What Is Gluconeogenesis?
Summary
Gluconeogenesis is the metabolic process by which the body creates glucose from non-carbohydrate sources such as protein and certain fats. This built-in system allows the body to maintain stable blood sugar levels without requiring dietary carbohydrates. Dr. Berg explains that because of this process, carbohydrates are not an essential dietary requirement.
Key Takeaways
- Gluconeogenesis literally means “making new glucose” — gluco (glucose) + neo (new) + genesis (create).
- The body can produce glucose from protein and certain lipids (specifically triglycerides).
- The primary purpose of gluconeogenesis is to prevent hypoglycemia (low blood sugar).
- It helps maintain stable blood sugar levels between meals and during fasting.
- Nearly all cells in the body can run on ketones as an alternative fuel source.
- A few exceptions exist — certain cells in the eye and small regions of the brain still require glucose.
- Red blood cells also require glucose and cannot use ketones.
- Because the body can manufacture its own glucose, dietary carbohydrates are not essential.
Details
The Mechanics of Gluconeogenesis
Gluconeogenesis is a metabolic pathway — a series of biochemical steps — that converts non-carbohydrate substrates into glucose. The two primary sources used are:
- Protein (amino acids broken down from dietary protein or muscle tissue)
- Certain lipids, specifically triglycerides (a type of fat found in food and stored in body fat)
This means the body has an internal glucose manufacturing system that operates independently of carbohydrate intake.
Why the Body Needs This System
The main driver of gluconeogenesis is blood sugar regulation. When you go extended periods without eating carbohydrates — such as during intermittent fasting, prolonged fasting, or a ketogenic diet — blood glucose could drop dangerously low. Gluconeogenesis prevents this by supplying just enough glucose to meet the demands of tissues that specifically require it.
Which Cells Need Glucose vs. Ketones
Dr. Berg highlights an important distinction:
- Most cells in the body are flexible and can use ketones as a primary fuel source instead of glucose.
- Cells that still require glucose include:
- Certain cells in the eye
- Small specific areas of the brain
- Red blood cells (which have no mitochondria and cannot metabolize ketones)
For these cells, gluconeogenesis ensures a continuous glucose supply even during carbohydrate restriction.
Carbohydrates Are Not Essential
The overarching point Dr. Berg makes is that carbohydrates are not a dietary essential. Unlike protein (needed for amino acids) and fat (needed for essential fatty acids), there is no equivalent “essential carbohydrate.” If the body requires glucose, it can synthesize exactly what it needs through gluconeogenesis — no dietary carbs required.