It works by increasing blood levels of substances called ketones, which are absorbed by brain cells in place of glucose – a type of carbohydrate and our body’s main energy source.

In some forms of epilepsy, this ‘fuel switch’ has the potential to improve seizure control. “In children, where the ketogenic diet has been widely researched, seizures are typically reduced by at least 50 per cent in at least half of the cases,” explains Dr Elizabeth Neal, a research dietician and member of the medical board of the epilepsy charity Matthew’s Friends. “A number of those who start the diet may become seizure free at some point.

“Initially used primarily in children, the ketogenic diet is now prescribed to people with epilepsy in all age groups, including babies, adolescents and adults. There is also more awareness of the benefits by healthcare professionals and parents, which has led to children being referred sooner, whereas in the past the ketogenic diet was seen only as a last resort,” says Neal.

Just like with any other medical treatment, people on the diet need the close supervision of a team of dietitians and doctors. Those who experience fewer seizures usually do so within a few weeks of starting the diet. Some of them report additional benefits, such as reduction in anticonvulsant medications,  improved energy levels, mood and overall quality of life.