Timing of weight gain and breast cancer risk.

BACKGROUND: Obesity and body-fat distribution have been associated with the incidence of breast and endometrial cancers. It may be critical to determine if the timing of weight gain during periods of hormonal change, such as menarche, pregnancy, or menopause, has different biologic effects, especially secondary to differences in the localization of body fat during these periods. The objective of the current study was to determine if excess weight in any particular decade of life or the timing of weight gain was more significant relative to breast cancer risk.
METHODS: Anthropometric, medical, and hormonal histories were obtained from 218 consecutively recruited, newly diagnosed patients with breast cancer admitted to the H. Lee Moffitt Cancer Center and Research Institute (Tampa, FL) and 436 control subjects, matched in a two to one ratio for age and menopausal status.
RESULTS: A weight gain of 15 pounds or more was observed for 63.8% of the patients compared with 49.3% control subjects (P = 0.0006) from age 30 to current age. Similarly, more than 48% of cases gained more than 15 pounds from ages 16 to 30 compared with 37% (P = 0.01) of the control population. Although weight gain from age 16 to adulthood was significantly higher in patients with breast cancer at each decade when compared with control subjects, a significant and independent association between weight at age 30 (P < 0.0001) and risk of breast cancer was noted.
CONCLUSION: Women who progressively gain weight from puberty to adulthood, and specifically in the third decade of life, should be considered at a higher risk for developing breast cancer.