The ketogenic diet is one treatment option for children or adults with epilepsy whose seizures are not controlled with AEDs. The diet may help to reduce the number or severity of seizures and may have other positive effects.Foods included in the ketogenic diet Up to 70% of people with epilepsy could have seizures controlled with anti-epileptic drugs (AEDs). For some people who continue to have seizures, the ketogenic diet may help. However, the diet is much specialized. It should be carried out with the care, supervision and guidance of trained medical specialists.Epilepsy is a disabling and common neurological disease, which can be controlled successfully in most patients with one or more antiepileptic drugs. Approximately 30% of patients with epilepsy have refractory epilepsy, that is, have a failure of adequate trials of two tolerated, appropriately chosen and used antiepileptic drug schedules to achieve sustained relief of seizures. Some of these patients are not surgery candidates, so it is necessary to search for alternative treatments for epilepsy such as palliative surgery, neuromodulation, and a ketogenic diet (KD).The classic ketogenic diet (CKD) consists of a high-fat and low-protein and carbohydrate diet, with restricted calories and fluids. The diet mimics the fasting state, altering the metabolism to use fats as a primary fuel source; catabolism of fatty acids in the liver produces ketone bodies (KB), which induces urinary ketosis.Recent studies have found a significantly positive outcome with the use of the KD for treatment of refractory epilepsy in children and adults.Regardless of the efficacy of the KD, most patients discontinue the diet because of its unpalatable and restrictive features. Over years, new variants of the KD diet have emerged, including the Modified Atkins diet (MAD), a low-glycemic-index diet, which although it has a high fat content, allows more protein and does not restrict calories and fluids. Several studies have shown that the new variants of the KD have a similar efficacy to the CKD. As presently understood, the KD is involved in multiple mechanisms responsible for biochemical alterations, including cellular substrates and mediators responsible for neuronal hyper excitability. However, it is not yet known with certainty whether the success of the KD is due to a single or several mechanisms.Because epilepsy is a metabolic disease, interest in studies of alterations of metabolism by anticonvulsants such as the KD has increased, as has their importance for the treatment of drug-resistant epilepsy. This contribution reviews the use and effects of the KD and its variants for the treatment of adults and children with intractable epilepsy.Adapting the DietThe classic ketogenic diet pioneered by Dr. Wilder is considered the gold standard for people with medication-resistant epilepsy because it produces the most ketones. It also demands the highest fat intake and is often the most difficult to follow due to the strict ratios required in planning and preparing meals. In the case of a patient had to follow a three-to-one ratio of fat to carbs and proteins. So, for example, if a meal included 12.8 grams of protein (less than three ounces of meat) and 7.9 grams of carbohydrates (one cup of string beans), it would also have to include 62.1 grams of fat (roughly equal to four and a half tablespoons of butter, cream, and coconut oil). Achieving these exact proportions requires meal preparers to weigh and measure food for every meal.