Debunking the Myth: Can Low-Carb Diets Impair Your Ability to Process Carbs?

In a recent live session with our Insulin IQ Certified Coaches, I received a question from Coach Carrie that I believe deserves some thorough clarification.

Carrie asked, “Some say that eating low-carb for a long while will cause your body to not be able to process healthy carbs eventually. Is there any truth to that?”

The simple answer is no, there’s absolutely no truth to that claim. Let me explain where this misconception might come from and why it’s not reflective of how the body actually works.

There is evidence that suggests the body can become acutely glucose intolerant on a low-carb or ketogenic diet, but this has been misunderstood—and sometimes even weaponized—either out of ignorance or malice. Here’s what’s really happening: the body remains highly insulin-sensitive on a low-carb diet. However, glucose intolerance—which is different from insulin resistance—can occur temporarily, particularly after fasting or eating very few carbs for an extended period.

To illustrate, let’s consider the two phases of insulin secretion. When glucose enters the bloodstream, the beta cells in the pancreas respond by releasing insulin in two phases. The first phase is the release of preformed insulin—the insulin that’s already on hand and ready to go. The second phase involves producing new insulin from scratch, depending on the ongoing glucose levels. If glucose intake is consistently low, the beta cells recognize that they don’t need to store as much insulin. Through a process called autophagy, they break down the excess insulin.

This process happens surprisingly quickly—sometimes within 16 to 24 hours of fasting. When someone who has been fasting or eating low-carb suddenly consumes a large amount of glucose, the beta cells are caught off guard. They don’t have enough preformed insulin stored to manage the sudden glucose spike, leading to a temporary delay in glucose clearance. Clinicians might misinterpret this as glucose intolerance, but it’s simply the beta cells playing catch-up.

Now, if you’re preparing for an oral glucose tolerance test—perhaps for pregnancy screening or another medical reason—it’s important to give your beta cells a heads-up. Eating some carbs the day before the test can stimulate the beta cells to restock their insulin supply, ensuring a smoother response when glucose levels spike.

So, to those who claim that a low-carb diet impairs your ability to metabolize carbohydrates: it’s simply not true. The body remains exceptionally insulin-sensitive on a low-carb diet. While there may be a brief delay in clearing glucose the first time, the body quickly adapts. The idea that a low-carb diet damages your ability to process carbs is nothing more than a myth.

I hope this clears things up. Remember, metabolic health is nuanced, and understanding these details helps us separate fact from fiction.

Sincerely,

Ben