How body fat and muscle change with GLP‑1 weight-loss medicines versus gastric bypass
Conduct of the REsponses in Function and Outcomes From RYGB vs. Medication Study (REFORM) Study by Research Coordinators
This project sees if GLP‑1 weight-loss medicines (like semaglutide or tirzepatide) or gastric bypass affect muscle, fat, metabolism, and side effects differently in adults with severe obesity.
Quick facts
| Study type | Observational |
|---|---|
| Enrollment | 60 (estimated) |
| Ages | 21 Years to 65 Years |
| Sex | All |
| Sponsor | Vanderbilt University Medical Center Academic / other |
| Locations | 1 site (Nashville, Tennessee) |
| Trial ID | NCT07115069 on ClinicalTrials.gov |
What this trial studies
This observational study follows adults with severe obesity who plan to start a GLP‑1 receptor agonist (semaglutide or tirzepatide) or undergo primary gastric bypass. Participants will have whole-body DXA scans at baseline and at 3, 6, and 12 months to measure changes in fat and lean mass, and will complete surveys about symptoms and side effects. Investigators will compare patterns of muscle loss, metabolic changes, and reported gastrointestinal or other adverse effects between the medication and surgery groups. The aim is to clarify differences in body composition and tolerability that could inform treatment choices.
Who should consider this trial
Good fit: Adults with BMI 35–60 planning primary gastric bypass or starting semaglutide or tirzepatide, without the listed exclusion conditions, are the intended participants.
Not a fit: People with revisional bariatric surgery, type 1 diabetes, recent myocardial infarction or unstable cardiac disease, uncontrolled hypertension, low kidney function (eGFR <60), recent systemic steroid use, or less than three months of GLP‑1 use are excluded and unlikely to benefit from joining.
Why it matters
Potential benefit: Results could help patients and clinicians choose the treatment that best preserves muscle, improves metabolism, and minimizes side effects.
How similar studies have performed: Large randomized trials have shown strong weight loss with GLP‑1 receptor agonists and durable benefits from gastric bypass, but direct head‑to‑head comparisons of their effects on muscle mass and side effects are limited.
Eligibility criteria
Show full inclusion / exclusion criteria
Inclusion Criteria: * BMI ≥35 and ≤60 * Primary weight loss surgery (gastric bypass), or * Medical weight loss with GLP1RAs (Semaglutide or Tirzepatide) Exclusion Criteria: * Revisional gastric bypass (e.g. sleeve to bypass), * \<3 months of continuous use of GLP1RA, * Type 1 Diabetes, * Myocardial Infarction, * Unstable Angina or Heart Failure, * Stroke * Solid organ transplantation, * Systemic glucocorticoid prior 28 days, * Uncontrolled Hypertension, (Systolic \> 150, Diastolic \> 90) * Untreated Hyperthyroidism * Chronic Kidney Disease (EGFR \< 60).
Where this trial is running
Nashville, Tennessee
- Vanderbilt University Medical Center — Nashville, Tennessee, United States (Recruiting)
Study contacts
- Principal investigator: Jason M Samuels, MD — Vanderbilt University Medical Center
- Study coordinator: Jason M Samuels, MD
- Email: jason.m.samuels@vumc.org
- Phone: 2142891373
How to participate
- Review the eligibility criteria above with your treating physician.
- Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
- Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.