Why Am I Gaining Weight During Cancer Treatment?

person standing on a scale

As you go through cancer treatment, you may not expect weight gain as a side effect. While a commonly known side effect of cancer is weight loss, some treatments can cause the opposite – weight gain.

  • Chemotherapy can cause fatigue, so you don’t feel like being active. 
  • Steroids such as prednisone and dexamethasone can make you feel hungry, which may cause you to end up eating more calories than you need. Steroids can make your body retain water and feel puffy. They may also cause your body to store fat more easily.
  • Radiation treatment directed at the brain can sometimes result in weight gain. 

If weight gain becomes a problem, ask your health care team about ways to prevent it or ways to safely lose excess weight. 

Eating Healthy, Staying Active, and Sleeping Well

You may already know the basics of healthy eating, like eating lots of fruits and veggies, along with choosing foods high in fiber. Working with a dietitian may also help you stick with healthy, tasty food that isn’t as likely to cause weight gain. The National Cancer Institute offers lots of Eating Hints that can help you avoid weight gain.  

Treatment and cancer itself can make you feel more tired and less active. When you’re feeling treatment fatigue, it’s hard to believe that getting active will give you more energy. But it can! It will also help you feel better. Ask your team for tips about the best activities for you. 

Weight gain and poor sleep quality are linked. Being overweight puts people at more risk for sleep apnea. With this condition, people can stop breathing for a short time during sleep. Sleep apnea can make people feel tired during the day, which makes it hard to concentrate. If you’re not sleeping well, talk with your health care team.

Are healthy habits worth it? Research studies show that the habits you set up while you’re young will follow you into adulthood. Those healthy habits can help you avoid all kinds of health problems in the future, like high blood pressure, type 2 diabetes, and cancer.

Strong Emotions Can Go Along with Weight Gain

It’s normal to feel anxiety about body changes like weight gain. You’re right to have any feelings you have, including:

  • Sadness
  • Anger
  • Shyness
  • Embarrassment
  • Frustration
  • Self-consciousness (awareness or worry about what others think about you)

Sometimes, when our bodies are under more stress than normal, weight changes can occur. It is important to remember that you need to give yourself some time to adjust to these changes. Make sure that you are fueling your body in a healthy way while remaining active.

Sharing Feelings with Friends and Partners

Teens and young adults often compare themselves with others, like friends. But most of your friends aren’t going through cancer treatment, and all the challenges this brings. Right now, you need the joys of friendship and fun. So try not to avoid friends, school, work, or photos because of weight gain. 

If you feel awkward about how your friends will react to your weight change, try being open about your feelings. They’ll most likely offer an understanding ear, as well as reassurance. That includes your romantic relationships. The right partner will support you at any weight.

Right now, you need the joys of friendship and fun.

Bullying as a Result of Weight Gain

You thought you were doing well, feeling good. Then someone posts an unflattering photo of you on social media. And the photo features your weight gain, front and center. You’re right if you believe that being overweight carries stigma, or negative attitudes and beliefs. Some people may act on their negative beliefs.

Have you been the target of teasing, social exclusion, or bullying? Talk to an adult you trust if this is happening. 

Whether it’s in-person or cyberbullying, these experiences have the same negative effects on your feelings. And it can put you at more risk for:

  • Low self-esteem and poor body image  
  • Depression and anxiety
  • Substance use
Teen holding a weight in one arm and flexing arm muscle in other arm

Managing Weight Gain During Treatment: Tips for Teens and Young Adults

Getting cancer wasn’t in your control. Neither is the treatment you need to get well. It may seem like nothing is in your control. But you can do a lot for your overall health right now. And some of these healthy habits can have positive effects for the rest of your life:

  • Eat healthy. Does that mean you can’t splurge? No. But a yummy fruit smoothie packed with vitamins and minerals can be just as tasty as a bowl of ice cream—better for your health and your weight. Read more about healthy eating after cancer so you can start great habits now. 
  • Avoid using food as a reward or to manage your emotions. It’s easy to do this, especially when you’re feeling down. It can make you feel better short-term, but long-term, it’s a recipe for weight gain. And afterward, you’ll feel even worse than before. 
  • Talk with your health care team if you’re not sleeping well. Weight gain and poor sleep quality are linked. 
  • Stay as active as you can. It can give you more energy and help you feel better. One idea is to find a buddy. It’s harder to skip exercise when someone is waiting for you. Try a new activity with friends, like walking, hiking, skating, or swimming. Read more about physical activity after cancer for ideas.
  • Get the whole household into healthy habits. People your age often tend to follow the same eating and exercise habits as their parents (insert gasp here). So healthy changes work better when the whole household takes part. And more fun, too. You can connect and create great family memories:
    •  Finding recipes and shopping
    • Cooking together
    • Trying new activities
    • Spending time in nature
  • Get help to manage your mental and social health. Your friends and family are great sources of support. Talking with a counselor can also help you manage your feelings and find ways to feel better. Or join a support group or online forum with other young people going through similar body changes. This support can help protect your mental health and self-esteem, especially if you’ve been the target of bullying or had other negative experiences.
  • Express Your Feelings. Express yourself with music, art, writing, or other creative pursuits that give you joy. Find a friendly ear—someone who listens when you want to talk. Your feelings are valid and it’s ok to feel the way you do. 
  • Develop confidence in yourself. Think about all that you do. You’re going through cancer and treatment, along with “normal life” stuff like school, work, friends, and family. You deserve to feel good about yourself, no matter what your weight.
  • Remember that you haven’t changed. You are still you in all the wonderful ways that matter.
ways to manage weight gain

Let’s Review

  • Some treatments like chemotherapy, steroids, and radiation treatments directed at the brain can cause weight gain.
  • Healthy eating, physical activity, and sleep habits can help you avoid weight gain.
  • It’s normal to feel anxiety and other emotions about body changes.
  • Be open with your feelings about weight gain and expect support from friends, family, and partners. 
  • Due to the stigma of weight gain, some people experience teasing, social exclusion, or even bullying. If this happens, get support from friends and family. A counselor can help, too.
  • Express your feelings with creative pursuits or to a friendly ear. It’s ok to feel the way you do.
  • Try to develop confidence in yourself and protect your self-esteem. You deserve to feel good about yourself.


Reviewed: June 2021