This subproject is one of many research subprojects utilizing the resources provided by a Center grant funded by NIH/NCRR. The subproject and investigator (PI) may have received primary funding from another NIH source, and thus could be represented in other CRISP entries. The institution listed is for the Center, which is not necessarily the institution for the investigator. This grant explores the effect of oral contraceptives on body weight control in adulthood. Many women stop taking oral contraceptives because they are concerned about a perceived side effect, weight gain. But this failure to consistently take oral contraceptives leads to increased rates of unintended pregnancy. Surprisingly, studies in animals (mice, rats, cats, dogs, monkeys) have shown that estrogen and progesterone administration to ovariectomized animals generally leads to weight loss, rather than weight gain. The overall goal of this grant is to document changes in body weight when ovary-intact primates are chronically given oral contraceptives for a one-year period of time. We hypothesize that monkeys taking oral contraceptives for a year with not experience weight gain, but may in fact experience a mild weight loss;a finding which would discredit the perceived side effect of oral contraceptives in causing weight gain.