Recent studies have constantly related higher BMI to increased breast cancer risk in postmenopausal women. This association has been assumed to be due to peripheral conversion of estrogen precursors to estrogen in the excess adipose tissue . This mechanism is supported by a secondary analysis of the Women's Health Initiative trial evaluating postmenopausal women with normal BMIs.
The trial showed that women with the highest quartile for body fat had an increased risk for breast cancer compared with those in the lowest quartile ( hazard ratio 1.9 ). Source: Journal Of Cancer Epidemiology
