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The Pain and Glory of Metabolic Flexibility

By Ritamarie Loscalzo


It’s now known that metabolic flexibility drives metabolic health.  Current statistics point to 88% of the population as being metabolically unhealthy which leads to a long list of chronic health conditions that cost billions of dollars and thousands of needless deaths every year.

The whole point of metabolic flexibility; what it is and why it’s important, is getting lost in the conversation. It’s becoming all about the tools used to get there, such as ketogenic diets and intermittent fasting (IF).  Due to misinformation, both are becoming  viewed as more of a fad than the valuable tools they can be.

 How do you correctly use a tool when you don’t understand the reason for using it? How do you sustain change without a meaningful “why”?

What is metabolic flexibility?

Simply put, metabolic flexibility is the ease with which your body can switch between burning glucose and burning fat for fuel.

You are born with the ability to easily shift between the two.  For thousands of years the human body had to be prepared to eat while food was available and store reserves for when it wasn’t. It is actually genius that your body figured out a way to carry those fuel stores with it in the form of fat, ready to be utilized when needed. The human race would not have survived if it had to find, manually carry, store, and protect what was necessary to meet all caloric needs on a daily basis.

What prevents metabolic flexibility?

In today’s world, due to the ever-present availability of food (especially highly processed carbohydrates), the misinformed advice to eat frequent meals, and the habit of mindless snacking, a constant supply of glucose is being provided for fuel, so your body never becomes good at using its stores of fat. It’s never given the opportunity to figure it out.  The fat just keeps accumulating.

When your body doesn’t get the carbs it is used to getting, it lets you know! Unless you suffer from a chronic condition that predisposes you to hypoglycemia, frequent hunger and feeling cranky, exhausted or jittery when you don’t eat is ultimately a result of your body not knowing how to access the fat that is available to it.  If it did, this would provide a seamless supply of fuel.  Your blood sugar would remain stable, bringing an end to all the theatrics being used to get your attention!

By stretching out the time between eating, the body begins to look elsewhere for its energy supply. This is all intermittent fasting is.  It’s not about calorie restriction, deprivation, losing weight or complicated eating schedules. It’s about creating spaces of rest for your digestive system and teaching your body it can stabilize blood sugar by utilizing fat.

When you begin using fat for fuel, you move into a state of ketosis, also known as being “fat adapted”.  This can cause a period of discomfort known as the “keto flu”, primarily because your body is still looking for glucose. This will pass.

As you adjust, all the old signs of “hangry” begin to diminish, and your body starts to automatically turn to fat stores for its fuel. When you easily transition between glucose and fat for fuel resources, skipping an occasional meal is no longer painful or uncomfortable. Your energy levels remain consistent even if your meals aren’t.

Oh, the joy of taking a cross country flight and not having to resort to airplane food for survival!

Ketosis is not metabolic flexibility.

I have concerns about the popularity of ketogenic diets, primarily because most fail to address the fact that being in a constant state of ketosis for long periods of time has diminishing health returns.  The true benefits come as a result of metabolic flexibility.

The “dangling carrot” of rapid weight loss, along with the promise you can do it while eating all the bacon you want also concerns me.  It is not healthy or sustainable and can lead to nutrient deficiencies, digestive and gut issues, and may damage bone health.

I believe ketosis plays a role in reaching optimal health, but only when it is achieved through a balanced, nutrient dense, plant-based approach.

The “why” of metabolic flexibility.

The lasting health benefits of metabolic flexibility come from your body’s ability to easily switch back and forth between using both fat and glucose for fuel. In doing so, it enables the body to sustain a continuous state of balanced blood sugar.

That’s where all the magic happens.

Balanced blood sugar prevents insulin spikes which reduces the risk of developing insulin resistance. It can help prevent prediabetes and diabetes, obesity, Alzheimer’s, cardiovascular disease, inflammation, and all the risk factors of Metabolic Syndrome.  It may protect you from certain cancers, support brain health, provide consistent energy levels, and help prevent you from making unhealthy food choices to ward off a melt down.

