Unexplained Weight Loss: Common Causes, Symptoms, and When to Worry

Weight loss is the reduction of body weight in a planned or unplanned manner and generally occurs due to an imbalance between energy intake and expenditure. It may develop as a result of physiological, metabolic, or pathological processes and is defined by a measurable decrease in weight over a certain period.

Unintentional weight loss is characterized by an individual losing weight without making changes to diet or exercise and may be a clinical sign of an underlying disease. Endocrine disorders, gastrointestinal absorption problems, and malignancies are among the main medical causes that may lead to this condition.

The causes of rapid weight loss include hyperthyroidism, diabetes, chronic infections, and severe psychiatric conditions. Conditions associated with an increased metabolic rate or loss of appetite may cause a significant reduction in body mass within a short period and require systemic evaluation.

Weight loss associated with chronic diseases is frequently seen in long-term illnesses such as cancer, chronic kidney failure, and heart failure. During this process, muscle mass may decrease, the immune system may weaken, and general health may deteriorate; therefore, early diagnosis and a holistic approach are important.

What Is Unintentional Weight Loss and Why Is It So Important?

We all gain and lose weight from time to time. Seasonal changes, stressful periods, or minor changes in dietary habits may affect the numbers on the scale. However, when we medically refer to “unintentional weight loss,” we are talking about a much more specific and alarming condition. If a person is not following a special diet program, is not spending hours at the gym, in other words, is not making a specific effort to lose weight, and despite this has lost more than 5 percent of their body weight within the last 6 to 12 months, this indicates that there is a problem.

For example, if an individual weighing 80 kilograms loses 4-5 kilograms without any effort within six months and drops to around 75 kilograms, this falls into the category of “unexplained weight loss” for us. From the perspective of thoracic surgery, this condition is not merely the loss of fat tissue. What we actually fear and consider dangerous is the loss of muscle mass. The body begins to burn its own building blocks, namely its muscles, in order to fight an internal disease or manage the metabolic chaos caused by that disease.

The importance of this condition lies here: Weight loss may often be the first and only symptom of a disease. Before a cough begins and before pain is felt, the body metabolically sends the message, “I am being depleted.” In addition, this condition is vitally important in our surgical planning. It is much more difficult for a patient whose muscle and fat stores are depleted to tolerate major lung or esophageal surgery compared to a strong patient. The recovery process is prolonged, and wound healing is delayed. Therefore, for us, weight loss is not merely a symptom but a parameter that completely changes the treatment strategy.

Why Does the Body Lose Weight on Its Own?

Under normal conditions, our body has a remarkable balance mechanism. The calories we consume and the energy we expend are like the two sides of a scale. However, malignant diseases or chronic infections developing in the chest cavity suddenly disrupt this balance. In medical terminology, we call this condition “cachexia.” Cachexia is very different from simple starvation. A starving person recovers when they eat, but a patient experiencing cachexia may be unable to continue gaining weight even if they eat.

The main reason for this is the state of “inflammation” created by the tumor or disease. Cancer cells seize all of the body’s energy resources in order to multiply uncontrollably. The body, on the other hand, activates the immune system at full capacity to fight this foreign tissue. Certain substances released during this battle suppress the appetite center in the brain. In other words, the patient is biologically in need of energy, while the brain gives the command “do not eat.”

In addition, the metabolic rate remains very high even at rest. It is as if the patient is running a marathon while lying in bed. To find energy, the body first uses the sugar in the blood; when that is depleted, it attacks fat stores, and finally breaks down the skeletal muscles that enable vital organs to function and converts them into energy. This is the complex mechanism behind the patient gradually wasting away, clothes becoming loose, and difficulty even when climbing stairs.

Some warning signs that patients may notice during this process are as follows:

• Persistent fatigue
• Complete loss of appetite
• Muscle weakness
• Night sweats
• Fever
• Clothes becoming loose

What Is the Relationship Between Lung Cancer and Weight Loss?

