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Obese Patients With Bariatric SurgeryNCT06963437

Interventions for Weight Regain After Bariatric Surgery

A study testing Diet, Ketogenic diet and Fasting in people with Obese Patients With Bariatric Surgery and Obese Patients (BMI ≥ 30 kg/m²), run by Medipol University at 2 sites in Turkey (Türkiye).

Completed

Finished. The study has ended and is not enrolling. Results may be posted on the official record.

Official record
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Trial 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… Read more about this study

Who is it for?
Ages 18 to 45 years
What is being tested?
Diet, Ketogenic diet and Fasting
Could I receive a placebo?
No, everyone receives an active treatment
How many people
43 participants
Where
2 sitesTurkey (Türkiye)
Study dates
12 May 2025to 10 Jul 2025
Phase
Interventional
Are there results?
None posted in the registry

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

  • Ages 18 to 45 years
  • All sexes
  • No healthy volunteers
  • Adult

Who may be able to join

  • 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).
  • -

Who cannot join

  • 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.

Trial locations and contacts

2 sites in 1 country.

Turkey (Türkiye)2 sites

  • Özel Nev FSM Hastanesi

    Bursa, Bursa, 16160

  • Özel Nev FSM Hastanesi

    Nilufer, Bursa, 16160

Other trials in Turkey (Türkiye)

About this study

Official title: Comparison of Revisional Surgery, Ketogenic Diet, and Intermittent Fasting in Bariatric Surgery Patients With Weight Regain: A Prospective Randomized Controlled Study

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.

Read the 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.
Being tested
Diet, Ketogenic diet, Fasting, Control
Keywords
weight regain post bariatric surgery, revisional bariatric surgery, ketogenic dieting, intermittent fasting, nutritional status
Medical subject headings
Intermittent Fasting

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

  • DietOther

    Also called bariatric 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

  • Ketogenic dietOther

    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.

  • FastingOther

    Also called intermittent 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

  • ControlOther

    Also called Control Group

    No individualized diet will be planned

Study groups in NCT06963437
Study groupRoleWhat they receive
Revisional bariatric surgery (RBS) groupExperimentalA nutrition program in accordance with ASMBS guidelines will be implemented for patients undergoing revisional bariatric surgery.
Receives: Other: Diet
Very low-calorie ketogenic diet (VLCKD) groupExperimentalThe 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.
Receives: Other: Ketogenic diet
Intermittent fasting (IF) groupExperimentalTime-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.
Receives: Other: Fasting
Control groupActive comparatorNo individualized diet will be planned; instead, patients will receive education on the stage 4 dietary guidelines recommended for lifelong adherence following bariatric surgery.
Receives: Other: Control

What is being measured

The primary outcome is the main question the study is designed to answer.

  1. 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.

    Measured: Baseline and Week 6

  2. 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.

    Measured: Baseline and Week 6

  3. 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.

    Measured: Baseline and Week 6

  4. 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.

    Measured: Baseline and Week 6

  5. Percentage Weight Loss (%WL)

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

    Measured: Baseline and Week 6

  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.*

    Measured: Baseline and Week 6

Secondary outcomes (9)

  1. Change in Fasting Blood Glucose (mg/dL)

    Fasting venous blood samples will be collected after an overnight fast of at least 8 hours, both at baseline and at Week 6. Fasting blood glucose will be measured using standardized automated analyzers in a certified clinical laboratory.

    Descriptive statistics will be reported as mean ± SD or median (min-max). Group comparisons will be made using ANOVA or Kruskal-Wallis, with significance set at p<0.05.

    Measured: Baseline and Week 6

  2. Change in Fasting Insulin (µIU/mL)

    Serum insulin concentrations will be determined from fasting blood samples taken at baseline and Week 6 using standardized laboratory methods.

    Descriptive statistics will be reported as mean ± SD or median (min-max). Group comparisons will be made using ANOVA or Kruskal-Wallis, with significance set at p<0.05.

    Measured: Baseline and Week 6

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

    Lipid levels will be assessed from fasting blood samples. The lipid profile includes high- density lipoprotein (HDL), low-density lipoprotein (LDL), total cholesterol, and triglycerides.

    Descriptive statistics will be reported as mean ± SD or median (min-max). Group comparisons will be made using ANOVA or Kruskal-Wallis, with significance set at p<0.05.

