Medically reviewed by Jeffrey A. Meyerhardt, MD, MPH
Everyone’s weight fluctuates over the course of life, rising or falling with changes in diet and exercise, and with the normal slowing of metabolism that occurs as we age. When weight loss occurs for no apparent reason – especially if the drop is dramatic – a variety of physical or psychological causes could be responsible. These can include diabetes, depression, celiac disease, an under- or overactive thyroid gland, peptic ulcer, colitis, cancer, or other condition. When a loss of 10 pounds or more occurs without changes in diet or physical activity, it’s important for people to see their doctor for an exam.
For many cancer patients, unexplained weight loss may be the first noticeable sign of the disease – estimates place the number at 40 percent of patients. This happens most often with cancers of the pancreas, stomach, esophagus, or lung, according to the American Cancer Society.
Weight loss associated with cancer can derive from a range of factors. Depending on the type of cancer and the organs affected, individuals may experience nausea or a lack of appetite, or have difficulty chewing or swallowing, which causes their food intake to drop. Cancer cells also use a disproportionate amount of the body’s energy supply and often release substances that alter the way the body processes food energy. These changes, too, can result in weight loss.
While most weight loss is not a sign of cancer, it’s prudent for people experiencing unexpected weight loss to see their doctor to determine the cause.