Metabolism basically refers to all the chemical reactions within the body used to produce energy. This involves a complex set of processes that convert fuels into specialized compounds loaded with energy. In the body, the primary final agent to produce energy is called adenosine triphosphate (ATP). When ATP is broken down or used by cells huge amounts of energy is released. This energy is essential for cells to grow and divide, synthesize important compounds, for muscles to contract and numerous other important functions.
The body has three main types of molecules it uses for energy:
Carbohydrates: These are the sugar type compounds in the body. Carbohydrates come from foods such as bread, cereal, potatoes, fruits and sugar-containing foods or bevarages. When carbohydrates are digested in the gastrointestinal system they are broken down into smaller molecules such as glucose (a simple sugar). The main storage sites for carbohydrates in the body are the liver and muscles.
Lipids: This basically refers to fats (such as cholesterol) from the diet or stored in adipose tissue (in other words the body fat). Lipids are broken down into smaller components called fatty acids for energy. Therefore lipids are really just chains of fatty acids joined together.
Proteins: These make up nearly three quarters of all the solid materials in the body. Proteins are thus the basic structural components in the body. They are made up of smaller agents called amino acids – considered the building blocks of proteins. Protein is present in the diet in foods such as meat, eggs, nuts and dairy products.
In general, carbohydrates form the main energy source for the body. They are the most efficient at producing ATP or energy (meaning they produce lots more ATP per amount of the fuel broken down). The body preferentially breaks down carbohydrates first, and then fats and finally proteins only if the other two fuels are depleted. This is important as proteins are generally less efficient at generating energy. In addition, proteins perform several important functions so if they were broken down several systems could fail.
To illustrate an example, in the event of starvation, the body has fewer carbohydrates available so will start to breakdown the fat stores in the body. Once all the available carbohydrate and fat stores have been depleted, the body will start to break down proteins to provide energy.
If your body runs out of other sources of fuel, it will start to use muscle tissue for energy. This is not a normal condition, and your body will only start to use muscle tissue for energy under extreme conditions, such as if you are very sick, severely malnourished or not consuming enough calories over an extended period of time to support normal body functions.
The first line of defense in maintaining energy is to break down carbohydrates, or glycogen, into simple glucose molecules — this process is called glycogenolysis. Next, your body breaks down fats into glycerol and fatty acids in the process of lipolysis. The fatty acids can then be broken down directly to get energy, or can be used to make glucose through a multi-step process called gluconeogenesis. In gluconeogenesis, amino acids can also be used to make glucose.
Remember that the body burns carbohydrates first, followed by fats and proteins only when the other two are depleted. Therefore if the carbohydrates in the diet are limited, the body will start to burn fat stores.
- Eat a balanced diet – appropriate amounts of carbohydrates, fat and protein
- Do not eat excessively – for most people, a diet of 1,500 to 2,000 calories a day is sufficient to maintain a healthy weight
- Exercise regularly
- Sleep well
Ketosis
Ketosis refers to an increased concentration of ketone bodies within the blood. When carbohydrates are unavailable for energy the body switches to metabolism of fatty acids. The body takes these from adipose tissue (the body’s fat stores). The fatty acids generated can either be broken down for energy or may be converted to ketone bodies within the liver. Some ketones can be excreted in the breath and give it a sweet smell (acetone breath).
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Content collected from various articles
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