What is Metabolic Flexibility and Why is it Important?

+ Steps you can take to improve your own metabolic flexibility!

Aug 28, 2024

reviewed by Dr. Michael Bollinger, MD

The Power of Metabolic Flexibility

In today’s world, where children and adults get 70 percent or more of their fuel from ultra-processed foods, many people unknowingly suffer from metabolic inflexibility. This condition makes it difficult for the body to switch between burning carbs and fat for energy, leading to a host of health problems, including fatigue, weight gain, and even chronic diseases like diabetes. Metabolic flexibility, on the other hand, is the body’s ability to efficiently switch between fuel sources depending on what’s available. Metabolic flexibility is a sign of a healthy metabolism and is crucial for maintaining steady energy levels, managing weight, and overall well-being. In today’s Wellness Wednesday newsletter, I want to talk about the importance of metabolic flexibility, how to recognize signs of metabolic inflexibility, and how to become more metabolically flexible.

Understanding Metabolic Flexibility

Metabolic flexibility refers to the body’s ability to adapt its energy source based on availability. When you eat a meal rich in carbohydrates, your body should be able to use those carbs for immediate energy. Conversely, during periods of fasting (like during sleep) or low-carb intake, your body should switch to burning fat for fuel. This adaptability is crucial for keeping your energy levels stable, managing your weight, and supporting your overall health.

However, due to our modern diet being high in refined sugars, and refined flour along with sedentary lifestyles, many people’s metabolisms become inflexible. Instead of smoothly switching between fuel sources, their bodies get stuck in a carb-dependent state, which can lead to a variety of health issues.

9 Signs You Are Metabolically Inflexible (carb-dependent)

How can you tell if you’re metabolically inflexible? Here are nine common signs:

You Get “Hangry”: If you feel irritable and shaky when you haven’t eaten, it’s a sign your body is struggling to tap into fat stores for energy.
You Need to Snack Throughout the Day to Maintain Energy: Constant snacking is a red flag that your body relies heavily on carbohydrates and can’t sustain energy without constant refueling.
You Can’t Go More Than 5 Hours Without Eating: If you struggle to go several hours without eating, your body may be too dependent on carbohydrates for energy.
You Feel Sleepy After Eating a Meal: Post-meal drowsiness can indicate that your body is having trouble processing and utilizing the food efficiently or that your meal was too heavy on carbs (even complex carbs), and you would do well to add fat, fiber, and protein to that meal.
You Crave Sweets: Constant sugar cravings suggest that your body is stuck in a carb-dependent state.
You’re Still Hungry After a Meal: If you often feel unsatisfied after eating, your body may not be using the nutrients you consume. It could be that the meal was too high in carbs, and you need to balance with more protein, fiber, and healthy fat.
You Have Insulin Resistance: Insulin resistance is a hallmark of metabolic inflexibility, where your cells don’t respond well to insulin, leading to higher and higher blood sugar levels.
You Have Unintended Weight Gain: Difficulty managing weight, despite efforts to eat well and exercise, can be a sign of metabolic inflexibility.
You’re Often Tired: Fatigue, even after a good night’s sleep, could indicate that your body isn’t efficiently using energy.

Why Is It Important to Be Metabolically Flexible?

Metabolic flexibility is essential for optimal health. Here’s why:

Better Energy Levels: When you’re metabolically flexible, your body can provide steady energy throughout the day, reducing the need for constant snacking or the risk of energy crashes. This continuous energy state is the opposite of “hangry.”
More Endurance: A flexible metabolism allows your body to efficiently use fat as a fuel source during extended periods of exercise, improving endurance.
Improved Insulin Sensitivity: Metabolic flexibility enhances your body’s response to insulin, which can help prevent or reverse insulin resistance and lower your risk of type 2 diabetes.
Improved Fat Burning: When your body can easily switch to burning fat for fuel, it becomes easier to manage weight.
Improved Glucose Processing: Your body can handle glucose more effectively, avoiding spikes and crashes in blood sugar levels.
Food Freedom: You’ll no longer feel the need to constantly eat or snack, giving you more freedom and flexibility with your diet. No more packing your purse, car, and work bag with snacks!

