PROJECT ABSTRACT Metabolic and bariatric surgery (MBS) is a safe and medically effective treatment choice for severe obesity. Yet, despite (1) an increase in the number of MBS procedures performed in the United States annually, and (2) the fact that many people express interest in MBS, only about 50% of referred or eligible persons for MBS actually undergo the procedure. Furthermore, studies have documented Hispanics and non-Hispanic Blacks (NHB) are significantly less likely than non-Hispanic Whites (NHW) to complete MBS despite higher rates of both severe obesity and obesity-related comorbidities (e.g. type 2 diabetes, heart disease, cancer). Reasons for the ethnic group disparities in post-MBS weight loss and comorbidity resolution are largely unknown; therefore, the following aims are being conducted: AIM 1. Identify the socioecological characteristics associated with the following four patient-determined MBS groups: (1) early-completers of MBS (< 3 months), (2) later-completers of MBS (>3 months but within 12-15 months), (3) non-completers of MBS because surgery was electively cancelled after being scheduled; and (4) non-completers due to no interest in MBS after receiving a medical referral. AIM 2. Determine how differences in Groups 1 and 2 relate to post-operative weight loss and comorbidity resolution at 6- 12- and 24-months post- MBS. AIM 3. Explore the mediating and moderating effect of ethnicity, intrapersonal, interpersonal, clinical, and other environmental interactions on MBS commitment group differences. For this administrative supplement we are proposing over 1 year to (1) enhance our current parent study with two additional sub-projects, the first one led by our current postdoc fellow (Dr. Elisa Morales- Marroquín) titled Role of MBS and Ethnicity on the Relationship Between the Blood and Gut Microbiotas and the second led by our clinical collaborator (Dr. Jaime Almandoz) titled An In-Depth Exploration of the Impact of Weight Stigma and Bias on MBS Completion and Post-MBS Weight Loss in Ethnically Diverse Patients, each with their own set of specific aims; (2) add two additional graduate research assistant training slots from DEIA backgrounds to assist Drs. Morales Marroquín and Almandoz with their projects; (3) enhance the current mentoring infrastructure to expand our Summer Scholars Program for undergraduates; and (4) use the parent R01 as an example of successful team science. These goals will reach trainees at the faculty, postdoc, graduate, and undergraduate training level and will promote peer-to-peer mentoring through all levels, led by the parent grant Principal Investigator. In summary, the parent award has produced impactful work to date that is informing clinical care for MBS patients in post-pandemic recovery efforts. Our parent grant provides an excellent example of how team, interdisciplinary science, and scientists representing epidemiology, surgery, psychiatry, endocrinology, and obesity medicine can successfull...