Eating a low carbohydrate diet has been around for a very long time with many civilizations thriving on a diet of mostly protein and fat such as the Inuit, the Sioux and the Masai. Restricting carbohydrates will put your body into ketosis but this does not guarantee weight loss, you still need to restrict your calories to lose weight. There are two schools of thought right now on the ketogenic diet, one that follows the medical ketogenic ratios: it is Low Carb High Fat (LCHF) with scant amounts of protein and the other camp is based off of the science and research of Drs. Phinney and Volek, where the amount protein eaten is adequate to prevent muscle loss and the fat macro is used to control calories for the purpose of losing weight.
The medical ketogenic diet was originally designed in the 1920's to help epileptic children control their seizures, they were eating enough calories to not lose weight on the diet and it was strictly monitored by a doctor; it was not intended to be a lifelong diet but only to be used for a few years. Due to the the low amount of protein that was eaten muscle atrophy in the children was a known side effect that the parents had to agree to before the treatment commenced.
The original ketogenic diet was NOT designed to help people lose weight. If you look on the internet you will see that what people have done is take those same medical ratios but eat at a deficit, they call it Low Carb High Fat (LCHF) and they will lose weight because they are eating fewer calories than the body requires but because they are not eating enough protein their body will break down or catabolize the skeletal muscles to get what it needs to maintain and repair the major organs. Read: if you restrict your protein you will lose your lean body mass (lbm).
Drs. Phinney and Volek, after years of research, have discovered that a well-formulated ketogenic diet for optimal health and weight loss is one where we eat low carb, adequate protein and eat fat to purpose, which means while cutting calories for weight loss you will eat low fat. This is the science that I use when I calculate your personalized macros, this guarantees that you will retain your lean body mass while losing fat.