Can cancer cause weight gain?

Can Cancer Cause Weight Gain?

Yes, certain cancers can cause weight gain, and weight gain is common after cancer diagnosis and treatment, particularly in breast cancer survivors where gains range from 1-5 kg.1, 2

Types of Cancer-Related Weight Gain

Cancer can contribute to weight gain through several mechanisms:

1. Direct Cancer Effects

• Ascites: Cancer that metastasizes to the peritoneum can lead to fluid accumulation (malignant ascites) due to increased vascular and lymphatic permeability 1
• Liver or lymphatic metastasis: Can cause increased pressure, hampering fluid return from the abdomen to the heart 1

2. Treatment-Related Weight Gain

• Breast cancer treatment: Weight gain is particularly common, affecting the majority of women undergoing treatment 2
• Adjuvant therapy: In women with breast cancer, weight gain is often associated with adjuvant therapy 1
• Chemotherapy: Higher dose, longer duration, and multi-agent regimens are associated with greater weight gain 3

3. Body Composition Changes

• Fat mass increase with lean mass decrease: Cancer treatment can lead to changes in body composition even when overall weight gain is modest 2
• Metabolic changes: Treatment may alter metabolism, contributing to weight gain despite stable or decreased caloric intake 2

Risk Factors for Cancer-Related Weight Gain

Several factors increase the likelihood of weight gain after cancer diagnosis:

• Age: Younger patients (18-54 years) are more likely to gain weight 4
• Pre-diagnosis BMI: Non-obese patients at diagnosis are more likely to gain weight than those who were obese 4
• Menopausal status: Premenopausal women experience greater weight gain 3
• Treatment type: Certain treatments, including some chemotherapy regimens, are associated with more weight gain 3
• Time since diagnosis: Longer time (>36 months) since diagnosis is associated with weight gain 5
• Diet quality: Lower diet quality is correlated with greater weight gain 5

Clinical Implications

Weight gain after cancer diagnosis has significant implications:

• Recurrence risk: Weight gain during therapy may increase the risk of cancer recurrence 3
• Mortality risk: Obesity (BMI ≥30 kg/m²) is associated with higher risk of total and cancer-specific mortality, particularly in breast cancer 1
• Quality of life: Weight gain has a profoundly negative impact on quality of life in cancer patients 3
• Comorbidities: Increases risk for cardiovascular disease and diabetes 1

Management Recommendations

For patients experiencing cancer-related weight gain:

1. Regular BMI monitoring: Evaluate BMI at regular intervals; maintain 18.5-24.9 kg/m² when possible 1

2. Dietary interventions:

   • Focus on portion control for overweight/obese survivors 1
   • Consider referral to a registered dietitian, especially one certified in oncology nutrition 1

3. Physical activity:

   • Moderate physical activity during and after treatment helps maintain lean muscle mass while reducing body fat 1
   • Physical activity is associated with reduced cancer-specific and all-cause mortality 1

4. Weight management timing:

   • During treatment: Focus on preventing further weight gain 1
   • After treatment: Safe weight loss through increased physical activity and healthful food choices 1

Important Caveats

• Unintentional weight loss may indicate cancer progression and should be evaluated 1
• Weight management strategies should be approved by treating oncologists and monitored closely 1
• Even modest weight loss (5-10% over 6-12 months) can reduce risk factors associated with disease 1
• The safety and efficacy of weight loss drugs or bariatric surgery in cancer survivors is currently unknown 1

Understanding the relationship between cancer and weight gain is essential for developing appropriate interventions that can improve both quality of life and long-term survival outcomes for cancer patients.