Most causes of IWL belong to one of four categories: (1) malignant neoplasms, (2) chronic inflammatory or infectious diseases, (3) metabolic disorders (e.g., hyperthyroidism and diabetes), or (4) psychiatric disorders (Table 56-1). Not infrequently, more than one of these causes can be responsible for IWL. In most series, IWL is caused by malignant disease in a quarter of patients and by organic disease in one-third, with the remainder due to psychiatric disease, medications, or uncertain causes.
TABLE 56-1Causes of Involuntary Weight Loss ||Download (.pdf) TABLE 56-1Causes of Involuntary Weight Loss
Inflammatory bowel disease
Endocrine and metabolic
Chronic congestive heart failure
Chronic obstructive pulmonary disease
Subacute bacterial endocarditis
Nonsteroidal anti-inflammatory drugs
Serotonin reuptake inhibitors
Angiotensin-converting enzyme inhibitors
Disorders of the mouth and teeth
Decreased taste and smell
Psychiatric and behavioral
Increased activity or exercise
The most common malignant causes of IWL are gastrointestinal, hepatobiliary, hematologic, lung, breast, genitourinary, ovarian, and prostate. Half of all patients with cancer lose some body weight; one-third lose more than 5% of their original body weight, and up to 20% of all cancer deaths are caused directly by cachexia (through immobility and/or cardiac/respiratory failure). The greatest incidence of weight loss is seen among patients with solid tumors. Malignancy that reveals itself through significant weight loss usually has a very poor prognosis.
In addition to malignancies, gastrointestinal causes are among the most prominent causes of IWL. Peptic ulcer disease, inflammatory bowel disease, dysmotility syndromes, chronic pancreatitis, celiac disease, constipation, and atrophic gastritis are some of the more common entities. Oral and dental problems are easily overlooked and may manifest with halitosis, poor oral hygiene, xerostomia, inability to chew, reduced masticatory force, nonocclusion, temporomandibular joint syndrome, edentulousness, and pain due to caries or abscesses.
Tuberculosis, fungal diseases, parasites, subacute bacterial endocarditis, and HIV are well-documented causes of IWL. Cardiovascular and pulmonary diseases cause unintentional weight loss through increased metabolic demand and decreased appetite and caloric intake. Uremia produces nausea, anorexia, and vomiting. Connective tissue diseases may increase metabolic demand and disrupt nutritional balance. As the incidence of diabetes mellitus increases with aging, the associated glucosuria can contribute to weight loss. Hyperthyroidism in the elderly may have less prominent sympathomimetic features and may present as “apathetic hyperthyroidism” or T3 toxicosis (Chap. 405).
Neurologic injuries such as stroke, quadriplegia, and multiple sclerosis may lead to visceral and autonomic dysfunction that can impair caloric intake. Dysphagia from these neurologic insults is a common mechanism. Functional disability that compromises activities of daily living (ADLs) is a common cause of undernutrition in the elderly. Visual impairment from ophthalmic or central nervous system disorders such as a tremor can limit the ability of people to prepare and eat meals. IWL may be one of the earliest manifestations of Alzheimer’s dementia.
Isolation and depression are significant causes of IWL that may manifest as an inability to care for oneself, including nutritional needs. A cytokine-mediated inflammatory metabolic cascade can be both a cause of and a manifestation of depression. Bereavement can be a cause of IWL and, when present, is more pronounced in men. More intense forms of mental illness such as paranoid disorders may lead to delusions about food and cause weight loss. Alcoholism can be a significant source of weight loss and malnutrition.
Elderly persons living in poverty may have to choose whether to purchase food or use the money for other expenses, including medications. Institutionalization is an independent risk factor, as up to 30–50% of nursing home patients have inadequate food intake.
Medications can cause anorexia, nausea, vomiting, gastrointestinal distress, diarrhea, dry mouth, and changes in taste. This is particularly an issue in the elderly, many of whom take five or more medications.