While medications, surgery, and devices help many individuals attain seizure freedom, they are not always effective in treating epilepsy. In those cases, some people may want to explore alternative therapies, such as changing their diet. For many years, ketogenic diets have effectively treated both adults and children with drug-resistant (refractory) epilepsy.
On this page, we explore five versions of the ketogenic diets, how they work, and what you should know before starting.
The original ketogenic diet was developed by Dr. Russell Wilder of the Mayo Clinic in 1923, as a treatment for epilepsy. Ketogenic diets are high fat, low protein, and low carbohydrate diets designed to make the body use fat (rather than carbohydrates) as its primary energy source.
Normally, the body relies on glucose (blood sugar), a byproduct of converting carbohydrates, for energy. If it cannot find carbohydrates to convert, the body will believe it is fasting and begin to convert fat into energy; instead of producing glucose, the body will produce ketone bodies. Once there are elevated ketone levels in the bloodstream, the body enters a state of ketosis, which has been shown to improve neurological conditions and metabolic disorders, including epilepsy.1 As a result, ketogenic diets “trick” the body into believing that it is fasting to encourage it to burn fat, produce ketones, and enter ketosis.2
While there is scientific evidence that ketogenic diets are an effective non-pharmacologic treatment for some people with epilepsy, how they work is still not completely understood. Several theories have been suggested, however, and are explained in greater detail on this page (below).
There are five versions of the ketogenic diet used to treat epilepsy. The original, now known as the Classic Ketogenic Diet, was created in 1923, followed by more recent types known as the Modified Ketogenic Diet, the Medium Chain Triglyceride (MCT) Diet, the Modified Atkins Diet, and the Low-Glycemic Index Treatment (LGIT). The various types of ketogenic diets have been used for years and have been studied in people with epilepsy who have failed to achieve seizure control with anti-seizure medications.
The “classic” ketogenic diet (KD) is the most restrictive of the five versions. It follows the “ketogenic ratio” of 4:1 or 4 grams of fat for every 1 gram of protein and carbohydrate.3 People with epilepsy who follow this diet can expect to consume about 80-90% of their calories from fat, 6-8% from protein, and 2-4% from carbohydrates.
The traditional KD is prescribed by a doctor and begins with a 24-hour fast followed by an inpatient hospital stay for two to three days while the patient is monitored for ketosis. In some cases, however, the patient may be able to start the KD at home over four weeks by slowly increasing the ketogenic ratio each week from 1:1 to 4:1.
Food and drink should be weighed and measured on a scale due to the strictness of this diet. During the inpatient visit, a dietitian will 1) calculate the patient’s meal ratio; and 2) educate the patient or caregivers to help maintain the diet after leaving the hospital. People following the classic KD must also take vitamin and mineral supplements to make up for the nutrients this diet lacks.
The Modified Ketogenic Diet is slightly less restrictive than the classic KD and follows a ratio range of 3:1 (3 grams of fat for every 1 gram of protein and carbohydrate) down to a 1:1 ratio.4 Although this diet was not officially recognized in the 2018 update to the recommendations by the International Ketogenic Diet Study Group, it may be a more comfortable way to start or taper off the classic KD.
This version reduces the body’s reliance on fat as the primary source of calories and allows for more protein and carbohydrates. Still, people following the modified KD may need to take vitamin and mineral supplements to make up for the nutrients this version lacks.
The Medium-Chain Triglyceride (MCT) diet follows a ketogenic ratio of 1.9:1 or 1.9 grams of fat for every gram of protein and carbohydrate. Medium-chain triglycerides (MCT) are a type of fat that is generally made by processing coconut and palm oils – they are not found in traditional foods.4 Not only does the body digest MCTs more efficiently than the fat typically found in food (long-chain triglycerides (LCT)), but it also produces more ketones. Because of this, people following the MCT diet can incorporate more protein and carbohydrates into their diet compared to the classic KD.
