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A new study suggests that obese women could perhaps cut down their risk for postmenopausal breast cancer by taking measures during perimenopause to prevent weight gain and to therapeutically control the metabolic effects of their obesity, Medical Xpress reports.

"Obese postmenopausal women have increased risk for breast cancer and poorer clinical outcomes compared with postmenopausal women who are lean," said Paul S. MacLean, Ph.D., associate professor of medicine at the University of Colorado Anschutz Health and Wellness Center in Aurora, Colo.

"The reasons for this are not fully understood. Unfortunately you cannot do the studies needed to address this issue in humans. So, we merged rat models of obesity, breast cancer and menopause to best mimic the events that link premenopausal obesity to an increased rate of postmenopausal breast cancer."

Weight gain is common in women during menopause due to the consumption of extra food that is not really required by their body.  

In the current study, researchers have confirmed with an experiment conducted on mice that obesity and overfeeding after surgical ovariectomy together drives aggressive tumor growth and progression.

According to the study, the reason was that obese rats were unable to handle the excess sources of energy in the form of glucose and dietary fat. However, the rats that were thin, appropriately stored the excess glucose and dietary fat from overfeeding in the liver, fat, muscle and healthy breast tissues.

In obese rats, while the healthy tissues were unable to increase uptake of glucose and dietary fat, it was found that the breast tumors dramatically increased uptake of glucose, hence aggressively increasing its growth.

Another reason for the enhanced tumor growth in obese rats could be that they have different molecular profiles when compared to lean rats. Tumors from obese rats had higher levels of expression of the progesterone receptor (PR), which was related to higher expression of genes involved in energy use and proliferation, the report said.

"If our findings in rats translate to humans, it means that the perimenopausal period is a critical window of time for determining breast cancer risk later in life," said MacLean.

"This, in turn, means that an obese woman's risk for postmenopausal breast cancer and poor clinical outcome could be reduced by perimenopausal lifestyle modifications, such as restricting food consumption and increasing exercise, and/or perimenopausal use of drugs, such as metformin, to improve metabolic control."

The results of a preclinical study are published in Cancer Research, a journal of the American Association for Cancer Research.