Why does cancer cause weight loss

Knowledge: Unintended weight loss is often a symptom of cancer

The wrong diet, too little exercise and being overweight are responsible for around a third of all cancer cases in Germany. But also those who gradually and involuntarily bring too few pounds on the scales can be in danger.

"With some cancers such as colon, kidney or lung tumors, weight loss is one of the first symptoms: When the tumors grow, they deprive the body of so many nutrients that weight loss occurs," explains cancer aid spokeswoman Eva Kalbheim. She therefore recommends using preventive examinations on a regular basis.

Anyone who inadvertently loses weight despite the fact that their living conditions remain the same should consult the doctor directly. "First of all, other unspecific symptoms provide him with important information: the back pain reminds one of the kidneys, the morning cough of the lungs." Blood samples and ultrasound examinations then bring clarity.

But all too often, weight loss is not taken seriously: Who doesn't like to lose a few pounds without following arduous diets? "Every second patient lost significant weight even before the disease was diagnosed, and every sixth patient lost ten percent of his body weight," says Jann Arends, specialist in internal oncology at the Clinic for Tumor Biology in Freiburg. This means that the patient does not lack the love handles that everyone likes to do without, but rather valuable cells that are involved in the metabolism and the functioning of the immune system.

Even if the weight loss is noticed, it is difficult to control. "In the ideal case, the tumor can be completely removed by an operation and thus the weight loss can be stopped," says Kalbheim. Then it's about stabilizing the body and making up for the loss.

But in many cases the course of the disease is accompanied by further weight loss. "On the one hand, many chemotherapeutic agents cause nausea, diarrhea and vomiting," explains Matthias Pirlich, specialist in internal medicine and endocrinology at the Charité University Clinic in Berlin. The body then does not have enough time to recover between two therapy sessions. Each time he is weaker than the previous time.

Overturn old habits

In addition, chemotherapy is often accompanied by acute inflammation of the mucous membrane, for example in the mouth and throat. Depending on the type of tumor, there are also disease-specific problems. "In the case of esophageal or throat tumors, the path that food has to pass is narrowed," says Pirlich. The ingestion of food is therefore extremely painful. Tumors of the pancreas, in turn, are accompanied by loss of appetite. In addition, the tumor forms protein molecules that cause uncontrollable muscle breakdown.