The chemical decomposition of complex substances by the body to form simpler ones, accompanies by the release of energy. The substances broken down include nutrients in food (carbohydrates, proteins etc as well as the body's storage products (such as glycogen).
Unit 2,
Reference: Oxford Concise Colour Medical Dictionary (7th Edition, Kindle Edition) Oxford University Press 2020 ISBN-13: 978-0198836629, p1136
