In a cohort study involving young and middle-aged women, researchers found that a larger bra cup size at age 20 predicted the onset of type 2 diabetes. Bra cup size, a simple, easily ascertained measure, explained the association beyond the well-established measure of BMI. – Elevated waist circumference and body mass index (BMI), both traditional measures of obesity, are accepted risk factors for type 2 diabetes mellitus. Girls who are obese experience earlier onset of puberty and possibly greater breast development. Young women with a larger bra cup size may be at higher risk of diabetes in adulthood, says a new study led by St. Michael’s Hospital physician Joel Ray.