Ketogenic diet - What is it?

The Ketogenic Diet - What is it really?

The ketogenic (or "keto") diet is often spoken about these days. But  many appear to have the wrong idea. Here is just a very brief introduction to what defines a ketogenic diet.

Many people talk about the ketogenic diet. Unfortunately, a large proportion of these people appear to have little understanding of the underlying principles.


In brief, a ketogenic diet is one in which the body does not receive enough carbohydrate (sugar) to satisfy its energy requirements and therefore has to metabolise fats, leading to the production of ketone bodies. Simple as that, no more no less.

The amount of fat or protein in the diet has absolutely nothing to do with whether a diet is ketogenic or not. Those so-called professionals in nutrition who state categorically that a ketogenic diet is, by definition, a high-fat or high-protein diet are just demonstrating their ignorance. Beware!

Even so, that does not mean that it cannot be high in fat or in protein, just that those aspects of the diet do not determine the state of ketosis.

The body stores energy in two forms: glycogen and fat. Glycogen is formed of molecules of glucose (a sugar) joined together in branching chains. Glycogen is found mainly in the liver and muscles. When glucose is required for energy, glycogen can be broken down to provide the necessary supply. There are only a few hundred grams of glycogen in the body, but, particularly in overweight persons, it is used in preference to fat for energy. As the stores start to decrease, we eat to replenish them. Any extra energy we eat is stored as fat and, to simplify the process a little, will not be used while there is sufficient glucose/glycogen to satisfy the body’s needs.

Sometimes we may have to go without food for a period. During such a period, we are not getting the supply of glucose we need to satisfy our energy needs. What is going to happen? Obviously, we are going to start to burn fat. Most tissues can use energy derived from fat, though in all tissues other than muscle, the fat must first be processed by the liver to make its energy accessible (muscle can use fat directly for energy). In the liver, fat is broken down to acetyl-CoA which, if present in sufficient quantity in the liver cells, combines spontaneously to form acetoacetate, the first of the ketone bodies. The other two ketone bodies (formed from the breakdown of acetoacetate) are beta-hydroxybutyrate* and acetone. Some of the acetone escapes in our breath, making it smell sweet. So, when we don’t eat sufficient carbohydrate (sugars), the liver uses fat to make ketone bodies for energy; hence a diet low enough in carbohydrate to provoke this use of fat is called a ketogenic diet. And that’s why it doesn’t matter if the diet is high or low in fat or in protein, it is the carbohydrate (sugars) that counts.

When a person diets and goes into ketosis, it means he or she is breaking down fats. Where do these fats come from? Obviously, they can be derived from our own fat stores. That’s very useful if you want to lose weight. But what if we continue to eat foods that contain fat but no carbohydrate? Then we are going to remain in ketosis (because we don’t have enough carbohydrate), but the fat we are going to burn will come, at least in part, from the diet; that means we are going to be burning less of our own fat. This happens in diets such as the Atkins diet, in which subjects are invited to eat relatively large amounts of fat. In the PronoKal PnK Method, on the other hand, most of the fat has been eliminated, leaving only a few grams in each meal (in total, about 25 grams over the course of a whole day). So, the large energy deficit is going to draw on the body’s own stores, and the person will lose weight rapidly.

*Beta-hydroxybutyrate is not a true ketone body but for the sake of argument we can treat is as such.

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