Why Low-Carb Diets Can Hurt Your Body’s Ability to Use Carbs: Insights on Glycogen and Athletic Performance

Learn how your body adapts to low-carb diets and why it matters for your athletic performance. Discover expert advice from Antonio Squillante on fueling your body for maximum energy and endurance!

Why Low-Carb Diets Can Hurt Your Body’s Ability to Use Carbs / Everyday Warrior Nation

In our recent podcast episode, we spoke with Antonio Squillante, Head of Sport Performance and Training at USA Cycling’s Sprint Program, about glycogen metabolism and what can happen when the body loses its ability to effectively break down and use stored glycogen. This process, essential for energy in athletic performance, can be affected by dietary choices, particularly when carbohydrates are restricted. Squillante shared his insights into the mechanisms behind glycogen breakdown and how the body’s enzyme production adapts based on dietary demands.

Glycogen is the storage form of glucose, a sugar that muscles use as a primary energy source during high-intensity activities. When we eat carbohydrates, they are broken down into glucose and enter the bloodstream. Glucose is then transported into muscles and stored as glycogen, providing a readily available energy source. This process is crucial for athletes who need fast-access fuel for sprinting, lifting, or other high-intensity efforts.

To release this stored energy, the body relies on enzymes to break down glycogen back into glucose. Squillante explained, “One glycogen, actually glucose, is taken out from your bloodstream, put into your muscles, and stored as glycogen. You need enzymes to be able to break down that glycogen... and use it.” Without these enzymes, glycogen remains stored and inaccessible, leading to energy shortages during intense activity.

Enzymes, like many physiological processes in the body, adapt to the demands, or lack thereof placed upon them. According to Squillante, when you follow a low-carbohydrate or ketogenic diet for an extended period, the body downregulates, or reduces, the enzymes needed to break down glycogen effectively. This adaptation makes sense biologically: if you’re not consuming or relying on carbohydrates for energy, the body sees less need to maintain high levels of glycogen-processing enzymes.

“When you condition your body to stay without those enzymes because you don’t need those carbohydrates anymore, you’re simply gonna lose the ability to break down glycogen effectively,” Squillante noted. This adaptation means that if you try to reintroduce carbohydrates after a long period of restriction, your body may struggle to process them efficiently, leading to issues like digestive discomfort and reduced carbohydrate metabolism.

Beyond enzymes, another factor impacting carbohydrate processing is the gut microbiome. Squillante mentioned that a prolonged absence of carbohydrates in the diet can lead to changes in the gut microbiome, the community of microorganisms that help digest food. Some of these microorganisms are specifically involved in breaking down carbohydrates and aiding glycogen metabolism. Without regular carbohydrate intake, the population of these microbes can diminish, further reducing your body’s ability to digest and absorb carbs effectively.

This is why athletes who follow a long-term low-carb or ketogenic diet may find it challenging to transition back to a higher-carb intake. The body needs time to rebuild both the enzymes and the gut microbiome required to metabolize carbohydrates efficiently. This adaptation can create a lag in performance while the body readjusts to using glycogen as a primary fuel source.

For athletes, understanding glycogen adaptation has practical implications. Athletes following a low-carb or ketogenic diet should be aware that their bodies will adapt by reducing glycogen-processing enzymes, which can limit their ability to perform high-intensity, glycogen-dependent activities. Here are a few key takeaways:

1. Consider Your Sport’s Energy Demands: Sports that rely heavily on quick, explosive energy may benefit from a steady intake of carbohydrates to maintain glycogen stores and enzyme function.

2. Ease Into Dietary Changes: If you’ve followed a low-carb diet, reintroduce carbohydrates gradually. This will give the body and microbiome time to rebuild the necessary enzymes and microbes for optimal digestion and metabolism.

3. Balance Long-Term Dietary Goals with Performance Needs: While low-carb diets can be beneficial for endurance in some sports, athletes in power or speed-oriented activities may need periodic carbohydrate intake to avoid the long-term downregulation of glycogen-processing enzymes.

Understanding how glycogen metabolism adapts based on diet can help athletes make informed choices that support both their performance and long-term health. By tuning into the body’s needs and adapting diet accordingly, athletes can maintain a balance that fuels their performance at peak levels.