Chicago researchers have said that women who put on weight in their adulthood have higher risk of the developing breast cancer. The hormone estrogen collects in fat tissue and advances cancerous cells in breast.

The study, carried out amidst women who did not take hormone therapy after menopause, has found that women became obese had 1.4 times higher the risk of breast cancer as compared to women whose weight remained constant or reduced.

In the October issue of the Archives of Internal Medicine, Jiyoung Ahn of the U.S. National Cancer Institute wrote, “The present findings indicate that the relations of adult weight gain to breast cancer is evident throughout the entire adulthood life span rather than being limited to a specific time in life. These findings may reinforce public health recommendations for the maintenance of a healthy weight throughout adulthood as a means of breast cancer prevention.”

Ahn and a team of researchers examined the case of 99,039 postmenopausal women, who reported their weights at age 18, 35, 50, and out of them, 2,111 developed breast cancer.

In study, women on average gained more than 34 pounds during their adult lives, roughly evenly divided in ages between 18 and 35, 35 and 50, 50 and current age, and 8 percent maintained their weight.  

Women who start menstruating early in life or who took hormone-replacement therapy during or after menopause, have low risk factor of weight gain.

Researchers wrote, “Because weight gain during adulthood mainly reflects the deposition of fat mass rather than lean body mass, weight gain potentially represents age-related metabolic change that may be important in breast cancer development. These findings may reinforce public health recommendations for the maintenance of a healthy weight throughout adulthood as a means of breast cancer prevention.”

Study concluded that weight gain in adulthood increased the risk of breast cancer, but study didn’t make it clear whether modest weight gains increased the breast cancer risk.

This year, about 178,000 new cases of breast cancer are estimated, including 40,000 deaths.