3 Cancer
Cancer in general can cause weight loss, but there are several types of cancer, such as lung, pancreatic, biliary, and colon that are known to lead to unexplained weight loss. "Abnormally functioning cancer cells grow out of control, speed up your metabolism, and wear out your entire body by using its resources, which causes weight loss," says Michael Russo, MD, general surgeon who specializes in bariatric surgery at MemorialCare Center for Obesity at Orange Coast Memorial Medical Center in Fountain Valley, California. Cancer treatments can also lead to weight loss. Radiation and chemotherapy often cause a decrease in appetite, and it can lead to side effects, including nausea, vomiting, and mouth sores that discourage eating.
