Body weight: estimation of risk for breast and endometrial cancers.

Consistent, positive, and independent associations between body weight or body mass index (BMI), weight gain, and various measures of central adiposity and the incidence of endometrial cancer exist. Increases in relative risks of 2-3.5 are reported for women with BMIs (in kg/m2) > or = 28-30, for women in the fourth compared with the first quartile of measures of central adiposity, and for women with weight gains from young adulthood to middle age of > or = 27 kg. Furthermore, endometrial cancer mortality is increased in heavier and taller women. Associations between breast cancer incidence and these measures of adiposity vary by age and menopausal status at the time of diagnosis. Heavier women appear to be at decreased risk for developing premenopausal breast cancer; relative risks of approximately 0.6 were reported for women with BMIs > or = 26-27. Conversely, heavier women are at increased risk of developing and dying from postmenopausal breast cancer. Although contradictory findings have been observed in cohort studies, modest increases in relative risks on the order of 1.2-1.5 were reported in older postmenopausal women with BMIs of > or = 28-30. Furthermore, adult weight gain and increased central adiposity have been consistently and independently associated with an increased risk for postmenopausal breast cancer. No significant associations have been observed between weight loss and postmenopausal breast cancer incidence. These findings indicate that avoidance of weight gain and accumulation of central body fat during adult life may reduce risk of both endometrial and postmenopausal breast cancer.