In the study, 100,000 women recorded their current body weight and their weights at age 18, 35 and 50. The average weight gain between the ages of 18 and 50 was 34 pounds.
The researchers found that women who gained weight, became overweight (BMI = 25-29.9) or obese (BMI ≥30) at any time during their adult lives were more likely to develop advanced breast cancer or tumors. Click here to calculate your body mass index (BMI).
Slight weight gain or weight loss was not associated with increased or decreased risk of breast cancer.
Women who had relatively early menarche (first menstrual period) or who received hormone replacement therapy for menopause were less likely to have weight gain as a factor for developing breast cancer.
It's thought that weight gain increases breast cancer risk since excess body fat can be used as a site for estrogen accumulation. Previous studies have linked estrogen exposure to increased breast cancer risk but the link between weight gain and breast cancer is unclear.
One in nine Canadian women will develop breast cancer during their lifetime, making it the most common cancer affecting women in Canada.
For more information about diet and breast cancer see Leslie's nutrition strategies for preventing breast cancer.
All research on this web site is the property of Leslie Beck Nutrition Consulting Inc. and is protected by copyright. Keep in mind that research on these matters continues daily and is subject to change. The information presented is not intended as a substitute for medical treatment. It is intended to provide ongoing support of your healthy lifestyle practices.