Modest Weight Gain Increases Breast Cancer Risk in Premenopausal Women

With 736 premenopausal breast cancer cases in the Nurses’ Health Study, we show that a weight gain of 10 or more pounds in just 4 years is associated with significantly higher risk of breast cancer in the subsequent years after the weight gain. Why does this matter? Well, lots of women gain weight through their premenopausal years. Based on previous findings, it’s likely many of these women did not think that this could impact their risk of breast cancer? Here we show that short-term gain does increase risk, and that this risk is more important for receptor negative (that is ER-ve PR-ve) breast cancer – the type that is more common in premenopausal women and the type for which we don’t have effective treatments. Weight gain of 10 or more pounds in 4 years during premenopausal life, more than doubles risk of this hard to treat type of breast cancer. In additional analyses, we observed that the adverse effect of weight gain was present among premenopausal women regardless of their starting BMI (body mass index), a measure of adiposity. Normal weight and overweight women all experienced the increase in risk of breast cancer.

In context, the majority of epidemiologic studies of breast cancer have focused on postmenopausal breast cancer. Fully 75 percent of breast cancer is diagnosed after menopause. On the other hand, waiting until menopause to begin screening (early detection) and to consider prevention strategies for higher risk women, misses any hope of prevention for the almost 1 in 4 breast cancers diagnosed before age 50. Weight gain in the premenopausal years may be contributing importantly to the burden of premenopausal disease. Furthermore, in Asia, rates of premenopausal breast cancer are rapidly rising. They are now approaching the rates in the US for women of similar ages.(3) ER-negative breast cancer is more common in premenopausal women – representing 30% of breast cancer diagnosed among women 35 to 44 but only about 12% among women age 65 and older.(4)

Global data attest to the growing obesity epidemic among women and men around the world. One consequence of this weight gain in women through their early adult years now looks to be increased breast cancer. As low and middle income countries develop, they also transition to higher rates of breast cancer. Adding strategies to prevent premenopausal breast cancer remains our highest priority, as this cancer has the highest societal burden, being diagnosed among women in their peak years of work productivity and family care.

The good news is that we can avoid weight gain through increasing physical activity and making healthier food choices.

Tips

• Integrate physical activity and movement into your life.
• Eat a diet rich in fruits, vegetables and whole grains.
• Choose smaller portions and eat more slowly.
• Use your bathroom scale regularly, so you keep surprise weight gain at bay.
• Get a pedometer and work up to 10,000 or more steps per day.

For Parents and Grandparents

• Limit children’s TV and computer time.
• Encourage healthy snacking on fruits and vegetables.
• Encourage activity during free time.