Metabolism Types and Components
The subject of nutrition is pretty wide and interesting. The food we eat and the various body functions are
interrelated in a series of processes. Nutrition deals with this interrelation.
The key components in the science of nutrition are: normal body requirement for the different food substances,
how the body uses the food (function), amount of food required and threshold for healthy body.
Food therefore supplies the essential energy the body needs, plus the chemical substances that can not be
synthesized in the body.
A complete, well balanced diet should supply all the required elements needed to maintain the body’s health. The
basic elements are obtained through carbohydrates, protein and lipids. There is a host of other inorganic elements
obtained from food or external sources. These include oxygen, hydrogen, sulphur, phosphorus and at least ten
other substances, in addition to water and vitamins.
Energy synthesis (metabolism)
The biochemical process through which the body obtains energy from food is called the metabolic process
(metabolism). In order for body cells to remain alive and function normally, they need to be ‘fuelled’ through a
series of processes.
Generally, metabolism can be broken down into two categories: catabolism and anabolism. Catabolism, which is our
main concern, is the breaking down of food molecules to extract energy, while anabolism is concerned with the
body’s synthesis of elements it needs for the proper functioning of cells.
Components of metabolism
The metabolic rate can be split into three components:
a) basal metabolic rate: represents the amount of calories burned at rest and equates to 80 percent of total
b) the energy expended when body is active, which is basically the energy used during physical activity. It
makes up 20 percent or less, of total energy used by a normal active person.
c) the energy used in ingesting, digesting and metabolising food (thermic effect of food), and makes up
between 5 and 10 percent of total energy used.
What affects metabolism?
The metabolic processes can be influenced by a variety of factors that may or may not work in combination,
including age, hormonal and genetic disorders.
Genetic or hereditary factors sometimes influence the rate of metabolism, for example a defective gene may cause
your body not to use up or metabolise carbohydrates in the normal way it should. Such disorders can be managed with
strict medical supervision, paying special attention to diet. Common metabolic disorders due to genes include
galactosaemia and fructose intolerance.
Since it is hormones which regulate metabolism, hormonal disorders directly affect it, particularly hormones
linked to the thyroid. If the thyroid is over active, it means more hormones are released, leading to increased metabolic rate.
Effects include raised appetite and weight loss. On the other hand, a less active thyroid lowers the rate of
metabolism, the effects of which may include an unexplained weight gain, constipation and lethargy.
Other factors affecting metabolism are gender, dietary deficiencies, body size, lean muscle mass, growth factors
in children and physical activity among others.
Metabolism is a more complex process than can be summarized here. The role it plays in determining the body’s
basic energy needs is the most vital.