Comprehensive lifestyle interventions are recommended for the treatment of adolescent obesity; however, evidence suggests that they are not as effective in teens as they are in children and adults. Recent evidence supports that shifting the timing of energy intake earlier in the day has led to improved weight loss outcomes among adults with overweight and obesity. Given that adolescents traditionally consume the majority of their daily energy intake late in the day (past 5PM), this approach may improve the effectiveness of traditional behavioral weight control interventions in teens. Therefore, the primary aim of the proposed research is to pilot a novel adaptation of an evidence-based adolescent weight control intervention in which adolescents will be randomized to consume the majority of their daily energy needs earlier versus later in the day. More specifically, 40 adolescents, ages 13-17, with obesity (BMI>95% for age and sex) will be randomized to a 16-week evidence-based weight control intervention that has the participant consume >50 percent of their total energy intake before 3PM (i.e. at breakfast / lunch; BFL) or after 3PM (i.e. dinner; DIN). Assessments will take place at baseline and 16 weeks (post-treatment). The proposed study will test 1) the adherence and feasibility of the BFL vs. DIN interventions as measured by the average number of days on which daily energy was consumed in accordance with the prescribed eating plan and, secondarily, mean session attendance, 2) if the BFL group will have significantly greater reductions in BMI post-treatment as compared to the DIN group, 3) if there are differences in sleep duration and quality between groups, and finally, as an exploratory aim, whether there are differences in dietary quality between groups. The proposed research is significant, as it addresses obesity in teens. It is innovative as the timing of meals and snacks have not been manipulated in adolescents in the context of behavioral weight control. Moreover, the study will shed light on whether doing so improves sleep and could help to untangle how sleep and weight gain relate in adolescents.

Inclusion Criteria:

• Age 13- 17 years
• BMI > 85th percentile for age and sex
• Ability to speak, read and write English due to the group format of the intervention
• A caregiver who is willing to participate in four separate parent groups with a facilitator
• Agreement to study participation and random assignment.

Exclusion Criteria:

• Current involvement in another weight loss program or has lost 10 pounds in the six months prior to enrollment
• Medical condition that interferes with the prescribed dietary plan or participation in physical activity (e.g. cardiovascular disease, type 1 or 2 diabetes mellitus, or pregnancy)
• In treatment for or are diagnosed with a major psychiatric disorder, including an eating disorder, at the time of screening
• Taking medications that promote weight gain.