The original version of the ketogenic diet, first introduced in the 1920’s, is often referred to as the “Classical” or “Traditional” ketogenic diet. Since then, there have been several variations of the classical ketogenic diet developed to provide different options for the dietary management of epilepsy. It is the role of the ketogenic diet team to select the ketogenic diet that is most appropriate for each patient and their family.

Classical Ketogenic Diet

The Classical ketogenic diet is the most popular type of ketogenic diet. This diet provides fat, protein and carbohydrate in a calculated quantity, known as the ketogenic ratio. The Classical ketogenic diet typically provides a 4:1 ketogenic ratio, which means for every 4g (grams) of fat, there is 1g (gram) of carbohydrate and protein combined. In some patients, such as infants and young children, a lower ketogenic ratio may be required, in which case a 3:1 ratio is commonly used.

The Classical ketogenic diet requires strict weighing of all food portions to ensure each meal results in the prescribed ketogenic ratio. Usually an initial hospital stay is required to commence this type of ketogenic diet.

Medium Chain Triglyceride Ketogenic Diet

In the 1970’s, it was discovered that medium chain triglycerides (MCT) produce more ketone bodies than the traditional long chain triglycerides (LCT) used in the Classical ketogenic diet. Therefore the MCT ketogenic diet was developed using MCT as the main fat source. Since MCT are said to be “more ketogenic” than other dietary fats, less fat is required and more carbohydrate and protein is allowed in this diet. This helps with compliance, and helps to make the diet taste better. However abdominal symptoms such as pain and diarrhoea can occur with the consumption of large amounts of MCT.

Modified Atkins Diet

During the 1990’s, Dr R.C. Atkins noted several similarities between the Classical ketogenic diet and his Atkins diet, for example, both diets are high in fat, low in carbohydrate and result in ketosis. However it is important to note weight loss is the primary goal of the Atkins diet whereas the main goal of the ketogenic diet is seizure control. Therefore in 2006, the Atkins diet was first referred to as the modified Atkins diet in order to distinguish between the two diets.

Overall, the modified Atkins diet is designed to produce ketosis in a more relaxed and less restrictive dietary therapy compared to the Classical ketogenic diet. Sometimes referred to as the modified ketogenic diet, the modified Atkins diet is based on a ketogenic ratio of approximately 1:1, although not all meals follow this ratio, and there is usually a maximum amount of carbohydrate that can be consumed, which is prescribed by the healthcare professional.

This type of ketogenic diet is growing in popularity due to the convenience and flexibility of the diet such that it does not require strict weighing of food portions and does not require an initial hospital stay to commence the diet.

Low Glycaemic Index Treatment

The Low Glycaemic Index Treatment (LGIT) was first developed in 2002, to offer individuals a more relaxed ketogenic dietary therapy. The LGIT focuses on the type and amount of carbohydrate consumed, specifically carbohydrates with a low glycaemic index (GI).

The GI of a food is a measure of the effect of carbohydrates on blood sugar (glucose) levels. When carbohydrate is eaten, it is digested into glucose, which is released into the bloodstream to provide energy for the body. Carbohydrate that is digested quickly has a high GI, whereas carbohydrate that is digested slowly has a low GI. Foods are ranked on a scale of zero to 100 based on their GI value. The LGIT includes foods that have a GI lower than 50.

The LGIT generally allows for a higher amount of carbohydrates in the diet, and food portions are typically measured using household measures rather than scales.

Summary of the types of ketogenic diet

This table below compares the main characteristics of each of the different types of ketogenic diet discussed in this section.

Type of Ketogenic Diet Diet Design Food Measurement Diet Initiation
Classical Ketogenic Diet   Based on a prescribed ketogenic ratio (e.g. 4:1, 3:1) Gram scale Inpatient
Medium Chain    Triglyceride Ketogenic                   Diet                      Based on MCT as the main source of fat Gram scale Inpatient
Modified Atkins Diet  Based on a carbohydrate restriction Household measures Usually outpatient
Low Glycaemic Index                 Treatment              Based on the glycaemic index of carbohydrates Household measures Usually outpatient



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