Interventions for Weight Regain After Bariatric Surgery

NCT06963437 | Completed

• 1 other identifier: MEDU-SBE-SS-01
• Study Type: interventional
• Target: 43
• Locations: 1 country
• Sites: 2

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.

Conditions

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

Keywords

weight regain post bariatric surgery; revisional bariatric surgery; ketogenic dieting; intermittent fasting; nutritional status

Outcome Measures

Primary Outcomes (6)

• Change in Body Weight (kg)

  Body weight will be measured at baseline and at Week 6 using a calibrated digital scale while participants are wearing light clothing and no shoes. Statistical analyses will be performed using SPSS v22.0. Normality will be tested using Shapiro-Wilk. ANOVA or Kruskal-Wallis will be used as appropriate; p\<0.05 considered significant.

  Baseline and Week 6

• Change in Body Mass Index (kg/m²)

  BMI will be calculated as weight (kg) divided by the square of height (m²), using body weight and height measurements obtained with a digital scale and a wall-mounted stadiometer. Statistical analyses will be performed using SPSS v22.0. Normality will be tested using Shapiro-Wilk. ANOVA or Kruskal-Wallis will be used as appropriate; p\<0.05 considered significant.

  Baseline and Week 6

• Change in Waist Circumference (cm)

  Waist circumference will be measured using a non-elastic measuring tape while participants are standing upright. The measurement will be taken 5 cm below the umbilicus. Statistical analyses will be performed using SPSS v22.0. Normality will be tested using Shapiro-Wilk. ANOVA or Kruskal-Wallis will be used as appropriate; p\<0.05 considered significant.

  Baseline and Week 6

• Change in Body Composition (Fat Mass %, Muscle Mass %,) assessed by BIA

  Body composition parameters, including fat mass (%), fat-free mass (%), muscle mass (%), and ECW/TBW ratio, will be assessed using multi-frequency segmental bioelectrical impedance analysis (BIA) (Tanita MC-780 MA, Korea). Assessments will follow ESPEN guidelines. Statistical analyses will be performed using SPSS v22.0. Normality will be tested using Shapiro-Wilk. ANOVA or Kruskal-Wallis will be used as appropriate; p\<0.05 considered significant.

  Baseline and Week 6

• Percentage Weight Loss (%WL)

  %WL will be calculated using the formula: \[(Preoperative weight - Postoperative weight) / Preoperative weight\] × 100

  Baseline and Week 6

• Percentage Excess Weight Loss (%EWL)

  %EWL will be calculated using the formula: \[(Preoperative weight - Postoperative weight) / (Preoperative weight - Ideal weight)\] ×100 \*Ideal weight is defined as the weight corresponding to a BMI of 25 kg/m².\*

  Baseline and Week 6

Secondary Outcomes (9)

• Change in Fasting Blood Glucose (mg/dL)

  Baseline and Week 6

• Change in Fasting Insulin (µIU/mL)

  Baseline and Week 6

• Change in Lipid Profile (HDL, LDL, Total Cholesterol, Triglycerides) (mg/dL)

  Baseline and Week 6

• Change in Renal Function Markers (BUN, Creatinine, Uric Acid, Urea) (mg/dL)

  Baseline and Week 6

• Change in Liver Function Tests (ALT, AST, Albumin, Total Protein) (U/L, g/dL)

  Baseline and Week 6

Study Arms (4)

Revisional bariatric surgery (RBS) group

EXPERIMENTAL

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

Other: Diet

Very low-calorie ketogenic diet (VLCKD) group

EXPERIMENTAL

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.

Other: Ketogenic diet

Intermittent fasting (IF) group

EXPERIMENTAL

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.

Other: Fasting

Control group

ACTIVE COMPARATOR

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

Other: Control

Interventions

Diet 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

Also known as: bariatric diet

Revisional bariatric surgery (RBS) group

Ketogenic diet 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.

Very low-calorie ketogenic diet (VLCKD) group

Fasting 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

Also known as: intermittent fasting

Intermittent fasting (IF) group

Control OTHER

No individualized diet will be planned

Also known as: Control Group

Control group

Eligibility Criteria

• Age: 18 Years - 45 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64)

You may qualify if:

• 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).

You may not qualify if:

• 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.

Sponsors & Collaborators

• Medipol University: lead

Study Sites (2)

Özel Nev FSM Hastanesi

Bursa, Bursa, 16160, Turkey (Türkiye)

Location

Özel Nev FSM Hastanesi

Nilufer, Bursa, 16160, Turkey (Türkiye)

Location

MeSH Terms

Conditions

Intermittent Fasting

Interventions

Diet; Diet, Ketogenic; Angptl4 protein, mouse; Control Groups

Condition Hierarchy (Ancestors)

Fasting; Feeding Behavior; Behavior

Intervention Hierarchy (Ancestors)

Nutritional Physiological Phenomena; Diet, Food, and Nutrition; Physiological Phenomena; Diet, Carbohydrate-Restricted; Diet Therapy; Nutrition Therapy; Therapeutics; Epidemiologic Research Design; Epidemiologic Methods; Investigative Techniques; Research Design; Methods

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Seher Dallı Şen, PhD Candidate in Nutrition and Dietetic

Model Details: This study will be conducted on 56 patients who have experienced insufficient weight loss (IWL) or weight regain (WR) following bariatric surgery. Participants will be randomly assigned to one of four groups (n=14 per group): RBS Group - patients undergoing revisional bariatric surgery (RBS) VLCKD Group - patients following a very low-calorie ketogenic diet (VLCKD) IF Group - patients following an intermittent fasting (IF) diet Control Group - patients receiving standard post-bariatric nutritional follow-up as recommended by the ASMBS

Study Record Dates

• First Submitted: April 18, 2025
• First Posted: May 9, 2025
• Study Start: May 12, 2025
• Primary Completion: July 10, 2025
• Study Completion: July 10, 2025
• Last Updated: August 1, 2025

Record last verified: 2025-07

Data Sharing

• IPD Sharing: Will not share

Locations

TU (2)