Current studies have shown that fast weight gain may be more important than body mass index on the incidence of breast cancer. The aim of this study was to evaluate the association between body weight and breast cancer.

This was a case-control study nested in a cohort of a breast cancer mammography screening program in Southern Brazil. A trained investigator administered a standardized interview to collect sociodemographic and clinical data, and body weight history (weight at menarche, at marriage, at first and last pregnancy, and at menopause). Current anthropometric measurements were also made.

Fifty-seven women with cancer (66.7% postmenopausal) and 159 controls were included. Current age (60.3 ± 10.4 vs. 55.8 ± 8.4 years, P < .01), marital status (49.1% vs. 64.8% with a partner, P = .03), and physical activity (48.2% vs. 32.3% sedentary, P = .01) were significantly different between cases and controls, respectively. Odds ratio showed that age and current waist circumference were associated with postmenopausal cancer. No difference was found in relation to body weight at different stages of life.

Women with social vulnerability recruited at a mammography screening program in Southern Brazil showed a large weight gain during life, but no significant differences were found in body weight between women with or without breast cancer.