Unfortunately, lung cancer is one of the diseases most commonly associated with weight loss. More than half of the patients diagnosed with lung cancer who apply to our outpatient clinic have a history of significant weight loss. The lung is the body’s oxygen reservoir. When there is a problem here, the entire system is affected. However, in lung cancer, the tumor consuming energy is not the only cause of weight loss.

At this point, the concept we call “work of breathing” comes into play. A healthy person does not feel that they expend energy while breathing. It is an automatic and effortless action. However, for a patient whose airways are narrowed due to a lung tumor or whose lung capacity has decreased, breathing requires significant physical effort. The neck and back muscles, which we call accessory respiratory muscles, work continuously. Even while the patient is simply sitting in a chair and trying to breathe, they may burn as many calories as a healthy person does while walking. We call this “pulmonary cachexia.”

In addition, depending on the location of the tumor, the patient’s desire to eat may also decrease. For example, tumors in the upper part of the lung may sometimes press on the esophagus or suppress the patient’s appetite due to severe pain. Chronic coughing attacks may also exhaust the patient and make eating difficult.

Symptoms accompanying weight loss in lung cancer that absolutely require medical consultation are as follows:

• Persistent cough
• Bloody sputum
• Shortness of breath
• Chest pain
• Pain radiating to the back
• Hoarseness
• Wheezing

How Does Esophageal Cancer Cause Weight Loss?

In thoracic surgery practice, esophageal cancer is the disease group in which weight loss occurs most dramatically and rapidly. Here, the mechanism is slightly different from lung cancer and much more tangible. The problem is entirely a mechanical obstruction. The esophagus is a flexible tube through which food taken by mouth is delivered to the stomach. A mass growing inside this tube causes the passage to become blocked.

The patient usually notices this condition gradually. At first, complaints begin such as “Food gets stuck in my throat” or “It feels as if food gets stuck in the middle of my chest.” The condition of difficulty swallowing, which we call “dysphagia” in medicine, worsens in parallel with the progression of the disease. Initially, the patient has difficulty swallowing solid foods such as bread and meat and avoids swallowing them without chewing. Over time, soft foods such as rice and pasta also begin to have difficulty passing.

In the advanced stages of the disease, the situation becomes even more severe; the patient becomes unable to swallow soup, milk, or even water. When the passage is completely blocked, food intake drops to zero. A patient in this condition may lose 10-15 kilograms within weeks. The weight loss here is related not only to the metabolic effect of cancer but directly to “starvation.” Since the body cannot receive nutrients, it rapidly consumes its own reserves. Therefore, in patients suspected of having esophageal cancer, we race against time because with each passing day the patient wastes away further and faces the risk of losing the opportunity for surgery.

Difficulty swallowing in esophageal cancer generally progresses in the following order:

• Solid foods
• Semi-solid foods
• Pureed foods
• Liquid foods
• Water
• Saliva

Is Every Weight Loss Cancer? What Is Achalasia?

After discussing such frightening scenarios, I should also mention a fact that may provide some reassurance: Not every chest disease presenting with weight loss is cancer. Sometimes benign diseases may also produce symptoms that mimic cancer. The foremost of these is “Achalasia.”

Achalasia is a disease in which the valve at the lower end of the esophagus, where it joins the stomach, cannot relax. Normally, when we swallow something, this valve opens and the food passes into the stomach. In patients with achalasia, however, this valve remains continuously contracted. Food accumulates in the esophagus and cannot descend into the stomach. The patient feels that the food they have eaten remains in their chest and complains that it comes back into their mouth when they lie down at night. Since food cannot pass into the stomach and be digested, the body is deprived of nutrients and the patient begins to lose weight.

Patients with achalasia usually come saying, “I have been losing weight for years; eating is torture for me.” The difference from cancer is that this process extends over many more years. However, the patient still ultimately faces serious nutritional deficiency, known as malnutrition. For us as thoracic surgeons, achalasia is a disease with highly satisfying outcomes. This is because we can completely correct this mechanical problem by surgically cutting the muscles that form the valve, known as Heller Myotomy.

