Breast Cancer and Weight Changes

Women with breast cancer often complain of weight gain as an undesirable side effect to their treatment. Women treated with chemotherapy are 65% more likely to gain weight than those patients who undergo other forms of treatment. Premenopausal women undergoing chemotherapy are at the greatest risk for weight changes.

Many women who have chemotherapy for breast cancer have reported an average weight gain of about 5 to 8 pounds over a year. Some have reported gaining less while others have gained as much as 25 pounds.

What causes weight gain with breast cancer?

Many things contribute to weight gain. One reason for weight gain could be premature menopause brought on by chemotherapy. Menopause makes it easy for you to gain weight. That's because it causes your metabolism to slow down. There is also a change in body composition. Your body gains more body fat and loses lean muscle.

Normal weight gain involves a gain in both fatty and lean tissue. The weight gain brought on by chemotherapy, though, involves only fat. The loss of lean body mass and the gain of body fat are typical of the normal aging process. A woman having chemotherapy ages the equivalent of 10 years over the course of just one year.

Some research suggests that weight gain is also related to lack of exercise. The drop in the level of physical activity may be due to the fatigue, nausea, and pain that come with breast cancer treatment.

Weight gain may also be related to intense food cravings. Some women have cravings that typically involve sweets and carbohydrates during chemotherapy. These foods can cause weight gain, especially when they're not eaten in moderation.

Do other breast cancer medications cause weight gain?

Women undergoing other forms of breast cancer treatment gain an average of 2 pounds a year. Women taking steroid medications during cancer treatment may also experience weight gain. The weight gain associated with steroids, though, usually only becomes noticeable after weeks of continuous use.

Steroids are hormonal substances that cause an increase in fatty tissue. The usual result is a fullness of the neck or face and a big belly. Another side effect of steroid medications is loss of muscle mass. That loss of muscle makes weight gain more apparent.

Hormone therapy is another treatment that can cause weight gain. Hormone therapy decreases the amount of estrogen and progesterone in females and testosterone in males. The treatment tends to cause an increase in body fat mass. At the same time, there's a decrease in muscle mass and a change in the way food is metabolized.

Many women taking tamoxifen have felt the drug was responsible for their weight gain. So far, though, no conclusive studies have shown a relationship between this hormone and weight gain.

Interestingly, weight gain is not typical in women who have undergone surgery alone. The same is true of women who have had surgery followed by radiation.