The weight debate – big fat tamoxifen

Is ‘Dear old tam’ to blame for weight gain in breast cancer patients? Dr Inge Kriel answers this hefty question.

What is tamoxifen?

Tamoxifen, a selective-oestrogen receptor modulator (SERM), is given for a duration of five to 10 years after diagnosis, to prevent breast cancer recurrence in oestrogen-receptor positive breast cancers.

Tamoxifen tales

Many patients are concerned about potential weight gain when starting tamoxifen. They may have chatted to other patients who complained about weight gain since starting it, or have read blog posts or chat threads on the internet around this controversial topic.

Some patients have refused to take tamoxifen for fear of gaining weight, and many have defaulted treatment as a result of weight gain that they have attributed to tamoxifen.

This leads to poor compliance and subsequent increased risk of breast cancer recurrence and increased mortality for early oestrogen-receptor positive breast cancers.

Scientific evidence

To date, no studies have shown a conclusive link between tamoxifen and weight gain.

Age at diagnosis correlates with weight gain, and weight gain in the ageing population is similar in breast cancer patients versus non-breast cancer patients.

How does this help you?

So, how does the breast cancer survivor shed those extra kilograms? Firstly, it’s imperative to stay on tamoxifen. ‘Dear old tam’ is not to blame here!

Secondly, it’s important to exclude other medical conditions that may be associated with weight gain, including underactive thyroid (hypothyroidism), or insulin resistance/Type 2 diabetes.

If you’re struggling to lose weight despite a well-balanced, sensible eating plan and rigorous exercise routine, your doctor may send you for blood tests to exclude the above conditions. Appropriate management of these conditions (together with diet and exercise) will facilitate weight loss in resistant cases.

Other factors that may contribute to weight gain in breast cancer patients include:
  • Decreased mobility due to poorly managed post-operative pain and muscular stiffness/scar tissue.
  • Peripheral neuropathy (pins and needles in the hands and feet) after paclitaxel/docetaxel chemotherapy. This can lead to impaired balance and pain, and depending on the severity of the symptoms may hamper ability to exercise.
  • Corticosteroid therapy during treatment.
  • Poor patient education around when it’s safe to commence an exercise programme after surgery, with subsequent unnecessary delay.
  • Complicated post-operative course  with prolonged hospital stay.
  • Overwhelming fatigue with inability to start an exercise programme.
  • Depression – associated with a lack of motivation and over-indulgence (comfort eating).
  • Pre-existing poor eating habits.

Talk to your oncology care physician if any of the above situations apply to you.  He/she will be able to assist in managing the underlying cause for your weight gain. That being said, how does one successfully shed the extra weight?

Follow a sensible eating plan:  
  • This means no fad diets, no extreme calorie-restricted diets or quick-fixes. Sustained weight loss requires adopting a healthy lifestyle. Adequate intake of high-quality lean protein and fresh fruits and vegetables is recommended. Limit consumption of processed food, refined carbohydrates, alcohol, and energy-dense carbonated beverages.
  • Remember to drink at least eight glasses of water a day.
  • Be kind to yourself. You are only human after all. You may make the occasional slip-up but the odd chocolate won’t ruin your diet.
  • One size does not fit all! Every individual is unique and what might work for one person might not work for someone else.
  • American Society of Clinical Oncology (ASCO) guidelines recommend at least 30 minutes of exercise five times per week, including at least two days of impact training for bone health.
  • Exercise has been shown to decrease risk of breast cancer recurrence.
Practice mindfulness
  • Be aware of whatever you choose to eat.
  • Ask yourself how hungry you are before you tuck into a big meal.
  • Teach yourself to recognise when you are full, to stop yourself from over-eating.
Professional help
  • A registered dietitian may help if you’re struggling to follow a sensible eating plan. He/she can assist with an eating plan tailored to your needs and lifestyle, and weekly weigh-ins will keep you motivated to continue losing weight.
  • Sophrology can assist in addressing emotional or psychological reasons for over-eating.
Dr Inge Kriel is an oncology care physician practicing at Netcare Milpark Hospital.


Dr Inge Kriel is an oncology care physician practicing at Netcare Milpark Hospital.