Why does cancer cause weight loss?
Cancer usually affects not just the organs but the whole body. The tumor itself can cause altered energy consumption and also lead to deficiencies because certain organs are impaired in their function and can’t work properly.
Due to the location of certain tumors, bottlenecks or passage disturbances may occur for the ingested food. The result may be dysphagia, diarrhea, bloating, early satiety, sometimes nausea and vomiting – all of them affect your nutritional intake in one way or the other.
It can also happen that certain tumor treatments (radio- and/or chemotherapy) or surgeries lead to reduced food intake or impaired nutrient utilization due to side effects.
A dangerous spiral
As a consequence, you may want to eat but are unable to. Don’t underestimate it when the scale shows you getting lighter and lighter. Unintentional weight loss means less treatment tolerance and a painful loss of quality of life.
There is a crucial difference between weight loss in cancer patients and conscious weight loss in a healthy state. It depends less on the total intake of calories and more on altered metabolic features. That’s why you mainly lose muscle mass instead of fat.
In cancer, the reasons for this mismatch are diverse.
5 reasons for weight loss in cancer patients
1. Metabolic changes
Cancer can cause changes in your metabolism. The body responds to the tumor in a similar fashion to a foreign body or a wound, and initiates a defense mechanism, utilizing certain nutritional components differently than when it was healthy. The tumor causes a change in your carbohydrate, fat and protein metabolism. As a result, your body needs more protein and can metabolize more fat. At the same time, cytokines (produced from the tumor itself) reduce hunger and appetite. Due to inflammation, the appetite is also diminished and that’s when your risk of developing cachexia starts.
2. Type of cancer
Your risk of malnutrition depends also on the type of cancer. Patients with upper GI (esophageal, gastric, pancreatic cancer), hematologic, head/neck and lung cancer have the highest risk, whereas hormone-dependent cancers (like breast cancer and prostate cancer) are rarely connected to malnutrition. In addition, the cancer stage also influences your risk of malnutrition. The more advanced the disease is, the higher the risk of developing malnutrition.
3. Tumor treatment
Radiation and chemotherapy or surgery can interfere with food intake. Sense of taste is often altered. Nausea and food intolerances can occur. Many patients also suffer from anorexia that can also be caused by treatment. Learn more about the common side effects of chemotherapy here.
4. Age
Geriatric patients in general have a higher risk of malnutrition, as their food intake often is not adequate because of age-related symptoms like reduced taste. Not only do geriatric patients have a higher risk of malnutrition but also a higher risk of cancer.
Facing the fact that the proportion of people over 60 is growing faster than any other age group, we can understand why the number of cancer patients is growing continuously. So, if you’re a cancer patient over 60 you should be especially attentive to your appetite, weight and other factors mentioned above.
5. Other factors
There are several other reasons for malnutrition in cancer patients, such as:
- Depression
- Preexisting obesity (BMI > 30)
- Smokers/ex-smokers
- Not being able to carry out any work activities at least half of waking hours
A vicious circle
Weight loss can also change the body’s composition. You don’t simply lose fat but, now, also muscle mass to a substantial degree. At the same time, the body often retains more water. These bodily changes aren’t reflected much on the scale. However, if you are affected you might feel weak and no longer feel able-bodied. Quality of life suffers as well as the desire to eat. The body gets increasingly weaker, appetite declines – it’s a vicious circle.
Unless counteracted in time, patients run the risk of finding themselves in a baleful downward spiral: Anorexia accelerates weight loss and this intensifies weakness, which once again intensifies lethargy… Escaping this vicious circle is hard but fundamental to regaining strength.
