Impact of a Pro-diversity Gut Microbiota Diet After a Bariatric Surgery on Gut Microbiota, Eating Behaviour and Sensory Function

NCT07268508 | Not Yet Recruiting

• 1 other identifier: 69HCL24_0033
• Study Type: interventional
• Target: 60
• Locations: 1 country
• Sites: 3

Brief Summary

Bariatric surgery is the most effective treatment for long-term weight loss and reducing obesity-related health risks. It alters the gastrointestinal tract as well as metabolic and hormonal functions, influencing eating behaviour. However, weight loss outcomes and long-term maintenance vary between patients, likely due to changes in the gut microbiota. Dietary recommendations aimed at improving microbiota diversity could help support sustained weight loss after surgery. The BariaGut Taste study aims to compare two dietary approaches following bariatric surgery: nutritional counselling promoting gut microbiota diversity versus standard nutritional counselling. One year after surgery, the study will evaluate differences in microbiota diversity, changes in food preferences and eating behaviours, sensory profiles (taste, smell), levels of digestive and gut hormones fasting, before and after eating, cardiometabolic parameters, mental health, physical activity, and more, to better understand Bariatric surgery is the most effective treatment for long-term weight loss and reducing obesity-related health risks. It alters the gastrointestinal tract as well as metabolic and hormonal functions, influencing eating behaviour. However, weight loss outcomes and long-term maintenance vary between patients, likely due to changes in the gut microbiota. Dietary recommendations aimed at improving microbiota diversity could help support sustained weight loss after surgery. The BariaGut Taste study aims to compare two dietary approaches following bariatric surgery: nutritional counselling promoting gut microbiota diversity versus standard nutritional counselling. One year after surgery, the study will evaluate differences in microbiota diversity, changes in food preferences and eating behaviours, sensory profiles (taste, smell), levels of digestive and gut hormones fasting, before and after eating, cardiometabolic parameters, mental health, physical activity, and more, to better understand the mechanisms that may explain variations in response to bariatric surgery. The BariaGut Taste study is a prospective, randomized, controlled trial with two parallel groups, involving non-diabetic patients aged 25 to 65 y undergoing either sleeve gastrectomy or Roux-en-Y gastric bypass. The trial will be conducted at the digestive surgery department of Edouard Herriot Hospital, the endocrinology-diabetes-nutrition department of Lyon Sud Hospital Center, and the Human Nutrition Research Center Rhône-Alpes. 60 participants are expected to be recruited, with 30 in each arm. Participants will be enrolled before surgery during a routine care visit with the surgeon. They will then undergo a metabolic assessment visit conducted exclusively for research purposes. This visit will allow to collect baseline data on primary outcomes via blood, expired air, and stool samples, anthropometric measurements, indirect calorimetry, a battery of questionnaires (TFEQ-21, DEBQ, PHQ-9, SF36, GSES, PANAS, ESUL, BES, DERS, GAD-7, IPAQ, BAQ, GSRS, sensory alterations, Bristol and Likert scales, and FNS), computerized food preference tests (LFPQ), and a standardized, video-recorded ad libitum buffet. Participants will be followed up at 3, 6, and 12 months after surgery through visits combining clinical care and research assessments. The dietary interventions specific to each group will be provided since the 3-month visit. The assessments conducted before surgery will be repeated at 6 and 12 months, also integrating clinical care objectives. Additional blood, stool, and adipose tissue samples collected during surgery will be stored to create a biobank.

Conditions

Obesity (Disorder); Bariatric Surgery

Keywords

Bariatric surgery; gut microbiota; sensory alteration; food preferences; weight loss maintenance

Outcome Measures

Primary Outcomes (1)

• Microbiota diversity 12 months after surgery

  The change in the diversity of the microbiota (shot gun metagenomic analysis, counting the number of microbial genes), between before surgery and one year after surgery (delta) between the two dietary intervention groups.

  Primary outcome will be assessed three times : before the surgery, 6 and 12 months after

Secondary Outcomes (99)

• Eating behaviour during a standardised, filmed and validated ad libitum buffet : Food intake

  Before the surgery and at 6 and 12 month after

• Eating behaviour during a standardised, filmed and validated ad libitum buffet: Nutritional quality

  Before the surgery and at 6 and 12 month after

• Eating behaviour during a standardised, filmed and validated ad libitum buffet: Meal microstructure

  Before the surgery and at 6 and 12 month after

• Eating behaviour during a standardised, filmed and validated ad libitum buffet: Meal appreciation

  Before the surgery and at 6 and 12 month after

• Eating behaviour and preferences : Behaviors

  Before the surgery and at 6 and 12 month after

Study Arms (2)

Participants with nutritional counselling promoting gut microbiota diversity

EXPERIMENTAL

Given the low amounts of food consumed during the first months after surgery, the specific nutritional recommendations for this group will be implemented starting 3 months post-surgery. Before 3 months, participants will receive the standard nutritional recommendations of routine care after bariatric surgery, identical to those given to the second group (see below). From 3 months onwards, participants will be encouraged to increase the consumption of certain specific foods known for their benefits on the gut microbiota, particularly for promoting gut bacterial diversity, in addition to maintaining protein intake and paying attention to food textures. Summary sheets will be provided to help recall the recommendations.

