The Hidden Health Benefit of Carbohydrates

Metabolic flexibility is the body’s ability to efficiently switch between using carbohydrates and fats as a fuel source based on availability and energy demands. A metabolically flexible person can burn carbs when they’re plentiful (e.g., after a meal) and shift to fat oxidation when carbs are scarce (e.g., during an overnight fast, between meals, etc.).

Good metabolic flexibility is associated with better insulin sensitivity, stable energy levels, and efficient fat metabolism. Poor metabolic flexibility, often seen in conditions like insulin resistance or metabolic syndrome, means the body struggles to switch between fuel sources, leading to sluggish energy production, poor blood sugar regulation, difficulty burning fat, and higher rates of fat storage.

But how do you actually achieve metabolic flexibility? Restoring metabolic flexibility involves relearning how to properly utilize carbohydrates — not avoiding them! It is ironic that low-carb proponents claim that avoiding carbohydrates improves metabolic flexibility when, in reality, it does the exact opposite.

Prolonged carbohydrate restriction induces a state of insulin resistance, making it harder to efficiently metabolize carbohydrates when they are reintroduced.

When carbohydrates are consumed, the body doesn’t just burn carbs all day; at some point, fat metabolism is utilized — whether that’s body fat or dietary fat. You are never ‘just burning carbs’ or ‘just burning fat’ — there is always some amount of each going on. For example, your muscles sitting at rest are using fat for fuel, and your brain reading this article is using carbs as fuel.

But true metabolic flexibility allows seamless switching between these two fuel sources as needed. One crucial but often overlooked fact is that relearning how to efficiently burn carbohydrates enhances the body’s ability to burn fat, highlighting the essential role of carbs in optimizing metabolism. Restoring metabolism is almost synonymous with relearning how to properly utilize carbohydrates.

Metabolism and Electron Flow

Albert Szent-Györgyi once said, “Life as we know it is nothing but a movement of electrons.” The food we consume is filled with energized electrons, and metabolism is about harnessing these high-energy electrons to generate ATP, the body’s primary energy currency.

These electrons are transferred into the mitochondria using electron carriers, where they move through the electron transport chain to oxygen, the final electron acceptor. When this process is efficient and unobstructed by ‘metabolic brakes,’ the body produces maximum energy, supporting all cellular functions and overall health.

When electrons cannot flow properly, they accumulate, leading to reductive stress, which impairs cellular function. Efficient electron flow through the electron transport chain maximizes ATP production and maintains metabolic health.

Inside our cells, electrons don’t flow on wires, they require electron carriers. Think of it like taxis picking up a pedestrian at a corner (electron) to take them to their destination.

Oxygen availability and the abundance of electron carriers like NAD⁺ are key limiting factors for metabolism. Oxygen, as the final electron acceptor in the mitochondrial electron transport chain, is essential for ATP production, while higher NAD⁺ levels enable greater electron transport, further enhancing energy generation.

Clearly, oxygen availability is vital for metabolism. But what is not commonly understood is how oxygen gets to our cells, a process reliant on carbon dioxide (CO₂).

The Relationship Between O₂ and CO₂

CO₂ is often labeled a ‘byproduct’ of energy metabolism, but it plays a vital role in oxygen delivery! There is a crucial relationship between oxygen and carbon dioxide.

More CO₂ enhances oxygen delivery to cells, improving energy production. This sets up a feedforward cycle, as better energy production leads to more CO₂ generation, which improves oxygen availability, which improves electron flow and increases energy production! The relationship between O₂ and CO₂ is explained by the Bohr and Haldane effects:¹

• Bohr effect — High CO₂ concentration in the cells lowers pH, causing hemoglobin to unload more O₂ into the tissues and take up CO₂.
• Haldane effect — High O₂ concentration in the lungs causes hemoglobin to release CO₂ and take up oxygen.

The higher the concentration of CO₂, the more effectively oxygen can be utilized, leading to improved metabolism and energy production. Well, proper oxidation of carbohydrates produces 50% more CO₂ than fat oxidation.^2,3

(Meaning, you produce 50% more CO₂ when you properly burn carbs relative to fat oxidation! Relying more on fat oxidation will lower CO₂ levels.)