In other words, metabolic flexibility has the potential to protect you from chronic, crippling diseases that contribute to some of the highest mortality rates in the country.

How is that for a “why”?

Progress Not Perfection

The number one rule when making any dietary changes is to listen to your body. I know this sounds contrary to the whole idea of acclimating to IF, but if hunger persists or you are feeling unwell, have a healthy meal or a purposeful snack and try again. What’s important is that as you expand your eating windows, you begin to figure out what is achievable and right for you.

“Progress, not perfection.” It’s a reminder of the need for patience, kindness, and self-love on your journey toward better health.

Comments from my soapbox: Empower and Inspire Change

Two of the most important responsibilities of a functional healthcare provider is to empower and inspire their clients.

Clients are empowered when they are provided with the information they need to take back control of their health. Whether this is by making them aware of available lab testing, effective treatment options, or just explaining body systems and how they work, it’s all done with the intention of increasing their knowledge base. It enables clients to  make their own, informed, decisions with the support of a professional.

Inspiration happens when they connect to their big “why”; to simply feel better or pursue a dream, to live their best life, to be able to play with their children, to see their grandchildren graduate. It’s often the simple things that are most missed when health is lost.  Functional healthcare practitioners recognize the importance of helping clients identify, then support, their “why”.

Ultimately, it’s personal, and that’s the greatest travesty of our current healthcare system. What should be a personal, individual-focused investigation into the root cause of a person’s illness, has turned into a one-size-fits-all, industrialized approach to treating symptoms. It results in the perpetuation of sickness not wellness. It leaves people feeling helpless, hopeless, overlooked, overwhelmed, and powerless.

In my podcast, The Most Important and Often Overlooked Tests for Metabolic Dysfunction, my guest, Annette Falconett tells her story of how misdiagnosed metabolic dysfunction nearly cost her daughter her life and how her own sensitivities to cleaning chemicals resulted in a year spent in bed.

A graduate of the NEPT program (Nutritional Endocrinology Practitioner Training), Annette is one example of many who find themselves alone and sick, trying to find answers to chronic, debilitating health issues. She and her daughter’s journey back to wellness is truly inspirational.

 Annette’s story reminds me, once again, of the profound need to change our broken healthcare system. When it comes to wellness, no one should be alone, frightened, and fighting for answers.

I’m passionate and adamant about the key role functional healthcare practitioners will play in facilitating this change.  With each success, empowering and inspiring people to take back control of their health, it demonstrates there is a better way. I hope you will join me.

Did you know?

A keto diet heavy on animal fats is not for everyone. It’s important to know there are many ways in which to reach ketosis, including a plant-based keto diet.

Fasting While Feasting and the Healthy Keto Challenge are two programs in which  people learn how to effectively achieve ketosis using healthy plant fats like those found in avocados, nuts, and seeds.

There are many ways in which a person can become fat-adapted and achieve metabolic flexibility.  Always listen to your body and be sure it is in line with you and your client’s health goals.


Mark Sisson on Achieving Metabolic Flexibility Through Fasting – YouTube

Intermittent Fasting 101 — The Ultimate Beginner’s Guide

Research on intermittent fasting shows health benefits | National Institute on Aging

Metabolic Flexibility: Everything You Need to Know to Get Started

Metabolic Flexibility as an Adaptation to Energy Resources and Requirements in Health and Disease | Endocrine Reviews | Oxford Academic

What is keto flu? – Harvard Health

Hypoglycemia – Symptoms and causes – Mayo Clinic

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Medical Disclaimer: The information on this website is not intended to replace a one-on-one relationship with a qualified health care professional and is not intended as medical advice. It is intended as a sharing of knowledge and information from the research and experience of Dr. Ritamarie Loscalzo, drritamarie.com, and the experts who have contributed. We encourage you to make your own health care decisions based upon your research and in partnership with a qualified health care professional.

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