It has been known for a long time that obesity brings health risk like diabetes and heart disease, but, according to a new research, being obese may also make locally advanced breast cancer behave more aggressively and worsen women’s prognosis.

“We already know that obesity is a risk factor for many disease, and now we’re showing that women who are obese or overweight essentially face a higher risk for getting a more aggressive form of breast cancer, and progress faster and die faster from their disease,” study senior author Dr. Massimo Cristofanilli, an associate professor in the department of breast medical oncology at the University of Texas M.D. Anderson Cancer Center in Houston said quoted by the Washington Post.

Dr. Cristofanilli and his colleagues looked at 606 women with advanced forms of breast cancer between 1974 and 2000 who were split up into three groups: normal, overweight and obese. Women in the obese group had a body mass index or BMI of more than 30, while women in the normal group had a BMI of 24.9 or less.

The overall five-year survival was 56.8 percent among obese women, 56.3 percent among overweight women and 67.4 percent among normal weight women, while the 10-year survival rate was 42.7 percent among obese women, 41.8 percent among overweight women and 56.5 percent among normal weight women.

Dr. Cristofanilli also found that inflammatory breast cancer was more often found in obese and overweight woman than in women with normal body weight at 45 percent, 30 percent and 15 percent respectively.

“The more obese a patient is, the more aggressive the disease. We are learning that the fat tissue may increase inflammation that leads to more aggressive disease,” Dr. Cristofanilli said in the study.

The recurrence rate was nearly 50 percent for the obese and overweight women, compared to 38.5 percent for normal weight women.

The researchers also gave an explanation for their findings which says that the hormone leptin, produced mainly in adipose tissue, promote tumor growth, invasion, and angiogenesis, “thereby promoting a more aggressive tumor,” Dr Cristofanilli said.

Dr. Harold J. Burstein, an assistant professor of medicine at Harvard Medical School and tha Dana-Farber Cancer Institute in Boston did not agree with Dr. Cristofanilli’s findings saying that a link between obesity and poor breast cancer outcomes is “less than overwhelming.”

“There's a lot of suggestive data, but there's nothing that's absolutely definitive. That is not to say that there is anything to suggest that it is risky for breast cancer patients to make an effort to maintain their weight through food control and exercise. And it can certainly help strengthen bones and lower the risk for diabetes and heart disease, which is all the better,” Dr. Burstein said, according to the Post.

The study, funded by the Susan G. Komen Foundation, the Nellie B. Connally Fund for Breast Cancer and the Inflammatory Breast Cancer Research Group, appeared in the March 15 issue of Clinical Cancer Research.