Body fat levels linked to breast cancer risk in post-menopausal women - CNN

"We find that excess body fat in those who are post-menopausal with a normal body mass index is associated with a doubling of estrogen-dependent breast cancer risk," said Dr. Andrew Dannenberg, one of the authors of the study and director of cancer prevention at the Sandra and Edward Meyer Cancer Center at Weill Cornell Medicine.
The American Cancer Society states that estrogen-dependent tumors, called ER-positive breast cancer in the study, occur when receptor proteins in or on cells attach themselves to the estrogen hormone and rely on it to grow.
The researchers studied 3,460 American women between the ages of 50 and 79 who had gone through menopause. Women were part of the Women's Health Initiative and had measured their body composition at the start of that program, Dannenberg said. Of those women, 146 developed ER-positive breast cancer, and researchers sought a relationship between excess body fat and the development of this tumor.

They found that an increase of 5 pounds (11 pounds) in the fat mass of the whole body was associated with a 35% increase in the risk of this type of breast cancer. An increase of 5 kg of fat mass of the trunk was associated with an increase in risk of 56%.

The fat of the trunk is "defined by the fat contained in the bust apart from the head and the limbs", according to the study.

The study also found that for invasive breast cancer, which has spread to the surrounding breast tissue, an increase of 5 kg in whole body fat was related to an increased risk of 28%. The same increase in trunk fat was linked to a 46% increase in the risk of invasive breast cancer.

"The main takeaway is that having excess body fat, even when you have a normal body mass index, is associated with an increased risk of breast cancer," Dannenberg said.

A person's BMI is calculated through a formula that implies their height and weight; a "normal" BMI is considered between 18.5 and 24.9, according to the study.

The researchers also examined the blood data taken at the start of the Women's Health initiative for other factors that are known to play a role in the development of breast cancer, such as the increase in insulin molecules.

The results "highlight the importance of research that differentiates the contributions of body size, body composition and metabolic profiles to breast cancer risk", Drs. Isabel Pimentel, Ana Elisa Lohmann and Pamela J. Goodwin wrote in an editorial published together with the study.

The editorial authors also point out that other researchers have looked at the topic with different results and have noted that "these observations suggest that the components of metabolic health, rather than the presence of a complete metabolic syndrome, may contribute to the risk of cancer otherwise".

How much a decade of obesity increases the risk of cancer
A particular strength of the research of Hoda Anton-Culver, distinguished professor in the Department of Medicine of the University of California, Irvine, has been the analysis of the position on the body of fat levels.

"I think it's a good step forward that takes us from looking at the body mass index as an indicator of obesity to really looking at the particular site of fat concentration in the body," said Anton-Culver, who he was not involved in the research.

The scientists knew that there was an association between obesity and cancer, but Anton-Culver states that the new study shifts research beyond that general association.

"They say correctly in the summary, that obesity is associated with breast cancer, but more specifically, obesity around the abdomen is more specific to that association," he said.

Although Anton-Culver thinks the research is strong, he emphasized that it looked like only a specific cancer.

"I do not know if we look at the same problems with other tumors because the result, what will be, is specific for breast cancer?" she said. "We need to ask that question later, because obesity is a risk factor for other cancers."

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