When You Are Metabolically Flexible, You Will:

Use Fat for Energy: Both from the food you eat and from your body fat stores.
Have Longer-Lasting, More Consistent Fuel: Your energy levels will remain stable throughout the day.
Find Fat Loss Easier: Burning fat for fuel helps with weight management and loss.
Have Better Weight Maintenance: Stable energy use leads to better control over your weight.
Have Lower Fasting Blood Sugar: Improved insulin sensitivity results in lower fasting blood sugar levels.
Have Consistent Energy Throughout the Day: No more energy crashes or constant hunger.
Have Improved Insulin Sensitivity: This reduces the risk of developing type 2 diabetes.
Reverse Insulin Resistance: Over time, metabolic flexibility can help reverse insulin resistance.
Have Lower Odds of Developing a Metabolic Disease: A flexible metabolism supports overall metabolic health.
Optimize Workout Performance: You can fuel your workouts more effectively, improving performance.
Improve Sleep: Better energy regulation can lead to more restful sleep.

The Science Behind Metabolic Flexibility

Metabolic flexibility is primarily driven by mitochondrial function. Mitochondria are the powerhouses of cells responsible for producing energy. When your mitochondria are healthy and functioning well, they can efficiently switch between burning carbs and fats, depending on what your body needs at the time.

Research published in the journal Cell Metabolism and NIH highlights the importance of mitochondrial health for metabolic flexibility. The study found that individuals with higher mitochondrial efficiency had better metabolic flexibility and were less likely to develop metabolic diseases like type 2 diabetes.

Dr. Ben Bikman, a leading researcher in metabolic health, explains, “Metabolic flexibility is the hallmark of a healthy metabolism. It reflects how well your body can adapt to changes in energy supply and demand, which is crucial for maintaining overall health and preventing metabolic diseases.”

A Gadget that Helps to Improve Metabolic Flexibility

Achieving metabolic flexibility can be challenging, especially if you’re unsure where to start. This is where Lumen comes in. I have been using Lumen on and off for about 2 1/2 years. Lumen is a handheld device that measures your body’s metabolism by analyzing the concentration of CO2 in your breath. It provides real-time insights into whether your body is burning fats or carbs for energy, allowing you to make informed decisions about your diet and lifestyle. I eat mostly low carb, and I use Lumen to help me to know when my body is ready for carbs. By carb cycling in this way, I maintain my metabolic flexibility, and I am able to easily switch between burning fat or carbs for fuel, which keeps my energy levels, mood, weight, and metabolism stable. Take a peak at my IG highlights labeled Lumen to learn more!

Here’s how Lumen works:

Personalized Metabolic Insights: Lumen measures your respiratory exchange ratio (RER), which indicates whether your body is burning more fat or carbohydrates for fuel. You are simply breathing into the Lumen device. Over time, Lumen provides personalized insights into how your body uses different fuel sources, allowing you to make informed decisions about your diet and lifestyle to improve metabolic flexibility.
Customized Nutrition Recommendations: Based on your metabolic data, Lumen offers tailored nutrition recommendations to help you optimize your metabolic flexibility. For example, if Lumen detects that you’re primarily burning carbs, it might suggest increasing healthy fat intake and reducing carbs to encourage fat utilization. Lumen is like having a pocket nutritionist!
Daily Tracking and Feedback: Lumen allows you to track your metabolism daily, giving you immediate feedback on how your diet and lifestyle choices affect your metabolic flexibility. This real-time feedback helps you adjust your habits to achieve better metabolic balance.
Supporting Weight Loss and Energy Management: By helping you understand when your body is in fat-burning mode versus carb-burning mode, Lumen can guide you in making dietary choices that support weight loss and stable energy levels.

How to Increase Metabolic Flexibility in 9 Steps

If you want to improve your metabolic flexibility, consider incorporating the following steps into your daily routine:

