The word metabolism is used a lot, especially in the weight-loss industry. It is helpful to parse out what exactly the metabolism is to approach claims about a product's ability to alter the metabolism. Alterations in the metabolism can occur through several factors, but it is important to consult with a physician for health-related conditions and help gaining or losing weight.
Metabolism
Broadly, metabolism is the way the body processes chemicals including ingested foods. DNA, cell membranes, proteins, energy carrying molecules, toxins and waste products, for example, all undergo chemical reactions in the body. In other words, they are metabolized. The metabolism can break chemicals down, called catabolism, or build chemicals up, called anabolism. Sugar can be broken down into water and carbon dioxide, which releases energy, or it can be linked together to form a huge carbohydrate molecule called glycogen in the liver or muscles, which stores sugar for later use.
Catabolism
Catabolism is usually performed by the body to rid it of unneeded or toxic substances or to release energy. Once amino acids, the building blocks of proteins, are damaged or no longer needed, they can be broken down into urea, carbon dioxide, sulfuric acid and phosphoric acid, all waste products. These are secreted from the body. The sugar glucose undergoes numerous chemical reactions and, along with oxygen, is used to synthesize adenosine-5'-triphosphate, or ATP, the main energy carrier of the cell. If glucose levels are low, the body can break down other chemicals, such as protein or fat.
Anabolism
Anabolic processes are a set of biochemical pathways that construct larger molecules from smaller ones. Generally this requires energy. For example, after strenuous activity, the body builds proteins in the muscle to allow them to perform more work. The division of cells, such as the creation of blood cells in the bone marrow, requires anabolic processes to replicate DNA, protein, fats, and other constituents of the cells.
Factors
The metabolism is determined by the interplay of genetics, hormones, environment, diet, exercise, health and numerous other factors. If a biochemical pathway is changed, that is an alteration to metabolism. However, as commonly used, an alteration often means speeding up or slowing down metabolism. Most products that claim to do this cannot back up their claims with scientific evidence. Medications for weight loss tend to affect the appetite and caloric intake more than metabolism. Weight loss is largely dependent on the balance of calories taken in through the diet and the calories used in activities throughout the day.
References
- "Physiology, 4th Ed."; Linda S.Costanzo; 2008
- "Lehninger Principles of Biochemistry, 4th Ed."; David L. Nelson, et al.; 2004
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