From the AIOM Guidelines 2018 NEOPLASES OF THE MAMMELLA (p. 167)

With regard to women with BRCA mutations in particular, the impact of lifestyle and diet on the risk of breast cancer has been evaluated in some studies. and diet on the risk of breast cancer has been evaluated in some studies. In fact, total caloric intake and overweight in adulthood correlate with an increased risk of breast cancer60 . breast cancer60

An inverse correlation between healthy diet and breast cancer risk has been demonstrated, and physical activity during adolescence appears to be associated with a reduced risk of breast cancer.
A case-control study in families with breast and ovarian cancer showed that elevated serum IGF-1 levels are associated with increased BRCA gene penetrance. Therefore, a randomised controlled trial in BRCA mutated women was initiated to evaluate the effects of diet and physical activity on reducing IGF-1 levels.