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Breast Cancer Weight Loss or Gain: Changes During Treatment

Breast Cancer Weight Loss or Gain: Changes During Treatment

Breast cancer is a dangerous disease, especially among women. The course of treatment for breast cancer can have many side effects on the patient, such as fatigue, stress, hair loss, temporary menopause, and others. Another side effect is breast cancer weight loss or weight gain, which often occurs during treatment.

Breast Cancer Weight Gain

Weight gain may occur when a patient undergoes breast cancer treatments. In addition, lifestyle factors during treatment may also contribute to weight gain.


Studies indicate that some patients undergoing breast cancer treatment will become overweight. The weight gain may be sustained even when treatment has ended. For some patients, they may lose muscle and increase fat tissue. The usual methods of weight loss like diet and exercise may not work for them. One reason for weight gain is the use of corticosteroids, which increase appetite. Corticosteroids are hormones that can also cause an increase in fatty tissue. Women treated with steroids can also gain weight after several weeks of continuous use.

Hormone Therapy

Treating cancer with hormone therapy may be another cause of weight gain. This treatment reduces the amount of estrogen and progesterone in women and testosterone in men. When the levels of these hormones are reduced, this tends to increase the amount of body fat, reduce muscle mass, and cause a change in the way the body converts food into energy.

Many women feel that the use of the drug tamoxifen makes them gain weight. However, no study has ever shown the relationship between hormones and weight gain. Becoming overweight can increase the risk of heart disease, hypertension, diabetes for patients. It can also particularly increase the risk of breast cancer recurrence.

Lack of Exercise

Many studies show that weight gain is related to lack of exercise. When undergoing cancer treatment, patients often feel stress, fatigue, nausea, and pain. This can lead to a reduction of physical activity and exercise. Weight gain may also be related to an increase in appetite. Some women crave sweets and carbohydrates in chemotherapy.

Breast Cancer Weight Loss

Some patients after breast cancer treatment have the opposite problem: They lose weight due to a loss of appetite, nausea and other side effects caused by chemotherapy. Some male patients say that weight loss is a major problem for them. The weight loss makes them feel that their health is getting worse and that they are “less masculine.”

Breast cancer weight loss can also lead to problems in recovery even when treatment is successful. Losing weight makes patients lose energy and suffer nutrient deficiencies, making it more difficult for the patient to recover.

Maintaining a healthy body weight during treatment for breast cancer is very important. Patients should seek a doctor’s advice in setting up a complete diet and a program that provides good nutrition. Finally, patients should exercise regularly; vigorous exercise for the arms and shoulders can prevent the loss of muscle and the increase of adipose (fatty) tissue.

Learn more about Breast Cancer here.

Hello Health Group does not provide medical advice, diagnosis or treatment.


Breast Cancer Treatment (PDQ®)–Patient Version. https://www.cancer.gov/types/breast/patient/breast-treatment-pdq. Accessed October 13th, 2016.

Breast Cancer Treatment and Pregnancy. https://www.cancer.gov/types/breast/patient/pregnancy-breast-treatment-pdq. Accessed October 13th, 2016.

Inflammatory Breast Cancer. https://www.cancer.gov/types/breast/ibc-fact-sheet. Accessed October 13th, 2016.

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Written by Kristel Dacumos-Lagorza Updated 3 weeks ago
Fact Checked by Cesar Beltran