Weight Loss

I. Background
Unintentional weight loss is generally considered to be significant when greater than 5% of body weight is lost over a period of 6 months or less. It is often associated with increased morbidity and mortality especially among the elderly. Perceived weight loss should be verified before initiating a workup, because 50% of patients with perceived weight loss do not have true weight loss. Of patients with confirmed weight loss, an explanation is generally found in 75% of cases. In 25% of patients an explanation is never found. If a physical cause is present, it is usually discovered within 6 months (1,2,3).
II. Pathophysiology
The various conditions that cause unintentional weight loss do so through one or more of the following mechanisms: inadequate caloric intake, excessive metabolic demands, or loss of nutrients through urine or stool. Other conditions that cause weight loss include:
A. Malignant conditions
Cancer is often the patient's or physician's greatest fear. Malignancy is the cause for unintentional weight loss in 16% to 36% of cases (1,2,3). Although any cancer can cause weight loss, the more common malignancies to consider are gastrointestinal (GI), leukemia or lymphoma, lung, ovarian, and prostate cancers.
B. Benign medical conditions
Many chronic medical conditions can cause anorexia, nausea, diarrhea, or postprandial symptoms which discourage the patient from eating. Medical conditions may also necessitate limiting salt, fat, or sugar in the diet, leaving the patient less inclined to eat.
  • GI disorders account for the most common physical cause of weight loss affecting approximately 17% of patients (4). These include:
    • Peptic ulcer disease/gastroesophageal reflux disease
    • Inflammatory bowel disease
    • Hepatitis, cholestasis
    • Pancreatitis
    • Atrophic gastritis
    • Constipation.
  • Cardiac diseases, especially congestive heart failure.
  • Respiratory diseases, such as chronic obstructive pulmonary disease.
  • Renal disease.
  • Neuromuscular disorders may affect the ability to swallow. These include:
    • Scleroderma
    • Polymyositis
    • Systemic lupus erythematosus.
  • Endocrine disorders can increase metabolic rate or cause nutrient loss. These include:
    • Hyperthyroidism
    • Diabetes mellitus
    • Other causes, such as pheochromocytoma, panhypopituitarism, adrenal insufficiency, and hyperthyroidism.
  • Infection, especially tuberculosis, fungal disease, subacute bacterial endocarditis, and any prolonged febrile illness can decrease appetite and increase metabolic demand. Human immunodeficiency virus infection is a special consideration with patients having multiple causes for weight loss.
  • Neurologic conditions (e.g., dementia, Parkinson's disease, stroke) can cause weight loss secondary to apathy, decreased appetite, or difficulty swallowing.
  • Medications can cause anorexia, nausea, abdominal pain, or diarrhea, or inhibit gastric emptying.
C. Psychiatric causes
These are responsible for weight loss in 10% to 20% of patients (1,2,3).
  • Depression is the most common psychiatric cause.
  • Substance abuse, especially alcoholism, and bereavement are other causes.
D. Social and age related causes
These include the following:
  • Financial hardship.
  • Diminished sense of taste and smell.
  • Functional inability to shop or prepare food.
  • Poor dentition.
III. Evaluation
A. History
A detailed history should be obtained from the patient and caregivers if applicable. Special attention should be given to the types and quantity of food consumed; alcohol use; history of cigarette smoking (current and remote); exercise patterns; medications; presence of nausea, vomiting, diarrhea, early satiety, difficulty swallowing; history of GI illnesses or previous abdominal surgery; cardiac history; respiratory history; history of kidney disease; depressive symptoms; social situation, including financial resources; and functional ability to shop for groceries and prepare meals.
B. Physical examination
  • Document weight and compare it to previous weights.
  • Perform a thorough physical examination, paying special attention to an oral examination, especially dentition; a respiratory examination; a cardiac examination; a GI examination; a psychologic examination; and an evaluation of cognitive function, especially if the patient is elderly.
C. Testing
Extensive undirected laboratory testing is not indicated and is rarely helpful.
  • Initial laboratory tests should include:
    • Complete blood count
    • Comprehensive metabolic profile
    • Thyroid-stimulating hormone
    • Urinalysis
    • Fecal occult blood testing.
  • Other laboratory tests as indicated by history or physical examination may include:
    • Chest x-ray, which may be helpful, especially with a history of cigarette smoking, or a new or different cough or dyspnea.
    • Appropriate age and gender based screening (e.g., mammography, colonoscopy).
    • Other tests as indicated by history (e.g., upper GI endoscopy).
IV. Diagnosis
Diagnosis of weight loss is made by verifying that a loss of more than 5% of body weight has occurred. A thorough history and physical examination and directed laboratory and ancillary tests result in an explanation approximately 75% of the time. Malignancy is the cause of weight loss in 16% to 36% of cases. Psychiatric causes, usually depression, is the cause in 10% to 20% of the cases. An organic cause other than malignancy is present in 30% to 50% of cases. Twenty-five percent of the time no identifiable cause is found. If a physical cause is responsible, but not identified on initial workup, it usually becomes evident within 6 months (4).
References
1. Marton KE, Sox HC Jr, Krupp JR. Involuntary weight loss: diagnostic and prognostic significance. Ann Intern Med 1981;95:568 - 574.
2. Rabinovitz M, Pitlik SD, Leifer M, et al. Unintentional weight loss. A retrospective analysis of 154 cases. Arch Intern Med 1986;146:186 - 187.
3. Thompson MP, Morris LK. Unexplained weight loss in the ambulatory elderly. J Am Geriatr Soc 1991;39:497 - 500.
4. Huffman GB. Evaluating and treating unintentional weight loss in the elderly. Am Fam Physician 2002;65:640 - 650.
5. Wise GR, Craig D. Evaluation of involuntary weight loss. Where do you start? Postgrad Med J 1994;95:143 - 146, 149 - 150.
6. Reife CM. Involuntary weight loss. Med Clin North Am 1995;79(2):299 - 313.
7. Bouras EP, Lange SM, Scolapio JS. Rational approach to patients with unintentional weight loss. Mayo Clin Proc 2001;76:923 - 929.