“Higher CO₂ has benefits, and a higher ratio of carbohydrates to fat being oxidized for fuel yields greater CO₂.”⁴

This increased intracellular CO₂ enhances oxygen delivery via the Bohr effect, allowing for better metabolic function, including fat oxidation when fat burning is needed. Since fat metabolism requires more oxygen to generate ATP compared to carbohydrates, having an efficient carb-burning metabolism indirectly supports fat oxidation by optimizing oxygen availability.

Properly metabolizing carbohydrates boosts NAD⁺ levels, increasing the availability of electron carriers to efficiently shuttle electrons throughout the body. This enhances electron flow and metabolic rate while reducing reductive stress.

When glucose is metabolized effectively, NADH donates electrons to Complex I of the electron transport chain (ETC), regenerating NAD⁺ levels. This process is vital because NAD⁺ is essential for the efficient oxidation of both carbohydrates and fats. In particular, fat oxidation relies heavily on sufficient NAD⁺ and oxygen availability.

How Does Our Body Break Down Carbohydrates?

Let’s take a quick moment to discuss what it means to properly burn carbohydrates — this is crucial to understand! Cells generate energy through aerobic (with oxygen) or anaerobic (without oxygen) respiration, depending on oxygen availability.

In aerobic respiration, electrons enter the mitochondria, driving the production of significantly more ATP along with CO₂, a byproduct that enhances oxygen delivery. This is the preferred pathway since we get more of the health promoting compounds, and less of the problematic compounds.

For optimal ATP production, oxygen must be available to act as the final electron acceptor in the mitochondrial electron transport chain (ETC). This ensures continuous electron flow, maintains a strong electrochemical gradient, and maximizes energy output.

In contrast, when oxygen is limited, cells rely more on anaerobic glycolysis (also called anaerobic fermentation). In this process, electrons do not enter the mitochondria, ATP production is significantly lower (only 2 ATP vs. 32 to 38), and no CO₂ is generated.

While glycolysis is always active to some extent, it becomes the dominant pathway under low-oxygen conditions, leading to a less efficient energy production system.

Why Some People Struggle to Burn Carbohydrates Efficiently

Individuals who struggle with carbohydrate metabolism often rely primarily on glycolysis, stopping short before reaching the ETC. As a result, they fail to fully oxidize carbohydrates and instead depend more on excessive fatty acid oxidation.

But avoiding carbs doesn’t fix the problem (low oxygen availability, fuel competition with too much fat, and reductive stress). Think of it like skipping leg day because of leg pain — avoiding the issue and not going to the gym to hit lower body might provide relief, but it doesn’t address the root cause of why there is leg pain.

When carbohydrate intake is reduced, pyruvate dehydrogenase (PDH) — one of the key enzymes that facilitates carb oxidation⁵ — becomes less active. This limits glucose oxidation,⁶ leading to an accumulation of electrons and increased reductive stress (a low NAD⁺/NADH ratio).

Additionally, PDH activity is suppressed by high dietary fat intake. Research shows that just 24 hours on a high-fat, low-carb diet can decrease PDH activity in human skeletal muscle.⁷ This disrupts efficient electron transfer, reduces ATP production, impairs metabolism, and further increases reductive stress.

In individuals with metabolic dysfunction, mitochondria become overloaded with electrons, leading to a buildup of NADH (the electron-carrying form of NAD⁺). Since NADH must donate its electrons before converting back to NAD⁺, an excess of NADH and a shortage of NAD⁺ create an energy bottleneck.

(NADH is NAD⁺ with an electron attached, meaning it is ‘full’ and can’t accept any more electrons. NADH needs to bring the electron somewhere before it is converted back to NAD⁺ and can ‘pick up’ more electrons!)

So no, removing carbohydrates does not fix carb metabolism since a low-carb state can lead to a lower NAD⁺/NADH ratio (reductive stress), which inhibits PDH,⁸ slows glucose oxidation and shifts the body toward greater reliance on fatty acid oxidation.

