Unexplained weight loss

Medical quality assurance by Dr. Albrecht Nonnenmacher, MD at December 10, 2015
StartSymptomsUnexplained weight loss

Unexplained or unintentional weight loss is characterized by a significant, often rapid decrease in body weight with no intentional cause. This means losing weight without dieting or exercising, or other direct, controlled means. Unexplained weight loss is usually due to an underlying, chronic condition, but it can often be explained by a short-term ailment, such as a stomach virus or a significant respiratory infection.


Definition & Facts

Unexplained weight loss is essentially just that - when a patient loses body weight without directly trying. Often this is the result of lack of appetite, but it can also happen despite eating at or above the base amount of calories needed to maintain weight.

Because the causes are often related to undiagnosed and underlying chronic conditions, the weight loss itself might be the only indication that there is a problem. Though unintentional weight loss itself is a problem, it's very rarely its own disease by itself and almost always a symptom of something bigger.


Many diseases, both acute and chronic, can cause unintentional weight loss. Short-term causes include:

These are diseases and conditions that are overt, and something of which the patient would be aware. Vomiting and diarrhea are often the main culprit here, causing a two-fold problem between lack of appetite and inability to keep food down.

Weight loss associated with other infections often gets better when the disease itself clears up, allowing for regain of appetite and normal eating to resume. Long-term causes of unexplained weight loss include but are not limited to:

The potential causes are too numerous to name, but these are some of the most common culprits to unintentional weight loss. The weight loss or wasting itself can be accompanied by a wide range of other symptoms, depending on the underlying cause. These might include fever, chills, changes in appetite or bowel movements, difficulty sleeping, general lack of interest in daily activities, or chronic infections.

When to see a doctor

At the first point it is noticed that weight has been lost with no known cause, a doctor should be consulted. Though the cause can be minor, it still needs to be addressed and a plan of action created. This goes in particular for potentially serious causes, such as AIDS or cancer, when early diagnosis and treatment can save lives.

If reduction in weight is accompanied by one of the above-listed symptoms, it is especially important. The doctor will need to be informed as much as possible about the diet and activity that came before the weight loss, as well as any other outside factors that could be an influence, like stress or illness.

Depending on the factors that the doctor sees influencing the weight loss, a handful of tests for various might be ordered. Ranging from a simple blood draw to a dietary or nutritional analysis, to different diagnostic procedures, such as X-rays or an endoscope to check for ulcers.

Treatment & Therapy

Depending on the cause, the treatment can vary wildly. If there are nutritional deficiencies apparent, the doctor will likely set up appointments with a dietician or nutritionist. Drugs or therapies to increase appetite or supplements to ensure adequate intake of key vitamins and minerals may also be prescribed.

If the underlying cause is hormonal, as it is in hypothyroidism, the doctor will likely prescribe medication. For more acute causes, like with viruses or food poisoning, rest, fluids, and over-the-counter pain medication will help the patient recover and feel better during this period, which will help bolster the desire to eat. Medication for the treatment of diarrhea might also be prescribed, whether the cause is acute or chronic.

No matter the cause, the key components of treatment are improving appetite and creating a more favorable environment internally for nutrient absorption. Drugs to treat underlying disorders that cause loss of appetite and nutritional correction through high-calorie meal replacements are often given. In the case of diseases like celiacs, dietary changes are necessary to ensure proper absorption of nutrients and to prevent further damage and wasting.

Often, lifestyle changes as well as dietary changes might be necessary to correct and treat the primary cause, such as avoiding certain food groups or chronic stress.

Prevention & Prophylaxis

Though weight loss itself isn't a disease, once the underlying cause has been determined, it can be managed. Planning meals around periods of known appetite loss, like with chemotherapy, can help make certain that calories and nutrients are received at a time when they're going to be accepted. Taking an antiemetic drug - one that prevents vomiting - prior to treatments or other causes of loss of appetite can prevent the weight loss associated with malnutrition.

Dietary steps to be taken to prevent weight loss include food journals, intentionally eating more of foods that are high in calorie and energy density, and intake of meal replacement fluids. Often meal replacements are blended drinks that are high in proteins and a blend of vitamins and minerals that help plug in the nutritional gaps in a patient's diet. The ultimate goal of treating this weight loss is to find out the cause, and being fixing that.

Once that disease is treated, or at least under control, the weight loss will often resolve on its own. Barring that, increasing calories, administration of appetite-increasing drugs, or discomfort-alleviating medication will be the next step. When the other symptoms of the primary disease are treated, then the wasting can be treated, prevented, and then reversed.

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