 1. Overweight or obese postmenopausal women with a history of biopsy-proven estrogen receptor positive andor progesterone receptor positive breast cancer and clinical evidence of metastatic disease. Overweight and obesity are defined by the WHO as a BMI of 25 - 29.9 and 30 kgm2 respectively. Postmenopausal status is defined by one of the following: a no spontaneous menses for over 1 year, in women 55 years; Continued in inclusion criterion 2. 