What is the Difference Between Ketosis and Ketogenesis

The main difference between ketosis and ketogenesis is that ketosis is a metabolic state characterized by detectable ketone levels, whereas ketogenesis is the biochemical process of generating ketones. 

Ketosis and ketogenesis are two processes that generate ketones in the body. They occur in the absence of carbohydrates to burn for energy.     

Key Areas Covered

1. What is Ketosis
– Definition, Facts, Features
2. What is Ketogenesis
– Definition, Facts, Features
3. Similarities Between Ketosis and Ketogenesis
– Outline of Common Features
4. Difference Between Ketosis and Ketogenesis
– Comparison of Key Differences

Key Terms 

Ketogenesis, Ketosis

What is Ketosis

Ketosis is a metabolic state that arises due to the metabolism of fat instead of carbs. Carbohydrates provide glucose, which serves as the primary fuel to the metabolizing tissues of the body. When adequate amounts of glucose are unavailable for the tissues, the body tends to use fat instead of glucose. Fat burning occurs in a low-carb diet that contains restricted levels of glucose.

Figure 1: Ketones: Acetone, Acetoacetic Acid, Beta-Hydroxybutyric Acid

Furthermore, burning fat releases fatty acids into the blood, which are transported to the liver to oxidize. The oxidized fatty acids are converted into ketones, which can then be used as an energy fuel. Some people believe ketosis is dangerous since the brain does not get enough glucose to work. But, under low glucose conditions, the liver carries out another process called gluconeogenesis, which produces an adequate amount of glucose required for brain function. 

What is Ketogenesis

Ketogenesis is the biochemical pathway that produces ketones as an alternative form of energy. By breaking down fatty acids, our body produces ketones, including acetone, acetoacetate, and beta-hydroxybutyrate molecules. Ketones contain two R groups attached to the carboxyl carbon. They are water-soluble lipid molecules. Therefore, they do not need lipoproteins for transportation. Our body continually produces a small number of ketones. But it increases the times of fasting. Also, a significant decrease in carbohydrates and an increase in fatty acids upregulate the ketogenic pathway. Apart from starvation, ketogenesis occurs in type I diabetes and alcoholism.

Figure 2: Ketogenesis

Primarily, ketogenesis occurs in the mitochondria of liver cells. Fatty acids undergo beta oxidation for the production of acetyl-CoA. Thiolase converts two acetyl-CoA molecules into acetoacetyl CoA, which is then converted into HMG CoA via HMG CoA synthase. Further, HMG CoA converts into acetoacetate by the action of HMG CoA lyase. It can convert into acetone through non-enzymatic decarboxylation. It can also convert into beta-hydroxybutyrate via beta-hydroxybutyrate dehydrogenase. Beta-hydroxybutyrate converts into acetoacetate by the enzyme beta-hydroxybutyrate dehydrogenase in the extrahepatic tissues. Also, acetoacetate converts into acetyl CoA via the enzyme beta-ketoacyl-CoA transferase, entering the citric acid cycle. 

Similarities Between Ketosis and Ketogenesis

• Ketosis and ketogenesis are two processes that produce ketones in the absence of carbohydrates for energy production.
• They burn fats to produce ketones.
• Ketones are converted into acetyl-CoA that enters into the citric acid cycle. 

Difference Between Ketosis and Ketogenesis

Definition

Ketosis refers to a metabolic state occurring when the body burns fat for energy instead of glucose. At the same time, ketogenesis refers to a metabolic pathway that produces ketone bodies, which provide an alternative form of energy for the body.

Correspondence

Ketosis is a metabolic state producing ketones, while ketogenesis is the biochemical pathway that produces ketones.

Occurrence

Ketosis generates low levels of ketones in the blood, while ketogenesis occurs in the liver.  

Conclusion

In brief, ketosis and ketoacidosis are two processes that produce ketones without carbohydrates as the energy source. Importantly, ketosis is a metabolic state that produces low levels of ketones in the blood. In comparison, ketoacidosis is the biochemical reaction that occurs in the liver. Therefore, the main difference between ketosis and ketogenesis is their correspondence. 

References:

1. Dhillon KK, Gupta S. Biochemistry, Ketogenesis. [Updated 2023 Feb 6]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2023 Jan-.

Image Courtesy:

1. “Ketone bodies” By Edgar181 – Own work (Public Domain) via Commons Wikimedia
2. “Ketogenesis” By Sav vas – Own Work (CC0) via Commons Wikimedia