Dietary fat intake has little to do with breast density; however, it does relate to increased body mass index (BMI). BMI is a measure of body fat based on height and weight, and there is more fatty breast tissue in women with higher BMI. Higher BMI reduces the percent of density but might not reduce the total amount of dense tissue. BMI and breast density are both separate risk factors for breast cancer. Before menopause, low BMI [1, 2] increases the risk of breast cancer. After menopause, weight gain and increasing BMI increase the risk of breast cancer.
1. van den Brandt PA, Spiegelman D, Yaun SS, et al. Pooled analysis of prospective cohort studies on height, weight, and breast cancer risk. Am J Epidemiol 2000; 152:514-527
2. Huo CW, Chew GL, Britt KL, et al. Mammographic density-a review on the current understanding of its association with breast cancer. Breast Cancer Res Treat 2014; 144:479-502