This study aims to address a critical gap in pediatric oncology survivorship care by exploring innovative solutions to addressing obesity and its comorbidities in pediatric cancer survivors. The majority (99%) of pediatric cancer survivors will develop severe chronic health conditions by age 50, with 96% developing at least one severe/disabling, life threating or fatal chronic health condition. Obesity, cardiovascular, and metabolic diseases are the most common treatment-related late effects among pediatric cancer survivors. Improving diet and reducing obesity has the potential to dramatically improve the quality of life and long-term health of pediatric cancer survivors. Utilization of a prebiotic fiber supplement along with TRE amy improve the gut microbiome, short-chain fatty acid synthesis, and hunger hormones to further improve weight loss with TRE and a greater decrease in cardiometabolic risk. The aims of this study are to test the safety, feasibility, and acceptability of 8-h TRE or 8-h TRE with a fiber supplement among young adult (YA) pediatric cancer survivors. The investigators further strive to examine the preliminary efficacy of TRE on body weight, body composition, glucose regulation, and cardiovascular risk markers. Data obtained will be used to inform a larger efficacy trial of TRE among adolescent and young adult pediatric cancer survivors. Given that a majority of pediatric cancer survivors will develop severe chronic health conditions by age 50, with 96% developing at least one severe/disabling, life threating or fatal chronic health condition exploring accessible nutritional strategies to improve long term health trajectory of 70,000+ AYA diagnosed with cancer each year in the United States. This study of TRE will provide important preliminary evidence of the benefits of this nutrition therapy for YA pediatric cancer survivors. The long-term goal of this line of inquiry is to improve both short and long-term outcomes for YA pediatric cancer survivors.

Inclusion Criteria:

• Age 18-39 years old at time of consent
• Completed anti-tumor treatment for pediatric cancer
• BMI 25-39.99 kg/m2
• Able to provide (self or guardian) written informed consent and HIPAA authorization for release of personal health information, via an approved UIC Institutional Review Board (IRB) informed consent form and HIPAA authorization.
• As determined at the discretion of the enrolling physician or protocol designee, ability of the subject to understand and comply with study procedures for the entire length of the study.

Exclusion Criteria:

Subjects meeting any of the criteria below may not participate in the study:

• Individuals <18 or >39 years of age
• Individuals on glucoregulatory medication
• Individuals with BMI ≥ 40kg/m2 and < 25kg/m2
• Individuals who are pregnant, trying to become pregnant or breast feeding. A negative serum or urine pregnancy test is required per institutional practice guidelines at screening as well as prior to all DXA scans.
• Shift workers who maintain a work schedule that crosses 12:00 am > 1 day per week
• Individuals with a history of eating disorders
• Active infection requiring systemic therapy
• Uncontrolled HIV/AIDS or active viral hepatitis
• Any mental or medical condition that prevents the patient from giving informed consent or participating in the trial.
• Other major comorbidity, as determined by study PI
• Illicit drug use (excluding self-reported marijuana) or excessive use of alcohol (i.e., > 2 drinks/day)
• Currently participating in Weight Watcher's or another weight loss program with a ≥ 3% weight loss in three months prior to recruitment
• History of: Myocardial infarction, Stroke, Congestive heart failure, Chronic hepatitis, Cirrhosis, Chronic pancreatitis
• History of solid organ transplantation
• Individual does not have access to the Internet
• Individuals who have taken antibiotics < 2 months prior to the initiation of the study
• Individuals who regularly use (≥ 3 times per week) prebiotics, probiotics, synbiotics, prebiotic supplements or laxatives within the past month