensitivity and therefore metabolic flexibility. If your situation has been outlined in this article and you feel you are trapped in metabolic inflexibility, stop worrying about muscle gains for a moment. Focus on resolving this situation first and future gains will only be better and faster.