Can chemotherapy lead to weight gain?

Chemotherapy and Weight Gain in Cancer Patients

Yes, chemotherapy commonly leads to weight gain, particularly in breast cancer patients, with increases typically ranging from 1-5 kg during treatment due to metabolic changes, decreased physical activity, and medication effects.

Mechanisms of Chemotherapy-Related Weight Gain

Chemotherapy can cause weight gain through several mechanisms:

1. Metabolic Changes:

   • Reduced resting energy expenditure (REE) during and after chemotherapy (approximately 3% decline) 1
   • Failure of patients to reduce caloric intake to match decreased energy requirements 1
   • Altered metabolism due to systemic inflammation 2

2. Body Composition Changes:

   • Increase in fat mass with concurrent loss of lean body mass 2
   • Development of sarcopenic obesity (weight gain with lean tissue loss) 2
   • Increased waist circumference and abdominal fat deposition 2

3. Treatment-Related Factors:

   • Steroid use (particularly dexamethasone) as antiemetics during chemotherapy 3
   • Decreased physical activity due to fatigue (occurs in 96% of patients) 2
   • In breast cancer patients: ovarian failure, increased caloric intake, and decreased basal metabolism 2

Patient Risk Factors

Weight gain is more pronounced in certain patient populations:

• Premenopausal women (85.6% experience weight gain vs. 72.6% in postmenopausal women) 3
• Patients closer to ideal body weight at diagnosis 4
• Younger patients 4
• Patients receiving specific chemotherapy regimens (particularly CMF: cyclophosphamide, methotrexate, 5-fluorouracil) 5
• Patients with hormone receptor-positive breast cancer 2

Clinical Significance

Weight gain during chemotherapy has important clinical implications:

• Increased mortality risk: Women who gain >2 kg/m² have a 64% increased risk of breast cancer death compared to those maintaining stable weight 6
• Poorer prognosis: Obesity at diagnosis and weight gain after diagnosis are associated with increased risks of cancer recurrence 2
• Reduced quality of life 4
• Increased cardiovascular risk factors: Higher rates of hypertension and diabetes in cancer survivors 2

Magnitude and Timing of Weight Gain

• Meta-analysis shows an average weight gain of 2.7 kg (95% CI 2.0-7.5) during chemotherapy 5
• Weight gain is more pronounced in studies published before 2000 (suggesting improvements in modern chemotherapy regimens) 5
• Weight changes are unlikely to reverse after treatment completion 4
• Body composition changes include an average gain of 7.1 kg of body fat with a concurrent loss of 1.7 kg of fat-free mass 1

Management Recommendations

1. Nutritional Counseling:

   • Early and individualized dietary counseling during treatment 2
   • Focus on controlling energy intake while ensuring adequate nutrition 2
   • Ensure adequate protein intake (1.2-1.5 g/kg/day) to prevent sarcopenia 2

2. Physical Activity:

   • At least 150 minutes of moderate-intensity aerobic exercise weekly with resistance training twice weekly 6
   • Exercise during treatment improves cardiorespiratory fitness, physical function, and mitigates treatment toxicities including fatigue 6

3. Monitoring:

   • Track weight at each follow-up visit and address changes >2 kg promptly 6
   • Monitor body composition changes when possible, not just total weight 2

4. Medication Considerations:

   • Use actual body weight for chemotherapy dosing regardless of obesity status 2
   • Consider minimizing steroid doses when possible 3

Clinical Pitfalls to Avoid

• Don't ignore small weight changes: Even modest weight gain can impact long-term outcomes and quality of life 2
• Don't focus only on scale weight: Body composition changes (increased fat, decreased muscle) may occur even without significant weight changes 2
• Don't assume weight gain is inevitable: Modern chemotherapy regimens show less weight gain than older protocols 5
• Don't reduce chemotherapy doses for obese patients: Full weight-based dosing is recommended as there is no evidence of increased toxicity 2
• Don't neglect nutritional assessment: Early intervention can help prevent or minimize weight gain 2

Weight management should be an integral part of cancer care from diagnosis through survivorship to optimize both oncologic outcomes and quality of life.