The ketogenic diet has quickly established itself as an effective weight loss tool in recent years. The ubiquity of the ketogenic diet means that there should be an understanding of how the diet works. This diet calls for restriction of carbohydrates—if properly done this leads to a breakdown, and therefore the loss of, body fat. But how does that work? Let’s understand this complex biochemical process.

What is a carbohydrate?

Carbohydrates are fiber and different molecules of sugar. An important carbohydrate is glucose. Glucose (a type of sugar) is the body’s primary energy source. Everything our bodies do requires energy. Many food sources of carbohydrates are broken down into individual glucose units during digestion. Glucose is either used for energy right away or stored for later use.

What about starches?

Starches are simply long chains of individual glucose molecules.

Potatoes for example are known to be very starchy. This means potatoes are made up of a lot of sugar.

How does glucose provide energy?

Glucose undergoes a process called glycolysis which takes place in cells’ mitochondria. This process breaks down glucose and produces adenosine triphosphate (ATP) molecules. ATP contains a lot of energy. Every basic and complex physiologic process requires ATP. Running, walking, digestion, chewing, fighting off a cold…these all require ATP.

But what if we reduce our carbohydrate intake?

Ketogenic diets are low carbohydrate and usually high protein and moderate fat diets. During periods of carbohydrate reduction our bodies begin a metabolic process that ensures ATP’s production.

When the body is need of energy and carbohydrates are not available, the hormone glucagon is released and the breakdown of fatty acids begins. Glucagon stimulates an enzyme specific to fat, lipase, to break down triglycerides into 3 fatty acid molecules. Those fatty acids are converted to ketone bodies. Ketone bodies then move throughout the bloodstream where they are they are absorbed by cells. Once ketone bodies are absorbed they enter the mitochondria and are converted to another molecule: acetyl-CoA. Acetyl-CoA is then converted to ATP. And that means…energy!

This complex biochemical process is the reason that low carbohydrate diets work for weight loss, and this demonstrates the body’s remarkable ability to adapt in times of need.

In summary:

  • Low carbohydrate diet (< 50 grams carbohydrates/day)
  • Body uses free and stored glucose for energy needs
  • As energy needs continue but carbohydrates are not available, glucagon is released
  • Glucagon sends signals to lipase
  • Lipase breaks down triglycerides
  • Fatty acids become available from triglycerides
  • Fatty acids are converted to ketone bodies
  • Ketone bodies travel through the blood and are absorbed by cells
  • Within cells, ketone bodies are converted to acetyl-CoA which is used to produce ATP

– Sondra Tunon