Carb depletion diets are diets that restrict either all dietary carbohydrates or certain types of carbohydrates. Most of these diets are aimed at weight loss. An exception is the ketogenic diet, which doctors occasionally prescribe to epileptics who do not respond well to standard anti-seizure medications. The ketogenic diet also proves promising as a treatment of cancer in patients in advanced stages of cancer.
Standard Low-Carb Diets
One of the most popular weight-loss carb depletion diets is the Atkins diet. It restricts carbohydrates to 20 g a day during the induction phase but allows a higher intake of carbohydrates in later phases. There are no restrictions on fat and protein intake. Fat and protein are slower to convert into useable energy than carbohydrates. So, by eating mostly fat and protein, the Atkins diet may give rise to a quicker and longer-lasting feeling of fullness compared to a regular diet. The restriction of carbohydrates can also make the body switch from using glucose as its main source of energy to using stored fat.
High-Glycemic Index Diets
High-glycemic index diets, such as the South Beach Diet, work on principles similar to the Atkins diet, but allow for consumption of carbohydrates that are slow to break down in the digestive system. The latter kinds of carbohydrates are also known as high-glycemic index carbohydrates. Foods high in high-glycemic index carbohydrates include whole-grain bread and pasta, brown rice, legumes and vegetables. High-glycemic index diets restrict foods high in low-glycemic index carbohydrates, such as sweets, breaded foods, white bread, white pasta and white rice.
The Ketogenic Diet
R.M. Wilders, M.D., invented the ketogenic diet in the 1920s as a way of treating children with epileptic seizures. The diet restricts carbohydrates to 10 to 15 g a day and protein to 1 g a day. As it is not intended as a weight-loss diet, it provides all the calories the body needs to sustain itself. The calories that do not come from carbohydrates and protein come from fat. Epilepsy centers, such as the Johns Hopkins Hospital Ketogenic Diet Center, still prescribe the diet to patients who do not get seizure relief from conventional medicines. Because of the extreme restrictions of protein and carbohydrates, the diet is normally followed under clinical supervision.
Effects of Carb Depletion Diets
Diets that restrict carbohydrates to an absolute minimum deplete the body’s stores of glucose, the building blocks of carbohydrates, within 12 to 14 hours. After the body’s stores of glucose have been depleted, the body starts to burn fat. Most of the body’s cells can use fat as a fuel. The brain can only use glucose or ketone bodies, a by-product of fat metabolism in the liver, as an energy source. To metabolize ketone bodies, the brain’s neurons need to build additional mitochondria, or cell engines. The increase in mitochondria stabilizes the brain’s neurons and makes the brain less prone to seizures. The Department of Obstetrics and Gynecology at Würzburg Hospital prescribes the ketogenic diet to cancer patients. The theory is that cancer cells thrive best on glucose. A diet that depletes the body’s stores of glucose can prevent or slow down the growth of tumors.
- "Epilepsy Currents"; The Ketogenic Diet: Stoking the Powerhouse of the Cell; Jong M Rho and Michael A Rogawski; March 2007
- Mayo Clinic: Atkins Diet: What's behind the claims?
- Mayo Clinic: South Beach Diet
- Würzburg hospital: Information on a ketogenic (low carbohydrate / high fat + protein) diet for cancer patients