Weight loss is widely believed to be beneficial for overall health and wellbeing. Most people lose weight when they increase their levels of physical activity and lower their calorie intake. However, there are also some who lose weight without making any intentional or conscious effort. In many cases, unexplained weight loss happens after a life-changing or stressful event such as the loss of a loved one, divorce, etc. It can also be a result of an underlying medical condition. For this reason, it is important to know more about the potential causes and consequences of unexplained weight loss.

What is unexplained weight loss?

Unexplained weight loss is defined as the unintentional loss of body weight even when the person is not trying to lose weight either by changing their dietary patterns or altering their physical activity routine. According to physicians, loss of at least 5% of body weight over a period of 6 months to 1 year is considered “unexplained”.

Possible causes of unexplained weight loss

• Hyperthyroidism

Hyperthyroidism, commonly known as overactive thyroid, is a condition in which the thyroid gland produces more hormones than normal. The hormones secreted by the thyroid gland help regulate the body’s metabolism. Excess release of these hormones revs up the metabolism which, in turn, causes the body to burn more energy and calories than usual. This results in unintentional or unexplained weight loss. There are certain conditions that can cause hyperthyroidism, such as Graves' disease, thyroditis, excess intake of iodine, medication error, and pregnancy.

• Diabetes

Diabetes is broadly classified into two major categories: Type 1 and Type 2. Unexplained weight loss can occur in both types, however, it is more common in people with Type 1 diabetes. Type 1 diabetes is an autoimmune disease that causes the immune system to attack cells in the pancreas that make insulin. Without insulin, the body is unable to utilize glucose from food into energy. This results in high blood glucose levels. The excess glucose in the blood is expelled from the body by the kidneys through urine. As excess glucose leaves the body, so do calories. Over time, this results in unintentional weight loss.

• Muscle loss

Muscle loss, also known as muscle atrophy or muscle wasting, is a condition in which the muscle tissues shrink or waste away. The condition occurs when a muscle is not used for a while. It mostly affects people who don’t exercise, work desk jobs, or are bedridden. Loss of comparatively heavy muscle tissue can result in unexplained weight loss.

Possible causes of muscle loss include malnutrition, injury-induced inactivity, aging, burns, stroke, nerve damage, osteoarthritis, rheumatoid arthritis, osteoporosis, multiple sclerosis, amyotrophic lateral sclerosis (ALS), etc. The condition can be prevented or reversed by proper nutrition, regular exercise, and physical therapy.

• Depression

Depression, also known as clinical depression, is a common mental disorder that is characterized by a pervasive low mood. The condition affects how an individual feels, thinks, and performs daily activities. Common symptoms of depression are constant feelings of sadness, loss of interest in favorite activities, low energy levels, poor concentration, muscle pain, irritability, sleeping too little or too much, and frequent thoughts of suicide.

The mental disorder can also cause unexplained weight loss. It can affect appetite and trigger changes in eating habits that can lead to weight loss. Researchers say that people who are suffering from depression may have associated suppressed interplay among the hypothalamus, pituitary gland, and adrenal glands. This interplay is believed to affect the function of the gastrointestinal (GI) or digestive tract.

• Inflammatory bowel disease (IBD)

Inflammatory bowel disease (IBD) is a term that is used to refer to chronic inflammatory disorders of the gastrointestinal (GI) or digestive tract. The most common cause of IBD is immune system dysfunction. Crohn’s disease and ulcerative colitis are the two main types of IBD. While Crohn’s disease can trigger inflammation in different areas of the GI tract, ulcerative colitis mostly only affects the colon (large intestine) and rectum. Common symptoms of IBD include fatigue, fever, frequent diarrhea, stomach pain, and bloody stools.

The condition triggers weight loss by adversely affecting the body’s ability to digest and absorb nutrients from the food. IBD also disrupts ghrelin, the hunger hormone, and leptin, the satiety hormone which results in decreased appetite and weight loss. Since there is no known cure for both types of IBD, treatment usually focuses on nutritional support, medication, and in rare cases, surgery.

• Cancer

Cancer is a term that is used to refer to a collection of related diseases in which abnormal and mutated cells multiply aggressively and eventually invade healthy tissue. According to the American Cancer Society, unexplained weight loss is one of the first signs of cancer. Weight loss is especially common in cancers of the blood, pancreas, lung, colon, liver, stomach, pancreas, and esophagus.

The cancerous cells increase inflammation in the body. The inflammation promotes muscle wasting and disrupts appetite-regulating hormones. A growing tumor can also increase the resting energy expenditure (REE) - the amount of energy burned by the body while at rest. A high REE makes the body burn more calories leading to weight loss.

• Rheumatoid arthritis

Rheumatoid arthritis (RA) is an autoimmune and chronic inflammatory disease in which the immune system attacks the healthy cells lining the joints. Swelling, stiffness, and pain in joints are the major symptoms of RA. Chronic inflammation caused by RA speeds up the metabolism. The increased metabolism forces the body to use more energy and burn more calories. This results in inexplicable weight loss. Moreover, muscle loss triggered by RA can also worsen weight loss in people who can’t engage in physical activity because of pain and stiffness in joints.

Other possible causes of unexplained weight loss include Addison’s disease, Celiac disease, chronic obstructive pulmonary disease (COPD), tuberculosis, endocarditis, and heart failure.

Diagnosis

A person experiencing unexplained weight loss should ideally contact a physician if they have lost at least 5% of their body weight over the last 6 to 12 months without making any effort. During the consultation, the physician will likely ask questions related to the medical history of the person. He may also perform some physical examinations. The diagnosis process will involve tests such as complete blood count (CBC) test, thyroid panel, blood glucose, urinalysis, kidney function, liver function, inflammation (C-reactive protein), etc.

Imaging tests such as chest X-ray, computerized tomography (CT), and magnetic resonance imaging (MRI) scan may be conducted to rule out certain medical conditions such as rheumatoid arthritis, hyperthyroidism, and cancer. Certain endoscopic procedures such as upper GI endoscopy or colonoscopy can also be prescribed to figure out if the unexplained weight loss is triggered by any gastrointestinal problem or not.

Treatment and takeaway

Unexplained weight loss is usually treated by identifying and addressing the underlying medical condition. If the diagnosis process fails to identify any underlying condition, then the physician will most likely recommend a wait-and-watch approach. He may also suggest following a specific diet during that period.

It is completely normal for the body weight to fluctuate occasionally. While losing weight without making any conscious effort may sound pleasing, it is important to determine the exact cause if a person loses more than 5% of their body weight in an inexplicable manner. Unexplained weight loss can be a symptom or a result of a serious illness such as cancer, IBD, rheumatoid arthritis, etc. Therefore, one must consult a doctor when they experience unintended weight loss.