A study in the journal Breast Cancer Research has found that women with a mutation in the BRCA1 gene - the gene that predisposes women to breast cancer - are 65 percent less likely to develop the disease if they lose weight between 18 and 30 years of age.
The multi-institute study, led by Steven Narod from the University of Toronto, suggests that young women with the BRCA1 genetic predisposition should avoid putting on weight in early adulthood, especially if they plan to have children.
The study involved two groups of women, all of whom had a mutation in one of the breast cancer susceptibility genes BRCA1 and BRCA2. The first group had been diagnosed with breast cancer while the second group had not. Each member of the first group was paired up, or 'matched', with a woman from the second group who was the same age, carried a mutation in the same gene and lived in the same country. By comparing the two groups, the researchers could identify the relationship between the incidence of pre-menopausal breast cancer and weight at 18, 30 and 40 years of age.
The researchers said that, for women who have a mutation in BRCA1, "weight loss of at least 10 pounds was associated with a 65 percent reduction in cancer risk between the ages of 30 and 40." Interestingly, the study also showed that BRCA1 mutation carriers who gained 10 pounds or more between 18 and 30 years of age were 44 percent more at risk of developing breast cancer if they have 2 children or more.
There was no association found between weight loss and breast cancer risk in carriers of the BRCA2 mutation.
