To find the effectiveness of a diet plan (Time Limited Eating or TLE) on glycemic control, B-cell function, body fat, and body mass index (BMI) in adolescents with type 2 diabetes.

Intervention Design This is a prospective, pilot randomized controlled trial testing the efficacy of time-limited eating (TLE) on glycemic control, β-cell function, and body composition among predominantly Latinx adolescents with T2D compared to a prolonged eating period (12+hours). One-hundred adolescents with T2D will be recruited from CHLA. All participants will receive standard nutritional counseling and will be randomized to one of two meal-timing schedules to be followed for 12 weeks: (1) Control: 12-hour or more eating window without mealtime restrictions and (2) TLE: 8-hour eating period (16 hours of daily fasting).

The implementation steps of the proposed RCT are as follows:

1. The staff will introduce the study to all eligible participants either in person or virtually and consent interested families for the study.
2. All participants and their families will complete baseline study surveys in REDcap.
3. All participants and their families will receive training on the use and application of the Dexcom G6 CGM, which is FDA approved in patients 2 years and older. All equipment required for the duration of the study will be distributed to the participants in-person. Participants will receive enough sensors to wear the CGM daily for the entire study period. Participants will be instructed to change their sensor every 10 days with the assistance of the study staff. Each participant will be asked to download the CGM app onto their personal smartphone and set up an account with a pseudonym.
4. All participants and their families will receive standard nutritional counseling and be randomized to one of two meal-timing schedules to be followed for 12 weeks: (1) Control: >12-hour eating or (2) TLE (8-hr eating period/16-hr of daily fasting). During the eating window, participants will not be required to count calories or monitor their food intake. Participants will choose and pay for their own food during the intervention. All participants will record their eating window daily and submit it to the study staff via REDcap. All participants will receive standard recommendations for physical activity, screen, and sleep time as per the American Academy of Pediatrics age appropriate recommendations at the first visit140.
5. The study staff will perform weekly phone encounters with the participants to assess barriers to adherence and review the CGM data. If a barrier is identified the study staff will create a solution plan to promote adherence and retention. The study staff will record any medication changes or health issues that have occurred in the last 7 days. To foster treatment adherence, participants will receive weekly calls from the study staff for the duration of the trial. Counseling will be conducted by trained research staff. The sessions will serve three purposes: (1) foster adherence, retention, and accountability; (2) troubleshoot intervention barriers; and (3) monitor safety endpoints. During the sessions, participants will be provided with the support, knowledge, skills, and resources they need to successfully adhere to the protocol. The research staff will analyze the adherence data and progress using multiple-pass methodology. To support participants, the staff will use behavioral techniques, such as stimulus control, goal setting, behavioral contracting, and motivational interviewing. In addition, the staff will assist participants in troubleshooting any adherence issues and give participants additional encouragement and support when adherence problems arise. If a participant adheres to meal timing protocol < 4 days/week, a follow-up call or videoconference will be scheduled to address challenges and to counsel participants. Furthermore, In order to reduce participant burden, if at all possible study procedures will be scheduled to coincide with participants' scheduled clinical visits.

(7) To further inform future trials and scalability we will continuously collect recruitment, consent, and retention rates, and barriers to engagement.

(8) Adverse Event Monitoring will be monitored. If at any time, the study staff notices any unhealthy compensatory behaviors the PI will be notified and a treatment plan will be created to ensure that the participant receive the appropriate screening, work-up, and diagnosis from their primary care provider and are withdrawn from the study if appropriate.

(9) The PI and research team will meet bi-weekly to monitor all study procedures and oversee data management and analysis.

All adolescents with T2D and referred to the endocrinology clinic at CHLA will be screened. Inclusion criteria are: (1) age 12-21 years; (2) Tanner stage III and above; (3) diagnosis of T2D based on the ADA diagnostic guidelines; (4) hemoglobin A1c < 9%; and (5) participant must be willing and able to adhere to the assessments, visit schedules, and eating/fasting periods. To limit confounding factors, individuals will be considered ineligible to participate if they meet any of the following exclusion criteria: (1) previous diagnosis of Prader-Willi Syndrome, brain tumor or hypothalamic obesity; (2) serious developmental or intellectual disability; (3) previous diagnosis or subthreshold symptoms of an eating disorder (anorexia nervosa, bulimia nervosa, binge-eating disorder); (4) parent/guardian-reported physical, mental of other inability to participate in the assessments (e.g., inability to wear CGM, inability to undergo imaging testing without sedation); (5) previous or planned bariatric surgery; (6) current planned use of an anti-obesity or other diabetes medication (e.g., phentermine, topiramate, orlistat, glucagon-like-peptide-1 agonist, naltrexone, or bupropion); or (7) current participation in other interventional weight loss studies.