We will conduct an intensive validation substudy with a randomly selected 15% of participants (n = 60). We plan to assess the validity of self-reported caloric intake with doubly labeled water, and the validity of self-reported activity levels with tri-axial accelerometers. We will also measure resting metabolic rate using a ventilated hood. For each of the 2 academic quarters that we recruit participants during each of the 3 proposed recruitment years, 10 participants will be randomly selected to provide intensive data during the last 2 weeks of the interventions because this should be the period during which there is maximal difference between participants in the two conditions in terms of caloric intake and physical activity. Participants in the validity sub-study will complete all assessments in the University of Oregon's human physiology lab. Assessments will be carried out by trained human physiology staff. Participants will complete pregnancy tests prior to participating in the validity substudy. Pregnant participants will not be able to complete the validity substudy as an extra precaution against any risk to the fetus that may be posed by the doubly labeled water procedure. No risks to fetuses or pregnant women from doubly labeled water have been identified at this point in time. Participants in this substudy will complete a 4-hour assessment within 2 days after the second intervention session (week 2) and will complete another 2-hour assessment within 2 days after the fourth intervention session. Participants will be offered an additional $80 for coming to the lab for the first 4-hour assessment and $100 for coming to the lab for the second 2-hour assessment.