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Involuntary Weight Loss


Michael R. Wasserman

, MD, Los Angeles Jewish Home

Last full review/revision Mar 2021| Content last modified Mar 2021
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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 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). 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 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

  • 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.


Some Common Causes and Features of Involuntary Weight Loss


Common Features*


Abdominal pain, fatigue, abnormal areas of skin darkening, and light-headedness

Blood tests

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 tests and/or liver biopsy

Inappropriate fear of weight gain in an emaciated young woman or adolescent female and lack of normal periods

Only a doctor's examination

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


  • Drugs of abuse: Amphetamines, cocaine, and opioids

  • Herbal and OTC products: Aloe, caffeine, cascara, chitosan, chromium, dandelion, ephedra, 5-hydroxytryptophan, garcinia, guarana, guar gum, glucomannan, herbal diuretics, ma huang, pyruvate, St. John's wort, and yerba mate

  • Prescription: Antiretroviral drugs, cancer chemotherapy drugs, digoxin, exenatide, levodopa, liraglutide, metformin, NSAIDs, SSRIs, topiramate, and zonisamide

History of use

A doctor's examination

Sometimes stopping the drug

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

Headache, muscle pains, jaw pain when chewing, fever, and/or visual disturbances in a person over 50

Blood tests

Sometimes temporal artery biopsy

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

Fever, shortness of breath, cough, swollen lymph nodes throughout the body, diarrhea, and fungal infections

Blood tests

Kidney disease

Limb swelling, fatigue, itching, and sometimes frothy urine

Blood tests and urine tests

Usually risk factors (for example, cranial nerve dysfunction, use of certain drugs, and aging)

Only a doctor's examination

Diarrhea, flatulence, and sometimes greasy or oily stools

Stool testing

Dental problems

Tooth or gum pain

Bad breath, gum disease, and missing and/or decayed teeth

Only a doctor's examination

Cough and shortness of breath

Fever, fatigue, and swelling of lymph nodes throughout the body

Chest x-ray

Sometimes chest CT


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


Thyroid gland overactivity (hyperthyroidism)

Increased appetite

Heat intolerance, sweating, tremor, anxiety, rapid heart beat, and diarrhea

Blood tests to evaluate thyroid function

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

* Features include symptoms and the results of the doctor's examination. Features mentioned are typical but not always present.

CT = computed tomography; HIV = human immunodeficiency virus; NSAIDs = nonsteroidal anti-inflammatory drugs, OTC = over-the-counter; SSRIs = selective serotonin reuptake inhibitors.


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. 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.

Key Points about Involuntary Weight Loss

  • 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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