Nearly everyone experiences weight fluctuations throughout their lives. Diet, exercise, pregnancy, hormonal changes, and aging can all affect weight. While fluctuations are generally normal, unexplained weight loss can raise concerns and may be a sign of a serious illness, such as cancer. Weight loss can be a symptom of cancer, a side effect of treatment, or the illness itself.
Losing weight for no clear reason does not automatically mean you have cancer; however, the amount of weight lost matters. Losing a few pounds is usually not serious, but losing 10 pounds or more without explanation can be a warning sign. According to Munveer Bhangoo, MD, a hematologist and oncologist at Scripps Cancer Center and Scripps Clinic, "For many people with cancer, this unexplained weight loss is one of the first indications of the disease."
This article explores the connection between lung cancer and weight loss, delving into the causes, impact, and management strategies.
The Connection Between Lung Cancer and Weight Loss
Lung cancer is a leading cause of cancer deaths in the United States. Studies have shown an association between weight loss and reduced survival in cancer patients. Weight loss is a common concern, with approximately 60% of all people diagnosed with lung cancer reporting weight loss.
A study using an extensive cancer dataset identified 76,086 patients diagnosed with lung cancer between 1998 and 2002. Among these patients, 14,751 presented with obesity and/or weight loss. The median survival time (MST) for all lung cancer patients was 8.7 months. Patients presenting with weight loss (15.8%) had a shorter MST compared to those who did not (6.4 vs. 9.2 months, p<0.001). Weight loss significantly shortened MST for all stages and histological subtypes.
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Weight Loss as a Predictor
Weight loss that begins as far as 2 years before a lung cancer diagnosis may be associated with a risk of cancer. Significant weight loss may be associated with incident lung cancer, according to an analysis of electronic health records (EHR) from University of Washington Medicine (UWM) that was published in JAMA Network Open. Patients in the case-control study who experienced 10% to 50% weight loss had a 2-times higher likelihood of being diagnosed with lung cancer.
Further, 6 months of continued weight loss prior to cancer diagnosis was significantly associated with incident cancer diagnosis. This includes weight loss recorded as a symptom by the clinician or weight loss based on changes seen in routinely measured weight.
Weight loss, loss of appetite, and fatigue are nonspecific symptoms of lung cancer; however, they are also associated with other conditions. To further complicate the issue, weight loss is difficult to assess because it can either be subjectively measured by the patient or objectively measured by a clinician. For example, it is routinely measured in visits to ambulatory care facilities.
Prior studies suggest weight loss can be significantly associated with various cancers; however, there is no clear association between weight loss and incident lung cancer. Investigators conducted a study to collect evidence that weight loss is associated with incident lung cancer.
The study included a large cohort of 625 patients, aged 40 years and older, diagnosed with lung cancer between 2012 and 2019 and part of the US ambulatory care medical system. Investigators enrolled 4606 controls who were matched on age, sex, smoking status, and in a similar type of ambulatory clinic.
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The EHR data suggest that 3 or more months of weight loss prior to lung cancer diagnosis is associated with lung cancer. Further, patients with lung cancer were more likely to have increased weight loss than matched controls in the 2 years prior to diagnosis.
Weight loss ranging between 1% and 10% did not have as much of a risk on lung cancer diagnosis compared to patients who maintained a steady weight. In addition, weight loss recorded by the clinician was a better tool to estimate risk of incident lung cancer than measuring weight change, although clinicians often missed or did not make noteworthy records of objective weight changes.
Limitations include control and study arms being chosen based on different criteria; some cases and controls were excluded during analysis due to clinically implausible data; certain aspects of data collection relied on patient interactions with the health care system; and smoking was not directly included in models.
Why Does Lung Cancer Cause Weight Loss?
Several factors can contribute to weight loss in people with lung cancer.
Increased Calorie Burn
One key factor is the body's increased calorie burn. Cancer cells demand more energy than healthy cells, so the body may burn more calories at rest than normal. Cancer cells also release substances that affect how your body uses calories from food and can lead to weight loss.
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Inflammation
Inflammation is another key factor. When the body fights cancer cells, the immune system releases substances called cytokines that increase inflammation in the body. They can disrupt normal metabolism and interfere with hormones that control appetite. This often leads to less hunger and significant weight loss.
Nausea and Other Symptoms
Nausea, a common side effect of cancer, also plays a role. Patients with nausea may have little or no appetite and may be unable to keep food down. Other factors include the location of the cancer. Cancers in the mouth or throat can make chewing or swallowing difficult. Tumors near the abdomen, like ovarian cancer, can press on the stomach.
Treatment Side Effects
Cancer treatments, such as chemotherapy and radiation therapy, often cause side effects that make it difficult for patients to eat and absorb nutrients. Nausea, vomiting, and loss of appetite are common side effects of these treatments.
