Benign Dietary Ketosis

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(Redirected from Ketosis)

Benign Dietary Ketosis (BDA) or more simply Ketosis, is a stage in metabolism occurring when the liver has been depleted of stored glycogen and switches to a stored fat-burning mode.

During the stage of Ketosis (after glycogen has run out), fat (triglycerol) is cleaved to give 3 fatty acid chains and 1 glycerol molecule in a process called lipolysis. Most of the body is able to utilize fatty acids as an alternative source of energy in a process where fatty acid chains are cleaved to form acetyl-CoA, which can then be fed into the Krebs Cycle. During this process, a high concentration of glucagon is present in the serum and this inactivates glucose kinase switching the primary energy source of most cells from using glucose to fatty acids. At the same time, new glucose is synthesized in the liver from lactic acid, glucogenic amino acids, and glycerol, in a process called gluconeogenesis. This glucose is used exclusively by cells such as neurons and red blood cells.

Ketone bodies, from the breakdown of fatty acids to acetyl groups, are also produced during this state, and are burned throughout the body. During the initial stages of starvation the brain does not burn ketones, since they are an important substrate for lipid synthesis in the brain. But after several days of Ketosis, the brain transitions to burning ketones in order to more directly utilize the energy from the fat stores that are being depended upon, and to reserve the glucose only for its absolute needs, thus slowing the depletion of the body's protein store in the muscles.

The brain retains a residual need for glucose, because ketones can only provide energy when used during aerobic respiration in mitochondria. In the long thin neurons, much of the metabolically active cellular membrane must derive its energy from glucose via anaerobic respiration without the assistance of mitochondria.

Ketosis, should not be confused with ketoacidosis, which is severe ketosis causing the pH of the blood to drop below 7.2. Ketoacidosis is a medical condition usually caused by diabetes and accompanied by dehydration, hyperglycemia, ketonuria and increased levels of glucagon. The high glucagon, low insulin serum levels signals the body to produce more glucose via gluconeogenesis, glycolysis and ketogenesis. High levels of glucose causes the failure of tubular reabsorption in the kidneys, causing water to leak into the tubules in a process called osmotic diuresis, causing dehydration and further exacerbating the acidosis.

The breath of people in a ketagenic state commonly contains acetone, detectable as a sweet smell that may be mistaken for ethyl alcohol.

Deliberately induced ketosis through a low-carbohydrate diet has been used to treat medical conditions. The ketogenic diet is an approach to treating epilepsy, and the Atkins Nutritional Approach is marketed for treating obesity.

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