    Measured: Baseline and Week 6

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

    Renal function parameters will be analyzed using fasting blood samples to determine changes in blood urea nitrogen (BUN), creatinine, uric acid, and urea levels.

    Descriptive statistics will be reported as mean ± SD or median (min-max). Group comparisons will be made using ANOVA or Kruskal-Wallis, with significance set at p<0.05.

    Measured: Baseline and Week 6

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

    Liver function will be assessed by measuring serum levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), albumin, and total protein.

    Descriptive statistics will be reported as mean ± SD or median (min-max). Group comparisons will be made using ANOVA or Kruskal-Wallis, with significance set at p<0.05.

    Measured: Baseline and Week 6

  6. Change in Vitamin and Mineral Status (Vitamin B12, Folic Acid, Magnesium, Calcium, Sodium, Potassium) (ng/L, mg/dL, mmol/L, etc.)

    Serum concentrations of vitamins and minerals will be measured from fasting samples. Parameters include vitamin B12, folic acid, magnesium, total calcium, sodium, and potassium.

    Descriptive statistics will be reported as mean ± SD or median (min-max). Group comparisons will be made using ANOVA or Kruskal-Wallis, with significance set at p<0.05.

    Measured: Baseline and Week 6

  7. Change in Hematological Parameters (Hemoglobin, Hematocrit, Ferritin, Serum Iron, TIBC) (g/dL, µg/L, etc.)

    Hematological status will be evaluated using fasting blood samples to assess hemoglobin, hematocrit, ferritin, serum iron, and total iron binding capacity (TIBC).Descriptive statistics will be reported as mean ± SD or median (min-max). Group comparisons will be made using ANOVA or Kruskal-Wallis, with significance set at p<0.05.

    Measured: Baseline and Week 6

  8. Change in Daily Energy and Macronutrient Intake

    Daily intake of energy (kcal/day) and macronutrients-protein, fat, carbohydrate, and fiber (g/day)-will be assessed using 3-day dietary records (including one weekend day) and a validated Food Frequency Questionnaire (FFQ). Data will be analyzed using BEBIS-9 (Nutrition Information System, Turkey). Dietary records will be reviewed for completeness and accuracy by trained dietitians. Results will be reported in kcal/day and g/day.

    Descriptive statistics will be reported as mean ± SD or median (min-max). Group comparisons will be made using ANOVA or Kruskal-Wallis, with significance set at p<0.05.

    Measured: Baseline and Week 6

  9. Change in Micronutrient Intake

    Micronutrient intake (e.g., vitamins and minerals) will be assessed using 3-day dietary records and the FFQ. Data will be analyzed using BEBIS-9, with results reported in standard units (e.g., mg/day, µg/day). Intake values will be interpreted in relation to dietary reference values but without applying a composite scoring scale.

    Descriptive statistics will be reported as mean ± SD or median (min-max). Group comparisons will be made using ANOVA or Kruskal-Wallis, with significance set at p<0.05.

    Measured: Baseline and Week 6

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

  1. First posted9 May 2025
  2. Study start12 May 2025
  3. Primary completion10 Jul 2025
  4. Study completion10 Jul 2025

Resources

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design
Study type
Interventional
Phase
Phase N/A
Primary purpose
Treatment
Allocation
Randomised
Intervention model
Parallel groups
Model description
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
Masking
None (open label)
Enrolment
43 participants (actual)
IDs, dates and publications
ClinicalTrials.gov ID
NCT06963437
Sponsor's protocol ID
MEDU-SBE-SS-01
Status last verified
Jul 2025
First submitted
18 Apr 2025
Last updated
1 Aug 2025
Results posted
No
Data monitoring committee
No
FDA-regulated drug
No
FDA-regulated device
No
Individual data sharing
No: Due to ethical and privacy considerations, individual participant data will not be shared

Questions about this trial

What is this clinical trial studying?

A study testing Diet, Ketogenic diet and Fasting in people with Obese Patients With Bariatric Surgery and Obese Patients (BMI ≥ 30 kg/m²), run by Medipol University at 2 sites in Turkey (Türkiye).

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 5 inclusion and 4 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: finished, as of the sponsor's last update on 1 Aug 2025. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 2 sites in Turkey (Türkiye). Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

Are results available for this study?

The study is completed, but results are not available in the source record. That does not mean the treatment did or did not work.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Change in Body Weight (kg) (time frame: Baseline and Week 6). The study lists 6 primary outcomes in all. It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT06963437.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 1 Aug 2025.

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