Which of the following would be considered a sign of disease?

Unexplained weight loss is considered a sign of disease because it often indicates that the body is undergoing a significant change that may be associated with an underlying health issue. When a person loses weight without trying, particularly if the weight loss is substantial or occurs over a short period of time, it can suggest a range of potential medical problems, including metabolic disorders, infections, or even certain types of cancer.

In contrast, regular appetite, normal weight, and consistent energy levels typically suggest that a person's health is stable and functioning normally. These factors are associated with a well-functioning bodily system, as they indicate that the body is receiving the necessary nutrients and is maintaining balance. Thus, unexplained weight loss stands out as a critical indicator that should prompt further investigation into possible health concerns.