Involuntary weight loss refers to weight loss that occurs when a person is not dieting or otherwise trying to lose weight. Because everyone's weight goes up and down slightly over time (such as during an illness), doctors typically become concerned only when people lose more than about 10 pounds (4 to 5 kilograms) or, in smaller people, 5% of their body weight. Such weight loss can be a sign of a serious physical or mental disorder. In addition to weight loss, people may have other symptoms, such as loss of appetite, fever, pain, or night sweats, due to the underlying disorder.
Causes
Most often, weight loss occurs because people take in fewer calories than their body needs. They may take in fewer calories because their appetite has decreased or because they have a disorder that prevents their digestive tract from absorbing nutrients (called malabsorption). Less often, people have a disorder that causes them to use more calories (for example, an overactive thyroid gland). Sometimes, both mechanisms are involved. For example, cancer tends to decrease appetite but also increases caloric expenditure, leading to rapid weight loss.
Almost any long-term illness of sufficient severity can cause weight loss (for example, severe heart failure or emphysema). However, these disorders have usually been diagnosed by the time weight loss occurs. This discussion focuses on weight loss as the first sign of illness. Causes can be divided into those in people who have increased appetite and those in people who have a decreased appetite.
With increased appetite, the most common unrecognized causes of involuntary weight loss are
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An overactive thyroid gland (hyperthyroidism)
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Uncontrolled diabetes
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Disorders that cause malabsorption
With decreased appetite, the most common unrecognized causes of involuntary weight loss are
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Mental disorders (for example, depression)
Evaluation
The following information can help people decide when a doctor's evaluation is needed and help them know what to expect during the evaluation.
Because many disorders can cause involuntary weight loss, doctors usually need to do a thorough evaluation.
Warning signs
When to see a doctor
What the doctor does
Doctors first ask questions about the person's symptoms and medical history. Doctors then do a physical examination. What they find during the history and physical examination often suggests a cause of the weight loss and the tests that may need to be done (see table Some Common Causes and Features of Involuntary Weight Loss).
Doctors first ask about how much weight the person has lost and over what time period. Doctors may ask about
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Changes in clothing size, appetite, and food intake
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Whether the person has difficulty swallowing
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Whether bowel patterns have changed
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What other symptoms the person has, such as fatigue, malaise, fevers, and night sweats
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Whether the person has a history of a disorder that causes weight loss
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What drugs, including prescription, over-the-counter, and recreational drugs and herbal products, the person is taking
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Whether there are any changes in the person's living situation (for example, loss of a loved one, loss of independence or job, loss of a communal eating routine)
During the physical examination, doctors check vital signs for fever, a rapid heart beat, rapid breathing, and low blood pressure. The general physical examination is very thorough because many disorders can cause involuntary weight loss. Doctors examine the heart, lungs, abdomen, head and neck, breasts, nervous system, rectum (including a prostate examination for men and testing for blood in the stool), genitals, liver, spleen, lymph nodes, joints, and skin. Doctors also assess the person's mood.
Weight is measured, and body mass index is calculated.
