How is "body composition" defined?

Body composition is defined as the proportion of fat, muscle, and bone in a person's body. This definition highlights that body composition provides a more detailed understanding of a person's physical makeup beyond just their overall weight. It is an essential aspect of health because different body compositions can indicate levels of fitness and health risks. For example, a higher proportion of muscle relative to fat is generally associated with better fitness and health outcomes.

While water content and overall weight are important in the context of fitness and health, they do not sufficiently describe body composition as a whole. Additionally, levels of cardiovascular fitness refer to the efficiency of the heart and lungs during exercise and do not directly relate to how various tissues are distributed in the body. Thus, option B accurately captures the multifaceted nature of body composition and its relevance in assessing health and fitness.