Weight Gain and Breast Cancer

A recent study revealed at the American Association for Cancer Research 101st Annual Meeting, 2010, purported that significant weight gain and a concurrent increase in Body Mass Index (BMI) was connected to an increase in postmenopausal breast cancer risk. The study showed that a BMI increase of 5 kg/m2 or more between subjects ranging in age from 20 years old to 50 years old had nearly double the postmenopausal breast cancer risk. This study was encouraged by the established connection between postmenopausal weight and breast cancer.

Body mass index (BMI) is a controversial measure of body fat based on height and weight that applies to both adult men and women. Though it does not actually measure the percentage of body fat, it is used to estimate a healthy body weight based on a person's height and current weight. As a result, some individuals may have a high BMI but not a high percentage of body fat and may not actually be overweight or obese. In regards to the study, a BMI increase of 5 kg/m2 is equivalent to a woman of average height, 5'4", gaining approximately 30 pounds.

In previous studies, excess weight has been linked with increased risk of postmenopausal breast cancer because fat cells produce excess estrogen. However, only small studies have specifically explored an increase in BMI and its timing in relation to postmenopausal breast cancer risk. This larger study consisted of 3,677 cases of postmenopausal breast cancer. The researchers used observations only among women who had never used menopausal hormone therapy.

"Compared with women who maintained approximately the same BMI, those who had an increase of 5 kg/m2 or more between age 20 and study entry had a nearly twofold increased risk of breast cancer," said Laura Sue, M.P.H., a cancer research fellow at the National Cancer Institute (NCI).

Women who reported a BMI increase of 5 kg/m2 or more between age 20 and 50 were at an 88 percent increased risk of developing postmenopausal breast cancer, compared with women who reported a stable BMI. For women who reported a BMI increase of 5 kg/m2 or more after the age of fifty had a 56 percent increased risk, compared with women who maintained a healthy weight. Weight gain, as seen as an increase in BMI, both before and after age 50, independently contributes to an increased risk of postmenopausal breast cancer.

A healthy BMI number is between 18.5-24.9. Eat healthy, avoid refined sugar, get moderate exercise, and try to lose weight if necessary to bring your BMI number into the healthy range.