THE CANADIAN PRESS

A woman's bra size at age 20 may predict her risk of developing Type 2 diabetes later in life, with larger cup size linked to higher rates of diabetes, a new study suggests.

After accounting for factors known to increase likelihood of diabetes – things like a family history of the disease, body mass index, level of physical activity, smoking status and waist-to-hip measurements – the researchers said the figures still show that women who wore B, C and D cups developed the disease at higher rates than women who wore A cup bras.

"I think the take-home message is that we have a new and thought provoking concept about how breast fatness or breast fat might be viewed as a contributor to Type 2 diabetes risk in a woman," lead author Dr. Joel Ray said of the study, published Tuesday in the Canadian Medical Association Journal.

But he and others cautioned that people should be careful in interpreting the findings – and should not feel compelled to try to reduce their breast size.

"The last thing I want to do is be freaking out a lot of D cup women, and also offending a lot of women along the way. Or having their doctors asking them whether they can measure their cup size or something like that. At this point it would be so wrong and premature," said Ray, a clinician scientist at the Li Ka Shing Knowledge Institute of St. Michael's Hospital in Toronto.

Dr. Diane Finegood, scientific director of the Canadian Institute of Health Research's Institute of Nutrition, Metabolism and Diabetes, said that even if a causal link been breast size and diabetes risk is proved – and this study doesn't do that – factors like a woman's family history of diabetes and her BMI are probably more important to her diabetes risk than size of her bra.

"In my opinion this is the sort of study that doesn't give the individual reader of the newspaper a whole lot of helpful information," said Finegood, who is based at Simon Fraser University in Burnaby, B.C.

"It's interesting from an academic point of view. But from a practical care point of view I don't think it says a lot."

Dr. Hertzel Gerstein, a diabetes expert and an epidemiologist at McMaster University in Hamilton, added another caution.

Gerstein noted the researchers used statistical formulas to factor out the influence of well known risks – like family history and BMI. But it is impossible to account for all risks, he said, suggesting a small increased risk might be further eroded if the researchers could look at things like whether the women with larger breasts were more likely to hold desk jobs, or drank more alcohol.

"I would look at this as an interesting observation that needs to be explored and understood better. And I would certainly not be alarmed if I was a woman who happened to have a D cup as opposed to an A cup. And I think that's as far as I could go," Gerstein said.

The research is based on data drawn from the large and ongoing Nurses' Health Study, a Boston-based study of nearly 117,000 women from 14 U.S. states. The women in the study are predominantly white, educated and professionals, which suggests findings from it may not be generalizable across women of various ethnic and socio-economic groups.

For this analysis, the authors used data from over 92,000 participants, 1,844 of whom went on to develop Type 2 diabetes.

After adjusting for the other known risk factors, the risk for a woman wearing a B cup was 1.3 times higher than if she wore an A cup. The increased risk for women wearing C cups and D cups was 1.7 and 1.6 respectively as compared to a woman who wore an A cup bra.

It's known that women who are overweight, especially those who carry excess weight around the middle of their torso, are at greater risk of developing Type 2 diabetes. And heavier women often have bigger breasts.

Does that mean this research is perhaps ascribing increased risk to larger breasts when in fact it is the woman's weight that elevates her chances of developing diabetes?

Ray didn't think so, saying there may be something about carrying more breast fat that influences development of diabetes.

"It isn't that it's just an equal marker (of diabetes risk)," he said in an interview. "But additively, above abdominal adiposity (fat), it might create a further adipose tissue area that could again further contribute to insulin resistance."