What is Metabolic Flexibility?
Metabolic flexibility means your body uses whatever fuel is available , dietary fat and stored fat, or glucose (sugar) and glycogen (sugar stores). This means your body can use carbs or fats for fuel. The term metabolic flexibility was coined by a team of researchers in 1999 when they studied fuel selection in skeletal muscle in lean and obese individuals after an overnight fast. They studied 16 lean & 40 obese volunteers & discovered that skeletal muscle of lean individuals showed a remarkable ability to adapt to fuel preference to fasting and insulin infusions and were therefore designated as metabolically flexible.
Why is it Important To Be Metabolically Flexible?
It sounds confusing, but simply put, when you are metabolically flexible, your body is better able to adapt to energy demands breaking down the foods you eat. Someone with good metabolic flexibility utilizes carbohydrate for high intensity exercise, and switches efficiently to burning fat at low intensities, or at rest. Improved metabolic flexibility can help you achieve:
- Better weight maintenance
- Increased energy levels
- Better health
- Lower odds of developing a metabolic disease
- More consistent, healthy glucose levels
- Improved sleep
- Optimized workout performance
Metabolic Flexibility & Insulin Resistance
According to Metabolic Flexibility and Insulin Resistance, by The American Journal of Physiology, “the inability to modify fuel oxidation in response to changes in nutrient availability has been implicated in the accumulation of intramyocellular lipid and insulin resistance .” This means that poor metabolic flexibility can lead to lipid, aka fat build-up and insulin resistance. According to Why Does Insulin Resistance Occur in Type 2 Diabetes by Diabetes UK, “Insulin resistance is the driving factor that leads to type 2 diabetes, gestational diabetes and prediabetes. Insulin resistance is closely associated with obesity; however, it is possible to be insulin resistant without being overweight or obese.” It is important to note that even though insulin resistance and obesity are correlated, you can be insulin resistant and not overweight or obese.
How to Identify if Your Metabolism is Inflexible
Here are some signs to help you recognize if your metabolism is inflexible. You may experience 1 or more of these symptoms:
- Feeling “hangry” during fasts (10 to 14 hours)
- Sleepiness after meals
- Mid-day energy crashes
- You have insulin resistance, prediabetes or type 2 diabetes
- Being overweight
- Feelings of anxiety
How to Improve The Flexibility of Your Metabolism
Before I begin this section, I will stress that you do not make any dietary changes without guidance from a medical or dietary professional.
Here are some tips to begin your journey to a more flexible metabolism:
- Exercise
Exercise is one of the easiest ways to improve the flexibility of your metabolism. In fact, According to Metabolic Flexibility and Insulin Resistance, by The American Journal of Physiology, “lipid accumulation in skeletal muscle of sedentary people is associated with impaired insulin-stimulated glucose metabolism.” Meaning that being sedentary with an inflexible metabolism can increase lipid (fat) build-up in skeletal muscle.
2. Identify If You Are Primarily A Carbohydrate or Fat Burner
This is vital because as discussed above, a person with a flexible metabolism is able to switch between fats & carbs as needed for energy. However, a person with an inflexible metabolism may struggle to break down fats or carbs. Meaning, they can be good at breaking down fats or carbs, but not both. If you identify if you are primarily burn fats or carbs, then you can begin to understand why your metabolism is inflexible.
Here are some ways to identify if you are a sugar burner:
a. A few hours after you eat, you’re hungry
b. If you go too long between meals you feel tired or irritable aka “hangry”
c. If you often crave carbs, especially processed carbs
d. If your diet has been carb heavy for an extended period of time
Here are some ways to identify if you are a fat burner:
a. Your blood sugar stays balanced and so does your energy level
b. If you have been eating a keto, carnivore or any fat heavy diet for an extended period of time
c. If you feel discomfort like bloating when you eat carbs
All items mentioned above can be symptoms of other underlying health issues
3. Adjust Your Diet Accordingly.
Here it is important to understand that if you are a sugar burner, your body may down-regulate it’s ability to burn fats efficiently and if you are a fat burner, your body may down-regulate it’s ability to burn carbs efficiently.
A slow, balanced approach to reintroduce more of these macros into your diet seems to be the preferred approach. Over time, your body should create the appropriate enzymes, i.e amylase to break down carbs & lipase to break down fats. Most research tends to show that going from a sugar to a fat metabolism is more challenging. Scientists believe this is due to humans are born with more carb burning enzymes like amylase than any other mammals on the planet.
4. Hack Your Metabolism with Lumen
This leads me to my last point. Lumen measures the C02 levels in your breath to interpret if your body is using carbs or fats for fuel. High calorie intakes, especially as carbohydrate, increases carbon dioxide production vs energy intake from fats. Lumen provides you with a daily measurement of your source of energy: fats or carbs on a scale of 1 to 5. Based on the state of your metabolism, their nutritionists provide daily nutrition guidance via the Lumen app, to train your metabolism to burn fats & carbs efficiently. Using Lumen takes the guess work out of the equation.
I take digestive enzymes, once daily, with my largest meal to give my body sufficient enzymes to promote a flexible metabolism.
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I really understood more what the lumen does and why it indicates the numbers that it does for me. I’ve been doing keto for over 5 years so I’ve been basically off sugar. I’ve also gone through major surgery having a total hysterectomy because of ovarian cancer 2021. So far I’ve enjoyed the lumen and I think it’s a better way of eating vs keto. I’m enjoying some of my favorite foods in moderation and hope to lose 15# and then go metabolic flexible program. Thank you for your help.
Thanks for sharing. I see this often when people come from keto. When we restrict a macro for too long, our bodies will downregulate it’s ability to break then down efficiently.
I really appreciate the in-depth look at why it can be difficult to switch from a LCHF diet back to a high carb boost day. I really thought I would be more metabolically flexible but apparently I’m struggling in the fat burner category. Thanks!
You are welcome. Training your metabolism is the best approach for sustainable weight management