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Involuntary Weight Loss


Michael R. Wasserman

, MD, California Association of Long Term Care Medicine

Reviewed/Revised Feb 2023
Topic Resources

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 about involuntary weight loss 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 emotional 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 of Involuntary Weight Loss

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 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

With decreased appetite, the most common unrecognized causes of involuntary weight loss are

Evaluation of Involuntary Weight Loss

The following information can help people with involuntary weight loss 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

In people with involuntary weight loss, certain symptoms and characteristics are cause for concern. They include

  • Fever and night sweats

  • Bone pain

  • Shortness of breath, cough, and coughing up blood

  • Excessive thirst and increased urination

  • Headache, jaw pain when chewing, and/or new vision disturbances (for example, double vision, blurred vision, or blind spots) in a person over 50

When to see a doctor

People who have warning signs should see a doctor right away. People who have no warning signs should see a doctor when possible. Typically a delay of a week or so is not harmful.

What the doctor does

Doctors first ask questions about the person's symptoms and medical and social 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 ).

Doctors first ask about how much weight the person has lost and over what time period. Doctors may ask about

  • Changes in clothing size, appetite, and food intake

  • Whether the person has difficulty swallowing

  • Whether bowel patterns have changed

  • What other symptoms the person has, such as fatigue, malaise, fevers, and night sweats

  • Whether the person has a history of a disorder that causes weight loss

  • What drugs, including prescription, over-the-counter, and recreational drugs and herbal products, the person is taking

  • 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.



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 of Involuntary Weight Loss

The underlying disorder causing involuntary weight loss 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:

  • Decreased sensitivity to certain appetite-stimulating mediators and increased sensitivity to certain inhibitory mediators

  • A decreased rate of gastric-emptying (prolonging the feeling of fullness)

  • Decreased sensitivities of taste and smell

  • Loss of muscle mass (sarcopenia)

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. Dental problems (for example, periodontitis) become more common with aging and can compromise nutrient intake and digestion. It is often difficult to sort out the exact contribution of specific factors.

Key Points

  • Involuntary weight loss exceeding 10 pounds or 5% of body weight over a period of a few months is cause for concern.

  • Tests are done based on the person's symptoms and findings on physical examination.

  • Extensive testing is not usually needed to identify the cause of weight loss.

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