The purpose of this study is to determine if the phase of the menstrual cycle (opposed versus unopposed estrogen phase) affects eating behavior, including types of foods preferred, wanting/desire for specific foods, and perception of hunger.

This is an observational study to investigate the effect of endogenous estrogen (E2) and progesterone (P4) levels on eating behavior and energy-yielding nutrient metabolism. Eating behavior will be assessed during a complete menstrual cycle during the first month of the study. Participants will track the follicular and luteal phases of their menstrual cycle using urinary leuteinizing hormone (LH) kits, they will record information about their food intake, eating behaviors, and appetite in their home environments, and they will complete two laboratory test days: one test day scheduled during their follicular phase, and one test day scheduled during their luteal phase.

Inclusion Criteria:

• Body Mass Index between 20-30 Kg/m2
• regular menstrual cycles
• sedentary lifestyle (physical activity not more than 30 minutes per day three times a week)

Exclusion Criteria:

• Fasting blood sugar greater than 110 mg/dL
• Systolic Blood Pressure greater than 140 mmHg
• Diastolic Blood Pressure greater than 90 mmHg
• Fasting triglycerides greater than 120 mg/dL
• Documented or self-reported chronic disorders such as arthritis, or other inflammatory diseases
• Women who are Post-menopausal or Peri-menopausal
• Pre-menopausal women who are pregnant, uni/multiparous, taking oral contraceptives, or who have menstrual cycles lasting less than 20 days or greater than 45 days, polycystic ovary syndrome (PCOS), amenorrhea, eumenorrhoea, or polymenorrhoea.

Healthy, premenopausal women.