Two studies that look at the role of diet, weight, and obesity in breast cancer. From Science News:
Calorie restriction during treatment for breast cancer changes cellular programming in a way that lowers the chance of metastases in mice. Breast cancer patients are often treated with hormonal therapy to block tumor growth, and steroids to counteract the side effects of chemotherapy. However, both treatments can cause a patient to have altered metabolism which can lead to weight gain. In fact, women gain an average of 10 pounds in their first year of treatment. Recent studies have shown that too much weight makes standard treatments for breast cancer less effective, and those who gain weight during treatment have worse cancer outcomes.
From Medical Daily:
Obesity increases the risk of another cancer, which adds to the long list of life-threatening health hazards that accompany obesity. A new study reveals more evidence that obesity is a risk factor for cancer prognosis and its development, which will be presented at the annual meeting of the American Society of Clinical Oncology (ASCO) in Chicago on May 30.
Researchers found that out of the 80,000 women in the study who had early stage breast cancer, obesity increased the risk of death by 34 percent for women who were pre-menopausal and were susceptible to higher levels of the hormone estrogen.
"No matter how we look at it, obesity is slated to replace tobacco as the leading modifiable risk for cancer," Dr. Clifford Hudis, ASCO president and chief of Memorial Sloan Kettering Cancer Center's Breast Cancer Medicine Service in New York, announced at a news conference.
Fat tissue produces an excess amount of estrogen, and those with increased levels have been associated with the risk of breast cancer. Obese women unquestionably have more fat tissue, which is why their estrogen levels are naturally higher. This leads to a more rapid growth of estrogen-responsive breast tumors. Obese patients also have increased level of insulin and insulin-like growth factor-1, which has been known to promote the development of tumor tissue.
They did find, as they had expected, there was no link between obesity and breast cancer death risk among women who were postmenopausal and either had an estrogen receptor positive or estrogen receptor negative breast cancer. This meant the tumors did not rely on estrogen to grow at a time in a woman’s life when her estrogen levels are fairly low.
Obesity has been linked to an increased risk of many other common cancers as well, which include colon, pancreas, esophagus, kidney, thyroid, gallbladder, and endometrium. Endometrial cancer is found within the lining of the uterus, and those who are obese increase risk by up to 40 percent.