Ketogenic diet is not just a fat based diet which leads to generation of ketones. Its real features is that it does not include much of carbohydrates. Ketogenic diet is often used to fight cancers particularly brain cancer. The theory is that the brain only takes glucose. If you limit the amount of carbohydrates, you essentially limit the energy source for cancer cells in the brain. The problem is, you can not completely eliminate glucose because you have to use some as normal brain cells also need it as the source of energy. In addition, cancer cells can also use some amino acids like glutamine as their energy source and amino acids are not limited in e ketogenic diet. So ketogenic diet does not have a powerful anticancer efficacy even though it does slow down the progression and patients may live a few more years.
Ketogenic diet is similar to fat/protein diet. One famous fat/protein diet is the Budwig diet which consists of cottage cheese and flaxseed oil. This diet was promoted by Dr. Johanna Budwig and used to treat all sorts of cancer. It seems that this diet actually help many cancer patients. Dr. Budwig claimed that her diet is particularly effective at getting rid of pediatric leukemia. Childhood leukemia responds to this diet quickly while adult leukemia responds generally slowly.