Weight Gain With Multiple Myeloma Treatment: What’s Typical and How to Manage It

Weight change during multiple myeloma treatment can happen, and weight gain is possible, mainly due to corticosteroids (like dexamethasone or prednisone), fluid retention, reduced activity, and changes in appetite. ^[1] Weight changes during cancer therapy vary some people gain weight and others lose weight so experiences can differ based on the drugs used, side effects, and personal factors. ^[2]

Why Weight Gain Can Occur

• Corticosteroids (dexamethasone/prednisone): These medicines are commonly paired with myeloma regimens and can increase appetite, cause fluid retention (“puffiness,” swelling), and shift body fat distribution. ^[1] Dexamethasone and similar steroids are known to cause appetite changes and swelling/weight gain in some users. ^[3]
• Infusion‑related steroid premedication: With therapies such as subcutaneous daratumumab, steroids are routinely given before and sometimes after early doses to prevent reactions, which can contribute to short‑term weight gain; after several doses, additional steroids may be reduced if no major reactions occur. ^[1]
• Fluid retention from certain chemotherapies: Some regimens that require steroid premedication in oncology have documented fluid retention and measurable weight increases in clinical settings. ^[4]
• Lower activity and diet shifts: Fatigue and nausea can lead to less movement and higher intake of easy carbohydrates or sugary drinks, which may add calories and promote weight gain. ^[2]

When Weight Gain Needs Medical Attention

• Rapid weight increase or swelling: A quick uptick in weight with leg/ankle swelling, shortness of breath, or decreasing urination may signal fluid retention that needs prompt assessment. [PM13]
• New or worsening edema: If swelling becomes uncomfortable or persistent, your team may adjust medications or recommend diuretics or other measures. [PM13]

Practical Ways to Manage Weight Gain

Nutrition Steps

• Balanced plate and portions: Aim for a balanced diet and mindful portion sizes to avoid excess calories during treatment. ^[5]
• Limit sugary drinks and refined carbs: These are common contributors to treatment‑related weight gain, especially when used to manage nausea; focus on water, unsweetened beverages, and high‑fiber carbs. ^[2]
• Plan meals and snacks: Putting food on a plate, pre‑portioning snacks, and keeping high‑protein, lower‑sugar options handy can reduce overeating. ^[5]
• Work with a dietitian: A clinical dietitian can tailor strategies around your side effects, appetite, and treatment plan. ^[5]

Physical Activity

• Regular movement: Gentle, regular exercise helps burn calories, maintains muscle, and supports digestion and mood; even short walks or light resistance exercises can be helpful. ^[6]
• Adjust for fatigue: On low‑energy days, brief activity sessions spread throughout the day can still support weight control. ^[2]

Medication and Care Plan Adjustments

• Steroid review: If weight gain is substantial or hard to manage, your clinician may consider tapering or simplifying steroid premedication when safe, especially after the first few doses of agents like daratumumab. ^[1]
• Manage fluid retention: If fluid buildup is suspected, your team may check labs, adjust drugs, or use diuretics to control swelling and related weight changes. [PM13]

What to Track and Share With Your Care Team

• Weekly weight and symptoms: Note gains of more than 1–2 kg in a short period, new swelling, or breathlessness and share these promptly. [PM13]
• Diet and activity logs: Brief notes on eating patterns and movement can help your team fine‑tune advice. ^[5]
• Side effects impacting lifestyle: Fatigue, nausea, or taste changes can drive overeating or inactivity; treating these can indirectly stabilize weight. ^[2]

The Bottom Line

Weight gain can happen during multiple myeloma treatment, most often linked to steroid use, fluid retention, and lifestyle shifts during therapy, although not everyone will experience it. ^[1] Practical steps balanced nutrition, regular gentle activity, and medication adjustments when appropriate usually help keep weight within a healthy range. ^{[5] [6]} If weight rises quickly or swelling appears, a timely medical review is important to rule out fluid retention and other complications. [PM13]