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Two friends kayaking as a man aims to get fitter and healthier after weight gain during cancer treatment

9 Tips to Combat Weight Gain During Cancer Treatment

Reading time | 5 mins
We often think of weight loss when it comes to cancer and cancer treatment, but weight gain is common for many people undergoing medical or hormonal therapies. Todd Seals shares how he kept his weight stable despite the initlal weakness and fatigue.


It’s not talked about often, but did you know that gaining weight is typical for people undergoing medical or hormonal treatment for breast of prostate cancer? It certainly happened to me.

Many oncologists have told me that they prefer that patients put on a few pounds. But significant weight gain may lead to health issues such as high blood pressure, diabetes, and heart disease.

Although I struggled with muscle loss, I started with zero interest in exercising during cancer treatments. I eventually found solutions that helped me to keep my weight in check. 

Over the last 13 years, my weight has never varied by more than a few pounds. More importantly, I feel good.

My weight gain during cancer treatment

I had prostate cancer and gained 15 pounds in the first year of treatment. I wasn't concerned that I was putting on weight at first. I had been sick for a long time before my diagnosis. I needed to gain a little weight to look healthy. 

But after gaining the first 10 pounds, I realised I needed to make changes to maintain a healthy body mass index. With a few adjustments, I found that my weight gain stabilised after the first year.

Cancer makes establishing a consistent workout routine complicated. I didn't always feel too well a couple of days after treatment. When I felt better, I still had fatigue. And when it came to another round of treatment, I still felt shattered. It was a vicious cycle. 

How to keep weight gain in check

Unfortunately, there's no magic bullet to maintain a healthy weight, but some strategies may help.

Finding an exercise regimes that suit your body's current condition 

Exercise helps minimise muscle atrophy and weight gain. 

I found that exercising was the last thing I wanted to do when I began treatment. I felt exhausted and sometimes nauseous. Ironically, exercise can sometimes help with fatigue.

A healthy diet is also key to minimising weight gain during cancer treatments. But even with the best intentions, many of us aren't sure where to start with a healthy diet.

I understand just how difficult it can be to maintain a new diet and exercise program when getting cancer treatment.  

Understand your nutritional needs

I was lucky to have a nutritionist on staff at my place of employment. He helped me understand how my body had changed due to cancer treatments. He also helped me build a healthy diet around my new nutritional needs.

If you aren't already working with a nutritionist, ask your doctor to refer you to one. A nutritionist can help you to adjust your diet to meet your needs, so you not only limit weight gain but feel better.

Your body's changed - adapt your portion sizes to suit it better 

My nutritionist taught me that my metabolism had slowed and needed a lower calorie intake. I learned that moderation was key to healthy eating while undergoing cancer treatment.

Choose fresh over packaged

I learned lots of packaged food at the grocery store has many nutrients processed out of it - with tonnes of unnecessary sugar, salt, and fats added in. 

Ultra-processed food may alter our hunger hormones and cause us to eat too many calories, which leads to weight gain. I choose fresh foods when possible.

Don't skimp on a few essential nutrients

My nutritionist suggested that I eat at least 100 grams of protein a day to avoid losing muscle mass. 

Protein helps our bodies to build and maintain muscle. It also keeps you feeling full to control weight. The amount of protein you'll need will vary. A nutritionist can help you figure out a goal that's right for you.

My nutritionist told me to be sure and get enough fibre. Fibre helps keep things moving through your digestive system. It also keeps you feeling fuller for longer after eating, so you start to eat less over time.

I also learned that healthy fats, such as those found in nuts, avocados, and fatty fish, are just as crucial to your diet needs as protein or carbohydrates. They give you energy and help you feel full. 

Finally, plenty of calcium and vitamin D are a must to keep bones healthy - especially when hormone therapy can make your bones weaker. I started drinking vitamin D-fortified orange juice. Other good sources include fatty fish and fortified dairy. 

Start your exercise program slowly

I was a long-distance runner before developing cancer. I'd completed many marathons and half-marathons. I once even finished a marathon with a time good enough to qualify for the Boston Marathon!

Lung metastasis (when cancer cells forming tumours in the lungs originated then spread from elsewhere in the body) took away my ability to run long distances. But it didn't take away my ability to walk or ride bicycles. I discovered that it doesn't take much physical activity to feel better.

Consult with your doctor before beginning any exercise program. Start slow but be consistent when you start your exercise routine. Don't do more than your body can handle.

Try to move just a little bit each day. It wasn't easy at first. Those early walks were no more than a quarter-mile. But we went out and did it every evening, willingly or not!

Build on your success

Build on duration and difficulty as you have more stamina.

My walks became longer with time. I began to feel better and have more energy. I started looking forward to them. We started walking farther after a couple of weeks. I later added hand weights, distance, and hills. These days, our walks average about 3 miles.

Add in resistance training to build muscle

Research suggests that resistance training helps reduce both muscle loss and fat gain.

Today, getting exercise is a way of life for my wife and me. We don't have a set schedule or routine at the gym. We just try and do something every day. We've thrown cycling and kayaking into the mix. I've found that kayaking helps me to maintain upper body strength. Cycling is an excellent aerobic exercise that's helped me build core and leg strength.

Find a friend

Exercise is way more fun when you have someone to talk to. It's also a lot more fun when you can incorporate a little friendly competition with someone else who's as interested in staying in shape as you are.

The takeaway 

My nutritionist taught me to not be discouraged if I didn't see immediate results.

You may not see the scales tip in your favour right away. I realised that I was in a marathon, not a sprint.

Cancer changed many aspects of my life. I learned early on that I was in control of many of those changes, to a degree. I hope what I've learned over the years can help others who are just starting down this road.

For more information on managing a cancer diagnosis, reach out to your doctor or healthcare team.

NPS-IE-NP-00278 March 2022