A case-control study on breast cancer and body mass. The American Health Foundation--Division of Epidemiology.

A hospital-based case-control study was carried out to examine the effect of body weight/fat and physical activity on risk of breast cancer on 617 newly diagnosed breast cancer cases and 531 controls matched to the cases by age (+/- 5 years), race, year of interview (+/- 1 year) and hospital of admission. Breast cancer was not found to be associated with height, while being overweight appeared to be protective in premenopausal women [odds ratio, OR = 0.4 (0.2-0.7) for cases who weighted > or = 72.7 kg versus controls]. Increased body mass index (BMI) was protective in premenopausal women [OR = 0.4 (0.2-0.6) in breast cancer cases with BMI > or = 27 versus controls], but not in postmenopausal women, for whom it was a risk factor [OR = 1.5 (1.0-2.3)]. Few women reported any strenuous physical activity from ages 15 to 22 years (22% of premenopausal, 13% of postmenopausal women), and no significant effect on breast cancer risk was observed.