Typical symptoms of achalasia are as follows:

• Difficulty swallowing
• Regurgitation of undigested food into the mouth
• Pain behind the chest
• Heartburn
• Difficulty burping
• Weight loss

Do Chest Masses Cause Weight Loss?

The area located in the exact center of the chest, between the two lungs, which we call the “mediastinum,” is the crossroads of the body. The heart, major vessels, windpipe, and a gland called the “thymus” are located here. Masses developing in this narrow area may also be among the hidden causes of weight loss.

Mediastinal masses are highly varied; thymoma, lymphoma, teratomas, or cystic structures may occur here. Blood-related malignancies such as lymphoma, in particular, create systemic inflammation in the body. These patients generally come to us with the classic triad we call “B Symptoms.” If these symptoms are present, it means the body’s energy consumption has increased excessively. Masses such as thymoma, on the other hand, may make swallowing difficult by compressing the esophagus from the outside as they grow and may indirectly cause weight loss.

The “B Symptoms” seen in mediastinal masses are as follows:

• Unexplained fever
• Severe night sweats
• Significant weight loss

Which Methods Are Used to Diagnose Weight Loss?

In a patient presenting with weight loss, our priority as thoracic surgeons is “to determine the location and strength of the enemy.” For this, an X-ray or tomography alone is not sufficient; a tissue diagnosis, namely a biopsy, is required. Fortunately, with today’s technological advances, we can establish a diagnosis without exhausting the patient or making large incisions.

One of the leading methods is EBUS, Endobronchial Ultrasound. This procedure is performed after giving the patient a mild sedative. A thin tube with an ultrasound probe and camera at its tip is inserted into the windpipe. Using sound waves, the lymph nodes behind the windpipe are visualized, and a sample is taken with a needle at the same time. The patient feels no pain and returns home the same day. Especially in patients weakened due to weight loss, it is the safest way to establish a diagnosis without exposing them to the risks of general anesthesia.

Another method is Mediastinoscopy. This procedure is considered the “gold standard” in the staging of lung cancer. Through a very small incision made just below the neck, tissue samples are taken directly from the lymph nodes inside the chest. The importance of this procedure is as follows: If the disease has spread to the lymph nodes, it may be necessary to begin treatment with chemotherapy rather than surgery. Making this distinction is vital to protect the patient from an unnecessary and major operation.

The main methods we use during the diagnostic process are as follows:

• Lung tomography
• PET-CT scan
• Bronchoscopy
• EBUS
• Mediastinoscopy
• Transthoracic needle biopsy

What Is VATS, the Minimally Invasive Surgical Method?

In the past, thoracic surgery operations brought to mind large and painful procedures in which the back was cut from end to end and the ribs were separated with special instruments. It is quite difficult for a patient who has lost weight and whose body resistance has decreased to tolerate such open surgeries. However, the VATS method, Video-Assisted Thoracic Surgery, which entered our lives over the last 30 years, has completely changed the situation.

In the VATS method, we do not open the patient’s chest. We create 1 or 3 small openings, approximately 1-2 centimeters in size, between the ribs. Through these openings, we insert a high-resolution camera and thin surgical instruments. The surgeon performs the operation while watching the internal image on a large screen.

The advantage of this method for patients with weight loss is very significant. Because large muscle incisions are not made, the patient experiences much less pain after surgery. The immune system is less suppressed. Most importantly, the patient gets back on their feet much more quickly, performs breathing exercises more comfortably, and returns to normal nutrition much earlier. Restoring the patient’s appetite and enabling them to begin eating as soon as possible is the most critical factor in regaining the weight they have lost.

The advantages that the VATS method provides to patients are as follows:

• Less postoperative pain
• Shorter hospital stay
• Smaller surgical scar
• Rapid return to daily life
• Less blood loss
• Preservation of the immune system

What Are the Surgical Treatment Options?

