How To Beat Weight Gain On Tamoxifen (A Success Story!)

If you are taking tamoxifen, you have A LOT of questions. And when it comes to weight loss, these two probably rank near the top:

  1. Will I gain weight on tamoxifen? And,

  2. If I do, is there anything I can do to stop it—and actually lose weight?

Both of these are valid questions. You've heard so many women talk about how they put on weight while on tamoxifen.

Kathy, a MyBodyTutor success story, said, "My oncologist told me he'd never seen any women on tamoxifen lose weight." 

Luckily, that wasn't the case. She has a happy and powerful story!

(Keeping reading, we'll pick Kathy's story back up soon.)

Is weight gain something you're struggling with now?

If so, we're going to talk about how you can challenge your beliefs and assumptions and beat this extra weight.

But first, let's start with:

What is Tamoxifen?

Tamoxifen is a medication prescribed for breast cancer treatment. And, as a preventative measure for women at high risk of developing breast cancer.

It works by attaching to estrogen receptors and blocking the effects of estrogen on the breast tissue. So it helps prevent the growth of breast tumors that need estrogen; which, according to the National Cancer Institute, is about 80%.

The benefits of tamoxifen are tremendous, but it's not without risk of side effects.

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Is Weight Gain A Side Effect?

A major concern among women on tamoxifen is if they will gain weight. And whether we’re talking about tamoxifen (or a countless number of other medications), weight gain is possible.

Here are just a few potential side effects from Breastcancer.org:

  • Hot flashes

  • Blood clots

  • Mood swings

  • Depression, and

  • Weight gain

The Cleveland Clinic also details weight gain as a possible side effect.

So the risk of gaining weight is very real.

But how common is it?

To answer that, we’ll dive into the research. And, the study we're going to look at is one of the most comprehensive out there.

This women's healthy eating and living (WHEL) study spanned a six-year period and included more than 3,000 breast cancer survivors—ranging in age from 27 to 74.

Among the study’s goals, one was to determine if tamoxifen had an effect on weight change after a breast cancer diagnosis.

The study had two key conclusions:

  1. That there was no link between weight gain and tamoxifen.

  2. However, chemotherapy is significantly associated with weight gain.

So, to answer the question: Should I worry about gaining weight on tamoxifen?

The answer is:

Weight gain is a potential side effect of tamoxifen. However, most studies suggest there is no direct link.


An unfortunate fact remains. Many women will gain weight after diagnosis.

In fact, according to an article published in the World Journal of Clinical Oncology, you can expect to gain anywhere from 2 to 11 pounds.

Right now, you may be asking...

If there is no link between tamoxifen and weight gain, why am I gaining weight?

And the answer is...there is no single aspect we can put our finger on. It is a combination of many, many reasons.

1.) Chemotherapy

In the WHEL study we looked at earlier, we learned that chemotherapy has a significant association with weight gain. But there are other reasons to consider as well.

2.) Emotional Stress

Beyond the initial shock of a cancer diagnosis, there is the inevitable stress, anxiety, and worry that go with that kind of life-changing news.

  • How will I take care of my family during treatment?

  • What will I do about my job?

  • How will I pay for all this?

  • What happens if cancer returns?

Your life just got turned upside down, and there are a million worries you have today that you didn’t have yesterday. Emotional stress can play a huge role in contributing to weight gain.

3.) Metabolism

Your metabolism (the rate at which you burn calories) slows as you age. So naturally, losing weight becomes much more difficult than it once was. Luckily, there are ways, like exercise, that can help you battle a slowing metabolism.

Which brings us to the next factor...

4.) A Lack Of Physical Activity

Studies show that physical activity will decline after a breast cancer diagnosis, which is completely natural. You are recovering from surgery or chemotherapy.

However, less activity means fewer calories burned, which can easily translate into increased weight.

If we consider the magnitude of the situation, combining:

  • A cancer diagnosis,

  • An intensely emotional situation (worry, anxiety, and fear),

  • A lack of physical activity, and

  • The treatment itself.

