Being overweight is associated with decreased risk of breast cancer before menopause and increased risk after menopause.
In a study published recently in PLOS Medicine, Wei Zheng, Ph.D., M.D., and colleagues investigate these contrasting associations.
They use data from 145,056 women, and a list of genetic variants found in genomic studies to be associated with BMI. Estimating each woman's BMI based strictly on genotype, the team found that genetically predicted high BMI was associated with a reduced risk of breast cancer in both premenopausal and postmenopausal women.
"It is likely that genetically predicted BMI may be more closely related to body weight in early life, which is negatively associated with breast cancer risk. Measured high BMI later in life may be influenced primarily by environmental factors that are associated with increased risk of breast cancer. For breast cancer prevention, the study provides evidence for lifestyle modification to reduce weight gain in adults," Zheng said.
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Guo, Y., Andersen, S. W., Shu, X. O., Michailidou, K., Bolla, M. K., Wang, Q., ... & Dunning, A. (2016). Genetically Predicted Body Mass Index and Breast Cancer Risk: Mendelian Randomization Analyses of Data from 145,000 Women of European Descent. PLoS Med, 13(8), e1002105.