Continuous Wearable Biometric Monitoring in Adults Undergoing Obesity Treatment (SMART-BMI)

This study addresses a specific gap in the evidence for consumer wearable devices in obesity care. Prior trials that supplied wearable devices without integrating the resulting data into clinical decision-making have generally not improved weight outcomes. This trial is therefore designed to test not the device in isolation, but whether care teams acting on continuous biometric data achieve better outcomes than standard care.

The trial uses a two-phase adaptive design at a single academic medical center. Two treatment cohorts are enrolled in parallel throughout: adults undergoing metabolic and bariatric surgery, and adults initiating GLP-1 receptor agonist therapy. All participants are followed for 52 weeks.

Phase 1 is a single-arm observational feasibility phase. Every participant receives an Oura Ring, and the existing clinical team (dietitians, nurse practitioners, physicians, and coordinators) can view the biometric data through a dashboard during routine care. No dedicated coach and no additional study visits are added. Phase 1 validates the end-to-end data pipeline, characterizes device wear adherence and data completeness, and estimates the variability of candidate outcomes to inform Phase 2 sizing. As a pre-specified exploratory analysis, observed Phase 1 outcomes are compared against historical electronic health record-based controls within each treatment cohort; this comparison is descriptive and hypothesis-generating rather than a formal test of efficacy.

Phase 1 data will be reviewed for feasibility, safety, and outcomes, including the exploratory comparison against historical controls, before Phase 2 is activated. Phase 2 proceeds only if Phase 1 demonstrates adequate feasibility and a directional signal that biometric-informed care may improve outcomes; absent any such signal relative to historical controls, Phase 2 will not be activated. Phase 1 results are analyzed and reported regardless of whether Phase 2 proceeds.

Phase 2 is a randomized controlled trial with 1:1 parallel allocation. Phase 2 will also have a health coach-in-both-arms design: every Phase 2 participant receives a study-funded health coach. In the intervention arm, the care team can view the participant's Oura dashboard and incorporates the biometric data into management and coaching. In the control arm, the coach delivers a standardized behavioral curriculum without access to any wearable data. Because both arms receive equivalent coach contact, the design isolates the specific contribution of the biometric information rather than the added attention of a coach, removing attention bias as an explanation for any observed difference.

The study is open label, as participants and coaches are necessarily aware of arm assignment. The primary outcome is drawn objectively from electronic health record data, which limits the influence of unmasked assessment.

Sample size follows an adaptive approach. The maximum enrollment reflects an adaptive upper bound, and Phase 1 estimates allow re-estimation of the Phase 2 sample size at the interim review.

The primary analysis follows a modified intention-to-treat approach, applying a pre-specified biometric data-quality threshold symmetrically across both arms. Between-arm comparison of the primary continuous outcome uses analysis of covariance adjusting for the baseline value.

The wearable data are generated by a commercially available consumer device used consistent with its general wellness purpose; no investigational device exemption applies. The sponsor supplies devices and device-use guidance and reviews manuscripts within a pre-specified window, but holds no authority over data analysis, interpretation, or the decision to publish. The principal investigator retains scientific and publication independence.

Inclusion criteria

• Age 18 years or older and under 65 years
• Diagnosis of obesity (BMI 27 kg/m² or greater), or meeting clinical criteria for bariatric surgery per standard of care at UCSD Health
• Actively receiving or planning to receive care through UCSD Health Bariatric and Metabolic Institute or Obesity Medicine clinics
• Able to provide written informed consent
• Owns or has access to a smartphone compatible with the Oura application (iOS 15 or higher, or Android 9 or higher)
• Agrees to follow the study's lifestyle considerations throughout the study
• Willing to wear the Oura Ring per manufacturer-recommended wear guidelines for the study duration (Phase 1: all participants; Phase 2: intervention arm only)
• For Phase 2: willing to be randomly assigned to either the wearable monitoring plus coaching arm or the coaching-only arm
• Bariatric Surgery Cohort: scheduled for bariatric surgery (sleeve gastrectomy or Roux-en-Y gastric bypass) at UCSD Health within the enrollment window, with surgery planned at least 30 days after consent to allow a baseline monitoring period
• GLP-1 Initiation Cohort: planned start of incretin-based medication (GLP-1 receptor agonist or dual GLP-1/GIP agonist) as part of routine clinical care
• Ability to speak English or Spanish

Exclusion criteria

• Any contraindication to wearing the Oura Ring per current manufacturer labeling and safety guidelines
• Implanted cardiac device, pacemaker, implantable cardioverter-defibrillator, or neurostimulator
• Severe heart disease (such as severe heart failure or unstable coronary artery disease) or end-stage lung disease, as determined by the site PI
• Known cardiac arrhythmia, or use of any cardiac medication (such as a beta-blocker) that in the PI's opinion would interfere with the quality of Oura-derived heart rate or heart rate variability data
• Severe gastroparesis
• Previous bariatric procedure at any time (bariatric surgery cohort only)
• Endocrine or metabolic condition that would make weight loss clinically complicated or difficult to achieve, at the discretion of the study team (such as uncontrolled hypothyroidism, chronic glucocorticoid use, or a genetic condition unresponsive to standard treatment)
• Portal hypertension or cirrhosis
• Chronic kidney disease Stage IV or greater, or on dialysis
• Chronic pancreatitis
• Significant and uncontrolled inflammatory bowel disease
• Diagnosed sleep disorder that would substantially impair the validity of wearable-derived sleep measurements (such as severe untreated obstructive sleep apnea or severe insomnia)
• Active cancer treatment within the past 12 months
• History of solid organ transplant, or currently receiving dialysis
• Inability to tolerate general anesthesia (bariatric surgery cohort only)
• History of laparoscopic gastric band with active band titration (any adjustments occurring or planned within 1 year of the start or end of the study period)
• Uncontrollable coagulopathy
• Severe or uncontrolled psychiatric disorder (including active psychosis or bipolar disorder with an active manic episode), as determined during standard pre-surgery psychiatric screening or clinical assessment
• Suicidal ideation, or unstable or untreated major depressive disorder within the past 12 months
• Active alcohol or substance use disorder within the past 12 months
• Pregnant, breastfeeding, or planning pregnancy within the study follow-up period (24 months from enrollment)
• Active diagnosed eating disorder (not in remission for more than 1 year)
• Diminished capacity to provide informed consent or to follow pre- and post-treatment instructions, as determined by the clinical team
• Current use of another wearable health monitoring device (such as Apple Watch, Fitbit, or Garmin) that the participant is unwilling to stop using for the study duration
• Prior use of incretin-based therapy within the past 6 months (GLP-1 initiation cohort only)
• Any history or current health condition that, in the PI's opinion, would make the participant ineligible or would substantially compromise the quality or interpretability of wearable-derived data