Study Objective An intensive lifestyle modification intervention (which includes caloric restriction, use of an over-the-counter weight loss medication, and moderate physical activity with tracking) designed to promote a weight loss of approximately 7% of initial body weight is more likely to achieve a good perinatal outcome (i.e. a healthy term normal weight infant) than a recommendation to standard lifestyle modification with moderate physical activity with tracking (based on publically available activity recommendations) in obese women with unexplained infertility.

Patient Population The population will consist of 380 obese women with unexplained infertility, age 18-40 years old. Subjects must have normal ovulatory function and normal ovarian reserve. Additionally, the couple will have no other major infertility factor: the subject will have at least one patent fallopian tube and a normal uterine cavity, and a partner total motile sperm count of at least 5 million in at least one ejaculate.

Study Design This will be a two-arm, multicenter, prospective, randomized clinical trial of a lifestyle modification program with tracked increased physical activity and weight loss (intensive) compared to recommendations to tracking of increased physical activity alone with weight maintenance (standard) in women with obesity and unexplained infertility. This 16 week period of lifestyle modification will be followed by an open label empiric infertility treatment regimen consisting of three cycles of ovarian stimulation with oral medication (clomiphene citrate (CC)), triggering of ovulation with human chorionic gonadotropin (hCG) and intrauterine insemination (IUI).

Treatment The intensive lifestyle modification intervention will consist of caloric restriction (consumption of approximately 1200-1500 kcal/d), use of an over-the-counter weight loss medication (Alli, which is brand name Orlistat, a gastric lipase inhibitor that limits gut fat absorption), and moderate physical activity (goal of reaching 10,000 steps a day). The pretreatment intervention will last 16 weeks and is designed to promote a weight loss of approximately 7% of total body weight. Women in the standard lifestyle intervention (standard) will receive publicly available written materials that promote engagement in moderate physical activity with target of 10,000 steps a day. Detailed instruction of physical activity will not be provided. Participants in both groups will receive activity tracking devices (Fitbit Wireless Activity Tracker) and wireless scales (Fitbit Aria Wireless Activity Scale) to promote adherence to the inventions and to allow monitoring for compliance by study personnel. The pretreatment intervention will last 16 weeks. Both groups will aim for activity levels of 10,000 steps/day, with a recommendation to increase steps from baseline by 500 steps/per week. The investigators will monitor subjects monthly during this preconception intervention. After 16 weeks of lifestyle modification, all subjects randomized will receive a standardized empiric infertility treatment, regardless of adherence or success in achieving treatment goals. This treatment will consist of ovarian stimulation with CC followed by ultrasound follicular monitoring, hCG trigger of ovulation, and a single partner intrauterine insemination (IUI) per treatment cycle for up to three treatment cycles. The goal for both treatment groups will be to maintain levels of physical activity and weight achieved during the pretreatment phase during the empiric infertility treatment phase. Subjects who conceive will be followed throughout pregnancy with the wireless activity monitor and wireless scale. Additionally there will be three brief onsite visits during pregnancy (per trimester at 16, 24, and 32 weeks) for onsite determination of weight, glycemic, and blood pressure changes and collection of biospecimens. All pregnancy outcomes will be tracked. Subjects who deliver will be encouraged to donate placenta and cord blood to the study repository and then to enroll in our Pregnancy Registry for continued infant follow-up. The investigators will also expand the number and variety of specimens that are collected for the repository from both partners including urine and serum, semen, saliva, placenta and cord blood.