Metabolism is the sum of physical and chemical processes occurring within a living organism that are essential for sustaining life. During metabolism, some substances are broken down to yield energy while other substances are synthesized. Food that is consumed and digested in the small intestines is then metabolized such that nutrients are converted to functional and beneficial chemicals. Without metabolism the body would be unable to absorb and convert vital nutrients, store energy, or cleanse toxins.

Nutrition and exercise affect the process of metabolism--exercise stimulates metabolism while insufficient caloric intake decreases one's metabolic rate. To reduce fat storage and lose weight, one must regularly exercise rather than diet.

Glandular malfunction, such as thyroid or pancreatic problems, may also increase or decrease one's metabolic rate. Like pancreatic dysfunction, diabetes adversely affects metabolism by altering insulin production. Type 1 diabetes causes the body to produce inadequate amounts of insulin, while type 2 diabetes leads to a lack of insulin response. Toxins such as cigarette smoke and alcohol, in addition, change the body's normal metabolism.

During catabolic metabolism, the body breaks down larger molecules into smaller ones, creating energy, facilitating muscle movement and allowing toxins to leave through the skin, lungs, kidneys and intestines. During anabolic metabolism, the body builds larger molecules out of smaller ones, promoting energy storage and cell growth.