Inclusion Criteria:

- Ambulatory women (aged 60-75), with a new diagnosis of nonmetastatic,
hormone-receptor positive breast cancer, having undergone lumpectomy. They will not
need chemotherapy and will have been prescribed but not yet started anastrazole. All
will need a course of radiation therapy as part of usual care. Participants are
instructed not to change their physical activity or eating habits over the period of
the study.

Comparisons are:

- Identical to the cases except they are hormone-receptor negative and don't need
hormonal therapy.

- Healthy controls.

Exclusion Criteria:

- Nicotine usage

- Metastatic breast cancer

- Need for chemotherapy

- AI other than anastrazole

- Usage of steroids (equivalent of equal then or more than 7.5 mg prednisone x 3
months)

- Clinically significant abnormality of thyroid function

- Treatment with gonadal hormone replacement therapy within last 3 years

- Status post unilateral/bilateral surgical oophorectomy

- Having experienced a medical event, which may confound study outcomes [e.g. heart
attack, stroke, cancer (metastatic or newly diagnosed within last 5 years, except for
non-melanoma skin cancer and breast), lupus, rheumatoid arthritis, chronic
inflammatory disease]

- Medication-dependent diabetes mellitus or hypercholesterolemia.

- Gastric surgery

- Weight loss medication (prescription or over the counter)