We have established the diagnosis and completed the staging. So, how will we remove this disease causing weight loss from the body? At this point, our surgical strategies, which vary according to the type of disease, come into play.

If the problem is lung cancer, the method we most commonly perform is “Lobectomy.” Our lungs consist of sections called lobes, with 3 on the right and 2 on the left. We completely remove the lobe containing the tumor together with the surrounding lymph nodes. This is the most effective method for eliminating the disease at its source. When the tumor is removed from the body, that “energy-consuming parasite” is also gone, and the metabolism gradually returns to normal.

If the problem is esophageal cancer, we perform a much more extensive operation called “Esophagectomy.” We remove the diseased portion of the esophagus. So, how will the patient eat? Here, we use the body’s own tissues. We generally shape the stomach into a tube and pull it upward into the chest cavity or as far as the neck to create a new esophagus. In this way, once the recovery process is complete, the patient is able to eat by mouth again. This operation is a major intervention that directly restores the patient’s quality of life and nutritional pattern.

In patients with achalasia, we perform Heller Myotomy. We cut the tightened muscles at the lower part of the esophagus, generally using a minimally invasive method. When the patient wakes up after surgery and drinks water the next day, they feel the water flowing freely into their stomach, which is an indescribable happiness for them.

The main surgical methods we perform are as follows:

• Lobectomy (Removal of a lung lobe)
• Segmentectomy (Removal of a smaller section)
• Esophagectomy (Removal of the esophagus)
• Gastric Pull-up (Pulling the stomach upward)
• Heller Myotomy (Muscle-relaxing surgery)
• Cyst or mass excision

Why Is Nutrition Important Before Surgery?

Immediately placing a patient presenting with weight loss on the operating table may sometimes be the biggest mistake that can be made. It is like setting out on a journey when the car has no fuel. If the body’s protein stores are depleted, even the most perfect operation we perform may fail. This is because the body needs protein and energy for surgical sutures to heal, wounds to close, and infections to be fought:

For this reason, we apply a preparation period called “Preoperative Nutrition.” We evaluate the patient’s nutritional status with special tests. If the patient is at risk, we place them in a kind of intensive preparation program for 7-10 days before surgery. In addition to the foods they normally eat, we begin special medical nutritional products enriched with protein and calories.

These products are not ordinary foods; they contain “immunonutrition” components that strengthen the immune system. Substances such as omega-3 fatty acids, arginine, and nucleotides prepare the body’s defense cells for battle. This preparation process significantly reduces the risk of postoperative complications. Our aim is not to make the patient gain weight on the scale but to nourish them at the cellular level.

The contents we focus on in nutritional support are as follows:

• High-quality protein
• Omega-3 fatty acids
• Arginine
• Vitamin and mineral complexes
• High-calorie formulas

Do Infections Cause Weight Loss?

Finally, it is necessary to mention infections that fall within the field of thoracic surgery. Tuberculosis has been known as the “wasting disease” since ancient times because it gradually consumes the patient. Today, we still encounter tuberculosis and nontuberculous mycobacterial infections.

When these microbes settle in the lungs, the body expends a tremendous amount of energy to contain them. This state of chronic battle causes severe loss of appetite, night sweats, and weight loss in the patient. Long-term medication therapy is generally applied. However, sometimes the medications are insufficient, and permanent damage, cavities, or abscesses develop in the lung. This is where surgery comes into play. Removing the part of the lung that has become a focus of infection and no longer functions relieves the burden on the body. Once the source of infection is cleared, the body uses its energy not to fight but to repair itself, and the patient begins to gain weight rapidly.

Situations in which these types of infections require surgery are as follows:

• Cases resistant to drug treatment
• Recurrent bloody sputum (hemoptysis)
• Lung abscess
• Bronchiectasis (Permanent widening of the airways)
• Destroyed lung tissue

Frequently Asked Questions