Specific diseases

• As chronic obstructive pulmonary disease (COPD) advances, about 35% of patients experience severe weight loss called pulmonary cachexia, including diminished muscle mass.Around 25% experience moderate to severe weight loss, and most others have some weight loss.Greater weight loss is associated with poorer prognosis.Theories about contributing factors include appetite loss related to reduced activity, additional energy required for breathing, and the difficulty of eating with dyspnea (labored breathing).
• Cancer, a very common and sometimes fatal cause of unexplained (idiopathic) weight loss. About one-third of unintentional weight loss cases are secondary to malignancy. Cancers to suspect in patients with unexplained weight loss include gastrointestinal, prostate, hepatobilary (hepatocellular carcinoma,pancreatic cancer), ovarian, hematologic or lung malignancies.
• People with HIV often experience weight loss, and it is associated with poorer outcomes.^[11] Wasting syndrome is an AIDS-defining condition.
• Gastrointestinal disorders are another common cause of unexplained weight loss – in fact they are the most common non-cancerous cause of idiopathic weight loss.^{[citation needed]} Possible gastrointestinal etiologies of unexplained weight loss include: celiac disease, peptic ulcer disease, inflammatory bowel disease (crohn's disease and ulcerative colitis), pancreatitis, gastritis, diarrhea and many other GI conditions.
• Infection. Some infectious diseases can cause weight loss. Fungal illnesses, endocarditis, many parasitic diseases, AIDS, and some other subacute or occult infections may cause weight loss.
• Renal disease. Patients who have uremia often have poor or absent appetite, vomiting and nausea. This can cause weight loss.
• Cardiac disease. Cardiovascular disease, especially congestive heart failure, may cause unexplained weight loss.
• Connective tissue disease
• Neurologic disease, including dementia
• Oral, taste or dental problems (including infections) can reduce nutrient intake leading to weight loss