Interventions for Weight Regain After Bariatric Surgery

NCT ID: NCT06963437

Last Updated: 2025-08-01

Basic Information

• Recruitment Status: COMPLETED
• Clinical Phase: NA
• Total Enrollment: 43 participants
• Study Classification: INTERVENTIONAL
• Study Start Date: 2025-05-12
• Study Completion Date: 2025-07-10

Brief Summary

Study Objective:

The aim of this study is to evaluate the effects of revisional bariatric surgery (RBS), very low-calorie ketogenic diet (VLCKD), and intermittent fasting (IF) on nutritional habits and clinical outcomes (anthropometric and biochemical measurements) in patients with insufficient weight loss (IWL) or weight regain (WR) after bariatric surgery, and to compare these findings with those of a control group.

Detailed Description

Study Hypotheses:

1. In patients with IWL or WR after bariatric surgery, a diet following the bariatric care guidelines (BCGs) after revisional bariatric surgery (RBS) improves nutritional habits, anthropometric, and biochemical parameters.

2. In patients with IWL or WR after bariatric surgery, VLCKD improves nutritional habits, anthropometric, and biochemical parameters.

3. In patients with IWL or WR after bariatric surgery, IF regimen improves nutritional habits, anthropometric, and biochemical parameters.

4. In patients with IWL or WR after bariatric surgery, the diet program recommended by the ASMBS as part of standard post-bariatric care improves nutritional habits, anthropometric measurements, and biochemical parameters.

Conditions

Obese Patients With Bariatric Surgery; Obese Patients (BMI ≥ 30 kg/m²); Weight Regain Post Bariatric Surgery; Revisional Bariatric Surgery; Ketogenic Dieting; Intermittent Fasting

Study Design

• Allocation Method: RANDOMIZED
• Intervention Model: PARALLEL
• Primary Study Purpose: TREATMENT
• Blinding Strategy: NONE

Study Groups

Revisional bariatric surgery (RBS) group

A nutrition program in accordance with ASMBS guidelines will be implemented for patients undergoing revisional bariatric surgery.

Group Type: EXPERIMENTAL

Diet

Intervention Type: OTHER

A four-stage dietary program will be implemented in accordance with ASMBS guidelines. To the best of our knowledge, there is currently no study comparing the dietary approach following revisional bariatric surgery with ketogenic and intermittent fasting diets

Very low-calorie ketogenic diet (VLCKD) group

The daily energy intake of VLCKD will be planned as 600-800 kcal, with approximately 10% of energy from carbohydrates (\<30 g/day), 40-45% from protein, and 40-50% from fat.

Group Type: EXPERIMENTAL

Ketogenic diet

Intervention Type: OTHER

A high-protein Very Low-Calorie Ketogenic Diet (VLCKD) will be implemented as the nutritional intervention. In line with previous studies, the daily energy intake of the ketogenic diet will be planned as 600-800 kcal, with approximately 10% of energy from carbohydrates (\<30 g/day), 40-45% from protein, and 40-50% from fat. Total carbohydrate intake will be restricted to less than 30 g per day, primarily from vegetables, while fat intake will derive from natural protein sources and 10 g of olive oil per day.

Intermittent fasting (IF) group

Time-restricted intermittent fasting (16/8) will be applied. Patients in this group will follow a feeding schedule limited to an 8-hour window (16/8) for a duration of 6 weeks.

Group Type: EXPERIMENTAL

Fasting

Intervention Type: OTHER

Patients in this group will follow a time-restricted eating pattern (16/8) for a duration of 6 weeks, with food intake limited to an 8-hour window each day. Intermittent fasting will preferably be observed between 6:00 PM and 10:00 AM; however, patients may choose alternative 16-hour fasting periods such as 7:00 PM-11:00 AM or 8:00 PM-12:00 PM, depending on their individual routines. During the 8-hour feeding window, patients will adhere to the stage 4 post-bariatric dietary guidelines in accordance with ASMBS recommendations

Control group

No individualized diet will be planned; instead, patients will receive education on the stage 4 dietary guidelines recommended for lifelong adherence following bariatric surgery.

Group Type: ACTIVE_COMPARATOR

Control

Intervention Type: OTHER

No individualized diet will be planned

Interventions

Diet

A four-stage dietary program will be implemented in accordance with ASMBS guidelines. To the best of our knowledge, there is currently no study comparing the dietary approach following revisional bariatric surgery with ketogenic and intermittent fasting diets

Intervention Type: OTHER

Ketogenic diet

A high-protein Very Low-Calorie Ketogenic Diet (VLCKD) will be implemented as the nutritional intervention. In line with previous studies, the daily energy intake of the ketogenic diet will be planned as 600-800 kcal, with approximately 10% of energy from carbohydrates (\<30 g/day), 40-45% from protein, and 40-50% from fat. Total carbohydrate intake will be restricted to less than 30 g per day, primarily from vegetables, while fat intake will derive from natural protein sources and 10 g of olive oil per day.

Intervention Type: OTHER

Fasting

Patients in this group will follow a time-restricted eating pattern (16/8) for a duration of 6 weeks, with food intake limited to an 8-hour window each day. Intermittent fasting will preferably be observed between 6:00 PM and 10:00 AM; however, patients may choose alternative 16-hour fasting periods such as 7:00 PM-11:00 AM or 8:00 PM-12:00 PM, depending on their individual routines. During the 8-hour feeding window, patients will adhere to the stage 4 post-bariatric dietary guidelines in accordance with ASMBS recommendations

Intervention Type: OTHER

Control

No individualized diet will be planned

Intervention Type: OTHER

Other Intervention Names

bariatric diet; intermittent fasting; Control Group

Eligibility Criteria

Inclusion Criteria

• Patients aged between 18 and 45 years who have undergone bariatric surgery (BS).
• Experiencing inadequate weight loss (IWL) within 18 months after surgery or weight regain (WR) following successful weight loss.
• Definitions used in the study:

IWL is defined as <50% excess weight loss (EWL) 18 months postoperatively. WR is defined as >25% regain of the lost weight (from the lowest achieved weight).

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Exclusion Criteria

• Pregnant or lactating women.
• Patients with acute illnesses, infections, or comorbidities that may affect treatment efficacy or safety (e.g., cancer, type 1 diabetes, renal or hepatic failure, recent stroke or myocardial infarction, nephrolithiasis, substance or alcohol abuse, eating disorders, severe depression or other psychiatric disorders, inflammatory bowel disease, neoplasms, arrhythmic heart diseases, heart failure, respiratory failure).
• Patients currently receiving corticosteroid therapy.
• Professional athletes.

• Minimum Eligible Age: 18 Years
• Maximum Eligible Age: 45 Years
• Eligible Sex: ALL
• Accepts Healthy Volunteers: No

Sponsors

Medipol University

OTHER

Sponsor Role: lead

Responsible Party

Seher Dallı Şen

Seher Dallı Şen, PhD Candidate in Nutrition and Dietetic

Responsibility Role: PRINCIPAL_INVESTIGATOR

Locations

Özel Nev FSM Hastanesi

Bursa, Bursa, Turkey (Türkiye)

Özel Nev FSM Hastanesi

Nilufer, Bursa, Turkey (Türkiye)

Countries

Turkey (Türkiye)

Other Identifiers

MEDU-SBE-SS-01

Identifier Type: -

Identifier Source: org_study_id