Cancer Cachexia
When cancer causes severe weight loss, it is called cancer cachexia. This metabolic condition leads to muscle loss and reduced appetite. According to the American Cancer Society, significant weight loss happens most often with cancers that affect the stomach, pancreas, esophagus, and lungs. Cancer can produce substances that suppress hunger. This can occur in advanced stages of lung cancer, causing a person's body to lose the ability to ingest and use nutrients in food.
Resting Energy Expenditure
People with lung cancer burn more energy at rest as their bodies try to regulate their condition. With the added strain on the body from lung cancer and its treatments, the energy balance shifts negative, and weight is lost. Another factor is cancer’s use of glucose for its own needs, which takes away calories from the rest of the body.
Loss of Appetite (Anorexia)
Loss of appetite, which is clinically known as anorexia, is one of the main factors contributing to malnutrition in a lung cancer diagnosis. This lack of an urge to eat is harder to overcome when people with lung cancer experience eating complications, like difficulty with chewing and swallowing. It’s common for people with lung cancer to fall into a negative feedback loop - they develop fatigue and weakness due to not eating enough, and this exhaustion makes it more difficult to eat.
Hypercalcemia
When lung cancer cells spread (metastasize), they may move to the neighboring bones around the lungs (a process known as bone metastasis). For people with non-small cell lung cancer, this metastasizing may result in hypercalcemia (excess calcium in the bloodstream). As cancer cells begin to affect the bones, the bones may release a large amount of calcium into the bloodstream. This excess in calcium levels may also cause various gastrointestinal issues, like nausea and vomiting, making it difficult to eat.
Impact of Weight Loss on Lung Cancer Patients
An unexpected drop in regular weight can overwhelm people as they deal with lung cancer. With the additional stress of weight loss and an energy imbalance, it’s common for people with lung cancer to experience fatigue. It’s no wonder people may forget to eat or be unable to manage their diets when they are battling pain and exhaustion.
Weight loss among cancer patients has been reported in up to 50% of all cancer patients. Among patients with small cell cancer, weight loss has been noted in nearly 57% of patients; similarly patients with non-small cell cancer have had reported weight loss rates of approximately 54%.
Considering all the different causes of weight loss in cancer, researchers have suggested that one’s body weight can be an indicator of health outcomes and quality of life. Researchers have also found that the effectiveness of radiation and chemotherapies improved when a person was able to maintain a healthy weight.
Managing Weight Loss in Lung Cancer
If you or a loved one has cancer and is losing weight, muscle, or energy, consult with your care team. They can find out what is causing these problems and give advice on how to deal with them. Doctors look at the medical side of weight loss, including treatment side effects and overall health. They can adjust treatments to reduce negative effects. Anti-nausea medications can help relieve nausea and stimulate appetite.
Here are several strategies to manage weight loss during lung cancer treatment:
Consult a Registered Dietitian: Registered dietitians provide individualized nutrition recommendations to help keep weight on while accommodating for personal or cultural food preferences and side effects, such as reduced appetite, nausea, taste changes, and issues chewing or swallowing. A dietitian may urge a person with cancer to eat more of their favorite foods, and the more calories, as tolerated, the better. This isn’t the time to restrict yourself to vegetables and fruits. A dietitian may even recommend dietary supplements to make sure you get the nutrients you need. Don’t start any new treatments, including over-the-counter drugs or natural remedies, without first consulting your health care team. You may want to use calorie additives that could make your meals and snacks more calorie-dense. Milk powder can add calories without affecting the taste of food too much.
Exercise Specialists: Exercise specialists provide personalized recommendations to help prevent muscle loss and boost energy levels.
Behavioral Health Specialists: Behavioral health specialists, such as psychologists and social workers, can help patients cope with stress and other emotional challenges of cancer, which can improve energy and appetite.
Cancer Support Groups: Cancer support groups provide a community of shared experiences. Emotional support is crucial for cancer patients.
Increase Frequency of Meals: Increase how often you eat in a day.
Medications: You may be offered medications to treat severe weight loss.
Home Remedies: There are also some home remedies you may want to try. As a cautionary note, it might be best to consult with your oncologist about the risk factors of smoking cannabis as opposed to alternative methods of consumption, like edibles (foods or beverages containing cannabis extracts) or taking it as a prescription medication. It’s also important to be aware of the laws about marijuana in your state.
Keeping a Lung Cancer Diary: To help you take an active role in your weight management, it may be a good idea to keep a cancer diary to log your day-to-day life with lung cancer. Not only does this allow you to create an artifact of your thoughts and feelings along the way, but it also helps you provide your health care team with data about your weight, appetite, and other symptoms. Write down the date every time you make an entry in the journal. By considering where you are in the cycle of your treatment, your doctors may be able to distinguish weight loss symptoms caused by lung cancer from treatment-related weight loss. If the idea of journaling seems off-putting, you can think about your writing as a narrative that details your journey through battling lung cancer and the resulting weight loss. The form of the diary can be completely up to you. You may prefer to write a daily symptom log, or if you find the inspiration, you can take a more artistic approach.