Why is unexplained weight loss a symptom of cancer?

Why is unexplained weight loss a symptom of cancer?

John A. Chabot
Endocrinology Diabetes & Metabolism
Unexplained weight loss is a common symptom in many cancers. It is often accompanied by general loss of appetite and fatigue. The weight loss can be caused by cancerous cells that deprive healthy cells of required nutrients. Unexplained weight loss can also be caused by some infections or parasites in the digestive tract.