Unexplained weight loss is a drop in body weight without changes to diet or exercise. While this can be concerning, cancer is just one of many potential causes. Understanding this symptom is the first step toward seeking medical advice.
The Biological Reasons for Cancer-Related Weight Loss
Cancer-related weight loss is driven by cachexia, a syndrome causing progressive loss of muscle and fat, fueled by the body’s inflammatory response to a tumor. Unlike weight loss from dieting, cachexia cannot be reversed by eating more, as it involves deep changes in body chemistry.
Tumors release inflammatory proteins called cytokines. These disrupt metabolism, leading to the breakdown of muscle and fat, and also suppress appetite. Cancer cells also demand significant energy, increasing the calories your body burns at rest.
Physical symptoms from a tumor’s location, such as difficulty swallowing or feelings of fullness, can also limit food consumption.
Specific Cancers Commonly Associated with Weight Loss
While many cancers cause weight loss, it is a prominent early sign for certain malignancies. Cancers of the upper gastrointestinal tract, including the pancreas, stomach, and esophagus, are frequently associated with significant weight reduction.
Pancreatic cancer can impair digestive enzyme production, leading to malabsorption. A stomach tumor can create a false sense of fullness, while esophageal cancer can make swallowing painful, both limiting food intake.
Lung cancer is another common example, as it can increase metabolism and suppress appetite. Other cancers, such as ovarian, liver, or colon, may also cause weight loss by disrupting metabolism or nutrient absorption.
Accompanying Signs and Symptoms
Unexplained weight loss from cancer rarely occurs in isolation and is often accompanied by other signs. Recognizing these associated symptoms is important for seeking a medical evaluation. Common accompanying symptoms include:
- Persistent fatigue not relieved by rest.
- Unexplained and persistent pain.
- Changes in bowel or bladder habits.
- A nagging cough or hoarseness.
- Heavy night sweats, fevers, or unusual bleeding.
- Persistent indigestion or difficulty swallowing.
When to Consult a Healthcare Professional
Healthcare professionals consider the unintentional loss of 5% or more of body weight in six to 12 months to be significant. An unexplained loss of 10 pounds or more also warrants a doctor’s visit, especially if accompanied by other symptoms.
It is particularly important for older adults to report such changes. A doctor can conduct an evaluation, which may include blood tests or imaging scans, to investigate potential causes.
Many conditions other than cancer, such as an overactive thyroid or diabetes, can cause weight loss. A professional medical diagnosis is the only way to determine the underlying cause.