The ketogenic diet originated from observations in the 1910s that patients with epilepsy who were placed in a fasting state experienced a 50 percent or more reduction in the frequency of their seizures. The classic ketogenic diet, first documented in the 1920s, is a high-fat, low-carbohydrate diet created to mimic the metabolic effects of starvation. Its mechanisms of action, however, are more complicated than starvation. Indeed, evidence suggests that independent effects of ketone-body creation lead to neuro protection. In the 1940s, when new anti-seizure drugs became available, the ketogenic diet was displaced as a last-resort treatment. Awakened interest occurred in the 1990s, when movie producer Jim Abrahams started the Charlie Foundation for Ketogenic Therapies after his young son experienced complete remission of seizures after implementing ketogenic diet therapy. Subsequent clinical studies in epilepsy showed improvement in cognition, mood, alertness and energy level as additional benefits, which lead to its use for other brain disorders. As use of ketogenic-diet therapy expands into other applications, the evolution of ketogenic diets has allowed for increased dietary options and better compliance. Today there are five variations of ketogenic diets used in epilepsy in order to accommodate different ages, nutrition requirements and lifestyles. A well-formulated ketogenic diet can be therapeutic as well as nutritionally adequate.