Bariatric Surgery and Gut Microbiota Changes Over Time

Is this trial a fit for you?

A plain-English reading of the study's rules. Only the study team can confirm whether you qualify.

What this trial studies

This prospective observational study will follow adults aged 18 to 65 who are undergoing Roux-en-Y gastric bypass, along with a control group of adults with obesity managed by diet and a healthy normal-weight group. Researchers will collect stool samples and blood at multiple time points over 12 months to analyze gut microbiota composition and fecal metabolome, and relate these findings to weight loss and metabolic outcomes. The goal is to understand the timing, persistence, and clinical relevance of microbial and metabolic changes after bariatric surgery compared with weight-loss by diet alone and with normal weight. The study does not involve an intervention beyond standard clinical care and data collection, and eligibility is limited to specified BMI ranges and health statuses. Interventions are not specified beyond observational data collection.

Why it matters

Who can join: the full rules

Inclusion Criteria (RYGB Group):

* Age between 18 and 65 years.
* Adults with a body mass index (BMI) ≥ 35 kg/m² with related comorbidities, or BMI ≥ 40 kg/m², who are candidates for Roux-en-Y gastric bypass (RYGB) surgery only.

Exclusion Criteria (RYGB Group):

* Treatment with antibiotics within the last 3 weeks, or probiotics/prebiotics within the last 4-6 weeks, or systemic corticosteroids within the 8 weeks prior to baseline (T0).
* Participation in dietary regimens or calorie restriction programs in the weeks prior to enrollment.
* Chronic inflammatory bowel diseases (e.g., Crohn's disease, ulcerative colitis), ongoing enteric infections, or active neoplasms.
* Previous organ transplant or ongoing systemic immunosuppressive therapy.
* Pregnancy or breastfeeding.
* Previous major gastrointestinal surgery.
* Chronic alcohol consumption above moderate levels or substance use disorder.

Inclusion Criteria (Obese Control Group):

* Age between 18 and 65 years.
* Adults with BMI ≥ 30 kg/m² who are candidates for structured dietary treatment.

Inclusion Criteria (Healthy Control Group):

* Age between 18 and 65 years.
* Normal weight (BMI between 18.5 and 24.9 kg/m²).
* Normal metabolic function: fasting glucose below threshold, normal ALT/AST, no diagnosis of diabetes or metabolic syndrome.
* No chronic gastrointestinal diseases or conditions that could alter the gut microbiota.

Exclusion Criteria (Obese Control and Healthy Control Group):

* Use of antibiotics within the last 3 weeks or probiotics/prebiotics within the last 4-6 weeks.
* Recent gastrointestinal surgery.
* Pregnancy or breastfeeding.
* Extreme diets or recent dietary changes.
* Recent international travel that could have affected the gut microbiota.
* Medications known to influence the gut microbiota (e.g., PPIs, metformin, steroids).
* Active smoking or excessive alcohol consumption.
* Significant gastrointestinal symptoms (chronic diarrhea or constipation).

Where it's running

• Azienda Ospedaliera Specializzata in Gastroenterologia Saverio de Bellis
  Castellana Grotte, Ba, Italy Recruiting

Study contacts

• Study coordinator: Domenica Mallardi, Biologist
• Email: domenica.mallardi@irccsdebellis.it
• Phone: +390804994129

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How to take part

1. Review the eligibility criteria above with your treating physician.
2. Check the official listing on ClinicalTrials.gov for the latest contact details and recruitment status.
3. Contact the study coordinator or principal investigator to ask for pre-screening. Pre-screening is free and never obligates you to enroll.