Cancer Diseases and Conditions

Why Does Cancer Cause Weight Loss?


People with Cancer usually experience progressive and profound weight loss caused by loss of both, muscle mass and body fat. The weight loss is usually accompanied by anemia, reduced appetite, and extreme weakness.

Understanding Cancer Cachexia

Cancer cachexia is a syndrome that makes the body waste away. The syndrome is most common during advanced cancer stages although one of the most common cancer symptoms during the early stages is unexplained weight loss. Cancer usually causes the body to lose over 5% of the body weight in a very short time.

Cancer cachexia affects 50% to 85% of all cancer sufferers. They syndrome is however common is some cancers only like lung, bowel and pancreatic cancer. Cancer cachexia compromises the quality of life a sufferer lives. It also makes cancer treatments hard to tolerate. In fact, the syndrome is responsible for causing death in 25% to 33% of all cancer patients. Extreme weight loss is linked to poorer prognosis.

Causes of Cancer Cachexia

The precise cause of Cachexia (a cancer-induced wasting syndrome) isn’t fully understood. Although cancer cells consume a lot of energy when they are constantly replicating, a human fetus grows faster and consumes more energy than cancer cells, but pregnant women don’t waste away. Small tumors can also cause cachexia. We can, therefore, conclude that the energy consumed by cancer isn’t nearly responsible for causing rapid weight loss.

But cancer is known to suppress appetite by causing changes in the regions of the brain responsible for controlling appetite. Cancer also causes changes in taste. However, studies have proven that reduced appetite alone can’t explain the weight loss experienced by cancer sufferers. Furthermore, not everyone with cachexia has a poor appetite.

What’s more important is the effect of cancer on metabolism. Cancer is known to increase metabolism significantly. Individuals who have cancer have heightened energy consumption. Cancer promotes the breakdown of fat and muscle to cater for increasing energy needs. This fat and muscle breakdown is significantly different to that experienced during deliberate starvation or weight loss.

In the recent past, scientists have worked on many mechanisms known to cause cancer-related fat loss and muscle wasting. Current research indicates that many factors are involved. For instance, studies have shown that cancer cells produce substances which promote weight loss. MIC-1 is an example of one such substance discovered recently by scientists. MIC-1 is protein present in the blood of healthy individuals (non-cancerous people). According to research studies, cancer cells promote the generation of abnormal quantities of MIC-1. The levels of the protein increase by 10 to 100 times the normal levels and there are studies linking MIC-1 to weight loss by suppressing appetite.

Cancer cells have also been found to produce substances which “tell” the body to break down fat and muscle. A perfect example of such a substance is PIF. Cytokines are also produced in the process as the body responds to cancer. They plunge the body’s defense mechanisms into overdrive. Cytokines have a multiplier effect on hormones. They also increase the body’s metabolism rate drastically accelerating the pace at which the body breaks down fat and muscle.

Cytokines have been discovered to have a specific effect that is of much interest, i.e., converting white adipose tissue (white fat) into brown fat (fat found in babies). Brown fat is responsible for keeping babies warm. The fat is packed with mitochondria which burn energy to produce heat. The reason why cytokines convert white adipose tissue into brown fat remains unknown. However, it is common among cancer patients and is responsible for increasing the body’s energy needs.

It appears many substances are contributing to cancer-related weight loss, and the scientific research is still in the formative stages. We are still discovering the substances behind rapid weight loss among cancer patients and how these substances cause Cachexia.

External factors

Although weight loss can be linked directly to cancer or the immune system’s response to cancer, the weight loss can also be caused by external factors. Poor appetite can cause nausea, vomiting, pain, changes in taste, as well as mouth sores from chemotherapy or radiation therapy and all this, can cause weight loss directly and indirectly.

Although cancer treatments like radiation therapy and chemotherapy destroy cancer cells, they cause extensive damage to body organs like the skin, blood, and intestines. The body consumes a lot of energy when repairing this damage. Cancers affecting the intestines and stomach are also known to reduce the body’s ability to absorb nutrients found in food. Side effects of cancer/cancer treatments like vomiting and diarrhea can also cause extensive loss of nutrients. Cancer symptoms like fatigue can also reduce activity which can, in turn, causes muscle wasting.

Wasting away is a severe side effect. Currently, cachexia can’t be treated or prevented. Furthermore, the cancer side effect can’t be counteracted effectively using nutrition. Countless studies are trying to understand why Cachexia occurs.

There is hope that scientists will be in a position to target precise mechanisms that cause the wasting syndrome in an effort to prevent cancer-induced weight loss.

In the meantime, it is advisable to eat foods rich in nutrients if you are suffering from cancer-related weight loss. Numerous studies have shown promising results when cancer treatment is focused on nutrition alongside treatments like chemotherapy and radiation therapy.

Although cancer suppresses appetite so you may not have the urge to eat when you have cancer, rapid weight loss is a testament that the body isn’t getting enough energy. You will be required to eat well to control the weight loss. Your body needs to be strong and well nourished for you to cope with cancer therapies. It is also advisable to do strength training to maintain your muscle mass. Since cancer attacks the muscles and breaks them down, you need to train consistently to rebuild lost muscle mass. Strength training should be part of your treatment as opposed to being a passive task done when you feel like. Last but not least, you need to ask your doctor about other therapies or medication that can help you recover.