Inclusion Criteria:  Weight 45-75 kg Body fat 15-35 percent BMI 18-25 kg/m2 Nonsmoking <1 hour/week of purposeful aerobic exercise for the past 6 months Documentation of at least two ovulatory menstrual cycles during screening.  Exclusion Criteria:  History of serious medical conditions Medication use that would alter metabolic hormone levels Significant weight loss/gain (±2.3 kg) in the last year Current evidence of disordered eating or history of an eating disorder Taking exogenous hormonal contraceptives for the past 6 months