Can you gain weight during cancer treatment?

Yes. Although many people with cancer lose their appetite and lose weight, you may gain weight during cancer treatment, according to the National Cancer Institute.

Weight gain is more common if you have ovarian, breast, or prostate cancer, but each person is different—having one of these cancers doesn't mean you'll gain weight, and you may gain weight with a different type of cancer.

There are several causes. Fluid retention from a tumor or fluid buildup can add weight. Increased appetite may come from the cancer, treatment, or medicines. Hormone therapy can slow your metabolism, so you burn less energy. Steroids often given during treatment increase appetite and can make the body hold onto water. And fatigue or pain can make you less active, which can also lead to weight gain.

Small weight changes during treatment are normal and expected. But if weight gain is sudden—such as 5 pounds in a week—or doesn't stop, tell your doctor right away so they can assess the cause. To manage it, your doctor or dietitian may suggest high-fiber foods, lean proteins, limiting fat, salt, and sugary drinks, and staying as active as you can.