Another study, by researchers at the Johns Hopkins Bloomberg School of Public Health, found that weight gain after a diagnosis of invasive breast cancer could significantly increase a women's risk of death from the cancer.
The study of more than 4,000 women with breast cancer classified them by body mass index, a ratio of weight to height. For obese women, the risk of dying of breast cancer was 2.4 times greater than for women with a normal body weight, a relationship that persisted when age, menopausal status and smoking were taken into account.
Another Johns Hopkins study provided a possible explanation for the lower risk of prostate cancer seen in men with diabetes. The researchers matched 264 men diagnosed with the cancer with a group of 264 cancer-free men, measuring C-peptide levels in both groups.
Men with elevated blood levels of C-peptide when the study started were one-third less likely to develop prostate cancer than those with lower levels. Men with higher C-peptide levels had half the risk of developing prostate cancer confined to the prostate.
The protective effect of those high levels could be due to the activity of insulin in relation to the male hormone testosterone, Plantz said. C-peptide derives from the same parent molecule as insulin, and insulin is known to reduce the activity of testosterone, which stimulates the growth of prostate cancer, she said.
The possible protective effect of insulin against prostate cancer could offer a mirror image of the negative effect of estrogen -- the female sex hormone -- in breast cancer, said Dr. Rexford Ahima, professor of medicine at the University of Pennsylvania.
"We have known for years that women who are obese are at high risk of breast cancer," Ahima said. "Fat tissue makes estrogen, which promotes breast cancer. The frightening thi
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