Multiple myeloma (MM) is a cancer originating in the plasma cells, a type of white blood cell found in the bone marrow, where these abnormal cells multiply uncontrollably. Unintended weight loss is a frequent and serious complication associated with the disease itself and its treatment. Losing weight without trying can be one of the initial signs that prompts medical evaluation. Unexplained weight loss is an indicator of underlying physiological stress that requires attention and is an important part of overall cancer care.
The Primary Causes of Unintended Weight Loss
The most significant physiological driver of weight loss in multiple myeloma is cancer-related cachexia, a wasting syndrome characterized by the loss of skeletal muscle mass, with or without fat loss. Cachexia is a metabolic state that cannot be fully reversed by simply increasing calorie intake through conventional nutritional support. The presence of the tumor burden initiates a state of systemic inflammation throughout the body.
This inflammatory response is mediated by the release of pro-inflammatory signaling proteins called cytokines, such as Tumor Necrosis Factor-alpha (TNF-α) and Interleukin-6 (IL-6). These cytokines disrupt the body’s normal metabolism, causing it to break down muscle protein and fat stores at an accelerated rate. This metabolic shift results in a persistent state of negative energy balance, where the body expends more energy than it takes in. MM cells themselves have high metabolic demands, which further increase the body’s overall energy expenditure.
The rapidly dividing cancer cells consume significant energy, effectively diverting nutrients away from healthy tissues. Furthermore, the disease can cause symptoms that directly suppress appetite, such as generalized fatigue and early satiety. Early satiety means a person feels full after eating only a small amount of food.
Another factor is hypercalcemia, which is an elevated level of calcium in the blood caused by the cancer-driven breakdown of bone cells. High calcium levels can cause a loss of appetite, nausea, and vomiting, all of which contribute to reduced caloric intake and subsequent weight loss.
Treatment-Related Nutritional Challenges
The therapies used to control multiple myeloma, while effective against the cancer, can introduce or worsen nutritional challenges that exacerbate weight loss. Chemotherapy and novel therapeutic agents commonly cause side effects that interfere with a person’s desire or ability to eat adequately. Nausea and vomiting are frequent complaints that lead to food aversion and a substantial reduction in daily caloric intake.
Many treatments also cause taste changes (dysgeusia) or a loss of taste entirely. This often results in a metallic or unpleasant taste in the mouth, making previously enjoyable foods unappealing and further decreasing appetite. Inflammation of the mucous membranes lining the digestive tract, known as mucositis, can cause painful sores in the mouth and throat, making chewing and swallowing difficult.
Corticosteroids, such as dexamethasone, are a standard component of many MM treatment regimens. While they can initially increase appetite and may lead to some weight gain, this is often temporary and can involve fluid retention. Over time, high-dose or prolonged corticosteroid use can contribute to the loss of lean muscle mass. This loss negatively impacts overall strength and body composition.
Strategies for Maintaining Healthy Weight
Managing nutritional health requires a proactive and personalized approach, ideally involving a registered oncology dietitian who can tailor advice to specific treatment side effects. Patients should focus on maximizing the nutritional density of their food intake without increasing the meal volume, which can be challenging with a poor appetite. This involves incorporating healthy fats and proteins into meals.
A practical strategy to counteract poor appetite is to eat small, frequent meals throughout the day, rather than attempting three large ones. Aiming for five to six smaller “mini-meals” can make it easier to consume adequate calories and protein. This approach may also help minimize treatment-related nausea. Timing meals around periods of least nausea, which is often in the morning, can also help maximize intake.
Maintaining excellent hydration is also important, as sufficient fluid intake can help manage side effects like constipation and kidney strain, which are common in MM. Individuals should prioritize drinking water, broths, and nutritional supplements. Regularly monitoring weight is an effective tool for tracking nutritional status, and any unintended or rapid weight change should be communicated promptly to the medical team.