How Does The Ketogenic Diet Work?

Table of Contents (click to expand)

The ketogenic diet works by shifting the body from using glucose as an energy source to using fats instead. Burning fats produces chemicals called ketone bodies, which are another source of energy, although slightly different than traditional carbs.

There seems to be a new diet fad every day. Some swear by the benefits of the Paleo diet, while others are convinced that banishing all forms of grains will reform your life. However, in the last 3 years, I’ve increasingly come across claims that the keto diet will change your life. The claims made regarding the keto diet range from shedding weight fast and gaining muscle to “feeling” better and being more “awake”.

With all these bold claims flying around, an important question arises…what exactly does it do in your body?

Keto food avocado, bacon, nuts, eggs, etc(JoyStudio)S
The ketogenic diet allows foods that are high in fat and protein, but low in carbohydrates. The above picture shows some of the food allowed on the diet. (Photo Credit : JoyStudio/ Shutterstock)

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What Is The Ketogenic Diet?

ketogenic diet plan
Pie charts showing mactronutrient intake for different types of keto diets compared with the normal American diet. (Photo Credit : Colin/Wikimedia Commons)

The ketogenic diet (a low-carb, high-fat diet) recommends eating more fats and proteins than carbohydrates (sugars). This is calculated as the ratio of fats to carbs and proteins. This ratio is called the macronutrient ratio. The classic ketogenic diet developed in 1921 suggested a macronutrient ratio of 4:1, but since then, doctors have modified the diet to make it less restrictive.

At face value, the ketogenic diet sounds counter-intuitive. How can eating more fat make you less fat? The answer lies in the different ways that the body processes carbohydrates and fats.

Also Read: Why Is The Ketogenic Diet Not Meant For Everyone?

How Does The Ketogenic Diet Work?

The aim of the ketogenic diet is to get the body to get all its energy from fats rather than using sugars.

Under completely normal conditions, the body prefers carbohydrates or sugars, specifically glucose to get its energy. Organs like the brain and the eyes almost exclusively use glucose for energy needs.

Immediately after a meal, there is an abunbace of glucose in the blood and the blood sugar level is high. This high blood sugar signals the pancreas to secrete insulin. Insulin is necessary for most organs (except a few, like the brain) to start using the abundant glucose.

Once all the glucose is used up—both free glucose and that acquired from glycogen, the stored form of glucose—the body switches over to using fat.

Fats stored in adipose tissue are transported through the blood to the liver. In the liver, fats—or more accurately, fatty acids—are broken down into smaller molecules called acetyl-CoA. These acetyl-CoA molecules then enter the citric cycle, which produces the majority of energy in the body.

When human loss weight and diet food the mitochondria of liver cells will produced Ketone bodies for energy( kanyanat wongsa)s
A flow chart of how ketosis is achieved. Acetyl-CoA increases in the liver because of fat breakdown. This excess acetyl-CoA combines and forms ketone bodies. (Photo Credit : kanyanat wongsa/ Shutterstock)

The ketogenic diet aims to keep the body using fats. This is why carbohydrates are eaten in the least quantity.

But, because of the heavy dependence of fats to gain energy, there is a build-up of acetyl-CoA in the liver.

The excess acetyl-CoA combine with each other to form ketone bodies, such as acetone, acetoacetate, and beta-hydroxybutyrate. Ketone bodies are an alternative source of energy for the body when glucose is not available. They get transported from the liver to other tissues to be used; in fact, ketones are the only other chemical the brain uses for energy.

When ketones are produced, the body is said to be in a state of ketosis.

Ketone bodies(chromatos)S
The three different ketones produced when the body is in ketosis. (Photo Credit : chromatos/ Shutterstock)

Keeping the body in ketosis is what a ketogenic diet targets. To maintain ketosis, just enough sugar is allowed to force the body to continue burning its fat reserves. However, this doesn’t answer an important question—why doesn’t the body store all this fat?

Insulin is the simple answer. Insulin promotes sugars to be converted to fats, and leads to fats being stored in adipose tissues. Very little glucose is stored as glycogen in the body. What does the body do with excess glucose when it doesn’t need it? It turns it into fat. Do you remember that even glucose forms acetyl-coA? That same acetyl-CoA is used to make fat. The keto diet keeps insulin levels low, which tells the body that glucose is low, so it doesn’t store any fat. Et voila, you continue to burn fat.

Also Read: Why Are Fats The Preferred Energy Storage Molecule?


Although the ketogenic diet does sound like a miracle diet from the simple biochemistry above, there are some caveats that are critical to understand. Nutritional biochemistry is complex and the above picture only depicts what we know for sure.

There is a whole world of hormones controlling these processes and we don’t yet know how the ketogenic diet affects each of them. Hormones like insulin, leptin, ghrelin, GLP-1 and more all interact with each other to affect our metabolism. In the short term, the ketogenic diet does show more weight loss success than a low-fat diet, but how the diet will affect a person over the long term hasn’t been studied yet.

Furthermore, there is a fine line to maintaining ketosis. Ketosis is normal, but it does cause what is commonly known as the ‘keto flu’. That also might be due to the body adjusting to using ketones as fuel. However, if excess ketones build up, it can lead to ketoacidosis.

Ketoacidosis is when the blood becomes very acidic, which can hamper the proper functioning of vital organs. This is why it’s best to get the advice of a nutritionist before going on any diet. Only a trained professional will actually get you the best results. Ultimately, any diet will work as well as your lifestyle and genetics will allow!

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References (click to expand)
  1. (2021) Ketogenic Diet - StatPearls - NCBI Bookshelf. National Center for Biotechnology Information
  2. Stryer L., Berg J., Tymoczko J.,& Gatto G. (2019). Biochemistry. Macmillan Learning
  3. Wheless, J. W. (2008, November). History of the ketogenic diet. Epilepsia. Wiley.
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About the Author

Salama has a degree in life sciences and biochemistry from St. Xavier’s College, Mumbai, which she puts to good use as a science writer and video producer at She’s interested in the history of science; how science has shaped how we understand the world and society.