High-carb diets and excess calories are well-established, well-studied contributors to insulin resistance. But researchers are also investigating a newer angle: what happens when your cells simply can’t burn fat efficiently, and what that has to do with how well they handle everything else. (Based on the insights of Thomas DeLauer)
Key Takeaways
- An emerging hypothesis suggests impaired fat oxidation, not just glucose handling, may contribute to insulin resistance.
- A rodent study found trans fats were broken down far less efficiently than other fats by a key oxidation enzyme, leading to oxidative stress and impaired insulin signaling.
- Combining large amounts of fat and carbohydrate in one sitting may create a metabolic “gridlock,” particularly for people already dealing with insulin resistance.
- Replacing some carbohydrate with protein in a meal has been shown in research to increase fatty acid oxidation for the rest of the day.
- This is an evolving hypothesis, not settled science — the fundamentals of calorie balance and carbohydrate quality remain the strongest-supported factors in insulin resistance.
What Happens When Cells Can’t Burn Fat Properly
A hypothesis discussed in recent research proposes that when fat oxidation is impaired inside a cell, byproducts build up that interfere with the cell’s ability to respond to insulin. In other words, insulin resistance isn’t only about how well cells handle glucose — it can also stem from how well they handle fat.
This traces back to a rodent study that compared how different fats were broken down. Two fats — oleic acid and stearic acid — were broken down efficiently by an enzyme responsible for the first step of fat oxidation. A trans fat, by contrast, wasn’t broken down efficiently by that same enzyme. That inefficient breakdown led to a buildup of fat components inside the cell membrane, creating oxidative stress and, in turn, impairing insulin signaling. In short: the trans fat didn’t just fail to provide clean fuel — its poor breakdown actively made the cell worse at handling fuel overall.
Why This Matters More When Fats and Carbs Are Combined
Separate research has described a concept sometimes called “metabolic gridlock.” Cells generally switch between burning fat and burning carbohydrate rather than using both simultaneously — a healthy metabolism switches between the two fairly quickly, while a less healthy one struggles to make that switch efficiently. When large