Although people more commonly lose weight during cancer treatment, some people gain weight. Slight increases in weight during cancer treatment are generally not problematic. However, significant weight gain may affect a person's health and ability to undergo treatment.
Weight gain is an especially important health issue for women with breast cancer because more than half experience weight gain during treatment. Reports have shown that weight gain during treatment is linked to a poorer prognosis (chance of recovery). Being overweight before treatment begins also increases the risk of serious health conditions, such as high blood pressure, diabetes, and cardiovascular disease.
The following cancer treatments may produce symptoms that lead to weight gain:
Chemotherapy. Some chemotherapy causes the body to retain (hold on to) excess fluid in cells and tissues, which is called edema . In addition, chemotherapy often causes people to reduce physical activity, usually because of fatigue ; increases hunger, especially for high-fat foods; triggers intense food cravings; and decreases metabolism (the rate that the body uses energy). It may also cause menopause  in some women, which decreases their metabolism, increasing the likelihood of weight gain.
Steroid medications. Steroids are medications that are often used for cancer treatment to reduce symptoms of inflammation, such as swelling and pain. For some cancers, they are used as part of the treatment for the cancer itself. A side effect of these medications is an increase in fatty issue, resulting in a large abdomen and fullness in the neck or face. Steroids may also cause wasting (loss of both weight and muscle mass). A noticeable increase in weight usually only occurs when people have been taking steroids continuously for many weeks.
Hormone therapy. Hormone therapy for the treatment of breast, uterine, prostate, and testicular cancers involves medications that decrease the amount of estrogen or progesterone in women and testosterone in men. This can increase body mass from fat, decrease body mass from muscle, and decrease metabolism, resulting in weight gain.
Managing weight gain
Relieving side effects–also called symptom management, palliative care , or supportive careâis an important part of cancer care and treatment. Talk with your health care team about any symptoms you experience, including any new symptoms or a change in symptoms.
If weight gain becomes a concern, consult with your doctor or a registered dietitian (RD) before starting a diet or changing eating habits. They can help discover the possible cause of the weight gain and find the best way to manage it. In addition, an RD can provide nutritional guidelines or a customized diet plan.
Consider the following ways to address weight gain through diet and physical activity:
- Eat plenty of fruits, vegetables, and whole grains.
- Limit fat, sugar, and refined flour.
- Drink plenty of water.
- Try to use healthier cooking methods whenever possible, such as steaming instead of frying.
- Evaluate everyday eating habits, and try to identify behavior patterns that lead to overeating and inactivity.
- Find cardiovascular physical activities (such as walking or bicycling) that you enjoy, and do strength building exercises if muscle mass has been lost. However, check with your doctor before beginning a new type of exercise or increasing your amount of physical activity .
Managing fluid retention-related weight gain
It is important to call your doctor immediately if you experience any of the following signs of fluid retention:
- Skin that feels stiff or leaves small indentations on the skin after pressing on the swollen area
- Swelling of the arms or legs, especially around the ankles and wrists
- Rings, wristwatches, bracelets, or shoes that fit tighter than usual
- Decreased flexibility in the hands, elbows, wrists, fingers, or legs
The following tips can help you manage fluid retention:
- Ask a doctor about prescribing a diuretic medication (medication that increases urination) to rid the body of excess water.
- Lower the amount of salt in your diet.
- Avoid standing for long periods, and elevate your feet as often as possible.
- Avoid crossing your legs, which restricts blood flow.
- Weigh yourself at the same time each day, and keep a log of your daily weights. Be sure to bring this log with you to appointments so your health care team can evaluate them.
- Avoid tight clothing.
Weight Control 
Last Updated: February 10, 2012