Unexplained weight loss may indicate an underlying medical condition. Conditions that may cause unexplained weight loss include hyperthyroidism, inflammatory bowel disease, depression, and others. Since sudden, unexplained weight loss can be caused by a variety of medical conditions, it is important to consult a doctor if you lose a significant amount of weight within 6 to 12 months, such that the weight loss exceeds 5% of your body weight. You should discuss the condition and other symptoms with your doctor. Continue reading this article to learn about the causes of unexplained weight loss.
What are the causes of unexplained weight loss?
Not all weight loss is serious. Weight loss may occur after a stressful or life-changing event. However, unintentional weight loss may be an early sign of an underlying medical condition. Some health problems that may cause unintentional weight loss include:
Inflammatory bowel disease (IBD)
Chronic inflammation caused by inflammatory bowel disease, including Crohn's disease and ulcerative colitis, can lead to unexplained weight loss. This can result from:
Malabsorption.
Decreased appetite due to pain and discomfort.
Eat a restricted diet to prevent symptoms.
Pain from complications such as strictures and blockages, which makes your body constantly use up energy.
Other digestive disorders
Some digestive disorders are caused by an autoimmune disease in which gluten in food causes the immune system to attack the body's cells, leading to weight loss and malnutrition. People with irritable bowel syndrome (IBS) or small intestinal bacterial overgrowth (SIBO) may also experience decreased appetite, leading to weight loss.
Mental health conditions
Mental health conditions such as depression and anxiety can affect the same parts of the brain that control appetite, which can lead to decreased appetite and eventually unexplained weight loss. In some people, depression or anxiety can lead to increased appetite, and symptoms vary from person to person.
Cancer
Cancer is caused by abnormal cells dividing and spreading rapidly in the body. Cancer increases inflammation and muscle wasting, and can disrupt hormones that regulate appetite. Its rapid growth rate can also increase your body's energy consumption. Unexplained weight loss of 10 pounds or more can be an early sign of some types of cancer.
Hyperthyroidism
Hyperthyroidism develops when your thyroid gland produces too much of its hormones. These hormones control many body functions, including metabolism. Hyperthyroidism causes you to burn calories and lose weight quickly, even if your appetite is good.
Rheumatoid arthritis (RA)
Rheumatoid arthritis occurs when the immune system attacks the lining of the joints, causing inflammation. This inflammatory response can increase metabolism and result in overall weight loss.
Muscle loss (muscle atrophy)
Muscle loss can lead to unexpected weight loss due to loss of muscle mass. This is often caused by not using the muscles for a period of time. It is more common in older people who do not exercise, work in office jobs or are otherwise immobile.
Type 1 diabetes
Type 1 diabetes is an autoimmune condition where the immune system attacks the insulin-producing cells in the pancreas. Without sufficient insulin, the body is unable to utilize glucose for energy, leading to elevated blood sugar levels. As a result, the body begins to break down fat and muscle for energy.
Chronic obstructive pulmonary disease (COPD)
This advanced lung disease includes emphysema and chronic bronchitis. In later stages, COPD can cause weight loss because labored breathing burns too many calories.
Endocarditis
Endocarditis is an infection, usually caused by bacteria, that inflames the inner lining of the heart (endocardium). Most people with endocarditis have a fever, and many have a decreased appetite. The high body temperature increases metabolism and fat burning, causing weight loss.
Tuberculosis (TB)
This contagious bacterial infection affects the lungs. Many people with TB experience weight loss and a decreased appetite, but the causes are not fully understood.
Addison's disease
Although rare, Addison's disease causes the immune system to damage the adrenal glands, which then can't produce enough hormones such as cortisol and aldosterone. Cortisol regulates many functions, including metabolism and appetite.
HIV
HIV attacks immune cells called T cells, reducing the body's ability to fight infection. If left untreated, HIV can progress to stage 3 disease, which can cause unexplained weight loss due to malnutrition, decreased appetite, and chronic diarrhea.
Congestive heart failure (CHF)
CHF develops when the heart can't fill with enough blood, pump blood hard enough, or both. Reduced blood flow to the digestive system can cause nausea and feeling full quickly. It can also be difficult to breathe while eating. Inflammation in damaged heart tissue can increase your metabolism and burn more calories.
Other risk factors
Some other factors can increase the likelihood of unexplained weight loss in different populations. These include:
Older age: Research suggests that 15% to 20% of adults age 65 and older experience unexplained weight loss. Smoking and low body fat may increase the likelihood.
Children and adolescents living in poverty: Living in poverty is a greater risk factor for failure to thrive, a child whose weight and height are below the norm for their age. Those who have difficulty breastfeeding: Infants who have difficulty breastfeeding may be underweight. If the infant refuses to breastfeed, it is best to consult a pediatrician to help increase and improve the child's weight.
How is unexplained weight loss diagnosed?
Diagnosing unintended weight loss usually begins with a comprehensive assessment of the body's condition, and the doctor asks about other symptoms and medical history. Some specific symptoms the patient is experiencing may help direct the doctor to order specific tests. If the cause is not clear, the doctor may recommend tests and examinations to rule out certain health conditions. Some tests may include:
A physical examination in the clinic.
Blood tests, including a complete blood count (CBC) and metabolic panel.
Urine analysis.
Depression screening.
Tests to measure blood sugar.
Tests for diseases and infections such as tuberculosis.
Imaging tests such as a CT scan or ultrasound.
Doctors may not discover the causes of unexplained weight loss. In a 2023 study, researchers found that researchers had identified the cause in only 21% of cases.
How is unintended weight loss treated?
Treatment for unexplained weight loss depends on the underlying cause. Research suggests that up to a quarter of people with unintended weight loss may not receive a specific diagnosis even after a thorough medical examination. In cases where the weight loss is severe enough that a doctor suspects a nutritional deficiency, the doctor may order dietary modifications or a nutritional supplement, even if the exact cause has not yet been determined.