What condition is associated with both unintentional weight loss and anorexia?

Malignant tumors are associated with both unintentional weight loss and anorexia due to a variety of mechanisms. Cancer can lead to significant weight loss as it often increases metabolic demands on the body while simultaneously causing a loss of appetite. The presence of a tumor can also affect the body's energy balance, skewing it towards catabolism (the breakdown of body tissues) rather than anabolism (the synthesis of new tissues). Additionally, cancer can induce systemic changes such as the release of cytokines and other substances that influence appetite and metabolism, often leading to cachexia, a complex syndrome characterized by weight loss, muscle wasting, and decreased appetite.

In contrast, conditions such as dust allergies typically do not impact appetite or body weight significantly. The seasonal flu may cause temporary loss of appetite but is often accompanied by other acute symptoms and does not usually lead to substantial weight loss unless prolonged. Chronic fatigue syndrome can cause fatigue and discomfort but is not primarily characterized by significant weight loss or anorexia. Therefore, malignant tumors are the most directly linked to the combination of unintentional weight loss and appetite changes.