Cachexia is a state of malnutrition and wasting characterized by weight loss, muscle atrophy, fatigue, weakness, and loss of appetite. The loss of body mass cannot be reversed with nutrition, indicating an underlying disease. Cachexia increases the risk of death and is seen with illnesses like cancer, infections, and autoimmune disorders. Cancer specifically causes muscle loss in cachexia patients, even when they receive nutrition through feeding tubes or IVs. Treating the underlying illness is important for treating cachexia.