Weight loss is a frequent experience for individuals diagnosed with cancer. The changes in body weight and composition that occur are a complex aspect of the disease and its treatment. This process involves shifts in the body’s metabolism and the direct impact of medical interventions. Understanding the nuances of this process is part of navigating the broader cancer experience.
Why Cancer Treatment Causes Weight Loss
The reasons for weight loss during cancer are multifaceted, stemming from the disease and its therapies. One of the primary drivers is cancer cachexia, a metabolic syndrome characterized by the involuntary loss of skeletal muscle and fat. This occurs because some tumors release chemicals called cytokines, which trigger a systemic inflammatory response. This inflammation speeds up the body’s metabolism, causing it to burn calories at a faster rate, even at rest.
Beyond the metabolic effects of the cancer, the treatments used to combat the disease contribute to weight loss. Chemotherapy, radiation therapy, and surgery can all cause side effects that interfere with a person’s ability to eat and absorb nutrients. Common issues include nausea, vomiting, painful mouth sores, and difficulty swallowing, which make the physical act of eating a challenge.
These physical challenges are often compounded by changes in sensory perception. Chemotherapy can alter the sense of taste and smell, making food unappealing. Treatments can also cause constipation or diarrhea, disrupting normal digestion and nutrient absorption. The emotional and psychological toll of a cancer diagnosis, including anxiety and depression, can also suppress appetite.
Understanding Body Composition Changes
The number on a scale provides only a partial view of the weight changes occurring during cancer treatment. The type of weight being lost is a more informative measure of a patient’s health and ability to tolerate therapy. The total weight lost is a combination of fat mass and lean body mass, which is primarily composed of muscle. While some fat loss is expected, the accelerated loss of muscle mass, a condition known as sarcopenia, is a more serious concern.
Sarcopenia is the progressive loss of skeletal muscle mass and function, and it is associated with increased physical frailty and fatigue. Muscle tissue is a reservoir of proteins that the body draws upon to heal and support immune function, particularly when under the stress of cancer treatment. Losing too much muscle can impair the body’s ability to recover from surgery and can increase the toxicity of chemotherapy.
In some cases, the body’s composition can change in ways that are not immediately obvious from overall weight. Certain treatments can lead to a simultaneous loss of muscle and gain of fat tissue, a condition termed sarcopenic obesity. A person experiencing this may see their weight remain stable or even increase, masking the significant loss of functional muscle. This highlights why focusing on preserving muscle is a specific goal during cancer care.
Nutritional Strategies During Treatment
During active cancer treatment, nutritional goals shift toward a focus on calorie and protein density. The primary objective is to provide the body with enough fuel to maintain weight, preserve muscle, and manage the side effects of therapy. Eating smaller, more frequent meals and snacks throughout the day is often more manageable and can help counter a poor appetite or feelings of fullness.
Choosing foods that are high in both calories and protein is an efficient way to get the most out of every bite. This can involve enriching foods with additives like butter, cheese, or cream. Full-fat dairy products, nut butters, and eggs are excellent sources of both protein and calories. When solid food is unappealing, nutrient-dense liquids such as smoothies or commercial nutritional supplements can provide sustenance in an easier-to-consume format.
Dietary adjustments can also manage specific treatment side effects. If a metallic taste is a problem, using plastic utensils and adding tart flavors like lemon can help. For nausea, bland and dry foods like crackers and toast are often better tolerated. For a sore mouth or throat, soft, moist foods served at a cool or lukewarm temperature, such as oatmeal and soups, are less likely to cause irritation.
Post-Treatment Weight and Nutrition
After cancer treatment concludes, nutritional goals evolve toward long-term recovery and health. For those who lost significant weight, the focus becomes rebuilding the body, particularly the muscle mass that may have been depleted. This is best achieved through a diet rich in high-quality protein from sources like lean meats, poultry, fish, and beans, paired with light physical activity as cleared by a doctor.
The post-treatment phase is also a time to reintroduce nutritious foods that may have been difficult to eat during therapy. A balanced diet centered on vegetables, fruits, and whole grains can help replenish vitamin and mineral stores. For healthy weight regain, incorporating healthy fats from sources like avocado, nuts, and olive oil can provide the necessary calories. The appetite should slowly improve, but it is important to be patient as the body recovers.
Conversely, some cancer survivors face the challenge of unwanted weight gain. Certain treatments, particularly steroid medications and hormone therapies, can increase appetite and alter metabolism. For these individuals, the focus shifts to creating a sustainable, healthy lifestyle. This involves choosing a diet rich in plant-based foods, managing portion sizes, and engaging in regular physical activity to achieve and maintain a healthy weight.