Without sufficient NAD⁺ to support electron transport, metabolism becomes inefficient, slowing both carbohydrate and fat utilization.

In contrast, efficient glucose oxidation increases NAD⁺, enhancing metabolic rate, ATP production, and CO₂ output. Since CO₂ improves oxygen delivery, this creates a positive feedback loop, further supporting efficient metabolism.

Interestingly, one of the key characteristics of obesity is a reduced ability to efficiently metabolize glucose.⁹ Research indicates that low NAD⁺ levels and elevated NADH levels (reductive stress) are common in both obesity and diabetes.^10,11,12 As a result, individuals with obesity often rely more on fat oxidation than on carbohydrate metabolism.

Additional Benefits of Carbon Dioxide

Beyond its role in oxygen delivery, CO₂ has numerous other health benefits that are upregulated with proper carbohydrate utilization.

How to Increase CO₂ Levels

CO₂ levels in the body are influenced by diet and breathing patterns. Since carbohydrates generate more CO₂ than fats, efficient carb oxidation increases CO₂ production. Research indicates that ketosis significantly reduces CO₂ stores, impairing metabolism.

Mouth breathing can deplete CO₂ levels, while nasal breathing preserves CO₂ and enhances oxygen utilization. Simple interventions like mouth taping during sleep or practicing controlled breathing exercises (such as bag breathing) can help maintain optimal CO₂ levels.

To Summarize

Understanding the role of CO₂ in metabolism highlights the importance of proper carbohydrate metabolism for optimal health. The better the body metabolizes carbs, the more CO₂ is produced, enhancing oxygen delivery, supporting metabolic function, and improving overall energy production.

Rather than avoiding carbohydrates, focusing on improving carb utilization can significantly enhance metabolic flexibility, energy levels, and, coincidentally, fat metabolism. CO₂ is not merely a byproduct of metabolism — it is a critical molecule for maintaining optimal physiological function. By ensuring efficient carbohydrate metabolism, we can harness CO₂’s benefits and support overall health.

Practical Steps to Improve Carb Metabolism and CO₂ Levels

Prioritize whole-food carbohydrate sources (fruits, roots, honey, dairy, properly prepared grains. Packaged food, baked goods, and pizza are not ‘carb sources’ — in fact, they often contain more calories from fat than they do carbs!)

Dietary fat is not bad! Fats are good for our health! But be mindful of the total amount (you don’t have to go crazy overboard to experience the benefits), and the type since we want to prioritize fats higher in saturated fat to optimize metabolic function

Avoid prolonged carbohydrate restriction to maintain metabolic flexibility

Incorporate daily movement and activity, plus strength training 2 to 3 times per week, to support proper glucose utilization

Practice nasal breathing and controlled breathwork to enhance CO₂ retention

Ensure adequate nutrient intake (B vitamins, magnesium) to support carbohydrate metabolism

To Learn More About Relearning How to Better Utilize Carbs, Join Rooted in Resilience

If you need help improving your ability to utilize and properly burn carbohydrates, we teach you exactly how to do this in our course, Rooted in Resilience. Here’s just a snapshot of what you’ll learn in the course …

How to heal your metabolism and improve glucose utilization to help you attain your ideal weight and body composition

Clear the confusion on what food we should actually be eating

Use reverse dieting to increase your calories without gaining weight while improving your energy levels

How to actually lose weight in a way that doesn’t tank your metabolism (a complete weight loss guide) and avoid weight loss plateaus

How many calories you should be eating, and what macronutrient composition (how many carbs, fat and protein you should be eating right now)

How to finally heal your gut so that you can start eating more foods

How to master the most essential healthy habits, including over 100 meal plans to help make it easier to implement these principles into your busy life and so much more!

Learn more about Rooted in Resilience here.

About the Author

Ashley Armstrong is passionate about helping educate and inspire others to improve their metabolic health. She and her sister run the “Strong Sistas” social media account, and a podcast channel ‘Rooted in Resilience’ available on YouTube, Spotify and iTunes. Plus, they have free information and courses on their website centered around improving metabolism.

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