What is the term for the phase when the body reduces complex substances to simpler substances, often releasing energy?

The term that describes the phase when the body reduces complex substances to simpler substances, often releasing energy, is catabolism. This process involves the breakdown of larger molecules, such as carbohydrates, proteins, and fats, into smaller units like glucose, amino acids, and fatty acids. During catabolism, the energy stored in the bonds of these complex molecules is released and can be utilized by the body for various functions, including physical activity and maintaining metabolic processes.

In contrast, metabolism refers to the overall set of chemical reactions that occur in the body, encompassing both catabolic and anabolic processes. Anabolism, on the other hand, is the phase where simpler substances are built up into more complex substances, requiring an input of energy. Digestion is specific to the process of breaking down food into nutrients, but it is not synonymous with the broader process of catabolism or the release of energy from these molecules.