Weight gain is a common concern among women being treated for hormone receptor positive breast cancer. If you notice that your weight is increasing during hormone therapy, it can be frustrating, especially when your eating habits and daily routine have not changed much.
The good news is that weight gain during hormone therapy is not simply a matter of “eating too much” or not exercising enough. Several changes can happen in the body during and after breast cancer treatment that may make maintaining weight more difficult.
How Hormone Therapy Can Affect Weight
Hormone therapy works by reducing the effect of hormones such as oestrogen on breast cancer cells. Depending on the type of breast cancer and treatment plan, medicines may include tamoxifen or aromatase inhibitors such as anastrozole, letrozole or exemestane. Some women may also receive medicines that suppress ovarian function.
These treatments can cause hormonal changes that affect how the body uses and stores energy.
Lower oestrogen levels, particularly in women who experience treatment induced menopause, can change body composition. You may lose some muscle mass while gaining a greater tendency to store fat, especially around the abdomen.
This does not mean that every woman taking hormone therapy will gain weight. Some women maintain their weight, while others may lose weight or notice changes in body shape without a large change on the weighing scale.
Treatment Induced Menopause Can Play a Role
For younger women, hormone therapy may sometimes be combined with ovarian suppression. This can bring on menopause earlier than expected.
Menopause itself is associated with changes in metabolism, muscle mass and fat distribution. Symptoms such as hot flashes, poor sleep and fatigue can also affect your daily activity.
For example, if you are sleeping poorly because of night sweats, you may feel tired during the day and naturally become less active. Persistent fatigue can also make regular exercise feel much harder.
Over time, these small changes can contribute to weight gain.
Changes in Muscle Mass Matter Too
Muscle is metabolically active tissue, which means it uses energy even when you are resting. During cancer treatment, reduced physical activity, hormonal changes and periods of recovery can contribute to loss of muscle mass.
If muscle mass decreases, your body may burn fewer calories than it did before treatment.
This is one reason why simply eating the same amount of food as before may no longer produce the same result.
Strength based exercise, when medically appropriate, can help maintain muscle and support healthy body composition.
Stress and Emotional Eating
A breast cancer diagnosis and treatment can be emotionally demanding. It is completely understandable if food becomes a source of comfort during difficult periods.
Stress, anxiety and changes in routine can lead some women to snack more often or choose foods that are higher in calories. Others may become less active because they are dealing with fatigue, treatment side effects or concerns about leaving home.
These are not failures of willpower. They are understandable responses to a challenging period.
Recognising these changes without blaming yourself is an important first step.
Steroids and Other Treatment Related Factors
Some women receive steroids or other medicines as part of their cancer treatment. These medicines can increase appetite and cause temporary fluid retention.
It is also important to remember that an increase on the weighing scale does not always represent an increase in body fat. Fluid retention, constipation and changes in muscle mass can all affect your weight.
If you notice a sudden or unexplained increase in weight, discuss it with your doctor rather than assuming it is simply due to hormone therapy.
What Can You Do?
The goal should not be rapid weight loss. During breast cancer treatment, maintaining adequate nutrition and strength is important.
Focus on practical habits such as:
1. Eating regular, balanced meals with adequate protein
2. Including vegetables, fruits, whole grains and other fibre rich foods
3. Limiting highly processed foods and sugary drinks
4. Staying physically active according to your doctor's advice
5. Including strength exercises when appropriate
6. Getting enough sleep
7. Managing stress in ways that work for you
8. Tracking changes in weight and waist measurement rather than focusing only on the weighing scale
A dietitian or cancer nutrition specialist can also help you create a plan based on your treatment, nutritional needs and lifestyle.
Dr. Pragati Singhal
