Effect of Exercise on Sex Hormones in Postmenopausal Women

Inclusion Criteria: * Ages 55-75 years at first group meeting * Physically able to undertake a moderate exercise program * Sedentary activity pattern (exercising \< 2 times/week for 20 minutes at a level to produce sweating) * Postmenopausal (not experiencing menstrual periods for the previous 12 months or FSH \>30 mIU/ml; for women who have had a hysterectomy, an FHS \>30 mIU/ml will classify them as postmenopausal) * Body Mass Index (BMI) greater than 25.0 * Able to follow directions and fill out questionnaires, and exercise diaries and logs in English * Agrees to be randomly assigned to either the exercise intervention or control group * Gives informed consent to participate in all screening and study activities * Able to come to the FHCRC for clinic visits and classes, to the UW Medical Center for CT scans, and to the UW NETT for measurements and instruction Exclusion Criteria: * Plans to leave Western Washington within the follow-up period * Using hormone replacement, tamoxifen, or oral contraceptives in past 6 months * Currently having severe hot flashes (that might prompt participant to start hormone replacement therapy before the end of study) * Current unstable thyroid disease or unstable dose of thyroid medications or TSH \>5.0 IU/ml or \<0.5 IU/ml * Invasive cancer in the past 10 years (except nonmelanotic skin cancer) * Any other endocrinologic abnormality * Breast, endometrial, ovarian, or melanoma cancer or carcinoma-in-situ at any time * Morbidly obese (BMI \> 40) * Current or planned use of corticosteroids * Currently on or planning to enter a structured weight loss program or to take diet drugs * Current use of certain other medications, such as any likely to interfere with adherence to an exercise program or likely to interfere with study outcomes * Moderate to high alcohol intake (more than 2 drinks per day) * Current smoker * Diabetes mellitus (fasting hyperglycemia) * Abnormal screening labs (hematocrit \< 32 or \> 48, white blood cells \< 3.0 or \> 15.0, potassium \< 3.5 or \> 5.0, fasting glucose \> 140, creatinine \> 2.0), or abnormalities on screening physical judged by study physicians to contraindicate participation in an exercise program * Contraindications for entry into a training program118 including: unstable angina, uncontrolled hypertension (systolic \> 200, diastolic \> 100), orthostatic hypotension (\> 20), moderate/severe aortic stenosis, uncontrolled arrhythmia, uncontrolled congestive heart failure, third degree heart block, pericarditis, myocarditis, pulmonary/systemic embolism within the past 6 months, thrombophlebitis, ST displacement \> 3 mm at rest, history of cardiac arrest) * Contraindications for exercise testing118 including: recent (within 6 months) cardiac event (MI, pulmonary edema, myocarditis, pericarditis), unstable angina, uncontrolled arrhythmia, third degree heart block, left bundle branch block, acute congestive failure, recent (within 6 months) pulmonary/systemic embolus, severe electrolyte abnormality * Meets criteria to stop screening exercise test118 as decided by overseeing physician (Dr. Schwartz or McTiernan) * volunteering in order to lose weight * alcohol or drug abuse, significant mental illness (as assessed by study staff impression)