What Is Metabolic Flexibility? Why You Need and Want It

Want to know more about metabolic flexibility and impaired metabolic flexibility? Read on for explanations of both.

people in a yoga class with their hands in prayer

We all know that girl or guy who can eat velvety twirls of pasta carbonara, gooey cinnamon rolls dripping with vanilla icing, and gargantuan burritos stuffed with guacamole, fries, and steak but never seems to gain weight. Rather than throw green monster side-eye shade at him or her, consider why this can happen. It's because that person has metabolic flexibility.

He may be young and sporty with a “fast” metabolism. She may be a long-distance runner who eats calorically dense foods to fuel her demanding training schedule. But what explains this concept from a physiological perspective? 

Metabolic flexibility describes the ability to adapt the demand for fuel with what’s available. A metabolically flexible person can switch between burning carbs or using fat as an energy source to fuel everyday tasks, exercise, or merely to think and breathe. 

What Is Impaired Metabolic Flexibility?

Impaired metabolic flexibility implies the inability to use fats stored in muscle cells for fuel. If your body can’t burn the excess glucose (stored as fat) in your muscle cells but you have a large fat supply in your body, you’ll continue to store fat you can’t burn, leading to insulin resistance <sup>1</sup>. Over time, insulin resistance can lead to obesity and prediabetes<sup>2</sup>.

Why You Need Metabolic Flexibility

Who doesn’t want to be able to stress less about how many carbs they eat? Metabolic flexibility provides exactly what it promises—flexibility and freedom from diet micromanagement.

  • Metabolically flexible people can tap into different fuel sources to power activity without difficulty. Going for a morning run? That mushroom farro you ate for dinner last night will provide the glucose you need. Don’t have time to eat breakfast and don’t feel hungry anyway? No problem, the glucose stored in your muscles will fuel your activities until you get hungry and decide to eat.
  • Metabolic flexibility implies optimal mitochondrial function. The powerhouses of cells, mitochondria make energy for the cells from the food we eat. Mitochondrial dysfunction is shown to be a precursor to the onset of chronic diseases indicated by the inability to match fuel preference (glucose first if available, fat second) to demand(3). If your mitochondria struggle to function properly, you likely store excess energy that your body doesn’t burn. This difficulty in burning fat leads to weight gain, insulin resistance, and chronic health problems associated with metabolic disorders.

So does this mean you can eat all of the carbs and “get away with it” if you have metabolic flexibility? Sorry to disappoint. 

Metabolic flexibility is a state to strive for as a sign of a healthy, high-functioning body. Enjoying roasted chickpeas on a salad or sinking your fork into a puddle of mashed sweet potatoes and using the glucose to power an evening walk should be the goal. Prioritize whole-food sources of macronutrients most of the time and that occasional processed treat won’t have such a domino effect on your health. 

<hr class="read-mr">

Related reading: Using Metabolic Workouts to Boost Your Metabolism

Share this article:
Topics discussed in this article:

About the Author

Sabrina Tillman Headshot
Sabrina has more than 20 years of experience writing, editing, and leading content teams in health, fitness, nutrition, and wellness. She is the former managing editor at MyFitnessPal.
View Author Bio

Please note: The Signos team is committed to sharing insightful and actionable health articles that are backed by scientific research, supported by expert reviews, and vetted by experienced health editors. The Signos blog is not intended to diagnose, treat, cure or prevent any disease. If you have or suspect you have a medical problem, promptly contact your professional healthcare provider. Read more about our editorial process and content philosophy here.

Interested in learning more about metabolic health and weight management?

Try Signos.
Buy Now
A white woman leaning back on a rowing machine with his arms bent and holding the bar to his chest.
Get started with Signos
A boy is on his dad's back with his arms around his shoulders. The dad is on all fours, extending his right leg behind him, and is wearing a CGM with Signos sports cover on his left arm.
A white woman leaning back on a rowing machine with his arms bent and holding the bar to his chest.
Sign up now
< More
Signos 101
Articles