A 3-arm randomized controlled trial will be conducted, the goal of which is to determine which group represents the most viable approach to behavioral weight loss treatment with 18-25 year olds. A total of 381 participants,18-25 years of age, with a BMI between 25 and 45 kg/m2 will be randomized to one of three groups: 1) Behavioral Weight Loss (BWL), 2) BWL + Autonomous Motivation (BWL+Aut) or 3) BWL + Extrinsic Motivation (BWL+Ext). All arms will receive a 24-week behavioral weight loss intervention, including personalized dietary, physical activity, and weight loss prescriptions. In addition, all arms will be followed for a 6 month no treatment follow-up period. Assessments of weight and secondary outcomes will occur in 0, 3, 6 and 12 months. The investigators will compare treatment effects, across all 3 arms at 6 months, and compare arms on weight loss maintenance at12 months. The investigators will also examine mediators of treatment outcomes consistent with the investigators theoretical framework.