What is Ketosis?
Once glycogen stores are no longer available to cells, fat molecules are cleaved through lipolysis to provide three fatty acid chains and one glycerol molecule. Fatty acids can be used through metabolic processes in the body as an alternative source of energy to glucose (which is used through a metabolic pathway known as gluconeogenesis). The process by which fatty acids are used for energy is called beta-oxidation. Beta-oxidation produces a number of products, including acetyl-CoA, which is then used in the citric acid cycle to provide energy. During times in which glycogen stores in the body are depleted, acetyl-CoA is used by the liver to produce ketone bodies (which, in turn, leads to a state of ketosis being reached).
During times of ketosis and when the body begins to use fatty acids instead of glucose, the fatty acids of the body must be broken down into ketone bodies which can then cross the blood-brain barrier and be used along with already present acetyl-CoA in the brain for the citric acid cycle. One way though which a person can tell if they are in a state of ketosis is when acetone, a metabolite of acetoacetate, is lost in the breath and urine. This loss of acetone causes a very distinct odor which can be used as a quick method of determining if a person is in ketosis or not.
It is important to note that in some cases, the acidity of ketone bodies within the blood can cause a dangerous state known as ketoacidosis (often in diabetics). Because of the inherent acidity of ketone bodies, when they are found within the blood they have an affect on the homeostasis of blood pH that is normally maintained through bicarbonate buffering, variable amounts of carbon dioxide molecules permitted in the blood from the lung alveoli, absorption of hydrogen ions from various tissues, and a compensation from the renal system.
A number of dietary programs rely on the principles of ketosis in order to help people lose fat and stay more healthy and fit. Ketosis is a strategic method through which people can help themselves maintain a healthy weight and lifestyle. Many contemporary diets are high in carbohydrates which promotes the production of insulin and the storage of fat. In addition, these carbohydrates serve as the driving force behind the levels of blood glucose and glycogen within the liver.
Lowering the number of carbohydrates will also lower the amount of fat storage hormones that are being produced and, in turn, lower the amount of fat that is being stored. When the body gets a low enough blood glucose and its glycogen stores are depleted, it will switch to using ketogenesis as its primary fuel source. This will switch metabolism from a fat storage system to a fat utilization system and promote hormones that will break down fat in the body for use in metabolic processes.
It is important to note that though ketogenesis may seem as though it is an entirely different process than gluconeogenesis and that the two may be a “one or the other” type of system, this is not the case. The truth of the matter is that the two play a role in the larger system of metabolism and are both utilized on a regular basis. Being in ketosis or a ketogenic state simply means that the body is using ketone bodies as its primary source of fuel, rather than glucose or glycogen.
Written by : Alexander Maness, United States (M.S. in Biotechnology )
Edited by: Rajesh Bihani ( Find me on Google+ )