How Does Keto Work?

Carbohydrates are usually the preferred source of energy production by our cells. When net carbohydrate intake is limited to less than 50g per day, insulin secretion is reduced and our glycogen stores become depleted, forcing the body to adapt to a different metabolic state.

This new metabolic state works by shifting the body’s metabolism from using glucose (sugar) as its primary source of energy to using ketones, which are derived from fat. This metabolic state is called ketosis. We will cover ketosis in more detail in the chapter “The metabolic process of ketosis”.

Let’s review some of the key concepts of the ketogenic diet, as a solid grasp of these principles will enable you to follow the diet effectively and maintain a state of ketosis.

Key Concepts

Macronutrient ratio

The keto diet is characterized by a high-fat, moderate-protein, and low-carbohydrate macronutrient ratio. Typically, it consists of approximately 60-80% fat, 20-30% protein, and 5-10% carbohydrates. I find maintaining ketosis can be very challenging consuming less than 70% fat intake.

Depleting glucose reserves

By significantly reducing carbohydrate intake, the keto diet deprives the body of glucose, which is its preferred energy source. As a result, the body then depletes its stored glucose (glycogen) reserves.

Decreased insulin levels

With lower glucose levels in the bloodstream, insulin secretion decreases. Insulin is a hormone that regulates blood sugar levels and promotes fat storage. Reduced insulin levels stimulate the breakdown of fatty acids from stored body fat.

Production of ketones

The liver converts fatty acids into ketone bodies, which serve as an alternative energy source for the brain and other organs when glucose is scarce. The primary ketone bodies produced are acetoacetate, beta-hydroxybutyrate, and acetone.


When the body consistently produces and uses ketones for energy, it enters a metabolic state called ketosis. In this state, the body becomes highly efficient at burning fat for fuel. Ketone bodies, specifically beta-hydroxybutyrate (BHB) and acetoacetate (AcAc), can cross the blood-brain barrier and be utilized by the brain for energy.