Start Your Day with Protein: Aim for 20-40 grams of protein per meal to support muscle health and satiety. Use this calculator to help you figure out your protein needs.
Shorten Your Feeding Window: Fast for 12-16 hours at night to give your digestive system a break and promote fat burning. For women still in their fertile years, 12 hours is safe. For women in peri-menopause and menopause and most men, 14-16 hours can be very beneficial.
Stop Snacking Between Meals: Focus on eating 2-3 satisfying meals daily to reduce the need for constant snacking.
Eat 2-3 Meals to Satiety: Ensure you’re eating enough at meals to avoid hunger between meals.
Walk 8-10,000 Steps a Day: Regular movement supports metabolic health and fat burning.
Incorporate Zone 2 Exercise: Engage in moderate-intensity exercise 2-3 times a week to enhance fat utilization. A simplified definition of Zone 2: if someone were to call you on the phone when you are engaged in Zone 2 exercise, they would know you were doing something to increase your heart rate. You can speak, but will be slightly winded.
Strength Train 2-3 Times a Week: Build muscle mass, which improves your body’s ability to burn fat and can improve glucose utilization which can help with insulin resistance.
Eat a Low-Carb Diet: Prioritize protein, fiber, and healthy fats while reducing carbohydrate intake to promote fat burning.
Keep Blood Sugar Stable: Focus on whole foods that don’t spike your blood sugar levels, supporting overall metabolic health. This could mean using a continuous glucose monitor (CGM) to determine what foods spike your blood sugar. Everyone is different and this information can be very valuable for increasing metabolic flexibility.

Expert Opinions on Metabolic Flexibility

Many experts in metabolic health recognize the importance of metabolic flexibility.

Dr. Casey Means, a physician and co-founder of the glucose monitoring company Levels, emphasizes the value of understanding metabolic flexibility in her book Good Energy: Metabolic flexibility is key to overall health and longevity.

Dr. Jason Fung, a nephrologist and expert on intermittent fasting, also highlights the role of metabolic flexibility in health and disease prevention. He says that the ability to switch between fuel sources efficiently is essential for preventing insulin resistance and managing chronic conditions.

Winding Up

Metabolic flexibility is a cornerstone of good health, influencing everything from your energy levels to your risk of chronic disease. You can support your overall well-being by understanding the signs of metabolic inflexibility and taking steps to improve it. I hope this newsletter gives you some ideas for where to begin. If you need guidance or have questions, I am always happy to help.

Lumen

The Lumen Labor Day Sale is live and the device is just $199. This is the best price it's been all year. My coupon code works on top of the discounted price, making Lumen just $179. Use code BETHB if you decide to order.

Lumen helps uncover the hidden connections between your lifestyle and your metabolic health, so you can focus on the changes that have the most impact for you.
Burning fat 100% of the time is not the goal, nor is it a marker of a healthy metabolism. As a rule, you should burn fat during rest and fasting, and carbs during intense or sudden energy bursts.

Continuous Glucose Monitor (CGM)

Learn how food, sleep, exercise, and stress affect your blood sugar levels. Learn how adding healthy fat, fiber, and protein to a meal helps to reduce blood sugar spikes. Figure out which complex carbs your body likes best! I may be able to eat a sweet potato without a blood sugar spike and crash, but maybe you do better with 1/2 sweet potato or a white or purple potato instead. I have been wearing a CGM for 3 years on and off to create recipes for level blood sugar and I have learned so much. I highly recommend everyone try a CGM, even for a couple months.

Books

I know I have shared Good Energy before, but it really is an excellent resource for improving metabolic flexibility and aging well. “As Dr. Casey Means explains in this groundbreaking book, nearly every health problem we face can be explained by how well the cells in our body create and use energy.”

Podcasts

If you want to learn more and dive into a little bit of the science of metabolic flexibilty, check out this podcast!

Join Beth Bollinger’s subscriber chat

Available in the Substack app and on web

Supplements

I have created many protocols in Fullscript, and you can access them all by creating an account. I offer 20% off on all practitioner-grade supplements, protein powders, collagen, and personal care products. Metabolic Health + Blood Sugar Support is a protocol designed to help with blood sugar balance and metabolic health in conjunction with a healthy, balanced diet.

Thank you🧡

I have been sharing blood sugar-friendly, whole-food recipes (gluten-free, refined sugar-free, and mostly dairy-free) without ads on my blog and Instagram for four years now, and I have met so many amazing people along the way. I am excited to share this enhanced user experience (with recipe videos!) on this platform, and I am so grateful you have joined me!

P.S.

If you know anyone with pre-diabetes, diabetes, PCOS, metabolic syndrome, or anyone eating for blood sugar balance, low carb, keto, grain-free, gluten-free, or just eating for better health, will you forward my Substack to them? It would mean the world to me as I try to share the message of eating for good metabolic health.

🧡Beth

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