Dr. Clifford Hudis at Memorial Sloan Kettering cancer center explains that doctors used to think that this association was really seen primarily in older women, but here it's being seen in young women. Doctors aren't sure how obesity and cancer are linked. Dr. Freya Schnabel believes that the most popular theory is that obese women have more fat cells in their body and these fat cells do produce a little bit of estrogen which can in fact stimulate these hormone-sensitive cells.
Researchers also suspect obese woman have higher levels of inflammation in their blood which allow cancer to thrive. It's unclear if losing weight after diagnosis will improve a patient's outcome, but Hackett isn't taking any chances. The study doesn't link obesity to poorer outcomes for post-menopausal patients but doctors say it's always important to maintain a healthy weight.
The study focused only on women who were already diagnosed. It does not address whether obesity plays a role in causing breast cancer. Previous studies have shown that people who are overweight have an elevated risk for developing breast cancer.