Loosing weight may be a warning sign of cancer. does the person eat less or does the body's metabolism speed up to cause weight loss? thank-you.

Often both: Tumor does have higher metabolic rate than rest of the body. Tumor related inflammation often releases mediators that raises the metabolism of the rest of the body as well and depresses appetite.

Loss of appetite: In presence of a malignant tumor, wt. loss is common even without other symptoms. Here depending on the malignant lesion loss of weight and appetite occur. The resulting process is referred to a cachexia or wasting syndrome in a patient not actively trying to lose wt. Tumors associated with cachexia found to produce TNF . When sequenced, the TNF was found to have same sequence as Cachectin