Definition

• Unexpected weight loss is the unintentional or involuntary decrease in body weight (i.e., without the use of certain drugs including thyroxine and diuretics, a decrease of calory intake or an increase of physical activity) of > 5% of usual body weight over a time period of 6–12 consecutive months

• Malignancy (e.g., lung cancer, colorectal cancer)

• Endocrinopathies (e.g., hyperthyroidism, hypocortisolism, diabetes mellitus)

• Gastrointestinal conditions (e.g., gastritis, celiac disease, Crohn disease, ulcerative colitis)

• Conditions with organ failure (e.g., COPD, renal failure)

• Infectious diseases (e.g., tuberculosis, HIV)

• Inherited disorders (e.g., cystic fibrosis)

• Psychiatric conditions (e.g., schizophrenia, bipolar disorder, major depression)

substance abuse (e.g., nicotine addiction, amphetamines use disorder, cocaine use disorders)