Inclusion Criteria:

• 40 postmenopausal women (age 40-62) and 30 men (age 18-45) will be recruited if they are healthy, at their lifetime maximal weight, have been weight stable for at least six months prior to entry, have a BMI between 19 and 39.9 kg/m2, and be willing to commit to not making significant changes to their diet or daily activities while enrolled in the study.

Exclusion Criteria:

• Subjects will be excluded for potential confounders on body weight, cortisol production rates, sex steroid metabolism, or contraindications to strong magnetic fields:

  1. Age less than 18 to exclude those who might be experiencing alterations in cortisol production or weight as a result of adolescent growth
  2. Subjects who exercise > 30 minutes/day, 3 times a week
  3. Smokers
  4. Heavy alcohol drinkers (> 2 drinks/ day)
  5. Subjects with medical diagnosis including diabetes, heart disease, and cancer
  6. Subjects with psychiatric illness (i.e., depression, psychosis, bipolar, schizophrenia; or are taking medications for these disorders)
  7. BMI 40 kg/m2, since obesity influences levels of sex steroids and sex hormone binding globulin; or body weight > 136 kg (300 lbs), since this is the weight limit for the DEXA and MR machines
  8. Presence of metal in the body such as body piercing, shrapnel, cardiac pacemakers or aneurysm clips
  9. Endocrine diseases affecting body composition, such as untreated hypothyroidism or Cushing's syndrome, will be excluded by history and physical examination, or by laboratory evaluation if necessary.
• Women with a contraindication to estrogen use will also be excluded, including: an estrogen dependent malignancy, active thrombophlebitis, history of deep venous thrombosis, hypertriglyceridemia, untreated hypertension, cardiovascular disease, migraine headaches, or current tobacco use.
• Women with frequent hot flashes or disrupted sleep will also be excluded since they will be unlikely to tolerate randomization to placebo and continued symptoms and altered sleep cycles will independently affect cortisol secretion patterns.
• All volunteers will have had a normal mammogram within the previous 12 months.
• Any subject with previously unevaluated postmenopausal bleeding will not be included and, instead, will be referred to a physician for evaluation.
• Women who underwent surgical menopause (bilateral ovariectomy) must be at least one year out from their surgery before considered eligible so as to allow weight stabilization after the procedure.
• Men will have had a prostate exam by their primary health provider within the previous year or by the PI at the time of screening for this study.
• Any subjects taking a blood thinning medication or with an abnormal exam will not be included and, instead, will be referred to a physician for evaluation