Waist Size Linked to Breast Cancer, Study Finds

Trading in smaller skirt sizes for bigger ones is linked to a higher risk of breast cancer, finds a new study published in BMJ Open.

But it’s what underneath the skirt—an expanding waist—that counts.

Research already suggests that gaining weight puts women more at risk for breast cancer, since fat tissue spurs the production of estrogen, which feeds the growth of breast tumors. The kind of fat around your waist seems to be especially telling: Some studies have found that waist circumference is better than BMI at assessing the risk for many conditions. In an attempt to give women an “easy to understand message,” researchers of this new study measured waist thickness by the number on their subjects’ skirt tags.

The study looked at data from about 93,000 mostly overweight, postmenopausal women in the U.K. Collaborative Trial of Ovarian Cancer. After gathering various kinds of health data from the women—like general health, cancer status, and, yes, skirt size—for about three years, they analyzed the results.

An increase in skirt size was the single most predictive measure of breast cancer risk, the study concluded. When women went up a single skirt size over a 10-year span between their mid 20s and mid 60s, they were shown to have a 33% greater risk of developing breast cancer after menopause. Buying two skirt sizes up during that same period was linked to a 77% increased risk.

The size of your skirt might seem like a silly stand-in for measuring belly fat, but skirt size “has been shown to provide a reliable and feasible estimate of waist circumference at the population level,” the study reads.

Don’t get too married to the results, though. The study acknowledges that skirt sizing probably varied over the years, as any woman who’s ever shopped at more than one store can tell you. Forget changing skirt size in a decade—you can change skirt size in a minute if you just try a different store, so it should take more than a sudden switch from a 4 to a 6 to freak you out.