Obesity is considered a risk factor for breast cancer. Modifying life styles that reduce obesity offers the potential for prevention and improved outcomes from cancer. The effects of obesity and breast cancer among African‐American women and Hispanic women have been explored in a limited number of studies. The objective of the current study was to investigate the association of obesity with breast cancer in a minority cohort.

This was a cross‐sectional study of 471 African‐American and Hispanic women with and without breast cancer in South Los Angeles. Data regarding body mass index (BMI) and clinical factors were obtained by medical record abstraction. Data were assessed using logistic regression with multivariate analysis. Kaplan‐Meier survival analysis was used to assess disease‐free survival.

Women with breast cancer were more likely to be obese (BMI >30 kg/m²) than women without breast cancer (odds ratio [OR], 2.0; P = .01). There was a significant association of being overweight or obese and breast cancer among postmenopausal women (OR, 2.3 [P = .03] and 2.9 [P < .01], respectively). The association between obesity and breast cancer was significant only among African‐American women (OR, 2.70; P < .01) and was especially significant among postmenopausal African‐American women (OR, 4.8; P < .01). There was a borderline significant association between obesity and later disease stage at diagnosis (P = .06). An association also was observed between higher BMI (for cutoff points of both 30 kg/m² and 28 kg/m²) and poorer disease‐free survival (P = .045 and P = .019, respectively).

The current data suggested an association between obesity and breast cancer, especially among postmenopausal women and most significantly in the African‐American cohort. Cancer 2011. © 2011 American Cancer Society.