Catabolysis is a

biological process Biological processes are those processes that are vital for an organism to live, and that shape its capacities for interacting with its environment. Biological processes are made of many chemical reactions or other events that are involved in the ...

in which the body breaks down

fat In nutrition science, nutrition, biology, and chemistry, fat usually means any ester of fatty acids, or a mixture of such chemical compound, compounds, most commonly those that occur in living beings or in food. The term often refers spec ...

and

muscle Skeletal muscles (commonly referred to as muscles) are organs of the vertebrate muscular system and typically are attached by tendons to bones of a skeleton. The muscle cells of skeletal muscles are much longer than in the other types of muscl ...

tissue in order to stay alive. Catabolysis occurs only when there is no longer any source of

protein Proteins are large biomolecules and macromolecules that comprise one or more long chains of amino acid residues. Proteins perform a vast array of functions within organisms, including catalysing metabolic reactions, DNA replication, respo ...

carbohydrate In organic chemistry, a carbohydrate () is a biomolecule consisting of carbon (C), hydrogen (H) and oxygen (O) atoms, usually with a hydrogen–oxygen atom ratio of 2:1 (as in water) and thus with the empirical formula (where ''m'' may or ma ...

, or

vitamin A vitamin is an organic molecule (or a set of molecules closely related chemically, i.e. vitamers) that is an Nutrient#Essential nutrients, essential micronutrient that an organism needs in small quantities for the proper functioning of its ...

nourishment feeding all body systems; it is the most severe type of

malnutrition Malnutrition occurs when an organism gets too few or too many nutrients, resulting in health problems. Specifically, it is "a deficiency, excess, or imbalance of energy, protein and other nutrients" which adversely affects the body's tissues a ...

Mechanism

Due to the normal metabolic rate of

human Humans (''Homo sapiens'') are the most abundant and widespread species of primate, characterized by bipedalism and exceptional cognitive skills due to a large and complex brain. This has enabled the development of advanced tools, culture, ...

s catabolysis becomes life-threatening only after 1–2 months from the cessation of nutrition going into the body. After this time, the damage to muscles and organs can be permanent and can also eventually cause

death Death is the irreversible cessation of all biological functions that sustain an organism. For organisms with a brain, death can also be defined as the irreversible cessation of functioning of the whole brain, including brainstem, and brain ...

, if left untreated. Catabolysis is the last metabolic resort for the body to keep itself — particularly the

nervous system In biology, the nervous system is the highly complex part of an animal that coordinates its actions and sensory information by transmitting signals to and from different parts of its body. The nervous system detects environmental changes th ...

—functional. Protein stores, especially in muscle tissue, provide the amino acids needed for the process. Amino acids are released into the blood and converted in the liver to alpha keto acids. Alpha keto acids can then be converted to glucose to maintain proper

blood sugar levels Glycaemia, also known as blood sugar level, blood sugar concentration, or blood glucose level is the measure of glucose concentrated in the blood of humans or other animals. Approximately 4 grams of glucose, a simple sugar, is present in the blo ...

. The situation can become dire when one begins to lose

mass; this is a sign that the fat has been expended and the body is now metabolizing the muscle tissue. This results in

muscle atrophy Muscle atrophy is the loss of skeletal muscle mass. It can be caused by immobility, aging, malnutrition, medications, or a wide range of injuries or diseases that impact the musculoskeletal or nervous system. Muscle atrophy leads to muscle weakness ...

, a loss of strength and, ultimately, a depletion of muscular tissue completely. Muscle weakness is not necessarily a symptom of catabolysis: the muscles will normally feel fatigued when they are not receiving enough energy or

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as wel ...

. Ultimately, catabolysis can progress to the point of no return when the body's machinery for

protein synthesis Protein biosynthesis (or protein synthesis) is a core biological process, occurring inside Cell (biology), cells, homeostasis, balancing the loss of cellular proteins (via Proteolysis, degradation or Protein targeting, export) through the product ...

, itself made of protein, has been degraded to the point that it cannot handle any protein. At this point, attempts to correct the disorder by giving food or protein are futile. The body has a natural store of

(also called '' adipose tissue'') that stores reserve energy. One can still stay alive while the body breaks down the fatty tissue (hence people

wasting In medicine, wasting, also known as wasting syndrome, refers to the process by which a debilitating disease causes muscle and fat tissue to "waste" away. Wasting is sometimes referred to as "acute malnutrition" because it is believed that episo ...

away from starvation). The person may, during catabolysis, have large amounts of

lipid Lipids are a broad group of naturally-occurring molecules which includes fats, waxes, sterols, fat-soluble vitamins (such as vitamins A, D, E and K), monoglycerides, diglycerides, phospholipids, and others. The functions of lipids include ...

s, and

amino acid Amino acids are organic compounds that contain both amino and carboxylic acid functional groups. Although hundreds of amino acids exist in nature, by far the most important are the alpha-amino acids, which comprise proteins. Only 22 alpha am ...

s in the bloodstream, due to the muscle fibers and adipose tissues being broken down and sent to the nervous system and

brain A brain is an organ that serves as the center of the nervous system in all vertebrate and most invertebrate animals. It is located in the head, usually close to the sensory organs for senses such as vision. It is the most complex organ in a v ...

. One may also exhibit a

fever Fever, also referred to as pyrexia, is defined as having a body temperature, temperature above the human body temperature, normal range due to an increase in the body's temperature Human body temperature#Fever, set point. There is not a single ...

, since the body is working hard to transfer the nutrients in the muscles and fat to the blood.

Treatment

While catabolysis can be deadly over time, if the person is given medical treatment early enough, the effects of catabolysis can be reversed. However, the person may require

intravenous Intravenous therapy (abbreviated as IV therapy) is a medical technique that administers fluids, medications and nutrients directly into a person's vein. The intravenous route of administration is commonly used for rehydration or to provide nutrie ...

nutrition Nutrition is the biochemical and physiological process by which an organism uses food to support its life. It provides organisms with nutrients, which can be metabolized to create energy and chemical structures. Failure to obtain sufficient n ...

, a

blood transfusion Blood transfusion is the process of transferring blood products into a person's circulation intravenously. Transfusions are used for various medical conditions to replace lost components of the blood. Early transfusions used whole blood, but mo ...

, and/or oxygen replenishment. After that, it may be a few weeks to a few months before the person's muscle mass and fat deposits can build themselves up again; there is a possibility that they may never build back up, depending on the severity of the condition.

References

External links

* {{Nutritional pathology Malnutrition

Mechanism

Treatment

See also

References

External links