Some Common Causes and Features of Involuntary Weight Loss
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Cause |
Common Features* |
Tests |
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Abdominal pain, fatigue, abnormal areas of skin darkening, and light-headedness |
Blood tests |
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History of excessive alcohol consumption In men, feminization, with loss of muscle tissue, decrease in armpit hair, smooth skin, breast growth In men and women, sometimes a distended abdomen due to fluid (ascites) and small purple spots on the skin (spider angiomas) |
A doctor's examination Sometimes liver function tests and/or liver biopsy |
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Inappropriate fear of weight gain in an emaciated young woman or adolescent female and lack of normal periods |
Only a doctor's examination |
|
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Often night sweats, fatigue, and fever Sometimes bone pain at night or other organ-specific symptoms |
Organ-specific evaluation |
|
|
Sadness, fatigue, loss of sexual desire and/or pleasure, and sleep disturbance |
Only a doctor's examination |
|
|
Diabetes mellitus, type 1 (newly developed or poorly controlled) |
Increased appetite Excessive thirst and increased urination |
Measurement of the amount of sugar (glucose) in the blood |
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Drugs
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History of use |
A doctor's examination Sometimes stopping the drug |
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Fungal infections (in the lungs or bodywide) |
Fever, night sweats, fatigue, cough, and shortness of breath Often a history of living in or visiting an area where a specific fungus is common |
Usually cultures and stains Sometimes blood tests Sometimes biopsy |
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Headache, muscle pains, jaw pain when chewing, fever, and/or visual disturbances in a person over 50 |
Blood tests Sometimes temporal artery biopsy |
|
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Worm infections in the digestive tract |
Fever, abdominal pain, bloating, flatulence, and diarrhea Usually residence in or travel to developing countries |
Microscopic examination of stool |
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Fever, shortness of breath, cough, swollen lymph nodes throughout the body, diarrhea, and fungal infections |
Blood tests |
|
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Kidney disease |
Limb swelling, fatigue, itching, and sometimes frothy urine |
Blood tests and urine tests |
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Usually risk factors (for example, cranial nerve dysfunction, use of certain drugs, and aging) |
Only a doctor's examination |
|
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Diarrhea, flatulence, and sometimes greasy or oily stools |
Stool testing |
|
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Dental problems |
Tooth or gum pain Bad breath, gum disease, and missing and/or decayed teeth |
Only a doctor's examination |
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Cough and shortness of breath Fever, fatigue, and swelling of lymph nodes throughout the body |
Chest x-ray Sometimes chest CT Biopsy |
|
|
Heart valve infection (bacterial endocarditis) |
Fever, night sweats, joint pain, shortness of breath, and fatigue Often in people with heart valve disorders or who inject drugs intravenously |
Blood cultures Echocardiography |
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Thyroid gland overactivity (hyperthyroidism) |
Increased appetite Heat intolerance, sweating, tremor, anxiety, rapid heart beat, and diarrhea |
Blood tests to evaluate thyroid function |
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Fever, night sweats, cough, and coughing up blood Sometimes risk factors (for example, exposure to people with tuberculosis or residence in poor living conditions) |
Sputum culture and smear |
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*Features include symptoms and the results of the doctor's examination. Features mentioned are typical but not always present. |
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CT = computed tomography; HIV = human immunodeficiency virus; NSAIDs = nonsteroidal anti-inflammatory drugs, OTC = over-the-counter; SSRIs = selective serotonin reuptake inhibitors. |
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Testing
People's symptoms and doctors' findings on physical examination suggest the cause of weight loss in about half of people, including many people eventually diagnosed with cancer.
Screening for common cancers (for example, colonoscopy for colon cancer or mammography for breast cancer) is often done. Other testing is done depending on what disorders the doctor suspects. When the history and physical examination do not suggest specific causes, some doctors do a series of tests, including a chest x-ray, blood tests, and urinalysis, to narrow down a cause. These tests are followed by more specific tests as needed.
If all test results are normal, doctors usually reevaluate the person within a few months to see if new symptoms or findings have developed.
Treatment
The underlying disorder is treated. To help people eat more, doctors often try behavioral measures, such as encouraging people to eat, assisting them with eating, providing favorite or strongly flavored foods, and offering only small portions. If behavioral measures are ineffective, high-nutrition food supplements can be tried. Feedings through a tube inserted into the stomach are a last resort and are worthwhile only in certain specific situations. For example, tube feedings can be worthwhile if a person has a disorder that will eventually be cured or resolve, whereas tube feedings may not be worthwhile if a person stops eating because of severe Alzheimer disease.
Essentials for Older People: Involuntary Weight Loss
Incidence of involuntary weight loss increases with aging, often reaching 50% among nursing home residents. Older people are more likely to have involuntary weight loss because disorders that cause weight loss are more common among older people. There are also normal age-related changes that contribute to weight loss. Typically, many factors are involved.
Normal age-related changes that can contribute to weight loss include the following:
In addition, social isolation is common in older people, which tends to decrease food intake. Depression and dementia are very common contributing factors, particularly among nursing home residents. It is often difficult to sort out the exact contribution of specific factors.
Older people may benefit from nutritional supplements to correct vitamin deficiencies (for example, of vitamins D and B12). However, supplements should be given between meals and at bedtime. Otherwise, supplements might decrease the appetite at mealtime. Feeding and shopping assistance may also help some people.
