The ketogenic diet was originally developed in the 1920s by Dr Russell Wilder at the Mayo Clinic to help control epilepsy in children. When effective anticonvulsant drugs became available in the 1940s, the popularity of the diet waned. It was not until the 1990s when scientific interest was renewed. There are now several variations.
The diet forces the body to burn dietary fat rather than carbohydrate, and was originally designed to mimic the effects of fasting for extended periods. This is achieved by providing a high level of fat, a moderate level of protein and a low level of carbohydrate. Carbohydrates are normally converted into glucose, which is then transported around the body and is particularly important in fuelling brain function. However, when carbohydrates are restricted, the liver converts fat into fatty acids and ketone bodies. These ketone bodies pass into the brain, and are used instead of glucose as a source of energy. The resultant elevated level of ketone bodies in the blood streams is called ketosis, and this leads to a reduction in the frequency of seizures.
Clinicial trials of the ketogenic diet in the management of paediatric epilepsy show that it is a beneficial way to reduce seizures (in children), but studies outside of this area are limited.
Results of a Ketogenic Food Trial for Dogs with Idiopathic Epilepsy (Edward E. Patterson. American College of Veterinary Internal Medicine. 2005) did not yield promising results, and there was no difference in seizure frequency between the dogs fed on a high fat, low carb diet and those fed on a diet with moderate levels of protein, fat and carbs.
It is believed that this was because dogs (as carnivores) are actually very well adapted for fasting for reasonably long periods of time, and thus the essential biochemical changes caused by changing to a high fat and low carbohydrate diet in humans cannot be manipulated in dogs. The way we metabolise our food is very different to the way dogs metabolise theirs. Furthermore, the ketogenic diet is most effective for children with particular types of epilepsy (especially refractory epilepsy), and so generalisations cannot be made in this group, let alone across other species.
High fat diets may result in medical conditions such as pancreatitis.
Some parties believe that ketogenic diets have the ability to combat cancer because cancer cells (particularly those in the more advanced stages of malignancy), feed preferentially on glucose as a source of energy. Malignant cancer cells have limited or no ability to burn fat for energy and they can only use protein for energy, once it has been processed by the liver, to form glucose. Evidence is largely anecdotal at present.
Please refer to the article Canine Diet & Epilepsy.