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The ketogenic diet restricts carbohydrate intake, and to a lesser extent protein intake, to the point where the body converts that into ketones. These ketones are an alternative fuel source for most cells in the body, supplementing or replacing glucose as a critical fuel source. The [[Ketogenic Diet as a Treatment| ketogenic diet has the potential to help with a number of health conditions]], but also has [[Health Risks of the Ketogenic Diet| some significant potential health risks]].
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=What is the Ketogenic Diet?=
The word "ketogenic" literally means that it creates [[Ketones]]. Our bodies produce ketones from fat when carbohydrates become scarce. To trigger ketosis (the production of ketones) we normally have to restrict carbohydrate intake to a very low level. The exact amount of carbohydrate varies by individual, but often it has to be restricted to less than 20g/day. (Normally the amount [[Fiber]] is ignored in the diet, and [[Net Carbohydrates]] are used.) Because the body will convert protein to glucose, it is also necessary to tightly control the intake of protein. Too much protein will prevent ketosis, but to a little will cause malnutrition. Some authors recommend the RDA for protein, while others suggest 0.6 to 1.0 grams per pound of lean body mass. When carbohydrate availability is restricted, the body does not immediately swap over to using fat and ketones, but rather there is a period of adaptation often referred to as [[Ketoadaptation]]. This made last a few weeks, and some people report feeling sluggish during this time. The ketogenic diet entails some potentially serious health risks, so medical supervision is required, along with regular tests and diet supplements. The ketogenic diet is one of the more stringent [[Low Carbohydrate Diets]], and should not be taken lightly.
=Are Carbohydrates Necessary?=
There are various answers to this, both 'yes' and 'no'. While many cells can burn Ketones instead of Glucose, cells with few or no mitochondria must have glucose. However, protein can be converted to glucose, so while carbohydrate is necessary, it does not have to be consumed in the diet. If no protein is consumed, then the body will cannibalize muscle tissue to provide the required glucose. The only type of carbohydrate intake that could be considered critical for health would be [[Fiber]], which is converted by the digestive bacteria into Short Chain Fatty Acids which are the primary fuel source for some cells such as the lining of the colon.
=Advantages of the Ketogenic Diet=
* [[Ketogenic Diet as a Treatment]]. The greatest advantage of the ketogenic diet is probably its use for the treatment or management of disease.
* '''Muscle Building'''. The ketogenic diet tends to have a protein sparing effect. There are anecdotal reports (myself included) that it is much easier to build muscle on the ketogenic diet.
** Anecdotal suggestion that over-ketosis might cause growth inhibition in children.
** The [[Ketogenic Mechanism of Action]] is probably the ketones levels, so increased protein intake (or [[Net Carbohydrates| Net Carbohydrate]] intake) can impair muscle growth.
* '''Altitude'''. There is evidence that the ketogenic diet provides protection against hypoxia, and in this may convey a survival advantage at extreme altitude. In addition, it is possible that the ketogenic diet may improve the ability to function at high altitude. My personal experience is that during my [[Altitude Training]], I am able to remain unimpaired while breathing much lower percentages of oxygen.
** See "Survival of fasted rats exposed to altitude".
=Disadvantages of the Ketogenic Diet=
* '''Health Risks'''. There are some serious [[Health Risks of the Ketogenic Diet]]. These can largely be mitigated with care, but anyone considering the Ketogenic Diet should be aware of both the risks and the mitigations.
* '''Adaptation time'''. It can take some weeks to adapt to the ketogenic diet, a process known as [[Ketoadaptation]]. During this time many people report feeling sluggish and the benefits may not be readily apparent. It is unclear how longer you can be out of ketosis without losing your [[Ketoadaptation]], something that is important if you accidentally eat the wrong foods.
* '''Many unknowns'''. While there is a significant body of research on the ketogenic diet and low carbohydrate diets, there are still a large number of unknowns. Our lack of knowledge makes it harder to provide good recommendations, but hopefully this will improve as time progresses.
=Required Reading=
If you are seriously considering the ketogenic diet, you should read Dr. Kossoff's book as a bare minimum. The other books are worth reading, but I'm not as critical as Kossoff's volume.
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=References=
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