You can burn fat without making ketones

The Role of Oxaloacetate in Fat Metabolism: Burning Fat Without Making Ketones

Written by Veronique @ Our Low Carb Life Clinic

Our patients often feel concerned when they eat a low carbohydrate diet but don't make high levels of ketones.

While ketones are a signal you are burning fat for fuel, not having high ketones does not mean you're not burning fat. To understand this, we need to dig into a bit of biochem and understand how (and why) our body makes ketones.

The Citric Acid Cycle

(Also known as the Krebs cycle or the tricarboxylic acid (TCA) cycle)

The citric acid cycle is a series of chemical reactions in the body that are essential for the metabolic breakdown of carbohydrates, fats, and proteins to produce energy. In the citric acid cycle, oxaloacetate plays a critical role in determining whether we burn ketones or fatty acids for energy.

Introducing Oxaloacetate

When it comes to our bodies' ability to burn fat for energy, there's a key player that often goes overlooked: oxaloacetate. This molecule is involved in the metabolism of carbohydrates and fats and has a significant impact on whether we burn ketones or fatty acids for energy.

Graphic Credit: Khan Academy.

Khan Academy - Citric Acid Cycle

Making oxaloacetate

When we consume food that contains carbohydrates, the carbohydrates are broken down into glucose, which can be used as an energy source. The glucose is converted into pyruvate, which then enters the citric acid cycle and is converted into oxaloacetate. We can also generate oxaloacetate from the amino acids from protein.

Oxaloacetate is used to generate energy through the citric acid cycle, which produces ATP. The citric acid cycle is a key part of cellular respiration, which is the process by which cells produce energy from the food we eat. In the citric acid cycle, the oxaloacetate reacts with acetyl-CoA to produce energy-rich molecules like ATP, which can then be used by the cells to power their various functions.

Burning Fat

However, if there is a shortage of carbohydrates or glucose, the body will begin to break down fats into fatty acids, which can also be used as an energy source. The fatty acids are converted into a molecule called acetyl-CoA, which enters the citric acid cycle and is converted into oxaloacetate.

When the body doesn't have enough oxaloacetate to process all of the acetyl-CoA produced from the breakdown of fats, the excess acetyl-CoA is converted into ketone bodies, which can be used as an energy source when glucose is not available. This is why people who follow a low-carbohydrate diet often see an increase in the production of ketones in their bodies.

When oxaloacetate is limited, we make ketones because we are not able to burn fat or carbohydrates. Just because you're not making ketones, does not mean you're not burning fat!

We make ketones when oxaloacete is low.

It's important to note that just because you're not making ketones doesn't mean you're not burning fat. If we add extra protein to our diet, this increases the amount of glucose produced through gluconeogenesis, which in turn increases the amount of oxaloacetate available. This means that the body is able to burn more fatty acids for energy without having to make ketones, because there is enough oxaloacetate to process all of the acetyl-CoA produced from the breakdown of fats.

In conclusion, oxaloacetate plays a critical role in determining whether we burn ketones or fatty acids for energy. When oxaloacetate is limited, we make ketones because we can't burn fat or carbohydrates. But when we add extra protein to our diet, we increase the amount of oxaloacetate, allowing us to burn fat without making ketones. So next time you're considering a low-carbohydrate diet, remember that just because you're not making ketones doesn't mean you're not burning fat!

Remember

You can be burning fat, without making ketones.

Summary

Oxaloacetate is a key player in the metabolic process that determines whether our bodies burn ketones or fatty acids for energy.
When there's a shortage of carbohydrates or glucose, the body begins to break down fats into fatty acids, which can be converted into ketone bodies if there's not enough oxaloacetate to process them.
However, adding extra protein to our diet can increase the amount of oxaloacetate and allow the body to burn more fatty acids without making ketones.
You can be burning fat without making ketones

Questions? Just reach out, we love to chat!

- Our Low Carb Life Clinic

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