It is entirely understandable why one would gain weight.

But, what can we do about it?

How To Beat Weight Gain Following A Breast Cancer Diagnosis.

Make no mistake, losing weight is a challenge even under normal circumstances. And it can be even harder after breast cancer.

But it is possible, and you CAN do it.

And where we need to start is with challenging our assumptions.

1.) Challenge Your Assumptions

When you hear you will gain weight after a diagnosis and not many women will ever lose weight enough times, that belief starts to solidify.

Remember when I mentioned earlier that Kathy said, "My oncologist told me he'd never seen any women on tamoxifen lose weight."

It's easy to start believing that is true, especially when you keep trying to lose weight without seeing any results.

We have got to expect a different result. Kathy didn't believe she could lose weight...


So, if you’re thinking, “There is no way I am going to lose this weight!”

I ask, what emotion does that thought trigger?

...Is it anger?

And if you feel hopeless, what action will you most likely take? You guessed it...you probably won’t take action.

So now I ask, How can you challenge this belief? How can you trigger a new emotion?

Maybe it's thinking like this:

Losing this weight is a challenge, but I will succeed DESPITE this diagnosis. Not only for my family but for myself and for others. I will be an inspiration for other women in my situation.

These thoughts trigger feelings of hope and determination, right?

And when you are determined, like I know you are and like Kathy is, you will take action. And actions lead to results.

2.) Describe Your Why

The reason “why” you want to lose weight is the fire that fuels your motivation.

Weight loss after a diagnosis can be a long road with many bumps and discouragements along the way. And that's why it is absolutely critical to describe why you want to lose weight, so you can turn to it when times get tough.

What is your why?

  • Are you doing this to regain control?

  • To improve your self-image?

  • To prove to yourself that you can?

Loving the way you feel and look contributes so much to your overall well-being.


It's about the confidence you gain. It's about the new outlook on life you get. It's about realizing your beliefs and assumptions were just that...beliefs and assumptions.

It's about a new attitude of, "What's next?" because when you conquer yourself, you truly feel like you can overcome anything, and that is life changing!

Here's how gaining control changed Kathy's life.

"In one week my husband and I are having the holiday of our dreams. We are going to Canada (very long plane ride for us from Sydney!) and doing 2 weeks of walking in the Rockies. I am the most fit and able I have been since cancer 5 years ago."

This is the power of why!

3.) Conquer Emotional Eating

Emotional eating is when we eat outside of being physically hungry. It’s when we turn to food to fill a void or to numb our emotions.

This is an important concept, especially now. Earlier, we spoke about anxiety, worry, and despair. So often, eating is a way to comfort ourselves and how to cope with these negative emotions.

So not only do we have to question our beliefs, we must question our hunger.

If you suspect your hunger might be emotional, ask yourself what you are really hungry for?

  • Perhaps, it’s been a stressful day.

  • Maybe we’re seeking the pleasure of food.

Sometimes, it can be very helpful to explore what it feels like to have the need go unmet by simply writing about it. Many clients have reported that this eases the discomfort tremendously, and of course, like all discomfort (and pleasure) it will subside.

Helping clients overcome emotional eating is a big part of what we do.

4.) Get Support

Deciding to lose weight is a big step in putting your health first. And you may genuinely believe you cannot beat this extra weight.

That’s why it is important to have someone on your side. Someone in your corner that will give you daily support and motivation.

Kathy points out, "The daily feedback was key to getting me over the line! I genuinely was not sure I could lose weight."

And this is exactly what we do at MyBodyTutor, we are expert weight-loss coaches who are you every step of the way.

  • We have countless examples of people who were told they could expect to gain weight and to just accept this fact, but didn’t, like Amy.

  • Countless examples of people who just believed their body was stuck like Laurie.

  • Countless examples of people who thought it was "genetically impossible" to have the body they wanted like Matt.

If you need help losing weight and building a plan that will work for you, this is what we live for!

When you join MyBodyTutor, you’ll get practical, real-life support from coaches that understand the struggles of life.

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