Clinical Research Directory

Inclusion Criteria: * Body Mass Index (BMI) at least 18 but less than 25 kg/m2 * No history of chronic disease affecting hormone production, metabolism, or clearance * No use of medications known to alter or interact with reproductive hormones or insulin metabolism (e.g. thiazolidinediones, metformin) * No use of reproductive hormones within 3 months of enrollment * Normal prolactin and thyroid stimulating hormone levels at screening * History of regular menstrual cycles every 25-35 days * Use of a reliable method of contraception (female or male partner sterilization; intra uterine device (IUD); abstinence; diaphragm) * Normal hemoglobin A1c * Screening hemoglobin \>11gm/dl Exclusion Criteria: * Women with a baseline dietary assessment indicative of \>35% daily calorie consumption from fat (as calculated based upon initial screening survey) will be excluded, as the impact of increasing their dietary fat intake may be minimal. * Women with fasting triglycerides \>300mg/dl at screening will be excluded, as they might be at risk for acute elevation of triglycerides and even pancreatitis if placed on a high fat diet * Inability to comply with the protocol. Individuals who travel frequently, or who eat most of their meals outside of their home will be excluded, as it will be difficult to impossible for them to comply with the diet, to pick up the food cartons, etc. * Because high proportions of dairy fat will be needed to attain 48% calories from fat in the diet, vegans and lactose intolerant individuals will be excluded. * Pregnant women or women planning to become pregnant will be excluded.