A ketosis diet is a diet that makes the body switch from using glucose, or blood sugar, as its main source of energy to using fat. The Atkins diet is one of the most popular ketosis diets. It restricts carbohydrates, the main source of glucose, to a bare minimum but allows unlimited amounts of fat and protein. Some ketosis diets modify protein intake to allow for ketosis without any weight loss. One of the best known among these is the ketogenic diet.
Regular Ketosis Diets
Regular ketosis diets, such as the Atkins diet, are aimed at weight loss. The Atkins diet restricts carbohydrates to 20 g during the induction phase but allows up to 100 g during later phases. There are no restrictions on the daily intake of protein and fat. The state referred to as ketosis sets in when the body has used up its stock of free blood glucose and glycogen, the stored form of glucose, and switches to using fat as its primary source of energy.
Modified Protein Ketosis Diet
Like regular ketosis diets, modified protein ketosis diets aim at getting the body into a state of ketosis, but weight loss is not the aim of these diets. One of the best known modified protein ketosis diet is Dr. R. M. Wilders' ketogenic diet. The aim of this diet is to control seizures in patients who do not respond in regular ways to conventional antiseizure medications. The diet was highly popular when first proposed in the 1920s, because very few antiseizure medications were available at the time. However, epilepsy centers, such as the center at Johns Hopkins Hospital, still regularly prescribe the diet.
The Ketogenic Diet
The ketogenic diet restricts carbohydrates to 10 to 15 g a day and protein to 1 g a day per kg of body weight. The remaining calories come from fat. Because the diet is not intended as a weight-loss diet, it supplies all the calories the body needs to sustain itself. The major restrictions on carbohydrate and protein make it difficult for patients to observe the diet outside of a clinical setting. The modified Atkins diet is a less strict alternative to the ketogenic diet that may have some of the same effects as the ketogenic diet. This latter ketosis diet can be followed without professional supervision.
Effects on the Brain
When the body switches from using glucose as its primary source of energy to using fat, the brain is required to use a different source of energy as well. Unlike most of the body's cells, the brain cannot use fat as a fuel. When glucose is limited, the brain switches to metabolizing ketone bodies, a byproduct of liver fat metabolism. Because ketone bodies are a more efficient fuel than glucose, metabolizing them requires more cell engines, or mitochondria. When the number of these cell components increases, each individual nerve cell becomes more resistant to the kind of overexcitement that can cause seizures.
References
- Natural Physiques: History of the Ketogenic Diet
- "Epilepsy Currents"; The Ketogenic Diet: Stoking the Powerhouse of the Cell; Jong M Rho and Michael A Rogawski; March 2007
- Johns Hopkins Hospital: Ketogenic Diet Center
- Mayo Clinic: Atkins Diet: What's behind the claims?
- Epilepsy.com: The Modified Atkins Diet
- Michael R. Eades, M.D.: Metabolism and Ketosis
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