Weight gain a greater cancer risk after menopause
By Times Staffer
Published July 17, 2006
- V. Upender Rao
Researchers from Harvard Medical School and Harvard School of Public Health examined weight gain and weight loss in the adult lives of women and its effect on the risk of breast cancer.
They studied a cohort of post menopausal women who were part of the Nurses' Health Study. The study consisted of 87,143 post-menopausal women between ages 33 and 55. Their change in weight from age 18 onward was recorded. These women were followed for up to 26 years.
A second cohort of 49,514 women was studied for weight gain from the onset of menopause. These women were followed for up to 24 years.
The study found that weight gain throughout the adult life was associated with an increased risk of breast cancer, but more so with post-menopausal weight gain.
Weight loss, both in adult years and in the post-menopausal life, was associated with a reduced risk if the women did not take hormones after menopause. The increased risk of post-menopausal hormone replacement was stronger than the decreased risk of post-menopausal weight loss.
The beneficial effect of the later was masked by the deleterious effect of the former.
Weight gain before age 18 was protective for breast cancer, because of slower pubertal growth or greater likelihood of irregular menses and ovulatory infertility in adulthood.
Benefits of weight loss in improvement of blood pressure, blood lipids and glucose metabolism are well documented, but decrease in cancer risk has only been postulated. This study, with its prospective nature, large number of patients and long period of followup, lends greater credence to this long-suspected ill effect of weight gain, particularly post-menopausal weight gain, and its associated risk of developing breast cancer.
After menopause, ovarian function rapidly diminishes. One other source of post menopausal female hormone is adipose, or fatty tissue, where adrenal androgens are converted to estrogen by a process known as aromatization.
Elimination or decrease in the amount of fat by way of weight loss will result in decreased estrogenic stimulation of the breast tissue and decreased incidence of breast cancer. Therefore, weight can be considered as a modifiable risk factor for breast cancer and weight loss as being beneficial.
This study, entitled Adult Weight Change and Risk of Post menopausal Breast Cancer, appeared in the July 12 issue of the Journal of the American Medical Association.
V. Upender Rao, MD, FACP, practices at the Cancer and Blood Disease Center in Lecanto.