Other: Nutritional counseling

Participants with standard nutritional counselling

NO INTERVENTION

The nutritional recommendations given to participants in this group are those applied in routine care within the Endocrinology, Diabetes, and Nutrition (EDN) Department for patients who have undergone sleeve gastrectomy or gastric bypass (Roux-en-Y). These recommendations aim to maintain adequate protein intake and are adapted to the recent changes in their digestive tract (pureed then mashed food during the first postoperative month). During the first 6 months, patients' food intake is significantly below their nutritional needs. So it is important to pay close attention to hydration (away from meals) and macronutrient intake, especially proteins, as well as the progression of food texture and chewing.

Interventions

Nutritional counseling OTHER

Nutritional counseling

Participants with nutritional counselling promoting gut microbiota diversity

Eligibility Criteria

• Age: 25 Years - 65 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Between 25 and 65 years old
• Undergoing either sleeve gastrectomy or Roux-en-Y gastric bypass
• With grade 3 obesity (BMI≥40 kg/m²) or with BMI≥35 kg/m² and at least one comorbidity likely to be improved after surgery, with the exception of type 2 diabetes
• Signed consent form
• Living less than an hour and 30 minutes from the hospital
• Presence of effective and stable contraception for women of childbearing potential

You may not qualify if:

• Type 2 diabetes
• Presence of a contraindication to bariatric surgery
• Presence of gastrointestinal pathologies with an inflammatory component, known gastroparesis, total gastrectomy, colectomy, exocrine pancreatic insufficiency, known endocrine pathologies inducing hyperglycaemia (uncontrolled dysthyroidism, acromegaly, hypercorticism, etc.), severe chronic renal insufficiency (\< 30mL/min), or hepatocellular insufficiency
• Claustrophobic
• Pregnant or breastfeeding women
• Taking an obesity treatment 3 months before surgery
• Daily taking of laxatives or drugs that can strongly interfere with the composition of the intestinal microbiota. If taken sporadically, the patient can be included at a distance (3 weeks) from the laxatives taken.
• Specific diets (vegetarian, vegan or without gluten)
• No French speaker
• Already included in other study
• Donated blood in the last two months
• Without freezer access
• With allergy or intolerance to food propose in ad libitum buffet

Sponsors & Collaborators

• Hospices Civils de Lyon: lead

Study Sites (3)

Hospital Edouard Herriot, digestive surgery department

Lyon, 69310, France

Location

Centre de recherche en nutrition humaine de Rhône-Alpes

Pierre-Bénite, 69310, France

Location

Hôpital Lyon sud, Endocrinology Diabetes Nutrition department

Pierre-Bénite, 69310, France

Location

MeSH Terms

Conditions

Obesity; Food Preferences

Interventions

Nutrition Assessment

Condition Hierarchy (Ancestors)

Overweight; Overnutrition; Nutrition Disorders; Nutritional and Metabolic Diseases; Body Weight; Signs and Symptoms; Pathological Conditions, Signs and Symptoms; Feeding Behavior; Behavior

Intervention Hierarchy (Ancestors)

Data Collection; Epidemiologic Methods; Investigative Techniques; Health Care Evaluation Mechanisms; Quality of Health Care; Health Care Quality, Access, and Evaluation; Epidemiologic Measurements; Public Health; Environment and Public Health

Central Study Contacts

Julie-Anne NAZARE

CONTACT

+33 6 88 87 09 62; julie-anne.nazare@univ-lyon1.fr

Berenice SEGRESTIN

CONTACT

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: SINGLE
• Who Masked: PARTICIPANT
• Masking Details: Randomisation will be stratified according to sex, type of surgery and age.
• Purpose: PREVENTION
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: SPONSOR

Model Details: * Arm with nutritional counselling promoting gut microbiota diversity * Arm with standard nutritional counselling

Study Record Dates

• First Submitted: August 14, 2025
• First Posted: December 5, 2025
• Study Start: December 1, 2025
• Primary Completion (Estimated): January 1, 2029
• Study Completion (Estimated): January 1, 2029
• Last Updated: December 5, 2025

Record last verified: 2025-11

Locations

FR (3)