People who follow this diet can expect to consume about 60% of their calories from MCT in addition to traditional fats, protein, and carbohydrates. This version of the KD is traditionally started in the hospital under the supervision of a neurologist and dietician and MCT is given as an oil or nutritional supplement with each meal and/or snack. This level of MCT, however, may cause stomach issues or discomfort and the dietician may recommend starting with a lower MCT percentage (40-50%) before adjusting up or down. People following this diet must also take vitamin and mineral supplements to make up for the nutrients this version lacks.
The Modified Atkins Diet (MAD) is a mix between the classic KD and the Atkins Diet.3, 5 It is less restrictive than the classic KD and generally follows a ratio of 1:1 (or one gram of fat for every gram of protein and carbohydrate). People on this diet may consume 65% of their calories from fat, 25% from protein, and 10% from carbohydrates. Unlike the classic KD, there are no restrictions on the amount of liquids, calories, or protein consumed, but there is still a limit for carbohydrates. This diet may be a good option for children, those that find it difficult sticking to the classic KD, or those with behavioral problems.
The Low Glycemic Index Treatment (LGIT) is a diet that emphasizes eating complex carbohydrates instead of simple sugars to consume foods with a low glycemic index (GI).3 The glycemic index is a number that ranges from 0-100 and describes how much a particular food increases the level of sugar in your blood after you eat it. Foods that have a high GI include most carbohydrates, which produce large increases in blood sugar and insulin levels. Foods with a low GI (e.g., unprocessed whole grains, meats, dairy, some fruits, and vegetables) produce smaller increases in blood sugar and insulin levels. High GI foods are those higher than 50; therefore, low-glycemic index foods are those less than 50.
Patients may consume a diet with 60% fat, 20-30% protein, and a 10% carbohydrate content. There are no restrictions on fat and protein intake, and LGIT allows for a larger carbohydrate intake; however, these carbohydrates must have a GI of less than 50. Young people may prefer LGIT because it is more tolerable compared to other versions of the KD, though it does produce a lower level of ketosis.
Although the way in which ketogenic diets work is still not completely understood, it has been used since the 1920s. Several theories have been suggested:
An increase in ketones
The ketones produced when the body uses fat as fuel instead of carbohydrates can prevent seizures by:
An increase in Polyunsaturated Fatty Acids
Polyunsaturated Fatty Acids (PUFAs) are a type of fat that comes from your diet and makeup approximately half of the fat content found in the brain. PUFAs help control the way neurons in the central nervous system work. An increase in these PUFAs can lead to:
Prevention of cell death
Having a seizure can cause damage or even the death of cells in the nervous system. Ketogenic diets increase the levels of a particular gene that protects these cells from dying.
Change in the microbes found in the intestine
Ketones change the bacteria found in the intestines, increasing the number of good bacteria. This change has a positive effect on certain chemicals in the blood and brain.
Starting and maintaining a ketogenic diet involves a joint team approach from neurologists, nutritionists, and primary care providers. Choosing the right diet is based on several factors, including, age, type of epilepsy, current medications, comorbidities, nutritional health, and treatment response.
While evidence has shown that the classic KD is slightly more effective at treating epilepsy than other versions, it is not as well-tolerated due to its restrictive nature and side effects. The classic KD may be easier to administer to children, but the modified KD, MCT, and MAD variations are more tolerable, flexible, and have fewer adverse effects. LGIT is also less restrictive and more favorable; however, there is not enough information regarding the safety and tolerability of the diet.
Patients should avoid ketogenic diets if they have any of the following conditions:
To determine the efficacy of ketogenic diets, patients should try the diet for at least three months from the time ketones are found in the body. Patients should also be seen regularly, ideally every three months, to monitor progress, discuss concerns or adverse effects, and adjust the diet (if needed).
Side effects can occur in all five versions of the ketogenic diet; however, it has been reported that stricter versions result in a higher rate of side effects.6
The Charlie Foundation for Ketogenic Therapies is a leading resource for the ketogenic diet in epilepsy. In addition to informative videos and graphics, their website has resources to help people with epilepsy find the right diet for them as well as tools to help them manage their diet. Visit their website for more.